Method and facility for controlled microbiome shift of biomass compaction in biological treatment of untreated influent

Abstract

The invention provides a method for controlled biomass densification in biological treatment of an untreated influent, characterized in that it comprises: a step of subjecting the untreated influent to a biological treatment of free suspended biomass, thereby producing a biomass comprising activated sludge; a step of separating and / or clarifying the activated sludge, thereby producing an effluent and a RAS; a step of extracting at least a part of the RAS and / or a part of the activated sludge as a first source of WAS; a step of subjecting at least a part of the RAS and / or a part of the activated sludge to an external density-based selection, thereby producing an overflow intended to be extracted as a second source of WAS, and an underflow comprising dense biomass aggregates, a step of producing and / or maintaining dense biomass aggregates, such as aerobic granular sludge or biofilm, by a dense biomass aggregate production process, using at least a part of the untreated influent; a step of subjecting the dense biomass aggregates to a biological treatment; a step of subjecting the dense biomass aggregates of the underflow to a biological treatment and / or to the dense biomass aggregate production process; thereby obtaining a densified biomass.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and more specifically to the activated sludge process. Background Technology

[0002] In wastewater treatment, the "activated sludge" process involves biological purification through the free-floating culture of microorganisms that degrade suspended or dissolved organic matter in the wastewater. Good levels of biodegradation are achieved due to the homogenization of the medium (thus allowing microorganisms to come into contact with pollutants (carbon, nitrogen, and phosphorus)) and aeration. The resulting mixture of microorganisms and other suspended solids in the water is called sludge, which is then separated from the treated effluent in a subsequent dedicated solid-liquid separation step.

[0003] One limiting factor in this type of activated sludge wastewater treatment is the "concentration" of the sludge. In fact, it relates to the potential of the methods used to treat the pollutant load, i.e., to the performance of the biological treatment steps. It also limits the design of subsequent clarification steps and the performance of subsequent sludge treatment.

[0004] Sludge concentration can be measured by its settling ability, usually expressed by the Mohlman index. The Mohlman index, also known as the sludge volume index (SVI), defines the volume of activated sludge settling within half an hour relative to the mass of the dry residue of that sludge. A lower dSVI (for diluted sludge volume index) indicates better settling ability.

[0005] In all conventional activated sludge (CAS) systems, the settling capacity of activated sludge typically depends on the variability of raw water characteristics (flow rate, pollutant load, concentration (raw water dilution), and seasonal temperature patterns), known as “environmental factors,” and the combination of bioreactor design configurations (plug flow reactor, completely mixed reactor, presence of contact zone, presence of anoxic zone, presence of anaerobic zone), known as “biodesign factors.”

[0006] Environmental and biological design factors have a critical impact on the range of expected settling capacity of any activated sludge and have a direct influence on design and operational performance. Therefore, each wastewater treatment plant has its own annual SVI variation range, which can be highly dispersed throughout the year. For example, the bulking period of activated sludge is known to occur during cold, high-dilution seasons, such as late winter / early spring.

[0007] This is certainly detrimental to design and operation, as the expected worst-case settling capacity defines the design, which in turn sets limits for operational performance. Therefore, solutions have been developed in the prior art to attempt to improve the settling capacity of activated sludge.

[0008] The first solution is to use granular activated sludge, as defined by Kreuk et al. (MKde Kreuk, N. Kishida, MCM van Loosdrecht, “Aerobic granular sludge-state of the art.” Water Sci Technol 1 April 2007; 55(8-9):75–81). Granular activated sludge does indeed show better settling ability. However, the process for producing granular sludge is quite variable and unstable.

[0009] Wei et al. (Wei SP, Stensel HD, Nguyen Quoc B, et al. "Flocs in disguise? High granule abundance found in continuous-flow activated sludge treatment plants." Water Res. 2020; 179; 115865) recently published the presence of partial but natural granulation in all CAS (conventional activated sludge) systems, highlighting the correlation between low SVI and higher proportions of partial granulation. Wei et al. noted that certain configurations produced more "small particles" than others, thus extending the definition of particles to <200 μm. In particular, higher proportions of particles were observed in systems including anaerobic selectors and plug flow configurations. However, this study remains imprecise in terms of the annual range of variation. Furthermore, this study did not identify any devices controlling the granulation phenomenon, let alone SVI.

[0010] An alternative lies in the use of external weight selection for sludge, which allows for the concentration of “dense” sludge into the activated sludge process. More specifically, the external selector collects and retains biomass aggregates with a concentration gradient of matrix and electron acceptor that favors particle formation rather than floc and filamentous formation. It further manipulates the biomass waste stream to discard filamentous and flocs in the biomass waste stream. Compared to granular activated sludge and conventional activated sludge, sludge obtained using weight selection (1) does not require the use of external carrier materials to form biomass aggregates; (2) activated sludge flocs tend to agglomerate as they settle (when the liquid-sludge mixture is not aerated or stirred), while particles do not agglomerate and settle as individual units; (3) settles significantly faster than activated sludge flocs; and (4) can be harvested by screening. For example, US 2014 / 0148436 describes an internal bioreactor that combines wastewater and recovered biomass to output a biomass waste stream comprising granular biomass. The collected biomass aggregates are returned to the internal bioreactor for pellet formation. In this literature, densified biomass is defined only by an SVI of less than 100 mL / g.

[0011] However, there remains a need for facilities and methods that allow for better control of sludge settling capacity and minimize its dependence on environmental factors. Such methods should be easily implemented, preferably on a wide range of existing CAS methods. For a given treatment capacity, the facility should offer reduced footprint (and capital expenditure) without compromising treatment quality (water purification level). Summary of the Invention

[0012] This invention therefore provides a method for the controlled conversion of existing activated sludge biomass into a new, densified biomass that exhibits reliable and excellent settling and thickening capabilities, particularly in continuous flow activated sludge processes. This conversion is achieved by combining a process for generating “dense biomass aggregates” with a choice based on external gravity (e.g., disclosed in documents US 2015 / 0376043 A1 and US 2016 / 0137537 A1). Density-based aggregates, or densified biomass aggregates, exhibit increased gravitational density or higher density in terms of diffusion resistance due to their compact structure or size (specified by a higher percentage of dense biomass aggregates larger than 100 μm in the biomass). The result of this densification is a controlled and narrower dSVI operating span, which allows for increased upflow velocities in the clarifier during operation and design.

[0013] As used in this paper, the “microbiome” can be defined as a characteristic community of microorganisms occupying a well-defined habitat with distinct physicochemical properties. The microbiome refers not only to the microorganisms involved but also to their habitat, which leads to the formation of a specific ecological niche (see Whipps J., Lewis K. and Cooke R. (1988) “Mycoparasitism and plant disease control”. In: Burge M (Ed.) Fungi in Biological Control Systems, Manchester University Press, pages 161–187. ISBN 9780719019791).

[0014] Where one does not wish to be bound by theory, the controlled transformation of the microbiome, as disclosed in this invention, is achieved by transforming the microbial aggregates and related structures of biomass aggregates and externally selecting these aggregates. More specifically, the controlled microbiome transformation is achieved through the following methods:

[0015] - Selecting biomass with excellent settling and thickening properties allows for the design and operation of systems at higher total biomass stock.

[0016] - Retaining biomass fractions with high solids residence time (SRT) leads to the accumulation of organisms with bionutrient removal activity (e.g., nitrifying bacteria, anaerobic ammonia oxidizing bacteria, denitrifying methanogenic bacteria, and phosphorus-accumulating organisms), thereby promoting new approaches to the design and operation of efficient reactors.

[0017] Therefore, in a first aspect, the present invention relates to a method for controlled biomass densification in the biological treatment of untreated influent, characterized in that it comprises:

[0018] - The untreated influent is subjected to a biological treatment step of free-suspension biomass to produce biomass containing activated sludge;

[0019] - Steps for separating and / or clarifying activated sludge, resulting in effluent and RAS;

[0020] - The step of extracting at least a portion of RAS and / or a portion of activated sludge as the primary source of waste activated sludge (WAS);

[0021] - A step of selecting at least a portion of the RAS and / or a portion of the activated sludge based on external density, thereby generating an overflow intended to be extracted as a second source of WAS, and an underflow comprising dense biomass aggregates;

[0022] - The step of generating and / or maintaining dense biomass aggregates, such as aerobic granular sludge (AGS) or biofilm, by using at least a portion of the untreated influent through a dense biomass aggregate generation process;

[0023] - Steps for subjecting dense biomass aggregates to biological treatment;

[0024] - Steps to subject the dense biomass aggregates in the underflow to biological treatment and / or the process of generating dense biomass aggregates;

[0025] This results in the formation of dense biomass;

[0026] -Steps for controlling the amount of untreated influent supplied to the dense biomass aggregate generation process and / or controlling the amount of waste activated sludge (WAS) extracted from a first source and / or a second source of waste activated sludge (WAS):

[0027] The above steps are configured to maintain dense biomass, said dense biomass having:

[0028] -35 to 100 ml / g of dSVI, and / or

[0029] - More than 10% of the particles have a particle size of 100 μm to 1000 μm, and / or

[0030] -70% to 95% dSVI30 / dSVI10 ratio.

[0031] In another aspect, the present invention relates to a facility for controlled biomass densification in the biological treatment of untreated influent, said facility comprising:

[0032] - A biological tank containing free-suspension biomass having a first inlet, a second inlet and a first outlet, the biological tank being configured to be supplied at the first inlet with at least a portion of untreated influent and RAS to produce a mixture of treated water and activated sludge recovered at the first outlet.

[0033] - A separation unit having a first inlet, a first outlet and a second outlet, the separation unit being configured to be supplied with activated sludge at the first inlet and to produce effluent recovered at the first outlet and RAS recovered at the second outlet;

[0034] - An extraction device configured to extract at least a portion of RAS and / or a portion of activated sludge as a primary source of WAS;

[0035] - An external gravity-based selector having a first inlet, a first outlet, and a second outlet, the external gravity-based selector being configured to be supplied with at least a portion of RAS and / or a portion of activated sludge at the first inlet, and to generate an overflow intended to be extracted at the first outlet as a second source of WAS and a bottom flow containing dense biomass aggregates to be recovered at the second outlet.

[0036] - A dense biomass aggregate generating and / or maintaining unit having a first inlet, an optional second inlet, an optional third inlet, and a first outlet, the dense biomass aggregate generating and / or maintaining unit pool being configured to be supplied with at least a portion of untreated influent at the first inlet and optionally with underflow at the second inlet, and forming a dense biomass aggregate, such as aerobic granular sludge or biofilm recovered at the first outlet;

[0037] - The biological pool is further configured to supply the generated dense biomass aggregates at the second inlet, and optionally supply at least a portion of the dense biomass aggregates recovered at the selector underflow, thereby obtaining dense biomass;

[0038] - Controllers of the amount of untreated influent supplied to the dense biomass aggregate generation and / or maintenance unit and / or controllers of the amount of waste activated sludge (WAS) extracted from a first source and / or a second source of waste activated sludge (WAS).

[0039] The technical advantages of this invention are:

[0040] - The possibility of designing clarifiers with higher surface overflow ratios (SOR), smaller total depths, and surface mass loads exceeding current recommendations.

[0041] - Allows for increased upflow velocities in clarifiers on existing systems to manage and reduce combined sewage overflows (CSOs) and more easily meet “reference” flow calculation thresholds in a brown zone context, particularly (but not limited to) the performance and compliance aspects defined by the European Directive of 21 July 2015.

[0042] - This allows the clarifier to operate at a lower regenerated activated sludge (RAS) rate, resulting in lower dilution and lower internal hydraulic loading in the treatment reactor.

[0043] - The higher biomass concentration and the decoupling of the SRT of the two biomass fractions allow for a reduction in reactor volume.

[0044] Furthermore, this invention allows for a significant increase in the plant's "reference flow rate" and a reduction in the "number of annual overflows," as defined by the European Wastewater Directive 91 / 271 / CEE.

[0045] Another advantage of this invention is the improved quality of the treated water effluent obtained in the secondary treatment step. This may allow for more efficient and / or more competitive tertiary treatment (affecting total suspended solids (TSS), but also total organic carbon (TOC) and BOD), resulting in more competitive operating expenditures (OPEX) (energy, chemicals, etc.) and capital expenditures (CAPEX).

[0046] The microbiome transformation obtained using the methods and facilities of this invention is supported by sludge retention time (SRT) uncoupling, which allows for two biomass samples with two different sludge ages:

[0047] -Ordinary heterotrophic organisms (OHO) in the form of flocculent biomass experience a low sludge age, which is beneficial to denitrification kinetics;

[0048] - Nitrifying bacteria, anaerobic ammonia-oxidizing bacteria, denitrifying methanogenic bacteria, denitrifying polyphosphate-accumulating bacteria or denitrifying methanophilic bacteria, or optionally any other slow-growing organisms associated with the nitrogen or phosphorus cycle, which are in the form of freely suspended biofilm aggregates that can be maintained in the system due to the long SRT provided by the weight selection of the aggregated biomass portion.

[0049] - Reactions and / or anaerobic, hypoxic and aerobic hydrolysis of organisms (e.g., fermenting bacteria, but also including more advanced ones) or such as those responsible for particle breakage; in the form of freely suspended biofilm aggregates that can be maintained in the system due to the long SRT provided by weight selection of the aggregated biomass portions.

[0050] This decoupling allows for more competitive biological tank designs. In fact, the apparent "aerobic SRT" of the biological system can be designed to be lower than the nitrification flushing threshold used in existing CAS and IFAS (Integrated Fixed Membrane Activated Sludge) design practices. This results in the potential to reduce aeration and anoxic volumes while achieving the same treatment performance. From this perspective, the proposed invention achieves both the transformation of the microbiome into denser microbial clusters or aggregates, supporting the densification of total biomass, and the microbiome transformation of the microbial community, i.e.,, in the case of this invention, the transformation to nitrifying biomass on and within denser biomass aggregates. Attached Figure Description

[0051] The accompanying drawings illustrate various non-limiting, exemplary, and inventive aspects of this specification:

[0052] Figure 1A block diagram schematically illustrating the steps of a method for controlled biomass densification in the biological treatment of untreated influent according to the present invention;

[0053] Figure 2 A block diagram schematically illustrating the steps of a method for controlled biomass densification in the biological treatment of untreated influent according to the present invention;

[0054] Figures 3 to 8 Different embodiments of the facility according to the invention are illustrated schematically;

[0055] Figure 9 This is a conceptual diagram showing the microbiome transformation obtained using the method of this invention, with operational change boundaries corresponding to the comparative CAS method;

[0056] Figure 10 This is a scatter plot showing the results compared to control CAS biomass using the method of this invention. Figure 4 The implementation scheme), using a densified production line to obtain microbiome transformations, as measured in the example implementation scheme;

[0057] Figure 11 It is a scatter plot, which shows the results of using the method of this invention. Figure 4 The implementation scheme) compares the seasonal behavior of densified sludge in a conventional activated sludge densification production line; the results are shown in terms of the percentage of aggregates and dSVI, as measured in the implementation scheme of the example;

[0058] Figure 12 It is a graph illustrating the enhanced oxygen transfer measured as in the embodiments of the example;

[0059] Figure 13 It is a graph illustrating the sludge thickening capacity measured in the embodiments described above; more specifically, Figure 13 The measured thickening profiles of densified sludge and CAS sludge are described using the ATV A131 model and the improved ATV model proposed according to the present invention for the thickening behavior of densified sludge.

[0060] Figure 14 It is a graph illustrating the sludge thickening capacity measured in the embodiments described above; more specifically, Figure 14 The relationship between the measured sludge volume index (SVI) and the associated sludge concentration in the thickening column test is described, indicating that the curve extends beyond the original area of ​​the gray rectangle showing the thickening profile in ATV A131. Detailed Implementation

[0061] As used herein, the term "a" in the context of "a unit" should be understood to include "one" or "several" units, which may be arranged in series or parallel, branch or split configurations. Furthermore, any described series method can be implemented in parallel or in branch or split format, and any described parallel method can be implemented in series or in branch or split format. Moreover, any parallel or series, branch or split method or unit can be implemented as an integrated single method or unit.

[0062] As is known in the art, sludge is a specific type of biomass.

[0063] As used in this article, " Biological treatment "Understood as biological treatment containing activated sludge—especially continuous flow biological treatment—that is, any freely suspended biomass process design and configuration and secondary bioreactor technology, such as MLE (modified Ludzack-Ettigner) process, 2-stage BardenPho process, stepwise feed, oxidation ditch process, sequential anoxic / oxidative, anaerobic-anoxic-oxidative (A2O), anoxic-oxidative (AO), AO-(AO)n, anoxic-oxidative-endogenous, MBR (membrane bioreactor), IFAS (integrated fixed membrane activated sludge), MABR (membrane aerated biofilm reactor), trickling filter, rotating biofilm contactor."

[0064] Untreated inflows (10) may include or consist of at least a portion of internal plant recirculation (68).

[0065] Separation It is a solid-liquid separation, and can be clarification, sedimentation, filtration, or flotation. It advantageously operates in a clarifier, membrane filter, or sedimentation system. The separation unit can also be a filter or flotation unit, such as dissolved air flotation (DAF). Preferably, the separation is clarification.

[0066] As used in this invention, " Dense biomass aggregates "Is understood to include or consist of particles with a size of 100 μm or larger, preferably 200 μm or larger, or a density greater than 1.03 g / cm³." 3 Preferably greater than 1.05 g / cm³ 3 Biomass is composed of aggregates. Typically, aggregates have a particle size of less than 1000 μm, for example, aggregates have a particle size of 200 to 500 μm.

[0067] As used in this article, the term " dense"It is understood in terms of its gravity and diffusion, that is, the size and shape of particles (particulate matter and / or flocs and / or aggregates) can be as important as their weight. In fact, the 'dense' biomass according to the invention is understood as biomass with improved settling ability, which is affected by two dimensions."

[0068] As used in this invention, " Densified biomass "Dense biomass" is understood as a mixture of "dense biomass aggregates" and "flocculated activated sludge biomass," and the mixture is ballasted by appropriately adjusting and controlling the proportion of "dense (aerobic granular) biomass aggregates," thereby imparting the overall "dense sludge" mixture with some very good and controlled settling capacity. Specifically, dense biomass is understood to be biomass exhibiting a settling capacity of 35 to 100 mL / g, preferably 40 to 80 mL / g, more preferably 40 to 70 mL / g. dSVI (diluted SVI) has a mass proportion of 10 to 50% (preferably 20 to 40%) of particles larger than 100 μm (up to 1000 μm; preferably 200 μm to 500 μm) and a settling velocity of 2.0 to 9.0 m / h. It is also characterized by a high mass proportion (50% to 90%) of bioflocs smaller than 100 μm (preferably smaller than 200 μm). This densified sludge may also be characterized by a mass fraction greater than or equal to 8.5 kg MLSS·m -2 ·h -1 The limiting mass flow rate standard (MLSS = Mixed Liquid Suspended Solids). Dense biomass typically exhibits a dSVI30 / dSVI10 ratio of 70% to 95% (as opposed to AGS, which has a ratio of 100%), and a typical dSVI30 / dSVI5 ratio of 55% to 85%.

[0069] (d)SVI is measured according to standard NF EN 14702-1 of July 2006.

[0070] Particle size, which refers to the maximum size of the particles, can be determined through statistical analysis of electron microscope images.

[0071] The mass percentage of bioflocs, expressed as a percentage, is related to size, for example, the percentage of particles smaller than 0.2 mm. This value can be obtained by sieving a biomass sample through sieves with different mesh sizes (e.g., 200 μm / 400 μm / 500 μm / 800 μm / 1 mm / 1.25 mm). The SS (suspended solids) concentration of the resulting filtrate is then measured and correlated with the SS concentration (in percentage) of the original sludge.

[0072] Limiting mass flow rate in kg·m -2 h -1It represents the MLSS settling volume per unit area and time. It measures the sludge flow rate at a given concentration. The limiting mass flow rate is determined by Kynch curves through multiple successive dilutions or concentrations of the raw biomass (sludge).

[0073] As used in this article, " Selector This is understood as a device that separates dense biomass (underflow) from non-dense biomass (overflow) in a biomass stream (input stream). In other words, it selects dense biomass to be returned or recycled during the process, while wasting non-dense biomass, thereby enriching the system into sludge with higher settling capacity. In this invention, the overflow comprises flocculated active biomass. The selector underflow typically recovers well-settled biomass (containing a high proportion of "dense biomass aggregates"), thus advantageously exhibiting an optimized and controlled dSVI in the range of 15 to 70 mL / g, typically having 20% ​​to 70% greater than 100 μm (up to 1000 μm; preferably 200 to 500 μm). The selector overflow typically recovers biomass with lower settling capacity (loose flocs, needle-like flocs, filamentous flocs, etc.), thus containing a high proportion of flocculated biomass, typically exhibiting a controlled dSVI ranging from 60 to 250 mL / g, and typically having a proportion of 5% to 18% of aggregates larger than 100 μm (up to 1000 μm; preferably 200 to 500 μm). In this invention, the selector is external and based on gravity (or weight). The weight selector can be a centrifuge, hydrocyclone, plate, clarifier, filter, screen, filter, classifier, or a combination thereof. Preferably, it is a hydrocyclone, for example, disclosed in US 2016 / 0137537A1. The selector can include one or more units. In other words, it can be a single selector or a dual selector. When the selector includes multiple units, these can be arranged in series or parallel, branch or split configurations.

[0074] Figure 1 A block diagram schematically illustrates the steps of a method for controlled biomass densification in the biological treatment of untreated influent 10 according to the present invention. The method includes a step 100 of subjecting the untreated influent 10 to biological treatment with freely suspended biomass, thereby producing biomass 11 comprising activated sludge AS. The biological treatment tank may contain anaerobic, anoxic, and aerobic compartments. More generally, biological treatment is any biological treatment configuration involving freely suspended biomass, preferably including, but not limited to, anaerobic steps.

[0075] The method includes step 101 of separating biomass 11 containing activated sludge AS, thereby producing effluent 12 and returning activated sludge RAS.

[0076] The method includes step 102, which involves extracting at least a portion of RAS and / or a portion of AS from activated sludge as a primary source of WAS from waste activated sludge. Extracting RAS is less costly because it exhibits a high concentration and requires less pumping work.

[0077] The method of the present invention further includes step 103 of external selection or density-based selection of at least a portion of the returned activated sludge RAS and / or a portion of the activated sludge AS, thereby generating an overflow 14 intended to be extracted as a second source 15 of waste activated sludge WAS, and an underflow 16 comprising a first portion of dense biomass aggregate 17. In step 100 or step 105, the underflow 16 is recycled during treatment. This solution enables control of the fluxes of inflow and outflow selection, thus resulting in a finer selection compared to internal selection.

[0078] The method of the present invention includes step 104 of generating and / or maintaining a first portion of dense biomass aggregate (17), such as aerobic granular sludge (AGS) or biofilm, by utilizing a dense biomass aggregate generation process (67) that utilizes at least a portion of untreated influent 10 and optionally at least a portion of internal plant recirculation (68). Step 104 occurs in dense biomass aggregate generation and / or maintenance unit 18.

[0079] The method according to the invention further includes step 105a, subjecting at least a portion of the dense biomass aggregate of step 104 and the optionally present underflow 16 to the biological treatment of step 100.

[0080] In other words, the method includes the step (105b) of subjecting a first portion of the dense biomass aggregate (17) of the underflow (16) to biological treatment and / or a dense biomass aggregate generation process (67).

[0081] The dense biomass aggregates from step 104 of generating and / or maintaining dense biomass aggregates and / or the underflow 16 in step 100 are recycled, and then densed biomass is obtained and maintained in the system, the densed biomass comprising aggregates of mixed biomass aggregates in the form of aerobic granular sludge (AGS) and activated sludge.

[0082] In a variation of the method of the present invention, step 104 is a step of supplying underflow 16 and at least a portion of untreated inflow 10, along with optionally a portion of internal plant recirculation (68), to contact tank 18 (hereinafter also referred to as feast zone 18) to form aerobic granular sludge (AGS). This results in a bioaugmentation phenomenon. Feast zone 18 increases the contact between underflow 16 containing larger-sized microbial forms and some or all of the untreated inflow 10 to promote AGS formation, preferentially growing aggregates larger than 200 μm.

[0083] On one hand, waste activated sludge (WAS) is extracted directly from the RAS or biological tank (13). The RAS or AS also refers to gravity-based selection. The WAS is also extracted as an overflow (14) via gravity-based selection. On the other hand, the underflow (16) containing recovered dense biomass aggregates (17) is sent to the production and maintenance unit, which is the contact tank. RAS is not allowed to enter the production and maintenance unit (contact zone). In this invention, only the retained aggregates are in contact with fresh carbon, which mainly promotes the growth of existing aggregates. Managing the percentage of influent load entering the abundance zone (18) is a way to control the aggregate growth rate compared to ordinary heterotrophic organisms (OHO). The more influent in the dense biomass aggregate production and / or maintenance unit (18), the more fresh carbon available in the influent is absorbed by the aggregates (17), and therefore the less available carbon is available in the OHO (ordinary heterotrophic organism).

[0084] The microbiome transformation of the present invention is controlled by extracting part or all of the WAS, particularly via selector overflow (14). This controlled extraction allows for control of the extraction amount via gravity-based selection and direct extraction (13) to mitigate aggregate waste.

[0085] This invention leads to the bio-enhancing of dense sludge through the selective extraction of excess biological sludge: preferential extraction of those with poor settling characteristics. The retention and recycling of the first portion of the dense biomass aggregates (17) in the underflow (16) in the saturation zone (18) and / or the bioreactor promotes their growth in the bioreactor and subsequent bio-enhancing. This results in the establishment of dense biomass, which provides the following advantages:

[0086] - Improvement in the absolute value of the Mohlman index (and dSVI) and limitations on its annual variability: elimination of the winter-spring “filamentous expansion” phenomenon;

[0087] - Increased settling velocity of mixed liquor, providing better clarification flexibility during the rainy season (with less risk of TSS (total suspended solids) loss at hydraulic peaks), better management of combined wastewater overflows, and minimization of spills into the natural environment;

[0088] - Significantly reduces the generation of scum and stable biological foam;

[0089] - Improve the quality of the treated water at the secondary clarification outlet.

[0090] This invention provides a novel method for controlling the percentage of dense biomass aggregates in a mixed liquor, thereby providing a way to control the dSVI of activated sludge biomass without considering the seasonality of "environmental factors".

[0091] As previously mentioned, a given plant has a certain percentage of aggregates larger than 200 μm (which induces a baseline dSVI) based on its biodesign factors and annual average environmental factors. This SVI then exhibits seasonal fluctuations throughout the year due to fluctuating environmental conditions, and follows a fairly repetitive pattern if the fluctuations in environmental factors are repeatable. Of course, better biodesign factors, such as the presence of anaerobic selectors or contact zones, induce more stable and narrower dSVI variations.

[0092] Similarly, relatively stable climate and inflow quality throughout the year will contribute to the stability of dSVI. Conversely, highly variable climate conditions, coupled with a distinct rainy season that leads to high variability in inflow quality, will produce large aggregate fluctuations, resulting in larger dSVI variations.

[0093] With the aid of selection based on external gravity, densified sludge allows:

[0094] - To maintain dense biomass aggregates in biological systems during adverse times;

[0095] - Favorable periods promote the bio-enhancing of denser aggregates;

[0096] - This leads to a controlled shift in the microbiome toward a higher proportion of aggregates, resulting in lower and narrower dSVI variations.

[0097] Figure 2 A block diagram schematically illustrates the steps of a method for controlled biomass densification in the biological treatment of untreated influent according to the present invention. The method further includes step 106 of controlling the amount of untreated influent 10 and / or internal plant return (68) supplied to the dense biomass aggregate generation process (67) in the dense biomass aggregate generation and / or maintenance unit 18. It further includes step 107 of controlling the amount of waste activated sludge WAS extracted from a first source 13 and / or a second source 15 of waste activated sludge WAS.

[0098] By controlling the extraction ratio based on external gravity selection, dSVI can be controlled to control the amount of sludge in aggregate form larger than 200 μm, and to cause a controlled transition of the microbiome to aggregates in a controlled ratio to obtain the desired dSVI.

[0099] Controlling the amount of untreated influent through the generation and / or maintenance of the dense biomass aggregates in unit 18 is one way to promote and regulate the growth of aggregates in the form of dense biomass larger than 200 μm (e.g., in the case of the sufficiency zone (18), controlling the sufficiency gradient leads to controlling the growth of the aggregate form).

[0100] Controlling the amount of WAS extracted directly and selectively extracted via external gravity allows for up-and-down adjustment of the percentage of aggregates, thereby adjusting dSVI.

[0101] Using these two levers, partial granulation of activated sludge can be managed and controlled, thereby establishing dense biomass in the form of AGS, dense aggregates, and flocculated biomass aggregates as described above.

[0102] In the method of the present invention, the dense biomass aggregate generation process 67 of step 104, which generates and / or maintains the second portion of dense biomass aggregate 171, can be carried out in a dense biomass aggregate generation and / or maintenance unit 18 supplied by underflow 16 and at least a portion of untreated inflow 10 and optionally internal plant recirculation (68), and the resulting second portion of dense biomass aggregate 171 is aerobic granular sludge (AGS). The dense biomass aggregate generation and / or maintenance unit 18 or the overflow tank 18 is advantageously aerated, anoxic, or anaerobic.

[0103] The method of the present invention may further include a meta-step 108 of supplying an additional flow 19 containing at least VFA and / or readily biodegradable material to the dense biomass aggregate generation and / or maintenance unit 18. This provides more substrate to the aggregate form to promote their growth. Controlling the supplemental load of the sufficiency zone 18 is an additional means for controlling the growth of the dense biomass aggregates 171, and therefore an additional tool for regulating SVI.

[0104] “ biodegradable carbon "Improved by those skilled in the art. For example, they are defined in "Activated Sludge Models ASM1, ASM2 and ASM3", edited by the IWA task force on mathematical modeling for the design and operation of biological wastewater treatment, Henze et al (2000), ISBN 1 900222 24 8. Examples of readily biodegradable carbon are volatile fatty acids. RBCs can be produced by fermentation, particularly as disclosed in US 6,387,264, such as in co-fermentation and thickening (UFAT) processes."

[0105] “ VFA "or" Volatile fatty acids These are also known in the art. They include lower carboxylic acids, especially C1-C4 saturated, straight or branched hydrocarbon chains substituted with COOH groups, such as acetic acid, lactic acid, and preferably acetic acid.

[0106] The method of the present invention may further include step 109 of returning at least a portion of activated sludge AS and / or at least a portion of activated sludge RAS and / or at least a portion of underflow 16 for fermentation, thereby producing a stream 20 containing VFA; and step 110 of supplying at least a portion of the VFA-containing stream 20 to the dense biomass aggregate production and / or maintenance unit 18 and / or the biological treatment. Fermentation may be a side-flow enhanced biological phosphorus removal (S2EBPR) also known as “RAS fermentation.” Its purpose is to produce VFA from the side-flow biomass fermentation. Stream 20 may exit from the saturation zone 18 and / or the biological treatment.

[0107] The method of the present invention advantageously further includes step 111 of controlling the amount of activated sludge AS undergoing fermentation step 109 or returned activated sludge RAS; and / or step 112 of controlling the amount of underflow 16 undergoing fermentation step 109; and / or step 113 of controlling the amount of VFA-containing flow 20 supplied to the dense biomass aggregate generation and / or maintenance unit 18, the remainder of which is supplied to the biological treatment. Controlling the amount of flow 20 to the saturation zone is a way to promote aggregate growth and therefore a way to regulate biomass densification (SVI).

[0108] In the method of the present invention, the dense biomass aggregate generation process 67 of step 104, which generates and / or maintains the second portion of dense biomass aggregate 171, can be a process 66 based on aeration or aerobic biofilm (e.g., Figure 5 (As shown), for example, biofiltration, which includes aerated biofiltration (BAF), membrane aerated membrane reactor (MABR), and / or moving bed biofilm reactor (MBBR). At least a portion of the untreated influent 10 and / or at least a portion of the internal plant recirculation 68 is supplied to the dense biomass aggregate generation process 67 to generate biofilm biomass, with excess biofilm biomass detaching as a freely suspended nitrifying biofilm 69 to the biological treatment process step 100.

[0109] In this case, the freely suspended nitrifying biofilm 69 output from step 104 can be included in the recirculation of the aerated biological filter (BAF) and / or the output of the aerated biological filter and / or the output of the moving bed biofilm reactor (MBBR) and / or the output of the membrane aerated biofilm reactor (MBBR). The membrane aerated biofilm reactor (MABR) can be placed in the sidestream of the biological treatment and / or within the biological treatment step 100.

[0110] When the dense biomass aggregate generation and / or maintenance unit 18 is a contact zone or a saturation zone, a membrane aerated biofilm reactor (MABR) can also be placed in the saturation zone, which serves as an anaerobic contact tank.

[0111] The observed dSVI variability (100 to 300 mL / g) in existing technologies is a limiting factor for practitioners designing clarifiers with low SOR, as the most restrictive approach in terms of clarifier design is the combination of high dSVI and peak flow rates with designed MLSS (mixed liquor suspended solids) concentrations. For temperate climate countries, this typically occurs during winter.

[0112] - The highest SVI value was observed during winter;

[0113] - In winter, the highest MLSS value is required to maintain nitrification SRT (sludge retention time).

[0114] The combination of these conditions, using the usual SVI assumption of around 120 to 180 ml / g, induces the lowest and most restrictive SOR in existing practices.

[0115] The present invention, using densified sludge, allows for stable and controlled dSVI, resulting from the aforementioned controlled microbiome transformation. The use of this technique ensures a low SVI design assumption in the range of 40 to 100 ml / g at a typical design MLSS of 4 g / L, thereby enabling clarifier SOR design in the range of 1.2 to 3.5 m / h, preferably 1.6 to 3.2 m / h. This SOR is significantly higher than current design practices, especially in France where the maximum is limited to 0.8 to 0.9 m / h. Furthermore, the ATV guidelines limit the maximum SOR of clarifiers to 1.6 to 2.0 m / h. The present invention allows for the adjustment of the SVI of biomass. Therefore, when the separation step is a clarification step, the present invention allows for the design of clarification steps outside of boundaries generally accepted by those skilled in the art.

[0116] Control steps 106, 107, 111, 112, and 113 are configured to maintain densed biomass, which has the following characteristics:

[0117] -35 to 100 ml / g, preferably 40 to 70 ml / g, and / or

[0118] - More than 10%, typically 15% to 70%, of the particles have a particle size of 100 μm to 1000 μm, and / or

[0119] -70% to 95%, 70% to 85% dSVI30 / dSVI10 ratio.

[0120] Advantageously, the densified biomass has 15% to 50% of the particles having a particle size greater than 200 μm (e.g., 200 μm to 500 μm).

[0121] Preferably, the densified biomass has 20% to 40% of the particles having a particle size greater than 200 μm (e.g., 200 μm to 500 μm).

[0122] When separation step 101 is operated in the clarifier, it can be operated using the following methods:

[0123] - Achieve thickening performance with a solids concentration of 20 to 30 g / L at the bottom of the clarifier;

[0124] - The RAS rate is approximately 30% to 60% of the inflow velocity;

[0125] The upflow velocity (SOR) is -1.0 to 4.0 m / h, preferably 1.6 to 3.2 m / h;

[0126] -8.5 to 33.8 kg MLSS / m 2 / h, preferably 10 to 22 kg MLSS / m 2 / h surface loading rate;

[0127] - Compared to traditional designs, the clarifier depth of this design is reduced by approximately 10%, and its volume is reduced by 20%.

[0128] - Compared to traditional designs, the aeration tank volume is 30% to 40% smaller.

[0129] Alternatively, the separation step (101) can be performed as an MBR membrane separation operation, which advantageously utilizes the following operations:

[0130] - The frequency of maintenance and cleaning cycles for polymer membranes is reduced, with maintenance and cleaning cycles, along with reagent consumption, consistently and significantly reduced to once a week or less, without shortening membrane lifespan, and / or

[0131] - At 20°C, using the existing cleaning frequency, the application consistently maintains a flow rate of 30 L·m. -2 ·h -1 The above average annual net filtration flux (also abbreviated as lmh) without shortening the membrane's lifespan.

[0132] The densified sludge obtained by the method of this invention falls outside the definition of granular sludge and CAS (Conditional Sludge As defined by CAS). Based on these characteristics of the obtained densified sludge, this invention can optimize the design of wastewater treatment plants and processes.

[0133] Figure 3The illustration schematically depicts one embodiment of the facility 50 according to the invention. The facility 50, for controlled biomass densification in the biological treatment of untreated influent 10, includes a biological tank 60 containing freely suspended biomass, having a first inlet 61, a second inlet 62, and a first outlet 63. The biological tank 60 is configured to be supplied at the first inlet 61 with at least a portion of the untreated influent 10 and returned activated sludge RAS to produce a mixture of treated water and activated sludge AS recovered at the first outlet 63. The facility 50 includes a separation unit 70 having a first inlet 71, a first outlet 72, and a second outlet 73. The separation unit 70 is configured to be supplied with activated sludge AS at the first inlet 71 and to produce effluent 12 recovered at the first outlet 72 and returned activated sludge RAS recovered at the second outlet 73. The separation unit 70 may be a membrane or a clarifier, preferably a sedimentation system, such as a clarifier, optionally a plate. The separation unit 70 may also be a filter or a flotation unit, such as dissolved air flotation (DAF). Facility 50 includes an extraction device 80 configured to extract at least a portion of the returned activated sludge RAS and / or a portion of the activated sludge AS as a first source 13 of waste activated sludge WAS. Facility 50 further includes an external gravity-based selector 90 having a first inlet 91, a first outlet 92, and a second outlet 93. The external gravity-based selector 90 is configured to be supplied with at least a portion of the returned activated sludge RAS and / or a portion of the activated sludge AS at the first inlet 91, and to generate an overflow 14 intended for extraction at the first outlet 92 as a second source 15 of waste activated sludge WAS, and an underflow 16 containing dense biomass aggregates 17 for recovery at the second outlet 93. The external gravity-based selector 90 may be, for example, a hydrocyclone. The facility 50 includes a dense biomass aggregate generation and / or maintenance unit 18 having a first inlet 181, a second inlet 182, a third inlet 185, and a first outlet 183. This unit 18 is configured to be supplied with at least a portion of untreated influent 10 at the first inlet 181 and optionally with underflow 16 at the second inlet 182, forming a second portion of dense biomass aggregate 171, such as aerobic granular sludge AGS or biofilm, recovered at the first outlet 183. The biological tank 60 is further configured to be supplied with dense biomass aggregate 171 and at least a portion of the recovered dense biomass aggregate 17 from the underflow 16 at the second inlet 62, thereby obtaining an aggregate of dense biomass aggregates in the form of aerobic granular sludge AGS and / or biofilm and activated sludge, the mixture constituting dense biomass.

[0134] The dense biomass aggregate generation and / or maintenance unit 18 can be a single unit or multiple units connected in series or parallel, branched or diverted. Unit 18 may optionally include a contact zone of an MABR (which can be considered a “sufficient” zone in the sense that it allows the generation and maintenance of dense biomass aggregates). Alternatively, unit 18 may be an MBBR, a trickling filter, a biofilter (e.g., BAF: aerated biofilter), an IFAS, an RBC (rotating biological contactor), or a biological disc.

[0135] Sometimes the underflow 16 is not connected to the second inlet 182 (i.e., the unit 18 is not supplied with underflow 16), especially when the dense aggregate generation unit 18 does not allow the recyclable dense biomass aggregate 17 to pass through (as is the case with a biofilter or trickle filter).

[0136] The process of forming dense biomass aggregates can be:

[0137] - In the preceding contact tank (under anaerobic, anoxic, or aerobic conditions), to promote an abundance-scarcity cycle that induces aggregation / granulation;

[0138] - Biofilm processes (which can be of different types) that produce biofilm detachment of any type of organism, with nitrifying biofilms being preferred;

[0139] - or any combination thereof.

[0140] The inoculated dense biomass aggregates are selectively retained by a selector to further enrich the biological treatment system. The mixture of aggregates and flocculent biomass present in the biological system is defined as densified sludge. The selector overflow preferentially wastes the biomass flocculated from the activated sludge.

[0141] External selectors can be hydrocyclones, centrifuges, sedimentation devices, filters, screens, sieves, classifiers, or thin plates.

[0142] Thanks to the shear stress applied to the biomass while it passes through the selector when it is a hydrocyclone, the size of dense biomass aggregates in the biological treatment mixture can be further limited to a relatively small aggregate size (100 to 500 μm, preferably 200 to 500 μm) compared to the AGS process (1 to 2 mm). This has advantages in terms of the ballast effect of the aggregates and flocculated sludge mixture, because for a given mass percentage of aggregates, the ballast effect is enhanced when the mass of the aggregates is distributed among many small, dense aggregate particles rather than among a limited number of larger, dense particles. Therefore, using a hydrocyclone as a selector helps to control the size of the aggregates to a smaller range than, for example, aggregates obtained using a screen.

[0143] Controlling the proportion of influent processed in the dense biomass aggregate generation unit 18 allows for increasing or decreasing the inoculation effect of the aggregates on the biological treatment.

[0144] Controlling the ratio of WAS extracted from direct WAS 13 and from selector overflow 14 (e.g., WAS source redistribution) can prevent the waste of dense biomass aggregates in a controlled manner.

[0145] Using these two controls enables the control of the proportion of dense biomass aggregates within the suspended biomass of a biological system in order to obtain dense biomass, which is defined as an aggregate of flocculated biomass and dense biomass.

[0146] The facility of the present invention results in a controlled transformation of the biomass microbiome for bio-enhancing dense bioaggregates through gravity-based selection in a partially granulated, freely suspended biomass system. The controlled transformation is advantageously performed in a controlled manner from values ​​below 20% to 15 to 50% aggregates, preferably 20 to 40%.

[0147] Figure 4 Another embodiment of the facility 50 according to the invention is illustrated schematically. In this embodiment, the dense biomass aggregate generation and / or maintenance unit 18 is an abundance zone. The abundance zone 18 enables selector underflow (16) containing larger-sized microbial forms to contact part or all of the untreated inflow 10 and optionally part or all of the internal plant return (68) to promote granulation. The preferred growth of the aggregates is greater than 100 μm. The abundance zone is configured to contact the recovered dense biomass aggregates (17) (or their precursors) from the underflow (16) with (preferably undiluted) untreated inflow (10) and optionally with the internal plant return (68) to induce a high matrix gradient that penetrates deeply into the dense aggregate form. Subsequent alternation between the abundance zone (18) and the biopool (60) creates an abundance-depletion effect on the aforementioned biomass, resulting in preferential growth of the organisms being able to store some matrix during the abundance period, thereby inducing aggregation / granulation. The fact that the present invention guides the growth of more compact biomass forms (aggregates of their precursors) only in the abundance zone 18 leads to even more preferential growth of aggregate forms, since these are the only forms that experience the abundance-scarcity period.

[0148] Figure 5 Another embodiment of the facility 50 according to the invention is illustrated schematically. In this embodiment, a biofilm-based process is added to enrich the system in aggregate form by sending an overgrown biofilm into the organism (60). The dense biomass aggregate generation process 67 of step 104, which generates and / or maintains dense biomass aggregates 171, is a process 66 based on anaerobic, anoxic, aerated, or aerobic biofilms, for example:

[0149] - Biological filtration, which includes aerated biological filtration (BAF) or anoxic biological filtration.

[0150] - Membrane aerated membrane reactor (MABR)

[0151] -Moving bed biofilm reactor (MBBR)

[0152] -Drip filter,

[0153] - Rotary biological contactor (RBC), also known as biological disc,

[0154] In the process of producing dense biomass aggregates, at least a portion of the untreated influent 10 and / or at least a portion of the internal plant recirculation 68 is supplied to the process of producing dense biomass aggregates, thereby producing biofilm biomass that grows excessively and detaches into the biological treatment process (60) of step 100 in the form of free-suspension biofilm 69, preferably nitrified or denitrified or anaerobic biofilm (therefore forming aggregates), preferably nitrified biofilm.

[0155] In this implementation, a sidestream or mainstream biofilm generation unit is added to the system to generate additional dense biomass in the form of a free-suspension biofilm, which is intended to be inoculated into the main bioprocessing system to further enrich the dense biomass mixture with dense biomass aggregates.

[0156] As described above, the biofilm generation unit can be a membrane aerated bioreactor (MABR), a moving bed bioreactor or an aerated or anoxic biofilter (BAF), a trickling filter, a biodisc (especially a rotating biodisc), or any form of embedded or ballasted biofilm, preferably a MABR.

[0157] The biofilm generation unit may be supplied with a portion of the influent 10, optionally to an internal plant return 68 such as a sludge line return, which may contain high ammonia levels if the sludge line is characterized by anaerobic digestion and / or advanced sludge treatment (e.g., hydrothermal carbonization, thermal hydrolysis, etc.).

[0158] The biofilm generation unit (66) treats the fouling supplied to induce biofilm growth. Excess biofilm will eventually detach from the growth medium either spontaneously (as MBBR does under aeration conditions) or through specific action (as in the case of flushing the aeration membrane in MABR or backwashing in BAF).

[0159] Excess biomass 69 produced by the biofilm generation unit then leaks at the outlet (or is intentionally backwashed in the case of BAF) into the biological tank 60.

[0160] In the proposed implementation, nitrified biofilm sheets 69 detached from the biofilm generation unit are collected and inoculated into a biological pond 60, where they combine with biological sludge to further enrich them in dense, freely suspended biofilm aggregates, which are considered to be dense biomass aggregates.

[0161] When using an aerated biological filter (BAF) that supplies a liquid containing low carbon and high ammonia (such as primary treatment wastewater inflow or digester filtrate), the BAF produces some nitrifying biofilm, which is then further inoculated into the main biological system. The MABR process also produces a large amount of nitrifying biomass. MBBR also produces some nitrifying biomass due to the long residence time of the biofilm on the medium. Optional use of internal plant recirculation (68), such as anaerobic digester filtrate or deammoniation plant effluent, also provides some temperature advantages for the easy growth of some nitrifying biofilm.

[0162] Therefore, using any of the biofilm generation processes described above (66), the mainstream biological system enriches its nitrified biomass stock through the excess biofilm generated by inoculation. Furthermore, the inoculated nitrified biofilm sheets, being of larger particle size and / or more compact than CAS biomass, can therefore preferentially remain at the gravity-based selector underflow 16. These two combined effects are synergistically amplified, as small nitrifying inoculation fluxes can be consolidated over time to gradually enrich the system with dense, nitrified biomass aggregates. These dense or larger nitrified aggregates can further grow and develop within the biological system while nitrifying some ammonia.

[0163] In this embodiment, the aeration zone (18) is optional and can enhance the synergistic maintenance effect for the microbiome transition of nitrifying organisms to dense biomass aggregates. In a specific implementation of this embodiment, dense nitrified aggregates, generated by the nitrifying biofilm generation unit and further enriched under the synergistic effect of selection based on external gravity, are collected in the underflow 16 and further contacted in the aeration aeration zone (18) with at least a portion of the plant internal recirculation 68 containing a high concentration of ammonia (specifically, anaerobic digestion filtrate or effluent from the side-stream deammoniation process), and preferably without any untreated inflow 10 being supplied to the aeration aeration zone 18. While this selected nitrifying bacteria aggregate stream benefits from the enrichment of ammonia, it also selects out OHO from the biofilm aggregates, resulting in the enrichment of the nitrifying bacteria population in the form of dense aggregates. This enables the maintenance of the nitrifying population in the system while reducing the amount of untreated inflow and / or internal recirculation treated in the biofilm generation unit. The maintenance effect can help maintain the same stock of nitrified biomass in the system biomass, while reducing the inoculation effect of nitrified biofilm generating units.

[0164] The uncoupling of nitrifying bacteria sludge retention time (SRT) unlocks some interesting technological effects due to the fact that nitrifying bacteria can be housed, grown, and maintained in a high proportion within / on dense aggregate biomass. Indeed, in such a system, nitrifying sludge preferentially growing within / on dense biomass aggregates can maintain a much longer sludge retention time in the system than flocculated activated sludge, because the mixture of dense nitrifying aggregates and activated sludge allows for highly selective extraction: while flocculated activated sludge is preferentially washed out of the system from the selector overflow 14, the nitrifying biomass aggregates 17 recovered in the underflow 16 are preferentially retained in the system. This results in a lower sludge retention time for flocculated biomass in the system, while aggregated biomass is retained for a longer period. This uncoupling of the SRT of these two biomass types offers advantages for global biological treatment systems: firstly, the lower SRT of flocculated activated sludge compared to the system's apparent average SRT leads to higher pollutant degradation kinetics (for carbon oxidation and denitrification purposes) in younger biomass. The aeration SRT of flocculent biomass can be intentionally designed to remain very low, thus below the nitrifying bacteria elution threshold within a given operating temperature range. Therefore, the flocculent biomass does not contain any nitrifying bacteria but has younger OHOs that operate at high kinetic rates. On the other hand, aggregates initially contain nitrifying bacteria, which can further develop because the aggregates remain in the system for a much longer time. Therefore, the aeration SRT of the aggregates is intentionally designed to be higher than that required for nitrification in order to establish, bioenhance, and maintain a sufficient stock of nitrifying bacteria in the biological system. A similar approach can be considered by maintaining a higher anoxic SRT, intentionally designed to be higher than that required for classical (or conventional) heterotrophic denitrification, in order to establish, bioenhance, and maintain a sufficient stock of slow-growing heterotrophic or autotrophic (e.g., anaerobic ammonia oxidizers, DAMO, or methanogenic bacteria) denitrifying bacteria in the biological system. Finally, a similar approach can be considered by maintaining a higher anaerobic SRT, intentionally designed to be higher than desired, in order to establish, bioenhance, and sustain sufficiently slow-growing hydrolysis (substrate particle breakage or enzymatic), fermentation, or any such organisms in the biological system. The fact that this invention can uncouple the SRT of OHO flocculent biomass and, for example, nitrifying bacteria biomass-supported aggregates allows the treatment tank to still undergo nitrification at an apparent SRT below the nitrifying bacteria elution threshold, thus allowing for a more compact design compared to CAS-BNR (Bionutrient Removal) or existing IFAS (Integrated Fixed Membrane Activated Sludge): CAS-BNR benefits neither from nitrifying bacteria inoculation nor from the selective retention of nitrifying agents, and IFAS benefits only from the inoculation effect of its fixed membrane portion but cannot consolidate nitrification stock when designed with a low aeration SRT due to its lack of selective retention.

[0165] The uncoupling of SRT and / or growth rate between organisms can span a continuum of selected particles because the underflow 16 of selector 90 will retain larger and denser particles compared to overflow 14. This method can create multiple niches for organisms with the highest growth rate in the smallest particles with the lowest matrix gradient characteristics (characterized by Fick's law of diffusion) and organisms with slower growth rates in the largest particles with the highest matrix gradient characteristics. A feature of the invention is the control and optimization of the selection of specific groups of organisms to operate at or near their highest activity. For example, the maximum specific growth rate of common heterotrophic bacteria is about 5 days. -1 The growth rate of nitrifying bacteria is approximately 1 day. -1 SRT (Self-Release Rate) can be uncoupled to optimize the niche for smaller or lighter particles (e.g., flocs) for faster-growing heterotrophic bacteria and larger aggregates for slower-growing nitrifying bacteria, resulting in an SRT or growth rate uncoupling ratio of 1:5. This uncoupling ratio can be altered by adjusting the selection pressure in selector devices (e.g., clarifiers, hydrocyclones, centrifuges, plates, or classifiers) to a low ratio of 1:2 to a high ratio of 1:10 (where a typical ratio is close to 1:5). The fortification of biomass detached from biofilms integrated into the process (e.g., MABRs) can further alter or increase this ratio to 1:20 or greater. For example, high-growth-rate organisms can be supported in flocs using the lowest SRT (e.g., 1 to 5 days at 20°C), medium-growth-rate organisms can be supported in granules or dense aggregates using a medium SRT (e.g., 5 to 25 days at 20°C), and the slowest-growth-rate organisms can be supported in biofilms (attachment and detachment) at ratios such as 1:5:20. Other ratios can be “introduced” as needed through biofilm management methods. The advantage of maintaining optimized SRTs based on organism growth rates helps retain the most active fraction, resulting in less decay products, including inert and endogenous debris, accumulating within the stock of rapidly growing organisms, while promoting the proliferation of typically very slow-growing “high-efficiency” organisms (e.g., nitrifying bacteria, anaerobic ammonia oxidizers, denitrifying anaerobic methanogenic bacteria (DAMO), or micropolluting degraders). Maintaining the highest “effective stock” through SRT staging or SRT uncoupling strongly contributes to process intensification and process flexibility. Examples of uncoupling could include using heterotrophic bacteria at 5 days. -1 Nitrifying bacteria grow in 1 day -1 Under growth and anaerobic ammonia-oxidizing bacteria or DAMO in 0.2 days -1Or even lower optimized support conditions for growth, resulting in a decoupling ratio of, for example, 1:5:25. Other ratios are also possible, and these decoupling methods are representative features of our invention. The SRT decoupling control steps can be performed based on adjustments to mass splitting, flow splitting, and / or particle retention efficiency at the selector. This decoupling device method automatically or manually adjusts the selection pressure in the device by changing the selection efficiency of larger particles versus smaller particles. For example, such adjustment of selection pressure can be achieved by changing the nozzles, the middle section, or the eddy current detectors in the inflow section of the hydrocyclone; or by changing the speed difference (revolutions per minute), G-force, torque, or pool depth or beach angle in the centrifuge; or by changing the hydraulic residence time or load of the classifier or plate. Adjustment of selection pressure can also be achieved by including multiple (two or more) devices in series, parallel, branch, or split configurations. When the term nitrifying bacteria is used, other organisms (such as denitrifying bacteria or anaerobic organisms) are also possible, and when the term "oxic" or "aerobic" is used, other conditions (such as anoxic or anaerobic) are also possible. It should be noted that the SRT requirement generally increases with decreasing water temperature and decreases with increasing water temperature, roughly consistent with the temperature dependence described by Arrhenius.

[0166] Figure 6 Another embodiment of the facility 50 according to the invention is illustrated schematically. In this embodiment, the dense biomass aggregate generation and / or maintenance unit comprises two units in series. One of these units is an abundance zone 18, preferably anaerobic. The abundance zone 18 is further configured to optionally be supplied at a third inlet 185 with an additional flow 19 containing at least VFA and / or readily biodegradable material. Additionally, the second dense biomass aggregate generation process 67 of step 104, which generates and / or maintains dense biomass aggregates 171, can be a process 66 based on an aerated biofilm, such as a membrane aerated membrane reactor (MABR) or a moving bed biofilm reactor.

[0167] As is known in the art, MABRs implemented in anoxic or anaerobic environments can be used for simultaneous nitrification and denitrification in a single compact reactor.

[0168] In this implementation, the facility includes a MABR as a process (66) for the formation of a nitrifying biofilm (69) and an anaerobic abundance zone 18 as a process (67) for the formation of dense biomass aggregates (171) to promote the aggregation of biomass, particularly EBPR biomass (enhanced biological phosphorus removal).

[0169] The MABR membrane can be directly installed in the anaerobic enrichment zone 18, thus providing a compact facility where one tank performs two functions, offering synergistic advantages. Biological treatment is preferably A2O or AO. In this embodiment, the advantages are:

[0170] -MABR can provide some nitrifying biofilm biomass to the system;

[0171] - Abundant anaerobic zone induces aggregation / partial granulation, producing some EBPR biomass (PAO and DPAO biomass) aggregates;

[0172] - Through specific sequential aeration control, MABR can provide some EBPR biomass.

[0173] Furthermore, hydrocyclones / selectors retain all of these densely aggregated biomass in the system through their selective biomass separation, aggregate retention, and subsequent waste of flocculated biomass.

[0174] As previously described in the previous implementation, the percentage of dense biomass aggregates in the system can be adjusted in the following ways:

[0175] - Increase the amount of inflow 10 and / or internal plant return 68 processed in the ample zone 18;

[0176] - Aggregate waste is managed by redistributing the WAS extracted from direct extraction 13 and the WAS extracted from selector overflow 14 as a second source of WAS 15.

[0177] In addition, in this embodiment, the adjustment of the continuous aeration rate in the MABR membrane can be the control point for producing more or less nitrifying biofilm.

[0178] If necessary, the ammonia concentration can be locally increased in the ample tank 18, where a MABR membrane can be installed to promote higher nitrification kinetics and thus maximize nitrification biofilm production.

[0179] Further synergistic effects were achieved in this configuration by simultaneously carrying out nitrification / denitrification reactions on the MABR membrane biofilm through the ample zone 18.

[0180] In alternative operation of the MABR, the aerated membrane is alternately aerated (full aeration or micro-aeration for more than 2 hours) and not aerated (1 to 3 hours). The medium is placed in the saturation zone 18, containing phosphorus contamination from the influent 10 and internal return 68, as well as fresh VFA from the influent, or further added to the third input 185 by introducing a VFA-containing stream 19 (e.g., external dose or S2EBPR outlet).

[0181] Alternating aerobic and anaerobic conditions on the biofilm grown on the MABR membrane will promote the formation of some EBPR biomass (PAO for polyphosphate accumulation and DPAO for denitrifying polyphosphate accumulation) in this specific operation, which will then be further inoculated into the downstream biological system. The EBPR aggregates formed through the anaerobic enrichment tank and the MABR-specific operation can be further grown and developed in a downstream biological treatment configured with A2O or AO containing the S2EBPR variant.

[0182] Compared to the CAS EBPR process, this implementation offers greater flexibility in EBPR, particularly during periods of heavy and prolonged rainfall, and / or winter conditions associated with low wastewater temperatures. In fact, in this implementation, portions of the EBPR biomass enclosed within dense biomass aggregates are selectively retained by an external density-based selector, thereby limiting EBPR biomass stock decay to the portion connected to the flocculant biomass.

[0183] Therefore, this implementation allows multiple control points to uncouple several SRTs in the system:

[0184] -OHO in flocculant biomass is kept at a low SRT to maximize its kinetics;

[0185] - Nitrifying bacteria in aggregated dense biomass are kept at high SRT to maintain nitrification stock in biological systems designed with low aerobic SRT, which would otherwise be unable to nitrify.

[0186] - EBPR biomass in dense biomass aggregates is kept within a moderate SRT range, preferably one-third the distance from OHO, in order to maintain some EBPR biomass stock.

[0187] By uncoupling the SRT provided by the combination of inoculating nitrifying biomass from MABR and selectively retaining it at the selector, it is possible to design the aerobic SRT of the biological tank to be lower than the known guidelines for integrated fixed membrane activated sludge (IFAS) without impairing nitrification (MABR is an IFAS).

[0188] In this implementation, the aerobic SRT of the biological system can be further reduced because the biomass SRT of nitrifying bacteria is uncoupled from the apparent SRT of the system. In fact, unlike existing IFAs, where the amount of media (including the MABR membrane surface) drives the amount of nitrifying bacteria in the system, thereby driving the final nitrification performance for a given aerobic demand, this invention provides a novel method for transforming the microbiome into a higher quantity of nitrifying bacteria regardless of the proportion of MABR membrane media, providing a compact system with reduced costs in relation to MABR membranes.

[0189] In one variant, the MABR membrane can be placed in the biological tank 60, preferably in the anaerobic or anoxic zone, and the MABR membrane can also be kept in the anaerobic-rich zone 18, but this is not mandatory. Such a variant allows for a more compact facility.

[0190] Furthermore, due to the MABR, some nitrification / denitrification can occur simultaneously in the anaerobic or anoxic zone of the biological system, thereby optimizing the system volume. During aeration, both MABRs can achieve further nitrifying bacteria inoculation in the densified sludge mixture. Alternatively, the first MABR located in the ample zone 18 can provide some EBPR biomass, while the second MABR located in the biological tank 60 supports nitrifying biomass.

[0191] In this variant, the inoculation of a nitrifying suspended biofilm 69 produced by an aerated biofilm-based process and its selective retention effect through a gravity-based selection step 103 allow the biological treatment 100 to meet the requirement that untreated influent 10 undergoes complete nitrification at an aeration SRT below the existing CAS nitrifying bacteria shredding limit and below the known IFAS complete nitrification requirement (see Houwelling Dwight & Daigger Glen T. - intensifying Activated Sludge Using Media-Supported Biofilms. CRC press, 2020 ISBN 978-0-367-20227-9).

[0192] Figure 7 Another embodiment of the facility according to the invention is illustrated schematically. In this embodiment, facility 50 further includes a fermentation tank 40 having a first inlet 41, a second inlet 42, and a first outlet 43. The fermentation tank 40 is configured to be supplied with at least a portion of activated sludge AS and / or at least a portion of returned activated sludge RAS at the first inlet 41, and / or to be supplied with at least a portion of underflow 16 at the second inlet 42, and to generate a VFA-containing flow 20 recovered at the first outlet 43. An abundance zone 18 is configured to be supplied with the VFA-containing flow 20 at a third inlet 185, and / or a biological tank 60 is configured to be supplied with the VFA-containing flow 20 at the second inlet 62.

[0193] Fermentation tank 40 may be a side-flow enhanced biological phosphorus removal (S2EBPR) system implemented to produce VFA from side-flow biomass fermentation. The S2EBPR outlet may flow out into the saturation zone 18 and / or the biological tank 60. The S2EBPR may be supplied by at least a portion of the underflow 16.

[0194] Controlling the proportion of VFA-containing flow 20 from outlet 43 of S2EBPR 40 to the ample zone 18 is a way to promote aggregate growth and therefore a way to regulate biomass densification.

[0195] Figure 8 Another embodiment of the facility 50 according to the invention is illustrated schematically. In this embodiment, facility 50 further includes a controller 184 for the amount of untreated inflow 10 supplied to the sufficiency zone 18. Facility 50 may further include a controller 131 for the amount of waste activated sludge extracted from a first source 13 of waste activated sludge WAS and / or from a second source 15 of waste activated sludge WAS.

[0196] Advantageously, facility 50 includes a controller 151 for the amount of activated sludge AS supplied or returned activated sludge RAS at a first inlet 41 of fermentation tank 40; and / or a controller 152 for the amount of underflow 16 supplied at a second inlet 42 of fermentation tank 40; and / or a controller 153 for the amount of VFA-containing flow 20 supplied at a third inlet 185 of saturation tank 18, the biological tank 60 being configured to be supplied with the remainder of VFA-containing flow 20 at the second inlet 62.

[0197] The technical effects and advantages of each part of the facility have already been discussed in conjunction with the method according to the present invention, and will not be discussed again here.

[0198] During operation, the following levers can be adjusted:

[0199] - The percentage of aggregates is obtained by sieving a known volume of the mixture through a 200 μm sieve and measuring the retained suspended solids, or by subtracting the sieve filtrate to infer it as the initial suspended solids. The concentration of aggregates larger than 200 μm is then divided by the initial sample MLSS concentration to obtain the percentage of aggregates in the mixture;

[0200] - Standardized analysis of SVI and dSVI as described in European Standard n°EN 14702-1.

[0201] If the percentage of aggregates drifts due to seasonal changes in environmental conditions, or if dSVI drifts, this drift can be compensated for in the following ways:

[0202] - Reduce the amount of WAS extracted directly (e.g., perform more WAS extraction via an external gravity-based selector), and / or

[0203] - Introduce a larger volume of untreated inflow 10 and / or internal plant return (68) and / or VFA-containing flow (19)(20) through the ample zone 18.

[0204] These actions will help preserve and grow the aggregates.

[0205] Stopping direct extraction from the first source (13) may also be a response to dSVI reaching a high value, which may, for example, interfere with the clarifier outlet quality.

[0206] Conversely, when seasonal environmental conditions are naturally favorable for the growth of dense aggregates, the proportion of WAS extracted via gravity-based selector overflow can be reduced, and the proportion extracted directly can be increased. This variant is advantageous in terms of energy efficiency, especially when the gravity-based selector is a hydrocyclone supplied at a higher pressure than direct WAS extraction. Reducing the proportion of raw water entering the abundance zone (18) can be an alternative or additional way to temporarily reduce the aggregate growth rate until the desired proportion of aggregates (and corresponding dSVI) is obtained.

[0207] Therefore, the present invention provides several levers to dynamically adjust the level of biomass densification, for example, depending on environmental and biological conditions.

[0208] Figure 9 It is a conceptual diagram of the microbiome transformation of a given plant, and an illustration of the CAS and operational variation boundaries of the dense sludge in terms of the proportion of dense biomass aggregates in the sludge and the resulting dSVI.

[0209] As previously mentioned, a given CAS plant exhibits a pattern of aggregate percentage and SVI variation throughout the year. The vertical arrangement of this pattern is attributed to “biodesign factors,” as indicated by the “gray squares” in the prior art (Wei et al. 2020), which show the different plants (e.g., WWTPs with different “biodesign factors”) at a given sampling time.

[0210] This relatively level of variation (or sloping from top left to bottom right) is attributed to changes in “environmental conditions.” These changes are experienced by the plant and may or may not result in bulking (an uncontrolled rise in SVI due to the overgrowth of filamentous organisms) depending on the biological design and variations in the quantity and quality of raw wastewater. Therefore, bulking (the right corner of the darker area of ​​CAS variation on the upper right of the graph) can be caused by a combination of environmental and operational factors, and unless specific chemical treatments such as shock chlorination are implemented, sludge SVI can drift uncontrollably to higher values ​​under adverse conditions. The extent of SVI drift under adverse conditions can vary from year to year depending on operational history and climate change.

[0211] By selectively implementing controlled waste of excess sludge (WAS) based on external gravity, the microbiome may shift to the left corner and exceed the normal annual variation that would occur in CAS. This results in controlled annual dSVI variation approaching or exceeding the optimal annual operating variation experienced in normal CAS operation. Examples of the normal CAS variation range based on "Biodesign Factors" and "Environmental Factors" are outlined in the "double-dotted area" on the right side of the figure.

[0212] Therefore, densified biomass allows for the elimination of annual variations caused by environmental factors, altering the settling capacity of biomass.

[0213] Example

[0214] Experimental facilities

[0215] A WWTP (Wastewater Treatment Plant) with a rated capacity of 400,000 PE (population equivalent) and equipped with a full-scale demonstration unit includes:

[0216] - Classic pretreatment: coarse sieve (40mm), fine sieve (6mm), grit and grease removal,

[0217] - The secondary biological treatment steps are distributed across four identical independent production lines. Each production line consists of an anaerobic biological tank, a sequence channel, and a related clarifier.

[0218] - Sludge treatment, which includes thickening on a drip grid and then dewatering by a centrifuge.

[0219] WWTP’s biological treatment lines are completely independent of each other, so there is no mixing of activated sludge upstream of the clarifier or at the recirculation level (RAS).

[0220] The study encompassed two independent bioprocessing lines: one designated the "control line" (Ltem); the other equipped with microbiome-transformation densification technology, similar to... Figure 4 These are called “denitrification production lines” (Ldens). These are two originally identical biological production lines, and therefore have exactly the same biological design factors. Each has a contact zone, or “pre-denitrification zone,” in which pretreated raw water and RAS are mixed. The mixture then passes through an anaerobic mixing zone, and then through a circular sequential aeration ditch equipped with fine bubble diffusers and banana leaf mixers. The output of the biological treatment falls into a deaeration structure before reaching the clarifier.

[0221] Sludge recycling is independent for each production line, and sludge mixing is not possible. Sequencing ditch aeration rate and intensity are managed through advanced aeration control based on online N-NH4 and N-NO3 analyzers.

[0222] The only difference in configuration between the two production lines is the method of sludge extraction and the presence of an overflow zone in the densification production line. Sludge from the control production line is extracted directly into the sequencing ditch, while sludge from the densification production line is extracted from the recycling tank, where a mobile pump is installed to feed it via a hydrocyclone slide rail, which serves as a selector. The flow, including the recovered dense aggregate sludge retained in the underflow of the hydrocyclone, is returned to the overflow zone at the top of the Ldens production line. The overflow from the hydrocyclone is pumped to a storage tank upstream of the sludge thickening treatment in the sludge production line.

[0223] Therefore, when operating under the same variations in "environmental factors," two production lines with the same "biodesign factors" can be compared. Thus, the significant difference in the percentage of sludge aggregates and the change in dSVI between the CAS (control production line) and the densified sludge (densified production line) will confirm the microbiome transformation hypothesis upon which this invention is based.

[0224] Analysis method:

[0225] The quality of the treated water

[0226] The quality of treated water from the two production lines is monitored weekly from composite samples taken on average every 24 hours. These samples are collected by refrigerated automated samplers located in the recovery tanks of each clarifier in the two production lines to be compared.

[0227] The monitored physicochemical parameters included pH, total COD (chemical oxygen demand), soluble COD (0.45 μm), BOD5 (5-day biological oxygen demand), N-NH4, N-NO3, N-NO2, total nitrogen (TN), total phosphorus (TP), P-PO4, turbidity, and TSS. Kjeldahl nitrogen (TKN) was derived by subtracting N-NOx from the measured TN.

[0228] Apart from pH, TSS (total suspended solids), and turbidity measurements performed according to standard methods, all other analyses were performed spectrophotometrically using the Macherey-Nagel Rapid Analytical Kit.

[0229] sludge settling

[0230] Three metrics were used to assess sludge settling capacity: the Mohlman index (SVI30), the normalized diluted sludge volume index at 2 g / L (dSVI30), and a 30-minute column batch settling test (de Kynch test) (which allows for the determination of sludge settling velocity (ISV)). Tests were conducted using freshly collected sludge (with a maximum of half an hour between sampling and return to the laboratory), under controlled ambient temperature conditions (20 ± 2 °C), with re-aeration in the laboratory for 10 minutes prior to the start of the test, and protection from direct solar radiation.

[0231] SVI and dSVI measurements were performed five times per week according to European standard EN 14709-1. A key feature was that, for fair comparison between the two production lines, dSVI was always reported as a target sludge concentration of 2.0 g / L in suspended solids. Column batch settling profiles were performed weekly according to the method described by Elena Torfs et al. (“Experimental Methods In Wastewater Treatment.” Edited by MCM van Loosdrecht, PH Nielsen, CMLopez-Vazquez and D. Brdjanovic. ISBN: 9781780404745 (Hardback), ISBN: 9781780404752 (eBook). Published by IWA Publishing, London, UK, pp. 235-262). ISV was calculated based on the steepest slope observed at three consecutive points within the first ten minutes of settling. These Kynch tests were conducted using sample concentrations in the treatment tank and sludge at a reference concentration of 2.0 g / L using treated water as a diluent.

[0232] The concentration of sludge affecting the Mohlman index results and the observed settling velocity during the undiluted Kynch test (Kynch, CJ, “A theory of sedimentation”. Transactions of the Faraday Society, Vol 48, 1952, pp 166-176), the standardization of the sludge index dSVI, and the measurement of ISV settling velocity at a low and identical reference MLSS (mixed liquor concentration) concentration (2 g / L) eliminated the “edge effect” of the experimental setup and the concentration differences between production lines, so as to enable a coherent and fair comparison of their settling indices.

[0233] Dense aggregate portion

[0234] The concentration of dense biomass aggregates was observed using sieves. A known volume of sludge was poured onto a pile of 500 μm and 200 μm sieves and gently rinsed with low tap water flow until all particles smaller than the sieves passed through. The fraction larger than 500 μm, with most debris, was excluded. The fraction retained on the 200 μm sieve was recovered by backwashing and the MLSS (105 °C, 24 h) was analyzed. The obtained aggregate mass was normalized to the sampling volume to obtain the aggregate concentration. The ratio of aggregate concentration to the original sludge concentration gives the mass percentage of the aggregates.

[0235] The generation of scum and biological foam

[0236] Scum generation on each production line is observed based on the operating time of the discharge pumps located at the degassers. Rotary scrapers collect floating debris from the surfaces of each degasser and transport it to a single tank on each production line. The scum tank is emptied when a high level threshold is triggered. Therefore, the cumulative pump operating time represents the volume of floating debris generated, making this generation monitorable even without flow meters.

[0237] result

[0238] Seasonal behavior

[0239] Historically, this plant exhibited fairly significant interseasonal behavior, with good sludge volume index (70 to 130 mL / g) at the end of summer and clear, recurring winter degradation, which was more or less heavily dependent on climatic conditions and extraction management. Historical reference values ​​for winter dSVI during filamentous bulking ranged from 150 to over 300 mL / g. Compared to this historical reference, the densification experimental production line fundamentally altered its behavior, with lower absolute values ​​of the winter sludge volume index, and particularly lower variability.

[0240] Figure 10 This shows the comparative results observed using experimental equipment. It is shown in the invention, particularly... Figure 4 All collected data on dSVI and aggregate percentage observed during the trial of the existing technology activated sludge (black square dots) production line (Ltem) parallel to the densified sludge (white round fill point) production line.

[0241] Figure 10 On the one hand, it shows the scope of application of existing activated sludge technologies, which is represented by clusters of "large square gray dots" (outlining the impact of "biodesign factors") and "small black square dots" (summarizing the impact of "environmental factor changes").

[0242] The “large square gray dot” cluster describes the existing technology variations between CAS plants based on different biodesign factors: each facility will result in a specific uncontrolled dSVI range composed of certain portions of polymerized biomass, depending on its feed water intensity (concentration, flow rate, and load) and process design configuration. The correlation between the dSVI range and the aggregate % range is represented by the dotted line. Aggregate % is a function of bioreactor system configuration and feed water intensity (Wei S. et al.). Therefore, the proportion of aggregates in the biosystem drives the dSVI, as shown by the “dotted line”.

[0243] The "small black square dot" clusters describe the existing technology variation of environmental factors for a given CAS facility. These results are from the CAS control production line (Ltem) of the given experimental example. Uncontrolled annual variation of dSVI is met in the freely suspended biomass system. 100 to 300 mL / g; 0 to 25% aggregates (of which 0 to 25%, through microscopic and sieving laboratory analysis, we estimate the major component is due to textile microfibers from toilet paper decomposition). Based on these observations from the experiment, the dense biomass aggregates contained in CAS sludge are estimated to be only in the range of 0 to 10%.

[0244] on the other hand, Figure 10 The microbiome transformation achieved using this invention in dense production lines (Ldens) demonstrates a significant bioaugmentation of the proportion of dense biomass aggregates in the biological system due to the synergistic effect of the aggregate generation process (abundance zone) and the preferential retention by the selector (hydrocyclone). The selector allows for the separation of:

[0245] - Biomass with poor settling ability (loose flocs, needle-like flocs, filamentous flocs, etc.) recovered at the selector overflow, namely "cross-point" clusters, which show an uncontrolled dSVI range (60 to 300 mL / g; 5 to 18% aggregates) similar to the "black square" clusters of the control production line, is preferentially extracted from the biological system.

[0246] - Biomass with excellent settling ability (recovered dense biomass aggregates: dense flocs, aerobic granular sludge, biofilm detached from suspension) recovered at the underflow of the selector, namely "black diamond" clusters, exhibiting an optimized and controlled SVI range of 15 to 70 mL / g; 20% to 70% of the aggregates are preferentially retained in the biological system.

[0247] The bioenhancement of dense biomass aggregates results in denser biomass in the biological system of the Ldens production line, namely denser sludge represented by clusters of “circular white filler dots”, which exhibits an optimized and controlled SVI range of 35 to 100 mL / g; and aggregates of 10 to 43%.

[0248] Figure 10 The "dashed line" designated as "this work" clearly outlines the correlation between the percentage of dense biomass aggregates and the resulting dSVI. This invention provides a method for controlling operable dSVI by controlling the proportion of dense biomass aggregates in densified sludge. As previously stated, this invention aims to partially granulate freely suspended biomass. The "dashed line" clearly delineates that increasing the aggregate percentage by more than 50% does not result in any significant additional improvement in dSVI, thus pursuing a higher aggregate ratio seems pointless in an industrial context.

[0249] Although the two production lines were operated under exactly the same environmental changes (same effluent, same contamination load, same temperature, same rainfall event), the fact that the experimental production line (Ldens) according to the invention showed a higher proportion of aggregates and a lower dSVI value and variation than the control production line (Ltem) confirms the microbiome shift.

[0250] Comparative evolution of aggregate ratio and diluted sludge volume index

[0251] Figure 11 The experimental production line according to the present invention is shown, using Figure 4 The implementation scheme yielded densified sludge (double line), and compared it with a control production line (single line) with conventional activated sludge, showing seasonal behavior in terms of aggregate percentage and dSVI. Rectangles delineate the 25th and 75th percentiles of each seasonal dataset. Dots delineate the mean of each seasonal dataset. For the densified production line (implementing the method of the present invention) and the CAS production line, the seasonal mean is represented by circles and squares, respectively. This figure shows a comparative seasonal statistical reclassification of dSVI and aggregate percentage observed during the trial period for a CAS production line parallel to the densified sludge production line according to the method of the present invention. The data provided here are consistent with... Figure 10 The data is the same as in the previous one, but this time it is organized by season in order to observe the evolution of dSVI and the variability of aggregate percentage.

[0252] These data show:

[0253] - The increased percentage of aggregates observed on the dense production line (dual line) relative to the CAS (single line) was reinforced over time;

[0254] - Narrower intra- and inter-seasonal dSVI variation of dense sludge (EXP line with "double line" profile) compared to CAS (CAS line with "single line" profile);

[0255] - Lower absolute value of dSVI for densed sludge (double line).

[0256] In contrast, the CAS control production line sludge experienced an expansion period during winter, resulting in a loss of aggregate proportion and a deterioration in its dSVI. The densified sludge, however, maintained its aggregate proportion throughout the winter and further enhanced it over time, thus exhibiting excellent settling characteristics at a controlled low dSVI. It has been confirmed that densified sludge is impervious to changes in environmental factors, yet these changes significantly affect the settling ability of CAS sludge.

[0257] Since the environmental and biodesign factors were identical for both production lines during the experiment, Figure 11 The significant differences in seasonal patterns observed between the two different types of sludge further confirm the microbiome transformation obtained using the present invention.

[0258] When observing the data from the CAS control production line (square dots and single lines), a fairly periodic behavior of the naturally occurring aggregate proportion and dSVI pattern can be observed due to changes in environmental factors: in winter and spring, the CAS production line loses its aggregate proportion due to sludge waste and because environmental conditions prevent the formation or maintenance of aggregate forms. An unavoidable effect is the increase in dSVI during the winter, which may be further induced by filamentous organisms, which may appear and proliferate during this specific period. As meteorological conditions improve throughout spring and summer, dSVI gradually improves when the highest aggregate proportion is reached. It should be mentioned that the scheme used for the aggregate portion distinguishes the retained biomass only by size: for the CAS production line, the higher autumn and winter results in terms of aggregate proportion compared to summer can be related to the filamentous bulking of sludge, as filamentous flocs can be larger than sieve meshes and are therefore explained in the results, but they do not actually meet the definition of "dense" given for dense biomass aggregates. However, the dSVI pattern observed in CAS largely illustrates the uncontrollable interannual variability of traditional activated sludge due to changing environmental factors.

[0259] When observing the data on densified biomass (dots and double lines), it can be noted that, when operating according to the present invention, the percentage of aggregates had already deviated from CAS behavior in the first quarter. Furthermore, unlike CAS biomass, the increased percentage of aggregates in autumn did not decrease during the adverse environmental factors of winter. The continuous increase in the percentage of aggregates and dSVI along spring illustrates a gradual microbiome shift towards dense biomass aggregates in the experimental production line operated according to the present invention. In summer, the densification production line has reached the aggregate ratio (preferably 20 to 40%) targeted by the present invention, and sludge waste is then adjusted between two sources of spent activated sludge to maintain this controlled aggregate ratio in subsequent operations.

[0260] Comparative analysis of sludge settling velocities

[0261] Further testing has demonstrated that the settling rate of the densified sludge according to the present invention is significantly higher than that of conventional activated sludge. In the tested WWTP at the current operating concentrations encountered in winter (MLSS of 2.5 to 4 g / L), the settling velocity of the densified sludge consistently remained above 1.44 m / h, with an average of 3.35 m / h, while the average for conventional activated sludge was 1.38 m / h. Under these favorable conditions, the densified sludge reached a maximum settling velocity of 9.0 m / h during the summer, while CAS sludge only reached 5.0 m / h.

[0262] Furthermore, the selective effect of the hydrocyclone selector was observed on the extracted sludge: those retained in the underflow had excellent settling characteristics with velocities greater than 6 m / h, while the "light" portion released in the overflow settled significantly worse than the supplied densified sludge, but was still better than the CAS control production line.

[0263] Considering these quantified phenomena, there might be a potential issue of lower quality sludge extracted as the second source of WAS proposed in this invention (i.e., hydrocyclone overflow). The results obtained do not appear to confirm this hypothesis; instead, they demonstrate an overall improvement, including the so-called “light” portion of the densification production line. Because the settling velocity of the sludge from the hydrocyclone overflow, measured during the experiments, was greater than that of the control production line, the selective pressure during extraction allowed for the gradual enrichment of the densified biomass. Therefore, the portion released in the overflow eventually improves its settling capacity over time, reaching levels higher than conventional biomass, and more particularly during winter, when filamentous bulking occurs in the CAS production line due to adverse environmental factors.

[0264] Impact on treated water

[0265] Studies of the quality of the treated water showed slight improvements in almost all parameters studied for the densification production line. There were no significant changes in the dissolved forms of soluble COD, mineral nitrogen, or ammonia nitrogen. However, as demonstrated by the TSS and turbidity results, densification of the sludge had a significant impact on reducing particulate matter pollution: sludge densification made the clarification system more flexible under peak hydraulic rainfall conditions, resulting in better TSS quality stability at discharge. Performance dispersion was significantly reduced during the study period, with the average TSS value for the densified production line being 6.9 (±2.0) mg / L, compared to an average TSS value of 11.9 (±5.9) mg / L for the control CAS production line. The standard deviation around the mean of Ldens was significantly reduced.

[0266] The performance gains of densified sludge in reducing particulate matter pollution resulted in slight but significant improvements in total nitrogen, Kjeldahl nitrogen, and total phosphorus parameters associated with TTS quality improvement.

[0267] Impact on the amount of scum produced

[0268] Another advantage of the densification achieved using this invention is the reduction of scum and floating matter. This positive effect, which was not anticipated at the start of the project, was first visually observed at the degassing tank, on the surface of the clarifier, and in the anaerobic zone at the top of the biological treatment production line.

[0269] Before densification was implemented on the experimental production line during the winter, both production lines exhibited similar levels of floating matter production. However, for the Ldens production line, when densification was carried out at the appropriate location on the experimental production line, this production was reduced to almost zero in the following winter. This effect can be explained by selective pressures in sludge extraction, which tends to preferentially discharge filamentous bacteria to the sludge production line. Microscopic observation revealed that the densified biosludge had a more compact biomass appearance, with more defined and fewer branched flocs and containing fewer filamentous organisms. Microscopic observation clearly demonstrated the transformation effect of the treatment system towards densified biomass: the activated sludge biomass operated according to the invention migrated in the form of aggregates of dense flocs and aggregates, which endowed it with increased settling properties.

[0270] Enhanced oxygen transport

[0271] During the trials, it was confirmed that the dissolved oxygen (DO) profiles obtained during daily automated air pulses (for dispersant preservation purposes) differed for CAS and densified biomass. Despite applying similar MLSS and similar loads to the experimental production line and the CAS control production line according to the invention, densified biomass appeared to reach higher DO levels in a shorter time.

[0272] Several tests were conducted to establish behavioral differences in in-situ oxygen transfer in the sludge during testing. The test involved stopping air in the biological treatment aeration zone for a required period to achieve zero dissolved oxygen (DO) levels, then restarting aeration at full blower capacity for approximately one and a half hours, followed by reducing blower capacity for approximately one and a half hours, and then stopping air again to observe sludge oxygen uptake (OUR). The obtained DO profile is shown below. Figure 12 As shown.

[0273] Figure 12 This represents the comparative oxygenation curves measured and recorded every 10 seconds on densified sludge (single line) and CAS sludge (double line) during the in-situ oxygenation test using probes on the production line. The simulated DO values ​​are depicted with dotted and dashed lines, respectively, for densified sludge and CAS sludge. Square dots and circles represent the time periods for calculating OUR for densified sludge and CAS sludge, respectively.

[0274] This graph qualitatively shows that, despite having equivalent blower capacity and similar OUR (in fact, OUR is slightly higher in the densified production line), the DO of densified sludge rises faster and higher than that of CAS sludge.

[0275] Using a simple parametric model, the DO was modeled based on a combination of α*Kla (αKla) factor parameters, measured OUR, and field physical conditions (Atm pressure, temperature, pool depth):

[0276]

[0277] in

[0278] Cx is the simulated DO concentration in the liquid.

[0279] α is the α factor, which reflects the impact of transfer loss due to the presence of sludge compared to clean water transfer;

[0280] Kla is the volumetric mass transfer coefficient of the aeration system.

[0281] Cs* is the saturated oxygen concentration in the water under the experimental conditions (temperature and pressure, as well as supersaturation due to pool depth).

[0282] OUR is the oxygen uptake rate of biomass.

[0283] Since both Kla and the α factor were unknown in this test, only the combined αKla value could be obtained in this experiment. The model parameter αKla factor was fitted using the least square root error reduction method between actual DO data and modeling data to obtain approximate α*KLa factor values ​​in both cases. The obtained ratio of αKla for the densified sludge production line to that for the CAS production line provides some insights into the benefits of aeration delivery. The results indicate that the αKla value for densified sludge is approximately +15% to +25% compared to CAS sludge. Both production lines were precisely configured with the same diffuser system and blower capacity; in both cases, Kla was considered equal. Therefore, based on the observations, for a given MLSS concentration, the α factor for densified sludge should be superior to that for CAS sludge.

[0284] It is hypothesized that, compared to CAS, for a given MLSS concentration, the sludge morphology obtained using the microbiome transformation according to the present invention can reduce sludge viscosity and bubble interference. Therefore, aeration transfer can be improved by enhancing the α factor.

[0285] Further dedicated research and testing are needed to more accurately measure the α factor using appropriate equipment and standard methods in order to fully understand the implications and benefits of densified sludge for oxygen transfer efficiency. However, the rapid assessment methods described above reveal that the densified sludge according to the present invention enhances the oxygen transfer rate; the driving mechanism of this enhancement remains to be investigated.

[0286] Sludge thickening capacity and clarifier design

[0287] Figure 13This describes the results for densified sludge (black continuous line with diamond-shaped dots) and CAS sludge (black continuous line with round dots) during sludge thickening tests conducted on a laboratory scale. Freshly sampled sludge was placed in a 15 cm diameter, 55 cm high staged settling column for a 2-hour thickening test. Sludge concentrations were calculated based on the initial mass introduced into the dynamic evolution of the sludge layer volume. Both types of sludge were sampled on the same day during the summer season, with dSVI values ​​of 37 ml / g for densified sludge and 107 ml / g for CAS sludge.

[0288] Thickened contours as Figure 13 As shown. These clearly demonstrate that densified sludge thickens much faster than CAS sludge and reaches a much higher final 2-hour thickening concentration:

[0289] - The densified sludge reached the final concentration of CAS sludge of 15 g / L MLSS after only 6 minutes and 2 hours.

[0290] - The densified sludge achieved a final thickening concentration of 40 g / L MLSS after 2 hours, which is 2.66 times that of CAS sludge.

[0291] In contrast, the ATV standard guidelines use the following equation to model the thickening behavior of activated sludge over time:

[0292]

[0293] in:

[0294] Simulated sludge concentration of Sr obtained as g / L MLSS

[0295] In the ATV guidelines, C is a fixed factor equal to 1000.

[0296] dSVI, the diluted sludge volume index of sludge in ml / g.

[0297] tth is the thickening time in hours.

[0298] like Figure 13 The simulated densified sludge thickening plotted according to the ATV guidelines (dotted line: simulation based on ATV–Sr=1000 / 37*tth^(1 / 3)) does not match the actual thickening behavior obtained.

[0299] An improved simulation method was tested by modifying the C-factor value in the ATV guidelines to better match the actual situation of densified sludge thickening. A C-factor of approximately 1250 was found to be suitable for obtaining a simulated 2-hour final concentration that matched the measured concentration. This improved ATV method for the thickening behavior of densified sludge was also plotted in [the relevant database / platform / etc.]. Figure 13(Dotted line: Simulation based on the improved ATV–Sr=1250 / 37*tth^(1 / 3)).

[0300] Figure 14 Several sludge thickening tests conducted at different times and under SVI conditions were summarized, showing the thickening concentrations obtained after 1 hour (diamond) and 2 hours (circle) for underflow sludge (black filler point), densified sludge (grey filler point), and CAS sludge (white filler point). According to SVI, these results correspond to the original ATV model (grey line) and the modified ATV model (black line) proposed above for thickening times of 1 hour (discontinuous line) and 2 hours (continuous line).

[0301] Within a wide SVI range, the obtained densified sludge and underflow sludge points match the modified ATV model. Using this invention, within a reasonable thickening time of 1 or 2 hours, an achievable final thickening concentration of 20 g / L to 40 g / L of dSVI can be achieved for the densified sludge. The higher thickening rate allows for a 50% reduction in RAS rate, which in turn reduces the hydraulic load on the clarifier by 25%.

[0302] Compared to the CAS standard of ATV, the further impacts of densification can be summarized as follows:

[0303]

[0304] This superior thickening ability of densified sludge allows for clarifier designs that are not possible with existing technologies. In particular, they allow for the design and operation of secondary clarifiers with approximately 50% lower RAS rates and 25% higher surface overflow rates, resulting in 10% lower clarifier depth, 20% smaller clarifier surface area, and 37.5% smaller aeration tank volume. An exemplary design summary is given in the table below.

[0305]

[0306] in conclusion

[0307] The present invention provides a method and apparatus that allow controlled implementation of densified biomass to maintain dSVI in activated sludge systems at 35 to 100 ml / g, wherein the densified biomass is a dense biomass aggregate and a flocculent biomass aggregate.

[0308] It is important to note that the goal of this invention is not complete granulation, but rather a controlled proportion of granulated form in the mixture, wherein the appropriate proportion of the more compact biomass form required to obtain low dSVI can be controlled and stabilized year-round regardless of changes in climatic conditions (e.g., regardless of environmental factors).

[0309] This invention demonstrates high potential in the following aspects:

[0310] - To improve the performance and competitiveness of biomass densification in continuous flow bioreactors by combining it with a description of best-in-class implementations with ample zones (aerated, anoxic, non-aerated), controlled influent flow reduction methods, direct and selector overflow WAS source flow reduction, recirculation and bypass EBPR.

[0311] - Increase the competitiveness of clarifier and bioreactor volumes, which can be achieved by intelligently integrating the selector to maximize densification success and control, and by combining it with other technologies such as biofilm MABR to achieve synergistic effects;

[0312] - Expand the impact of densification by strengthening the control of "microbiome transformation" and biomass stock;

[0313] -Super enhancement of biomass densification, which combines it with biofilm-based processes through multiple SRT management methods and reducing the minimum aeration SRT of nitrifying bacteria.

[0314] Optimize stock and kinetic potential of all biomass types by controlling the SRT uncoupling ratio.

Claims

1. A method for controlled biomass densification in the biological treatment of untreated influent (10), characterized in that... The method includes: The untreated influent (10) is subjected to a biological treatment step (100) of free-suspension biomass to produce biomass (11) containing activated sludge (AS). The step (101) of separating and / or clarifying activated sludge (AS) produces effluent (12) and returned activated sludge (RAS). The step (102) of extracting at least a portion of the returned activated sludge (RAS) and / or a portion of the activated sludge (AS) as a first source of waste activated sludge (WAS); The step (103) involves selecting at least a portion of the returned activated sludge (RAS) and / or a portion of the activated sludge (AS) based on external density, thereby generating an overflow (14) intended to be extracted as a second source (15) of waste activated sludge (WAS), and an underflow (16) comprising a first portion of dense biomass aggregate (17). The step (104) involves generating and / or maintaining a second portion of dense biomass aggregates (171) using at least a portion of the untreated inflow (10) through a dense biomass aggregate generation process (67). Step (105) of subjecting the second part of dense biomass aggregate (171) to biological treatment; The steps of subjecting the first portion of the dense biomass aggregate (17) of the underflow (16) to the biological treatment and / or the dense biomass aggregate generation process (67); This results in the formation of dense biomass; Step (106) of controlling the amount of the untreated influent (10) supplied to the dense biomass aggregate generation process (67) and / or step (107) of controlling the amount of the waste activated sludge (WAS) extracted from the first source (13) and / or from the second source (15) of the waste activated sludge (WAS): The above steps are configured to maintain dense biomass, said dense biomass having: 35 to 100 ml / g dSVI, and / or Particles comprising more than 10% by weight have a particle size of 100 µm to 1000 µm, and / or 70% to 95% dSVI30 / dSVI10 ratio.

2. The method according to claim 1, wherein the dense biomass aggregate generation process (67) of step (104) of generating and / or maintaining the second partial dense biomass aggregate (171) is carried out in a contact zone supplied by the underflow (16) and at least a portion of the untreated inflow (10), and wherein the generated second partial dense biomass aggregate (171) is typically aerobic granular sludge (AGS).

3. The method according to claim 2, wherein the contact zone comprises a membrane aerated biofilm reactor (MABR) disposed within the contact zone.

4. The method according to any one of claims 1 to 3, wherein the dense biomass aggregate generation process (67) of the step (104) of producing and / or maintaining the second portion of dense biomass aggregate (171) includes a process (66) based on aerobic, anoxic or anaerobic biofilms. The process of generating dense biomass aggregates (67) supplies at least a portion of the untreated influent (10) to generate biofilm biomass, with excess biofilm biomass detaching into the biological treatment process step (100) in the form of freely suspended nitrifying, denitrifying, or anaerobic biofilm (69).

5. The method according to any one of claims 1 to 3, further comprising: Step (111) to control the amount of activated sludge (AS) undergoing the fermentation step or the amount of RAS returned to activated sludge; and / or Step (112) of controlling the amount of the underflow (16) undergoing the fermentation step; and / or Step (113) of controlling the amount of VFA-containing stream (20) supplied to the dense biomass aggregate generation and / or maintenance unit (18), wherein the remainder of the VFA-containing stream (20) is supplied to the biological treatment.

6. The method according to any one of claims 1 to 3, further comprising the step (108) of supplying an additional stream (19) comprising at least VFA and / or readily biodegradable carbon to the dense biomass aggregate generation process (67).

7. The method according to any one of claims 1 to 3, wherein The step (106) of controlling the amount of the untreated influent (10) supplied to the dense biomass aggregate generation process (67), and / or Step (107) of controlling the amount of waste activated sludge (WAS) extracted from the first source (13) and / or from the second source (15) of the waste activated sludge (WAS), and / or The above steps are configured to maintain dense biomass, said dense biomass having: 40 to 70 ml / g dSVI, and / or Maintain a particle size of 200 µm to 500 µm for particles comprising 20% ​​to 40% by weight, and / or 70% to 85% dSVI30 / dSVI10 ratio.

8. The method according to any one of claims 1 to 3, wherein: The separation step (101) is carried out in a clarifier, which is operated to achieve: A thickening effect with a solids concentration of 20 to 30 g / L is achieved at the bottom of the clarifier, and / or The RAS rate is 30% to 60% of the inflow velocity, and / or Upflow velocity (SOR) of 1.0 to 4.0 m / h, and / or 8.5 to 33.8 kg MLSS•m -2 h -1 Surface loading rate, and / or Compared to traditional designs, this design achieves a 10% reduction in depth and a 20% reduction in volume. Compared to traditional designs, the aeration tank volume is reduced by 30% to 40%. Alternatively, the separation step (101) can be carried out in a membrane reactor (MBR), which is operated to achieve: The frequency of maintenance and cleaning cycles for polymer membranes is reduced, with maintenance and cleaning, along with reagent consumption, consistently and significantly decreased to once a week or less, without shortening membrane lifespan. At 20°C, using existing technology and a cleaning frequency consistently at 30 L•m -2 •h -1 The above average annual net filtration flux is achieved without shortening the membrane's lifespan.

9. A facility (50) for controlled biomass densification in the biological treatment of untreated influent (10), said facility comprising: A biological tank (60) containing free-suspension biomass having a first inlet (61), a second inlet (62) and a first outlet (63) is configured to be supplied at the first inlet (61) with at least a portion of the untreated influent (10) and returned activated sludge (RAS) to produce a mixture of treated water and activated sludge (AS) recovered at the first outlet (63); A separation unit (70) having a first inlet (71), a first outlet (72) and a second outlet (73) is configured to be supplied with activated sludge (AS) at the first inlet (71) of the separation unit (70) and to produce effluent (12) recovered at the first outlet (72) of the separation unit (70) and recycled activated sludge (RAS) recovered at the second outlet (73) of the separation unit (70); An extraction device (80) is configured to extract at least a portion of the returned activated sludge (RAS) and / or a portion of the activated sludge (AS) as a first source of waste activated sludge (WAS) (13). An external gravity-based selector (90) having a first inlet (91), a first outlet (92), and a second outlet (93) is configured to be supplied at the first inlet (91) of the external gravity-based selector (90) with at least a portion of the returned activated sludge (RAS) and / or a portion of the activated sludge (AS), and to generate an overflow (14) at the first outlet (92) of the external gravity-based selector (90) to form a second source (15) of the waste activated sludge (WAS) and an underflow (16) containing a first portion of dense biomass aggregate (17) recovered at the second outlet (93) of the external gravity-based selector (90). A dense biomass aggregate generating and / or maintaining unit (18) having a first inlet (181), an optional second inlet (182), an optional third inlet (185), and a first outlet (183), the dense biomass aggregate generating and / or maintaining unit (18) being configured to be supplied with at least a portion of the untreated influent (10) at the first inlet (181) of the dense biomass aggregate generating and / or maintaining unit (18), and optionally supplied with the underflow (16) at the second inlet (182) of the dense biomass aggregate generating and / or maintaining unit (18), and forming a second portion of dense biomass aggregate (171) recovered at the first outlet (183) of the dense biomass aggregate generating and / or maintaining unit (18); The bioreactor (60) is further configured to be supplied at the second inlet (62) of the bioreactor (60) with a second partially dense biomass aggregate (171) produced by the generating and / or maintaining unit (18), and optionally with at least a portion of the first partially dense biomass aggregate (17) of the underflow (16) to obtain dense biomass. A controller (184) for the amount of the untreated inflow (10) supplied to the dense biomass aggregate generation and / or maintenance unit (18) and a controller (131) for the amount of the waste activated sludge (WAS) extracted from the first source (13) of the waste activated sludge (WAS) and / or from the second source (15) of the waste activated sludge (WAS).

10. The facility (50) according to claim 9, wherein the dense biomass aggregate generation and / or maintenance unit (18) is a contact zone and / or a membrane aerated biofilm reactor, or includes a contact zone of a membrane aerated biofilm reactor.

11. The facility (50) according to any one of claims 9 or 10, wherein the dense biomass aggregate generation and / or maintenance unit (18) is further configured to be supplied with an additional flow (19) comprising at least VFA and / or readily biodegradable carbon at the third inlet (185).

12. The facility (50) according to claim 9 or 10, comprising a fermentation tank (40) having a first inlet (41), a second inlet (42) and a first outlet (43), the fermentation tank (40) being configured to be supplied with at least a portion of the activated sludge (AS) and / or at least a portion of the returned activated sludge (RAS) at the first inlet (41) of the fermentation tank (40), and / or to be supplied with at least a portion of the underflow (16) at the second inlet (42) of the fermentation tank (40), and generating a VFA-containing flow (20) recovered at the first outlet (43) of the fermentation tank (40), the dense biomass aggregate generation and / or maintenance unit (18) being configured to be supplied with the VFA-containing flow (20) at a third inlet (185) of the dense biomass aggregate generation and / or maintenance unit (18), and / or the bioreactor (60) being configured to be supplied with the VFA-containing flow (20) at the second inlet (62) of the bioreactor (60).

13. The facility (50) according to claim 12, further comprising: A controller (151) for the amount of activated sludge (AS) supplied or returned activated sludge (RAS) at the first inlet (41) of the fermentation tank (40); and / or A controller (152) for the amount of underflow (16) supplied at the second inlet (42) of the fermentation tank (40); and / or A controller (153) controls the amount of the VFA-containing flow (20) supplied at the third inlet (185) of the dense biomass aggregate generation and / or maintenance unit (18), wherein the bioreactor (60) is configured to be supplied with the remainder of the VFA-containing flow (20) at the second inlet (62) of the bioreactor (60).

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