Method for filtering tannery wastewater and tannery wastewater treatment system

Abstract

The invention relates to a method for filtering tannery wastewater, said method comprising the steps of: microfiltering a wastewater input of said wastewater in at least one microfilter (MF), thereby separating said wastewater input into a first trapped stream (FRS) comprising organic compounds and a first permeate stream (FPS); establishing a reverse osmosis input stream (ROIS) based on the first permeate stream (FPS) or a derivative thereof; reverse osmosis filtration is performed through a reverse osmosis filter (ROF) based on the reverse osmosis input stream (ROIS) to establish a reverse osmosis trapped stream (RORS) and a reverse osmosis permeate stream (ROPS) wherein the wastewater comprises one or more side streams of the tanning process.

Description

Technical Field

[0001] The present invention relates to a tannery wastewater filtering method according to claim 1 and a tannery wastewater treatment system according to claim 56. Background Art

[0002] Regarding leather industrial processes, the use of chemical compounds as water-based or solvent-based treatment agents generates different types of effluents, which often pose challenges or limitations to process efficiency. In addition, many industrial processes generate complex wastes that sometimes have to be handled carefully. This is of course expensive and the subsequent treatment of such wastewaters can be energy intensive. Summary of the invention

[0003] The present invention relates to a method for filtering leather wastewater, the method comprising the following steps:

[0004] microfiltering a wastewater input of said wastewater in at least one microfilter (MF) thereby separating said wastewater input into a first retentate stream (FRS) comprising organic compounds and a first permeate stream (FPS);

[0005] establishing a reverse osmosis input stream (ROIS) based on the first permeate stream (FPS) or a derivative thereof;

[0006] A reverse osmosis filtration is performed on the reverse osmosis input stream (ROIS) through a reverse osmosis filter (ROF) to establish a reverse osmosis retentate stream (RORS) and a reverse osmosis permeate stream (ROPS), wherein the wastewater comprises one or more side streams of the tanning process.

[0007] Complex effluents, such as waste streams from the tanning industry, contain a wide variety of molecules that, if separated into different fractions, can be valorized or processed in a variety of ways. In addition, the initial mixture reduces the performance of separation technologies that target the smallest molecules or particles (such as reverse osmosis membranes) and potentially has a negative impact on water quality.

[0008] In this context, "effluent" is understood to be the liquid stream that leaves the process, while "influent" is understood to be the liquid stream that enters the process. Thus, in the present case, industrial effluent is what becomes the influent of the present filtration method and system. Otherwise, these effluents may be discharged from the factory / town to a water body, a local treatment plant or a sewer.

[0009] Separation methods can be combined and applied in cascade, which allows the sequential removal of classes of compounds. Thus, deterioration of the separation technique, for example due to fouling of the filter elements, is limited.

[0010] The application of cascade membranes enables the characteristics of each side stream to be used for high-value utilization and further protects subsequent filter elements from harmful contaminants.

[0011] In this context, wastewaters that are relatively rich in organic compounds are not necessarily considered and treated as problematic wastes, but wastewater treatment may actually output valuable organic compounds, such as effluents from tanning process steps, which can be used to produce biogas in a biogas reactor and / or for the production of other fuels.

[0012] Another advantageous feature is that the wastewater treatment system can reduce hydraulic loads because aerobic treatment can be significantly reduced compared to conventional wastewater treatment involving a biological treatment process as an initial treatment step, and because the process provides a side stream comprising carbon compounds that can be used to produce biogas and / or other fuels. This can therefore advantageously result in a reduction in net energy consumption, and may also reduce net sludge production - and therefore reduce the disposal of sludge resulting therefrom.

[0013] In conventional treatment systems, the disposal and treatment of such complex waste is costly and energy intensive, and often results in the destruction of the organic and mineral resources contained in the waste, whereas the wastewater treatment system of the present invention provides both an efficient and reliable filter and an improved net energy feature.

[0014] In the present context, the term "wastewater" is not only traditionally understood as sewage, but also as effluent generated by industrial processes. In addition, the term "wastewater" refers to the total waste stream flow available in the process of the scope, while the term "wastewater input" refers to one or more "substreams" from one or more individual process steps in the process of the scope. Such substreams may also be referred to as "sidestreams". Therefore, when the term "wastewater input subset" or "sidestream subset" or "one or more substreams" is used, it may refer to one wastewater input (effluent from one process step), two or more wastewater inputs (effluent from two or more process steps), or to the total term of wastewater (total waste stream flow of the process). In this document, if not otherwise specified, any effluent or substream may be suitable as wastewater input for any level of filtration.

[0015] In other words, the total available waste stream can be filtered as a whole, or the method can be applied to filter only part of the total wastewater by subjecting one or more substreams of the total available wastewater to the filtration according to the invention. It should also be noted that some industrial processes provide wastewater to be filtered that output a total mixed liquid substance, wherein all components to be filtered are in the mixed stream and must therefore be treated as such, whereas processes involving separate separation steps can advantageously be filtered according to the invention by filtering one or more separate sidestreams separately to optimize the separate filtration. Thus, according to the invention it may mean filtering only one separate sidestream, thereby improving overall benefits, such as energy consumption, even if only one or more parts of the wastewater are filtered.

[0016] In one embodiment of the invention, the wastewater comprises a subset of one or more side streams of the tanning process.

[0017] In one embodiment of the invention, wastewater is provided based on effluent from one or more tanning process steps.

[0018] In this context, the wastewater filtration method can advantageously be used for the treatment of effluent from a tanning process. The tanning process herein refers to a series of tanning process steps for converting animal hides into so-called leather materials. A tanning process step is understood to be a sub-process of the entire tanning process, such as a soaking step, a liming step, a bating step, a pickling step, a tanning step, a fatliquor step and / or a drying step.

[0019] It goes without saying that the content of organic compounds may vary depending on whether the effluent originates from a single tanning process step or from a combined subset of tanning process steps, or whether the filtration method is applied to the entire effluent pool (i.e., mixed from all or most of the relevant tanning process steps).

[0020] In this context, tanning processes may refer to tanning processes related to animal hides as well as tanning processes related to source materials other than animals. Examples of such non-animal source materials may include fungal mycelium. In such an arrangement, the tanning step of the tanning process may be more accurately referred to as a plasticizing step, for example in the form of a cross-linking step.

[0021] In one embodiment of the present invention, the wastewater is the effluent from a tanning process step.

[0022] In one embodiment of the present invention, the wastewater is the effluent from two or more tanning process steps.

[0023] In one embodiment of the invention the effluent is from one or more tanning process steps of a tanning process such as soaking, SOA, liming, LIM, deliming, DE-LIM, bating, pickling, tanning, TAN, dyeing, DYI and fatliquoring, FAL.

[0024] In one embodiment of the invention, the organic compound content of the first retentate stream (FRS) is at least 25%, such as at least 50%, such as at least 75% by weight of the wastewater input.

[0025] In this context, it should be understood that a slight reduction in the organic content is acceptable before subjecting the feed to the process of the invention, but in order to properly utilize the very attractive properties of the process of the invention, this reduction should be kept as low as possible. The organics can be obtained in the retentate of the initial microfilter filtration, and optionally, the permeate can be further filtered by a downstream filter (such as a nanofilter or ultrafilter) to maximize the energy yield of the wastewater treatment.

[0026] Herein, a microfilter may be defined as a filter having an open pore structure and a pore size between 5 nanometers and 2 micrometers, such as between 5 nanometers and 1 micrometer, such as between 5 nanometers and 200 nanometers, such as between 5 nanometers and 100 nanometers, such as between 5 nanometers and 60 nanometers, such as between 10 nanometers and 50 nanometers.

[0027] The microfiltration process may advantageously include a pump mounted on the processing equipment to allow the liquid to pass through the filter element. Filtration through the microfilter may be performed by cross-flow filtration or dead-end filtration.

[0028] In one embodiment of the present invention, the first retentate stream and / or its derivative (FRS) is subjected to anaerobic digestion.

[0029] In this context, it should be emphasized that the first retentate stream can be directly subjected to anaerobically treatment or advantageously after some intermediate treatment. Such intermediate treatment may be, for example, the removal of ammonia or other compounds that are undesirable for converting the first retentate stream or its derivatives into biogas and / or other fuels.

[0030] In one embodiment of the present invention, the first retentate stream and / or its derivative (FRS) is subjected to anaerobic digestion and thereby converted into biogas.

[0031] In this context, biogas and other types of fuels are attractive products from the first retentate stream because the biofuels represent a "reuse" or recycling of waste, which can actually reduce the net energy consumption of the wastewater treatment system because the high energy gain obtained by filtering organic compounds during the initial microfiltration process can more than compensate for the relatively high energy consumption associated with subsequent filtration (particularly reverse osmosis-based filtration).

[0032] In one embodiment of the present invention, the first retentate stream and / or its derivatives (FRS) and at least the second retentate stream and / or its derivatives (SRS) are subjected to anaerobic digestion.

[0033] In this context, it should be emphasized that the first retentate stream and the second retentate stream can be directly subjected to anaerobically treatment or advantageously to anaerobically treatment after some intermediate treatment. In other words, the second retentate stream or the retentate from a further downstream filter (e.g. a nanofilter or an ultrafilter) can also be used to produce biogas and / or other fuels if it is considered cost-effective.

[0034] In one embodiment of the invention, the first retentate stream and / or derivatives thereof (FRS) are subjected to anaerobic digestion and at least the second retentate stream (SRS) is subjected to aerobic treatment.

[0035] In this context it should be emphasized that the first retentate stream FRS can be treated anaerobically, either directly or through additional treatment steps, to utilize the inherent energy of organic compounds. The second retentate stream SRS, and potentially the retentate stream from the filter downstream of the process, can be treated aerobically. In such a setup, the first retentate, preferably the largest and most important side stream of the wastewater input, can be reused for example as biogas and / or other fuels, while smaller side streams can be subjected to less energy efficient processes, but still keep the net energetics of the method / system attractive.

[0036] In one embodiment of the present invention, the organic compound content of the first retentate stream (FRS) is at least 25%, such as at least 50%, such as at least 75% by weight of the organic compounds of the wastewater input, and wherein the organic compound content of the reverse osmosis input stream (ROIS) is less than 1% by weight of the total reverse osmosis input stream (ROIS), such as less than 0.001%.

[0037] In one embodiment of the present invention, the chemical oxygen demand (COD) content of the wastewater input is 1 to 50 g / L, such as 2 to 20 g / L.

[0038] In one embodiment, the method can both create a side stream of organic compounds that can be used, for example, for biogas and / or other fuels, such as through anaerobic treatment, but at the same time create a relatively clean output from the final filtration step, i.e., a reverse osmosis filter. The clean water output from the final filtration step can be reused in a wastewater treatment process, or can be discharged.

[0039] Furthermore, by keeping the concentration of organic compounds in the reverse osmosis input stream low, fouling of the reverse osmosis filter membrane can be minimized.

[0040] In one embodiment, 100% of the particulate organic matter may be removed by the microfilter.

[0041] In one embodiment of the invention, a reverse osmosis input stream (ROIS) is established at least in part by filtering the first permeate stream using one or more additional filters.

[0042] In this context, the reverse osmosis input flow based on the first permeate stream means that the first permeate stream is filtered by reverse osmosis directly after the microfiltration step, i.e., without being filtered through an intermediate filter before entering the reverse osmosis membrane, or is usually filtered by reverse osmosis after one or more intermediate filtrations (e.g., nanofiltration and / or ultrafiltration).

[0043] In this case, the initial microfiltration will provide the majority of the organic material for organic compound energy recovery (e.g., biofuel production), and the remaining filter can be used to remove unwanted ions such as NH4+, SO4, Ca2+, and S2-, to an extent that allows the permeate from the reverse osmosis filtration to be clean enough for discharge or at least reuse.

[0044] In one embodiment of the present invention, nanofiltration is performed based on the first permeate stream (FPS) to obtain a second retentate stream (SRS) and a second permeate stream (SPS) comprising additional organic compounds.

[0045] In one embodiment of the present invention, based on the second permeate stream (SPS), the first permeate stream is filtered through one or more additional filtration units to provide a reverse osmosis input stream (ROIS).

[0046] In one embodiment of the invention, at least the first retentate stream (FRS) or a derivative thereof is used to produce biogas and / or other fuels.

[0047] In one embodiment of the invention, the wastewater input comprises effluent from a soaking step of a tanning process.

[0048] In one embodiment of the invention, the wastewater input comprises liming effluent from a tanning process.

[0049] In one embodiment of the invention, the wastewater input comprises deliming effluent from a tanning process.

[0050] In one embodiment of the invention, the wastewater input comprises bating effluent from a tanning process.

[0051] In one embodiment of the invention, the wastewater input comprises pickling effluent from a tanning process.

[0052] In one embodiment of the invention, the wastewater input comprises hide salt dilution water.

[0053] In one embodiment of the invention, the wastewater input comprises digestate centrate.

[0054] In one embodiment of the invention, said wastewater input comprises fibers removed from animal hides prior to said tanning process, and a pre-filter is applied to filter said fibers prior to said microfiltration.

[0055] In one embodiment of the invention, the wastewater input comprises effluent from a sammy step of a tanning process.

[0056] In one embodiment of the invention, the wastewater input comprises the effluent from the neutralization step of a tanning process.

[0057] In one embodiment of the invention, the effluents from the soaking and bating steps of the tanning process are combined.

[0058] In one embodiment of the invention, the effluent from the lime treatment step is treated separately.

[0059] In one embodiment of the invention, the effluent from the acid wash step is treated separately.

[0060] In one embodiment of the present invention, the first retentate stream (FRS) comprises organic compounds such as feces, blood, urine, oil, non-structural proteins, hyaluronic acid and / or keratin.

[0061] In one embodiment of the present invention, the first retentate stream (FRS) comprises inorganic compounds such as mud, soil, gravel and / or sand.

[0062] In one embodiment of the present invention, the second retentate stream (SRS) comprises organic molecules such as smaller proteins, peptides, amino acids, organic acids, multivalent ions such as calcium, magnesium, sulfate, phosphate and / or any combination thereof.

[0063] In one embodiment of the invention at least one of the retentate streams is fed back to the industrial process.

[0064] In the present context, the retentate stream is understood to be the relevant retentate obtained from one or more filters downstream of the microfilter.

[0065] In one embodiment of the invention at least one of the retentate streams is fed back into the pickling step of the tanning process.

[0066] In one embodiment of the invention, at least one of the permeate streams is fed back to the industrial process.

[0067] In one embodiment of the invention, at least one of said permeate streams is fed to a soaking step of a tanning process.

[0068] In one embodiment of the present invention, the microfilter is implemented using one or more cross-flow filter elements.

[0069] In one embodiment of the present invention, the pore size of the microfilter is between 5 nanometers and 2 micrometers, such as between 5 nanometers and 1 micrometer, such as between 5 nanometers and 200 nanometers, such as between 5 nanometers and 100 nanometers, such as between 5 nanometers and 60 nanometers, such as between 10 nanometers and 50 nanometers.

[0070] In one embodiment of the invention, the at least one further filter comprises an ultrafilter, and wherein the ultrafilter is realized by one or more cross-flow filter elements.

[0071] In one embodiment of the present invention, the pore size of the ultrafilter is between 0.1 nanometers and 2 micrometers.

[0072] In one embodiment of the invention, the at least one further filter comprises a nanofilter, and wherein the nanofilter is realized by one or more cross-flow membranes.

[0073] In one embodiment of the present invention, the pore size of the nanofilter is between 150 Da (Dalton) and 1000 Da.

[0074] In one embodiment of the present invention, the reverse osmosis filter is implemented with one or more cross-flow membranes.

[0075] The cross-flow filtration elements or membranes described above, when applied in connection with, for example, microfilters, ultrafilters, nanofilters and / or reverse osmosis filters, may be defined as filtration elements providing cross-flow filtration, also known as tangential flow filtration (TFF).

[0076] Cross-flow filtration differs from dead-end filtration in that the feed passes through the filter element, solids are trapped in the filter, and the filtrate is released at the other end. Cross-flow filtration gets its name because most of the feed flow passes tangentially across the filter surface, rather than into the filter. The main advantage of this is that the filter cake (which may clog the filter) is essentially washed away during the filtration process, thereby extending the operability time of the filtration unit. It can be a continuous process, unlike dead-end filtration, which is intermittent.

[0077] The main driving force of the cross-flow filtration process is the transmembrane pressure. Transmembrane pressure is a measure of the pressure difference between the two sides of the filter element.

[0078] In cross-flow filtration, the feed passes through the filter element at a positive pressure relative to the permeate side (tangentially). The proportion of material smaller than the pore size passes through the filter element as permeate or filtrate; the rest of the material is retained on the feed side of the filter element as retentate.

[0079] With cross-flow filtration, the tangential motion of the bulk of the fluid across the membrane causes particles captured on the filter surface to be wiped off. This means that cross-flow filters can operate continuously at relatively high solids loadings without clogging.

[0080] Some advantages of cross-flow filter elements in specific cascade applications include, but are not limited to:

[0081] -Achieve higher overall liquid removal rates by preventing filter cake formation

[0082] -Process feed remains in the form of a flowing slurry, suitable for further processing

[0083] -The solid content of the product slurry can vary within a wide range

[0084] -Can fractionate particles by size

[0085] -Tubular pinch effect

[0086] The filter elements associated with cross-flow filtration can be polymeric or ceramic, depending on the application. In specific embodiments, the principles of cross-flow filtration can be used for reverse osmosis, nanofiltration, ultrafiltration, and microfiltration.

[0087] In this context, some types of cross-flow filter elements can be improved in performance by, for example, applying backwashing. In backwashing, the transmembrane pressure is periodically reversed using an auxiliary pump so that the permeate flows back into the feed, thereby lifting the fouling layer from the membrane surface.

[0088] In this context, an advantageous method for increasing the industrial performance of wastewater filtration within the scope of the present invention is the use of so-called cleaning-in-place systems (CIP).

[0089] The CIP process may use cleaning agents, reactants such as acids and bases such as citric acid and sodium hydroxide (NaOH). In some membrane units, sodium hypochlorite (bleach) must be removed from the feed. Bleach will oxidize the membrane. Oxidation will degrade the performance of the filter elements to the point where they no longer operate at the rated rejection level and must be replaced. Bleach can be added to the sodium hydroxide CIP during the initial system startup to help disinfect the system before the spiral wound membrane is installed in the unit. Bleach can also be used with metal or ceramic filter elements because they tolerate sodium hypochlorite much better than spiral wound membranes. Bases and acids can also be used as primary CIP chemicals. Bases can remove organic foulants, while acids can remove minerals. Enzyme solutions are also used in some systems to help remove organic foulants from membrane units. pH and temperature are important to the CIP procedure. If the pH and temperature are too high, the membrane may degrade and flux performance will also be affected. If the pH and temperature are too low, the system will not be properly cleaned. Each application has different CIP requirements. Each membrane manufacturer has its own CIP process guidelines for its products.

[0090] Nevertheless, within the scope of the present invention, it may be advantageous to sterilize one or more filter elements of a microfilter, ultrafilter, nanofilter and / or reverse osmosis filter with hot water. The cleaning method and temperature must be adapted to the filter element used to avoid degradation of the filter element's performance or damage to the filter element.

[0091] In one embodiment of the present invention, the pore size of the reverse osmosis filter is less than 150 Da.

[0092] In one embodiment of the present invention, the first permeate stream (FPS) or its derivative is subjected to an antimicrobial treatment before the first permeate stream or its derivative is subjected to the reverse osmosis filtration through the reverse osmosis filter (ROF).

[0093] In the present invention, the reduction of the number of microorganisms at this stage of the process is preferably carried out without the use of chemical compounds or, for example, enzymes.

[0094] In one embodiment of the present invention, the first permeate stream (FPS) or its derivative is subjected to an antimicrobial treatment before being subjected to the reverse osmosis filtration through the reverse osmosis filter (ROF), and wherein the antimicrobial treatment is obtained by ultraviolet (UV) light.

[0095] Using UV disinfection, the cell walls of bacteria, viruses and protozoa can be penetrated, permanently changing the DNA of the microorganism. This effectively inactivates the microorganism, making it unable to infect and reproduce. As long as the cells cannot reproduce, they cannot cause any infection, thus killing bacteria and viruses.

[0096] UV disinfection has become the preferred water disinfection solution for inactivating and killing microorganisms, bacteria and viruses due to its many benefits, which can include:

[0097] Lower carbon footprint compared to alternative disinfection methods

[0098] Low maintenance, management and operating costs

[0099] - No hazardous chemicals involved (no residues, handling and storage)

[0100] - No by-products added during the process

[0101] - No changes in water properties such as pH and temperature

[0102] "Instant" processing, meaning very short processing time

[0103] Safe and simple implementation.

[0104] In one embodiment of the present invention, the first permeate stream (FPS) or its derivative is subjected to antimicrobial treatment before the reverse osmosis filtration of the first permeate stream or its derivative is performed through the reverse osmosis filter (ROF), and wherein the reverse osmosis permeate stream (ROPS) is further subjected to antimicrobial treatment.

[0105] In one embodiment of the present invention, the reverse osmosis permeate stream (ROPS) is subjected to an antimicrobial treatment.

[0106] In one embodiment of the present invention, the reverse osmosis permeate stream and / or the reverse osmosis retentate stream is subjected to antimicrobial treatment by chemical treatment with chlorine, hydrogen peroxide and / or ozone.

[0107] By chemically treating the reusable permeate stream, the bacterial and viral content can be reduced or removed.

[0108] In one embodiment of the present invention, the reverse osmosis permeate stream and / or the reverse osmosis retentate stream is subjected to UV radiation and / or filtered through an activated carbon filter.

[0109] By using UV (UV: Ultraviolet) radiation, the content of undesirable microorganisms can be reduced or eliminated.

[0110] In one embodiment of the invention, any of the antimicrobial treatments are variably turned on or off depending on the level of microorganisms in a water stream associated with the system.

[0111] In one embodiment of the invention, at least one permeate stream is fed back for use as a diluted version of the input wastewater in an industrial process.

[0112] In one embodiment of the present invention, the tannery wastewater is further filtered with a pre-filter before applying the at least one microfilter.

[0113] In one embodiment of the present invention, before applying the at least one microfilter, the tanning wastewater is further filtered with a pre-filter to remove components in the wastewater that may not be effectively removed by the at least one microfilter, such as solids, hair, etc., which are part of the wastewater subjected to filtration according to the present invention.

[0114] In one embodiment of the present invention, the tannery wastewater is not subjected to aerobic pretreatment before the microfiltration.

[0115] In one embodiment of the present invention, the microfilter is subjected to cleaning in place (CIP), wherein the microfilter is cleaned at least once every 7 days, such as at least once every 6 days, such as at least once every 5 days, such as at least once every 4 days, such as at least once every 3 days, such as at least once every 2 days, such as at least once every day.

[0116] The present invention also relates to a wastewater treatment system (WWTS), comprising at least one wastewater system input (WSI), the wastewater system input (WSI) being fluidically connected to a microfilter (MF), the microfilter (MF) being fluidically connected to a conduit (CON2) for directing a first retentate stream (FRS) or a derivative thereof to a system output (SOI), the microfilter (MF) being further fluidly connected to a conduit for directing at least one substream of a first permeate stream (FPS) via one or more intermediate filters (NF) to at least one reverse osmosis filter (ROF), the reverse osmosis filter (ROF) providing at least one reverse osmosis permeate stream to a system output (SO4).

[0117] In one embodiment of the invention, the reverse osmosis filter (ROF) provides at least one reverse osmosis retentate stream to the system output (SO3).

[0118] In one embodiment of the invention, the microfilter (MF) is fluidly connected to a conduit for directing a substream of the first permeate stream (FPS) or a derivative thereof to the system output (SO2) via at least one intermediate filter (NF).

[0119] In this context, the intermediate filter may typically be a nanofilter or an ultrafilter.

[0120] In one embodiment of the present invention, the first retentate stream (FRS) or at least a side stream thereof is directed to a system output (SOI) via one or more filters.

[0121] In one embodiment of the present invention, the tannery wastewater treatment system (WWTS) operates according to the method for filtering tannery wastewater.

[0122] In embodiments, it may be advantageous to eliminate undesirable compounds that may negatively impact subsequent anaerobic processing based on the first retentate stream. BRIEF DESCRIPTION OF THE DRAWINGS

[0123] The present invention will be described below with reference to the accompanying drawings, in which

[0124] Figure 1a and 1b shows how to obtain effluents from different steps of the tanning process,

[0125] Figure 2 The principle of the water treatment system according to the embodiment of the present invention is shown.

[0126] Figure 3 The principle of a wastewater treatment system for treating tanning process effluent according to an embodiment of the present invention is shown, and

[0127] Figure 4 An implementation of a microfilter suitable for use with embodiments of the present invention is shown. DETAILED DESCRIPTION

[0128] Figure 1a An industrial process is shown in which the water treatment system and method of the present invention may be implemented.

[0129] The illustrated process is a tanning process comprising the following steps: soaking step, SOA, liming step LIM, deliming step, DE-LIM, bating / pickling step BA / PI, tanning step, TAN, dyeing step, DYI and fatliquoring step, FAL. The process itself is well known in the art and may comprise further steps depending on the source material, e.g. leather type, mycelium type, etc. According to different tanning process methods, some of the steps may also be split, repeated and / or switched, and some steps may be omitted and / or significantly modified depending on the application.

[0130] An example of a step that can be split is the softening / pickling step, which can typically be accomplished in separate softening and pickling steps (not shown).

[0131] In some applications, it may not be attractive to treat wastewater substreams from tanning steps, dyeing steps and fatliquoring steps.

[0132] Other suitable wastewater substreams may originate from the fiber removal step of the tanning process, the wetting step of the tanning process and / or the neutralization step of the tanning process.Other substreams may include input streams obtained prior to the tanning process, for example in the form of digestion liquor.

[0133] Another step that can be added is a processing step before the tanning process where the salt is scraped off the hides.

[0134] With this in mind, the tanning process steps shown and their sequence may be performed in the order shown or modified, with appropriate definitions.

[0135] Again, regardless of the order used, each individual tanning process step may result in effluent.

[0136] As shown in the figure, each step of the process can be filtered using a cascade filter device FILT according to the provisions of the present invention. Filtration can result in multiple side streams, which can be clean and reusable water (REU), a stream suitable for high-value utilization (VAL) and / or a stream (WAS) subjected to further treatment / degradation. Reusable side streams are water streams with extremely low dissolved solids content and not containing suspended solids, and are therefore suitable for reuse. Fluids suitable for high-value utilization can be fluids with high energy content, high salinity content or other molecules of interest (such as ammonia or phosphate) content. Therefore, high-value utilization side streams can be used as feedback streams of industrial processes (such as tanning processes) or for energy recovery or for synthesizing specific molecules of interest. Finally, the side stream subjected to degradation can include a residual compound stream that cannot be further utilized, and can therefore be degraded by, for example, aerobic treatment.

[0137] The wastewater treatment according to the present invention will be described in more detail in the following figures.

[0138] Figure lb illustrates the tanning process shown above, but now combining some of the tanning process steps to obtain a side stream that meets the desired results for effluent treatment.

[0139] In this embodiment, the effluents from the soaking step SOA and the liming step LIM are combined into one process, and the combined effluents are treated to produce clean water REU, value-added utilization side stream VAL and waste side stream WAS, which are obtained by the combined tanning process steps of soaking SOA and liming LIM.

[0140] In another embodiment, the soaking step SOA and the liming step LIM are isolated from each other and the respective effluents are treated separately. An advantage may be that mixing the effluents of the soaking and liming treatment steps may result in a decrease in pH, leading to the release of harmful gases.

[0141] Likewise, according to the invention, the effluents from the deliming step DE-LIM, the bating / pickling step BA / PI and the tanning step TAN are also combined for treatment, and finally the effluents from the dyeing step DYI and the fatliquoring step FAL are combined.

[0142] Several other combinations may be applied within the scope of the present invention, taking into account the compounds of the corresponding effluents and the potential for high value utilization of each combination.

[0143] Non-limiting examples include: hide salt dilution water, effluents from the soaking step and the bating step, effluents from the liming and deliming steps, effluents from the pickling step, effluents from the digester liquor obtained before the tanning process, combined effluents from the fiber removal step, the wetting step and the neutralization step, or a "one-pot" of all or most of the sub-streams of the tanning process.

[0144] Figure 2 The diagram illustrates the principles of a wastewater treatment system WWTS and a wastewater treatment method according to an embodiment of the present invention.

[0145] The wastewater treatment system WWTS comprises a wastewater system input WSI, which is fluidically connected to a wastewater source, here a wastewater tank WWT. Circulation in the wastewater tank WWT is achieved by a fluid pump FP0.

[0146] The system input WSI directs the input flow IS to the microfilter MF via conduit CONI and fluid pumps FP1A and FP1B.

[0147] The microfilter MF may be a tubular membrane filter, a flat membrane filter, a hollow fiber filter, a spinning disk filter or the like.

[0148] The pore size can generally be in the range of 5 nm to 60 nm. In this embodiment, the pore size is selected to be 20 nm.

[0149] The microfilter MF separates the input stream IS into a first retentate stream FRS and a first permeate stream FPS. The first retentate stream FRS is directed to the intermediate bulk container IBC1 via the conduit CON2 through the back pressure valve BPV1. From the intermediate bulk container IBC1, the first system output SOI can be released.

[0150] The recirculation loop flow FLSA is directed from the first retentate stream FRS back to the microfilter MF by means of a fluid pump FP1B via conduit CON1A.

[0151] The first permeate stream FPS is guided to the nanofilter NF via the conduit CON3 by means of two fluid pumps FP2 and FP3.

[0152] The nanofilter NF separates the first permeate stream FPS into a second retentate stream SRS and a second permeate stream SPS.

[0153] The recirculation loop flow FLSB is directed from the second retentate stream SRS back to the nanofilter NF via the conduit CON5 through the fluid pump FP3.

[0154] The second retentate stream SRS is led through the back pressure valve BPV2 via conduit CON4 to the intermediate bulk container IBC2. From the intermediate bulk container IBC2, the second system output SO2 can be released.

[0155] The second permeate stream SPS is directed to the reverse osmosis filter ROF via conduit CON6 through fluid pumps FP4A and FP4B. The above-described feedback arrangement is used to reduce the water content of the second retentate stream SRS to an acceptable level.

[0156] The reverse osmosis filter ROF separates the reverse osmosis input flow ROIS obtained from the second permeate flow SPS and the recirculation loop flow FLSC into a reverse osmosis retentate flow RORS and a reverse osmosis permeate flow ROPS. The reverse osmosis retentate flow RORS is led to the intermediate bulk container IBC3 via the pipeline CON7 through the back pressure valve BPV3. From the intermediate bulk container IBC3, the third system output SO3 can be released.

[0157] The recirculation loop flow FLSC is directed from the reverse osmosis retentate stream RORS back to the reverse osmosis filter ROF by means of a fluid pump FP4B via conduit CON6A.

[0158] From the intermediate bulk container IBC3, a third system output SO3 can be released. Reverse osmosis permeate ROPS flows from the reverse osmosis filter output to the intermediate bulk container IBC4 via conduit CON8. From the intermediate bulk container IBC4, a fourth system output SO4 can be released.

[0159] It is worth noting that the above system outputs SO1-SO4 are associated with corresponding intermediate bulk containers in this context. If desired, some or all side streams can also be directed directly to the system outputs.

[0160] The system output SOI may, for example, form a water-based stream of carbon compounds, which may be subjected to anaerobic treatment in order to produce biogas via a biogas reactor (not shown).

[0161] The system output SO2 may, for example, also include carbon compounds and other compounds, such as ions. The output may be further processed into valuable products, or may be subjected to biological treatment, such as aerobic treatment.

[0162] The SO3 output of the system should generally have a relatively low carbon compound content, but may include salts, metals, etc., which can be reused in industrial processes, such as feedback to tanning process steps. The SO3 output of the system can be subjected to subsequent treatment. See elsewhere in this application for optional post-treatment types.

[0163] The system output SO4 can provide a "cleanest" side stream, which can be reused in an industrial process, for example.

[0164] It should also be noted that the use of an initial microfilter serves the purpose of protecting subsequent filter elements from fouling, thereby reducing the need for maintenance of these downstream filter elements.

[0165] The filters shown above, in particular the microfilter MF, can be cleaned of dirt by known measures, for example by cleaning in place (CIP). However, it is worth noting that the method / system shown facilitates relatively low frequency cleaning of the filter elements downstream of the microfilter (MF).

[0166] The microfilter MF can also be back-flushed with water to reduce CIP costs.

[0167] The filter elements employed in the system are typically cross-flow membranes to suit the industrial process with the associated throughput / acceptable maintenance frequency.

[0168] It is worth noting that, in addition to organic compounds in the first retentate stream FRS, the microfilter MF can also sort other substances other than organic compounds (such as all substances larger than, for example, 60 nanometers, such as hair, solid particles, sand, clay, etc.) into the retentate.

[0169] Figure 3 An embodiment specifically related to the treatment of soaking / baing effluent in a tanning process is illustrated.

[0170] Thus, the first waste stream WAI is fed to the microfilter MF which separates the waste stream into a first permeate stream FPS and a first retentate stream FRS.

[0171] The first retentate stream FRS and the second waste stream WA2 are fed to an anaerobic treatment system ATS comprising a biogas reactor (not shown). The anaerobic treatment system provides a biogas output BG, a waste output WAO, a fertilizer output FERT and a further output AT which may be subjected to aerobic treatment.

[0172] Turning to the first permeate stream FPS, it is directed to a nanofilter NF, which again divides the first permeate stream into two side streams, namely a second permeate stream SPS and a second retentate stream SRS. The second retentate stream SRS is fed to the nanofilter output NFO. Subsequently, the second retentate stream can be subjected to an aerobic treatment.

[0173] The second permeate stream SPS is directed via a further filtration unit RO, producing a permeate side stream PORO of clean water and a retentate output RORO delivering a side stream comprising salts. In the embodiment shown, the retentate output can be fed back to the tanning process step and used with the pickling step.

[0174] The filtering device RO providing the above output may include a cascade carbon filter CF, a seawater reverse osmosis filter SWRO and a saltwater reverse osmosis filter BWRO. In addition, the permeate may then be subjected to UV treatment through a UV filter. The order of filters CF, SWRO and BWRO and UV treatment may vary within the scope of the invention. Some filters may also be omitted, or more filters may be added.

[0175] The first side stream in this embodiment would be the effluent from the soaking / bating step of the tanning process, e.g. Figure 1a shown.

[0176] The second waste stream WA2 comprises a wastewater stream having a relatively high concentration of proteins and optionally other organic compounds.The second wastewater stream WA2 may for example be based on scrapings originating from mechanical treatment of the hides prior to the tanning step.

[0177] It should be noted that the pre-processing and / or post-processing may be related to FIG. 1A , FIG. 1B , Figure 2 and Figure 3 Any of the above embodiments may be used in conjunction or advantageously. No pre-processing and / or post-processing is shown in any of the drawings.

[0178] The pre-treatment(s) and / or post-treatment(s) may be adapted to the particular industrial process associated with which the wastewater was generated. Figure 3 The embodiments are specifically directed to the treatment of wastewater from a tanning process, combined with an input of wastewater from residues of mechanical processing of hides prior to the tanning process. For different types of industrial process waste streams, the pore size of the applied filter may vary, in particular for microfilters.

[0179] Related pre-treatment may include, but is not limited to, pre-filtration with a filter / mesh having a pore size / opening larger than the initial microfilter MF or, for example, a cyclone filter, to help remove unwanted larger particles.

[0180] Another type of suitable pretreatment may include chemical / physical treatments such as flocculation, coagulation, and / or pH adjustment such as acid treatment and ion exchange.

[0181] Related types of post-treatment may include, but are not limited to, UV irradiation, filtration through an activated carbon filter, chemical treatment (e.g., chlorine, ozone, hydrogen peroxide). The latter three treatments are preferably performed on the retentate stream and / or the permeate stream from the reverse osmosis filter, while treatment by UV irradiation and / or activated carbon filter may be performed, for example, on a substream before the reverse osmosis filter (e.g., the input stream of the reverse osmosis filter). A further type of post-treatment may be an ammonia removal step, such as an ion exchange treatment.

[0182] In addition, FIG. 1A, FIG. 1B, Figure 2 and Figure 3 The above-described embodiments may advantageously include one or more additional buffer tanks (not shown) to ensure efficient performance of the system.

[0183] In addition, Figure 1A, Figure 1B, Figure 2 and Figure 3 The above-described embodiment in may advantageously comprise a biological treatment (eg aerobic treatment) of the first permeate stream or further permeate streams downstream of the microfilter MF in order to reduce small residues of undesirable compounds.

[0184] Figure 4 A microfilter MF is shown having four different microfilter subunits MFI, MF2, MF3 and MF4 having the same filtering capacity. The microfilter input flow MFI enters the microfilter MF, whereby it is divided into four substreams of equal size. Each substream is then directed to a microfilter subunit (MFI, MF2, MF3 or MF4) through which it is filtered and divided into a retentate flow and a permeate flow. Four retentate flows are collected from each microfilter subunit and combined into one microfilter retentate MFR and leave the microfilter via an output. Similarly, four permeate flows are collected from each microfilter subunit and combined into one microfilter permeate MFP and leave the microfilter through another output. By having multiple microfilters (here a four-unit microfilter), cleaning and maintenance can be performed by a cleaning in place (CIP) procedure, where one microfiltration subunit can be shut down and cleaned at a time. This can help achieve a filtering capacity of 75% or more, so that the filtration flow can continue uninterrupted during maintenance.

[0185] If in Figure 2 or Figure 3 By applying the parallel microfilters MF shown in the embodiment of FIG. 1 , the efficiency of the entire system can be kept relatively high because the microfilters can remove compounds (retentates) that would otherwise cause fouling of downstream filters.

[0186] The parallel membrane concept as described above can be applied not only to microfiltration but also to other filtration elements, such as downstream nanofilters and / or reverse osmosis filters if required.

Claims

1. A method for filtering tannery wastewater, the method comprising the following steps: microfiltering a wastewater input of said wastewater in at least one microfilter (MF) thereby separating said wastewater input into a first retentate stream (FRS) comprising organic compounds, and a first permeate stream (FPS), establishing a reverse osmosis input stream (ROIS) based on the first permeate stream (FPS) or a derivative thereof, A reverse osmosis filtration is performed on the reverse osmosis input stream (ROIS) through a reverse osmosis filter (ROF) to establish a reverse osmosis retentate stream (RORS) and a reverse osmosis permeate stream (ROPS), wherein the wastewater comprises one or more side streams of the tanning process.

2. The method for filtering wastewater according to claim 1, wherein: The wastewater comprises a subset of one or more side streams of the tanning process.

3. The method for filtering wastewater according to claim 1 or 2, wherein: The wastewater is provided based on the effluent from one or more tanning process steps.

4. The method for filtering wastewater according to any one of claims 1 to 3, wherein: The wastewater is the effluent from a tanning process step.

5. The method for filtering wastewater according to any one of claims 1 to 4, wherein: The wastewater is the effluent from two or more tanning process steps.

6. The method for filtering wastewater according to any one of claims 1 to 5, wherein: The effluent provides one or more tanning process steps of the self-tanning process, such as soaking SOA, liming LIM, deliming DE-LIM, bating, pickling, tanning, TAN, dyeing, DYI and fatliquoring FAL.

7. The method for filtering wastewater according to any one of claims 1 to 6, wherein: The first retentate stream (FRS) has an organic compound content of at least 25%, such as at least 50%, such as at least 75% by weight of the wastewater input.

8. The method for filtering wastewater according to any one of claims 1 to 7, wherein: The first retentate stream and / or derivatives thereof (FRS) are subjected to anaerobic digestion.

9. The method for filtering wastewater according to any one of claims 1 to 8, wherein: The first retentate stream and / or its derivatives (FRS) are subjected to anaerobic digestion and thereby converted into biogas and / or other fuels.

10. The method for filtering wastewater according to any one of claims 1 to 9, wherein: The first retentate stream and / or derivatives thereof (FRS) and at least a second retentate stream and / or derivatives thereof (SRS) are subjected to anaerobic digestion.

11. The method for filtering wastewater according to any one of claims 1 to 10, wherein: The first retentate stream and / or derivatives thereof (FRS) are subjected to anaerobic digestion and at least the second retentate stream (SRS) is subjected to aerobic treatment.

12. The method for filtering wastewater according to any one of claims 1 to 11, wherein: The organic compound content of the first retentate stream (FRS) is at least 25%, such as at least 50%, such as at least 75% by weight of the organic compounds of the wastewater input, and the organic compound content of the reverse osmosis input stream (ROIS) is less than 1% by weight of the total reverse osmosis input stream (ROIS), such as less than 0.001%.

13. The method for filtering wastewater according to any one of claims 1 to 12, wherein: A reverse osmosis input stream (ROIS) is established at least in part by filtering the first permeate stream through one or more additional filters.

14. The method for filtering wastewater according to any one of claims 1 to 13, wherein: Nanofiltration is performed on the first permeate stream (FPS), thereby obtaining a second retentate stream (SRS) comprising additional organic compounds, and a second permeate stream (SPS).

15. The method for filtering wastewater according to any one of claims 1 to 14, wherein the first permeate stream is filtered through one or more additional filtration units based on the second permeate stream (SPS) to provide a reverse osmosis input stream (ROIS).

16. The method for filtering wastewater according to any one of claims 1 to 15, wherein: At least the first retentate stream (FRS) or a derivative thereof is used for the production of biogas and / or other biofuels.

17. The method for filtering wastewater according to any one of claims 1 to 16, wherein: The wastewater input comprises the effluent from the soaking step of the tanning process.

18. The method for filtering wastewater according to any one of claims 1 to 17, wherein: The wastewater input comprises liming effluent from a tanning process.

19. The method for filtering wastewater according to any one of claims 1 to 18, wherein: The wastewater input comprises deliming effluent from a tanning process and / or bating effluent from a tanning process.

20. The method for filtering wastewater according to any one of claims 1 to 19, wherein: The wastewater input comprises pickling effluent from a tanning process.

21. The method for filtering wastewater according to any one of claims 1 to 20, wherein: The wastewater input includes hide salt dilution water.

22. The method for filtering wastewater according to any one of claims 1 to 21, wherein: The wastewater input includes digestate.

23. The method for filtering wastewater according to any one of claims 1 to 22, wherein: The wastewater input comprises fibers removed from animal hides prior to the tanning process, and wherein the fibers are filtered using a pre-filter prior to the microfiltration.

24. The method for filtering wastewater according to any one of claims 1 to 23, wherein: The wastewater input comprises the effluent from the wet step of the tanning process.

25. The method for filtering wastewater according to any one of claims 1 to 24, wherein: The wastewater input comprises the effluent from the neutralization step of the tanning process.

26. The method for filtering wastewater according to any one of claims 1 to 25, wherein: The effluents from the soaking and bating steps of the tanning process are combined.

27. The method for filtering wastewater according to any one of claims 1 to 26, wherein: The effluent from the liming step is treated separately.

28. The method for filtering wastewater according to any one of claims 1 to 27, wherein: The effluent from the acid wash step is treated separately.

29. The method for filtering wastewater according to any one of claims 1 to 28, wherein: The first retentate stream (FRS) comprises organic compounds, such as feces, blood, urine, oil, non-structural proteins, hyaluronic acid and / or keratin.

30. The method for filtering wastewater according to any one of claims 1 to 29, wherein: The first retentate stream (FRS) comprises inorganic compounds, such as mud, soil, gravel and / or sand.

31. The method for filtering wastewater according to any one of claims 1 to 30, wherein: The second retentate stream (SRS) includes organic molecules such as smaller proteins, peptides, amino acids, organic acids, multivalent ions such as calcium, magnesium, sulfate, phosphate and / or any combination thereof.

32. The method for filtering wastewater according to any one of claims 1 to 31, wherein: At least one of the retentate streams is fed back to the industrial process.

33. The method for filtering wastewater according to any one of claims 1 to 32, wherein: At least one of the retentate streams is fed back to the pickling step of the tanning process.

34. The method for filtering wastewater according to any one of claims 1 to 33, wherein: The at least one permeate stream is fed back to the industrial process.

35. The method for filtering wastewater according to any one of claims 1 to 34, wherein: At least one of the permeate streams is fed back to the soaking step of the tanning process.

36. The method for filtering wastewater according to any one of claims 1 to 35, wherein: The microfilter is implemented using one or more cross-flow filter elements.

37. The method for filtering wastewater according to any one of claims 1 to 36, wherein: The pore size of the microfilter is between 5 nm and 2 microns, such as between 5 nm and 1 micron, such as between 5 nm and 200 nm, such as between 5 nm and 100 nm, such as between 5 nm and 60 nm, such as between 10 nm and 50 nm.

38. The method for filtering wastewater according to any one of claims 1 to 37, wherein: The at least one further filter comprises an ultrafilter and wherein the ultrafilter is implemented using one or more cross-flow filter elements.

39. The method for filtering wastewater according to claim 38, wherein: The pore size of the ultrafilter is between 0.1 nm and 2 microns.

40. The method for filtering wastewater according to any one of claims 1 to 39, wherein: At least one additional filter comprises a nanofilter, and wherein the nanofilter is implemented using one or more cross-flow membranes.

41. The method for filtering wastewater according to claim 40, wherein: The pore size of the nanofilter is between 150 Da (Dalton) and 1000 Da.

42. The method for filtering wastewater according to any one of claims 1 to 41, wherein: The reverse osmosis filter is implemented with one or more cross-flow membranes.

43. The method for filtering wastewater according to any one of claims 1 to 42, wherein: The pore size of the reverse osmosis filter is less than 150 Da.

44. A method for filtering wastewater according to any one of claims 1 to 43, in, Before the reverse osmosis filtration of the first permeate stream or the derivative thereof through the reverse osmosis filter (ROF), the first permeate stream (FPS) or the derivative thereof is subjected to an antimicrobial treatment.

45. The method for filtering wastewater according to any one of claims 1 to 44, wherein: Prior to said reverse osmosis filtration of said first permeate stream (FPS) or a derivative thereof through said reverse osmosis filter (ROF), said first permeate stream (FPS) or a derivative thereof is subjected to an antimicrobial treatment, and wherein said antimicrobial treatment is obtained by ultraviolet (UV) light.

46. ​​The method for filtering wastewater according to any one of claims 1 to 45, wherein: Prior to the reverse osmosis filtration of the first permeate stream or a derivative thereof through the reverse osmosis filter (ROF), the first permeate stream (FPS) or a derivative thereof is subjected to an antimicrobial treatment, and wherein the reverse osmosis permeate stream (ROPS) is further subjected to an antimicrobial treatment.

47. The method for filtering wastewater according to any one of claims 1 to 46, wherein: The reverse osmosis permeate stream (ROPS) is subjected to antimicrobial treatment.

48. The method for filtering wastewater according to any one of claims 1 to 47, wherein: The reverse osmosis permeate stream and / or the reverse osmosis retentate stream is subjected to antimicrobial treatment by chemical treatment with chlorine, hydrogen peroxide and / or ozone.

49. The method for filtering wastewater according to any one of claims 1 to 48, wherein: The reverse osmosis permeate stream and / or the reverse osmosis retentate stream are UV irradiated and / or subjected to filtration through an activated carbon filter.

50. The method for filtering wastewater according to any one of claims 1 to 49, wherein: Any such antimicrobial treatment can be variably turned on or off depending on the level of microorganisms in the system's associated water stream.

51. The method for filtering wastewater according to any one of claims 1 to 50, wherein: At least one permeate stream is fed back for use as a diluted version of the input wastewater in the industrial process.

52. The method for filtering wastewater according to any one of claims 1 to 51, wherein: Prior to applying the at least one microfilter, the tannery wastewater is further filtered using a pre-filter.

53. The method for filtering wastewater according to any one of claims 1 to 52, wherein: Prior to applying the at least one microfilter, the tanning wastewater is further filtered with a prefilter to remove components in the wastewater that may not be effectively removed by the at least one microfilter, such as solids, hair, etc., which are part of the wastewater subjected to filtration according to the present invention.

54. The method for filtering wastewater according to any one of claims 1 to 53, wherein: The tannery wastewater was not subjected to aerobic pretreatment prior to the microfiltration.

55. The method for filtering wastewater according to any one of claims 1 to 54, wherein: The microfilter is subjected to cleaning in place (CIP), and wherein the microfilter is cleaned at least once every 7 days, such as at least once every 6 days, such as at least once every 5 days, such as at least once every 4 days, such as at least once every 3 days, such as at least once every 2 days, such as at least once every day.

56. The method for filtering wastewater according to any one of claims 1 to 55, wherein: The wastewater input may have a chemical oxygen demand (COD) content of 1 to 50 g / L, such as 2 to 20 g / L.

57. A tannery wastewater treatment system (WWTS) comprising at least one wastewater system input (WSI), said wastewater system input (WSI) being fluidly connected to a microfilter (MF), The microfilter (MF) is fluidly connected to a conduit (CON2) for directing the first retentate stream (FRS) or a derivative thereof to a system output (SOI), and further, The microfilter (MF) is also fluidly connected to a conduit for directing at least a side stream of the first permeate stream (FPS) to at least one reverse osmosis filter (ROF) via one or more intermediate filters (NF), The reverse osmosis filter (ROF) provides at least one reverse osmosis permeate stream to a system output (SO4).

58. The tannery wastewater treatment system (WWTS) of claim 57, wherein: The reverse osmosis filter (ROF) provides at least one reverse osmosis retentate stream to the system output (SO3).

59. The tannery wastewater treatment system (WWTS) according to claim 57 or 58, wherein: The microfilter (MF) is fluidly connected to a conduit for directing a substream of the first permeate stream (FPS) or a derivative thereof to a system output (SO2) via at least one intermediate filter (NF).

60. The tannery wastewater treatment system (WWTS) according to any one of claims 57 to 59, wherein: The first retentate stream (FRS) or at least one side stream thereof is directed to a system output (SO1) via one or more filters.

61. A tannery wastewater treatment system (WWTS) as claimed in any one of claims 57 to 60 and operated in accordance with any one of claims 1 to 56.

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