METHOD FOR THE BIOLOGICAL TREATMENT OF WASTEWATER

Abstract

A process, biological reactor, and installation for the biological treatment of wastewater comprising organic matter or matter assimilable by microorganisms in a mixed reactor, forming a complete mixture. Abstract figure: Figure 3

Description

Title of the invention: METHOD FOR THE BIOLOGICAL TREATMENT OF WASTEWATER

[0001] The present invention relates to a process for the biological treatment of wastewater, to a biological reactor and to an installation both enabling the implementation of this process.

[0002] A biological treatment allows the treatment of wastewater containing biologically degradable compounds using activated sludge containing microorganisms. The activated sludge is formed by microorganisms assembled into loose flocs floating freely in the water, called bacterial flocs.

[0003] During treatment, microorganisms, which are mostly bacteria, will consume carbon, nitrogen and phosphorus that are present in wastewater.

[0004] To enable this consumption of carbon, nitrogen, and phosphorus by microorganisms, the treatment conditions alternate between anaerobic and aerobic conditions. Indeed, this alternation between anaerobic, aerobic, and anoxic conditions allows for the simultaneous achievement of dephosphatation, nitrification (transformation of ammonium into nitrites and transformation of nitrites into nitrates), and denitrification (transformation of nitrites and nitrates into nitrogen).

[0005] Unfortunately, in the event of proliferation of filamentous bacteria, these bacterial flocs do not allow for the discharge of quality treated water because they can end up in the treated water and require sometimes aggressive treatments such as chlorine to prevent their proliferation.

[0006] The prior art document WO2004024638, which discloses a process for the biological treatment of wastewater containing organic matter or matter assimilable by microorganisms, is well known, comprising the steps of:

[0007] a first supply of wastewater under anaerobic conditions to at least one reactor called a biological reactor comprising an upper zone, a lower zone and a central zone, said at least one biological reactor comprising a sludge supplied with microorganisms,

[0008] a mixture of said wastewater with said sludge under anaerobic conditions in said at least one biological reactor, forming a suspension of solid matter in an aqueous phase,

[0009] Initiating aeration of said suspension of solids in the aqueous phase by injecting gas into said at least one biological reactor, obtaining a sufficient quantity of dissolved oxygen to oxidize 50 to 100% of the organic matter and 50 to 100% mineral matter,

[0010] a continuation of said mixing of said wastewater with said sludge under aerobic conditions or alternately under aerobic and anaerobic conditions in said at least one biological reactor forming the suspension of solid matter in the aqueous phase,

[0011] a settling of said sludge with obtaining (i) treated water formed from said wastewater substantially depleted in organic matter or matter assimilable by residual microorganisms and possibly containing a first part of microorganisms and (ii) a sludge bed formed from said organic matter or matter assimilable by residual microorganisms and a second part of microorganisms,

[0012] a withdrawal of at least a part of said treated water to form a treated water discharge.

[0013] In practice, a feast-famine regime is implemented in one or more biological reactors. The biological reactor is fed with wastewater mixed with granular sludge, also called sludge granules, which contains microorganisms such as bacteria. This mixture forms a suspension of solid matter comprising the sludge, microorganisms, organic matter, or matter assimilable by microorganisms in an aqueous phase. The feast-famine regime involves alternating periods of feeding and feeding.

[0014] Under anaerobic conditions, the feeding phase is initiated which allows microorganisms to feed on organic matter but also on matter assimilable by microorganisms such as matter based on phosphorus or nitrogen.

[0015] Next, the suspension of solid matter in the aqueous phase is aerated by the injection of a gas which makes it possible to obtain a quantity of dissolved oxygen sufficient to oxidize 50 to 100% of the organic matter and 50 to 100% of the mineral matter to form the aerobic conditions.

[0016] Under aerobic conditions, the starvation phase begins, during which the microorganisms have already consumed organic matter or matter assimilable by microorganisms. When aerobic conditions are established, the feeding phase ends at the beginning of said aerobic conditions. Therefore, there is a residual portion of the feeding phase under aerobic conditions before the starvation phase begins.

[0017] Under aerobic conditions, the concentration of oxygen present in said at least one biological reactor is from 1 mg / 1 to 2.5 mg / 1.

[0018] Sludge settling is then carried out (during which the biological reactor is no longer mixed) and allows, firstly, treated water to be obtained, consisting of wastewater substantially depleted of residual organic matter or matter assimilable by microorganisms and possibly containing a first portion of microorganisms and, secondly, a sludge bed consisting of said residual organic matter or matter assimilable by microorganisms and a second part of microorganisms.

[0019] This decantation is followed by the withdrawal of at least part of said treated water, which forms a discharge of treated water outside the biological reactor.

[0020] Document WO2004024638 describes how the wastewater feed to the reactor is slow and occurs through the lower section. Furthermore, the document also describes how the sludge settling rate is greater than 10 m / h and that this value is representative of high-quality granular sludge.

[0021] Unfortunately, this process has the drawback of depending on the geometry of the reactor in which it is carried out. Indeed, it is implemented by the formation of a plug flow within the reactor. Consequently, according to this document, the space is used to implement the various stages of the process. Furthermore, to obtain high-quality treated water, an additional filtration stage is performed after the biological treatment of the water.

[0022] To overcome these drawbacks, the present invention provides a process which allows water to be treated in reactors or wastewater treatment plant installations while allowing energy savings as well as the treatment of a larger pollutant load while being adaptable to pre-existing installations.

[0023] More particularly, the invention provides a process as described above, characterized in that said at least one reactor called a biological reactor is a fully mixed reactor equipped with stirring means so as to form a complete mixture and in that the settling of said sludge is carried out at a settling rate of solids in the aqueous phase of between 1.2 and 5 m / h.

[0024] By the terms "integral mixing reactor", according to the invention, a biological reactor which has stirring means sized to form a so-called "complete" mixture in the biological reactor, so that all areas of the biological reactor undergo stirring, i.e. a biological reactor whose contents have at all points relatively identical concentrations of microorganisms, dissolved oxygen and organic matter or matter assimilable by microorganisms (minimization of dead zones).

[0025] Although it is generally prohibited in granular sludge processes to use integrally mixed reactors, the present invention has made it possible to obtain an optimal wastewater treatment in which energy savings are achieved, which allows the treatment of a large pollutant load while being adaptable to pre-existing installations, and therefore independently of the geometry of the biological reactor.

[0026] Indeed, the formation of a complete mixture in the biological reactor generally favors a population of filamentous bacteria, considered incompatible with granular sludge treatment processes and often considered to require one or more downstream steps to obtain "clean" water However, according to the present invention, it has been shown that an appropriate alternation of anaerobic / aerobic conditions, in combination with thorough mixing and control of the settling rate between 1.2 m / h and 5 m / h, together made it possible to achieve an equilibrium between a population of granular bacteria and a population of filamentous bacteria to form granular sludge or granular sludge with a population of filamentous bacteria.

[0027] Granular sludge or granular sludge with a population of filamentous bacteria provides energy through its metabolism. Indeed, each granule comprises an anaerobic zone and an aerobic zone, allowing each granule to act as a "mini wastewater treatment plant." Granular sludge with a population of filamentous bacteria consists of sludge granules onto which filamentous bacteria have aggregated.

[0028] Particularly advantageously, this process makes it possible to avoid episodes of proliferation of filamentous bacteria, thus avoiding a subsequent filtration step, and this without depending on the geometry of the reactor.

[0029] According to the invention, the wastewater is directly dispersed into the biological reactor during feeding and is mixed with the sludge contained within the biological reactor. The advantage of this complete mixing is its resistance to very high pollutant loads as well as to potential short-term toxic shocks.

[0030] As explained above, this process has the advantage of achieving a balance between two populations of granular sludge: granular sludge such as that described in patent WO2004024638, and granular sludge with a population of filamentous bacteria. This balance contributes to optimal wastewater treatment and thus also avoids a subsequent filtration step. Indeed, the presence of filamentous bacteria in the granules allows for the capture of any free bacteria still present in the clarified water. This balance is achieved by controlling the sludge settling rate, which is between 1.2 m / h and 5 m / h. This relatively slow settling rate allows the free bacteria to settle and aggregate with the granular sludge.

[0031] This process therefore allows for a biological treatment of wastewater of quality, economically viable and exploitable on an industrial scale.

[0032] Furthermore, the use of a fully mixed (biological) reactor allows for the treatment of a larger pollutant load, and the process, as already mentioned above, is not dependent on the geometry of the biological reactor used. Indeed, according to the present invention, the process implemented comprises a temporal succession of different steps in the same fully mixed reactor, which eliminates geometric constraints and does not require different zones in which certain treatment steps are carried out by moving the material to be treated, but On the contrary, these steps take place in the same location, but successively or alternately. This also has the advantage of allowing the process according to the present invention to be used for any existing wastewater treatment plant installation or biological reactor while ensuring high-quality wastewater treatment.

[0033] Preferably, the stirring means comprise at least one blade.

[0034] Advantageously, the wastewater supply to the biological reactor is carried out in the upper zone thereof. Said mixing can be carried out continuously or discontinuously.

[0035] Preferably, said continuation of said mixing may take place during said initiation of said aeration, or during said aeration, or after said aeration. Said aeration may be carried out continuously or discontinuously (in bursts).

[0036] Advantageously, the process according to the invention comprises purging at least a portion of said sludge from said central zone of said at least one biological reactor, before or during settling, said portion of the sludge being purged by drawing off said suspension of solid matter from the aqueous phase. This purging is sometimes called homogeneous purging and makes it possible to obtain a relatively uniform population of bacteria comprising filamentous and granular bacteria.

[0037] In other embodiments, the process according to the invention comprises purging at least a portion of said sludge from said central zone of said at least one biological reactor, after settling. This purging is then called selective purging and makes it possible to obtain a relatively uniform population of filamentous bacteria.

[0038] As can be seen, depending on the moment in the process when the purging is applied, we will be faced with a homogeneous purging or a selective purging for withdrawal in a central zone of said biological reactor.

[0039] Sometimes, the process includes purging at least a portion of said sludge from said lower zone of said at least one biological reactor, after settling, said portion of the sludge being purged by drawing off a portion of the sludge bed. This purging is then called homogeneous purging because it makes it possible to obtain a relatively uniform population of bacteria comprising filamentous and granular bacteria.

[0040] During purging, either a mixture of granules and filamentous bacteria is withdrawn, or the filamentous bacteria are withdrawn separately. This choice depends on the area of ​​the biological reactor from which the purging is carried out and / or the timing of the withdrawal.

[0041] If purging is carried out in the central zone of the biological reactor and is performed before or during settling, filamentous bacteria and granules are removed. If purging is carried out in the central zone of the biological reactor but after settling, filamentous bacteria are preferentially removed. extracted so easily.

[0042] If purging is carried out in the lower zone of the biological reactor, the granules and filamentous bacteria are removed, and this purging is performed after settling. This maintains a balance in the levels of filamentous bacteria and granules.

[0043] The purging process allows for adjustment of the sludge concentration relative to the incoming carbon load (COD). This regular adjustment makes it possible to control the quality and granulation rate of the granular sludge, i.e., the rate of granule formation. This adjustment is achieved by adapting the sludge purging. Selective purging promotes granulation and therefore improves settling performance and the quality of the treated water. Homogeneous purging promotes sludge stability and the quality of the treated water.

[0044] Advantageously, said solid materials in said process are formed by said microorganisms and said organic or assimilable matter by microorganisms, said microorganisms forming with said organic or assimilable matter by microorganisms granular sludge or granular sludge with a population of filamentous bacteria.

[0045] In a preferred embodiment, the process further comprises a step of controlling the settling rate, by means of a second supply of wastewater from said upper zone of said at least one biological reactor under aerobic conditions by means of supply means arranged to be actuated by a control means when the biological reactor implements said initiation of said aeration or after said aeration, before or during said continuation of said mixing, said settling control step being followed by an additional mixing step so as to slow down the settling rate of solids in the aqueous phase.

[0046] Said second feed allows a new pollutant load to be introduced and a balance to be restored between the granular sludge and the granular sludge with a population of filamentous bacteria when the balance no longer allows optimal treatment of wastewater and bacterial flocs begin to be found in the discharge.

[0047] In another preferred embodiment, the process further comprises an acidogenesis step upstream of said first wastewater feed to said at least one biological reactor.

[0048] This acidogenesis step improves the cleavage of long-chain carbon molecules and promotes the production of small, highly biodegradable molecules, such as volatile fatty acids. This step is carried out using bacteria under anaerobic conditions.

[0049] Advantageously, said wastewater from the process according to the invention is chosen among industrial waters, urban waters, or a mixture of these.

[0050] In an advantageous embodiment, the process according to the invention further comprises an initial step of adapting an existing installation for the implementation of the process in said adapted existing installation.

[0051] This allows existing installations to be used without modification and represents an economic gain.

[0052] Other embodiments of the process according to the invention are indicated in the attached claims.

[0053] The invention also relates to a reactor called a biological reactor for the biological treatment of wastewater to be used according to the process according to the invention, said biological reactor being an SBR (Sequential Batch Reactor) type reactor arranged to receive wastewater and a sludge containing microorganisms, said wastewater and said sludge containing microorganisms forming a content, this biological reactor includes an inlet for wastewater in fluidic communication with the upper zone, an outlet for treated water in fluidic communication with the upper zone and means for stirring said content, forming a fully mixed type reactor.

[0054] It has been found to be particularly advantageous that a biological reactor with a wastewater inlet in fluidic communication with the upper zone allows for "turbulent" feeding while the mixing of said wastewater and said sludge is carried out by stirring means, forming a fully mixed biological reactor. Furthermore, the biological reactor exhibits at all points relatively identical concentrations of microorganisms, dissolved oxygen from the medium, and organic matter or matter assimilable by microorganisms.

[0055] Turbulent feeding facilitates the complete mixing carried out in the biological reactor, whereas document WO2004024638 describes a slow feeding carried out by an inlet in fluidic communication with the lower zone to avoid mixing of wastewater with treated water and to work on a piston flow, namely a reactor with different zones having a different role.

[0056] In an advantageous embodiment, the biological reactor according to the present invention further comprises means for drawing off at least a part of said sludge in fluidic communication with said lower or central zone, arranged to allow the purging of at least a part of said sludge.

[0057] In a preferred embodiment, the biological reactor according to the present invention further comprises fluidic communication supply means with said upper zone arranged to supply said biological reactor with wastewater. For example, the supply means bring the wastewater into the biological reactor under anaerobic conditions when it is the first feeding of the process according to the present invention or bring the wastewater into the biological reactor under aerobic conditions when it is the second feeding, said feeding means being arranged to be operated by a control means when the biological reactor implements said aeration or after said aeration, before said continuation of the mixing.

[0058] In another preferred embodiment, the biological reactor includes an inlet for the injection of gas in fluidic communication with said central zone or said lower zone of said biological reactor.

[0059] Other embodiments of the biological reactor according to the invention are indicated in the attached claims.

[0060] The invention further relates to an installation comprising at least one biological reactor according to the present invention, further comprising a buffer tank or a biological basin, possibly a biological buffer basin, in fluidic communication with said at least one biological reactor.

[0061] Preferably, the installation according to the present invention further comprises an acidogenic tank in fluidic communication with said at least one biological reactor via said buffer tank or said biological basin, optionally the biological buffer basin.

[0062] Advantageously, the installation includes a second biological reactor, arranged in parallel in co-current or counter-current or even in alternation with said at least one biological reactor.

[0063] Preferably, said second biological reactor and said at least one biological reactor of the installation according to the invention, are in fluidic communication with a buffer tank or a biological basin, possibly a biological buffer basin.

[0064] Other embodiments of the installation according to the invention are indicated in the attached claims.

[0065] Other features, details and advantages of the invention will become apparent from the description given below, by way of non-limitation and with reference to the drawings and examples.

[0066] Fig. 1 is a longitudinal section of a schematic representation of one embodiment of the biological reactor according to the present invention.

[0067] Fig. 2 is a longitudinal section of a schematic representation of another embodiment of the biological reactor according to the present invention.

[0068] Fig. 3 is a schematic representation of one embodiment of an installation according to the present invention.

[0069] Fig. 4 is a diagram explaining the main steps of a preferred embodiment of the biological wastewater treatment process according to the present invention.

[0070] In the figures, identical or analogous elements bear the same reference numerals.

[0071] The biological reactor 8 is shown in [Fig. 1] and 2. The biological reactor 8 illustrated in [Fig. 1] is a biological reactor of the SBR (Sequential Batch Reactor) type which comprises an upper zone 9 extending from the surface of the top of the biological reactor 8 to the upper part of a central zone 11, a lower zone 10 extending from the surface of the bottom of the biological reactor 8 to the lower part of the central zone 11 and the central zone 11 comprising the upper zone 9 and the lower zone 10.

[0072] This biological reactor 8 comprises a wastewater inlet 12 (not shown) in fluidic communication with the upper zone 9 and is arranged to receive the wastewater via the inlet 12 and a sludge containing microorganisms. It comprises a treated water outlet 13 (not shown) in fluidic communication with the upper zone 9 and stirring means 14 arranged to mix the wastewater and the sludge containing microorganisms (not shown). The biological reactor 8 is a fully mixed reactor which, particularly advantageously, allows for the formation of a complete mixture using the stirring means 14 and the formation of a suspension of solids in an aqueous phase.

[0073] The illustrated biological reactor 8 includes an inlet arranged for injecting gas 15, for example dioxygen, and is in fluidic communication with said lower zone 10 of said biological reactor 8. In another embodiment not illustrated, the inlet arranged for injecting gas 15 is in fluidic communication with said central zone 11.

[0074] The biological reactor 8 includes means for removing at least a part of said sludge in fluidic communication with said central zone 11 of said biological reactor 8 arranged to allow the purging of at least a part of said sludge, more particularly of filamentous bacteria.

[0075] In another embodiment illustrated in [Fig.2], the means for drawing off at least a part of said sludge are in fluidic communication with said lower zone 10 of said biological reactor 8 and the inlet arranged for injecting gas 15 is in fluidic communication with said upper zone 9 of said biological reactor 8.

[0076] In another embodiment not illustrated, the withdrawal means 16 are in fluidic communication with said central zone 11 to allow the purging of at least part of said sludge, more particularly filamentous bacteria and other bacteria whose settling rate is less than 2m / h.

[0077] Advantageously, the biological reactor 8 may include feeding means (not illustrated) in fluidic communication with said upper zone 9 arranged to supply said biological reactor 8 with wastewater under aerobic conditions robotics. Said feeding means are arranged to be operated by a control means when the biological reactor 8 implements an aeration 3 or after it, before the continuation of the mixing 4, as appropriate.

[0078] Figure 3 shows an installation comprising a first biological reactor 8, a biological buffer tank 8', and a second biological reactor 8". The first biological reactor 8 and the second biological reactor 8" each include an inlet 12 for wastewater in fluidic communication with the upper zone 9. Both biological reactors 8 and 8" are arranged to receive wastewater via the wastewater inlet 12 and a sludge containing microorganisms. The first biological reactor 8 and the second biological reactor 8" also include an outlet 13 for treated water in fluidic communication with the upper zone 9.

[0079] In this embodiment, the first biological reactor 8 and the second biological reactor 8” operate simultaneously or alternately. This means that wastewater can be fed in parallel into the first biological reactor 8 and the second biological reactor 8” or, alternatively, the treatment steps carried out in the first biological reactor 8 and the second biological reactor 8” are staggered in time.

[0080] The biological buffer basin 8' in fluidic communication with the first biological reactor 8 and the second biological reactor 8”.

[0081] The first biological reactor 8, the second biological reactor 8”, and optionally the biological buffer tank 8’ each comprise stirring means 14, as well as an inlet for an air injector 15, while the wastewater inlet 12 and the withdrawal means 16 are necessarily present only on the first and second biological reactors 8, 8”.

[0082] Depending on the desired effect, said biological reactors 8, 8” are arranged in parallel in co-current or counter-current or even in alternation.

[0083] A buffer tank and / or an acidifying tank (not shown) may be in fluidic communication with said first biological reactor 8 or said second biological reactor 8. The buffer tank and / or the acidifying tank will thus be upstream of the biological reactor with respect to the flow of the process according to the present invention. In the biological reactor 8 illustrated in [Fig. 1] or 2, the process typically includes a wastewater feed 1, for example industrial wastewater and / or urban wastewater as illustrated in [Fig. 4], which includes sludge containing microorganisms, and is carried out under anaerobic conditions.

[0084] The steps described below are described in the context of the biological reactor 8, but apply mutatis mutandis to the biological reactor 8” when it is present as for example in the embodiment illustrated in [Fig.3].

[0085] Still under anaerobic conditions, a mixture 2 of the wastewater with the sludge in Biological reactor 8 is prepared. This mixture 2 forms a suspension of solid materials in an aqueous phase. The solid materials include, for example, polluting load, microorganisms including bacteria, sludge, etc. Mixing 2 can be carried out continuously or discontinuously depending on the circumstances.

[0086] A gas, for example dioxygen, is then injected into said biological reactor 8 through the inlet 15 implementing an initiation of an aeration 3 of said suspension of solid matter in the aqueous phase in said biological reactor 8. The injection of the gas can be carried out continuously or discontinuously (in bursts or in spurts).

[0087] The continued mixing of said wastewater with said sludge under aerobic conditions in said biological reactor 8 is carried out to maintain the suspension of solid matter in the aqueous phase. This continued mixing of said wastewater is carried out until the air in said biological reactor 8 is exhausted and anaerobic or anoxic conditions are again present. The continued mixing of said wastewater may take place during the initiation of said aeration 3 or during the aeration 3 itself. The continued mixing of said wastewater is advantageously carried out continuously but may also be carried out discontinuously.

[0088] Preferably, a purging (not illustrated) of at least a portion of said sludge from said central zone 11 of said biological reactor 8 is carried out before, during or after the settling 5 which follows the continuation of the mixing 4. Said portion of the sludge is purged by drawing off 6 of said suspension of solids in the aqueous phase by drawing off means 16.

[0089] Next, the decantation 5 of said sludge is carried out (and the mixing of the biological reactor is stopped) and makes it possible to obtain treated water formed from said wastewater substantially depleted in organic matter or assimilable by residual microorganisms and possibly containing a first part of microorganisms and also makes it possible to obtain a sludge bed formed from said organic matter or assimilable by residual microorganisms and a second part of microorganisms.

[0090] Particularly advantageously, the settling rate 5 of said sludge is between 1.2 m / h and 5 m / h and makes it possible to obtain, in combination with the fully mixed biological reactor 8, a granular sludge or a granular sludge with a population of filamentous bacteria.

[0091] When filamentous bacteria aggregate on the granules of the granular sludge, they do not move freely and allow for better treatment of the pollutant load by increasing the surface area of ​​adhesion of the granules to the free bacteria. Even more advantageously, this avoids episodes of proliferation of filamentous bacteria which, normally, tend to be withdrawn with the treated water when they do not aggregate with the granules.

[0092] Optionally, a control step (not illustrated) of the decantation 5 is carried out by means of a second supply of wastewater from the upper zone 9 of the biological reactor 8 under aerobic conditions by means of supply means arranged to be operated by a control means. This step may be carried out either when the biological reactor implements the initiation of the aeration 3 or after it, or before or during the continuation of the mixing 4, the settling control step 5 being followed by an additional mixing step 2 so as to slow down the settling rate 5 of the solids in the aqueous phase.

[0093] Advantageously, a purge (not illustrated) of at least a portion of said sludge from said lower zone 10 of said biological reactor 8 is carried out after settling. Said portion of the purged sludge is carried out by drawing off a portion of the sludge bed by means of the drawing-off means 16.

[0094] A withdrawal 6 of at least part of said treated water is then carried out and makes it possible to form a discharge of quality treated water.

[0095] Optionally, an acidogenesis step (not illustrated) is carried out before the first feeding 1 of wastewater into the biological reactor 8. This step allows the long carbon chains of molecules such as fatty acids to be cut.

[0096] The method according to the present invention can be implemented on existing installations comprising at least one SBR type biological reactor 8 by taking control of the existing installation using an automaton for example.

[0097] Examples. -

[0098] Example 1: Treatment of wastewater from the dairy industry.

[0099] Wastewater from a dairy plant was treated by an installation according to the present invention, which comprises, in sequence, an acidifying basin with a capacity of 4 m³, a buffer tank with a capacity of 3.5 m³, and a biological reactor according to the present invention with a capacity of 4.5 m³. The biological reactor, comprising a sludge containing microorganisms, was fed, under anaerobic conditions, with wastewater from the dairy plant at a flow rate of 7 m³ / h. The carbon pollution concentration of the wastewater at the inlet to the biological reactor was 665 mg / L. The phosphorus concentration was 4 mg / L and the nitrogen concentration was 31 mg / L. The daily volume of wastewater from the dairy plant treated is 1.3 m³ / day.

[0100] These wastewaters were then mixed with said sludge, still under anaerobic conditions with a paddle agitator, at a speed of 32 revolutions per minute in the biological reactor according to the present invention, which is an integral mixing reactor forming a suspension of solids in an aqueous phase.

[0101] Aeration of said suspension of solids in the aqueous phase was then initiated by gas injection so as to obtain 1.2 to 2 mg / L of O2 in the reactor biological according to the invention. The quantity of dissolved oxygen indicated above is regulated and sufficient to degrade 89.63% of the organic matter and 60.28% of the mineral matter (62.5% phosphorus and 58.07% nitrogen).

[0102] The mixing of said wastewater with said sludge was continued under aerobic conditions in the biological reactor forming the suspension of solid matter in the aqueous phase.

[0103] The sludge was then settled, yielding (i) treated water consisting of the wastewater with a carbon pollution concentration reduced to 69 mg / L, a phosphorus concentration reduced to 1.2 mg / L, and a nitrogen concentration reduced to 13 mg / L, and (ii) a sludge bed consisting of residual organic matter or matter assimilable by microorganisms and a second portion of microorganisms. The settling rate of the sludge was between 2.5 and 5 m / h.

[0104] A portion of the treated water was then withdrawn to form a treated water discharge with a carbon pollution concentration of 69 mg / L, a phosphorus concentration of 1.5 mg / L and a nitrogen concentration of 13 mg / L

[0105] Example 2: Treatment of wastewater from a phospholipid extraction process contained in eggs.

[0106] Wastewater from a phospholipid extraction line was treated by an installation according to the present invention, which comprises, in sequence, an acidifying basin with a capacity of 4 m³, a buffer tank with a capacity of 3.5 m³, and a biological reactor according to the present invention with a capacity of 4.5 m³. The biological reactor, comprising a sludge containing microorganisms, was fed, under anaerobic conditions, with wastewater from a phospholipid extraction line. The carbon pollution concentration of the wastewater at the inlet to the biological reactor was between 9,000 and 13,000 mg / L. The phosphorus concentration was 30 mg / L and the nitrogen concentration was 120 mg / L. The daily volume of wastewater treated is 0.9 m³ / day.

[0107] These wastewaters were then mixed with said sludge, still under anaerobic conditions with a paddle agitator, at a speed of 32 revolutions per minute in the biological reactor according to the present invention, which is an integral mixing reactor forming a suspension of solids in an aqueous phase.

[0108] Aeration of said suspension of solid matter in the aqueous phase was then initiated by gas injection so as to obtain 1.2 to 2 mg / L of O2 in the biological reactor according to the invention. The quantity of dissolved oxygen indicated above is regulated and sufficient to degrade 98 to 99% of the organic matter and 81.25% of the mineral matter (95.8% of the nitrogen and 66.7% of the phosphorus).

[0109] The mixing of said wastewater with said sludge was continued under aerobic conditions in the biological reactor forming the suspension of solid matter in the aqueous phase.

[0110] The sludge was then decanted, yielding (i) treated water consisting of the wastewater with a carbon pollution concentration reduced to 105 mg / L, a phosphorus concentration reduced to 10 mg / L, and a nitrogen concentration reduced to less than 5 mg / L, and (ii) a sludge bed consisting of the residual organic matter or matter assimilable by microorganisms and a second portion of microorganisms. The settling rate of the sludge was 2 m / h.

[0111] A portion of said treated water was then withdrawn to form a treated water discharge whose carbon pollution concentration was 105 mg / L, the phosphorus concentration was 10 mg / L and the nitrogen concentration was less than 5 mg / L.

[0112] Example 3: Treatment of wastewater from a sweet and flavored beverage bottling industry.

[0113] Wastewater from a sugar and flavored beverage bottling plant was treated according to the present invention. The arrangement used comprises an upstream buffer tank with a total capacity of 600 m³, followed by an installation including a first biological reactor according to the invention and a second biological reactor according to the invention, each with a capacity of 500 m³. The two 500 m³ biological reactors are separated by a buffer biological tank with a capacity of 400 m³. The installation thus has a total capacity of 1400 m³.

[0114] The first and second biological reactors, each containing sludge containing microorganisms, were fed anaerobically with wastewater at a flow rate of between 130 and 230 m³ / h, alternating and in a counter-current fashion, such that when one was being fed, the other was being drained. (The water sent to the first reactor pushed the water from the second reactor towards the outlet of the second reactor.) The carbon pollution concentration of the wastewater at the inlet of both the first and second biological reactors was between 200 and 1200 mg / L. The phosphorus concentration was 1 mg / L and the nitrogen concentration was 7 mg / L. The daily volume of wastewater treated was between 500 and 1500 m³ / day.

[0115] These wastewaters were then mixed with said sludge, still under anaerobic conditions with a paddle agitator, at a speed of 475 revolutions per minute in the first biological reactor and in the second biological reactor according to the present invention.

[0116] Each of the first and second biological reactors is a mixing reactor integral forming a suspension of solid materials in an aqueous phase.

[0117] Aeration of said suspension of solid matter in the aqueous phase was then initiated by gas injection so as to obtain 1.2 to 2 mg / L of O2 in each biological reactor according to the invention. The quantity of dissolved oxygen indicated above is regulated and sufficient to degrade 97% of the organic matter and 83.95% of the mineral matter (82.9% nitrogen and 85% phosphorus).

[0118] The mixing of said wastewater with said sludge was continued under aerobic conditions in said biological reactors forming the suspension of solid matter in the aqueous phase.

[0119] The sludge was then settled, yielding (i) treated water consisting of the wastewater with a carbon pollution concentration reduced to 35 mg / L, a phosphorus concentration reduced to 0.15 mg / L, and a nitrogen concentration reduced to less than 1.2 mg / L, and (ii) a sludge bed consisting of the residual organic matter or matter assimilable by microorganisms and a second portion of microorganisms. The settling rate of the sludge was between 1.8 and 2.5 m / h.

[0120] A portion of said treated water was then withdrawn to form a treated water discharge whose carbon pollution concentration was 35 mg / L, the phosphorus concentration was 0.15 mg / L and the nitrogen concentration was less than 1.2 mg / L.

[0121] Example 4: Municipal wastewater treatment.

[0122] Municipal wastewater was treated by an installation according to the present invention, which comprises, in sequence, a buffer tank with a capacity of 3.5 m³ and a biological reactor according to the present invention with a capacity of 4.5 m³. The biological reactor, comprising a sludge containing microorganisms, was fed, under anaerobic conditions, with municipal wastewater at a flow rate of 7 m³ / h. The carbon pollution concentration of the municipal wastewater at the inlet of the biological reactor was 400 mg / L. The phosphorus concentration was 2 mg / L and the nitrogen concentration was 25 mg / L. The daily volume of wastewater treated is 5.5 m³ / day.

[0123] These municipal wastewaters were then mixed with said sludge, still under anaerobic conditions with a paddle agitator, at a speed of 32 revolutions per minute in the biological reactor according to the present invention, which is a fully mixed reactor forming a suspension of solids in an aqueous phase. Aeration of said suspension of solids in the aqueous phase was then initiated by gas injection so as to obtain 1.2 to 2 mg / L of O2 in the biological reactor according to the invention. The quantity of dissolved oxygen indicated above is regulated and sufficient to degrade 91.25% of the organic matter and 56% of the mineral matter (52% nitrogen and 60% phosphorus).

[0124] The mixing of said wastewater with said sludge was continued under aerobic conditions in said biological reactor, forming a suspension of solid matter in the aqueous phase,

[0125] The sludge was then settled, yielding (i) treated water consisting of the wastewater with a carbon pollution concentration reduced to 35 mg / L, a phosphorus concentration reduced to 0.8 mg / L, and a nitrogen concentration reduced to 12 mg / L, and (ii) a sludge bed consisting of the residual organic matter or matter assimilable by microorganisms and a second portion of microorganisms. The settling rate of the sludge was between 1.3 and 1.8 m / h.

[0126] A portion of said treated water was then withdrawn to form a treated water discharge with a carbon pollution concentration of 35 mg / L, a phosphorus concentration of 0.8 mg / L and a nitrogen concentration of 12 mg / L.

[0127] It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made to it without departing from the scope of the annexed claims.

Claims

Claims

1. Method for the biological treatment of wastewater comprising organic matter or matter assimilable by microorganisms comprising the steps of: - a first supply (1) of wastewater under anaerobic or anoxic conditions to at least one reactor (8) called a biological reactor comprising an upper zone (9), a lower zone (10) and a central zone (11), said at least one biological reactor (8) comprising a sludge provided with microorganisms, - a mixture (2) of said wastewater with said sludge under anaerobic or anoxic conditions in said at least one biological reactor (8) forming a suspension of solid materials in an aqueous phase, - An initiation of an aeration (3) of said suspension of solid matter in the aqueous phase by an injection of gas into said at least one biological reactor (8) with obtaining a quantity of dissolved oxygen sufficient to degrade 50 to 100% of the organic matter and 50 to 100% of the mineral matter, - a continuation of said mixing (4) of said wastewater with said sludge under aerobic conditions or alternately under aerobic and anoxic conditions in said at least one biological reactor (8) forming the suspension of solid materials in the aqueous phase, - decantation (5) of said sludge with obtaining (i) treated water formed from said wastewater substantially depleted in residual organic matter or matter assimilable by microorganisms and possibly containing a first part of microorganisms and (ii) a bed of sludge formed from said residual organic matter or matter assimilable by microorganisms and a second part of microorganisms, - a withdrawal (6) of at least part of said treated water to form a discharge of treated water, characterized in that said at least one reactor (8) called reactor biological is a complete mixing reactor equipped with stirring means (14) so ​​as to form a complete mixture and in that the decantation (5) of said sludge is carried out at a decantation speed (5) of the solid materials in the aqueous phase of between 1.2 m / h and 5 m / h.

2. A method according to claim 1, comprising purging at least a portion of said sludge from said central zone of said at least one biological reactor (8), before or during decantation (5), said portion of the purged sludge being carried out by withdrawing (6) said suspension of solids in the aqueous phase.

3. A method according to claim 1, comprising purging at least a portion of said sludge from said lower zone of said at least one biological reactor (8), after settling (5), said portion of the purged sludge being carried out by drawing off (6) a portion of the sludge bed.

4. A method according to claim 1, wherein said solid materials are formed by said microorganisms and said organic or microorganism-assimilable matter, said microorganisms forming with said organic or microorganism-assimilable matter granular sludge or granular sludge with a population of filamentous bacteria.

5. A method according to claim 4, further comprising a step of controlling the settling rate (5), by means of a second feed (1) of wastewater to said upper zone of said at least one biological reactor (8) under aerobic conditions by feed means arranged to be actuated by a control means when the biological reactor implements said initiation of said aeration (3) or after it, before or during said continuation of said mixing (4), said settling control step (5) being followed by an additional mixing step (2) so as to slow down the settling rate (5) of the solids in the aqueous phase.

6. Method according to any one of the preceding claims, further comprising an acidogenesis step upstream of said first supply (1) of wastewater from said at least one biological reactor (8).

7. A method according to any preceding claim, wherein said wastewater is selected from industrial water, urban water, or a mixture thereof.

8. A method according to any preceding claim, further comprising an initial step of adapting an existing installation for the implementation of the method in said adapted existing installation.

9. Biological reactor for the biological treatment of wastewater to be used according to the method according to any one of claims 1 to 8, said biological reactor (8) being a reactor (8) of the SBR (Sequential Batch Reactor) type arranged to receive wastewater and a sludge provided with microorganisms, said wastewater and said sludge provided with microorganisms forming a content, characterized in that it comprises an inlet for the wastewater (12) in fluid communication with the upper zone (9), an outlet for the treated water (13) in fluid communication with the upper zone (9) and means for stirring (14) said content, forming a biological reactor (8) of the integral mixing type.

10. Biological reactor (8) according to claim 9, further comprising means (16) for withdrawing at least a portion of said sludge in fluid communication with said lower (10) or central (11) zone, arranged to allow the purging of at least a portion of said sludge.

11. Biological reactor (8) according to any one of claims 9 to 10, comprising an inlet for the injection of gas (15) in fluid communication with said central zone (11) or said lower zone (10) of said biological reactor (8).

12. Installation comprising at least one biological reactor (8) according to claims 9 to 11, further comprising a buffer tank or a biological basin, optionally a biological buffer basin, in fluid communication with said at least one biological reactor (8).

13. Installation according to claim 12, further comprising an acidogenic tank in fluid communication with said at least one biological reactor (8) via said buffer tank or said biological basin, optionally the biological buffer basin.

14. Installation according to claim 12 or 13, comprising a second biological reactor (8), arranged in parallel in co-current or counter-current or alternatively alternating with said at least one biological reactor (8).

15. Installation according to claim 14, in which said second biological reactor (8) and said at least one biological reactor (8) are in fluid communication with a buffer tank or a basin biological, possibly a biological buffer basin.

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