Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F3/00—Biological treatment of water, waste water, or sewage
  • C02F3/02—Aerobic processes
  • C02F3/12—Activated sludge processes
  • C02F3/1236—Particular type of activated sludge installations
  • C02F3/1268—Membrane bioreactor systems
  • C02F3/1273—Submerged membrane bioreactors
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/72—Treatment of water, waste water, or sewage by oxidation
  • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/06—Sludge reduction, e.g. by lysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the present invention relates to methods and devices for improving the treatment of wastewater comprising one or more biological treatment (s) associated with a liquid / solid membrane separation member so as to reduce the costs of investment by increasing the filterability of the organic crop and reducing the surface area of the membranes.
• the invention relates to a wastewater treatment process of municipal or industrial origin, loaded with organic matter, a process comprising a step during which the wastewater remains in a treatment device implementing a culture.
• biological system containing the purifying biomass and the separation of which is carried out by filtration through organic or inorganic membranes (micro-, ultra-, nano- or hyperfiltration).
• the filtration membranes are sensitive to clogging, which leads to an initial oversizing of the membrane surface and in the long term to the increase in operating costs corresponding to the reagents used for cleaning them.
• the clogging of membranes by different types of substances, especially dissolved substances such as organic matter, colloids or suspended substances (abbreviated as MeS, suspended matter) is strongly affected by the hydraulic conditions in the vicinity of the filtration membrane. but also by the properties of the microbial floc. Clogging leads to a very significant reduction in the filtration capacity of the membrane, the decline is not always reversible.
• optimal dose of coagulation which according to the experience acquired by those skilled in the art is the dose that allows the best treatment of water clarification during treatment and which will therefore ensure the best working conditions for the membrane, ie the least fouling conditions.
• the present invention aims to provide a method for minimizing or at least reducing the clogging of membranes and improve the filtration capacity while strengthening the economy of the process. To achieve this result the technical problems to be solved are:
• ozone oxidation is used in the field of wastewater treatment to reduce the amount of sludge produced by biological treatment.
• the doses of ozone applied must be large enough to cause the destructuring of the microbial floc, the bursting of bacteria and solubilizing particulate organic materials to render them biodegradable.
• the patent application WO 03078335 describes such a process, where the activated sludge undergoes an ozone pretreatment (dose of 0.02 g O 3 / g solids) in combination with an alkaline and thermal treatment so as to increase the "biodegradability of micro-organisms" by hydrolyzing their cell wall.
• the main disadvantage of these processes is to release in the liquid phase, a non-biodegradable organic fraction called "hard DCO" which accumulates in the membrane bioreactor and whose highly colloidal structure can contribute to the fouling of the filtration membranes.
• the invention proposes a process for the purification of wastewater loaded with organic matter, said process comprising a step of contacting the wastewater with a biological culture containing a purifying biomass and a separation step carried out by filtration. through organic or inorganic membranes, characterized in that at least a portion of said biological culture is subjected to a step of oxidative stress leading to the production of a liquor by action of ozone implemented in a small quantity, at a rate of 0.1 mg to 8 mg of ozone per gram of dry matter of the effluent to be treated, so as to preserve the biological activity of the purifying biomass while modifying the structure of the microbial floc to make it denser .
• oxidative stress is understood to mean a controlled and reduced oxidation of the effluent to be treated so as to cause the partial oxidation of the oxidizable compounds.
• This incomplete oxidation causes a modification and structuring of the sludge so that they become less clogging for the filtration membranes.
• this oxidative stress makes it possible to generate denser and harder flocs while preserving the biological activity of the purifying biomass.
• the liquor is returned to the main device by recirculation.
• the pH is always between 6 and 9 inclusive. This characteristic also makes it possible to preserve the biological activity of the purifying biomass and makes it possible not to have to correct the pH of the effluents and / or the liquor before a possible withdrawal.
• the oxidative stress step is combined with mechanical agitation before the liquor is returned to the main device.
• the mechanical agitation can take place before the oxidative stress step, after the oxidative stress step or the oxidative stress step and the mechanical stirring take place in the same reaction chamber.
• the oxidative stress stage is implemented in an oxidation reactor which comprises at least one vent from which a gaseous effluent comprising at least oxygen comes out, the process further comprising a step of collecting this effluent gas, and reuse said gaseous effluent to treat wastewater or other liquid resulting from the treatment of such wastewater.
• gaseous oxidizing agent such as ozone
• ozone a gaseous effluent rich in oxygen that can be reintroduced at the head of the process to promote the aerobic phase of the treatments organic.
• the oxidative stress stage may be carried out in a reactor operating under pressure, for example from 0.1 to 5 bars.
• the floc becomes larger and wider with a dense and granular structure that can be observed under a microscope.
• the improvement of the properties of the flocks contributes to increasing the filterability of the biological culture.
• the invention also has the advantage of reducing possible biological disorders (especially "bulking") due to filamentous bacteria and significantly increase the sludge decantability.
• the filamentous bacteria which affect the good decantation of the sludge because of their morphology, will be destroyed which will increase the quality of the decantation parameter. This will cause an improvement in the quality and structure of the sludge.
• the invention contributes to producing biological sludge whose dehydratability is greatly improved both in terms of polymer consumption and on the final dryness.
• the method according to the invention gives excellent results when it is applied to membranes of different shapes (capillaries, tubulars, planes, spirals) with internal and external skin, having various configurations (in crankcase, without crankcase and submerged in a pool).
• the invention is also suitable for applications involving the watering of recreational areas and the reuse of wastewater in factories.
• FIG. 1 is a schematic view of a membrane-equipped water treatment installation and implementing a method according to different embodiments of the invention
• FIGS. 2 to 4 are diagrammatic views showing in greater detail the content of the device 9 of FIG. 1, in which the combined treatment of oxidation and mechanical stirring of the effluent to be treated is carried out,
• FIGS. 5 and 6 are views similar to FIG. 1, for another embodiment and invention.
• FIG. 7 shows the evolution of the membrane permeability as a function of time for a conventional process and a process according to the invention.
• FIG. 1 very schematically represents a wastewater treatment plant comprising:
• one or more biological treatment reactors for example a pond 2 in which said organic materials are degraded by the purifying biomass by producing sludge,
• a filtration tank 3 houses filtration membranes 4 which make it possible to separate the liquid phase from the solid phase
• a first recycling loop 7 which collects a portion of the sludge at the outlet 6 and which recycles the sludge at the top of the aeration tank 2, this first recycling loop possibly being eliminated (this recycling loop can for example provide a flow representing 50 to 400% of the nominal flow rate of urban or industrial effluent treated by the treatment plant), and a second loop 8 for converting activated sludge, which also collects part of the sludge at the level of the evacuation 6 and which returns these sludge at the top of the aeration basin 2 after passing through a sludge treatment assembly where said sludge undergo a combined oxidation treatment with ozone and / or oxygen and mechanical agitation.
• the device 9 for oxidation and mechanical stirring for implementing the oxidative stress step in accordance with the method according to the invention, comprises a mechanical stirrer 10 generally consisting of a chamber 11 comprising one or more turbines 12 or possibly dynamic mixers or hydroéjecteurs ... or any other mechanical stirring system.
• the power of the mechanical stirring system is chosen so that the sludge treatment assembly 9 dissipates mechanical stirring energy.
• the device 9 for oxidation and mechanical stirring comprises an oxidation reactor 13 which generally consists of a closed chamber 16 which receives the sludge to be treated and into which ozone is injected from an ozonizer 17 , by means of injection nozzles 14 (possibly replaced by porous diffusers, hydro-ejectors or other), these nozzles being coupled if necessary to static or dynamic mixers.
• Ozonation generally consumes from 0.1 mg to 10 mg of ozone per g of solids contained in the treated sludge which passes through the activated sludge conversion device 9.
• the enclosure 16 may be pressurized, and in this case is the subject of appropriate structural calculations.
• this chamber 16 has a vent 15 from which emanates a gaseous effluent comprising at least oxygen which can be reused at any point in the purification plant, for example at the top of the aeration tank.
• the mechanical stirrer 10 and the oxidation reactor 13 are not necessarily arranged as in FIG. 2; as shown in FIGS. 3 and 4, it is possible:
• the turbine 12 or other stirring system is disposed in the oxidation reactor 18 itself (FIG. 3), this reactor also having characteristics similar to the oxidation reactor 13 described previously
• the sludge treatment assembly 9 with all of its variants described above can optionally take the sludge from the aeration tank 2 and return the treated sludge to the same aeration tank.
• the sludge treatment assembly 9 can withdraw the sludge to be treated at any location in the treatment plant after at least one biological treatment of the wastewater, and return at least a portion of the treated sludge to this biological treatment. .
• the oxidation device in which instead of the oxidative stress stage was composed of a reactor equipped with a mechanical stirring system in which were introduced the effluent to be treated from the bioreactor and the ozone produced from oxygen pure.
• the ozone dose used for this test was 3 mg of ozone per g of solids contained in the effluent to be treated.
• the operating conditions of the membrane were:
• Figure 7 shows the evolution of membrane permeability as a function of time for both systems.
• the permeability of the membrane of the control line is 71 l / hm 2 .bar after 100 days of operation against 154 l / hm 2 .bar for the line equipped with the invention.
• CST capillary Suction Time

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Water Supply & Treatment (AREA)
• Microbiology (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Biodiversity & Conservation Biology (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Activated Sludge Processes (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)
• Treatment Of Sludge (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=36577402

Family Applications (1)

Country Status (9)

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• 2005
  • 2005-09-08 FR FR0509180A patent/FR2890389B1/fr active Active
• 2006
  • 2006-09-01 US US12/066,002 patent/US7867397B2/en active Active
  • 2006-09-01 EP EP06808062A patent/EP1928793A1/de not_active Ceased
  • 2006-09-01 JP JP2008529658A patent/JP2009507625A/ja active Pending
  • 2006-09-01 AU AU2006289072A patent/AU2006289072B2/en not_active Ceased
  • 2006-09-01 CA CA 2620162 patent/CA2620162A1/fr not_active Abandoned
  • 2006-09-01 WO PCT/FR2006/002020 patent/WO2007028879A1/fr active Application Filing
  • 2006-09-01 DE DE2006808062 patent/DE06808062T1/de active Pending
  • 2006-09-01 ES ES06808062T patent/ES2312303T1/es active Pending

Patent Citations (1)

Non-Patent Citations (1)

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