FR2459206A1 - METHOD AND DEVICE FOR THE ANAEROBIC TREATMENT OF WASTEWATER - Google Patents

Abstract

The invention relates to a method and a device for the anaerobic treatment of wastewater. THE DEVICE ACCORDING TO THE INVENTION INCLUDING A TREATMENT CONTAINER THAT CAN BE HEATED IN WHICH IS A FIXED BED CONTAINING BACTERIA AND INCLUDING AT ITS UPPER PART AN OUTLET DUCT FOR THE CURING GAS PRODUCED DURING THE TREATMENT AND AN EXHAUST DUCT FOR THE TREATMENT. PUTREFIED WASTEWATER-SOLID BODY MIXTURE IS CHARACTERIZED BY THE FACT THAT IT INCLUDES A HEAT EXCHANGER 2 WITH BYPASSES FOR THE DELIVERY AND DRAINAGE OF NEW WASTEWATER NOT YET PUTREFIATED, AND WITH A SEPARATE PASSAGE FOR THE PUTREFIATED MIXTURE WASTEWATER-SOLID BODY THE FLOW OF WHICH IS CONDUCTED TO A HOMOGENIZER-CRUSHER WHICH IS CONNECTED TO THE LOWER PART OF THE TREATMENT CONTAINER 4 EQUIPPED WITH A FIXED BED OF SAND 14. APPLICATION TO THE TREATMENT OF WASTEWATER.

Description

The invention relates to an anaerobic wastewater treatment method, in which

  the wastewater is guided, with the solid bodies they contain, from bottom to top, through a fixed bed containing bacteria, at a temperature above room temperature, the wastewater, after a sufficient residence time in the fixed bed for putrefaction, are replaced with the putrefied solid bodies at the top of the fixed bed by introducing new sewage to the lower part, and the mixture sewage - pretreated solid bodies and the cleaning gas it contains separated from each other above the fixed bed are continuously extracted. The present invention relates to

  also a device for implementing this method.

  The above treatment method is known from German Patent No. 2531598. The anaerobic treatment is here carried out in a fixed bed reactor in which is disposed coal, coke, slag, porous stones, for example pumice or of the

  ceramic, as a carrier for anaerobic bacteria. The Treaty-

  temperature is between 10 and 40 ° C, preferably between

  preferably between 20 and 30 ° C., and a treatment time of from 10 minutes to 10 hours, preferably from 0.5 to 3 hours, is indicated. This known method is originally directed only to the putrefaction of the wastewater, without the by-product cleaning gas having received a

great meaning.

  The present invention therefore aims to improve this known method so that the cleansing gas mass that can be obtained is increased by a more energy efficient process possible. This object is achieved in accordance with the invention by virtue of the fact

  the wastewater is preheated and the solid bodies

  are ground and homogenized, the wastewater is subject to the

  anaerobic treatment in a fixed bed of sand at a higher temperature than

  At 40 ° C, the new waste water is preheated by the mixture of wastewater and solids extracted above the fixed bed of sand. The essential characteristics of the process according to the invention reside in a thermophilic treatment at a treatment temperature of greater than 400 ° C., preferably of between 50 ° C. and 550 ° C., which gives, relative to the mesophilic treatment, a yield of 28 ° to 350 ° C. a higher cleaning gas of about 80%, as well as anaerobic treatment in a fixed bed of sand, the sand layer which, thanks to a high heat transfer coefficient, allows a uniform flow of heat , which protects the bacterial flora from temperature variations above - 0.50C. A condition related to the short duration of the treatment is the grinding and homogenization of the solids contained in the wastewater, as well as their preheating which occurs in accordance with the invention in an energy-efficient manner by transmitting the heat of the rotten mixture wastewater - solid bodies. The larger mass of cleaning gas thus gained can be used for heating or as

source of energy for engines.

  To obtain a further increase in the cleaning gas yield, according to a preferred embodiment of the process according to the invention, provision may be made to add to the wastewater, before the grinding and homogenization of the solid bodies that they contain, organic waste. Organic waste, which can be added to wastewater, includes in particular

  leaves, straw, agricultural waste and slaughterhouse waste.

  These organic waste is ground together with the solid bodies already contained in the wastewater and distributed homogeneously in

  the wastewater tending to a particle size less than Imm.

  In the case of excessive thickening of the wastewater by added organic waste, it can be mixed with water. fresh or

  to restore the fluidity necessary for anaerobic treatment.

in the fixed bed of sand.

  Organic waste added to wastewater is a food for anaerobic bacteria. The cleaning gas produced by the disintegration of organic waste by anaerobic bacteria

  increases the amount of cleaning gas produced by the usual putrefaction

it's sewage mud.

  The process according to the invention can be carried out either with fixed cycles or continuously. In the case of a fixed cycle operation, the new wastewater, if necessary supplemented with organic waste, flows into a heat exchanger where it is preheated by heat transfer from the wastewater - solid bodies mixture. rotten. The wastewater is for example transferred by a gear pump, which crushes the solid bodies and the organic waste contained in the wastewater and distributes them homogeneously in the wastewater, through the heat exchanger until preheating, grinding and

  homogenization sufficient. Preheated wastewater is

  sent from the fixed bed of sand, the volume of which increases

  Viron 30%, so that a corresponding volume of putrefied sludge, supernatant and hat at the top of the treatment vessel is pushed into a centrifuge. The centrifuge separates the putrefied sludge and the supernatant liquid from the cleaning gas which is discharged separately. The new wastewater which is introduced into the treatment vessel is gradually rotten

  by bacteria adhering to the sand grains of the fixed bed of sand.

  After completion of the putrefaction process, the rotation is interrupted.

  Sanding the sand in the bioreactor and it occurs spontaneously, in the state of rest, because of the various specific weights, a layered arrangement. The upper layer is constituted by the cap (gaseous foam and light materials with small adhering gaseous bubbles);

  underneath is the supernatant fluid in which the biological process

  logic no longer progresses; underneath is what is called thin sludge, and an older concentrated putrefactive sludge is directly on the fixed bed and is used for inoculation and mixing of the new wastewater introduced. When the new waste water is supplied, the upper cap, after separation into cleaning gas and mixed waste water - solid bodies, is extracted from the reactor

  and the newly fed wastewater is mixed with the putrefactive sludge.

  more concentrated concentrate which rests on the fixed bed by the

Billing of the fixed bed of sand.

  A vortex layer of sand has the advantage over coal, slag, porous stones or ceramic which is known from German Patent No. 2531598, that the swirling is much more intensive and the friction inside. of the vortex layer promotes the rise of gas bubbles. This is particularly true for the gas that forms in the sand bed during the rest period. Gas production is the most important

  shortly after the start of the process but does not stop during the rest.

  The grinding and homogenization of solid bodies and, where

  organic waste in waste water and their

  In conjunction with the higher process temperature, the heating produces a much higher yield of cleaning gas than previously possible with the known process. For temperatures between 50 and 550C, the activity of bacteria is

  the strongest while they meet optimal living conditions.

  For a treatment temperature greater than 550C, the production of

gas almost stops.

  According to an advantageous embodiment of the process according to the invention, it is possible to bring new sludge that has not yet been putrefied into the fixed bed of sand, as well as the separate extraction of the sludge.

  putrefied, supernatant fluid and cleaning gas also continuously.

  This produces a circulation of the contents of the treatment vessel by a bypass duct from its upper part to the pump, so that newly supplied wastewater is mixed and continuously pumped back into the lower part of the treatment vessel. The supernatant putrefied material is compressed in the centrifuge by the newly brought wastewater permanently to be separated into

  putrefied mixture sewage - solid bodies and cleaning gas.

  A device adapted to the implementation of the method according to the invention comprising a heatable treatment container in which there is a fixed bed containing bacteria and having at its upper part an outlet duct cleaning gas produced during the treatment and a separate outlet duct for mixing

  putrefied wastewater - solid bodies, characterized by the fact that it

  takes a heat exchanger with diversions for the supply and disposal of new wastewater not yet rotten, and with a passage

  separated for the putrefied wastewater mixture - solid bodies from which flows

  led to a grinder-homogenizer which is connected to the lower part

  the treatment vessel with a fixed bed of sand.

  To allow a multiple crossing of the waste water for the grinding and the homogenization of the solid bodies which they contain thus

  sufficient preheating, a preferred embodiment of the

  according to the invention provides for a bypass duct going from the grinder

  homogenizer at the top of the heat exchanger. An instantaneous water heater can be inserted in the bypass duct which

  produces additional preheating of wastewater.

  In addition, a bypass duct can lead from the upper part

  of the treatment container at its lower part which allows a

  circulation of the contents of the treatment container.

  Preferably, a tray centrifuge is disposed in the upper portion of the treatment vessel for separating the

  putrefied mixture sewage - solid bodies and cleaning gas.

  The single FIGURE of the appended drawing shows a device

  tif according to an exemplary embodiment of the invention.

  New wastewater, if any loaded with waste

  organic, flow through the inlet I in the heat exchanger 2.

  The wastewater collects in the heat exchanger 2 the heat of the putrefied wastewater sludge which flows through the pipe 3 from the upper part of the treatment vessel 4 to the heat exchanger.

  heat 2 and pass through it by a separate chamber or a serpen-

  tin 5, without mixing with the newly brought wastewater, but are instead removed from the heat exchanger 2 by a conduit 6

  after transmission of their heat.

  At the lower part of the heat exchanger 2, a duct 7 leads to a gear pump 8 in which the solid bodies and, where appropriate, the organic waste are crushed and homogeneously distributed in the wastewater. The wastewater can flow from the pump 8 several times through the heat exchanger 2 by means of a bypass duct 9 into which an instantaneous water heater 10 can be inserted for additional heat supply, until

  that grinding, homogenization and preheating are achieved

  wastewater. Homogenized and preheated wastewater

  are then fed through a conduit I1 to the lower part of the container.

  treatment post 4 which is provided with a heating jacket 12.

  The wastewater flows through a porous or perforated bottom 13 through a layer of sand lying thereon and containing anaerobic bacteria. The height of the sand bed is determined according to the contents of the treatment vessel 4 and / or the flow rate of the pump 8. When the critical flow velocity is exceeded, the sand bed is swirled and forms a fixed bed of sand 14, the stirring per passage being maintained for 15 to 20 minutes. During this time the biological reaction of anaerobic bacteria, which adhere to the surface of individual sand grains, with pumped wastewater occurs. The thickness of the sand bed and the granulometry of the sand grains determine the size of the reactive surface. The larger elements of solid bodies in the water are retained in the lower part of the fixed bed of sand 14. The small gas bubbles have a free exit to the upper face through swirling. During and after the putrefaction phase, emulsified colloids are formed by the bonding of the small gas bubbles with the sewage sludge of waste water and deposit in the form of a hat.

  on the surface of the water above the fixed bed of sand 14.

  A tray centrifuge 16 is disposed in the upper part of the treatment container 4 and, at the beginning of the swirling of the fixed bed of sand 14, the cap 15, the supernatant liquid and the thin sludge are pushed into this centrifuge 16. This separates the cleaning gas. The putrefied sludge is fed via line 3 to the heat exchanger 2 and the cleaning gas leaves the container 4 via line 17 and arrives at a container 18 from which it is fed, via a compressor 19, in a pressure tank 20

o It is stored.

  In this way, 35,000 liters of cleaning gas are obtained from 50 kg of dried organic waste. Since the average CH4 content of the flushing gas is 60%, I Nm3 of gas has a heat capacity of about 6000 kcal. About 210,000 kcal per day are obtained from kg of organic waste, of which only about 8,500 kcal are required for heat requirements or for

  compensation for heat loss from the process.

  A treatment vessel with a volume of I to 2 Nm3 is sufficient for the production of 50 kg of organic waste to cover

  heat needs of a home. The cleaning gas can, after desulfurization

  tion, as well as being used for the supply of a gas engine with

heat pump.

Claims (10)

  1. Anaerobic treatment process for wastewater, in the-   the wastewater is guided, with the solid bodies they contain, from bottom to top, through a fixed bed containing bacteria, at a temperature above room temperature, the wastewater, after a sufficient residence time in the fixed bed for putrefaction, are replaced with putrefied solid bodies at the top of the fixed bed by introduction of new sewage   at the bottom, and the mixture of wastewater - solid bodies pre-   treated and the cleaning gas which it contains separated from each other above the fixed bed are extracted continuously, characterized in that the wastewater is preheated and the solid bodies they contain are crushed and homogenized, the waters are subjected to anaerobic treatment in a fixed bed of sand at a temperature higher than 40'C and the new sewage brought are preheated by the mixture wastewater - solids extracted above fixed bed of sand.   2. Method according to claim 1, wherein is added to the wastewater, before grinding and homogenization of solid bodies.   they contain organic waste.   3. Method according to one of claims I and 2, wherein   the anaerobic treatment is carried out at a temperature of between 50 and 550C.   4. Method according to one of claims I to 3, wherein   the supply of new mud not yet rotten in the fixed bed of sand is carried out, as well as the separate extraction of the rotten mud, the liquid   supernatant and continuous cleaning gas.   5. Device for implementing the method according to one   Claims 1 to 4 comprising a treatment container   to be heated in which there is a fixed bed containing bacteria and having at its upper part a flue gas outlet duct produced during the treatment and a separate outlet duct for the putrefied wastewater - solids mixture, characterized in that it comprises a heat exchanger (2) with by-passes for the supply and discharge of new waste water which has not yet been putrefied and with a separate passage for the putrefied wastewater mixture - solid bodies whose flow leads to a grinder-homogenirator which is connected to the lower part of the treatment container (4) provided with a fixed bed sand (14).   6. Device according to claim 5, wherein a porous or perforated blow bottom (13) is arranged in the lower part.   of the treatment container (4), the fixed bed of sand (14) provided with bacterium   is located above the bottom (13) and the arrival of waste water   heated is under the bottom (13).   7. Device according to one of claims 5 and 6, in   which the mill-homogenizer is constituted by a pump with gears (8).   8. Device according to one of claims 5 to 7, in   which a bypass duct (9) goes from the grinder-homogenizer to the part   upper heat exchanger (2).   9. Device according to claim 8, wherein a   instantaneous water heater 491st interposed in the bypass duct (10).   10. Device according to one of claims 5 to 9, in   which a bypass duct leads from the upper part of the treatment container4a its lower part which allows a circulation of   contents of the treatment container (4).   He. Device according to one of Claims 5 to 10, in   wherein a platen centrifuge (16) is disposed in the upper portion of the treatment vessel (4) for separating the mixture   putrefied wastewater - solid bodies and cleaning gas. oA