CN110713318B

CN110713318B - Treatment system and treatment method for dehydration filtrate after anaerobic digestion of sludge

Info

Publication number: CN110713318B
Application number: CN201911053001.1A
Authority: CN
Inventors: 王晓阳; 汪德罡; 谢晓朋
Original assignee: Beijing Hanqi Environment Technology Co ltd
Current assignee: Beijing Hanqi Environmental Technology Co.,Ltd.
Priority date: 2019-09-29
Filing date: 2019-10-31
Publication date: 2022-07-19
Anticipated expiration: 2039-10-31
Also published as: CN110713318A

Abstract

The invention discloses a treatment system and a treatment method of dehydrated filtrate after anaerobic digestion of sludge, wherein the treatment system comprises an ammonia evaporation pretreatment unit, an ammonia nitrogen treatment unit, a nitrate nitrogen treatment unit and a COD treatment unit, wherein a flocculation zone of a first sedimentation tank of the ammonia evaporation pretreatment unit is arranged in a sedimentation zone and does not comprise an inclined tube sedimentation zone; the water in the secondary BFR anoxic reaction tank of the nitrate nitrogen treatment unit flows back to the primary BFR anoxic reaction tank; the powdered activated carbon in the secondary BFR aerobic reaction tank of the COD treatment unit internally reflows to the primary BFR aerobic reaction tank. The treatment method comprises the steps of sequentially carrying out ammonia evaporation pretreatment, ammonia nitrogen treatment, nitrate nitrogen treatment and COD treatment on the dehydration filtrate to finally obtain the dehydration filtrate meeting the standard. The treatment system is used for treating the sewage with high suspended matters, high viscosity and high ammonia nitrogen, and has the advantages of high efficiency in treating impurities in the sewage and high effluent quality.

Description

Treatment system and treatment method for dehydration filtrate after anaerobic digestion of sludge

Technical Field

The invention relates to the field of sewage treatment systems, in particular to a system and a method for treating dehydrated filtrate after anaerobic digestion of sludge.

Background

At present, anaerobic digestion process is recommended to be adopted to carry out reduction and stabilization treatment on sludge in a sewage plant, wherein anaerobic digestion of the sludge means that biodegradable organic matters in the sludge are decomposed into CH by facultative bacteria and anaerobic bacteria under the anaerobic condition₄、CO₂、H₂O and H₂S digestion technology. It can remove 30-50% of organic matters in the waste and stabilize the organic matters, is one of common means for reducing and stabilizing sludge, and is the most economic sludge treatment method for large-scale sewage plants.

The anaerobic digestion of sludge is a multi-stage complex process, and at present, two-stage theory, three-stage theory and four-stage theory are applied to the biochemical process of anaerobic digestion. Wherein the three-stage theory means that three stages, namely hydrolysis and acidification stages, an acetoxylation stage and a methanation stage, are needed. The stages are both interrelated and interacting, each stage having its own distinct microbial population.

Large amounts of methane are produced in the methanation stage of anaerobic digestion and can be utilized after further processing; meanwhile, the process can release high-concentration ammonia, and the dehydration filtrate with high ammonia nitrogen content finally flows back to a sewage treatment system, so that the investment and the operating cost of sewage treatment are increased.

At present, a nitrification and denitrification process is adopted for treating ammonia nitrogen in sewage in a relatively common mode, namely, firstly, nitrate is generated after ammonia salt in wastewater is oxidized and nitrified, and then the nitrate is decomposed into nitrogen and ammonia through denitrification, but the process has more oxygen consumption.

In the denitrification technology, the anaerobic ammonia oxidation technology is a new technology, ammonia is used as an electron donor, nitrate or nitrite is used as an electron acceptor, and the ammonia is oxidized into nitrogen under the anaerobic condition, so that the oxygen supply is saved by more than 60% compared with the whole-course nitrification (ammonia is oxidized into nitrate). The use of ammonia as an electron donor also saves the carbon source required in the conventional biological denitrification process. The anaerobic ammonia oxidation technology overcomes a plurality of defects compared with the traditional denitrification technology, has more advantages, such as energy and carbon source saving, no alkali supplement, low sludge yield, high load, small occupied area and the like, and has better treatment effect on ammonia nitrogen in high ammonia nitrogen wastewater, thereby receiving general attention. For example, the anaerobic ammonia oxidation process has the advantages of energy and carbon source saving, no need of alkali supplement, low sludge yield, high load, small occupied area and the like.

However, this process also has a number of problems: firstly, inflow water of an anaerobic ammonia oxidation system comes from plate-and-frame filter press, filter cloth is prone to generating problems after the plate-and-frame system runs for a long time, once the filter cloth leaks, the content of suspended solid in inflow water of the whole anaerobic ammonia oxidation system is increased, the operation is continued after the plate-and-frame filter press runs for a long time, the amount of precipitated sludge at the bottom of an adjusting tank is increased, and the normal operation of the adjusting tank is affected, so that the adjusting tank needs to be overhauled, the whole anaerobic ammonia oxidation system needs to be stopped in the conventional setting for overhauling the adjusting tank, and the plate-and-frame filter press flows back to a water inflow pump room again, so that the subsequent sewage treatment is affected; secondly, the microorganism bacteria used in the anaerobic ammonia oxidation system are anaerobic ammonia oxidation bacteria (rhodobacter), the rhodobacter is slow in production, low in cell yield, poor in settling property and easy to run off, and the biological activity in the reactor is difficult to maintain, so that the deamination efficiency is low; and anaerobic ammonia oxidation bacteria (rhodobacter) have strict requirements on the environmental temperature, which is one of the reasons that most of domestic anaerobic ammonia oxidation processes stay in a small test stage and large-scale sewage deamination treatment cannot be realized; in addition, the generation time of the rhodobacter is usually 11 days due to the growth and slow growth of the rhodobacter, so that the start-up of the anaerobic ammonia oxidation process needs a relatively long period to start slowly, the start-up time of the first productive device in the world is as long as 3.5 years, and the excessively long start-up time is a great obstacle for the engineering application of the rhodobacter. Therefore, in engineering application, how to control the temperature of the reactor and ensure the stable operation of the ammonia nitrogen treatment system with high efficiency and stability is a problem which needs to be solved urgently in the current design.

Except that the concentration of ammonia nitrogen in the dehydration filtrate after anaerobic digestion of sludge is higher, the dehydration filtrate also has higher Total Phosphorus (TP), Suspended Solid (SS), COD and the like, the biochemical ratio is extremely poor, most of the COD are COD which are difficult to degrade, and a common biochemical unit basically has no effect, so that most of the dehydration filtrate adopts a mode of combining biochemistry, nanofiltration and reverse osmosis, because the rejection rate of reverse osmosis to pollutants is high, the treated water can be discharged up to the standard, but the reverse osmosis membrane intercepts salt and pollutants in the water, so that the salt and COD are concentrated and enriched in the reverse osmosis concentrated solution after concentration, most of the treatment of the reverse osmosis concentrated solution at present adopts a recharging mode, but the recharging of the concentrated solution can cause the increase of the salt and the pollutants of the whole garbage leachate system, the concentration of the salt and the pollutants is continuously improved and accumulated, and finally the biochemical system and the reverse osmosis system can be paralyzed, the difficulty of the current process is that the concentrate from reverse osmosis cannot be finally processed.

Therefore, it is necessary to find a high-efficiency and low-cost treatment system and method for treating high-suspended matter and high ammonia nitrogen sewage.

Disclosure of Invention

Aiming at the defects in the prior art, the first purpose of the invention is to provide a system for treating the dewatering filtrate after anaerobic digestion of sludge, which has the advantages of effectively removing suspended matters, nitrate nitrogen and ammonia nitrogen in the dewatering filtrate with high density, high ammonia nitrogen and high suspended matters.

The second purpose of the invention is to provide a method for treating the dehydration filtrate after anaerobic digestion of sludge, which has the advantages of high-efficiency and low-cost treatment of the dehydration filtrate with high density, high viscosity, high ammonia nitrogen and high suspended matters.

In order to achieve the first object, the invention provides the following technical scheme:

a system for treating dehydrated filtrate after anaerobic digestion of sludge comprises an ammonia distillation pretreatment unit, an ammonia nitrogen treatment unit, a nitrate nitrogen treatment unit and a COD treatment unit which are sequentially communicated along the flow direction of the dehydrated filtrate;

the ammonia distillation pretreatment unit comprises a dehydration filtrate adjusting tank, a coagulation tank and a first sedimentation tank which are sequentially communicated, wherein the dehydration filtrate adjusting tank is communicated with an alkali liquor input pipe;

the ammonia nitrogen treatment unit comprises an ammonia still, an ammonia still inlet pipe is communicated with the ammonia still, and an alkali liquor input pipe is communicated with the ammonia still inlet pipe;

the nitrate nitrogen treatment unit comprises a primary BFR anoxic reaction tank and a secondary BFR anoxic reaction tank which are communicated, denitrifying biological fillers are added into the primary BFR anoxic reaction tank and the secondary BFR anoxic reaction tank, and a reflux device is arranged between the primary BFR anoxic reaction tank and the secondary BFR anoxic reaction tank;

the COD treatment unit comprises a primary BFR aerobic reaction tank, an ozone catalytic oxidation unit and a secondary BFR aerobic reaction tank added with powdered activated carbon, which are sequentially communicated, wherein a carbon return pipe communicated with the primary BFR aerobic reaction tank is arranged on the secondary BFR aerobic reaction tank;

the lower stream of the first-stage BFR aerobic reaction tank is communicated with a second sedimentation tank, the lower stream of the second-stage BFR aerobic reaction tank is communicated with a third sedimentation tank, the sludge outlet end of the third sedimentation tank is communicated with the first-stage BFR aerobic reaction tank, the water outlet end of the third sedimentation tank is communicated with a clear water outlet tank, and the sludge outlet end of the second sedimentation tank is communicated with a sludge treatment system;

the first sedimentation tank comprises a tank body and a guide cylinder arranged in the tank body, the guide cylinder divides the tank body into a flocculation area and a sedimentation area, the area in the guide cylinder is the flocculation area, and the area outside the guide cylinder in the tank body is the sedimentation area;

the sedimentation zone is provided with the concentrated mud scraper, the cell body is through setting up the one-level sedimentation tank mud pipe and the sludge treatment system intercommunication in its bottom, cell body upper portion intercommunication has the outlet basin, the outlet basin is through setting up one-level sedimentation tank outlet pipe and ammonia nitrogen treatment unit intercommunication in its one side.

By adopting the technical scheme, the dehydrated filtrate sequentially passes through the ammonia distillation pretreatment unit, the ammonia nitrogen treatment unit, the nitrate nitrogen treatment unit and the COD treatment unit according to the flowing direction of the dehydrated filtrate to carry out standard treatment on the dehydrated filtrate.

The flocculation area of the sedimentation tank is arranged in the sedimentation area, and the inclined tube sedimentation area is removed, so that the space occupied area of equipment is saved; meanwhile, the installation of a pipeline for communicating the flocculation area with the sedimentation area is avoided, and the installation of equipment is simpler; in addition to this, such an arrangement makes the precipitation process more efficient. Because the flocculation area is provided with the axial flow stirrer, the flocculating agent adding ring and the central steady flow cylinder, the generation of vortex is inhibited, thereby reducing the danger of the rotation of a large amount of liquid in the sedimentation tank and ensuring more effective flocculating agent distribution. Meanwhile, partial sludge in the settling zone is sucked into the coagulation tank from the bottom of the guide cylinder to form sludge internal reflux, the water inflow and the internal reflux sludge are fully mixed and separated to generate efficient flocculation reaction and net catching effect, larger and more compact sludge flocs which are not easy to break are generated, the settleability of the sludge is effectively improved, the effluent quality is improved, the use of a flocculating agent is saved, and the treatment cost is reduced. In addition, the design of the axial-flow type stirring paddle blade is matched with the lower rotating speed of the axial-flow type stirring paddle blade, so that colloid particles in water are collided and adsorbed and gradually form larger flocculating constituents, the solid-liquid separation effect of a settling zone is improved, and the axial-flow type stirring paddle blade has the effects of high liquid discharge capacity and low energy consumption. After ammonia evaporation pretreatment, firstly treating ammonia nitrogen in the dehydration filtrate, and then treating nitrate nitrogen in the dehydration filtrate.

In the process of treating nitrate nitrogen in the dehydrated filtrate, the two-stage series BFR anoxic reaction tanks added with denitrifying biological fillers are adopted to carry out denitration nitrogen treatment on the dehydrated filtrate, and meanwhile, the water inflow in the two-stage BFR anoxic reaction tanks flows back to the one-stage BFR anoxic reaction tank in a combined manner, so that the efficient treatment on the nitrate nitrogen in the dehydrated filtrate is realized.

The aerobic reaction tank in the COD treatment unit is loaded with materials (powdered activated carbon), which has the most remarkable advantages of adsorbing organic pollutants and changing the retention time of the organic pollutants in a biochemical system from hydraulic retention time to sludge age, thereby providing sufficient degradation time for microorganisms attached to the powdered activated carbon to the organic pollutants; meanwhile, the powdered activated carbon system can adsorb toxic organic matters and heavy metals, can be used as a microorganism growth carrier, protects sensitive microorganisms, greatly promotes the biological phase in the biochemical reaction tank, and enables the biochemical system to achieve higher treatment efficiency; based on the principle of adsorption isotherm of activated carbon, the higher the concentration of organic pollutants, the larger the adsorption amount of activated carbon, so that the powdered activated carbon can still adsorb a large amount of pollutants after entering a first-stage aerobic reaction tank after reaching adsorption balance in a second-stage aerobic reaction tank; besides, the powdery activated carbon loaded biochemical system can treat odor at the same time.

After sewage passes through the primary BFR aerobic reaction tank, biodegradability in the sewage is reduced to be extremely low, an ozone catalytic oxidation unit is added behind the primary BFR aerobic biochemical tank, COD (chemical oxygen demand) is removed, biodegradability of the sewage is increased, and biochemical reaction of the sewage can continue to occur in the secondary BFR aerobic reaction tank. The biochemical system loaded by the powdered activated carbon is combined with catalytic oxidation of ozone, so that the adding amount of the powdered activated carbon and the using amount of the ozone can be greatly reduced, COD in sewage is reduced to the maximum extent through aerobic biochemical reaction, and the system operation cost under the combined mode is the lowest.

Therefore, in conclusion, the water treatment system of the invention has the effect of sequentially removing solid suspended matters, ammonia nitrogen, nitrate nitrogen and COD in sewage with high density, high viscosity, high ammonia nitrogen and high suspended matters with high efficiency and low consumption.

Further, the primary BFR anoxic reaction tank and the secondary BFR anoxic reaction tank are respectively communicated with a sodium acetate adding tank.

By adopting the technical scheme, since acetic acid (root) is one of carbon sources which enable the denitrification rate of microorganisms to be highest, the addition of sodium acetate ensures that the nitrate nitrogen in effluent is lower than 45 mg/L.

Furthermore, filter screen cylinders are arranged at the water outlets at the tail ends of the primary BFR anoxic reaction tank and the secondary BFR anoxic reaction tank.

By adopting the technical scheme, the denitrification biological filler is effectively prevented from flowing out of the anoxic reaction tank, so that the smooth proceeding of denitrification reaction is ensured, and the efficient and stable proceeding of water treatment is ensured.

Furthermore, all be provided with the second dive mixer in one-level BFR oxygen deficiency reaction pond and the second grade BFR oxygen deficiency reaction pond, the rigid coupling has the lining to glue on the paddle of second dive mixer.

By adopting the technical scheme, the damage of the metal paddle to the denitrification biological filler is effectively avoided.

Further, the efficient sedimentation tank comprises a second sedimentation tank and a third sedimentation tank, and the second sedimentation tank and the third sedimentation tank are arranged in the same structure as the first sedimentation tank; the second sedimentation tank is communicated with the sludge treatment system through a second-stage sedimentation tank sludge discharge pipe arranged at the bottom of the second sedimentation tank, and the third sedimentation tank is communicated with the first-stage BFR aerobic reaction tank through a third-stage sedimentation tank sludge discharge pipe arranged at the bottom of the third sedimentation tank.

By adopting the technical scheme, the powdered activated carbon and the activated sludge in the secondary BFR aerobic reaction tank are internally refluxed into the primary BFR aerobic reaction tank, and the aim of saving materials is fulfilled. Meanwhile, the wet density of the powdered activated carbon is high, flocs formed by the powdered activated carbon and the activated sludge are easy to precipitate, but if a common sedimentation tank is adopted, very fine powdered activated carbon or sludge particles are easy to appear in effluent or on the surface of the tank, so that the effluent quality or the treatment efficiency of ozone catalytic oxidation is influenced; by adopting the second sedimentation tank and the third sedimentation tank, the internal reflux of the sludge is realized through the unique central flocculation area structure, the inlet water and the internal reflux sludge are fully mixed, the high-efficiency flocculation reaction and the net catching effect are generated, the very fine powdered activated carbon or sludge particles are effectively removed, larger and more compact sludge flocs which are not easy to break are generated, and the settleability of the sludge and the effluent quality are effectively improved.

Furthermore, the primary BFR aerobic reaction tank and the secondary BFR aerobic reaction tank are both provided with aeration heads.

By adopting the technical scheme, sufficient oxygen is provided for aerobic reactions in the primary BFR aerobic reaction tank and the secondary BFR aerobic reaction tank.

Further, the ozone catalytic oxidation unit comprises an ozone contact oxidation pond and an ozone degassing pond communicated with the ozone contact oxidation pond, the ozone contact oxidation pond is divided into four zones along the water flow direction, the first three zones are provided with microporous gas dispersing heads communicated with an ozone source, and the fourth zone is provided with a gas dispersing perforated pipe communicated with the ozone source.

By adopting the technical scheme, the ozone adding amount of different sections can be adjusted according to different water quality conditions of the incoming water, and the highest ozone utilization efficiency and the best biochemical improvement effect are ensured.

In order to achieve the second object, the invention provides the following technical scheme:

a method for treating dehydration filtrate after anaerobic digestion of sludge comprises the following steps:

enabling the dehydrated filtrate subjected to anaerobic digestion to sequentially enter a dehydrated filtrate adjusting tank, a coagulation tank and a first sedimentation tank of an ammonia distillation pretreatment unit, and adding alkali liquor into the dehydrated filtrate adjusting tank in the process to generate flocculent precipitates in the dehydrated filtrate; adding a coagulant into the coagulation tank, and generating a flocculating constituent in the dehydrated filtrate; adding a flocculating agent into the first sedimentation tank, forming flocculating constituents in the dewatering filtrate, and settling in a settling zone at the lower end of the guide cylinder; meanwhile, part of the sediment flows back into the coagulation tank through the first sludge return pipe, the other part of the sludge is discharged through a sludge discharge pipe of the primary sedimentation tank, and the dehydrated filtrate treated by the ammonia evaporation pretreatment unit is discharged through a water outlet pipe of the primary sedimentation tank;

introducing the dehydrated filtrate discharged from a water outlet pipe of the primary sedimentation tank into an ammonia still, and removing ammonia nitrogen to obtain dehydrated filtrate of ammonia nitrogen;

introducing the dehydrated filtrate subjected to ammonia nitrogen treatment into a first-stage BFR anoxic reaction tank and a second-stage BFR anoxic reaction tank, controlling the pH value and ORP value in the denitrification process, performing denitrification treatment, and starting a reflux device; the dehydrated filtrate after nitrate nitrogen treatment is sequentially introduced into a first-stage BFR aerobic reaction tank, a second sedimentation tank, an ozone catalytic oxidation unit, a second-stage BFR aerobic reaction tank and a third sedimentation tank for COD treatment; in the process, the sludge containing powdered activated carbon in the secondary BFR aerobic reaction tank flows back to the primary BFR aerobic reaction tank, and the sludge in the primary BFR aerobic reaction tank is conveyed to a sludge treatment system; and introducing the dehydrated filtrate subjected to the COD treatment into a clear water outlet pool to obtain final outlet water.

By adopting the technical scheme, the dehydrated filtrate is sequentially subjected to precipitation of solid suspended matters, ammonia nitrogen removal, nitrate nitrogen removal and COD removal. In the process of removing solid suspended matters, adding alkali liquor into a dehydration filtrate regulating tank, wherein iron ions and carbonate ions in dehydration filtrate exist in a precipitation form under an alkaline condition, simultaneously, under the action of a coagulant, fine alum flocs are formed after the processes of destabilization, point neutralization, adsorption bridge formation and the like of the solid suspended matters in the dehydration filtrate, the fine alum flocs and ferric hydroxide and the like are precipitated and enter a first precipitation tank, and the fine alum flocs are further aggregated to form larger and compact alum flocs in a flocculation area of the first precipitation tank under the action of a flocculant, wherein the addition of the alkali liquor, the coagulant and the flocculant is determined according to the actual condition of the dehydration filtrate, and the method has the advantage of quickly and efficiently separating the solid suspended matters in the dehydration filtrate and water bodies of the dehydration filtrate after precipitation.

In the process of treating the nitrate nitrogen in the dehydrated filtrate, the pH and ORP ranges in the first-stage BFR anoxic reaction tank and the second-stage BFR anoxic reaction tank are controlled, so that an optimal reaction environment can be provided for denitrifying bacteria, and the treatment efficiency of denitrifying microorganisms in the biological filler on the nitrate nitrogen in the dehydrated filtrate is higher. Meanwhile, the dehydration filtrate in the secondary BFR anoxic reaction tank flows back to the primary BFR anoxic reaction tank in a backflow amount which is 10 times of the water inlet flow, so that the concentration of nitrate nitrogen in the primary BFR anoxic reaction tank is rapidly reduced, and the dehydration filtrate which flows back to the primary BFR anoxic reaction tank flows into the secondary BFR anoxic reaction tank again, so that the nitrate nitrogen in the dehydration filtrate is treated for many times. The denitrification of denitrifying microorganism and the internal reflux of the dehydrated filtrate efficiently complete the removal of nitrate nitrogen in the dehydrated filtrate under the combined action of the denitrifying microorganism and the dehydrated filtrate.

In the process of removing COD in the dehydrated filtrate, two stages of BFR aerobic reaction tanks are connected in series and an ozone catalytic oxidation unit is combined to carry out the operation of the unit. Firstly, the pH value and the dissolved oxygen value of a first-level BFR aerobic reaction tank are controlled, so that the aerobic microorganisms in the activated sludge are in an optimal reaction environment, the degradation of organic matters in the dehydrated filtrate by the aerobic microorganisms is promoted, the biodegradability of the dehydrated filtrate is reduced to be extremely low after the first-level BFR aerobic reaction tank is used, the addition of an ozone catalytic oxidation unit can degrade COD in the dehydrated filtrate, and meanwhile, the biodegradability of sewage is also increased, so that the dehydrated filtrate can continuously generate biochemical reaction in a second-level aerobic reaction tank. The method comprises the following steps of pumping sludge containing powdered activated carbon in a secondary BFR aerobic reaction tank into a primary BFR aerobic reaction tank, and carrying out 100-150% internal reflux on the sludge containing the powdered activated carbon.

In conclusion, the invention has the following beneficial effects:

firstly, the dehydrated filtrate is sequentially treated by the ammonia distillation pretreatment unit, the ammonia nitrogen treatment unit, the nitrate nitrogen treatment unit and the COD treatment unit, the first sedimentation tank of the ammonia distillation pretreatment unit is not provided with an inclined pipe, and the high-efficiency and effective treatment of high suspended matters in the dehydrated filtrate is realized by combining the structural characteristics of a guide cylinder and an axial flow type stirrer of the high-efficiency sedimentation tank; in the nitrate nitrogen treatment unit, the inlet water in the secondary BFR anoxic reaction tank flows back to the primary BFR anoxic reaction tank, so that the nitrate nitrogen in the dehydrated filtrate is efficiently treated; the powdery active carbon and the activated sludge in the second-stage aerobic reaction tank in the COD treatment unit flow back to the first-stage aerobic reaction tank and are continuously added with brand new powdery active carbon in the second-stage aerobic reaction tank, so that the effluent quality is effectively ensured, and meanwhile, the consumption of raw materials is saved, and the COD treatment unit is more economical.

Secondly, in the design of the high-efficiency sedimentation tank, the flocculation zone is arranged in the sedimentation zone, and the inclined tube sedimentation is removed, so that the space occupied area of equipment is saved firstly; meanwhile, the installation of a pipeline for communicating the flocculation area with the sedimentation area is avoided, and the installation of equipment is simpler; in addition to this, such an arrangement makes the precipitation process more efficient. The flocculation area is provided with the axial flow stirrer, the polymer electrolyte adding ring, the central flow stabilizing cylinder and the arrangement of internal sludge backflow, so that the settleability of the sludge is effectively improved, the solid-liquid separation effect of the sedimentation area is improved, the effluent quality is improved, the use of a flocculating agent is saved, and the effects of high liquid discharge capacity and low energy consumption are achieved.

And thirdly, performing ammonia distillation pretreatment, ammonia nitrogen treatment, nitrate nitrogen treatment and COD treatment on the dehydrated filtrate in sequence, and realizing the treatment on the dehydrated filtrate with high density, high viscosity, high ammonia nitrogen and high suspended substances efficiently and at low cost by controlling the reaction conditions in the BFR anoxic reaction tank and the BFR aerobic reaction tank through sludge backflow in the efficient sedimentation tank, internal backflow of denitrification fillers between the BFR anoxic reaction tanks and backflow of powdered activated carbon between the BFR aerobic reaction tanks.

Drawings

FIG. 1 is a block diagram of a processing system for carrying out the process of the invention;

FIG. 2 is a block diagram of an ammonia still pretreatment unit according to the present invention;

FIG. 3 is a structural view of a high efficiency sedimentation tank according to the present invention;

FIG. 4 is a structural diagram of an ammonia nitrogen treatment unit of the invention;

FIG. 5 is a block diagram of a nitro-nitrogen treatment unit according to the present invention;

FIG. 6 is a view showing the structure of a COD treatment unit according to the present invention;

FIG. 7 is a block diagram of an ozone catalytic oxidation unit of the present invention;

FIG. 8 is a flow chart of a process provided by the present invention.

In the figure: 1. an ammonia distillation pretreatment unit; 11. a dehydrated filtrate adjusting tank; 111. a dehydrated filtrate outlet pipe; 112. a water outlet pipe of the filtrate adjusting tank; 113. a first submersible mixer; 12. a coagulation tank; 121. a water outlet pipe of the coagulation tank; 122. a coagulation stirrer; 13. an alkali liquor storage tank; 14. a coagulant adding barrel; 141. a coagulant adding pipe; 26. a middle water tank; 261. a water outlet pipe of the middle water tank; 2. an ammonia nitrogen treatment unit; 21. an ammonia still; 22. an ammonia tower water inlet pump; 24. a water outlet pipe of the ammonia nitrogen treatment unit; 25. an ammonia still inlet pipe; 3. a nitrate nitrogen treatment unit; 31. a first-stage BFR anoxic reaction tank; 311. denitrifying biological filler; 312. a second submersible mixer; 32. a secondary BFR anoxic reaction tank; 33. a sodium acetate adding tank; 331. a sodium acetate water outlet pipe; 34. distributing a water well; 35. an acid liquor tank; 351. an acid liquor outlet pipe; 4. a COD treatment unit; 41. a primary BFR aerobic reaction tank; 411. an aeration pipe; 412. a water outlet pipe of the primary aerobic tank; 42. an ozone catalytic oxidation unit; 422. an ozone contact oxidation tank; 4221. an ozone delivery pipe; 4222. a microporous air diffusing head; 4223. a gas dispersion perforated pipe; 4224. a first baffle; 4225. a second baffle; 423. an ozone degassing pool; 4231. an ozone unit water outlet pipe; 4232. a guide wall; 43. a secondary BFR aerobic reaction tank; 431. a water outlet pipe of the secondary aerobic tank; 432. a powdered activated carbon feeding device; 433. a carbon return pipe; 44. a second sedimentation tank; 441. a water outlet pipe of the secondary sedimentation tank; 442. a sludge discharge pipe of the secondary sedimentation tank; 45. a third sedimentation tank; 451. a water outlet pipe of the third-stage sedimentation tank; 452. a sludge discharge pipe of the third-stage sedimentation tank; 5. clear water is discharged from the pool; 6. a first sedimentation tank; 61. a tank body; 611. a sludge discharge pipe of the primary sedimentation tank; 612. a water outlet pool; 6121. a water outlet pipe of the primary sedimentation tank; 613. a concentrating mud scraper; 6133. a cross beam; 6134. a mud scraper; 6135. a connecting arm; 614. a tank side wall; 615. the bottom wall of the pool; 616. a sludge collection tank; 62. a draft tube; 621. an axial flow agitator; 6211. an axial flow type stirring blade; 622. adding a flocculating agent into a ring; 623. a first sludge return pipe; 63. and a flow stabilizing cylinder.

Detailed Description

The invention discloses a treatment system of dewatered filtrate after anaerobic digestion of sludge, which comprises an ammonia evaporation pretreatment unit 1, an ammonia nitrogen treatment unit 2, a nitrate nitrogen treatment unit 3 and a COD treatment unit 4 which are sequentially communicated along the flow direction of wastewater, wherein solid precipitates, ammonia nitrogen, nitrate nitrogen and COD in the dewatered filtrate after anaerobic digestion of sludge are sequentially treated, and finally, discharge water meeting the standard is obtained.

Specifically, as shown in fig. 2, the ammonia distillation pretreatment unit 1 includes a dewatering filtrate adjusting tank 11, a coagulation tank 12 and a first sedimentation tank 6 which are sequentially communicated, a plate-frame filtration system is communicated with a dewatering filtrate outlet pipe 111, the plate-frame filtration system is communicated with the dewatering filtrate adjusting tank 11 through the dewatering filtrate outlet pipe 111, the dewatering filtrate adjusting tank 11 is communicated with the coagulation tank 12 through a filtrate adjusting tank outlet pipe 112 communicated with the lower end of the side surface of the dewatering filtrate adjusting tank, the dewatering filtrate adjusting tank 11 is communicated with an alkali liquor input pipe, the other end of the alkali liquor input pipe is communicated with a device for providing alkali liquor, and further, the device for providing alkali liquor can be an alkali liquor storage tank 13.

As the dehydration filtrate of the plate-and-frame filtration system is characterized by high density, high viscosity, high ammonia nitrogen and high suspended matters (the content of suspended matters is 4000-5000mg/L), the high-content suspended matters are difficult to precipitate and separate through a common sedimentation tank, the existing high-efficiency sedimentation tank is difficult to bear overhigh sludge load, and in addition, the inclined pipe area of the high-efficiency sedimentation tank can be polluted and blocked. Therefore, the sedimentation tank designed by the invention is improved based on the core principle of the efficient sedimentation tank and combined with engineering practice, removes the inclined pipe and is used for treating high-suspended-matter sewage with poor settleability.

The sludge after thermal hydrolysis and anaerobic digestion needs to be added with ferric salt/lime and PAM before dehydration to improve the dehydration property of the sludge, so that the dehydration filtrate contains ferric ions with higher concentration, the hardness of the dehydration filtrate is also higher, and simultaneously a large amount of bicarbonate radical is also contained. Therefore, the dewatering filtrate adjusting tank 11 is communicated with an alkali liquor storage tank 13, and the dewatering filtrate adjusting tank 11 is added with alkali liquor to treat iron ions and bicarbonate radicals in the dewatering filtrate.

Further, a pH meter is arranged in the dewatering filtrate adjusting tank 11, and the pH value of the dewatering filtrate in the dewatering filtrate adjusting tank 11 is detected by the pH meter. The bottom of the dewatering filtrate regulating reservoir 11 is equipped with a first submersible mixer 113, and the mixing propeller of the first submersible mixer 113 is a three-blade propeller type mixing propeller to ensure the homogeneity of the dewatering filtrate and prevent the suspended matters from settling in the regulating reservoir.

The coagulation tank 12 is communicated with the first sedimentation tank 6 through a coagulation tank water outlet pipe 121 arranged at the bottom of the coagulation tank 12, a coagulation stirrer 122 is arranged in the coagulation tank 12, and a stirring paddle at the lower end of the coagulation stirrer 122 extends into the coagulation tank 12 and is close to the bottom of the coagulation tank 12; a coagulant adding barrel 14 is arranged above the coagulation tank 12, and the coagulant adding barrel 14 is communicated with the coagulation tank 12 through a coagulant adding pipe 141 communicated with the bottom surface of the coagulant adding barrel.

Further, the first sedimentation tank 6 comprises a tank body 61, a guide cylinder 62 arranged in the tank body 61, and a flow stabilization cylinder 63 sleeved outside the upper end of the guide cylinder 62, the tank body 61 is divided into a flocculation region and a sedimentation region by the guide cylinder 62 and the flow stabilization cylinder 63, the areas in the guide cylinder 62 and the flow stabilization cylinder 63 are the flocculation region, and the areas outside the guide cylinder 62 and the flow stabilization cylinder 63 in the tank body 61 are the sedimentation region.

The guide cylinder 62 of the flocculation area comprises a cylindrical guide cylinder body and a horn mouth fixedly arranged at the upper end of the guide cylinder body, and the horn mouth is positioned in the flow stabilizing cylinder 63. Be provided with axial flow agitator 621 and the level setting in draft tube 62 inside upper end flocculating agent throw ring 622, axial flow agitator 621 and draft tube 62 coaxial setting, axial flow agitator 621's (mixing) shaft downwardly extending, its lower extreme rigid coupling has axial-flow type stirring paddle 6211, and axial flow agitator 621's axial-flow type stirring paddle 6211 sets up in the lower part of flocculating agent throw ring 622, flocculating agent is thrown to the sewage of flocculating zone in the setting of flocculating agent throw ring 622 and is convenient for throw the flocculating agent into, the bottom and the settling zone intercommunication of draft tube 62. As shown in fig. 2, the draft tube 62 is communicated with the coagulation tank 12 through a coagulation tank outlet pipe 121, and the effluent in the coagulation tank 12 enters the draft tube 62 through the coagulation tank outlet pipe 121; the bottom of the guide cylinder 62 is communicated with a first sludge return pipe 623, the bottom of the guide cylinder 62 is communicated with the coagulation tank 12 through the first sludge return pipe 623, a first sludge return pump is arranged on the first sludge return pipe 623, and part of sludge in the sedimentation area flows back to the coagulation tank 12 through the first sludge return pipe 623.

Preferably, the first sludge reflux pump can adopt a positive displacement eccentric single screw pump, and the external reflux ratio is 5%.

After the dehydration filtrate enters the coagulation tank 12, adding alkali liquor into the coagulation tank 12, under the alkaline condition, iron ions and carbonate ions in the dehydration filtrate exist in a form of precipitation, simultaneously, under the action of a coagulant, fine alum flocs are formed after processes such as destabilization, point neutralization, adsorption bridging and the like are carried out on solid suspended matters in the dehydration filtrate, the fine alum flocs and ferric hydroxide and the like enter the first sedimentation tank 6 together, after entering a flocculation area of the first sedimentation tank 6, flocculation of sludge colloidal particles in the dehydration filtrate is accelerated under the action of a flocculating agent, sludge flocculating constituents are formed, the sludge flocculating constituents are separated from water after gravity sedimentation, and the sludge flocculating constituents are settled in a sedimentation area at the bottom of the first sedimentation tank 6. Meanwhile, the structure of the axial-flow type stirring blade 6211 of the axial-flow type stirrer 621 and the low-speed rotation of the axial-flow type stirring blade 6211 make the sludge colloid particles in the water collide, adsorb and gradually form larger sludge floccules, thereby improving the solid-liquid separation effect of the settling zone; in addition, the propeller axial flow design of the axial flow type stirring blade 6211 has the advantages of high liquid discharge capacity and low energy consumption.

As shown in fig. 3, the settling zone includes a tank body 61 and a thickening mud scraper 613 disposed at the upper portion of the center of the tank body 61, the tank body 61 includes a cylindrical tank side wall 614, a large-upper and small-lower inverted truncated cone-shaped tank bottom wall 615 disposed at the bottom of the tank side wall 614, and a mud collecting tank 616 communicated with the bottom of the tank side wall 614, and the bottom of the guide cylinder 62 extends into the mud collecting tank 616. As shown in fig. 2 and fig. 3, the upper part of the tank sidewall 614 is communicated with a water outlet tank 612, one side of the water outlet tank 612 is communicated with a first-stage sedimentation tank water outlet pipe 6121, one side of the tank bottom wall 615 is communicated with a first-stage sedimentation tank sludge discharge pipe 611, and the other end of the first-stage sedimentation tank sludge discharge pipe 611 is communicated with a sludge treatment system.

The concentration mud scraper 613 comprises a main shaft vertically arranged above the tank body 61, a horizontally arranged beam 6133 fixedly connected with the lower end of the main shaft, a plurality of connecting arms 6135 fixedly connected with the lower surface of the beam 6133, a mud scraper 6134 fixedly connected with the other end of the connecting arms 6135, and a mud scraper fixedly connected with the lower end face of the mud scraper 6134, wherein the mud scraper is attached to the inner surface of the bottom wall 615 of the tank, and the upper end of the main shaft is connected with a central driving device for driving the main shaft to rotate.

When the flocs in the dewatering filtrate settle at the bottom wall 615 of the tank, the concentration scraper 613 is activated to concentrate the sediment in the sludge collection tank 616 by the scraper. One part of sludge settled at the bottom of the first sedimentation tank 6 flows back to the coagulation tank 12 from a sedimentation area to realize internal reflux of the sludge, the inlet water of the dehydration filtrate in the coagulation tank 12 is fully mixed with the internal reflux sludge to generate efficient flocculation reaction and net catching effect, larger and denser sludge floc which is not easy to break is generated, the adding amount of a flocculating agent is saved, the effluent quality is improved, and the settleability of the sludge is improved; the other part of the sludge is discharged through a primary sedimentation tank sludge discharge pipe 611 arranged at the lower end of the first sedimentation tank 6. Further, a sludge discharge pump is arranged on the sludge discharge pipe 611 of the primary sedimentation tank, and sludge in the sedimentation zone is pumped out of the first sedimentation tank 6; the central driving system of the concentration mud scraper 613 is provided with a variable frequency adjusting device, and the mud scraper keeps a proper rotating speed during working, so that sludge of floccules is effectively further concentrated and the quality of effluent water is improved. The dehydrated filtrate treated by the first sedimentation tank 6 is finally discharged out of the first sedimentation tank 6 through a water outlet pipe 6121 of the first-stage sedimentation tank.

Furthermore, the sludge discharge pump can adopt a positive displacement eccentric single screw pump, runs discontinuously, and sends out the sludge with the water content of about 98 percent (wt percent) to the sludge treatment system.

Through the treatment of the ammonia distillation pretreatment unit 1, iron ions, bicarbonate radicals and suspended solids in the dehydration filtrate are removed, and then an ammonia nitrogen treatment unit 2 is arranged for removing ammonia nitrogen in the dehydration filtrate.

The ammonia nitrogen treatment unit 2 comprises an intermediate water tank 26 and an ammonia still 21 which are sequentially communicated along the water flow direction.

As shown in fig. 4, the first sedimentation tank 6 is communicated with the intermediate water tank 26 through a first-stage sedimentation tank water outlet pipe 6121, and the dewatering filtrate after flocculation and sedimentation in the first sedimentation tank 6 enters the intermediate water tank 26 through the first-stage sedimentation tank water outlet pipe 6121.

Further, a pH meter is arranged in the intermediate water tank 26 for detecting the pH value of the effluent of the high-efficiency sedimentation tank; meanwhile, the intermediate water tank 26 is communicated with an alkali liquor storage tank 13 for adding alkali liquor.

The downstream of the intermediate water tank 26 is communicated with an intermediate water tank outlet pipe 261, the other end of the intermediate water tank outlet pipe 261 is communicated with an ammonia still inlet pipe 25 communicated with the middle upper part of the ammonia still 21, an ammonia still inlet pump 22 is communicated between the intermediate water tank outlet pipe 261 and the ammonia still inlet pipe 25, and the ammonia still inlet pump 22 is fixedly connected on the horizontal plane at the bottom of the ammonia still 21. The water outlet end of the ammonia still 21 is communicated with an ammonia nitrogen treatment unit water outlet pipe 24.

Specifically, the ammonia still 21 has a treatment capacity of 2000m³D/base, the operation temperature at the top of the tower is 93 ℃, the pressure is 0.01MPa, the operation temperature at the bottom of the tower is 100.4 ℃, and the pressure is 0.03 MPa.

Further, a methane heating furnace (not shown) is disposed at the lower end of the ammonia still 21 to heat the ammonia still 21. The dehydrated filtrate is pumped into the ammonia still 21 through an ammonia still water inlet pump 22 arranged on a water outlet pipe 261 of the middle water tank after coming out of the middle water tank 26, suspended matters are removed after passing through a filter (not shown in the figure) arranged at a water inlet of the ammonia still 21 before the dehydrated filtrate enters the ammonia still 21, and then alkali liquor is added after being preheated to 93 ℃ after passing through a heat exchanger (not shown in the figure) arranged at a water outlet end of the filter and enters the ammonia still 21 through a water inlet pipe 25 of the ammonia still. The ammonia in the dehydrated filtrate reacts with the alkali liquor to generate ammonium hydroxide, the ammonium hydroxide is decomposed into ammonia water by heat, and the ammonia water are separated in the ammonia still 21. Wherein, the filtering and preheating operation before the dehydrated filtrate enters the ammonia still 21 is well known by those skilled in the art and will not be described herein.

As described above, the ammonia and the water vapor in the ammonia still 21 rise to the top of the ammonia still 21 and are cooled under the condition that the ammonia still 21 is continuously heated by the biogas heating furnace, and finally 20% (wt,%) ammonia water is obtained and stored for later use. The operations of condensing, cooling, and storing ammonia and water vapor are well known to those skilled in the art and will not be described in detail herein. The dehydration filtrate containing the sludge sinks to the bottom of the ammonia still 21 under the action of gravity, and the ammonia still effluent, namely the dehydration filtrate treated by ammonia nitrogen removal, is obtained after the operation of temperature reduction and cooling. The cooling operation of the bottom dewatering filtrate is well known to those skilled in the art and will not be described in detail herein.

The dehydrated filtrate after the ammonia nitrogen removal treatment still has 700mg/L of nitrate nitrogen to be treated, so a nitrate nitrogen treatment unit 3 is arranged. As shown in fig. 5, the nitrate nitrogen treatment unit 3 includes a primary BFR anoxic reaction tank 31 and a secondary BFR anoxic reaction tank 32 which are communicated; preferably, a water distribution well 34 is communicated with the upstream of the first-stage BFR anoxic reaction tank 31, the water distribution well 34 is communicated with the ammonia distillation tower 21 through an ammonia nitrogen treatment unit water outlet pipe 24, except that the dehydration filtrate enters the nitrate nitrogen treatment unit 3 through the water distribution well 34, other source water to be treated can also enter the nitrate nitrogen treatment unit 3 after being communicated with the water distribution well 34 for nitrate nitrogen treatment.

A special denitrification biological filler 311 is added in the first-stage BFR anoxic reaction tank 31, so that rich biomass with extremely high activity exists in a two-stage denitrification system; the second submersible stirrer 312 is installed in the first-stage BFR anoxic reaction tank 31 to ensure that the denitrification biological filler 311 is in a suspended state, and preferably, the blades of the second submersible stirrer 312 are all processed by lining with rubber to avoid the metal blades from damaging the denitrification biological filler 311.

Further, the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 are communicated with a sodium acetate adding tank 33 and an acid liquor tank 35. The sodium acetate adding tank 33 is respectively communicated with the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 through a sodium acetate outlet pipe 331 communicated with the sodium acetate adding tank; the acid liquor tank 35 is respectively communicated with the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 through an acid liquor outlet pipe 351 communicated with the acid liquor tank.

The second-stage BFR anoxic reaction tank 32 is connected with the first-stage BFR anoxic reaction tank 31 in an abutting mode, a backflow device is arranged between the second-stage BFR anoxic reaction tank 32 and the first-stage BFR anoxic reaction tank 31, further, the backflow device is a large-flow low-lift wall-penetrating pump arranged on a wall shared by the second-stage BFR anoxic reaction tank 32 and the first-stage BFR anoxic reaction tank 31, furthermore, the wall-penetrating pump realizes that dehydration filtrate with about 10 times of water inflow in the second-stage BFR anoxic reaction tank 32 flows back to the first-stage BFR anoxic reaction tank 31, and directly dilutes nitrate nitrogen with 700mg/L of inflow water to be below 105mg/L, so that the reaction gradient of the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 is greatly reduced, and the important guarantee that the effluent nitrate nitrogen is lower than 45mg/L is achieved.

In the operation process of the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32, sodium acetate is continuously added into the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32, and acetic acid (radicals) is used as an important carbon source, is one of the carbon sources which enable the denitrification rate of microorganisms to be highest, and is an important guarantee that the nitrate nitrogen of effluent is lower than 45 mg/L. Meanwhile, an Oxygen Reduction Potential (ORP) meter and a sodium acetate dosing metering pump are arranged on the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32, so that the ORP value of the water solution in the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 is controlled to be always within the optimal ORP range of the denitrification reaction.

Because the most suitable pH range of the denitrification process is 7-8, the pH value of the effluent of the ammonia nitrogen treatment unit 2 is about 8.5, and the denitrification process continuously generates alkalinity, so that the pH value is increased, acid liquor is added into the first-level BFR anoxic reaction tank 31 and the second-level BFR anoxic reaction tank 32, meanwhile, a pH meter and an acid adding metering pump are respectively arranged on the first-level BFR anoxic reaction tank 31 and the second-level BFR anoxic reaction tank 32, and the dehydration filtrate in the first-level BFR anoxic reaction tank 31 and the second-level BFR anoxic reaction tank 32 is in the suitable pH range by adjusting the adding amount of the acid liquor.

Further, filter screen cylinders are arranged at the tail ends of the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32 to prevent the denitrification biological filler 311 from flowing out of the anoxic reaction tanks.

After the treatment of the nitrate nitrogen treatment unit 3, the indexes of ammonia nitrogen and total nitrogen in the sewage reach the standards, and then a COD treatment unit 4 is arranged, which aims to treat COD in the dehydrated filtrate.

As shown in fig. 6, the COD processing unit 4 comprises a first-stage BFR aerobic reaction tank 41, a second sedimentation tank 44, an ozone catalytic oxidation unit 42, a second-stage BFR aerobic reaction tank 43, and a third sedimentation tank 45, which are sequentially communicated. The primary BFR aerobic reaction tank 41 and the secondary BFR anoxic reaction tank 32 are adjacently communicated (refer to fig. 5), the downstream of the primary BFR aerobic reaction tank 41 is communicated with a primary aerobic tank water outlet pipe 412, the primary BFR aerobic reaction tank 41 is communicated with the second sedimentation tank 44 through the primary aerobic tank water outlet pipe 412, the water outlet end of the second sedimentation tank 44 is connected with a secondary sedimentation tank water outlet pipe 441, the other end of the secondary sedimentation tank water outlet pipe 441 is connected with the ozone catalytic oxidation unit 42, the ozone catalytic oxidation unit 42 is communicated with the secondary BFR aerobic reaction tank 43 through an ozone unit water outlet pipe 4231 communicated with the downstream, the water outlet end of the secondary BFR aerobic reaction tank 43 is communicated with a secondary aerobic tank water outlet pipe 431, and the secondary BFR aerobic reaction tank 43 is communicated with the third sedimentation tank 45 through the secondary aerobic tank water outlet pipe 431.

The filler in the first-stage BFR aerobic reaction tank 41 is powdered activated carbon and activated sludge, the activated sludge contains microorganisms for degrading COD, and the powdered activated carbon can adsorb toxic organic matters and heavy metals; meanwhile, COD degrading microorganisms are added into the first-stage BFR aerobic reaction tank 41, and biological treatment is carried out on organic matters in the dehydration filtrate. The powdered activated carbon and the microorganisms are used together, firstly, after the powdered activated carbon adsorbs pollutants in the dehydration filtrate, longer treatment time for the dehydration filtrate is provided for the microorganisms, and the treatment time is prolonged from the hydraulic retention time to the mud age (the mud age is far longer than the hydraulic retention time); secondly, the powdered activated carbon can adsorb toxic organic matters and heavy metals, reduce the impact of organic pollutants, can be used as a microorganism growth carrier, protect sensitive microorganisms, greatly promote the biological phase in a biochemical reaction tank and enable a biochemical system to achieve higher treatment efficiency; in addition, the microorganisms degrade the pollutants to generate carbon dioxide, water and new microorganism cells, and the nondegradable pollutants still stay on the powdered activated carbon, so that the quality of the effluent is ensured.

An aeration head is arranged at the bottom of the primary BFR aerobic reaction tank 41, the aeration head is communicated with an aeration pipe 411, and the other end of the aeration pipe 411 is communicated with a blower; a DO dissolved oxygen meter for controlling the oxygen supply amount in the first-stage BFR aerobic reaction tank 41 is arranged in the first-stage BFR aerobic reaction tank 41 and is matched with an aerator for use.

The difference between the secondary BFR aerobic reaction tank 43 and the primary BFR aerobic reaction tank 41 is that the secondary BFR aerobic reaction tank 43 is communicated with a powdered activated carbon feeding device 432, and brand new powdered activated carbon is fed into the secondary BFR aerobic reaction tank 43 through the powdered activated carbon feeding device 432.

The second-stage BFR aerobic reaction tank 43 is directly communicated with the first-stage BFR aerobic reaction tank 41 through a carbon return pipe 433 arranged at the bottom of the second-stage BFR aerobic reaction tank, the powdered activated carbon filler in the second-stage BFR aerobic reaction tank is returned to the first-stage BFR aerobic reaction tank 41, the filler added in the second-stage BFR aerobic reaction tank 43 is brand-new powdered activated carbon every time, and the brand-new powdered activated carbon is introduced into the first-stage BFR aerobic reaction tank 41 for secondary utilization after being used. The advantage of the arrangement is that the adsorption isotherm principle of the powdered activated carbon shows that the higher the concentration of the organic pollutants is, the larger the adsorption amount of the powdered activated carbon is, the more the powdered activated carbon reaches the adsorption balance in the secondary BFR aerobic reaction tank 43, and the powdered activated carbon still can adsorb a large amount of pollutants after entering the primary BFR aerobic reaction tank 41, so that the use amount of the powdered activated carbon is greatly reduced, and the quality of effluent water is effectively ensured because the brand-new powdered activated carbon with the strongest adsorption capacity is added into the secondary BFR aerobic reaction tank 43.

Because the wet density of the powdered activated carbon is larger, flocs formed by the powdered activated carbon and the activated sludge are easier to precipitate, but if a common sedimentation tank is adopted, very fine powdered activated carbon or sludge particles are easy to appear in effluent or on the surface of the tank, and the effluent quality or the treatment efficiency of ozone catalytic oxidation is influenced. Therefore, the second sedimentation tank 44 and the third sedimentation tank 45 are both arranged in the same structure as the first sedimentation tank 6, and are not described in detail herein.

The third sedimentation tank 45 is communicated with the first-stage BFR aerobic reaction tank 41 through a third-stage sedimentation tank sludge discharge pipe 452 communicated with the bottom of the third sedimentation tank, and the powdered activated carbon in the second-stage BFR aerobic reaction tank 43 flows back to the first-stage BFR aerobic reaction tank 41, so that the purpose of recycling the powdered activated carbon in the second-stage BFR aerobic reaction tank 43 is achieved. The sludge (powdered activated carbon, sludge, etc.) in the second sedimentation tank 44 is discharged to the sludge treatment system through a secondary sedimentation tank sludge discharge pipe 442 communicated at the bottom thereof.

The second sedimentation tank 44 and the third sedimentation tank 45 realize the internal reflux of the sludge through the unique central flocculation area structure, the inflow water and the internal reflux sludge are fully mixed and divided, the high-efficiency flocculation reaction and the net catching effect are generated, very fine powdered activated carbon or sludge particles are effectively removed, larger, more compact and difficult-to-break sludge flocs are generated, and the settleability and the effluent quality of the sludge are effectively improved.

As shown in fig. 1 and 7, the catalytic ozonation unit 42 includes an ozone generator (not shown), which provides a source of ozone, an ozone contact oxidation tank 422, which is in communication with the ozone generator, and an ozone degassing tank 423, which is in communication with the ozone contact oxidation tank 422, the ozone contact oxidation tank 422 is in communication with the second sedimentation tank 44, and the ozone degassing tank 423 is in communication with the secondary BFR aerobic reaction tank 43 through an ozone unit water outlet pipe 4231.

The structure of the ozone generator 421 is well known to those skilled in the art and will not be described herein.

Three groups of guide plates are arranged in the ozone contact oxidation tank 422 along the water flow direction, and the three groups of guide plates divide the ozone contact oxidation tank 422 into four areas; each group of guide plates comprises a first guide plate 4224 and a second guide plate 4225 which are vertically arranged at intervals, the upper end surface of the first guide plate 4224 is fixedly connected with the top surface of the ozone contact oxidation tank 422, and the lower end surface of the first guide plate 4224 extends downwards to the bottom surface of the ozone contact oxidation tank 422 and has a certain distance with the bottom surface of the ozone contact oxidation tank 422, so that dehydration filtrate can pass through; the lower end surface of the second guide plate 4225 is fixedly connected with the bottom surface of the ozone contact oxidation tank 422, and the upper end surface of the second guide plate 4225 upwards extends to the top surface of the ozone contact oxidation tank 422 and has a certain distance with the top surface of the ozone contact oxidation tank 422, so that the dehydration filtrate can pass through. The dehydrated filtrate directionally passes through four zones of the ozone contact oxidation tank 422 in turn under the action of the guide plates.

Furthermore, the first three areas are all provided with a micropore air diffusing head 4222, the micropore air diffusing head 4222 is communicated with an ozone conveying pipe 4221 communicated with an ozone generator, namely pure ozone is adopted to treat dehydrated filtrate, preferably, the micropore air diffusing head 4222 has a uniform structure, the pore diameter of micropores is 1-100um, the porosity is 28-50%, the wall thickness is 2-3mm, and aeration bubbles are 0.1-2 mm; the last zone is added with ozone catalytic packing and is also provided with a perforated pipe 4223 for air diffusion, the perforated pipe 4223 is communicated with an ozone delivery pipe 4221 communicated with an ozone generator, the perforated pipe 4223 for air diffusion penetrates through the ozone catalytic packing and extends to the bottom surface of a fourth zone of the ozone contact oxidation pond 422, and the fourth zone adopts catalytic packing and ozone to jointly treat dehydrated filtrate.

The ozone degassing tank 423 is provided with a flow guide wall 4232, the flow pushing type is adopted to ensure that the ozone content of the effluent is the lowest, and the ozone degassing tank 423 is communicated with the secondary BFR aerobic reaction tank 43 through an ozone unit water outlet pipe 4231.

Further, excess ozone in ozone degasser 423 is sent to an exhaust destruction system for further treatment.

As shown in fig. 1, the dehydrated filtrate finally passing through the COD treatment unit 4 is discharged to the clear water outlet tank 5, and the clear water outlet tank 5 is communicated with a third-stage sedimentation tank outlet pipe 451 communicating with the downstream of the third sedimentation tank 45.

The sewage to be treated is plate-frame filtered water generated after anaerobic digestion of sludge in a sewage plant, and the treatment scale of the plate-frame filtered water generated after anaerobic digestion of the sludge in the sewage plant is 2000m³The water quality indexes of the plate-frame filtered water are shown in table 1:

TABLE 1 Water quality parameter Table of plate-and-frame filtered water produced by anaerobic digestion of sludge from sewage plants

Item	Quality of incoming water	Emission index
			CODcr/(mg/L)	1000-3000	≤300
BOD5/(mg/L)	550-800	≤150
			TN/(mg/L)	3200	≤70
NH₃-N/(mg/L)	2500	≤25
			TP/(mg/L)	70-100	-
pH	6-9	6-9
			SS/(mg/L)	4000-5000	-

Wherein CODcr is the chemical oxygen consumption measured by using potassium dichromate (K2Cr2O7) as an oxidant, namely the dichromate index; BOD5 is biological oxygen demand, which refers to the amount of dissolved oxygen consumed in a biochemical reaction process in which microorganisms break down biodegradable organic matter present in water under certain conditions; TN is the total nitrogen content; NH (NH)₃-N is the ammonia nitrogen content; TP is total phosphorus content; SS is solid suspension.

A method for treating a dewatering filtrate after anaerobic digestion of sludge, in this embodiment, a process for treating a dewatering filtrate after anaerobic digestion of sludge is implemented based on the above-mentioned system for treating a dewatering filtrate after anaerobic digestion of sludge, and with reference to fig. 8, specifically includes the following steps:

the sludge anaerobic digestion dehydration filtrate passing through the plate-and-frame filtration system is sequentially introduced into a dehydration filtrate adjusting tank 11, a coagulation tank 12 and a first sedimentation tank 6;

in the process, alkali liquor is added into the dehydration filtrate regulating tank 11, the pH value of the dehydration filtrate is regulated to 8, stirring is carried out for 25.35 hours, the dehydration filtrate is ensured to be homogeneous in the process, and suspended matters are prevented from being precipitated in the dehydration filtrate regulating tank 11. After the alkali liquor is added, the bicarbonate radical in the dehydration filtrate is converted into carbonate radical, and the carbonate radical is combined with calcium ions to generate calcium carbonate precipitate, so that the hardness of the dehydration filtrate is reduced; meanwhile, iron ions in the dehydration filtrate are converted into ferric hydroxide precipitate, and colloid in the dehydration filtrate is destabilized by the existence of ferric salt to form floc, which is beneficial to removing COD; and the density of the ferric hydroxide is high, which is beneficial to improving the integral settleability of the sludge floc.

And (3) introducing the dehydration filtrate containing the flocs into a first sedimentation tank 6, adding a flocculating agent PAM into the first sedimentation tank 6, wherein the addition amount of the PAM refers to the prior art, and the dehydration filtrate is further flocculated under the action of the PAM and is precipitated in a precipitation area below a guide cylinder 62 of the first sedimentation tank 6 under the action of gravity to form sludge precipitation. A part of sludge sediment flows back to the coagulation tank 12 through the first sludge return pipe 623 and is fully mixed with the inlet water of the dehydration filtrate to generate high-efficiency flocculation reaction and net capture effect, so that larger and denser sludge floc which is not easy to break is generated, and flocculation is promoted; the other part of the sludge with the water content of 98 percent is discharged through a sludge discharge pipe 611 of the primary sedimentation tank.

The dehydrated filtrate treated by the ammonia distillation pretreatment unit 1 is discharged through a water outlet pipe 6121 of the first-stage sedimentation tank in the first sedimentation tank 6.

The dehydration filtrate after being treated by the ammonia distillation pretreatment unit 1 is introduced into an intermediate water tank 26, after alkali liquor is added into the intermediate water tank 26, high ammonia nitrogen wastewater in the intermediate water tank 26 is boosted to a filter through an ammonia tower water inlet pump 22, then suspended matters in the inlet water are removed through filtration, the wastewater enters a feeding heat exchanger for heat exchange, and after the temperature is raised to 93 ℃, the wastewater is fully mixed with the injected alkali liquor, and the form of the ammonia in the water changes:

NaOH+NH₄ ⁺→Na⁺+NH₄OH，

NH₄OH→NH₃+H₂O。

the raw material water enters the middle upper part of the ammonia tower, and NH is carried out in the ammonia tower₃And separation of water: the material at the tower top is mixed gas of ammonia and water, and ammonia water containing 20% (wt%) of ammonia is obtained after the material is condensed at the tower top and stored for later use.

The dehydrated filtrate containing the sludge moves to the bottom of the tower under the action of gravity, a heat source is provided by a methane heating furnace at the bottom of the tower, the wastewater at the bottom of the tower is cooled to 35 ℃ and then is discharged out of the device, the ammonia nitrogen content of the dehydrated filtrate is reduced to 50mg/L, and the pH value is 8.5.

After ammonia nitrogen is treated by an ammonia distillation system, 700mg/L of nitrate nitrogen still needs to be treated in the sludge anaerobic digestion dehydration filtrate.

And (2) putting the dehydration filtrate subjected to ammonia nitrogen treatment into a water distribution well 34 for water distribution, then introducing the sludge anaerobic digestion dehydration filtrate into a first-stage BFR anoxic reaction tank 31 and a second-stage BFR anoxic reaction tank 32 which are adjacently communicated, controlling the pH range of the denitrification process to be 7-8, and controlling the ORP range of the denitrification process to be-100 to +100 mV. Simultaneously starting a wall-through pump arranged on a common wall body of the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32, and refluxing dehydration filtrate with 10 times of water inflow flow in the second-stage BFR anoxic reaction tank 32 into the first-stage BFR anoxic reaction tank 31 to ensure that 700mg/L of nitrate nitrogen of the inflow water is directly diluted to be below 105 mg/L; in addition, sodium acetate is added into the first-stage BFR anoxic reaction tank 31 and the second-stage BFR anoxic reaction tank 32, the addition amount of the sodium acetate refers to the prior art, and the addition of the sodium acetate efficiently promotes the denitrification process of microorganisms. The final ammonia nitrogen content of the effluent is lower than 25mg/L, the nitrate nitrogen content is lower than 45mg/L, and the total nitrogen content is lower than 70 mg/L.

In the COD treatment unit of the sludge anaerobic digestion dehydration filtrate, the dehydration filtrate after nitrate nitrogen treatment passes through a primary BFR aerobic reaction tank 41, an ozone contact oxidation tank 422, an ozone degassing tank 423 and a secondary BFR aerobic reaction tank 43 in turn. The powdery activated carbon added in both the first-stage BFR aerobic reaction tank 41 and the second-stage BFR aerobic reaction tank 43 adsorbs COD in the dehydrated filtrate, and microorganisms for treating COD in the powdery activated carbon decompose organic matters and the like in the dehydrated filtrate. And in the period, the pH values of the dehydration filtrate of the primary BFR aerobic reaction tank 41 and the secondary BFR aerobic reaction tank 43 are controlled to be 7-8, and the dissolved oxygen in the tanks is more than or equal to 2 mg/L.

The sludge anaerobic digestion dehydration filtrate passes through a first-stage BFR aerobic reaction tank 41 and then passes through a second sedimentation tank 44 to carry out flocculation sedimentation, and a third sedimentation tank 45 arranged behind a second-stage BFR aerobic reaction tank 43 is used for secondary flocculation sedimentation. In the process, the residual sludge (with the water content of about 98%) containing the powdered activated carbon in the secondary BFR aerobic reaction tank 43 flows back to the primary BFR aerobic reaction tank 41, and the sludge reflux ratio is 100-50%; and the residual sludge (the water content is about 98%) containing powdered activated carbon in the primary aerobic biochemical system is taken as waste sludge and sent out to a sludge treatment system.

And finally, introducing the dehydrated filtrate subjected to the COD treatment into a clear water outlet pool 5 to obtain final outlet water.

The quality of the inlet water of each unit and the quality of the outlet water of each unit of the process flow after the sludge anaerobic digestion dehydration filtrate is treated by each unit are shown in table 2:

table 2 effluent quality of each unit of process flow

Wherein CODcr is potassium dichromate (K)₂Cr₂O₇) Chemical oxygen demand, i.e. dichromate index, measured as oxidant; BOD5 is the biological oxygen demand, i.e. the amount of dissolved oxygen consumed in a biochemical reaction process in which microorganisms break down biochemically degradable organic matter present in water under certain conditions; TN is total nitrogen content; NH (NH)₃-N is the ammonia nitrogen content; TP is total phosphorus content; SS is solid suspension.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Claims

1. A system for treating dehydrated filtrate after anaerobic digestion of sludge is characterized by comprising an ammonia evaporation pretreatment unit (1), an ammonia nitrogen treatment unit (2), a nitrate nitrogen treatment unit (3) and a COD treatment unit (4) which are sequentially communicated along the flow direction of the dehydrated filtrate;

the ammonia distillation pretreatment unit (1) comprises a dehydration filtrate adjusting tank (11), a coagulation tank (12) and a first sedimentation tank (6) which are sequentially communicated, wherein the dehydration filtrate adjusting tank (11) is communicated with an alkali liquor input pipe, the other end of the alkali liquor input pipe is communicated with a device for providing alkali liquor, and the device for providing alkali liquor is an alkali liquor storage tank (13);

the ammonia nitrogen treatment unit (2) comprises an intermediate water tank (26) and an ammonia still (21) which are sequentially communicated along the water flow direction, the first sedimentation tank (6) is communicated with the intermediate water tank (26), and the intermediate water tank (26) is communicated with an alkali liquor storage tank (13) for adding alkali liquor; the ammonia still (21) is communicated with an ammonia still water inlet pipe (25), and the ammonia still water inlet pipe (25) is communicated with an alkali liquor input pipe;

the nitrate nitrogen treatment unit (3) comprises a primary BFR anoxic reaction tank (31) and a secondary BFR anoxic reaction tank (32) which are communicated, denitrification biological fillers (311) are added in the primary BFR anoxic reaction tank (31) and the secondary BFR anoxic reaction tank (32), and a reflux device is arranged between the primary BFR anoxic reaction tank (31) and the secondary BFR anoxic reaction tank (32);

the COD treatment unit (4) comprises a primary BFR aerobic reaction tank (41), an ozone catalytic oxidation unit (42) and a secondary BFR aerobic reaction tank (43) added with powdered activated carbon, wherein the primary BFR aerobic reaction tank (41), the ozone catalytic oxidation unit and the secondary BFR aerobic reaction tank are sequentially communicated, and a carbon return pipe (433) communicated with the primary BFR aerobic reaction tank (41) is arranged on the secondary BFR aerobic reaction tank (43);

refluxing the dehydrated filtrate in the secondary BFR anoxic reaction tank (32) to the primary BFR anoxic reaction tank (31) by taking the water inflow rate of 10 times as the reflux amount; refluxing the sludge containing the powdered activated carbon in the secondary BFR aerobic reaction tank (43) to the primary BFR aerobic reaction tank (41) by taking 100-150% of the feeding amount as the reflux amount;

the downstream of the primary BFR aerobic reaction tank (41) is communicated with a second sedimentation tank (44), the downstream of the secondary BFR aerobic reaction tank (43) is communicated with a third sedimentation tank (45), the sludge outlet end of the third sedimentation tank (45) is communicated with the primary BFR aerobic reaction tank (41), the water outlet end of the third sedimentation tank (45) is communicated with a clear water outlet tank (5), and the sludge outlet end of the second sedimentation tank (44) is communicated with a sludge treatment system;

the first sedimentation tank (6) comprises a tank body (61) and a guide flow cylinder (62) arranged in the tank body (61), the tank body is divided into a flocculation area and a sedimentation area by the guide flow cylinder (62), the area in the guide flow cylinder (62) is the flocculation area, and the area outside the guide flow cylinder (62) in the tank body (61) is the sedimentation area;

the settling zone is provided with concentrated mud scraper (631), cell body (61) are through setting up first mud back flow (623) and coagulation basin (12) intercommunication in its bottom, cell body (61) are through setting up one-level sedimentation tank mud pipe (611) and the sludge treatment system intercommunication in its bottom, cell body (61) upper portion intercommunication has outlet basin (612), outlet basin (612) are through setting up one-level sedimentation tank outlet pipe (6121) and ammonia nitrogen treatment unit (2) intercommunication in its one side.

2. The system for treating a dewatering filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: the primary BFR anoxic reaction tank (31) and the secondary BFR anoxic reaction tank (32) are respectively communicated with a sodium acetate adding tank (33).

3. The system for treating a dewatering filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: and filter screen cylinders are arranged at the water outlets at the tail ends of the primary BFR anoxic reaction tank (31) and the secondary BFR anoxic reaction tank (32).

4. The system for treating a dewatering filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: all be provided with second dive mixer (312) in one-level BFR oxygen deficiency reaction pond (31) and second grade BFR oxygen deficiency reaction pond (32), the rigid coupling has the lining glue on the paddle of second dive mixer (312).

5. The system for treating dehydrated filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: the second sedimentation tank (44) and the third sedimentation tank (45) are arranged in the same structure as the first sedimentation tank (6); the second sedimentation tank (44) is communicated with the sludge treatment system through a second-stage sedimentation tank sludge discharge pipe (442) arranged at the bottom of the second sedimentation tank, and the third sedimentation tank (45) is communicated with the first-stage BFR aerobic reaction tank (41) through a third-stage sedimentation tank sludge discharge pipe (452) arranged at the bottom of the third sedimentation tank.

6. The system for treating a dewatering filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: and aeration heads are arranged in the first-stage BFR aerobic reaction tank (41) and the second-stage BFR aerobic reaction tank (43), and are communicated with an aeration pipe (411).

7. The system for treating a dewatering filtrate after anaerobic digestion of sludge as claimed in claim 1, wherein: the ozone catalytic oxidation unit (42) comprises an ozone contact oxidation tank (422) and an ozone degassing tank (423) communicated with the ozone contact oxidation tank (422), wherein the ozone contact oxidation tank (422) is divided into four regions along the water flow direction, the first three regions are provided with microporous gas dispersing heads (4222) communicated with an ozone source through ozone conveying pipes (4221), and the fourth region is provided with gas dispersing perforated pipes (4223) communicated with the ozone source.

8. A method of treating a sludge anaerobic digestion dewatered filtrate treatment system according to claim 1, comprising the steps of:

the dehydration filtrate after anaerobic digestion of the sludge sequentially enters a dehydration filtrate adjusting tank (11), a coagulation tank (12) and a first sedimentation tank (6) of an ammonia distillation pretreatment unit (1), and alkali liquor is added into the dehydration filtrate adjusting tank (11) in the process to generate flocculent precipitate in the dehydration filtrate; adding a coagulant into the coagulation tank (12), and generating floccules in the dehydrated filtrate; adding a flocculating agent into the first sedimentation tank (6), forming flocculating constituents in the dehydrated filtrate, and settling in a settling zone at the lower end of the guide cylinder (62); meanwhile, part of the sediment flows back into the coagulation tank (12) through a first sludge return pipe (623), the other part of the sludge is discharged through a first-stage sedimentation tank sludge discharge pipe (611), and the dehydration filtrate treated by the ammonia evaporation pretreatment unit (1) is discharged through a first-stage sedimentation tank water outlet pipe (6121), so that the ammonia evaporation pretreatment is completed;

introducing the dehydrated filtrate discharged from a water outlet pipe (6121) of the primary sedimentation tank into an ammonia still (21), and removing ammonia nitrogen to obtain dehydrated filtrate of the ammonia nitrogen;

introducing the dehydrated filtrate subjected to ammonia nitrogen treatment into a first-stage BFR anoxic reaction tank (31) and a second-stage BFR anoxic reaction tank (32), controlling the pH value and ORP value in the denitrification process, performing denitrification nitrogen treatment, and starting a reflux device;

the dehydrated filtrate after denitration nitrogen treatment is sequentially led into a first-stage BFR aerobic reaction tank (41), a second sedimentation tank (44), an ozone catalytic oxidation unit (42), a second-stage BFR aerobic reaction tank (43) and a third sedimentation tank (45) for COD treatment; in the process, the sludge containing powdered activated carbon in the secondary BFR aerobic reaction tank (43) flows back to the primary BFR aerobic reaction tank (41), and the sludge in the primary BFR aerobic reaction tank (41) is conveyed to a sludge treatment system; introducing the dehydrated filtrate subjected to COD treatment into a clear water outlet pool (5) to obtain final outlet water.

9. The method for treating the dewatering filtrate after the anaerobic digestion of the sludge according to the claim 8, characterized in that the dewatering filtrate in the secondary BFR anoxic reaction tank (32) is internally refluxed into the primary BFR anoxic reaction tank (31) with the 10 times of water inlet flow as reflux.

10. The method for treating the dewatered filtrate after anaerobic digestion of sludge as claimed in claim 8, wherein the sludge containing powdered activated carbon in the secondary BFR aerobic reaction tank (43) is refluxed into the primary BFR aerobic reaction tank (41) with a feed rate of 100-150% as a reflux rate.