Advanced treatment method for municipal sludge wastewater

Abstract

A municipal sludge wastewater advanced treatment method comprises the following steps: feeding municipal sludge wastewater into a grating well through a pipeline, and then feeding the municipal sludge wastewater into a comprehensive regulating reservoir; comprehensively adjusting in a comprehensive adjusting tank, and then pumping into a high-precision self-cleaning filter; filtering in a high-precision self-cleaning filter, and feeding into a pH regulation reaction tank; after the pH value is adjusted in the pH adjusting reaction tank, the wastewater enters the coagulation reaction tank; after the reaction in the coagulation reaction tank, the wastewater enters a flocculation reaction tank, after the reaction, the wastewater enters a sedimentation tank, and supernate of the sedimentation tank enters an intermediate water tank; pumping to a pulse water distributor in the middle water tank, uniformly distributing water to a hydrolysis acidification tank by the pulse water distributor, treating, and entering a two-stage AO tank; the treated wastewater enters a tubular ultrafiltration membrane; after mud-water separation by the tubular ultrafiltration membrane, entering a clean water tank; the method is scientific and reasonable, the combined method is adopted for treating the municipal sludge deep treatment wastewater, the system operation cost is reduced to the maximum extent, the treatment effect is good, the efficiency is high, and remarkable social and economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, in particular to a method for deep treatment of municipal sludge wastewater. Background Art

[0002] With the development of urban industrialization and the construction of large-scale urban sewage treatment plants, the issue of sludge resource utilization in urban sewage treatment plants has become increasingly urgent. At present, most cities deeply dehydrate municipal sludge and then incinerate it with domestic waste to generate electricity to maximize the utilization of sludge resources. However, the wastewater generated by deep dehydration of municipal sludge still does not meet the emission standards and needs to be treated before discharge.

[0003] In order to pursue a higher dehydration rate, municipal sludge deep treatment often adds a large amount of modifying agents to destroy the sludge cell structure, and reduces the sludge water content through mechanical extrusion and drying equipment so that it can enter the incinerator for incineration. The wastewater generated during the dehydration and drying process often contains a large amount of agents. The wastewater has a high level of suspended particles, high molecular polymers and other difficult-to-degrade substances, poor biodegradability, and is difficult to treat.

[0004] At present, the methods for deep treatment of municipal sludge wastewater include "coagulation", "biochemical method", "electrocatalytic oxidation method" and "Fenton advanced oxidation method". Among them, the coagulation method has a general treatment effect, which is not enough to meet the emission standards and requires deep treatment. The electrocatalytic oxidation method and Fenton advanced oxidation method have good effects, but their energy consumption and operating costs are high, which are not the best choice. The biochemical method has limitations, and the single biochemical method has low treatment efficiency. Therefore, it is necessary to further improve and innovate the existing methods for treating municipal sludge wastewater, but there has been no relevant public reports so far. Summary of the invention

[0005] In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a method for deep treatment of municipal sludge wastewater, which can effectively solve the problems of high treatment cost, low treatment efficiency and failure to meet discharge requirements in the existing treatment methods for municipal sludge wastewater.

[0006] To achieve the above object, the technical solution provided by the present invention is a method for deep treatment of municipal sludge wastewater, comprising the following steps: S1. Send the municipal sludge wastewater into the screen well through the pipeline to separate the large suspended matter, floating matter, fiber matter and solid particulate matter in the wastewater, and the separated wastewater enters the comprehensive regulating tank; S2. The wastewater is comprehensively regulated in the comprehensive regulating tank, and acid and alkali agents are added to roughly adjust the pH value of the wastewater to 6-9. The hydraulic retention is 12-24 hours, and then the regulated wastewater is pumped into the high-precision self-cleaning filter; S3. The wastewater is filtered in a high-precision self-cleaning filter. The high-precision self-cleaning filter uses a 10-300 mesh screen to physically intercept particulate matter in the wastewater. The filtered wastewater enters the pH adjustment reaction tank; S4. The wastewater is subjected to pH adjustment in a pH adjustment reaction tank. The reaction time is 5-10 minutes. The speed of the reduction mixer in the pH adjustment reaction tank is 30-50 r / min. Acid / base is added to the pH adjustment reaction tank to adjust the pH value of the wastewater to 7-8.5. The wastewater after pH adjustment enters a coagulation reaction tank. S5. PAC is added to the coagulation reaction tank at a dosage of 10~50mg / l. The wastewater reacts in the coagulation reaction tank for 5~15min. The speed of the reduction mixer in the coagulation reaction tank is 30~50r / min. The wastewater after the reaction enters the flocculation reaction tank. PAM is added to the flocculation reaction tank at a dosage of 2~5mg / l. The wastewater reacts in the flocculation reaction tank for 5~12min. The speed of the reduction mixer in the flocculation reaction tank is 10~25r / min. After sufficient reaction, it enters the sedimentation tank for mud-water separation. The supernatant of the sedimentation tank flows into the intermediate water tank by gravity. S6. The wastewater is hydraulically retained in the intermediate water tank for 0.5-2 hours, and then pumped to the pulse water distributor by the lifting pump. The pulse water distributor evenly distributes the water to the activated sludge bed at the bottom of the hydrolysis and acidification tank. The wastewater is hydraulically retained for 8-12 hours. Under anaerobic conditions, high-efficiency anaerobic bacteria hydrolyze and acidify the difficult-to-degrade substances in the wastewater. The B / C of the acidified wastewater reaches above 0.3. The wastewater treated in the hydrolysis and acidification tank enters the two-stage AO tank. S7, the two-stage AO pool includes a first anoxic pool, a first aerobic pool, a second anoxic pool and a second aerobic pool which are sequentially connected by pipelines. The wastewater is biologically denitrified by nitrification / denitrification of nitrifying bacteria and denitrifying bacteria in the two-stage AO pool. A carbon source is added to the first anoxic pool and the second anoxic pool, and an alkali solution is added to the first aerobic pool and the second aerobic pool. The wastewater is sequentially reacted in the first anoxic pool for 20-30 hours, the first aerobic pool for 60-90 hours, the second anoxic pool for 10-20 hours, and the second aerobic pool for 20-40 hours, so that the pH value of the wastewater is 7-8, the reaction temperature is controlled at 20-35°C, the redox potential value is controlled at +50--50mV, the dissolved oxygen of the wastewater in the second aerobic pool is controlled at 2-4mg / l, and the treated wastewater enters the tubular ultrafiltration membrane; S8. Wastewater is separated into mud and water by tubular ultrafiltration membrane. The ultrafiltration membrane flux is 50~120L / , and the applicable sludge concentration is 10~50g / l. The filtered wastewater enters the clear water tank and meets the discharge standards. S9, the backwash water of the high-precision self-cleaning filter, the sludge in the sedimentation tank and part of the sludge from the tubular ultrafiltration membrane enter the sludge concentration tank for concentration, and PAM is added to the sludge concentration tank 8 at a dosage of 50-150 mg / l with a molecular weight greater than 12 million. After adjustment, it is pumped into the screw dehydrator for dehydration. The dehydrated sludge is pumped to the municipal sludge deep treatment workshop for deep treatment, and the filtrate is refluxed to the screen well for circulation treatment.

[0007] Furthermore, the comprehensive regulating tank, pH regulating reaction tank, first aerobic tank and second aerobic tank are equipped with online pH meters, the high-precision self-cleaning filter is equipped with a differential pressure sensor, the first anoxic tank and the second anoxic tank are equipped with an ORP analyzer and a temperature controller, the first aerobic tank and the second aerobic tank are equipped with a DO analyzer, and a pressure gauge is installed on the tubular ultrafiltration membrane.

[0008] The screw stacking and dehydrating machine is a 301 type screw stacking and dehydrating machine.

[0009] In step S2, the acid and alkali reagents are dilute sulfuric acid and sodium hydroxide, and in step S7, the carbon source is sodium acetate and the alkali solution is sodium hydroxide.

[0010] The method of the present invention is scientific and reasonable. It adopts the combined method of "high-precision self-cleaning filtration + pH adjustment + coagulation sedimentation + hydrolysis acidification + two-stage AO biochemistry + tubular ultrafiltration membrane" to treat municipal sludge deep treatment wastewater, which can reduce the system operation cost to the greatest extent, has good treatment effect, high efficiency, and significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural connection frame diagram of the present invention. DETAILED DESCRIPTION

[0012] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings and specific circumstances.

[0013] The present invention is specifically described in the following examples.

[0014] A garbage incineration project in a certain city uses domestic garbage and municipal sludge as raw materials for co-incineration. The plant is equipped with a disposal production line that can process 300 tons of municipal sludge (water content 80%) per day. The wastewater comes from the vertical high-pressure plate and frame extrusion wastewater of the sludge disposal production line, the drying wastewater of the disc sludge drying equipment, the workshop floor washing water and the domestic sewage in the plant, etc., with a daily wastewater volume of 200t / d.

[0015] After mixing, the water quality of the comprehensive regulating pool is: CODcr=3500mg / l, BOD 5 =1000mg / l, NH 3-N=400m / l, TN=500mg / l, TP=10mg / l, SS=1200mg / l, pH=4~6 (dimensionless).

[0016] The discharge standards are the water collection standards of local municipal sewage treatment plants as follows: CODcr=400mg / l, BOD 5 =150mg / l, NH 3 -N=30m / l, TN=45mg / l, TP=6mg / l, SS=150mg / l, pH=6.5~9.5 (dimensionless).

[0017] Using the municipal sludge wastewater deep treatment system of the present invention, the process route of the project is designed as "grid → comprehensive regulation → high-precision self-cleaning filtration → pH adjustment → coagulation sedimentation → hydrolysis acidification → two-stage AO biochemical → tubular ultrafiltration membrane → clear water tank → standard discharge, which specifically includes the following steps: S1, send the sewage sludge wastewater into the screen well 1 through the pipeline, separate the large suspended matter, floating matter, fiber matter and solid particulate matter in the wastewater, and the separated wastewater enters the comprehensive regulating tank 2; S2, the wastewater is comprehensively regulated in the comprehensive regulating tank 2, and dilute sulfuric acid or sodium hydroxide is added to roughly adjust the pH value of the wastewater to 6-9, and the hydraulic retention is 12-24 hours, and then the regulated wastewater is pumped into the high-precision self-cleaning filter 3; S3, the wastewater is filtered in a high-precision self-cleaning filter 3, which uses a 10-300 mesh screen to physically intercept particulate matter in the wastewater. The filter has an automatic cleaning function and is automatically cleaned by a pressure difference sensor. The equipment is automatically program controlled and does not require manual cleaning. The filtered wastewater enters a pH adjustment reaction tank 4; S4, the wastewater is conditioned in the pH regulating reaction tank 4 for 5 minutes, the speed of the speed reducer in the pH regulating reaction tank 4 is 50 r / min, acid / base is added to the pH regulating reaction tank 4 to adjust the pH value of the wastewater to 7-8.5, and the wastewater after pH adjustment enters the coagulation reaction tank 5; S5, PAC (polyaluminium chloride) is added into the coagulation reaction tank 5, the dosage is 30mg / l, the wastewater reacts in the coagulation reaction tank 5 for 5min, the speed of the reduction mixer in the coagulation reaction tank 5 is 50r / min, the wastewater after the reaction enters the flocculation reaction tank 6, PAM (polyacrylamide) is added into the flocculation reaction tank 6, the dosage is 3mg / l, the wastewater reacts in the flocculation reaction tank 6 for 10min, the speed of the reduction mixer in the flocculation reaction tank 6 is 20r / min, after sufficient reaction, the wastewater enters the sedimentation tank 7 for mud-water separation, and the supernatant of the sedimentation tank 7 flows into the intermediate water tank 10 by gravity; S6. The wastewater is hydraulically retained in the intermediate water tank 10 for 0.5-2 hours, and then pumped to the pulse water distributor 11 by the lifting pump. The pulse water distributor 11 evenly distributes the water to the bottom activated sludge bed of the hydrolysis acidification tank 12, and hydraulically retains for 8-12 hours. Under anaerobic conditions, high-efficiency anaerobic bacteria hydrolyze and acidify the difficult-to-degrade substances in the wastewater. The biodegradability (B / C) of the acidified wastewater is improved, and the B / C reaches above 0.3. After high-precision self-cleaning filtration, pH adjustment, coagulation sedimentation, and hydrolysis acidification units, the effluent quality of the hydrolysis acidification tank is: CODcr=2500mg / l, BOD 5 =800mg / l, NH 3 -N=400m / l, TN=500mg / l, TP=3mg / l, SS=200mg / l, pH=7~8 (dimensionless), CODcr removal rate is 28.5%, BOD 5 The removal rate is 20%, the TP removal rate is 70%, the SS removal rate is 83.3%, B / C=0.32, and the biodegradability is significantly improved. The wastewater treated in the hydrolysis acidification tank (12) enters the two-stage AO tank; S6, the two-stage AO pool includes a first anoxic pool 13, a first aerobic pool 14, a second anoxic pool 131 and a second aerobic pool 141 which are sequentially connected by pipelines. The wastewater is biologically denitrified by nitrification / denitrification of nitrifying bacteria and denitrifying bacteria in the two-stage AO pool. The two-stage AO pool is equipped with a variety of instruments for real-time monitoring. Sodium acetate is added to the first anoxic pool 13 and the second anoxic pool 131, and sodium hydroxide is added to the first aerobic pool 14 and the second aerobic pool 141. The wastewater is reacted in the first anoxic pool 13 and the second aerobic pool 141 in sequence. 0~30h, the first aerobic pool 14 reacts for 60~90h, the second anoxic pool 131 reacts for 10~20h, and the second aerobic pool 141 reacts for 20~40h, so that the online pH value is controlled at 7~8, the reaction temperature is controlled at 20~35℃, the oxidation-reduction potential (ORP) instrument value is controlled between +50~-50mV, and the dissolved oxygen of the wastewater in the second aerobic pool 141 is controlled at 2~4mg / l through a DO (dissolved oxygen) analyzer, and the treated wastewater enters the tubular ultrafiltration membrane 15; S7. Wastewater is separated into mud and water in the tubular ultrafiltration membrane 15. The tubular ultrafiltration membrane 15 adopts an external tubular ultrafiltration membrane, which has a larger flux than the traditional MBR, adapts to a wider range of sludge concentrations, is easy to repair, easy to maintain on a daily basis, and has a higher degree of automation. The principle is to use the microporous filtration effect of the membrane to intercept the activated sludge and increase the concentration of the activated sludge, thereby increasing the removal efficiency of the pollution factors (CODcr, BOD, etc.) and maximizing the biochemical treatment efficiency. In addition, since the water is filtered out through the membrane, the secondary sedimentation tank and subsequent filtration facilities are omitted, the floor space of the sewage treatment facility is reduced, and the treatment process is shortened.

[0018] The project is designed with an external tubular ultrafiltration membrane flux of 55L / (㎡.h) and a sludge concentration of 25g / l. The ultrafiltration is fully automated and program-controlled, without manual intervention. The ultrafiltration inlet pump flow is 83m³ / h, the head is 20m, the ultrafiltration circulation pump flow is 264m³ / h, the head is 50m, the water production flow is 8.5m³ / h, the membrane group system operating pressure is 5~6bar, the ultrafiltration membrane group is one standby and one in use, and a set of chemical cleaning system is provided.

[0019] After two-stage AO and ultrafiltration membrane separation units, the final effluent quality is: CODcr=250mg / l, BOD 5 =30mg / l, NH 3 -N=15m / l, TN=36mg / l, TP=1.3mg / l, SS=0.5mg / l, pH=7~8 (dimensionless), CODcr removal rate is 90%, BOD 5 The removal rate was 96.3%, NH 3 -N removal rate is 96.3%, TN removal rate is 92.8%, TP removal rate is 50%, SS removal rate is 99.7%, the effluent water quality meets the municipal sewage treatment plant management standards, and can be stably discharged in compliance with the standards. The filtered wastewater enters the clear water tank 16 and meets the discharge standards; S8, the backwash water of the high-precision self-cleaning filter 3, the sludge in the sedimentation tank 7 and a part of the sludge from the tubular ultrafiltration membrane 15 enter the sludge concentration tank 8 for concentration, and PAM is added into the sludge concentration tank 8 in an amount of 50-150 mg / l. A 12 million cationic polyacrylamide with a molecular weight is used as a conditioning agent. After adjustment, it is pumped into the screw stack dewatering machine 9 for dehydration treatment. After dehydration by the screw stack, the moisture content of the sludge is about 80-85%. The dehydrated sludge is pumped to the municipal sludge deep treatment workshop for deep treatment, and the filtrate is refluxed to the grid well 1 for circulation treatment.

[0020] It can be seen from the above that the method of the present invention is scientific and reasonable, and has the following advantages compared with the prior art: 1. To solve the problem of high suspended solids in wastewater, the present invention adopts a high-precision self-cleaning filter to intercept solid particles, intercepts solid particles in the filter through a high-precision 10-300 mesh screen, and then adopts a coagulation method to perform high molecular polymer flocculation precipitation to solve the problem of high suspended solids in wastewater; the backwashing procedure is automatically started by the pressure difference change, which greatly saves labor costs; 2. For the difficult-to-degrade substances in wastewater, the present invention adopts an improved biochemical method for biochemical treatment, and performs biochemical degradation by taming microorganisms to minimize the operating cost. The two-stage AO biochemical treatment process monitors the biochemical reaction state in real time through high-precision analytical instruments (pH, ORP, DO, temperature), making the biochemical treatment visual and controllable, and providing an operating basis for the biochemical treatment through the changes in instrument parameters; 3. At the end of the treatment, an external tubular ultrafiltration membrane is used for mud and water separation, which maximizes the biochemical treatment efficiency while increasing the sludge concentration in the biochemical pool. The most important thing is that it saves the traditional secondary sedimentation tank and subsequent filtration facilities, reduces the floor space of sewage treatment facilities, shortens the treatment process, and uses full automated control operations, saving labor costs, achieving good treatment effects, high efficiency, and good social and economic benefits.

[0021] It should be noted that the above components are all prior art and commercially available products. The contribution of the present invention is to scientifically design and layout these known components, effectively solve the defects of the prior art, and meet production needs. It should be pointed out that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any technician familiar with the profession can make changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention, and all of them fall within the protection scope of the present invention.

Claims

1. A method for deep treatment of municipal sludge wastewater, characterized in that: The following steps are involved: S1, sending the municipal sludge wastewater into the screen well (1) through the pipeline, separating the large suspended matter, floating matter, fiber matter and solid particulate matter in the wastewater, and the separated wastewater enters the comprehensive regulating tank (2); S2. The wastewater is comprehensively regulated in the comprehensive regulating tank (2), and acid and alkali reagents are added to roughly adjust the pH value of the wastewater to 6-9. The wastewater is hydraulically retained for 12-24 hours, and then the regulated wastewater is pumped into the high-precision self-cleaning filter (3); S3, the wastewater is filtered in a high-precision self-cleaning filter (3), the high-precision self-cleaning filter (3) uses a 10-300 mesh screen to physically intercept particulate matter in the wastewater, and the filtered wastewater enters a pH adjustment reaction tank (4); S4, the wastewater is subjected to pH adjustment in the pH adjustment reaction tank (4), the reaction time is 5 to 10 minutes, the speed of the reduction mixer in the pH adjustment reaction tank (4) is 30 to 50 r / min, acid / base is added to the pH adjustment reaction tank (4), the pH value of the wastewater is adjusted to 7 to 8.5, and the wastewater after pH adjustment enters the coagulation reaction tank (5); S5, PAC is added to the coagulation reaction tank (5) at a dosage of 10-50 mg / l, the wastewater reacts in the coagulation reaction tank (5) for 5-15 min, the speed of the reduction mixer in the coagulation reaction tank (5) is 30-50 r / min, the wastewater after the reaction enters the flocculation reaction tank (6), PAM is added to the flocculation reaction tank (6) at a dosage of 2-5 mg / l, the wastewater reacts in the flocculation reaction tank (6) for 5-12 min, the speed of the reduction mixer in the flocculation reaction tank (6) is 10-25 r / min, after sufficient reaction, the wastewater enters the sedimentation tank (7) for mud and water separation, and the supernatant of the sedimentation tank (7) flows by gravity into the intermediate water tank (10); S6, the wastewater is hydraulically retained in the intermediate water tank (10) for 0.5 to 2 hours, and then the wastewater is pumped to the pulse water distributor (11) by the lifting pump, and the pulse water distributor (11) evenly distributes the water to the bottom activated sludge bed of the hydrolysis acidification tank (12). The wastewater is hydraulically retained for 8 to 12 hours. Under anaerobic conditions, high-efficiency anaerobic bacteria hydrolyze and acidify the difficult-to-degrade substances in the wastewater. The B / C ratio of the acidified wastewater reaches above 0.

3. The wastewater treated in the hydrolysis acidification tank (12) enters the two-stage AO tank; S7, the two-stage AO pool includes a first anoxic pool (13), a first aerobic pool (14), a second anoxic pool (131) and a second aerobic pool (141) which are connected in sequence via pipelines. The wastewater is biologically denitrified in the two-stage AO pool by nitrification / denitrification of nitrifying bacteria and denitrifying bacteria. A carbon source is added to the first anoxic pool (13) and the second anoxic pool (131), and an alkali solution is added to the first aerobic pool (14) and the second aerobic pool (141). The wastewater is sequentially added to the first anoxic pool (13), the second aerobic pool (141) and the second aerobic pool (141). 13) react for 20-30 hours, the first aerobic tank (14) reacts for 60-90 hours, the second anoxic tank (131) reacts for 10-20 hours, and the second aerobic tank (141) reacts for 20-40 hours, so that the pH value of the wastewater is 7-8, the reaction temperature is controlled at 20-35°C, the redox potential value is controlled at +50-50mV, the dissolved oxygen of the wastewater in the second aerobic tank (141) is controlled at 2-4mg / l, and the treated wastewater enters the tubular ultrafiltration membrane (15); S8. The wastewater is separated into mud and water in a tubular ultrafiltration membrane (15). The ultrafiltration membrane flux is 50~120L / (㎡.h), and the applicable sludge concentration is 10~50g / l. The filtered wastewater enters a clear water tank (16) and meets the discharge standards; S9, the backwash water of the high-precision self-cleaning filter (3), the sludge in the sedimentation tank (7) and a part of the sludge from the tubular ultrafiltration membrane (15) enter the sludge concentration tank (8) for concentration, and PAM is added to the sludge concentration tank 8 in an amount of 50-150 mg / l with a molecular weight greater than 12 million. After adjustment, it is pumped into the screw press dewatering machine (9) for dehydration treatment. The dehydrated sludge is pumped to the municipal sludge deep treatment workshop for deep treatment, and the filtrate is refluxed to the screen well (1) for circulation treatment.

2. The method for deep treatment of municipal sludge wastewater according to claim 1, characterized in that: The comprehensive regulating tank (2), pH regulating reaction tank (4), first aerobic tank (14) and second aerobic tank (141) are all equipped with online pH meters, the high-precision self-cleaning filter (3) is equipped with a differential pressure sensor, the first anoxic tank (13) and second anoxic tank (131) are both equipped with an ORP analyzer and a temperature controller, the first aerobic tank (14) and second aerobic tank (141) are both equipped with a DO analyzer, and a pressure gauge is installed on the tubular ultrafiltration membrane (15).

3. The method for deep treatment of municipal sludge wastewater according to claim 1, characterized in that: The screw stacking and dehydrating machine (9) is a 301 type screw stacking and dehydrating machine.

4. The method for deep treatment of municipal sludge wastewater according to claim 1, characterized in that: In step S2, the acid and alkali reagents are dilute sulfuric acid and sodium hydroxide, and in step S7, the carbon source is sodium acetate and the alkali solution is sodium hydroxide.

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