1, wastewater quality

This project has a set of treatment device with a treatment capacity of 200m3/d, which needs to be modified. In addition, the second phase of the project, which is in urgent need of production, will be added, and a new set of wastewater treatment device will be built, with the wastewater treatment capacity of 200m3/d and the total amount of wastewater of 400m3/d. ..

Table-1 coking wastewater quality (unit: mg/l)

2. Water quality discharge requirements

According to the secondary standard of Shanghai Comprehensive Wastewater Discharge Standard, the discharge standard to be reached after wastewater treatment is shown in Table -2:

Table -2 Discharge Standard for Wastewater Treatment (except temperature and pH, the rest units are mg/L)

(II) Wastewater treatment process

1, process

This reconstruction and expansion project includes two parts: original system reconstruction and new construction. According to the sewage treatment achievements of Shanghai Coking Co., Ltd., combined with the original sewage treatment process, the new expansion project adopts A 1-A2-O biofilm process.

Try not to change the function and structure of the existing sewage treatment facilities, make full use of the treatment capacity of the existing sewage treatment structures, transform the old system, and add an anaerobic acidification tank on the basis of the original A/O system, that is, change it into A 1-A2-O biochemical system. A new biochemical system A 1-A2-O will be built, and each system will bear half of the treated water.

Process flow chart of the whole sewage treatment reconstruction and expansion project (omitted)

2. Description of process flow

(1) The production wastewater and domestic wastewater from each workshop enter the regulating tank in a unified way. The main function of regulating tank is to balance the quality and quantity of wastewater and ensure the stability of subsequent biochemical treatment facilities. Because the phosphorus content in wastewater is very small, phosphorus nutrients are added to the regulating tank to provide nutrients needed by microorganisms.

(2) The wastewater from the regulating tank is respectively lifted to the new and old biochemical system A 1-A2-O by two pumps. In the biochemical treatment system, the degradation process of wastewater is as follows:

A. Coking wastewater first enters the anaerobic acidification section. In this section, heterocyclic compounds such as phenol, xylenol, quinoline, isoquinoline, indole and pyridine in wastewater have been greatly transformed or removed, and the setting of anaerobic acidification section is very beneficial to the transformation and removal of complex organic compounds. Therefore, the water quality of wastewater after anaerobic acidification has been improved, and the biodegradability of wastewater has been improved compared with that of raw water, which provides a more effective carbon source for the subsequent denitrification stage.

B. Denitrification reaction is mainly carried out in the anoxic section, the wastewater from the acidification section enters the anoxic section, and at the same time, the treated effluent from the aerobic section partially flows back to the anoxic section to provide nitrate nitrogen for the anoxic section. In addition, due to the lack of denitrification carbon source in coking wastewater, methanol should be added to the anoxic tank as a supplementary carbon source.

After anoxic treatment, nitrate nitrogen is transformed into nitrogen to achieve the purpose of nitrogen removal. At the same time, most of the organic matter in the wastewater is removed, which makes the wastewater enter the aerobic section, and the COD is low, which is very beneficial to the nitrification reaction in the aerobic section.

C, the wastewater enters the aerobic section after being treated in the anoxic section. In aerobic stage, wastewater contains higher ammonia nitrogen and lower COD. Therefore, the nitrification reaction is mainly carried out here, and soda solution needs to be added to the aerobic section to provide the alkalinity required for the nitrification reaction. After the wastewater is treated in aerobic stage, ammonia nitrogen can be basically transformed into nitrate nitrogen (nitrate nitrogen can be effectively denitrified after returning to anoxic stage, and finally transformed into nitrogen in anoxic stage), and at the same time, the organic matter is further degraded, so that the final effluent COD reaches the standard.

(3) After the wastewater is treated by biochemical system, it is separated from sludge by coagulation sedimentation tank, and polyiron is added to the coagulation part to improve the sedimentation performance of the precipitated sludge and further reduce the COD of the effluent.

The effluent of the secondary sedimentation tank is connected to the "Northern Drainage" pipe network.

(4) The surplus sludge discharged from the secondary sedimentation tank is regularly discharged into the sludge concentration tank for concentration and stabilization, the supernatant of the concentration tank is refluxed to the regulating tank for further treatment, the sludge in the concentration tank is discharged into the sludge storage tank, and the sludge is periodically dewatered by a sludge dewatering machine. PAM should be added to react with sludge for flocculation before dewatering to improve sludge dewatering efficiency.

Sludge is dehydrated and then transported for treatment.

4. Process conditions

(1) Control the quality and quantity of influent water.

According to the original statistical data of the quality and quantity of coking wastewater and the provisions of the design scheme, the quality and quantity of wastewater entering the sewage treatment system must meet the design requirements.

(2) Pretreatment of wastewater

In order to reduce the load of subsequent biochemical treatment, reduce the impact load of toxic substances, stabilize the effect of subsequent biochemical treatment, and facilitate operation management, wastewater needs to be pretreated before entering the system.

A. control the COD content of influent.

Excessive fluctuation of influent COD will greatly affect the system operation. Therefore, according to the design requirements, the influent COD should be strictly controlled within the design requirements.

B. Control the inlet water temperature

The final cooling wastewater, ammonia evaporation wastewater and ammonia evaporation wastewater from 5 # and 6 # coke ovens in the old factory area need to be cooled to below 38℃ by plate condenser and atomizing cooler and then discharged into the regulating tank due to the high water temperature.

C. control the oil content of feed water.

Gas condensate wastewater and turbid water from different streams are treated by gravity oil separation and air flotation (the oil content is lower than 30mg/L), so that the oil content is lower than the concentration that affects the normal growth of microorganisms, and then discharged into the regulating tank.

D. reducing ammonia nitrogen

Part of the ammonia distilled wastewater first passes through the fixed ammonia decomposition device of Coking Co., Ltd., and its ammonia nitrogen concentration is reduced from 800 mg/L to 250 mg/L, and then discharged into the regulating tank.

E. reduce ash content

Because of the high ash content, the wastewater from "triple supply" needs to be precipitated and cleaned before it can be discharged into the regulating tank.

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