At present, the best coking wastewater treatment process is A1-A2-O biofilm process.
The specific process flow is as follows:
(1) The production wastewater and domestic sewage from each workshop enter the regulating tank uniformly, and the main function of the regulating tank is to balance the quality and quantity of wastewater and ensure the stability of the subsequent biochemical treatment facilities. Because the phosphorus content of wastewater is very small, phosphorus nutrient salt is added to the regulating tank to provide nutrients needed by microorganisms.
(2) The wastewater from the regulating tank is respectively upgraded from two pumps to the new and old A1-A2-O biochemical systems. 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, phenol, xylenol, quinoline, isoquinoline, indole, pyridine and other heterocyclic compounds 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 the anoxic treatment, nitrate nitrogen is converted into nitrogen, thus achieving 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 with low COD, 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 the aerobic stage, the wastewater contains higher ammonia nitrogen and lower COD. Therefore, the nitrification reaction is mainly carried out here, and soda solution needs to be added in the aerobic section to provide the alkalinity required for the nitrification reaction. After the wastewater is treated in the aerobic section, ammonia nitrogen can be basically converted into nitrate nitrogen (nitrate nitrogen can be effectively denitrified after returning to the anoxic section, and finally converted into nitrogen in the anoxic section), 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 the sludge by coagulation sedimentation tank, and polyiron is added to the coagulation part, so as 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 to the sludge concentration tank for concentration and stabilization treatment, and the supernatant of the concentration tank is refluxed to the regulating tank for further treatment, and the sludge from the concentration tank is discharged to the sludge storage tank, which is periodically dewatered by the sludge dewatering machine. PAM should be added to react with sludge for flocculation before dewatering to improve sludge dewatering efficiency. Sludge is dewatered and then transported for disposal.