Take you all-round understanding of the source and treatment process of coking wastewater
Release time：
2020-07-16
Coking wastewater is a typical toxic and refractory organic wastewater. Coking wastewater mainly comes from the production water and steam condensate wastewater in the initial cooling of coke oven gas and coking production process.
Coking wastewater is a typical toxic and refractory organic wastewater.
Coking wastewater mainly comes from the production water and steam condensate wastewater in the initial cooling of coke oven gas and coking production process.
Characteristics: the high concentration of pollutants in coking wastewater is difficult to degrade. Due to the presence of nitrogen in coking wastewater, the nitrogen source required for biological purification is excessive, which brings great difficulties to treatment compliance;
The amount of wastewater discharged is large, and the water consumption per ton of coke is more than 2.5t;
Wastewater is harmful. Polycyclic aromatic hydrocarbons in coking wastewater are not only difficult to degrade, but are also usually strong carcinogens, which cause serious pollution to the environment and directly threaten human health.
Wastewater source:
Coking Plant mainly produces chemical products such as coke, commercial gas, ammonium sulfate and light benzene. The plant's tar recovery system adopts the ammonium sulfate process, the tar processing adopts two-tower continuous distillation in a tubular furnace, and the industrial naphthalene production process is continuous distillation, washing, and refining with two furnaces and two towers. In the process of coke oven gas cooling, washing, crude benzene processing and tar processing, industrial wastewater containing phenol, cyanide, oil, ammonia and a large amount of organic matter is produced.
Environmental protection
Treatment process:
Process flow
The expansion project includes two parts: the original system transformation and the new construction. According to the results of coking wastewater treatment, combined with the original wastewater treatment process, the new expansion project adopts the A1-A2-O biofilm process.
Try not to change the function and structure of existing wastewater treatment facilities, make full use of the treatment capacity of existing wastewater 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 to A1 －A2－O Biochemical System. Build a new set of A1-A2-O biochemical system, and the two systems will each bear half of the treated water.
Flow Description
(1) The production wastewater and domestic sewage from each workshop enter the regulating tank uniformly. The main function of the regulating tank is to balance the water quality and volume of the wastewater and ensure the stability of the subsequent biochemical treatment facilities. Since the wastewater contains very little phosphorus, phosphorus nutrients are added to the conditioning tank to provide nutrients needed by microorganisms.
(2) The wastewater from the regulating tank is lifted by two pumps to the old and new 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 the wastewater have been transformed or removed. The setting of the anaerobic acidification section is for the conversion and removal of complex organic matter. It is very advantageous. Therefore, after the wastewater passes through the anaerobic acidification section, the water quality is improved, and the biodegradability of the wastewater is improved compared with the original water, which provides a more effective carbon source for the subsequent denitrification section.
B. The denitrification reaction is mainly carried out in the anoxic section. The wastewater from the acidification section enters the anoxic section. At the same time, the effluent after the aerobic section is partially returned to the anoxic section to provide nitrate nitrogen for the anoxic section. In addition, because the denitrification carbon source contained in the coking wastewater is insufficient, it is necessary to add methanol as a supplementary carbon source in the anoxic tank. After the treatment in the anoxic section, nitrate nitrogen is converted into nitrogen to achieve the purpose of nitrogen removal. At the same time, most of the organic matter in the wastewater is removed, so that the wastewater enters the aerobic section with a lower COD, which is very beneficial for the nitrification reaction in the aerobic section.
C. Wastewater enters the aerobic section after being treated in the anoxic section. In the aerobic section, the COD is low due to the high ammonia nitrogen contained in the wastewater. Therefore, what is going on here is mainly the nitration reaction. Soda ash solution needs to be added in the aerobic section to provide the alkalinity required for the nitration reaction. After the wastewater is treated in the aerobic section, the ammonia nitrogen can basically be converted into nitrate nitrogen (nitrate nitrogen is returned to the anoxic section, and is finally converted to nitrogen in the anoxic section to obtain effective denitrification). At the same time, the organic matter is further Degrade, make the effluent COD reach the standard.
(3) After the wastewater is treated by the biochemical system, it is separated from the sludge and water through the coagulation sedimentation tank, and polyiron is added to the coagulation part to increase the sedimentation performance of the sedimented sludge and further reduce the COD of the effluent.
(4) The remaining sludge discharged from the secondary settling tank is regularly discharged to the sludge thickening tank for thickening and stabilization treatment, the supernatant of the thickening tank is returned to the regulating tank for further treatment, and the thickening tank sludge is discharged into the sludge storage tank at regular intervals. The sludge dehydrator performs dehydration treatment. Before dewatering, PAM needs to be added to flocculate the sludge to improve the efficiency of sludge dewatering.
Environmental protection
Process conditions
(1) Control the quality and quantity of influent water
According to the original statistical data of the water quality and quantity of the main sources of coking wastewater, as well as the design plan, the quality and quantity of wastewater entering the sewage treatment system must meet the design requirements
(2) Wastewater pretreatment
In order to reduce the subsequent biochemical treatment load and reduce the impact load of toxic substances, at the same time, to stabilize the subsequent biochemical treatment effect and facilitate operation management, the wastewater needs to be pretreated before entering the system.
A. Control the COD content of influent water If the fluctuation of COD in influent water is too large, it will have a great impact on the operation of the system. 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 evaporating wastewater and 5#, 6# coke oven ammonia evaporating wastewater from the old factory area need to be cooled to below 38℃ by a plate condenser and atomized cooler and then discharged into the regulating tank due to the high water temperature.
C. Control oil content in influent water
gas condensate waste water and the turbid water from various places are separated by gravity and deoiled by air flotation (oil content is less than 30mg/L), and the oil content is lower than the concentration that affects the normal growth of microorganisms before being discharged into the regulating tank.
C. Reduce ammonia nitrogen
part of the distilled ammonia wastewater first passes through the fixed ammonia decomposition device, reduces its ammonia nitrogen concentration from 800 mg/L to 250 mg/L, and discharges it into the regulating tank.
D. Reduce ash content
follow the principle
1. The technology is mature and reliable, and it has a good pertinence to the inflow of the wastewater treatment plant, the treatment effect is stable, and the long-term continuous operation is guaranteed, and the effluent quality is stable and up to standard.
2. Reasonable infrastructure investment, low operating cost, flexible operation mode, and obtain the largest possible benefits with the smallest possible investment.
3. Convenient operation and management, and can adjust the operation mode and parameters according to the fluctuation of the influent water quality, so as to maximize the processing capacity of the treatment structure.
4. It is convenient to realize the automatic control of the process, improve the management level, and reduce labor intensity and labor costs.
5. The selected equipment is advanced, reliable, highly localized, and good in complete sets.
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