2023-03-18518
The biological treatment method utilizes the metabolism of microorganisms to convert toxic and harmful organic substances into less toxic substances, with a reasonable cost. The process of purifying sewage by sewage treatment equipment to meet the water quality requirements for discharge into a certain water body or reuse. Sewage treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering, and more, and is increasingly entering the daily lives of ordinary people. However, paint wastewater has a high concentration and contains a large amount of toxic organic substances, which is difficult to be directly biodegradable; Therefore, at present, both domestic and foreign countries mostly adopt the technique of combining physical and chemical methods with biological methods, that is, using physical and chemical methods to fully homogenize water quality and quantity, in order to reduce the impact load on subsequent biological treatment.
1.1 Activated sludge method
Ford is the largest automotive manufacturer in the world, and the wastewater generated during its production process includes deionized water, paint wastewater, and domestic sewage. During the treatment process, the coating wastewater is first combined with deionized water for chemical flocculation and deposition, and then settled in an upflow contact sedimentation tank before entering the aeration tank. The original high concentration coating wastewater lacks the nitrogen and phosphorus necessary for microbial growth, which is confused with domestic sewage. The required nutrients are supplied by domestic sewage, while a certain amount of special nutrients are added according to actual needs for deployment, which helps stimulate the growth of degrading bacteria, improve the operating performance of the activated sludge treatment system, and improve its biodegradation efficiency. The mixed sewage is treated in an activated sludge tank and finally accumulated in a secondary sedimentation tank. In order to achieve the consequences of tertiary filtration, the wastewater from the secondary sedimentation tank is filtered again, and the most outdated water quality analysis is carried out. After 4 months of experimental treatment, the BOD of the original coating wastewater decreased from 15000 mg/L to 21 mg/L, with a total removal rate of 99.3%.
The company uses oil separation - air flotation - cyclic activated sludge process - filtration process to treat coating wastewater, and the various indicators of the effluent basically meet the design requirements, with a total COD removal rate of about 98.1%. Due to the difficulty in physicochemical separation of water-soluble solvents in paint wastewater, it is possible to choose coagulation filtration as a pretreatment process, and then flow into a membrane bioreactor with good treatment results and high level of activeness. After activated sludge aeration and biochemical treatment, both COD and SS in the effluent have good removal results.
1.2 Biofilm method
The biofilm method is to make the microbial community adhere to other objects in a nominally membranous form and become contaminated through contact with wastewater. The process of purifying sewage by sewage treatment equipment to meet the water quality requirements for discharge into a certain water body or reuse. Sewage treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering, and more, and is increasingly entering the daily lives of ordinary people. Currently, there are many important processes for treating coating wastewater using biofilm:
Biological turntable
The harmful waste water produced by the United States Navy for paint removal each year exceeds 1.1 billion liters, including important dichloromethane and phenol; In addition, there are alkanes, cellulose derivatives, petroleum sulfonates, and naphthalene. The wastewater was mixed with domestic sewage at a ratio of 1 to 1, and a comparative experiment was conducted using the activated sludge method and the biological rotary disk method to distinguish it. The results showed that this type of mixed wastewater can be effectively treated regardless of whether the bacterial population is in suspension growth or adsorption growth. In addition, improving the nutrient environment by using activated sludge can significantly improve the number of bacteria in the treatment system, which is two orders of magnitude higher than when using only a single carbon source. In a biological turntable system, the number of bacteria in continuous influent water is significantly higher than that in intermittent influent water, which may be due to two reasons: first, during intermittent influent water, the concentration of toxic wastewater in the reaction system is higher than that during continuous influent water; Second, continuous water inflow is more conducive to bacterial adsorption. In addition, after a comprehensive analysis of the number, variety, and ability of bacteria to degrade toxic compounds, it is believed that Pseudomonas and rod-shaped bacteria are the dominant bacteria for degrading such wastewater.
Biological contact oxidation method
When Chongqing Three Gorges Paint Co., Ltd. is treating wastewater from the comprehensive coating industry, it uses a biological contact oxidation treatment process after primary treatment, resulting in short incubation time, high activity, and fast degradation rate of organic substances in the wastewater. Hunan Xiangjiang Paint Group adopts a process of uniform oil separation, coagulation, air floatation, biological contact oxidation to treat comprehensive paint wastewater, and the effluent meets the national first-class discharge standard. Studies by Zuo Hongying and others have shown that after pre-treatment using flocculation and sedimentation and air flotation, followed by secondary biological contact, the treated water is treated by activated carbon and industrial recycling cooling water processors, ultimately meeting the design standard requirements for industrial recycling cooling water.
Biological fluidized bed
The biological fluidized bed uses particle data with a particle diameter of less than about 1 mm as a carrier and fills the aeration container. The wastewater fluidizes the carrier from bottom to top, and the carrier is nominally covered with a biofilm. The process of purifying sewage by sewage treatment equipment to meet the water quality requirements for discharge into a certain water body or reuse. Sewage treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering, and more, and is increasingly entering the daily lives of ordinary people. Wuhan Shuanghu Paint Co., Ltd. pretreated the paint production wastewater by primary air flotation and then treated by a pure oxygen biological fluidized bed device, which has high efficiency and can meet the discharge standards.
At present, the author is studying the combination of a moving bed biofilm process and an aerated biofilter process. MBBR has a strong ability to resist shock loads, and BAF has the characteristics of integrating biological oxidation with the interception of suspended solids. The two are combined to form a composite biofilm process for the treatment of coating wastewater. After a period of operation, the inventive system has good treatment results and operates firmly. When the hydraulic retention time of the single stage reactor is 5 hours and the COD concentration of the uniform inflow is 800 mg/L, the ultimate COD removal rate of the effluent reaches 93.05%.
The organic content of paint wastewater is individually high, and it is not suitable to directly adopt aerobic method for treatment. First, anaerobic biological treatment can be adopted. Chen Bei added biochemical treatment in front of the original air flotation tank, and the first stage was set as aerobic biochemical treatment. Under the action of aerobic bacteria, the macromolecular organic matter was degraded into small molecular organic matter, which lowered the CODCr value of the wastewater, while improving the BOD5/CODCr value of the wastewater, thereby facilitating the next aerobic biochemical treatment.
Oxidation ponds are natural or artificially constructed ponds in which wastewater stays for a long time and organic contaminants are degraded and contaminated through the metabolic activity of microorganisms in the water.
Using aquatic animals as the main source of ecological pond engineering contaminated paint wastewater is also an efficient biological treatment technique. Huang Yunzhu and others cultivate water hyacinth in the paint wastewater after physical and chemical pretreatment, and the wastewater supplies water and nutrients required for the growth and development of water hyacinth. Experiments have shown that water hyacinth has strong vitality, excellent pollution resistance and reception, and is an excellent anti pollution animal. Its ecosystem uses metabolism to comprehensively treat contaminated wastewater, achieving illusory results. Moreover, the process flow for contaminating paint wastewater in the ecological pond project is relatively simple, and it can contaminate industrial wastewater mainly composed of acids, alcohols, and benzenes, with the best consequences for phenol containing wastewater. However, because the treatment results of oxidation ponds are greatly affected by light and temperature, the treatment results in individual summers are better than those in winter.