Printing and dyeing wastewater is one of the main sources of water pollution, which is characterized by large amounts of sewage and difficult treatment. It is estimated that the average water consumption for producing 100 meters of standard cloth is about 2.5 tons, and the wastewater has complex composition and high color. At the same time, wastewater contains a large amount of organic matter, which makes its CODcr value high, highly alkaline, and difficult to treat.
At present, the main treatment methods are divided into physical methods, chemical methods, physical chemical methods and biochemical methods. In recent years, research on the use of photocatalysis and electrochemistry to treat printing and dyeing wastewater has attracted people’s attention. However, physical and chemical treatment methods are usually more expensive, produce waste that is difficult to process, are not efficient, and have limited applications. The biological treatment method has the advantages of simple operation, low operating cost, no secondary pollution, and environmental friendliness, and has attracted more and more attention in the treatment of printing and dyeing wastewater.
At present, aerobic biological methods, anaerobic methods and combined treatment technologies are mainly used in China. Aerobic treatment of printing and dyeing wastewater is divided into activated sludge method and biofilm method. The anaerobic method can degrade dyes containing azo groups, anthraquinone groups and triphenylmethane groups through anaerobic degradation of dyes. However, the degradation products of these dyes are aromatic amine compounds, which are carcinogens and cannot continue to be degraded under anaerobic conditions, that is, they cannot be completely degraded to achieve inorganicization of the dyes. Therefore, it is rare to use anaerobic reactors to directly treat printing and dyeing wastewater. Report. However, the efficiency of the new high-efficiency anaerobic treatment device has been greatly improved, and the requirements for the COD concentration of the incoming water have been greatly reduced. Wastewater with a COD value of 2000mg/l can also reach the standard through primary biological treatment through anaerobic digestion. Joint treatment technology is a combination of anaerobic and aerobic processes, that is, anaerobic and aerobic processes are connected in series to collaboratively treat printing and dyeing wastewater. Among them, anaerobic treatment mainly hydrolyzes and acidifies some polymer substances with poor biodegradability in printing and dyeing wastewater and turns them into smaller molecules, or changes the molecular structure of refractory organic matter, thereby improving the biodegradability of wastewater. Create conditions for aerobic treatment. At the same time, all the remaining sludge produced in the aerobic stage can also be returned to the anaerobic tank. Since the anaerobic stage has a long enough solid residence time, the sludge can be thoroughly anaerobically digested, so that there is basically no remaining sludge in the entire system. Mud discharge.
At present, the main development direction of printing and dyeing wastewater treatment is the combination of microorganisms and treatment technology. Many environmental engineers are committed to screening efficient degrading bacteria and constructing genetically engineered bacteria to utilize the vast resources of nature to serve mankind. However, newly developed high-efficiency bacteria used in wastewater treatment may not necessarily achieve the expected strengthening effect. Whether the bacterial species can occupy a dominant position in the treatment system, whether the complex components in the wastewater will inhibit its growth… many factors will affect the treatment effect. Therefore, the application of biotechnology must undergo strict environmental safety testing and evaluation. At the same time, the degradation mechanism of dyes and the metabolic mechanism of microorganisms need to be further studied and clarified.
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