Selection and Optimization of Control Technics in CODCr and Colority of the Refined Cotton Wastewater Treatment Process in a Refined Cotton Enterprise in Rudong, Jiangsu Province
|School||Nanjing Agricultural College|
|Keywords||refined cotton wastewater treatment process optimize CODCr Colority|
Refined cotton is one kind of high-purity cellulose product, obtained by the refining treatment of Cotton linter, i.e. alkali cooking and bleaching. Refined cotton is mainly used in the manufacture of cellulose esters, ethers and other cellulose derivatives. The alkaline black liquor produced during the production process contains a large number of impurities, such as cotton linter, which belongs to lignin-type substance. It has complex component and poor biodegradability, which brings about great difficulties in the progress of the refined cotton wastewater treatment.According to statistics, at present domestic production of refined cotton is about 100,000 tons/year. The existing four refined cotton producers have a total production capacity of 10,000 tons/year, and produce more than 200 million tons/year wastewater in Rudong County, Jiangsu Province. Four producers comply with the requirements of environmental protection enterprises, supporting the construction of chemical and biological or biochemical wastewater treatment facilities. But in the production process, the deficiencies in treatment project cause high cost and the wastewater is not constant according to the wastewater discharge standards. Therefore, in order to establish a set of economic, rational and practical process of the refined cotton wastewater treatment, a Refined Cotton Enterprise in Rudong was selected for optimizing the original progress design and improving the refined cotton wastewater treatment, so that it could be used by the similar enterprise’s wastewater disposal for reference.For a Refined Cotton Enterprise in Rudong, CODcr and Colority of the refined cotton wastewater are very high.In this study, the author improved the original physical chemical processes and biochemical methods, and optimized their combination. The main conclusions drawn from the investigation are as follows:(1) Flocculate reagent (A)、flocculation reagent (B)、centrifuge (SS450) and centrifuge (LWL-450) are chosen in the test. There are four combinations, including flocculate reagent (A)-LWL450、flocculation reagent (A)-SS450、flocculate reagent (B)-LWL450 and flocculation reagent (B)-SS450. According the test, comparing treatment effects, the result is that the combination of flocculate reagent (A)-LWL450 has the best effect, the mean removal rate of CODCr is 48%, the mean removal rate of chroma is 37%. So during the first period of alteration, flocculate reagent (A)-LWL450 is chosen for physical chemistry section increased.(2) During the second period, the way of actived sludge method in aerobic pool is changed into biological contact oxidation. After alteration, sewage of the final limber hole is let up to par. Biological contact oxidation has upper removal rate of contamination, the mean removal rate of CODCr and chroma are 78.3% and 73.5%, respectively. While the mean removal rate of CODCr and chroma by the old way of actived sludge method are only 34.4% and 40.6% respectively.(3) After two alterations, waste water is let up to par. Treated with the optimized process, CODCr of the inlet greater than or equal to 4000mg/L and Colority of the inlet greater than or equal to 1000 times can reach CODCr of the outlet less than or equal to 100mg/L and colority of the outlet less than or equal to 50 times, respectively, which achieve the primary standard of《Wastewater Integrated Discharge Standard》(GB 8978-1996).Compared to the original process, optimized combination of process not only overcomes the deficiencies of the physical chemical processes and the biochemical methods, but also has many advantages such as good effect, low running costs. At the same time, it reduces the accumulation of harmful substances, and enhances the recycle ratio of the water. According the analysis of running cost, we find that among fixed investment, the cost of centrifuge and filling have big percentage. However, with development of mechanical manufacture technology and filling, the part of cost will get lower. Running cost is not very high, after budget, it is 7.24yuan per cubic meter. During running stage, the cost of source power is the main factor for high running cost. The combined process is easy, not cost too much, it is considered a good process for wastewater meeting the discharge limits steadily and reuse.