Study On The Distribution Of Pollutants In Domestic Wastewater And Their Treatbility Evaluation

The discharge of domestic wastewater is the main reason of water pollution. It is very important to select a technically reliable and economically feasible process for wastewater treatment. This paper systematically studied the characteristics of pollutants and their distribution in domestic wastewater, and investigated the effects of wastewater treatment units on pollutant removal. The objective of study is to provide theoretical basis for a rational selection of several typical for wastewater treatment.A membrane filter with 0.45um pore size was used to separate the pollutions in the wastewater into soluble matter and suspended matter. The method of fuzzy analysis was applied to e valuate t he weight of the main pollutants in t he d omestic wastewater. water quality matrix and water quality conversion matrix was introduced into the analysis regarding 4 kinds of wastewater treatment process such as sedimentation, coagulation-sedimentation, secondary treatment by oxygen ditch and a hybrid MBR for pollutant characterization and treatbility evaluation.The main conclusions can be draw as following :(l)In the domestic wastewater about 70%of the organic matter is suspended,80%of nitrogen is soluble, about 90% of inorganic nitrogen is soluble ,60% of organic nitrogen is soluble and 50%of the phosphorous compound is soluble;(2)the weight factors of SS, COD, BOD, TN, TP are 0.2621,0.1094,0.1724,0.0519, 0.4042, so the contaminants which threaten the environment are phosphorous compound, suspended solid organic matter and nitrogen in a sequence according to their degree of significance. Among them, TP, SS and organic pollutant, exist mostly as suspended matter, and therefore become the important part of the pollutants in the domestic wastewater ;(3) Sedimentation can remove50% of the SS, 70% of the CODcr and suspended BOD5. The soluble organic matter, ammonia nitrogen only can be removedby bio-treatment ;(4)The coagulation-sedimentation shows a high efficiency of treatment of suspended matter in domestic wastewater. The efficiency of TP removing can be as high as 95%. All these show the advantages of the enhanced primary treatment, although it can not achieve a high level of soluble pollutants as the level of biological treatment. The water quality index of SS, CODcr, BOD5 and TP can reach the general standard of wastewater discharge.The methods adopted in this paper are applicable in the filed of wastewater treatment. The result of the study can provide theoretical basis for the selection of wastewater treatment method. In the area, where secondary wastewater treatment is difficult to implement, especially in the underdeveloped regions of the west china, enhanced primary treatment is recommendable because it can remove most suspended pollutants and get good treatment results.