Research On Semicentralized Wastewater And Solid Waste Integrated Treatment System

With the course of rapid urbanization in our country, economy of city and town has got prompt development, which has brought about enormous pressure to ecological environment at the same time. Under this background the concept of "semicentralized wastewater and solid waste integrated treatment system" was proposed, which could promote reduce, reuse, and recycle in the city as a new philosophy of environmental protection. As an important component of domestic sewage, greywater has characteristics of low-pollution and large volume, and its reuse could save water and reduce discharge in the city, which has great social, environmental and economic effectiveness. So far, the research of greywater reuse in our country is still in its beginning stages, so research and development of greywater treatment technology is great important to resolve the problem of water shortage and promote the level of wastewater recycling technology.This subject tends to research the feasibility and prospect of Biological Aerated Filter and Coagulation process to treat greywater. The main content includes:(1) Research of Biological Aerated Filter for greywater treatmentFrom the aspects of startup of BAF, removal of main pollutants and pressure loss, Clay ceramsite agitator and new type sphere ceramics filter material were individually studied in BAF, to research the most suited characteristics of filters media to greywater treatment.(2) Research of Coagulation process for greywater treatmentOrthogonal experiment is carried out to research the Coagulation effect of bathing wastewater in two water qualities, and find out better range of reaction conditions and finally determine the best coagulation condition for greywater.The results show that:(1)Research of Biological Aerated Filter for greywater treatmenta. Clay ceramsite has characteristics of high porosity, high roughness and big specific surface, which is good to microbes' growth. So the ability of biochemical degraded and shock load of BAF is high. In steady-going stage, removal rate of COD, NH₃-N, LAS, SS, turbidity was individually 85%, 80%, 90%, 80%, 95%, and effluent concentration was individually bellow 50mg/l, 5mg/l, 1.0 mg/1, 10 mg/1, 5mg/l, which could satisfied the reuse criteria for urban non-potable household. But the mechanical strength and filter bed expansibility when backwashing of this filter media is not good, so the filter bed was blocked easily which load to more frequently backwashing and high energy consumption.b. New type sphere ceramics filter material has characteristics of high mechanical strength and low specific gravity, which is good to backwash of BAF and prevent blockage. In steady-going stage, removal rate of COD, NH₃-N, LAS, SS, turbidity was individually 75%, 50%, 90%, 70%, 95%, and effluent concentration was individually bellow 50mg/l, 10mg/l, 1.0mg/l, 20mg/l, 5mg/l. But characteristics of lower porosity, lower roughness and smaller specific surface lead to unstable growth of biomass, which weaken the ability of BAF treatment, for example the unstable treatment effect and higher SS.(2) Research of Coagulation process for greywater treatmentOrthogonal experiments were carried out to research the Coagulation effect of Bathing wastewater in two water quality (one was bathing wastewater; the other was bathing wastewater after storied ), and find out better range of reaction conditions and finally determine the best coagulation condition for greywater.a. Through orthogonal experiment, the better range of coagulation reaction conditions for bathing wastewater was got: pH≈7, middle mixing speed, PAC or PAFC, dosing amount of coagulant is 150mg/l for "I water quality" and 100mg/l for "II water quality".b. In this experiment, adding coagulant aid could promote the settling ability, but the effect of pollutant removal didn't increase.c. The best coagulation reaction conditions for bathing wastewater was got by single factor experiment: I water quality: dosing amount of coagulant was 50～100mg/l, mixing speed was 50～100 r/min. II water quality: dosing amount of coagulant was 50⁷5mg/l, mixing speed was 30～80 r/min.As a whole, through the research of Biological Aerated Filter and Coagulation process for greywater treatment we got results as follow:(1) The most suited characteristics of filters media for greywater treatment were got by research of comparison of Clay ceramsite agitator and new type sphere ceramics filter material in BAF, which would supply important reference to choose and optimize filter media. (2) BAF demands higher influent quality, even greywater which is low polluted also need pretreatment. Coagulation process could be chosen for greywater pretreatment to remove most SS and LAS, providing better biochemical degraded condition for subsequent treatment system.