The Research On The Treatment Of The Waste Water From Garment Washing And Dyeing

Clothing washing and dyeing industries have prospered in recent years, which were scattered in the cities with small scale and great numbers. The Wastewater from these factories has seriously polluted the water enviorment. Because it is difficult to treat this Wastewater with centralized process, it is urgent to develop the suitable treatment technology with little investment.Based on the characteristics of the washing and dyeing Wastewater, a physical-chemistry treatment technology was studied. Under certain pH value, Coagulants and flocculants were added into the Wastewater, after settling, the supernate was discharged or recycled after further treatment. The wasterwater samples were taken from Zhuzhou washing and dying factories. The characteristics of the original Wastewater are: pH, 2～6; COD_Cr; 250～4000 mg/L; colourity (chroma), 250～1000 with the color of blue and black; turbidity, 320～1200 degree. The effects of different factors such as pH, coagulant and flocculatant dosage, stirring duration and settling-aids were investigated. The optimal reaction conditions are: pH, about 9.5; inorganic coagulantflocculate dasage, 0.4 kg/m³; polyacrylamide dasage, 3 g/m³; activated flyash dasage, 3 kg/m³, and stirring duration, 5 min. After settling, the COD_Cr removal efficiency is 80%, decolor efficiency is 98% and turbidity removal efficiency is 96%. The water quality can meet the second national effluent standard. At the same time, function mechanisms of coagulation, flocculation and settling were discussed.Because of the slow sedimentation velocity and large sludge volume in the physical-chemistry treatment, the coagulation-electrical floatation was studied. The results show that the removal efficiency of suspended substance reaches 96% after 4 min flotation with graphite as electrode, the pressure of 8 ～11V and energy consumption of 0.08 degree/m³. When Fe was used as the anode material, the Wastewater purification was enhanced and COD_Cr removal efficiency reaches 86%. The mechanisms of elctronical floatation process ware initially discussed.The full-scale tests were carried out with two different processes: coagulation-flocculation-settling process and coagulation-flocculation-settling and...