The Experimental Study On High Turbidity Water By Two-stage Coagulation- Sedimentation Process

With the rapid urban construction development in China and the growing urban population, urban residents water consumption also has increased. In the current situation of the growing river basin soil erosion and increasing water pollution case, the high turbidity of surface water resources has become an important source of urban water component.Meanwhile, with the economic development and social progress, and the improvement of people's consumption level, the requirements on water quality are increasingly stringent. Because of high turbidity, sediment deposition, and difficulties which are not easy to deal with of high turbidity water , and so on, high turbidity water use has been restricted in some areas, even some time water plants in order to exert compliance in the high turbidity water period, not does not reduce the water load, thus producing less water.Aiming at the features of turbidity high, and complex terrain of the Upper Yangtze River raw water, regarding the existing two-stage coagulation- sedimentation process treating high turbidity water as the research object, research treatment effect on the Jialing River source of water in its different operational conditions, seeking for operating characteristics and flocculants to adapt the Jialing River raw water quality parameters, to provide technical guidance and design for the same type water treatment plant's design and optimization operation, has important practical significance.In this paper, in view of different turbidity conditions of the Jialing River, take two-stage coagulation-sedimentation in the high turbidity levels time, when a low turbidity time one-stage natural sedimentation + two-stage coagulation-sedimentation methods to test, study the two-stage different hydraulic retention time ratio, different flocculent dosing types and the effluent effect with the different dosage at the different coagulation and sedimentation mode, investigate the impact on process running effect about the water temperature, pH value, waters change. At the same time investigation the impact on turbidity, UV₂₅₄, COD_Mn, NH₄⁺-N removal efficiency in different flocculation and the impact on UV₂₅₄, COD_Mn, NH₄⁺-N removal effect to turbidity removal were discussed.The results showed that:â‘ On high turbidity time, adopt the two-stage coagulation-sedimentation, and add polymer flocculent PAM in the first stage; on low turbidity time, adopt one-stage natural sedimentation and two-stage coagulation-sedimentation process. Effluent quality can reach less than 10NTU water turbidity requirements before the filter.â‘¡According to treatment effect under different HRT ratio, combined with the existing water treatment plant with two-stage coagulation-sedimentation process operation, propose that the two-stage coagulation-sedimentation hydraulic retention time ratio is 1:2.â‘¢Under the condition of one-stage and two-stage hydraulic retention time ratio 1:2, when the high turbidity one-stage PAM dosage of 1.5 mg/L, two-stage PAC dosage of 20 mg/L, when the low turbidity two-stage PAC dosage of 25 mg/L would be more appropriate.â‘£Under the same condition of flocculation and sedimentation way, inlet quality and meeting the outlet quality indicators, PAC dosage is smaller than FeCl3 dosage.⑤During the trial, water temperature change is little, so water temperature was the main factor affected outlet effect in this experiment. With the source water pH increase, turbidity is on the increase, while the UV₂₅₄, COD_Mn, NH₄⁺-N removal rate has not changed.â‘¥On the water impact load, two-stage coagulation-sedimentation effluent turbidity values did not exceed 10NTU.⑦Turbidity removal has a positive significance on the UV₂₅₄, COD_Mn, NH₄⁺-N removal.