The Experimental Study On The Treatment Of Reservoir Water Derived From Yellow River By Flotation-Sedimentation Process

The phenomenon of high amounts of algae in summer and low temperature and turbidity in winter is prevalent in reservoir water derived from Yellow River. With the aggravator of water pollution, it becomes more and more difficult to meet the new drinking water standards by the conventional treatment process. Therefore, it is necessary to improve and optimize the existing treatment process. Pilot test device of flotation-sedimentation basin was designed for reservoir water derived from Yellow River, fully combined flotation and sedimentation technique to exert their functions and thus had a greater adaptation for the changing raw water. The relative in-depth study of flotation-sedimentation treatment process for reservoir water derived from Yellow River was carried on in this paper.This paper includes three aspects:(1) the optimum operating parameters study of flotation-sedimentation process in different water quality; (2) the experimental study on flotation-sedimentation and active-filter combined process on treatment for reservoir water derived from Yellow River; (3) preliminary discussion on the flotation model.In the optimum study of operating conditions in the period of high amounts of algae on the flotation-sedimentation technology, it is recommended the optimal dosage of PFAC as a coagulant was 5mg A13+/L. On this basis, the location of coagulant dosing was determined. In the optimum study of function conditions in flotation unit, by examining the removal effect of pollutants in different reflux ratio and the sampling points of flotation, the best proposed reflux ratio was 14%, and the sampling points of this device is determined too.During the period in winter when the water was of low temperature and low turbidity, in order to find out the optimal operating parameters of flotation-sedimentation process, it was advised that the best dosage of PFAC as coagulant was 2mg A13+/L through the experiment. In the optimum study of hydraulic loading in flotation unit, the influencing factor of primary and secondary order conditions were ascertained by orthogonal test, and the optimal level for the reflux ratio was 14%, the flux 5m3/h, mixing speed 130r/min and flocculation speed 60r/min. On the basis of orthogonal test to investigate the reflux ratio affecting the operating results, it was recommended that the reflux ratio of 12% was adopted. According to the changes of water turbidity in slag-off cycle, it was determined that the cycle was within the 2～3h.Through the experimental study on flotation-sedimentation and active-filter combined process on treatment for reservoir water derived from Yellow River, it was found that the combined process had good removal of turbidity, CODMn and UV254. Through the duration of test, the effluent turbidity after the combined process could be basically lower than 0.5NTU, less than the current drinking water standards. The removal of CODMn was slighter better than UV254 by flotation. The average removal of CODMn was 18.9% and UV254 was 17.1% after the flotation-sedimentation process. After active-filter the average removal of CODMn rose to 34.6% and UV254 were 42.1%. It showed that the removal of UV254 was better than CODMn by active-filter. It was also found that the removal of precursor of DBPs by flotation-sedimentation was limited, but the removal could be achieved more than 13% after active-filter.Finally, the kinetic model in the contact zone of flotation was briefly introduced, and the flotation efficiency model was preliminary discussed with reference to bubble-particle collision model.