Study On Enhanced Coagulation Of Adsorbent In The Raw Water Of South To North Water Diversion Project In South Hebei Province

In the operation of a waterworks in the south of Hebei Province,there are many problems such as low turbidity and difficulty in coagulation,algae blocking the filter,significantly increasing the coagulant dosage,etc,it is necessary to adjust the waterworks process.Enhanced coagulation with adsorbent can improve the removal efficiency of algae and various organic matters,has the advantages of simple process and no need to change treatment facilities.This study aims to investigate the treatment effect of adsorbent enhanced coagulation in the raw water of the South-to-North Water Transfer Project in Southern Hebei Province.Firstly,a small test was carried out to compare and select the adsorbents,to study the removal effect of adsorbent enhanced coagulantion on pollutants,and to further study the influencing factors.Then the dynamic test is carried out to optimize the dosage of adsorbent enhanced coagulation.On this basis,the continuous dynamic test of the adsorbent enhanced coagulation to treat the raw water of the south-to-north water transfer was investigated in the actual operation,and the comparison between the adsorbent enhanced coagulation and the traditional coagulation technology was analyzed.The results showed that in the small-scale test,when PAC and 5 adsorbents were used to enhanced coagulation,the removal effect of chlorophyll a was better when powdered activated carbon or diatomite was added,but the removal effect of turbidity was worse when powdered activated carbon was added.The optimal dosage of diatomite for enhanced coagulation was 15mg/L PAC and 20mg/L diatomite,and the removal rate of chlorophyll a,COD_Mnn and UV₂₅₄54 were 93%,93.2%,41.4%and 38%,respectively,and the minimum residual aluminum was 0.179 mg/L.The study on the influencing factors of diatomite enhanced coagulation showed that the pH value has a great influence on the residual aluminum.Controlling the pH value in the range of 6.5-7.5 can made the residual aluminum in the effluent of the two kinds of pH adjustment modes lower than 0.2mg/L.The removal effect of pollutants was the best when PAC was added first for 10mins,then diatomite was added for coagulation.When the residual aluminum and turbidity were the lowest,the dosage of PAC was different,and when the residual aluminum reached the lowest,the dosage of PAC is lower.So the residual turbidity and aluminum content should be controlled reasonably.The dynamic test was used to treat the high temperature and high algae water from the south to north water of Hebei Province,it is determined that the treatment capacity of subsequent test run is 48L/h.Based on the removal effect,cost and residual aluminum content of PAC and adsorbent at different dosages,it is optimized to add5mg/L diatomite in the range of 10-15mg/L PAC to enhanced coagulation treatment the raw water of South-to-North Water Transfer Project;or add 5mg/L powdered activated carbon in the range of 10-15mg/L PAC to enhanced coagulation treatment the raw water of South-to-North Water Transfer,the chlorophyll a of the precipitated effluent was all below 1ug/L,which reduces the adverse effect of algae on the filter.Adsorbent enhanced coagulation continuous dynamic test results showed that When adding 10mg/L PAC+5mg/L diatomite for enhanced coagulation or adding10mg/L PAC+5mg/L powdered activated carbon for enhanced coagulation,the main indexes of filtered water were far lower than the hygienic standard of drinking water,which solved the problem of water plant operation.Compared with PAC coagulation alone,the sludge yield of enhanced coagulation by adding adsorbent was larger,but the treatment effect and stability of pollutants were better.Adding a small amount of adsorbent would not significantly increase the running cost.