Experimental Research On Treatment Process Conditions Of Micro-polluted Source Water

In recent years,lakes and reservoirs in China are confronted with more and more serious water pollution,even if the water which was used as urban sourse water. Domestic and overseas research on the treatment of micro-polluted source water (MPSW) is available,but special experimental research is necessary for specific case because of the different conditions in different water bodies.This paper selected Tangyu Reservoir as its research object,which is located in Lantian City,Shaanxi Province,China.Based on monitoring water quality during one year,we analyzed the change trend and reasons of pollutants measures,and Kmeans Clustering Analysis model was employed to divide research duration into different phases according to the different water quality.In order to find out the optimal dosage and types of chemicals,we adopted jar test to treat the source water in different phases by "Enhanced Coagulation" and "Chemical pre-oxidation + Enhanced Coagulation" processes respectively in different conditions.Through the above experimental research, we analyzed the effect of purifing water in different treatment process conditions and enhanced coagulation factors.The monitoring results indicated:pH of source is approximately 8.Turbidity and the concentrations of TN and Mn exceed the allowed standard.Color and the concentration of TP may occasionally exceed the allowed standard and the concentrations of NH₄⁺-N and Fe are low continuously.Alga amount which is positively correlated to water temperature and the concentration of TP is relatively high from May to September.And the concentration of organism is caused to be high as a result of massive reproductions,metabolism and death of algae.The concentration of Chla, which is positively correlated to water temperature and alga amount,presents the obvious seasonal variation.According to Kmeans Clustering Analysis,the source water quality was divided into three phases:high-temperature and high-alga water quality phase(May～Mid-October);normal water quality phase(Mid-October Mid-November and March～April);low-temperature and low-turbidity water quality phase(Mid-November～February).In high-temperature and high-alga water quality phase,the best option is PAC dosage of 25mg/L if only sole coagulant was used to enhanced coagulation,while the best option is PAC dosage of 20mg/L and PAM dosage of 0.4mg/L if the coagulant-aid was added.In low-temperature and low-turbidity water quality phase,the best option is PAC dosage of 25mg/L and PAM dosage of 0.4mg/L whose molecular weight is 5 millions.In the condition that the coagulant dosage is determined,the removal rate of turbidity,Mn and organism gradually decreases along with the decreasing of temperature and turbidity and the best pH value scope for turbidity and Mn removal is 7.83～8.05 and approximately 7.83 for organism removal.Not only the pollutants concentration after treatments but also the pollutants removal rate,the process of enhanced coagulation with pre-oxidation can get better effect than other ones,such as sole coagulant process and coagulant-aid added process. The optimal chemical for pre-oxidation is ClO₂ and the optimal dosage is 2.0mg/L.