Study On The Treatment Of The Micro-polluted Water Of Dongjiang By GAC-Sand Filters

Dongjiang raw water is the major source of drinking water in Dongguan,Guangdong Province. However, with emissions of pollutants increasing in the upperreaches, some factors like drainage of canal lead to the situation that Dongjiang rawwater has a higher probability of suffer from sudden pollution in rainy season. In thatsituation, the traditional water treatment technique cannot guarantee that water plantshave the qualified outlet water. GAC-sand filter, which is an important method toimprove the water qualify, can cope with the seasonal and sudden pollution ofDongjiang water to some extent. In this paper, the author takes use of the Dongjianglocal water and simulative seasonal polluted water and employs GAC-sand filter as thecore technique, research the effect of micro-polluted water of the Dongjiang byenhanced coagulation, Potassium permanganate pre-oxidation, powdered activatedcarbon adsorption and activated carbon sludge return with the combined process ofGAC-sand filter respectively, and provide technical support for the future practicalapplication of various treatment processes by examining the removal rate on turbidity,COD_Mn, UV₂₅₄, ammonia and other indicators.The results show that GAC-sand filter substitutes Sand filter can enhance the waterquality effectively, and have a better removal especially for small organic molecules.Enhanced coagulation can enhance the removal of turbidity and organic matter.However, to a certain extent, increase the coagulant dosage, water turbidity willincreased and organic removal rate will not rise again. According to the actual waterquality, coagulant dosage can be controlled between10and20mg/L.Organic matter can be removed by Potassium permanganate oxidation, the newmanganese dioxide can play the role of adsorbing organic matter and promoting thecoagulation. Potassium permanganate pre-oxidation has the advantages of simplyoperated and small cost, and can be popularized for a wide range.PAC adsorbed can enhance the removal of organic matter and removes turbiditywell. With the long-term operation of the process, there will be a layer of biofilm on thesurface of the GAC-sand filter, Ammonia in the water can be effectively removed by theAerobic bacteria from the biofilm.Powdered Activated Carbon sludge return can improve the residence time in thesystem of the PAC, organic matter in the water will be removed by PAC. At the same time, Powdered Activated Carbon sludge can reduce the dosage of the coagulant.Nitrifying bacteria in the sludge can remove the ammonia and nitrite significantly.