Experimental Study On Treatment Of Low Turbidity And Micropolluted Water By Combined Application Of High-density Sedimentation Tank And Powder Active Carbon

Our drinking water sources have been widely polluted and the traditional water purification technique can not function effectively in the removal of organic substance in raw water. The treatment of micro-polluted raw water has always been an urgent technical problem waiting to be solved. However, the enhanced coagulation process developed in recent years has made great progress in this field. And the high-density sedimentation tank is the most important technique in the process.In this research, high-density sedimentation tank is adoped to treat micro-polluted raw water. Activated carbon powder and potassium permanganate are added to form a combined process together with the high-density sedimentation tank and the activated carbon powder is made to return with the sludge into the raw water in the treatment system, so as to fully develop the absorption potential of the activated carbon and the functions of potassium permanganate and manganese dioxide as coagulation aid and oxidant to enhance the removal of organic substance.The result of the pilot test, which adopts the combined process of the pre-oxidated potassium permanganate, activated carbon powder and high-density sedimentation tank, indicates that the fittest sludge reflux ratio can get the best result of the effluent turbidity and the removal of organic substance. When the ratio is 60%, the turbidity of filtrated and settled water and the removal of UV254 and CODMn achieve the perfect effect. Adding potassium permanganate can get the same result for its function as coagulation aid. When they are combined together, the sludge return can furtherly improve the removal efficiency of the potassium permanganate, while the potassium permanganate can enhance the removal ability of the sludge return.The result of the pilot experiment that adopts the combination of activated carbon powder and high-density sedimentation tank shows that the flocculating effect can be improved by increasing the sludge return ratio within a certain limit under the optimum dosage of polyacrylamide. When the sludge return ratio exceeds this limit, the removal effect of the turbidity and organic substance will not be improved distinctively. This research finds that the optimum dosage of polyacrylamide is 1.0mg/L and the optimum sludge return ratio is 5%. The combined process of activated carbon powder and high-density sedimentation tank can make the effluent water quality meet the standard of"Standards for Drinking Water Quality"(GB5749-2006). The research result shows that the combined process of activated carbon powder and high-density sedimentation tank is a quite effective technique for the treatment of micro-polluted raw water.