Study On The Key Technologies For Water Treatment Of Yellow River With Low Temperature And Low Turbidity

In December 2006, Ministry of Sanitation and the National Standardization Management Committee jointly revised and issued a new “drinking water health standards”(GB5749-2006), from July 2007 to implement. In the standards, the water quality indexes increased from 35 in GB5749-85 to 106, revised 8 items. The turbidity was claimed from 3NTU to 1NTU. Revision of this standard protects the interests of people’s health and Water companies were put forward higher requirements. According the operation data of Yinchuan Helanshan water plant, optimization of coagulant for low temperature and low turdibity water is an economical and effective method among all kinds of water purification technologies under the conditions of reducing the production costs and meeting the water quality standard.The coagulation beaker test were analyzed by coagulation mechanism regards on the low temperature and low turdibity water characterisistics, the thesis studied the effects of some commom coagulants; analyzed the influencing factors on coagulation for the low temperature and low turdibity water; researched the relationship of water turbidity and coagulant dosage; the coagulating agents influence on the low temperature and low turbidity water in the purification process; and the optimum pH range, flocculation time and other factors influence on the low temperature and low turbidity water.The coagulation beaker test shows that the coagulant dosage increased as the water after precipitation turbidity increased in order to achieve the same sediment effects under virus turbidity. But the low temperature and low turbidity water can reach a precipitation extreme, No matter how many coagulants were increased, the settling efficiency would not increase when a precipitation extreme was appeared. The test shows that PAC optimal dosage was 6mg / L, the coagulating agents optimal dosage was 0.7 mg/L, and in the start of flocculation after 3 ~ 6 min,dosing the coagulating agents can get a optimal effect. The optimum pH range in the treatment of low temperature and low turbidity water is 7~8.According to the production experiment research results, PAC best dosage is 6 mg/L. Mixing the row water and the filter backwash water, the coagulating characteristics has no significant difference, just need a fine tune of the coagulant dosage in the mixed water. Also according to the analysis of the variable cost equation, the infections of the water coagulation, sedimentation, filtration, backwashing in the water treatment process was reflected by the settled water turbidity, and the settled water turbidity determines the operation status of the water treatment system, so, the operation cost of Helanshan water plant, was reduced greatly.