Study On Treatment Of Low Temperature And Low Turbidity Water By Enhanced Coagulation

In Jnne of 2001, Ministry of Sanitation ordinates the criterion for daily drinking water quality, which increased the water quality, indexes to 96 items and the turbidity value was claimed to 1NTU. But the water quality is even worse. By now,the tradiontial process of water treatment is not suitable. According the operation data of a north water treatment plant, optimization of coagulant for low temperature and low turbidity water is aneconomy method among all kinds of water purification technologies under the conditions of reducing the production costs.Laboratory and full scale experiments were analyzed by coagulation mechanism regards on the raw water characteristics. The paper studied the effects of some common inorganic and polymeric coagulants; analyzed the influencing factors on coagulation for a low temperature and low turbidity water. A polymeric coagulants, Polymeric Ferric Silicate Sulfate (PFSS), was prepared and compared with PAC on the effects of the treatment of a low temperature and low turbidity water. Meantime, the controlling conditions were determined in the processes. It was obtained to increase the coagulating agents dosage to enhance the coagulation and improve the effluent based on the probability analysis of experimental results.The test showed that the coagulant dosage increased as the row water turbidity increased in order to achieve the same sediment effects under virus turbidity. Both common row water and a low temperature and low turbidity one can reach a precipitation extreme. No matter how many agents were increased, the settling efficiency would not increase when a precipitation extreme was appeared.The figure of coagulating agents dosage and ratio was obtained based on the probability analysis of the enhancement and the dosage was determined by the effluent turbidity aim. The coagulation was better when the ratio was 15~25 than it was 5~15 for such a low temperature and low turbidity raw water.The full-scale experimental results showed the turbidity of the effluent after filtering can be as low as 0.4 NTU by flocculants dosage increasing under such a low temperature, low turbidity, CODMn<5mg/L. Meantime, the removal efficiencies of UV254, TOC and DOC were greatly increased and some other common ones were improved too. It shows that such a coagulating agents dosage increasing method can be used to revise the former water treatment process and improve the effluent to meet the standards.