Tianjin Water Quality Of Chemical Pre-oxidation Pilot Study

In Chinese north cities, more than 70% of drinking water resource is surface water which has been seriously polluted by organic matters and algae. As a result, the conventional treatment processes can't guarantee the safety of drinking water, which makes advanced and efficient treatment techniques necessary. The quality of Tianjin resource water varies greatly with seasons and often worsens abruptly. The characteristic of Tianjin resource water is typical in north China. In this study, preoxidation applied on Tianjin resource water during different water quality periods was conducted to intensify the conventional treatment processes, enhance removal efficacy of organic matters and improve the quality of drinking water.The preoxidation by four chemicals, such as potassium permanganate, chorine ozone and ozone/hydrogen peroxide, and its influence on the subsequent processes were analyzed. The results showed that preoxidation could improve the quality of the water after following treatment processes.As to water in Summer with high amounts of algae, although only few organic matters were removed after preoxidation by potassium permanganate, water quality after sand-filtration was improved obviously; and prechlorination could efficiently remove algae, but its effect was directly related to the quantity of algae and was more obvious in the period of algae bloom; algae also could removed efficiently with preozonation, and the turbidity and UV254 after air-flotation and sand-filtration were highly reduced, accordingly THMFPs and HAAFPs were decreased. Ozone/hydrogen peroxide had the equal ability with preozonation in the aspect such as the coagulation-aid, organic matters removal. However, it possessed of the best ability to reduce the THMFP and HAAFP among the preoxidation.With regard to Yellow River water in winter with low temperature and low turbidity, it was showed that propriety potassium permanganate would reduced the turbidity after the subsequent processes, but little removal of organic matters; It was further revealed that the effect of preozonation as the coagulation-aid decreased, but preozonation enhanced the efficiency of removal of organic matters.As to the water in ordinary period, the turbidity after sedimentation increased by potassium permanganate, however, water quality after filtration was improved. But water quality after sedimentation and filtration increased remarkably with preozonation, which reduced the dosage of coagulant and increased the velocity of the filtration.The effects of all three preoxidants in three typical water quality periods were compared in the end and the results showed that it was the ozone that is the best preoxidant during summer water period with high amounts of alga, and the appropriate dosage is 1.0-1.2mg/L; and during the period with lowtemperature and low turbidity, the best preoxidant is potassium permanganate with the dosage of 0.8mg/L; during the ordinary period, the best is ozone with the dosage of 1.0mg/L...