Study On The Pretreatment Process For Source Water Of Dongjiang River

In the paper, aiming at solving the problem of the manganese overrunning the national stndard in the Dongjiang River - the source water of Dongguan City, the dynamic process of potassium permanganate preoxidation for removing the manganese in the Fourth Water Plant in Dongguan City has been studied on the basis of earlier jar testing. In the dynamic process, the effectiveness of the removal of manganese in the process of potassium permanganate preoxidation and influence on the removal of the organic pollutant in the conventional treatment process have been studied, at the same time, the effectiveness of adsorption on the organic pollutant in the source water and the function of aid coagulation of the freshly formed hydrous manganese dioxide formed in the preoxidation process also have been analyzed. The effectiveness of the removal of the organic pollutant in the water by the adsorption of powder actived carbon has been studied in the jar testing and the optimal kind of powder actived carbon suitable to treat with the source water in Dongguan city has been conformed. In addition, the characteristic of potassium permanganate oxiding the humic acid has been further discussed in order to perfect the principle of potassium permanganate oxiding the organic pollutant.The research results indicate as follows:① The process of preoxidation of potassium permanganate has a good effect on the removal of the manganese,and the process is suitable to treat with the source water in Dongguan City. In the process, the average removal of manganese is up to 98.3% at the average potassium permanganate dose of 0.22mg/L,and the average content of manganese in the finished water is 0.002mg/L absolutely to meet the desired purpose.② The formed manganese dioxide in the preoxiding process has been mostly sedimentated in the terminal of the sedimentation tank, so the burden of the filter tank has not been increased.③ The preoxidation process redounds to the effectiveness of coagulation and reduces the dose of the coagulant. The average turbidity in the source water in the Fouth Water Plant is 30.4NTU in July in 2004,and the average dose of PAC is 16.3mg/L;while the average turbidity in the source water is 36.8NTU in the preoxidation process in October in 2004,but the average dose of PAC is only 15.7mg/L.Analysis has been implied that the freshly formed hydrous manganese dioxide formed in the preoxidation process has the function of aid coagulation. ④ The preoxidation process has been of great benefit to developing the removal of the organic pollutant. According to the analysis results from the dynamic experiment, the average removals of UV254, CODMn and TOC have respectively increased 6%, 6.5% and 16% in contrast with the conventional treatment process.⑤ In the preoxidation process the potassium permanganate has been used instead of chlorine in the process of pretreatment, which then distinctly control the formation of DBPs such as choroform and carbon tetrafluoride which can result in cancer.⑥ In order to solve the urgent pollution of source water in Dongjiang River caused by overflow, powder actived carbon has been performed subsequently to enhance the finished water quality at the optimal dose of 10~20mg/L.