| Drinking water is linked to our living level and our health closely, and biological stability is one of the most important aspects for drinking water safety. The presence of organic matters in treated water would promote bacterial regrowth, and in turn would lead to corrosion of pipe materials and deterioration of water quality in distribution systems. The bacteria growth and biological stability problems in drinking water caused by biodegradable dissolved organic carbon has become a recent focus in the field of water treatment.The study was from "National water pollution and management major projects"-the research and comprehensive demonstration of drinking water safety in the Yellow River downstream. According to the water instability caused by seasonal changes and secondary pollution in distribution pipe network, the relationship between water treatment processes and the stability of water in pipe network was analyzed in this study; the monitoring and assessment techniques about the stability of pipe network water was researched; the feasibility of a method to improve the stability of network water by strengthening water treatment process was explored; the operating parameters of conventional water treatment process were optimizated; a technical program to control the pipe network secondary pollution and improve water quality stability by transfonnating water process was proposed in order to promote the drinking water safety security work in the Yellow River downstream. In this paper, the water supply system in Jinan was investigated. The water stability in waterworks, the influence of treated water for the stability of network water and the simulation experiment were researched. At last, the effluent water after upgrading water plant was analyzed. Main research contents and results of this paper were summarized as follows:(1) Combined with the raw water data of Quehua plant in Jinan, the water quality belonged to Ⅲ～Ⅳ slightly polluted water according to 《The Surface Water Environment Quality Standards》(GB3838-2002).(2) Combined with the literature on water biological stability, AOC and BDOC had good correlation with heterotrophic bacteria. So the subject selected BDOC as the evaluation of the biological stability of drinking water.(3) The Quehua plant raw water’BDOC concentration was between0.144～0.294mg/L, and most values was less than the suggested value of0.2mg/L. The raw water was stable basically.(4) Water quality stability of pipe network depended on the treated water. Monitoring different positions of the pipe network water quality of Quehua plant showed that BDOC concentration was0.142mg/L～0.217mg/L, some value exceeded occasionally, but most value were less than the suggested value of0.2mg/L. So the pipe water was stable.(5) Conventional water treatment process had high removal to turbidity. It had partial removal of organic pollutants, and mainly in the filter units. This may be because filter material surface would generate certain biological membrane after filter’ s long term operation, which would improve the removal efficiency of organic pollutants such as TOC. The treated water belongs to a biological stability water, and its BDOC value was between0.125-0.2mg/L. BDOC and TOC had a good relationship, assuming that BDOC was y, TOC was x, the relationship was:y=9.291x3-65.38x2+153x-118.8, R=0.997. Therefore reduce the organic matter in water could improve the water’s biological stability effectively.(6) By using a transformation process of biological activated carbon, TOC and BDOC removal rate were13.87%and25.22%separately, increased by6.71%and12.49%compared to conventional treatment process. The reason was the transformation process strengthened the biodegradation. By using biological activated carbon process can improve the water stability effectively.(7) By O3-BAC-membrane treatment process, TOC removal rate was up to92.75%, BDOC removal rate was81.12%. By biodegradation and membrane-bound could greatly improve the removal of organic matter. Through the deep processing technology could enhance the water quality and water stability, and this could provide technical support and learn for other water plant’s transformation process and the protection of pipe network terminal water quality. |
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