| The subjects investigated in this dissertation included the followings:①Influence of nutrients (carbon or phosphorus limitation) on growth ofsuspended bacteria and the ratio of carbon and phosphorus in the nutrientsused by suspended bacteria; ②Factors affecting regrowth of suspendedbacteria in Jieyuan drinking water distribution system; ③Standards evaluatingbiostability of drinking water and measures to control bacterial regrowth indrinking water systems; ④Removal efficiency of pollutants by conventionaltreatment process. Based on the research, the following conclusions can be drawn: 1. Phosphorus can promote suspended bacteria growth. Firstly, phosphorus can shorten the lag phase of bacterial growth evidently. Secondly, phosphorus can increase the growth rate of suspended bacteria. Thirdly, the maximum cell count in stationary phase of water samples with higher phosphorus concentration was more than that of lower phosphorus concentration. However, carbon can only increase the maximum cell count. So, it can be more effectively to control bacteria regrowth by reducing the phosphorus concentration of drinking water. 2. When the phosphorus concentration was less than 0.7μg/L in laboratory-scale water samples, it was very difficult for suspended bacteria to obtain phosphorus, and then growth of suspended bacteria was very slow or in lag phase in the first nine days of incubation time. To limit the regrowth of bacteria in drinking water, concentration of microbially available phosphorus (MAP) should be below 0.7μgPO4 -P/L in drinking water distribution systems without 3- chlorine disinfection. - II -3. The ratio of AOC:MAP in nutrients used by suspended bacteria approximates 100:5 under oligosaprobic condition. 4. Suspended bacteria regrowth was influenced mainly by assimilable organic carbon (AOC) with low chlorine residual of Jieyuan distribution system. In some points of the distribution system, phosphorus limited suspended bacteria regrowth. However, in the whole distribution system, phosphorus did not limited bacterial regrowth because of higher phosphorus concentration. There was a linear relationship between the maximum heterotrophic plate count (HPC) and the maximum AOC concentration of the distribution system. 5. Average removal efficiency of total phosphorus (TP) by conventional treatment process was 65.4%. Removal efficiency of TP affected by water temperature. The higher water temperature made the higher removal efficiency. Removal efficiency of TP by coagulation-sedimentation and filtration were similar. Average removal efficiency of MAP by conventional treatment process was 57.4%.Coagulation-sedimentation removed MAP more efficiently than filtration.
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