| In recent years, T. tubifex are reported propagating excessively in water sources due to the large amount of nutrients input. Once the worm enters water plant along with source water, it can penetrate water treatment for high stretching and disinfectant resistance capability, which results in worm pollution in drinking water distribution systems. The main objective of present research was to supply the theoretic proof for water plant to forecast and control the worm pollution. The study first aimed at the worm life habit and rules of growth and reproduction. The effects of temperature, DO and sediment property on worm migration were investigated by stimulating worm migration activity in lab. Second, worms were inactivated by adopting oxidants and copper as inactivators. The inactivation mechanisms of the above inactivators were investigated by assessing the change of·OH concentration, Antioxidant enzyme Catalase (CAT) activity and lipid peroxidation produce malondialderhyde (MDA). At last, the worm interception efficiencies of traditional water treatment were investigated in a pilot-scale study. Addition, the influence of pre-oxidation with ClO2 on the interception efficiency of traditional water treatment was also studied. The present major results were showed as follows:T.tubife showed strong adaptability to temperature, DO and pH. Survival, growth and reproduction were observed at temperature of 10℃～30℃, DO content of 0.5 mg·L-1～8mg·L-1 and pH of 3～11. The migration in water-sediment interface can be influenced by both temperature and DO. Moreover, the increase of temperature can significantly improve T. tubifex innate growth capacity and reduce the average generation cycle and the population doubling time;The inactivation results indicated that oxidants such as Cl2, ClO2, KMnO4 and copper have the inactivation function to T. tubifex and The inactivation effect of the four chemicals in turn was ClO2> Cu> Cl2> KMnO4. The change of·OH concentration in T. tubifex showed that both oxidants and copper had obvious·OH inducing effect and oxidative stress expect for KMnO4.The coagulation had interception effect on T. tubifex, and its efficiency was relate to coagulation conditions. The extension of coagulation time is helpful to improve interception effect. In present test, the highest interception efficiency of 52.8% was obtained with program 4 (100 r·min-1,50 r·min-1,0 r·min-1); The optimal coagulant dosing for worm interception was 22 mg·L-1, of which the interception efficiency was 41%. Remarkable Interception effect of sand filter to T. tubifex was observed in present test. Based on the experimental results, to control the worm leakage risk effectively, filtration rate and cycle should be lower than 9.4m/h and 12h, respectively. Backwashing intensity should be controlled about 25L·s-1·m-2, at which 97.7% T. tubifex removal efficiency was obtained.Pre-oxidation with ClO2 can improve interception effect of coagulation on T. tubifex obviously. The interception efficiencies were increased respectively from 28.5% to 92.9%,89.9% and 93.1% under the ClO2 content of 0.05mg·L-1, 0.1mg·L-1 and 0.2mg·L-1. Low ClO2 content (0.05mg·L-1) promoted the migration of worms in sand filter and decreased it interception efficiency. However, high ClO2 content enhanced the interception efficiency of sand filter to the worm, In present test,100% interception efficiency was obtained at ClO2 content of 0.1mg·L-1 and 0.2mg·L-1.The present results indicated that T. tubifex can propagate massively in source water, particularly in polluted source water because of its special life habit. At the same time, the worm can enter water plant by drift migration from sediment to overlying water and results in its pollution in drinking water distribution system eventually. Though most worms are intercepted by the traditional water treatment processes, there are still some worms that can penetrate the whole water treatment processes. Significant inactivation effect of ClO2 on T. tubifex was obtained for its remarkable OH inductive effect and strong fat-soluble. It is hopeful to solve the worm pollution in water plant by combining traditional water treatment processes with Pre-oxidation with ClO2.
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