Characteristics Of Iron Stability And Red Water Control In Drinking Water Distribution Systems

The object of this paper is to complete the theory systems of iron stability in drinking water distribution systems and control it. This paper includes the characteristic of iron bacteria in drinking water distribution systems, corrosion by iron bacteria, the control technology of iron bacteria, red water caused by water source switch and iron stability technology.Measure the iron bacteria in drinking water distribution systems of Tianjin and analyze the influencing factors on the iron bacteria. The count of iron bacteria is between 0 and 107cfu/mL which has a negative correlation with chlorine residual and the count in summer is more about 2log than it in winter. Two specieses of heterotrophic iron bacteria isolated from the water were Acinetobacter baumannii and Microbacterum oxydans. The inactivation of these iron bacteria was studied on and the results were that the chlorine residual should be 0.2mg/L to get 99% inactivation ratio.The characteristic of the attached iron bacteria and the corrosion it were carried out by Annular Reactor. Corrosion by iron bacteria was about 30% in the total corrosion. Hydraulics influence on iron bacteria level and corrosion rate of steady-state attached iron bacteria was not significant. When the chlorine residual was 0.3mg/L, the iron bacteria growth could be controlled effectively and suspended and attached iron bacteria levels both decreased 1 to 2 log, the corrosion rate reduced 40%. The corrosion rate was linearly dependent on the logarithm of attached iron bacteria which the suspended iron bacteria levels were linearly dependent on. The mechanics of iron bacteria acting in drinking water distribution systems was analysed. The control of iron bacteria in drinking water distribution systems was advanced.The red water caused by water source switch in some communities of Beijing was investigated, and large increase of sulfate concentration by water source shift was regarded as the cause of red water problem which was obtained by the index of water chemical stability and the experiments with pipe section reactor. High-sulfate- concentration source water broke the stable shell of scale in pipe and iron release occured, pipe water deteriorated. Water source ratio adjusting control measure was advanced and utilized in the practice, the problem amended and the tap water was improvement.Iron stability control technologies of chemical treatment were proposed, including adding phosphate, elevating pH and alkalinity and utilizing free chlorine as the disinfectant instead of chloramine. Adding polyphosphate was more effective, practical and cheaper than the other measures according to the bench and pilot scale experiments.