Increase in population and development of various industrial and agricultural activities, makes supply of enough water with appropriate quality an ever increasing difficult task. On the basis of various researches different types of hazardous and perhaps dangerous chemical substances have been observed in the water supply reservoirs of large cities. A large proportion of these chemical substances contain organic material. Drinking water of Tehran city is mainly from free surface sources which are treated in ordinary plants where no units are considered for removal of organic pollutants. Therefore, knowledge of the organic materials is necessary. In the present research, the inflow of the organic material to the treatment plant emphasizing on TOC and also percentage of its removal were measured separately from April to October. Considering the average concentration of the organic material on the plant outflow, changes are necessary in conventional water treatment plants. In majority of the treatment plants including present case, disinfection byproduct is carried out before pre-chlorination. Therefore production of side materials from primary disinfection is not impossible and solutions are suggested accordingly. Finally, the TOC in sewerage resulted by wash out of the filters and raw water are compared.
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