reatment plant effluent quality (particle count and particle size)

City of Tehran uses surface water to supply drinking water to more than 10 million populations by five large water treatment plants .Tehran water treatment plants consists of pre-treatment, coagulation, flocculation, filtration and disinfection units (conventional treatment).Plants effluent quality is in compliance with WHO standards . Drinking water standards these days are getting more stringent because of our knowledge about pollutants and the development in measurement instruments. Meeting new drinking water standards which will be enforced by regulatory agency in future is a challenge of water industry. Removal of micro organisms such as Giardia, cryptosporidium, DBD, TOC and particle size and particle count are playing a more important role in new standards. In this experimental study a conventional pilot plant was designed, built and used during six months to study the effect of type and dose of coagulant, filtration rate on particle count and particle size of treated water .Particle size and count which is a surrogate measure for removal of pathogens such as bacteria, viruses, Giardia, Lambia, and Cryptosporidium. The results of this study indicated that filtration rate and type of coagulant dosage has more effect than the other operational parameters on overall effluent quality and on particle size and count.