Evaluation of the effect of advanced coagulation process to optimize the removal of natural organic matter in water (Case study: drinking water of Mashhad’s Kardeh dam)

Natural Organic Matter (NOM) is a non-uniform mixture of organic compounds that enter water after synthesis of plants, animals, etc. Among the organic matters in natural waters, humic substances which usually exist as solutions have allocated a major portion to themselves and in addition to giving taste, color and odor to the water, they can intervene in the oxidization and removal of heavy metals such as arsenic, iron and manganese. Also, the natural organic precursors of disinfection by-products have been recognized as toxic or carcinogenic substances. The coagulation process is optimized as the most common system of water treatment in Iran for removing turbidity of water. This process is capable of removing the natural organic matter but the conditions for the removal of turbidity are constantly not identical with the optimum conditions for removing the NOM. Therefore, where NOM is the main pollutant, the traetment process should be optimized for removing NOM. Therefore, where NOM is the main pollutant, the traetment process should be optimized for removing NOM. After doing the common treatment, the water of Kardeh dam of Mashhad is used as drinking water of the city of Mashhad. By doing the water analysis experiments, the amounts of natural organic matter in the exiting water from water treatment plant was observed at 5 mg/l which is much higher than the world standards of drinking water. In this research the optimum conditions for the removal of NOM from drinking water of Kardeh dam have been examined. The experiments have been conducted at the laboratory scale and by Jar Test Device by different doses of two coagulants of alum and ferric chloride at various pH of water. It is concluded that these coagulation process by two coagulants remove NOM from drinking water and bring it to standards of US Environmental Protection Agency and World Health Organization. Keywords : advanced coagulation; natural organic matter; drinking water; city of Mashhad.