By measuring the COD (chemical oxygen demend) of dish washing detergents being sold at market and pollutants connected with domestic sewage, we compared the amounts of water pollutants of one with other and carried out the experiments of ultimate biodegradation as against these samples. Also we combined our experimental results and circumstances of water pollution and wastewater treatments to the sewage system, compared the effects of synthetic detergent on water pollution with soap and the other pollutants and investigated results of our research.