Evaluation of wastewater quality using water quality index

A study for evaluating the quality of wastewater discharged into the sewerage network of Bucharest, for several economic agents with various activity profiles: a car wash, a sweet producer, and a provider of automatic access systems were presented in this paper. The study was conducted over a period of five years (2013 2017). The results obtained for the analyzed parameters were compared with the maximum allowed values (MAV) by the legislation in force. The results showed that for the car wash there was only one exceeding of the chemical oxygen demand (COD) parameter during the whole study period. The sweet producer and the provider of the automatic access systems evacuated wastewater with exceedances of MAV for the parameters: COD, biochemical oxygen demand (BOD5), zinc, suspended solids, extractable substances in organic solvents, and total phosphorus. In order to evaluate the quality of the wastewater discharged by these two agents, the quality indices of wastewater (WWQI) were calculated. For the sweet producer, the calculated water quality indices had values between 62.4 - 92.7%, with a classification of wastewater, discharged in the quality class: marginal to good quality. For the provider of automatic access systems, the value of the quality index was between 74.2 and 85.5, the discharged wastewater being considered fair or good.