Romania is making efforts in order to enforce the Directive concerning urban waste water treatment and was left behind by other member states. Starting from the premise that the lack of a proper treatment of wastewater can negatively influence the quality of the emissary in which they are discharged., we proposed that in this paper we analyze the main indicators of wastewater quality, identifying also the causes of water pollution. For this purpose, we followed the variation of five representative indicators of wastewater from Calarasi Wastewater Treatment Plan: chemical oxygen consumption, biochemical oxygen consumption, total nitrogen, total phosphorus, suspended solids. The best results in purification were observed regarding the biochemical oxygen consumption (over 95%). The low temperature of wastewater at the entrance to the Wastewater Treatment Plant during winter leads to a difficult exploitation of the biological step and implicitly to the increase of the phosphorus and total nitrogen concentration in the effluent, which means a weak process of eutrophication in the emissary.

Due to human activity, there are some changes in the composition of surface waters, especially near the industrial plants and cities. Wastewater, insuf iciently treated, affects negatively the quality of the emissary they reach.The discharge of poorly treated municipal sewage and industrial surface waste water has serious consequences for the natural phenomenon of self-puri ication, water Borcea branch and the Danube are now reaching the limits of the natural possibilities of biogeochemical balance recovery.In the present study two sources of waste water were taken into discussion, with important contribution of pollutants reaching the terminal basin of the Danube from the Waste Water Treatment of Călăraşi town and a meat processing plant, representative for the businesses in the county. The indicators followed in the study were: chemical consume of oxygen, biochemical consume of oxygen, ammonia nitrogen, total phosphorus.In recent months, by the rehabilitations that have been already made in the treatment plant, the water quality discharged into the environment improved, from physical chemical point of view.From the evolution of the main indicators analyzed, it is found out a decrease in content of organic substances and water eutrophication agents (total phosphorus and ammonium ion), their values reaching nearer to the standards required by the legislation in force.