An appropriate appraisal of the water quality parameters has an essential contribution in identification of main pollution factors in a certain region. In Romania, the lower course of Danube River Basin covers more than 1,075 kilometres and a significant percentage of the population lives in this area and depends on the Danube for potable water, industry, agriculture, and transport. The biodiversity, species and habitats, is markedly significant, taking in account that the Danube is the largest uninterrupted wetland area in the world and one of the last relatively undisturbed regions of Europe. The main focus of this article is to analyze the capability of chlorine removal in the municipal wastewater treatment plants in five counties of Romania, starting from 2013 to 2017. The five years average of influent fluctuates from 77.56 mg/dm3 to 111.03 mg/dm3 comparing with 82.94 mg/dm3 and 116.29 mg/dm3 the average of effluent. It should be specified that the limit imposed by the European legislation is 500 mg/dm3. Even if the measured values are below a quarter of the imposed limit, chlorinated wastewaters can be poisonous and may have a harmful impact on aquatic flora and fauna that are exposed to them, and consequently, that chlorination dechlorination might not be appropriate treatment approach for the protection of receiving waters.