TOXICITY OF DOMESTIC AND INDUSTRIAL WASTEWATER FROM HOCHIMINH CITY CANALS SYSTEM

Abstract

The aim of this study is to evaluate the contamination level and the ecotoxicological risk of surface water of the five canals in Ho Chi Minh City. It responds to an urgent need and fills a gap of knowledge concerning the toxicity of wastewater for the receiving media in Vietnam. This evaluation is carried out by applying ecotoxicological tests with the organisms Daphnia magna, Ceriodaphnia cornuta and Vibrio fisheri, as well as the measurement of heavy metals and traditional physicochemical parameters such as the chemical oxygen demand COD and the biochemical oxygen demand BOD5. The results of the analysis of thirty two water samples taken in as many points distributed along the canal show a strong presence of heavy metals. The water samples are characterized by high COD and BOD5, with typical values for domestic wastewater. The ecotoxicological tests show for their part an acute toxicity of all surface water samples of the canals, with 50% effect concentrations (EC50) are almost classified as toxic. This observed acute toxicity indicates that the organisms living in the canal are affected and shows the need of sanitation of canals. In addition to regular dredging of sediments currently carried out, various actions could be planned to protect this canal against the contamination, the most important being to act in the origin of the pollution. The installation of treatment systems on a small scale based on low cost technologies using some physical or biological processes should also be considered. But in addition to these technical aspects, the awareness of the population regarding the importance of environmental protection needs to be reinforced.