HUMAN HEALTH RISK ASSESSMENT BY EXPOSURE TO CHLORINATION BY-PRODUCTS OF WATER FROM PUBLIC SUPPLY SYSTEM
chlorination by-products; trihalomethanes; health risk; filter backwash water recycling; algae bloom.
In front to the population growth and the degradation of water quality from public supply sources, it is becoming challenging supply to populations of safe water with ideal quality and quantity through the most commonly used treatment technologies. Water treatment plants (WTP) are constituted by different treatment technologies worldwide used. The processes of filtration and disinfection are required in the water treatment for human supply. However, in these processes there may be the generation of residues or by-products that could cause health risks to the population. A systematic review about toxicologic aspect of trihalomethanes (THM) generated in the disinfection process by chlorination of water from supply distribution system, in which the cytotoxic, genotoxic and mutagenic of THM was shown along with the demonstration of the need for studies aimed assess in a more realistic way the exposure condition of the population to this family of toxic substances. Moreover this study propose to assess the efficiency of the water potability treatment from a water net supply and the related health risks linked to the THMs exposure through the public water distribution system. Physico-chemical, microbiological and hydrobiological analyses were performed. The results showed that the THM´s formation is related to chlorination conditions, such as contact time and concentration of it, as well as the raw water characteristics, such as the concentration and properties of organic matter. However, the filter washing water (FWW) treated in a sedimentation pond and recirculated in the system contributed to the cyanobacterial bloom, which are potentially producing cyanotoxins. Public supply water treated in a source with high organic matter, direct filtration, FWW recirculation and chlorine disinfection has sanitary risks due to the high THMs formation. In this way, it is evident that the WTP operationalization concept for treating raw water with high organic matter loading poses risks to the population supplied, since they contribute to the formation of high concentrations of THM and the non-carcinogenic and carcinogenic risks of exposure the amount of these compounds to consumers of treated water from a tropical lagoon.