CHLORINATED WATERS DISCHARGED TO THE MARINE-ENVIRONMENT CHEMISTRY AND ENVIRONMENTAL-IMPACT - AN OVERVIEW

Chlorinated discharges into coastal waters are of great environmental concern because of the large amount of chlorine and the diversity of the compounds involved. Seawater chlorination for cooling systems and disinfection of urban wastewaters are the major sources of these hazardous compounds reaching the marine environment. Seawater chlorination (at the mg . l-1 level) produces bromine which disappears rapidly in receiving waters yielding organobrominated compounds. Chlorination of urban wastewaters, containing high concentrations of organic carbon and ammonia, requires higher chlorine dosage (5-20 mg . l-1) to fulfill the disinfection requirements. Monochloramine still active is the predominant final compound. Organochlorinated by-products represent a minor part of the added compound; however they need further investigations to precisely evaluate their potential hazard to marine life because of their persistence and mutagenic character. For chlorine produced oxidants first signs of deleterious effects appear at concentrations as low as 0.1 mg . l-1, about two orders of magnitude lower than the actual concentrations in chlorinated effluents.