Ultrasonic destruction of trihalomethanes: optimization of system parameters

Abstract

Disinfection of drinking waters is a major public health triumph of our age. However, while the pathogenic microorganisms provide the primary health risk from drinking water, chemical disinfection by-products also introduce an unintended health hazard. Trihalomethanes are the most common by-products of disinfection with chlorination. Due to their carcinogenic properties, removal of trihalomethanes from drinking water has become an important public health concern. Research into the use of ultrasound in environmental protection has received a considerable amount of attention with the majority of investigations focusing on the harnessing of cavitational effects for the destruction of biological and chemical pollutants in water. Sonochemical removal of hydrophilic compounds has been investigated more than hydrophobic compounds. In this study sonolytical removal of trihalomethanes from aqueous solutions has been investigated. Chloroform was selected as a model compound for the investigation of factors affecting sonolytical trihalomethanes removal. The sonolytical removal of chloroform was studied at three distinct frequencies and at different power densities. The effect of different sparging gases on chloroform removal was investigated using argon, air, nitrogen and oxygen. The effect of hydroxyl radical reactions on chloroform removal was investigated through the use of radical scavangers. The effect of trihalomethanes combinations on the removal rates of chloroform and bromoform were investigated. The results obtained from the model compound studies were compared with results obtained from tap water treatment studies. Finally, the effect of sonolysis on the acute toxicity of tap water was investigated using the Microtox test method.