Chlorination of Water: Correlation of THM formation with fluorescence shift

Abstract

The practice of disinfection is used for killing pathogens and make water safe for drinking and other purposes. Chlorine is widely used as disinfectant because of its easy availability, cost effectiveness and residual effect. But the use of chlorine as a water disinfectant has come under scrutiny because of its potential to react with natural organic matter (NOM) and form disinfection by products (DBPs). In addition to being highly influenced by the type of organic and inorganic matter in the source water, the different species and concentration of DBPs vary according to the type of disinfectant use, the dose of the disinfectant, the concentration and nature of NOM, the time since dosing, temperature and pH of water (Singer and Reckhow, 1999). Trihalomethanes (THMs) and Haloacetic Acids (HAAs) are two most prevalent class of DBPs obtained during chlorination of drinking water. They are regarded as carcinogens and are regulated due to the health risk they pose. Fluorescence is the property of a material to absorb certain wavelength of energy and emit the higher wavelengths from excited singlets. The substances which show fluorescence are called fluorophores. NOM is a fluorophore. During chlorination, the degradation of the natural organic matter results in a shift in fluorescence which can be measured using fluorescence spectrophotometers and can be correlated with the disinfection by products formed (Roccaro et al, 2009). The objective of the present work is to devise a model to predict THM formation with the help of shift in fluorescence. Additionally, develop a model to measure residual chlorine content with the use of absorbance spectroscopy and eliminate the use of additional chemicals as - presently used in DPD method.