New Treatment Processes for Pesticides and Chlorinated Organics Control in Drinking Water

Sources of pesticides and chlorinated organic compounds potentially found in water sources are reviewed. International and UK drinking water standards for these compounds are discussed and compared with concentrations found in ground and surface waters derived from lowland agricultural and urban areas. Water soluble herbicides including triazines, phenylamides (urons) and chlorophenoxy acids are the most commonly reported types of pesticide compounds found above 0.1 μg/l in water sources. The more toxic, and less water soluble, organo-chlorine and organophosphorus pesticides are rarely reported. Chlorinated organic solvents are reported as contaminants of some groundwaters. Disinfection by-products, in particular trihalomethanes, formed during the chlorination of waters containing natural organics, are widely reported, sometimes at concentrations above current UK standards. The effects of conventional water-treatment processes on the concentrations of these organic compounds are discussed. Additional water-treatment processes, designed specifically for trace organic micropollutant removal, are identified and reviewed. Ozonation, activated-carbon adsorption and air stripping are acknowledged as appropriate advanced water-treatment process solutions. Developments in novel technologies include organics destruction via advanced oxidation processes, biological processes, membrane technology and novel adsorbents. Thames Water Plc is contributing to research in this area, investing over £5 million in pilot- and large-scale trials prior to a £200-£300 million capital investment programme in advanced water treatment in the 1990s.