The use of nutshell carbons in drinking water filters for removal of chlorination by-products

Chlorination of drinking water is a common practice, used by numerous municipalities in the United States (US) to safeguard their water supplies. However, the chlorine used can chemically react with organic components in the drinking water to produce unwanted chlorination by-products. The objective of this investigation was to evaluate the use of granular activated carbon produced from nutshells (almond, English walnut, pecan) in a point-of-use (POU) water filtration system designated ‘Envirofilter’ and to determine its efficacy in removing select, potentially carcinogenic chlorination by-products, namely the trihalomethanes (THMs) bromodichloromethane, bromoform and dibromochloromethane. The POU water filtration system that contained the nutshell-based carbons was designated ‘Envirofilter’ and adsorption efficiencies of this system were compared to that of four commercially available POU home water filter systems, namely, BRITA, Omni Filter, PUR and Teledyne Water Pik. Eight different ‘Envirofilters’ were constructed of individual or binary mixtures of carbons produced from acid-activated almond or pecan shells and steam-activated pecan or walnut shells and evaluated for adsorption of the three chlorination by-products. The results indicate that only two of the eight ‘Envirofilters’ failed to remove more THMs than the commercial POU systems. In both cases, these filters contained carbons with either 100% acid-activated almond shells or 100% acid-activated pecan shells. All six of the other filters contained carbons with either 50% or 100% steam-activated pecan shells or steam-activated walnut shells. Therefore, ‘Envirofilters’ appeared to depend on the presence of steam-activated nutshell carbons for their success. The six effective ‘Envirofilters’ reduced THM levels to below the Maximum Contaminant Levels (MCL) required by the US Environmental Protection Agency (US EPA). Based on these results, these six ‘Envirofilters’ may be considered as a replacement for existing commercial filter systems because of their efficacy and projected cost.  2004 Society of Chemical Industry