Arsenic in groundwater in New England - point-of-entry and point-of-use treatment of private wells

摘要

Arsenic in drinking water is a factor that has recently been shown to be a possible cause for an elevated bladder cancer risk in northern New England. More than 40% of the population in this region uses private wells as the primary drinking water source. Point-of-entry (POE) and point-of-use (POU) arsenic removal systems can be an attractive and effective way for a well owner to treat the water to reduce the arsenic level to below the US EPA maximum contaminant level (MCL) of 10 μg/L (10 ppb). A study based on data collected from customers in eastern New England and New Jersey has been conducted to identify areas with elevated arsenic concentrations and to assess the performance of installed POE and POU devices based on arsenic adsorption on hybrid hydrous iron oxide/ polymer media. The first of these arsenic treatment systems became operational in November 2005 and as of August 26,2007, a total of 275 systems has been installed. The raw water from all the systems was sampled at startup and 62 have since been re-sampled. Of the tested waters, 77% had arsenic concentrations less than 50 ppb which was the US EPA MCL for arsenic until January 2006. At this level, the lead column of the POE system would be expected to last for a minimum of 1.5 years in most waters before replacement is required. However, the actual life of the media column will depend upon the volume of processed water and the water chemistry (arsenic speciation, silica, phosphate and pH). To date, the collected data seem to fall into areas that have been identified by the US Geological Survey for the New England region and the New Jersey Geological Survey in New Jersey as having high arsenic concentrations in the groundwater. Periodic arsenic analyses of the customer waters have shown that the POE and POU systems operate as predicted and meet the needs of the customers in terms of arsenic removal and ease of operation. Only 10 systems have required replacement of the exhausted lead column since becoming operational, which is 4.2% of all installed devices. This means that even in challenging conditions the lead column effectively operates for an average of 10-12 months.