Using water industry data to assess the metaldehyde pollution problem

The presence of metaldehyde in raw and treated water has become a recognised problem recently. The current study used water industry monitoring data collected over a two and a half-year period (2008-2011) to quantify the presence of metaldehyde in rivers and finished waters. Measured surface water concentrations were then compared with catchment characteristics in an attempt to identify those factors driving losses of the pesticide to water. An assessment was also made of the robustness of the monitoring strategy used, which was assumed to represent typical water industry practice, and is currently being used to develop catchment management plans. It was found that exceedance of the European Union pesticide standard (0.1μg/L) during the October-December slug pellet application period is commonplace. Peak concentrations were generally in the 0.4-0.6μg/L range although sometimes were an order of magnitude higher.