Proceedings

Over 80% of the sewage sludge in the UK is recycled to agricultural land. The sustainability of this approach to sludge management is highly dependent on ensuring the chemical and microbiological quality of sludge is of an exceptional standard. The chemical composition of sludge and microbial indicator organisms are routinely measured by the UK Water Utilities. However, information on sludge quality is not
published routinely, so the significant improvements in the quality of sludge which have taken place in recent years, that underpin the practice of beneficial land spreading, are not generally known. In collaboration with several major Water Utility companies in the UK, we have completed a critical statistical analysis of historical and contemporary sludge quality data. Here we show an example of the trace element composition results for Thames Water.

The statistical analysis shows the time trend decrease both in concentrations of upper ranges and the overall average concentrations of trace elements and, in some cases, a reduction of up to 50-60 % has occurred in the past 15 years.