A contemporary and historical analysis of the trace element composition of sewage sludge in the United Kingdom

Abstract

Sewage sludge is the essential by‐product of wastewater treatment and approaching 100% of the sludge generated in the United Kingdom is recycled to agricultural land. In collaboration with three major Water Utility companies in the United Kingdom, a critical statistical analysis of historical and contemporary sludge quality data was completed to demonstrate the long‐term patterns and improvements in the trace element (TE) content of sludge recycled to agriculture since 1989, and to indicate the current status of sludge quality in the United Kingdom. Comparisons with pollutant emission inventory data showed most of the TE concentrations in sludge were strongly linked to declining environmental emissions. A soil accumulation model showed that zinc and copper would be the first to approach their statutory soil limits in the long term and that nickel, cadmium, lead and mercury are no longer significant and, from a practical perspective, could be removed from the regulatory controls on agricultural use.

Environmental Forensic

“…• In the study of Liu et al (2021), the mean Cu concentration has remained relatively static and contemporary concentrations are similar to those observed in the early 1990s.…”

“…• Liu et al (2021) reported data from 75 wastewater treatment plants (WWTPs) in the United Kingdom, for the period 1989-2017. Only inorganic compounds (heavy metals mostly) were statically analysed: Zn, Cu, Ni, Pb, Cd, Hg, Cr, Mo, As, Se and F. The study showed that trace element concentrations decreased significantly in response to declining pollutant emissions, demonstrating the environmental benefits of effective source control and cleaner technologies.…”

Agricultural soils and microplastics: Are biosolids the problem?

“…Switzerland) have placed restrictions on the use of biosolid application to land based on the potential impact of persistent pollutants (9,10). However, in the UK, almost all biosolids produced are spread on agricultural land (11). Wastewater treatment systems are designed to primarily remove biochemical oxygen demand, suspended solids, and ammonia.…”