Sludge phyto-conditioning: low-technology enhanced treatment

Agricultural recycling of biosolids is coming under increasing regulatory and non-regulatory pressure. The UK Government and the European Commission are introducing new microbiological standards for (a) sludge, (b) expanded nitrate vulnerable zones, and (c) more stringent maximum potentially toxic element concentrations in soils. Public perception continues to play an important and unpredictable role in the acceptability of biosolids agricultural recycling. Sludge phyto-conditioning is a low-technology process, growing grass on sewage sludge to produce a pleasant/low-odour compost-like material and reducing bacterial indicators to below detectable levels, whilst retaining the beneficial energy-recovery aspects of anaerobic digestion. This paper describes the process stream and discusses the benefits for the operator, including treatment to ‘enhanced’status and reduction in volume. The process is batch in nature and results in a high-quality soil conditioner.