Biosolids recycling to land in North-west England

The EU Urban Waste Water Treatment Directive (91/271/EEC) required an end to the disposal of sewage to sea from the end of 1998, meaning options for recycling sewage sludge to land had to be explored in the UK.

Land Research Associates was first retained by United Utilities (formerly North West Water) to review the potential market for recycling the outputs of a large (>100,000 tonnes/annum) sewage sludge incineration and recycling centre planned for the Mersey Valley near Warrington. Our initial studies indicated that dewatered sludge cake (biosolids) would be a potential soil improver and seedbed fertiliser for arable cropping, as well as being suitable for enhancing or creating soils on degraded former industrial land and mineral extraction sites.

Once the potential of the agricultural recycling option had been confirmed by positive responses from farmer questionnaires, a five-year programme was commenced comprising:

• Crop trials to determine optimum application rates and the fertiliser replacement value of the product
• Environmental monitoring of the risk to controlled waters of nutrient leaching from the root zone
• Trials to establish the most suitable equipment for spreading biosolids evenly onto agricultural land

Following this successful programme, agricultural marketing brochures were produced, negotiation conducted with farmers and soils were sampled for analysis to meet the Sludge Use in Agriculture regulations. The result was the establishment of a 15,000 ha landbank onto which the target volume of biosolids could be recycled.

Work was undertaken in following years for a United Utilities initiative to recycle biopellets to agriculture from a sludge drying plant.

As concerns to controlled waters of nitrate leaching increased and Nitrate Vulnerable Zones were extended to protect aquifers and surface waters, LRA designed a detailed spreadsheet to assess the impact to United Utilities on their available landbank and to assist strategic planning.

For further information on how we can assist in the recycling of biosolids contact us on +44 (0)1509 670570 or email mike.palmer@lra.co.uk