09 February 2012What are Biosolids?
Several farms in Sevenoaks District Council's area use sewage sludge as fertiliser on their fields. Sewage sludge is the residue collected after treatment of the contents of urban drainage systems. Although the bulk of the sludge is from human waste, it may contain industrial and food processing effluent as well as run-off water from roads and pavements.
Incidentally, the Chartered Institution of Water and Environmental Management (CIWEM) considers the term 'sewage sludge' as misleading as up to 40% of the solids are biomass that has grown during the wastewater treatment process and were not originally present in the sewage, so sewage sludge should be labelled as biosolids or humanure.
Why are they used?
The use of these biosolids on farmland completes nutrient cycles and conserves organic matter. It feeds the soil and promotes better structure and life within the soil. When biosolids are used on land, they substitute for part of the mineral fertiliser needs of crops and because of the gradual release nature of the nutrients, the crops are frequently healthier and may need fewer applications of crop protection chemicals.
Generally, the treatment and use of biosolids are done efficiently in the United Kingdom. However, to ensure environmental, animal and human health protection; to guarantee the continued availability of agricultural land for the beneficial use of biosolids and other residuals; to meet current and future stakeholder concerns; there has to be a consistent framework of controls for all residuals applied to land. The risk of adverse environmental impact when biosolids are used on agricultural land is controlled through the soil limit values set in the Sludge Regulations. These limit values are based on sound scientific information and are continually reviewed.
How are they used?
Using raw or untreated biosolids on agricultural land was stopped on 31st December 2005 and now there is strict regulation of the use of treated biosolids. How they must be applied (generally by injection into the soil) and the subsequent use of the land, whether for food or forage crops or grazing, is detailed in the Code of Practice For Agricultural Use of Sewage Sludge.
For further information you can download The District Council's Information Sheet:
Agricultural use of Sewage Sludge, Humanure, Biosolids (
PDF File 72KB file details)or contact:
The Environmental Health Department
Community and Planning Services
PO Box 183
Argyle Road
Sevenoaks
Kent TN13 1GN
environmental.protection@sevenoaks.gov.uk
