Water Quality
Sewage sludge – application to agricultural land
Provided it is carried out in accordance with good practice guidance, recycling to agricultural land for agricultural benefit or ecological improvement is the Best Practical Environmental Option for sewage sludge in most circumstances. It provides the soil with plant nutrients and organic matter, which plays a key role in retaining good soil structure and water holding capacity, and is a sustainable alternative to the use of inorganic fertilisers.
To ensure the beneficial effects of sludge spreading it needs to be subject to appropriate controls based on sound science. The regulatory regime and the latest findings from Defra research are set out below.
Controls
The EC Sewage Sludge (Use in Agriculture) Directive (86/278/EEC) regulates sludge spreading in order to “prevent harmful effects on soil, vegetation, animals and man”. It is transposed through the following regulations:
- The Sludge (Use in Agriculture) Regulations 1989
- The Sludge (Use in Agriculture) (Amendment) Regulations 1990
These are supported by the Code of Practice for Agricultural Use of Sewage Sludge (PDF 140 KB)
In addition to these controls, the water industry and the British Retail Consortium have agreed a voluntary Safe Sludge Matrix (PDF on ADAS website) which is followed by all water companies.
Research
There is an extensive body of research relating to sewage sludge. The following reports may be of particular interest:
- A review of recent research Defra project WT03051
- Pathogens in biosolids – microbiological risk assessment (PDF 180 KB)
An on-going experiment into the effects of metals in sludge on the long-term soil fertility was established following an investigation by an independent scientific committee in 1993.
1. Report on soil fertility aspects of potentially toxic elements
2. Report on food safety and relevant animal health aspects of potentially toxic elements.
The latest interim results from the experiments, and further information, can be viewed on the science pages:
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Page published: 28 November 2007