Hill, S.A. and Pollock, M., Wessex Water
(free)The cost of sending waste to landfill is increasing every year putting pressure on companies
to reduce and recycle more of their waste. For the UK water industry sewer grit and sewage
screenings has presented a difficult challenge when trying to find sustainable alternatives to
landfill. Currently the UK water industry landfills over 95% of this waste with projected
disposal costs of £12.6 to £16.8 million by 2010 (UKWIR, 2007).
Composting is a well established process for treating wastes with organic matter. The
characteristics of sewer grit and sewage screenings makes them favourable for a composting
process, which will reduce its volume and produce a sanitised, stabilised and saleable
product.
Open windrow composting was used in this study to reduce the volume of waste and produce
a final product called Primary Retrieved Biosolids (PRB). The process succeeded in reducing
the amount of waste to 15%, which currently requires land-filling. PRB produced from
composting is a gritty soil like material with an equivalent fertiliser value of £15.22 per tonne.
This product has been approved by the Environment Agency for recycling to agricultural land
under the Sludge (Use in Agriculture) regulations, 1989.
KEY WORDS
Agriculture, Biosolids, Composting, Fertiliser Application, Grit, Landfill Reduction, Recycling,
Screenings, Sewer Grit, Sewage Screenings
Aqua Enviro Ltd
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