Draft PPS18: Renewable Energy
Annex 1 Energy from Waste (Biological Processes) Planning Issues: Sewage Gas
Site selection, Transport and Traffic
C47. In general terms, sites for sewage digestion plant will be influenced by the presence of a suitable wastewater treatment plant. At a site-specific level the location of the sludge digesters is likely to be dictated by the constraints of other systems to which they are linked at a treatment works. It is sometimes the case that some sludge is transported to wastewater treatment plants by tanker, and therefore there may be some local variation in siting in relation to the logistics of sludge transportation.
Feedstocks and Product Storage
C48. Sewage sludge is not generally stored in liquid form for extended periods of time. There are however usually intermediate storage tanks which act as buffers for variations in flow or input from sludge tankers.
C49. Given that sewage sludge digesters are normally located at wastewater treatment works, odour emissions are likely to be dominated by the primary treatment processes (settlement/aerobic treatment), which usually take place in open tanks.
Emissions to Air, Ground and Watercourses
C50. Issues will be broadly the same as those described under anaerobic digestion. They are likely to be addressed as part of the collection of operations of a wastewater treatment works.