Over the past months local residents have complained about foul smells hanging over the area which seemed to arise on the Industrial Estate. While not all odours can be traced to this source, the explanation below provides the likely reason.
Biosolids is another word for digested sewage sludge, which is the solid matter that is left when sewage is treated by the water industry. Sewage sludge contains nutrients and organic matter so it is widely used by farmers as a fertiliser and soil conditioner. Unfortunately sludge can also contain bacteria and other disease-causing organisms known as pathogens, so before it can be safely used on farmland, it must receive further treatment to destroy the pathogens.
The treatment process at Burscough airfield is known as ‘lime stabilisation’. Mixing it with lime sterilises the sewage sludge by raising the pH to above 12.
Lime stabilisation of sewage sludge is carried out under a permit issued by the Environment Agency. The permit allows the operator to treat the bio-solids for a period of 12 months, subject to certain conditions being met. This activity is classed as ‘temporary’ so it does not require planning permission. At Burscough, operating limits were set by the Environment Agency at a maximum of 10,000 tonnes of sludge treated per year. There is no daily limit and no restriction on the number of days of operation - it depends on the supply of sludge from the sewage works.
Once treated, the sludge is stockpiled before being moved off site to the farmland where it will be spread as a fertiliser. This can cause odours, during both the transfer process and the spreading itself.
The temporary permit at Burscough airfield expired on the 18th July 2017. The last load of biosolids accepted for treatment was on the 6th June. The treated sludge is now being moved off the airfield to land in the Croston area but the process had to be temporarily suspended because of the wet weather. When the ground conditions dry up, all the remaining biosolids will be removed from the site. This will take an estimated 4 or 5 days, depending on the weather. Once all the sludge is removed from the airfield site, the odours caused by the treatment process should subside.
Any particularly offensive odour generated from landspreading on farm land should be reported to the Local Authority Environmental Health Officers.