CONTROLLING ODOUR FROM STORED CENTRIFUGED DIGESTED SLUDGE (BIOSOLIDS)
(1)Matt J. Lovell, (2)Phil Hobbs, (2)Jon Williams, (2)David Chadwick, (1)Richard Smith
(1)Severn Trent Water Ltd., UK
(2)Institute of Grasslands and Environmental Research (IGER), UK
(free)
The aim of this work was to reduce odour production from disturbed/handled digested sludge cake that had undergone several months of storage. Phase 1 of the project tested chemical and physical additives mixed with digested sludge cake, at a ratio of 2:3 additive to cake (volume basis) contained in 60 litre barrels. Headspace analysis of the surfactant additives, Sodium Dodecyl Sulphate and Rape Seed oil, and the sterilisation additive, Calcium Cyanamide and Hydrogen Peroxide showed that odorant emissions increased relative to the control and so were considered unsuccessful. Solids analysis of the barley straw, bark chippings and compost (the physical additives) suggested that they adsorbed sulphides. Consequently, they were chosen for further investigation in Phase II, which was at the larger 5-ton stockpile scale. This was conducted in concrete bunkers at a ratio of 1:2 additive to cake by volume (1:4 by weight). All three additives reduced actual odour emissions approximately 5 times at the point of moving the stockpiles after 2 months storage. The additives also reduced odour emission rates from land spreading by a factor of 3, with bark chipping being marginally better than straw and compost.
KEY WORDS Additives, Biosolids, Compost, GCMS, Hydrogen Sulphide, Odour, Odorant, Olfactometry, Straw, Sludge Cake, Sulphides, VOCs, Wood Chippings.
