FATE OF PHOSPHORUS DURING ANAEROBIC DIGESTION OF SLUDGE FROM AN EBPR PLANT
S. Bungay 1, K. Chapman 2, A. Buchanan 3, J. Crassweller 4, L. Barnes 5, M. Smyth 6
1Black & Veatch, 2Mott MacDonald, 3Black & Veatch, 4Black & Veatch, 5Anglian Water, and 6Aqua Enviro Ltd.
(free)
As part of their ongoing commitment to produce safe sewage sludge for recycling to agricultural land, Anglian
Water are expanding their enhanced sludge treatment operations at four key sites across the Eastern region.
The project at Whitlingham STW uses thermal hydrolysis as a pre-treatment to anaerobic digestion as the main
sludge treatment process. As well as producing an enhanced treated sludge, the thermal hydrolysis process
facilitates increased volatile solids destruction, and subsequent biogas production. The hydrolysed and
digested sludge will be dewatered to sludge cake for recycling to agriculture. The biogas will be used for energy
generation for use on-site.
As a consequence of the increased volatile destruction, the dewatering liquors will contain elevated levels of
ammonia and phosphorus, which will be recycled to the main works for treatment. This works is an EBPR plant.
Therefore, it is essential that any phosphorus removed from the main sewage flow by the EBPR is not simply
recycled back via the sludge treatment stream, and that the levels of recycled phosphorus and ammonia do not
exceed the capacity of the works to treat it. This paper investigates the fate of phosphorus during anaerobic
digestion in order to establish the amount of phosphorus, which is likely to remain in a dissolved form and
therefore be recycled back to the EBPR plant, as well as the levels of recycled ammonia, so that the
requirements for any side-stream treatment can be established.
KEY WORDS
Fixation, Liquor Treatment, Phosphorus, Precipitation, Struvite
