Enhanced biological phosphorus removal using sludge liquor
Farrant, L.1, Le, M.S.2, Phipps, D.1 and Al Khaddar, R.1 1Liverpool John Moores University, UK, 2United Utilities PLC, UK
(free)
This paper reports recent findings from both bench and pilot scale studies of biological nutrient removal (BNR) from wastewater using sludge liquor as a carbon source.
The Urban Waste Water Treatment Directive (91/271/EEC) was adopted by all EU member states in 1991 raising the need for effective nutrient removal processes. Current infraction proceedings against the UK government in Brussels over the nutrient status of the North East Irish Sea (NEIS) has injected more urgency into the situation and heightened the requirement for more sustainable treatment processes, particularly for dealing with phosphorus. The cost implications of implementing nitrogen and phosphorus removal for NEIS are huge, not only in financial terms but also in terms of customer affordability and carbon foot printing. Such drivers have provided United Utilities the incentive to seek further improvements in process reliability for the more sustainable alternative, Enhanced Biological Phosphorus Removal (EBPR).
The successful operation of EBPR requires that the process influent contains a sufficient and reliable concentration of a suitable carbon source, preferably in the form of volatile fatty acids (VFA). Traditionally, this is provided by a fermenter or by the direct addition of an external carbon source making EBPR an expensive option. This study details the results from an experimental programme for EBPR removal from wastewater using sludge liquor as a carbon source for improved process reliability. In this study, liquor from Inverted Phase Fermentation (IPF), a novel sludge thickening process, has provided a convenient source of VFA. If phosphate accumulating organisms can readily utilise IPF liquor as a carbon source, this would eliminate the need for an external carbon source or a more costly online fermenter.
Bench scale tests, using the EBPR process in a sequencing batch reactor (SBR), have shown the IPF liquor to be suitable carbon source for the process. These results and the outcome from a more recent EBPR pilot plant trial utilising IPF liquor in a continuous process which could be transferred to full scale are also reported.
Key words: wastewater, EBPR, Inverted Phase Fermentation, carbon source
