A Novel Biotechnological Approach To Phosphorus Removal From Wastewaters

Synthesis Report for the ERTDI project: 2005-ET-LS-10-M3

Summary: STRIVE Report 55 - John W. McGrath and John P. Quinn

The problem of eutrophication caused by the enrichment of water bodies through excessive nutrient inputs (particularly of phosphate) has become significant in Ireland and throughout the developed world. This project has attempted to develop an improved method to tackle the difficult problem of phosphorus (P) removal from treated municipal wastewaters, which constitute the major point source of phosphate discharge into inland lakes and rivers.

The project was designed to build on previous attempts by the project team to develop an improved alternative both to the use of chemical precipitants and to the enhanced biological phosphorus removal (EBPR) process – currently the major methods of achieving the levels of P reduction demanded by increasingly stringent European legislation. Each has significant drawbacks: the former is expensive and leads to increased levels of sludge production, while the latter can perform inconsistently in the low-strength, high-volume wastewaters characteristic of temperate latitudes.

Earlier work by the project team at laboratory and pilot-plant scale indicated that the maintenance of mildly acidic conditions (about pH 6.0) in a fully aerobic conventional activated sludge process can achieve levels of P removal comparable to those attainable under the aerobic/anaerobic cycling regime characteristic of the EBPR process (which has an optimum operationally pH of 7 to 8): this phenomenon has been termed the ‘acid-stimulated biological phosphorus removal’ (ASBPR). The major aims of the current study were to subject ASBPR to a full-scale trial under normal operational conditions (funded by the project’s industrial partners Northern Ireland Water Ltd and the QUESTOR Centre), and to gain a better understanding of the biochemical mechanisms that underpin the phenomenon so that it might be exploited more fully.

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