Phosphorous (P) permits are tightening, with >750 new or tightened permits expected to be enforced during AMP7 and >450 of these permits below 0.9 mg/l. Traditionally these permits are met by dosing iron and aluminium salts, for conversion of the soluble ortho-P fractions into solid, settleable P. Use of ferric sulphate is already 466,000 t/a, and is expected to increase significantly during AMP7. Security of the supply chain is on the business risk register for most Water Companies. Further, chemical phosphorous removal reduces the potential for recovery of P, which is essential for a circular economy and true sustainability.
Bio-P offers a more sustainable and cheaper solution to P removal, but there are a limited number of bio-P plants operating, largely due to concern over the resilience and durability of such plants. This paper will discuss the conventional wisdom around bio-P removal, the drivers for its implementation and reasons for lack of uptake in the UK.
Operational trials with a plant exhibiting good, but variable P removal will explore how more consistent performance can be achieved and that performance less than 1 mg/l P without chemical addition can be more than just a pipe dream.