Technico-economic feasibility of P-recovery from municipal wastewaters

The feasibility of recovering phosphates from municipal wastewater is assessed from literature, targeted interviews of water industry experts and process modeling. It is concluded that it is technically feasible to recover up to 75% of wastewater treatment plant (WwTP) inflow P, but today this is only attractive in WwTPs operating biological nutrient removal. The recovered P-product is likely to be of a better quality than currently available phosphate rock. P-recovery should reduce total wastewater biosolids production by 2-8% dry matter but where biosolids are incinerated ash production should reduce by 12-48%. It will considerably facilitate co-combustion in cement works. The impact of P- recovery on wastewater biosolids management, and in particular the reductions in transport distances where biosolids are used on agricultural land (resulting from lowered P:N ratios) are costed. Savings could be around UK 100 pounds per tonne of P recovered (roughly half of UK dockside prices of imported phosphate rock), giving a total saving of UK 450,000 pounds/year for the UK if 20% of all sewage P were recovered. The size of the savings is related to the capacity of the WwTP and to the % land surface around the WwTP that is available for agricultural spreading. Economic feasibility will depend on the local context, for example possible advantages for WwTP operation (nuisance deposit avoidance, removal of return streams of P to WwTP head), advantages for biosolids management or national decisions to fix P-recycling as environmental objectives.