Evaluation of Local and National Effects of Recovering Phosphorus at 1 Wastewater Treatment Plants: Lessons Learned from the UK

10 P recovery from wastewater treatment plants (WWTPs) as struvite fertiliser is a recognised method of 11 improving P use efficiency and reducing P losses into the environment. The main driver for P recovery from the 12 water industry viewpoint is the reduction in the nuisance of struvite clogging inside pumps and pipes. Struvite 13 recovery leads to an average P recovery rate of 72±7% from centrifuge centrate, with 8.8±0.7% total P and 14 20.5±3.2% PO4-P removed from the WWTP influent as struvite. This reduces the potential for struvite 15 precipitation, moderates P loads on biological nutrient removal processes and lowers P concentration in the 16 final effluent. Totalling revenue from sale of struvite and operational site savings, P recovery becomes an 17 attractive option for water companies. The implementation of P recovery technologies to produce struvite 18 fertiliser in all UK WWTPs could produce a national P fertiliser source of 7.05±2.01 kt P/year. In addition, 19 sludge produced at WWTPs could be diverted to advanced energy recovery (AER) processes and P recovered 20 from AER residues; up to 21.71±0.95 kt P/year could be recovered in this way in the UK. Combining the two 21 methods of P recovery, UK imports of P fertiliser could be reduced by 36.2±1.1%. P recovery on a large scale 22 has the further benefit of protecting against eutrophication by reducing P emissions to water bodies by 23 21.7±1.9%. The protection of the environment and reduction in reliance on imported P are major national 24 motivations to legislate P recovery from waste. 25