title: Phosphorus species and fractionation--why sewage derived phosphorus is a problem.
abstract: Phosphorus (P) inputs to sewage treatment works (STW) come from a variety of sources and filtration of treated wastewater prior to discharge into receiving waters is a common practice. This means P in treated wastewaters may be present in forms that are potentially more bioavailable and mobile. We conducted a 2-year study to determine P species up and downstream of two STW outfalls into two tributaries of the River Thames. Downstream of the outfalls, P concentrations in both rivers were frequently greater by an order of magnitude for all species of P. A high proportion of total P (TP) in the downstream waters was determined as dissolved, which was largely comprised of soluble reactive P (SRP) - considered as the most bioavailable P species. Furthermore no significant difference in SRP was found in receiving waters passed through 0.45 and 0.10 μm filters. This means that P from STWs occurs in <0.1 μm fraction size, which will not readily settle to the channel bed and is more easily assimilated by biota. This distinguishes STW inputs from agricultural runoff where a high proportion of P occurs as particulate P which is both less bioavailable and more likely to settle to the channel bed. This implies that STWs derived P is likely to have a greater adverse impact on the receiving river than agricultural runoff.
authors.affiliation: Centre for Earth and Environmental Science Research, Kingston University London, Kingston upon Thames KT1 2EE, UK. h.millier@westminster.ac.uk
authors.forename: Helen K G R
authors.initials: HK
authors.lastname: Millier
authors.forename: Peter S
authors.initials: PS
authors.lastname: Hooda
mesh_terms: D004739:England; D010758:Phosphorus / Q000032:analysis*; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000032:analysis*
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D010758:Phosphorus