Removing phosphate from a municipal wastewater treatment plant in the United Kingdom using a waste-to-resource model

The dispersal of phosphorus from sewage, industrial waste, detergents, and urban and agricultural runoff has played a major part in the eutrophication of many freshwater and marine ecosystems in Europe. As a consequence, phosphate discharge consents on municipal and industrial effluent are being tightened to ≤2.0 mg/L. Many agricultural activities, industrial processes and water treatment companies therefore face additional requirements to reduce soluble phosphate in discharge waters. A new green filtration technology, which repurposes alumina refinery residue, offers a passive, flow-through treatment system for phosphorus removal. The technology has been shown elsewhere to reduce or eliminate the need for chemical dosing, allow for variations in hydraulic flow and nutrient loading, minimise sludge production, and provide an effective and straightforward treatment system when applied immediately prior to final effluent discharge. A four-month trial to evaluate the potential use of this waste-to-resource technology to enhance the removal of phosphate from municipal wastewater in line with these tighter standards was conducted in the United Kingdom. The primary objective was to determine if the technology could reliably maintain phosphate concentrations to extremely low consent limits. The trial was conducted at Yorkshire Water’s Kirk Smeaton wastewater treatment plant in North Yorkshire, and comprised three separate filter configurations in order to provide comparison data on different design scenarios, hydraulic residence times, removal efficiencies and projected filter life-spans. Filter Pairing A consisted of two columns operating in series with a hydraulic residence time of 12 hours. Influent phosphate concentrations averaged 10.3 mg/L for the duration of the trial and effluent concentrations averaged 2.6 mg/L, a removal efficiency across both columns of 74%. In addition, biological oxygen demand was reduced from 6.8 mg/L to 4.3 mg/L, and ammonia-nitrogen was reduced from 1.1 mg/L to 0.86 mg/L. Filter Pairing B again consisted of a two-stage filter system operating in series but with a shorter hydraulic residence time of two to three hours. Influent phosphate concentrations averaged 9.6 mg/L and effluent concentrations averaged 1.8 mg/L, a removal efficiency across both columns of 81%. Filter Pairing C, consisted of a three-stage filter system operated in series with a hydraulic residence time of 12 hours, but in contrast with Filter Pairing a each filter operated with a hydraulic residence time of four hours. Influent phosphate concentrations averaged 9.6 mg/L and effluent concentrations averaged 0.37 mg/L, a phosphate removal efficiency across both columns of 96%. Results of this study indicate that Filter Pairings B and C achieved phosphate removal efficiencies which conform to the tighter regimes being imposed throughout the UK and Europe