A new filter material for phosphorus removal and recycling in small-scale wastewater treatment

Abstract Santacroce, A., 2002. A new filter material for phosphorus removal and recycling in small-scale wastewater treatment. TRITA-LWR Master Thesis: 02-x. KTH, Stockholm. The use of phosphorus (P)-sorbing materials as substrates in both constructed wetlands and filter systems after a preliminary treatment is promising for P removal in small-scale plants disposing wastewater. The P-saturated materials may be used as fertiliser in agriculture, provided the adsorbed P is available to the crop. The newly available commercial product Polonite ® (2-5.6 mm), derived from the bedrock Opoka, was tested in this study in relation to its P-sorption capacity. Short-term batch experiments and two different long-term column experiments were performed. A small-columns (n=3, d=3.4 cm, h=19 cm) laboratory experiment was carried out under conditions of continuous phosphate loading ( 3 l/d per column) through collected wastewater (3-5 mg/l PO 4 2- ) for 49 days. Samples were taken daily from the influent and effluent water and phosphate concentrations were measured by means of Aquatech Autoanalyser. Results showed an almost complete P- retention in the first 10 days, a fluctuating but consistently above 90% removal during the second 10 days and then an increasing loss of the material efficiency in P-sorption. At the Loudden wastewater treatment plant in Stockholm a column (d=35 cm, h=60 cm) experiment was run for 8 weeks under conditions of intermittent wastewater loading (5 l/h, 18 h/d). Samples were collected once per week and a total PO 4 2- sorption was found, with the exception of the last week when, although slowly, P content in the outflow started increasing. The possibilities for recycling or recovering the phosphorus resource are discussed. # Keywords: sorption, Opoka, Polonite ® , batch experiments, column experiments ii