Long-term phosphate removal by the calcium-silicate material Polonite in wastewater filtration systems.
The mineral-based filter material Polonite was tested for its PO4 removal capacity in column and full-scale systems using synthetic and domestic wastewater. Three long-term experiments (67, 68 and 92 wk), operated under different hydrological conditions, were compared. The best PO4 removal capacity (97%) was observed in an intermittent saturated column fed with a synthetic solution (530 L m(-2) d(-1)) without organic matter during 68 wk. An unsaturated column system using municipal wastewater (76.7 L m(-2) (-1)) showed no tendency for PO4 breakthrough and effluent PO(4) concentration was still low (0.2 mg L(-1)) after 67 wk. For a compact bed filter containing 560 kg of Polonite and fed with 70 m(3) of wastewater from a single house, the average PO4 removal was 89% after 92 wk of operation. The column experiments revealed that a design volume of 1-2 kg of material of a particle size of 2-5mm was required amount for treating 1m(3) of wastewater in on-site systems operating at target 90% P mass removal. Poor pre-treatment of the wastewater was suggested to reduce the phosphate removal capacity of Polonite in the bed filter trial, where 8 kg were required per m(3). To measure pH of the treated effluent water proved not to be a simple tool for determining when the filter material is exhausted and should be replaced.
Renman
Agnieszka
A
Department of Land and Water Resources Engineering, Royal Institute of Technology, SE-10044 Stockholm, Sweden. agak@kth.se
Renman
Gunno
G
D017610:Calcium Compounds / Q000737:chemistry*; D005374:Filtration / Q000379:methods*; D010710:Phosphates / Q000302:isolation & purification*; D017640:Silicates / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D017610:Calcium Compounds; D010710:Phosphates; D017640:Silicates; C031293:calcium silicate