Phosphorus retention capacity of iron-ore and blast furnace slag in subsurface flow constructed wetlands.
The suitability of iron-ore and blast furnace slag for subsurface flow (SSF) constructed wetlands was studied over a period of four months. Dairy farm wastewater (TP 45 mg l(-1)) was percolated through buckets planted with reed (volume 9.1 l; hydraulic load 151 m(-2) d(-1)). One group of buckets was kept under aerobic conditions and the other group under anaerobic conditions, monitored by continuous redox potential measurements. Even at high mass loading rates of 0.65 g P m(-1) d(-1) the slag provided 98% removal efficiency and showed no decrease in performance with time. However, phosphorus fractionation data indicate that the high phosphorus retention capacity under aerobic conditions is to a great extent attributable to unstable sorption onto calcium compounds (NH4Cl-P). Phosphorus sorption of both the slag (200 microg P g(-1)) and the iron-ore (140 microg P g(-1)) was promoted by predominantly anaerobic conditions due to continuous formation of amorphous ferrous hydroxides. None of the substrates had adverse affects on reed growth.
Grüneberg
B
B
Institute of Agricultural Engineering, Bornim, Potsdam, Germany.
Kern
J
J
D000327:Adsorption; D000383:Agriculture; D000818:Animals; D001421:Bacteria, Anaerobic; D002417:Cattle; D017753:Ecosystem; D007501:Iron / Q000737:chemistry*; D008906:Mining; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements
D010758:Phosphorus; D007501:Iron