title: Phosphorus removal using Ca-rich hydrated oil shale ash as filter material--the effect of different phosphorus loadings and wastewater compositions.
abstract: We studied the phosphorus (P) binding capacity of Ca-rich alkaline filter material - hydrated oil shale ash (i.e. hydrated ash) in two onsite pilot-scale experiments (with subsurface flow filters) in Estonia: one using pre-treated municipal wastewater with total phosphorus (TP) concentration of 0.13-17.0 mg L(-1) over a period of 6 months, another using pre-treated landfill leachate (median TP 3.4 mg L(-1)) for a total of 12 months. The results show efficient P removal (median removal of phosphates 99%) in horizontal flow (HF) filters at both sites regardless of variable concentrations of several inhibitors. The P removal efficiency of the hydrated ash increases with increasing P loading, suggesting direct precipitation of Ca-phosphate phases rather than an adsorption mechanism. Changes in the composition of the hydrated ash suggest a significant increase in P concentration in all filters (e.g. from 489.5 mg kg(-1) in initial ash to 664.9 mg kg(-1) in the HF filter after one year in operation), whereas almost all TP was removed from the inflow leachate (R(2) = 0.99). Efficiency was high throughout the experiments (median outflow from HF hydrated ash filters 0.05-0.50 mg L(-1)), and P accumulation did not show any signs of saturation.
authors.affiliation: Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise St., Tartu 51014, Estonia. margit.koiv@ut.ee
authors.forename: Margit
authors.initials: M
authors.lastname: Kõiv
authors.forename: Martin
authors.initials: M
authors.lastname: Liira
authors.forename: Ulo
authors.initials: U
authors.lastname: Mander
authors.forename: Riho
authors.initials: R
authors.lastname: Mõtlep
authors.forename: Christina
authors.initials: C
authors.lastname: Vohla
authors.forename: Kalle
authors.initials: K
authors.lastname: Kirsimäe
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002947:Cities; D004957:Estonia; D005374:Filtration / Q000295:instrumentation*; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009821:Oils / Q000737:chemistry*; D010758:Phosphorus / Q000302:isolation & purification*; D013696:Temperature; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000302:isolation & purification
chemical_list: D009821:Oils; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D002118:Calcium