title: Improving nutrient fixation and dry matter content of an ammonium-rich anaerobic digestion effluent by struvite formation and clay adsorption.
abstract: The anaerobic digestion (AD) of organic wastes that contain nitrogen leads to its mineralization, yielding a digestate rich in ammonium (NH(4)(+)), an important fertilizing nutrient. The applicability of AD digestate as fertilizer can be improved by fixating the nutrients and increasing its dry matter content. Methods for the fixation and recovery of the digestate's NH(4)(+) and possible also PO(4)(3-) include struvite precipitation and adsorption in clay materials such as bentonite. These techniques were tested in batch experiments employing the liquid fraction of a digestate originating from the AD of a substrate mix containing lignocellulose, cattle manure and fish industrial waste. The concentration of NH(4)(+)-N in this digestate was 2,300 mg L⁻¹. Struvite precipitation conditions at a molar ratio of 1.2:1:1 (Mg²⁺:NH(4)(+):PO(4)(3-)) and pH 9.5 were best in terms of simultaneous removal of NH(4)(+)-N (88%), PO(4)(3-) (60%) and soluble chemical oxygen demand (44%). Bentonite adsorption gave comparably high removal levels for NH(4)(+)-N (82%) and PO(4)(3-) (52%). Analysis of the precipitates' morphology and elemental composition confirmed their struvite and bentonite nature. Dry matter content was increased from 5.8% in the AD digestate to 27% and 22% in the struvite and bentonite sludges, respectively.
authors: Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway E-mail: maria.magdalena.estevez@nmbu.no; Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Frederik A. Dahls vei 20, 1432 Ås, Norway.
authors: Maria M
authors: MM
authors: Estevez
authors: Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Frederik A. Dahls vei 20, 1432 Ås, Norway.
authors: Roar
authors: R
authors: Linjordet
authors: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P. O. Box 5003, 1432 Ås, Norway.
authors: Svein J
authors: SJ
authors: Horn
authors: Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway E-mail: maria.magdalena.estevez@nmbu.no.
authors: John
authors: J
authors: Morken
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D064751:Ammonium Compounds / Q000737:chemistry*; D000818:Animals; D001546:Bentonite; D019149:Bioreactors; D002417:Cattle; D011232:Chemical Precipitation; D000077215:Clay; D005399:Fishes; D007220:Industrial Waste; D017616:Magnesium Compounds / Q000737:chemistry*; D008372:Manure; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D000069877:Struvite; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D064751:Ammonium Compounds; D001546:Bentonite; D000077215:Clay; D007220:Industrial Waste; D017616:Magnesium Compounds; D008372:Manure; D010710:Phosphates; D010758:Phosphorus; D000069877:Struvite; D062065:Wastewater