Assessment of quality of post-fermentation effluents from municipal and agricultural biogas plants in the aspect of the possibility of recovering biogenic compounds

摘要

The post-fermentation effluents contained 0.06-0.54 g/L and 0.92-2.11 g/L of PO43- and NH4+ ions, resp. The highest concns. of those ions were found in the effluents from the fermentation of animal waste and the lowest from the fermentation of agricultural waste. High efficiency of struvite pptn. was obtained at 21 degrees C, pH 9, stirring intensity 240 rpm for 120 min and molar ratios of Mg:P = 1.2:1 and Mg:Ca < 1. Regardless of the type of external Mg source used (MgO, MgCl2 and MgSO4), high recovery of PO43 ions (71.0-98.0%), and NH4+ ions (14.0-24.0%) were found.