Ammonium removal from digested effluent of swine wastewater by using solid residue from magnesium-hydroxide flue gas desulfurization process

Abstract

This paper focused on the ammonium removal from the digested effluent of swine wastewater (DESW) via MAP precipitation using the residue from magnesium-hydroxide flue gas desulfurization (MFGD) process as a Mg source. The MAP precipitation was proceeded in a 500-mL beaker with a magnetic stirrer. It was found that around 60% of ammonium in the DESW was removed at pH 9.5, HRT 10min and the P:Mg:N molar ratio of 0.6:0.7:1. The NH4+ concentration (183.2mg/L) in the DESW after MAP precipitation was lower than 200mgL−1, being alternative for the downstream biological process. A low content of PO43− (3.64mgL−1) and a high concentration of Mg2+ (67.17mgL−1) were also observed in the solution. The main composition of the precipitate was proved to be MAP via XRD and SEM-EDX analysis. Besides, the total chemical cost was saved by 29.17% using the MFGD residue as a Mg source instead of the commercial MgCl2·6H2O. Hence, reusing MFGD residue as a Mg source to remove ammonium from the DESW was feasible with cost saving, resource recovery and environment protection.