Removal of ammonia from anaerobic co-digestion effluent of organic fraction of food waste and domestic wastewater using air stripping process

For many years, anaerobic digestion has been widely applied to the treatment of wastewater with high biodegradable organic content like waste sludge, an organic fraction of solid waste, as well as to mixtures of wastewater and solid waste [1]. The anaerobic digestion process possesses advantages such as low sludge production, low energy consumption, and high potential recovery of biogases, which can be used for cooking and electricity. However, anaerobic effluent has a high ammonia concentration [1]. Further, ammonium is discharged into receiving bodies from various sources, namely fertilizer [2], landfill leachate [3], pig wastewater [4, 5], and especially in the effluent of an anaerobic co-digestion of a mixture of two or more solid wastes and wastewaters [6]. When discharged into receiving sources, ammonium causes eutrophication, dissolved oxygen depletion, and toxicity to aquatic organisms [7]. Additionally, the penetration of ammonia into ground water causes water contamination and is the cause of blue-skinned disease in children and pregnant women [7]. Because of the risks of untreated ammonia discharge, environmental regulations regarding the allowable limits of ammonia into receiving bodies are becoming more stringent across every country. In Vietnam, the maximum allowable limit of ammonium in drinking water is 3.0 mg/l [8].