Ammonia air stripping from pig slurry: influence of previous mesophilic anaerobic digestion process

The solution to environmental problems associated with livestock wastes requires a broad integrated approach. The recovery of valuable products as nitrogen, has become a need in geographical areas with high animal farming density. Ammonia air stripping, combined with absorption, can remove and recover ammonia from liquid wastes. The objective of the present paper is to study the pH effect on ammonia air stripping from pig slurry and its performance when fresh and anaerobic digested slurry is used. Depending on the pig slurry type, treatment performances are different. In any case, ammonia removal rates are pH dependent, the higher the pH, the higher the removal rates are. When fresh pig slurry is used, a high initial pH is required (large addition of alkali is needed). For digested pig slurry, pH adjustment is still necessary but not critical for achieving high removal efficiencies. Whit digested slurry, a complete ammonia removal without pH modification was possible, at 80oC.