Effect of aeration on crystallization technology for nitrogen and phosphorus recovery from biogas fermentative liquid

Taking the biogas fermentative liquid treated by anaerobic digestion process from livestock wastewater as the research object, the effects of influent modes, aeration intensities, and hydraulic retention time (HRT) on lifting pH values were investigated by using the treatment method of aeration stripping. The variation laws of PO43--P, NH4+-N, Mg2+, Ca2+, and COD in aerating were studied too. The results showed that the effects of lifting pH values were obvious, the pH values of the biogas fermentative liquid were lifted from 7.27 to 8.5 in 2 hours after aerated. Then the pH value changed slowly and reached its maximum 9.3 at 12 hours. That created favorable condition of pH value for nitrogen and phosphorus recovery with crystallization technology. The effect of batch-influent was better than that of continuous-influent. The lifting speed accelerated when aeration intensity and HRT increased. The bigger the HRT was, the larger the lifting range was. The PO43--P, NH4+-N, Mg2+, Ca2+, and COD have been a regular downtrend in aerating. Recovery rate of phosphorus was almost 65%, while that of nitrogen was 20%-40%, and COD decreased by 20%-30%.