曝气在沉淀法回收沼气发酵液氮磷中的作用

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

以畜禽养殖废水经厌氧消化处理后的沼气发酵液为研究对象,采用曝气吹脱的处理方式。研究了进水方式,曝气强度,水力停留时间(HRT)对发酵液pH值提升效果的影响。并考察了曝气过程中PO43--P、NH4+-N、Mg2+、Ca2+、化学需氧量(COD)的变化规律。结果表明:发酵液pH值在曝气2h内提升明显,可迅速从7.27达到8.5,之后则变化较缓慢,12h后可基本达到最高值9.3,为沉淀法回收氮磷提供了有利的pH值条件。间歇式进水pH值提升效果优于连续式进水,增大曝气强度和HRT可加快pH值提升速度,HRT越大pH值提升幅度越大。曝气过程中发酵液的PO43--P、NH4+-N、Mg2+、Ca2+、COD均呈规律性下降趋势,磷回收率可达65%左右,氮回收率为20%～40%,同时发酵液COD可下降20%～30%。曝气方式亦可以起到搅拌的作用。试验证实了采用化学沉淀法对厌氧发酵液进行氮磷回收时采用曝气处理可提升pH值。

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 PO4 3-P,NH4 ＋-N, Mg 2＋ ,Ca 2＋ ,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 PO4 3-P,NH4 ＋-N,Mg 2＋,Ca 2＋,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%.