In-depth observations of fermentative hydrogen production from liquid swine manure using an anaerobic sequencing batch reactor

In this study,experiments were designed to reveal in-depth information of the effect of pH and hydraulic retention time(HRT)on biohydrogen fermentation from liquid swine manure supplemented with glucose using an Anaerobic Sequencing Batch Reactor(ASBR)System.Five values of HRT(8,12,16,20,and 24 h)were first tested and the best HRT determined was further studied at five p H levels(4.4,4.7,5.0,5.3,and 5.6).The results showed that for HRT 24 h,there was a dividing Hcontent(around 37%)related to the total biogas production rate for the ASBR System running at p H 5.0.When the Hcontent went beyond 37%,an appreciable decline in biogas production rate was observed,implying that there might exist an Hcontent limit in the biogas.For other HRTs(8 through 20 h),an average Hcontent of 42%could be achieved.In the second experiment(HRT 12 h),the highest Hcontent(35%)in the biogas was found to be associated with p H 5.0.The upswing of p H from 5.0 to 5.6 had a significantly more impact on biogas Hcontent than the downswing of p H from5.0 to 4.3.The results also indicated good linear relationships of biogas and Hproduction rates with HRT(r=0.9971 and0.9967,respectively).Since the optimal ASBR operating conditions were different for the biogas/Hproduction rates and the Hyield,a compromised combination of the running parameters was determined to be HRT 12 h and pH 5.0 in order to achieve good biogas/Hproductions.