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Research on the Union Process of Autothermal Thermophilic Aerobic and Anaerobic Digestion under Different Sludge Solid Contents

In order to understand the influence of the methane production in the union process of autothermal thermophilic aerobic and anaerobic digestion(TAD-MAD) systems, p H, total alkalinity, VSS removal rate, VFA content, methane production, and CH_4 content were studied under different sludge solid contents in TAD-MAD and mesophilic anaerobic digestion(MAD) process, respectively. The results showed that p H in TAD-MAD system was maintained at 6.5~7.8 which is a suitable condition for growth of methanogenic bacteria without regulating p H of feed sludge. It was propitious to the subsequent MAD that the TAD optimal sludge retention time was 2 days with the substantial increase of VFA content for8 524.70 mg/L. TAD-MAD obtained more superiority than MAD in the total methane production per unit VSS and CH_4 content. When the optimum sludge TSS condition of TAD-MAD was 7.12%, the VSS removal rate reached above 40% after a24-days digestion. By contrast, the VSS removal rate of MAD was 35.12% only. TAD-MAD total methane production per unit VSS was 116.56 m L/g VSS, more than the MAD 85.72 m L/g VSS. In addition, TAD-MAD had not only much longer duration of methane production but also higher CH_4 content than MAD. In conclusion, TAD-MAD had more advantage than MAD on VSS removal rate, methane production and CH_4 content.