초록
<P><B>Abstract</B></P> <P>This study used a batch experiment and a long-term experiment to investigate the effects of FeCl<SUB>3</SUB> and FeCl<SUB>2</SUB> on the high-solids anaerobic digestion (HSAD) of sludge for improving the methane productions. The results of batch experiment with an organic loading rate of 6.93 gVS/L suggested that the cumulative methane productions were enhanced by 28.9% and 6.4% with 200 mg/L FeCl<SUB>3</SUB> and 250 mg/L FeCl<SUB>2</SUB> in HSAD system, respectively. The higher methane productions were also obtained by 200 mg/L FeCl<SUB>3</SUB> and 250 mg/L FeCl<SUB>2</SUB> in the long-term experiment for 114d. An excessive FeCl<SUB>3</SUB> could inhibit the HSAD process, which would be gradually recovered by the ammonia and the microbes acclimated to this environment. The organics degradation results indicated that the addition of 200 mg/L FeCl<SUB>3</SUB> or 250 mg/L FeCl<SUB>2</SUB> could show a positive effect on the substrate environment of a stable total volatile fatty acids (TVFA) concentration and pH, and promote the protease and dehydrogenase activities in HSAD system. In addition, the SRT played a significant role in the HSAD process by balancing hydrolysis-acidification and methanogenesis. An appropriate dosage of FeCl<SUB>3</SUB> and FeCl<SUB>2</SUB> improved the methane productions, and blocked the accumulation of TVFA caused by shortening SRT.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We comparatively studied the effects of FeCl<SUB>3</SUB> and FeCl<SUB>2</SUB> in sludge HSAD system. </LI> <LI> The best concentrations of FeCl<SUB>3</SUB> and FeCl<SUB>2</SUB> were 200 mg/L and 250 mg/L. </LI> <LI> FeCl<SUB>3</SUB> and FeCl<SUB>2</SUB> created positive environment and promoted enzymatic activities. </LI> <LI> Excessive FeCl<SUB>3</SUB> exhibited a more serious inhibition effect than excessive FeCl<SUB>2</SUB>. </LI> <LI> SRT played a significant role in sludge HSAD system. </LI> </UL> </P>