The alternating aerobic-anoxic (AAA) process offers many advantages for wastewater treatment and sludge digestion. Laboratory scale experiments were conducted to investigate the feasibility of using pH as a realtime control parameter for this process. Several well defined control points on the pH curve were identified, e.g., ammonia valley and nitrate apex. These points were directly related to the alternating nitrification and denitrification reactions in the process, and were found to be consistent with those previously identified using ORP. Although both pH and ORP can be used as real-time control parameters, pH provides several additional advantages over ORP. Based on these findings, real-time control strategies (fixed pH setpoints and dynamic pH control) were developed and tested. Results from laboratory scale AAA sludge digestion using fixed pH setpoints (6-8) indicated that 36% MLVSS reduction, 39% TN reduction and almost 48% saving in aeration energy was achieved after 300 hrs of digestion.

No abstract

No abstract

No abstract

BackgroundThe microbial fuel cell represents a novel technology to simultaneously generate electric power and treat wastewater. Both pure organic matter and real wastewater can be used as fuel to generate electric power and the substrate type can influence the microbial community structure. In the present study, rice straw, an important feedstock source in the world, was used as fuel after pretreatment with diluted acid method for a microbial fuel cell to obtain electric power. Moreover, the microbial community structures of anodic and cathodic biofilm and planktonic culturewere analyzed and compared to reveal the effect of niche on microbial community structure.ResultsThe microbial fuel cell produced a maximum power density of 137.6 ± 15.5 mW/m2 at a COD concentration of 400 mg/L, which was further increased to 293.33 ± 7.89 mW/m2 through adjusting the electrolyte conductivity from 5.6 mS/cm to 17 mS/cm. Microbial community analysis showed reduction of the microbial diversities of the anodic biofilm and planktonic culture, whereas diversity of the cathodic biofilm was increased. Planktonic microbial communities were clustered closer to the anodic microbial communities compared to the cathodic biofilm. The differentiation in microbial community structure of the samples was caused by minor portion of the genus. The three samples shared the same predominant phylum of Proteobacteria. The abundance of exoelectrogenic genus was increased with Desulfobulbus as the shared most abundant genus; while the most abundant exoelectrogenic genus of Clostridium in the inoculum was reduced. Sulfate reducing bacteria accounted for large relative abundance in all the samples, whereas the relative abundance varied in different samples.ConclusionThe results demonstrated that rice straw hydrolysate can be used as fuel for microbial fuel cells; microbial community structure differentiated depending on niches after microbial fuel cell operation; exoelectrogens were enriched; sulfate from rice straw hydrolysate might be responsible for the large relative abundance of sulfate reducing bacteria.