Prediction of biogas production rate from dry anaerobic digestion of food waste: Process-based approach vs. recurrent neural network black-box model.

The stability of dry anaerobic digestion (AD) of food waste (FW) as well as the resulting methane gas generation was investigated from the perspective of system dynamics. Various organic loading rates were applied to the system by modifying the water content in the FW feed and solid retention time (SRT). The excessive organic loading due to the accumulation of volatile fatty acids (VFAs) from the feed with 80% water content during the short SRT (15 and 20 d) caused system failure. In contrast, more intermediate materials, such as VFAs, was easily converted into methane at higher water contents. In addition, the biogas production rate of dry AD was effectively predicted based on SRT, soluble chemical oxygen demand, total VFA, total ammonia, and free ammonia using a recurrent neural network-the so-called "black-box" model. This implies the feasibility of applying this data-based black-box model for controlling and optimizing complex biological processes.

Process stability and comparative rDNA/rRNA community analyses in an anaerobic membrane bioreactor with silicon carbide ceramic membrane applications.

This study evaluated the feasibility of using a silicon carbide (SiC) anaerobic ceramic membrane bioreactor (AnCMBR) to co-manage domestic wastewater (DWW) and food waste recycling wastewater (FRW). A pilot-scale SiC-AnCMBR was put into operation for 140 days under two different organic loading rates (OLRs): 5 kg COD m-3 d-1 (OLR 5) and 3 kg COD m-3 d-1 (OLR 3). The organic removal efficiency was 93.5 ±â€¯3.7% over the operational period. Methane production increased significantly after sludge re-seeding at OLR 3. rDNA and rRNA microbial results showed that the active archaeal community was affected by sludge re-seeding, whereas the active bacterial community was not, indicating that a shift in the active archaeal community was responsible for the increased methane production. Our results thus suggest that SiC-AnCMBRs are a promising option for co-managing DWW and FRW.

Effects of changes in temperature on treatment performance and energy recovery at mainstream anaerobic ceramic membrane bioreactor for food waste recycling wastewater treatment.

An anaerobic ceramic membrane bioreactor (AnCMBR) has been attracted as an alternative technology to co-manage various organic substrates. This AnCMBR study investigated process performance and microbial community structure at decreasing temperatures to evaluate the potential of AnCMBR treatment for co-managing domestic wastewater (DWW) and food waste-recycling wastewater (FRW). As a result, the water flux (≥6.9 LMH) and organic removal efficiency (≥98.0%) were maintained above 25 °C. The trend of methane production in the AnCMBR was similar except for at 15 °C. At 15 °C, the archaeal community structure did not shifted, whereas the bacterial community structure was changed. Various major archaeal species were identified as the mesophilic methanogens which unable to grow at 15 °C. Our results suggest that the AnCMBR can be applied to co-manage DWW and FRW above 20 °C. Future improvements including psychrophilic methanogen inoculation and process optimization would make co-manage DWW and FRW at lower temperature climates.

Pilot-scale investigation of sludge reduction in aerobic digestion system with endospore-forming bacteria.

A pilot-scale investigation of membrane-based aerobic digestion system dominated by endospore-forming bacteria was evaluated as one of the potential sludge treatment processes (STP). Most of the organic matter in the sludge was removed (90.1%) by the particular bacteria in the STP, which consisted of mixed liquor suspended solid (MLSS) contact reactor (MCR), MLSS oxidation reactor (MOR), and membrane bioreactor (MBR). The sludge was accumulated in the MBR without wasting, and then the effluent in STP was fed into the first step in water resource recovery facility (WRRF). According to the analysis of microbial communities in all reactors, various Bacillus species were present in the STP, mainly due to their intrinsic resistance to the extreme conditions. As the surviving Bacillus species might consume degraded microorganisms for their growth, these endospore-forming bacteria-based STP could be suitable for the sludge reduction when they operated for a long time.

Production of algal biomass (Chlorella vulgaris) using sediment microbial fuel cells.

In this study, a novel algal biomass production method using a sediment microbial fuel cell (SMFC) system was assessed. Under the experimental conditions, CO(2) generation from the SMFC and its rate of increase were found to be dependent on the current generated from the SMFC. However, the CH(4) production rate from the SMFC was inhibited by the generation of current. When Chlorella vulgaris was inoculated into the cathode compartment of the SMFC and current was generated under 10 Ω resistance, biomass production from the anode compartment was observed to be closely associated with the rate of current generation from the SMFC. The experimental results demonstrate that 420 mg/L of algae (dry cell weight) was produced when the current from the SMFC reached 48.5 mA/m(2). Therefore, SMFC could provide a means for producing algal biomass via CO(2) generated by the oxidation of organics upon current generation.