Anaerobic dynamic membrane bioreactor for the co-digestion of toilet blackwater and kitchen waste.

Anaerobic co-digestion using an anaerobic dynamic membrane bioreactor (AnDMBR) can separate the sludge retention time and hydraulic retention time, retaining the biomass for efficient degradation and the use of less expensive large pore-size membrane materials and more sustainable dynamic membranes (DMs). Therefore, anaerobic co-digestion of toilet blackwater (BW) and kitchen waste (KW) using an AnDMBR was hypothesized to increase the potential for co-digestion. Here, the efficiency and stability of AnDMBR in anaerobic co-digestion of toilet BW and KW were investigated. DM morphology and structural characteristics, filtration properties, and composition, as well as membrane contamination and membrane regeneration mechanisms, were investigated. Average daily biogas yields of the reactor in two membrane cycles before and after cleaning were 788.67 and 746.09 ml/g volatile solids, with average methane content of 66.64% and 67.27% and average COD removal efficiencies of 82.03% and 80.96%, respectively. The results showed that the bioreactor obtained good performance and stability. During the stabilization phase of the DM operation, the flux was maintained between 43.65 and 65.15 L/m2/h. DM was mainly composed of organic and inorganic elements. Off-line cleaning facilitated DM regulation and regeneration, restoring new Anaerobic morphology and structure. PRACTITIONER POINTS: High efficiency co-digestion of BW and KW was realized in the DMBR system. Average daily biogas yields before and after membrane cleaning were 788.67 and 746.09 ml/g volatile solids. Off-line cleaning facilitated DM regulation and regeneration as well as system stability. The flux was maintained between 43.65 and 65.15 L/m2/h during operation.

Bacterial dynamics and functions driven by biomass wastes to promote rural toilet blackwater absorption and recycling in an ectopic fermentation system.

Due to high concentration of organic matter and the ease of disease transmission, blackwater pose a serious threat to both the environment and human health, especially in rural areas where wastewater treatment is dispersed. The reuse of biomass waste is also a difficult issue to be addressed urgently. In this study, an ectopic fermentation system (EFS) was used to treat toilet blackwater, and the effects of different biomass waste combinations on bacterial communities and functions during aerobic fermentation of blackwater were compared. The results showed that adding bran powder prolonged the high temperature period of 11 d, improved blackwater absorption capacity by 7.5% and was beneficial to microbial metabolic activities to enhance organic degradation. By contrast, the combination of corn straw and rice husk obtained abundant bacterial OTUs and diversity. Bacillus, Thermobifida and Thermopolyspora were the main microorganisms involved in the degradation of organic matter in EFS, and their abundance varied in different filler combinations. Bacterial communities were directly affected by environmental factors such as temperature, NH4+-N and organic carbon as well as biomass materials during fermentation. This study revealed the role of corn straw, rice husk and bran powder in EFSs, provided new technical support for blackwater treatment and a new direction for the resource utilization of agricultural biomass waste.

Pushing the organic loading rate in electrochemically assisted anaerobic digestion of blackwater at ambient temperature: Insights into microbial community dynamics.

Decentralized blackwater treatment by anaerobic digestion is being considered as a sustainable sanitation concept. However, the low biodegradability and complex composition restrictedly limited the treatability of blackwater, resulting in requirements of low operational organic loading rates (OLRs). In this study, a microbial electrolysis cell assisted anaerobic digester (MEC-AD) treating vacuum toilet blackwater was successfully operated for 420 days at OLRs ranging from 0.77 to 3.03 g COD/L-d in 6 stages (including an open-circuit Stage 5) at ambient temperature. Based on the steady-state results from different stages, the highest methane yield (42.4% out of 45% biochemical methane potential value) was achieved in Stage 1 with an OLR of 0.77 g COD/L-d. At the same OLR of ~3.0 g COD/L-d, Stage 4 (32.4%) and Stage 6 (35.2%) showed significantly higher methane yield (p < 0.01) than open-circuit Stage 5 (24.1%). The lowest COD removal efficiency of 31.8% was observed in Stage 5 with short-chain volatile fatty acids (SCVFAs) accumulated to ~1000 mg/L, which was more than double the values of Stage 4 and 6. The microbial community analysis revealed that the applied potential did not significantly affect archaeal diversity but largely increased the archaeal abundance on the cathode, and led the bacterial community shift with the enrichment of specific electroactive bacteria. Microbial co-occurrence network analysis further confirmed the positive correlations between known electroactive bacteria and electrotrophic methanogens. Moreover, electric energy consumed by the MEC-AD system was fully recovered as biomethane.