Enhanced biomethane production with a low carbon footprint via anaerobic co-digestion of swine wastewater with rice husk.

An electricity-assisted anaerobic co-digestion (EAAD) process was developed and compared with conventional anaerobic co-digestion (AD) using piggery wastewater and rice husk as feedstocks. Various methodologies, including kinetic models, microbial community analyses, life-cycle carbon footprints, and preliminary economic analysis, were integrated to comprehensively evaluate the performance of the two processes. The results demonstrated that EAAD exhibited a positive improvement of 2.6 % to 14.5 % in biogas production compared to AD. The suitable wastewater-to-husk ratio for EAAD was found to be 3:1, which corresponded to a carbon-to­nitrogen ratio of approximately 14. This ratio demonstrated positive co-digestion effects and electrical enhancements in the process. According to the modified Gompertz kinetics, the biogas production rate in EAAD ranged from 1.87 to 5.23 mL/g-VS/d, significantly higher than the range of 1.19 to 3.74 mL/g-VS/d observed in AD. The study also investigated the contributions of acetoclastic and hydrogenotrophic methanogens to biomethane formation, revealing that acetoclastic methanogens accounted for 56.6 % ± 0.6 % of the methane production, while hydrogenotrophic methanogens contributed to 43.4 % ± 0.6 %. No significant difference in the methanogenic reaction pathways was observed between AD and EAAD, indicating that the introduction of an external electric field did not alter the predominant pathways (p > 0.05, two-sample t-test). Furthermore, retrofitting existing AD plants with EAAD units can reduce the carbon intensity of piggery wastewater treatment by 17.6 % to 21.7 %. The preliminary economic analysis indicated a benefit-cost ratio of 1.33 for EAAD, confirming the feasibility of implementing EAAD for wastewater treatment while simultaneously producing bioenergy. Overall, this study provides valuable insights into upgrading the performance of existing AD plants by introducing an external electric field. It demonstrates that EAAD can achieve higher and cost-effective biogas production with a lower life-cycle carbon footprint, thus enhancing the sustainability and efficiency of the biogas production process.

Recovery of iodide as triiodide from thin-film transistor liquid crystal display wastewater by forward osmosis.

Triiodide, a larger charged molecule compared to iodide, is thermodynamically favored with the presence of both iodide and iodine, and is easier to be retained by membrane processes. For the first time, iodide was recovered in the form of triiodide by forward osmosis (FO) for thin-film transistor liquid crystal display industries by preoxidation of iodide to triiodide. Partial oxidation by NaOCl was used to convert the iodide to iodine and then to form triiodide. Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), a commonly used chelating agent in the industry, was used as the draw solute because of its low reverse salt flux. The results revealed that the ideal efficiency of iodide recovery was at pH 3 with a preoxidation (adding 0.0150 M NaClO) for the 0.048 M iodide wastewater with a recovery of 98.5%. Additionally, the Pourbaix diagram and starch indicator were used to verify the formation of triiodide. Membrane distillation was demonstrated to recover the EDTA-2Na draw solute, and more than 99% of recoveries for the draw solutes with initial water flux of 12.0 L/m2 h were achieved, indicating that simultaneous recovery of the EDTA-2Na draw solute and water is feasible.

A novel thermophilic anaerobic granular sludge membrane distillation bioreactor for wastewater reclamation.

Membrane distillation (MD) has a high heat requirement. Integrating MD with thermophilic bioreactors could remedy this problem. A laboratory-scale thermophilic anaerobic granular sludge membrane distillation bioreactor (ThAGS-MDBR) was used to treat wastewater with a high organic loading rate (OLR). Waste heat from ThAGS was used directly for the MD process to reduce energy consumption. The result demonstrated that the ThAGS-MDBR system achieved a high-efficiency removal of chemical oxygen demand (more 99.5%) and NH4+-N (96.4%). Furthermore, the highest methane production from the proposed system was 332 mL/g CODremoved at OLR of 16 kg COD/m3/day. Specifically, an aggregate of densely packed diverse microbial communities in anaerobic granular sludge was the main mechanism for the enhancement of bioreactor tolerance with environmental changes. High-quality distillate water from ThAGS-MDBR was reclaimed in one step with total organic carbon less than 1.7 mg/L and electrical conductivity less than 120 µS/cm. Furthermore, the result of the DNA extraction kit recorded that Methanosaeta thermophila was a critical archaea for high COD removal and bioreactor stability.

Innovative upflow anaerobic sludge osmotic membrane bioreactor for wastewater treatment.

A novel upflow anaerobic sludge-forward osmotic membrane bioreactor was developed for simultaneous wastewater treatment, membrane fouling reduction, and nutrient recovery. An upflow anaerobic sludge blanket (UASB) reactor was incorporated into the system, suspending the anaerobic sludge at the bottom of the reactor. A forward osmosis membrane replaced the traditional three-phase separator of the UASB technology. The removals of chemical oxygen demand, PO43-, and NH4+ were all more than 95% with low membrane fouling in this system. Halotolerant Fusibacter, which can ferment organics to acetate, was increased rapidly from 0.1% to 5% in this saline environment. Acetoclastic Methanosaeta was the most dominant prokaryotes and responsible for majority of methane production. Reduction of membrane fouling in this system was verified by the fluorescence excitation-emission matrix spectrophotometry. Furthermore, phosphorus recovery and salinity build-up mitigation were achieved using periodic microfiltration to recover 57-105 mg/L phosphorus from pH 9 to 12.