Xiang Li

Membrane fouling and biological toxicity are two main bottlenecks in treating azo dye wastewater using anaerobic membrane bioreactors (AnMBRs). This review examines how azo dye molecular structure affects AnMBR performance and membrane fouling. It discusses azo dye reduction, aromatic amine formation, microbial inhibition, and foulant formation. Aromatic amines may inhibit methanogenesis and promote the accumulation of hydrophobic foulants on membrane surfaces. At low dye loadings, stable treatment may be supported under favorable operating conditions, whereas higher loadings may inhibit anaerobic activity and accelerate membrane fouling. The review evaluates membrane modification, biological enhancement and in situ electro-cleaning strategies. No single strategy has yet ensured long-term industrial operation. Reported concentration thresholds are mainly derived from single-dye laboratory studies and may not apply to actual textile wastewater. Future work should use data-driven fouling prediction and pilot trials with real wastewater to define AnMBR operating limits.

Owing to advantageous properties such as high mechanical strength and wear and hydrolysis resistance, polyvinylidene fluoride (PVDF)-based materials have been widely used to fabricate membranes utilizing in anaerobic membrane bioreactors (AnMBRs) for wastewater treatment. Though AnMBRs can be regarded as high-rate bioreactors, membrane fouling caused by organic, inorganic, and biological contaminants remains an inevitable challenge. In order to alleviate this issue, this review systematically summarizes modification methods including crosslinking, surface coating, and assembly for the loading of functional materials and inorganic nanoparticles onto the membrane surface. Additionally, this review indicates that modified PVDF-based membranes with enhanced conductive or antifouling properties can be effectively applied in AnMBRs, and better chemical oxygen demand (COD) removal efficiency can be achieved compared with those utilizing pristine PVDF membranes. Different from previous reviews, this review proposes technology intensification strategies utilizing pristine PVDF membranes including electrochemical AnMBR (electro-AnMBR) and anaerobic fluidized bed membrane bioreactor (AFMBR). Both of them have demonstrated enormous potential for mitigating membrane fouling relative to conventional AnMBR configurations. Spontaneously, this review underscores the critical need to integrate these intensification strategies with modified PVDF-based membranes as relative studies in this combined area. Therefore, this review provides comprehensive guidance on modification methods of PVDF membranes and technology intensification strategies utilizing modified PVDF-based membranes.

Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under a high OLR (over 3 g-VS/L d). Primarily, in terms of ammonia nitrogen inhibition, ammonia ions inhibit methane synthesis enzymes, and free ammonia (FAN) contributes to the imbalance of microbial protons. Regulation strategies include substrate C/N ratio regulation, microbial domestication, and ammonia nitrogen removal. In addition, with regard to acid inhibition, including volatile fatty acid (VFA) and long-chain fatty acid (LCFA) accumulation, the elevated acid concentration can contribute to reactive oxygen species stress, and a solution to this includes the addition of alkaline agents and trace elements or the use of microbial electrochemical and biofortification technology and micro-aeration-based AD technology. Furthermore, in terms of salinity inhibition, high salinity can result in a rapid increase in cell osmotic pressure, which can cause cell rupture, and water washing and bio-electrochemical AD are defined as solutions. Future research directions are proposed, mainly in terms of avoiding the introduction of novel containments into these regulation strategies and applying them in large-scale AD plants under a high OLR.

Kitchen waste has been confirmed as an appropriate substrate for anaerobic digestion, although means of alleviating the difficulties and time-consuming nature of the start-up phase need to be further explored. Based on the mechanism of anaerobic digestion, we discuss the factors influencing the anaerobic start-up phase of kitchen waste. By controlling the temperature, pH, organic loading rate, inoculation ratio and other parameters, the high activity of methane-producing archaea and other bacteria can be intensified, thereby increasing the biogas yield. Furthermore, we introduce the methods of substrate pretreatment, operating condition optimization and conductive material addition. Finally, we put forward future perspectives and research gaps related to accelerating the start-up phase of anaerobic bioreactors utilized for kitchen waste biodegradation.

This study investigated oleate inhibition concentration on mesophilic and thermophilic sludge by utilizing acetate and H₂/CO₂ (80:20, v/v) as substrate, respectively. In addition, another batch experiment was carried out to explore the influence of oleate loads (mM-oleate/g-VS) on methane production. Generally, the mesophilic anaerobic system was more stable than the thermophilic system, which embodied higher microbial abundance, higher methane yield, and higher oleate tolerance. Furthermore, this study provides a possible methanogenic pathway impacted by oleate under mesophilic and thermophilic conditions according to functional microbial composition. Lastly, this paper provides noticeable and avoidable oleate concentrations and loads under different experimental conditions as a guide for future anaerobic bioreactors of lipidic waste biodegradation.