Despite growing scientific interest in the past decade, bipolar membrane electrodialysis has seen limited advancement in controlled operation of water dissociation via the bipolar membrane (BPM). For nutrient recovery applications, such as ammonia (NH₃) extraction from anaerobic digestion reject water, implementing in-situ pH control in the base solution could enhance energy efficiency. By controlling the electric current, pH is regulated through OH⁻ generation from the bipolar membrane (BPM). Once the targeted pH is reached, the electric current is applied in pulses and pauses with the purpose to sustain and to not overpass the pH setpoint. A selective electrodialysis reversal (SEDR) combined with a two-compartment bipolar membrane electrodialysis (BPMC) and vacuum membrane stripping (VMS) enabled the recovery and conversion of ammonium ions (NH₄⁺) into volatile ammonia (NH₃). Operating the BPMC with the developed pH control method lowered energy consumption (E_NH4⁺) and improved current efficiency for NH₄⁺ removal compared to constant current (CC) operation. Under pH control, the BPMC maintained the target pH throughout the whole operation, with an E_NH4⁺ between 12.5 and 35.3 MJ·kgN⁻¹, compared to 12.1 and 78.6 MJ·kgN⁻¹ under CC. The current efficiency was maintained across setpoints with pH control, ranging between 25 % and 29 %. With CC, the current efficiency declined from 27 % to 12 % at higher current densities. Furthermore, pH control applying a pulsed electric current reduced the occurrence of scaling by minimising the transport of divalent cations across the cation exchange membrane and CO₂ formation in the acid compartment. Similar removal efficiencies were attained, applying pH controlled operation and CC; however, both methods performed a declining removal efficiency during 30 h operation. The developed pH control method can provide distinct improvement in scale-up applications, where energy reduction by preventing excessive water dissociation by the BPM is of interest. In addition, external caustic dosing can be substituted by pH control with a BPMC layout of the stack, reducing the residual impurities of the chemical dosing.

This mini review explores the potential of visible light–driven bismuth vanadate (BiVO₄)-based photoanodes for removing trace organic pollutants from water. It highlights the advantages of using BiVO₄-based photoanodes over conventional UV-driven photoanodes in water treatment. The mechanism of reactive species generation through water oxidation is discussed. The review also highlights the role of sulfate and sulfite radicals in enhancing pollutant degradation. Furthermore, it evaluates how heterojunction formation improves the removal efficiency of BiVO₄-based photoanodes by reducing charge carrier recombination. Limited research on BiVO₄-based photoanodes for the simultaneous removal of multiple organic pollutants at low concentrations (<1 mg L⁻¹) from real wastewater is identified as a key knowledge gap. Addressing this gap could advance the application of BiVO₄-based photoanodes in photoelectrocatalytic-based advanced oxidation processes.

The anaerobic degradation of phenolic compounds presents substantial challenges due to their toxicity to methanogenic biomass and inherently low conversion rates. Recent studies indicate that nano-magnetite can stimulate direct interspecies electron transfer (DIET), potentially enhancing phenol conversion and methane production. This study employed two anaerobic membrane bioreactors (AnMBRs) to investigate phenol and p-cresol degradation under stepwise increasing loading rates, with complete retention of biomass in both reactors. While AnMBR-C served as a control, nano-magnetite was additionally supplemented to reactor AnMBR-M at a concentration of 40 mmol/L in Phase 1 and 20 mmol/L in Phase 2. Results demonstrated that AnMBR-M supplemented with 20 mmol/L nano-magnetite tolerated higher phenolic loading rates compared to AnMBR-C. In Phase 2, a higher total Fe concentration was observed in AnMBR-M, suggesting an enhanced electron transfer mechanism via dissimilatory iron reduction-oxidation cycle. Follow-up batch experiments revealed that magnetite-adapted biomass had more tolerance to phenol inhibition. A 16S-rRNA sequencing was conducted to characterize microbial communities within both reactors. Results suggested that DIET was stimulated in Phase 1, as shown by the enrichment of the electrogenic Pseudomonas and Methanolinea in AnMBR-M. However, the possibly stimulated DIET in Phase 1 could not alleviate the inhibition caused by excessive 40 mmol/L nano-magnetite dosage. Notably, there was no significant difference between the genera of AnMBR-C and AnMBR-M by the end of Phase 2. However, short-chain fatty acid degrader Mesotoga was more enriched in AnMBR-M. Moreover, species-level analysis showed that AnMBR-M had a sixfold higher relative abundance of Methanosaeta harundinacea compared to AnMBR-C.

Abstract: Presence of carbohydrates hampers protein degradation in anaerobic digesters. To understand this phenomenon, we used proteogenomics to identify the active protein-degraders in the presence of low and high carbohydrates concentrations. Active metabolic pathways of the identified protein-degraders were investigated using proteomics with ¹³C-protein substrates (protein stable isotope probing). Results showed that 1) Acinetobacter was the active protein-degraders under both protein-fed and protein-glucose mixture-fed conditions, 2) the relative abundance of Acinetobacter was not affected by the presence of carbohydrates, 3) the incorporation of the ¹³C-labelled protein substrate was predominantly observed in outer membrane-bound proteins and porin proteins, which are associated with proteinases or the transportation of amino acids across the cell wall. The Acinetobacter metabolic model and the incubation conditions suggested that glucose and proteins were degraded through anaerobic respiration. The negative impact of carbohydrates on protein biodegradation was attributed to Acinetobacter's preference for carbohydrates. This work highlights that efficient degradation of protein and carbohydrate mixtures in anaerobic digesters requires a staged or time-phased approach and enrichment of active protein-degraders, offering a new direction for process optimization in anaerobic digestion systems.

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Purpose of Review: Liquid crystal monomers (LCMs), used extensively in liquid crystal displays (LCDs), have emerged as persistent, bioaccumulative, and toxic organic pollutants. A network analysis of SCOPUS data revealed significant knowledge gaps, especially concerning the fate of LCMs in WWTPs. The available literature highlights that influent LCM concentrations vary widely, with elevated levels linked to industrial and e-waste recycling activities. This review examines the occurrence, fate, and treatment of LCMs, particularly fluorinated LCMs (F-LCMs), in wastewater treatment plants (WWTPs). Recent Findings: Conventional WWTP processes achieve moderate removal efficiencies (~ 84%) for LCMs, but F-LCMs often persist. Advanced treatment techniques such as UV/peroxydisulfate (UV/PDS) showed removal rates of 77–84% for LCMs with biphenyl and ethoxy groups. These groups alter electron distribution, making the molecules more susceptible to oxidative attack by reactive species such as hydroxyl and sulfate radicals. Degradation pathways include cleavage of biphenyl, ethoxy, and C-F bonds, producing less toxic by-products such as oxalic acid and cyclohexane. However, some degradation intermediates formed are toxic, necessitating further research of the treatment processes. Summary: This review underscores the need for systematic monitoring of LCMs in wastewater and their transformation products in treated wastewater and sludge, alongside advancements in treatment technologies to mitigate environmental and health risks. This review highlights the urgency of improving wastewater management strategies for LCMs and the need for future research to address the critical knowledge gaps.

The removal of ammonium and ammonia, represented as total ammoniacal nitrogen (TAN), from reject water through electro-dialysis (ED) and bipolar membrane electrodialysis (BPMED) encounters challenges such as organic fouling, NH₃ back-diffusion, and high energy consumption. The efficacy of electrodialysis reversal (EDR) combined with bipolar membrane electrodialysis using cation-exchange membranes (BPC) was assessed as a more practical configuration (EDR + BPC). Additionally, a novel configuration involving monovalent selective cation-exchange membranes (MSCEMs) in an EDR + BPC setup (SEDR + BPC) was investigated. Comparisons were made among BPMED, EDR + BPC, and SEDR + BPC under three load ratios (L_N) of 0.8, 1, and 1.3 during continuous operation. The innovative SEDR + BPC configuration, with an L_N of 0.8, exhibited the lowest energy consumption for transported TAN (E_TAN) at 4.4 MJ·kgN⁻¹ removal and achieved the highest TAN removal efficiency of 78 % with an L_N of 1.3. In contrast to conventional BPMED, SEDR + BPC allowed for the recovery of potentially back-diffused NH₃ into the acid chamber, minimizing transport losses. Furthermore, scaling in the base chamber was reduced due to the contribution of MSCEMs when applying an L_N of 0.8. The MSCEMs increased the molar ratio of TAN over (Mg²⁺ + Ca²⁺) in the concentrate and decreased it in the diluate. EDR + BPC and SEDR + BPC configurations exhibited stable and lower cell resistance throughout the operation compared to BPMED, attributed to their ability to generate higher concentration gradients. The results clearly demonstrated the feasibility of low-energy TAN removal from real reject water from sludge anaerobic digestion using the SEDR + BPC setup.

Structural extracellular polymeric substances (SEPS) as valuable biopolymers, can be extracted from waste activated sludge (WAS). However, the extraction yield is typically low, and detailed information on SEPS characterizations, as well as proper treatment of the sludge after SEPS extraction, remains limited. This study aimed to optimize the conditions of heating-Na₂CO₃ extraction process to increase the yield of SEPS extracted from WAS. Subsequently, SEPS were characterized, and, for the first time, insights into their protein composition were uncovered by using proteomics. A maximum SEPS yield of 209 mg g^-1 volatile solid (VS) was obtained under optimal conditions: temperature of 90 °C, heating time of 60 min, Na⁺ dosage of 8.0 mmol/g VS, and pH required to precipitation of 4.0, which was comparable to that from the aerobic granular sludge reported in literature. Proteomics analysis unveiled that the proteins in SEPS primarily originated from microorganisms involved in nitrogen fixation and organic matter degradation, including their intracellular and membrane-associated regions. These proteins exhibited various catalytic activities and played crucial roles in aggregation processes. Besides, the process of SEPS extraction significantly enhanced volatile fatty acid (VFA) production during the anaerobic fermentation of residual WAS after SEPS extraction. A maximum VFA yield of 420 ± 14 mg COD/g VS_added was observed in anaerobic fermentation of 10 d, which was 77.2 ± 0.1 % higher than that from raw sludge. Mechanism analysis revealed that SEPS extraction not only improved WAS disintegration and solubilization but also reduced the relative activity of methanogens during anaerobic fermentation. Moreover, SEPS extraction shifted the microbial population during anaerobic fermentation in the direction towards hydrolysis and acidification such as Fermentimonas sp. and Soehngenia sp. This study proposed a novel strategy based on SEPS extraction and VFA production for sludge treatment, offering potential benefits for resource recovery and improved process efficiency.

Simulated ammonium sulfate scrubber effluent was treated using bipolar membrane electrodialysis (BPMED) to recover sulfuric acid for reuse in the scrubber, and ammonium hydroxide as a product, without using any chemicals. The effect of pH and temperature of the feed solution on the energy consumption of the BPMED and the purity of the recovered acid and base were investigated in batch experiments. Experiments were conducted during a 3-hour period using a scrubber effluent with the following characteristics: 50 g/L ammonium sulfate, pH ranging from 1 to 5 and temperature ranging from 20 °C to 30 °C. The energy consumption at pH 5 was lower than that at pH 1, i.e., 6.9 MJ/kg SO₄^2- and 7.7 MJ/kg SO₄^2-, respectively. The purity of the acid recovered from the feed solution with a pH of 5 was 36 %, whereas the feed with a pH of 1 resulted in an acid purity of 72 %. These values corresponded to a mass of ammonia diffusion of 6.9 g and 2.3 g, respectively. The purity of the base recovered from the feed with a pH of 5 was 84 %, whereas this was 69 % for the feed with a pH of 1. Higher temperature of the feed solution, i.e., 30 °C compared to 20 °C, resulted in a lower energy consumption: 7.1 MJ/kg SO₄^2- compared to 9.5 MJ/kg SO₄²⁻, respectively. The temperature had a very limited effect on the acid and base purities, with values ranging from 80 % to 82 % for the acid, and from 33 % to 36 % for the base. Our study demonstrated the effective application of BPMED for the treatment of simulated acidic scrubber effluent, with simultaneous recovery of ammonia and sulfuric acid.

While air stripping combined with acid scrubbing remains a competitive technology for the removal and recovery of ammonia from wastewater streams, its use of strong acids is concerning. Organic acids offer promising alternatives to strong acids like sulphuric acid, but their application remains limited due to high cost. This study proposes an integration of air stripping and organic acid scrubbing with bipolar membrane electrodialysis (BPMED) to regenerate the organic acids. We compared the energy consumption and current efficiency of BPMED in recovering dissolved ammonia and regenerating sulphuric, citric, and maleic acids from synthetic scrubber effluents. Current efficiency was lower when regenerating sulphuric acid (22 %) compared to citric (47 %) and maleic acid (37 %), attributable to the competitive proton transport over ammonium across the cation exchange membrane. Organic salts functioned as buffers, reducing the concentration of free protons, resulting in higher ammonium removal efficiencies with citrate (75 %) and malate (68 %), compared to sulphate (29 %). Consequently, the energy consumption of the BPMED decreased by 54 % and 35 % while regenerating citric and maleic acids, respectively, compared to sulfuric acid. Membrane characterisation experiments showed that the electrical conductivity ranking, ammonium citrate > ammonium malate > ammonium sulphate, was mirrored by the energy consumption (kWh/kg-N recovered) ranking, ammonium sulphate (15.6) < ammonium malate (10.2) < ammonium citrate (7.2), while the permselectivity ranking, ammonium sulphate > ammonium citrate > ammonium malate, aligned with calculated charge densities. This work demonstrates the potential of combining organic acid scrubbers with BPMED for ammonium recovery from wastewater effluents with minimum chemical input.

Bovine serum albumin (BSA) and casein (CAS) were used in batch tests to compare the protein degradation in the presence and absence of carbohydrates and volatile fatty acids (VFAs). The modified Gompertz model was applied to estimate reaction rates. The results showed that deamination was the rate-limiting step, with a rate ranging between 2.7 and 12.7 mgN·h⁻¹. Higher protein structural complexity negatively affected protein hydrolysis, deamination, and methanogenesis by a factor of 1.6–3.8; whereas a higher protein concentration improved the conversion rates. A carbohydrate:protein COD ratio of 1 improved the hydrolysis rate of BSA from 26 mg·h⁻¹ to 45 mg·h⁻¹, and that of CAS from 98 mg·h⁻¹ to 157 mg·h⁻¹; whereas the deamination rate slightly decreased from 2.7 mg N·h⁻¹ to 2.5 mg N·h⁻¹ and from 6.0 mg N·h⁻¹ to 5.6 mg N·h⁻¹. Additionally, an initial VFAs:protein COD ratio of 1 decreased the CAS deamination rate by 17 %.

Bitumen fume condensate (BFC) is a hazardous wastewater generated at asphalt reclamation and production sites. BFC contains a wide variety of potentially toxic organic pollutants that negatively affect anaerobic processes. In this study, we chemically characterized BFC produced at an industrial site and evaluated its degradation under anaerobic conditions. Analyses identified about 900 compounds including acetate, polycyclic aromatic hydrocarbons, phenolic compounds, and metal ions. We estimated the half maximal inhibitory concentrations (IC₅₀) of methanogenesis of 120, 224, and 990 mgCOD·L⁻¹ for three types of anaerobic biomass, which indicated the enrichment and adaptation potentials of methanogenic biomass to the wastewater constituents. We operated an AnMBR (7.0 L, 35 °C) for 188 days with a mixture of BFC, phenol, acetate, and nutrients. The reactor showed a maximum average COD removal efficiency of 87.7 ± 7.0 %, that corresponded to an organic conversion rate of 286 ± 71 mgCOD⁻¹·L⁻¹d⁻¹. The microbial characterization of the reactor's biomass showed the acetoclastic methanogen Methanosaeta as the most abundant microorganism (43 %), whereas the aromatic and phenol degrader Syntrophorhabdus was continuously present with abundances up to 11.5 %. The obtained results offer the possibility for the application of AnMBRs for the treatment of BFC or other petrochemical wastewater.

Treating protein-rich wastewater using cost-effective and simple-structured single-stage reactors presents several challenges. In this study, we applied an anaerobic sequencing batch reactor (AnSBR) to treat protein-rich wastewater from a slaughterhouse. We focused on identifying the key factors influencing the removal of chemical oxygen demand (COD) and the settling performance of the sludge. The AnSBR achieved a maximum total COD removal of 90%, a protein degradation efficiency exceeding 80%, and a COD to methane conversion efficiency of over 70% at organic loading rates of up to 6.2 g COD L⁻¹ d⁻¹. We found that the variations in both the organic loading rate within the reactor and the hydraulic retention time in the buffer tank had a significant effect on COD removal. The hydraulic retention time in the buffer tank and the reactor, which determined the ammonification efficiencies and the residual carbohydrate concentrations in the reactor liquid, affected the sludge settleability. Furthermore, the genus Clostridium sensu stricto 1, known as protein- and lipids-degraders, was predominant in the reactor. Statistical analysis showed a significant correlation between the core microbiome and ammonification efficiency, highlighting the importance of protein degradation as the governing process in the treatment. Our results will provide valuable insights to optimise the design and operation of AnSBR for efficient treatment of protein-rich wastewater.

In this research, photoelectrocatalytic (PEC) based advanced oxidation process (AOP) was studied for the removal of multiple OMPs through an oxidative mechanism. This study investigated the application of a BiVO4 photoanode in simultaneous removal of three selected OMPs: acetaminophen (ACT), benzotriazole (BTA) and propranolol (PRO). This study was carried out in demineralized water with a starting concentration of each organic micro-pollutant (OMP) at 45 μg L−1. In order to fabricate BiVO4 photoanodes, a facile and effective dip-coating method was used to deposit BiVO4 photocatalytic layers on fluorine doped tin oxide (FTO) substrate. UV–vis diffusive reflectance spectroscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) confirmed the successful fabrication of porous BiVO4 photoanode having an absorbance edge at around 526 nm. The fabricated photoanode showed incident photon to current conversion efficiency (IPCE) of 9.23% (λmax=445 nm) under 1 Sun standard illumination. Application of the fabricated photoanodes for the simultaneous removal of ACT, PRO and BTA at an applied voltage of 1 V (vs Ag/AgCl) under solar simulated light resulted in 99% removal of both ACT and PRO, and 70% removal of BTA. The first order rate coefficients and half-life times of ACT and PRO were about three times higher than those of BTA.

Gas-mixing is commonly applied in anaerobic digesters, yet the resulting flow and hydraulic mixing are difficult to evaluate because of limited full-scale experimental data and uncertainties in integrating sludge rheological data. This study used computational fluid dynamics (CFD) to assess the impact of treated sludge rheology on flow and mixing characterisation in a full-scale biogas-mixed digester. The CFD model, which was firstly validated using a lab-scale setup, showed that flow and mixing predictions depended on the rheological properties, especially at low shear rates. The predicted dominant shear rate was out of the effective shear-rate range of the Ostwald model, leading to flow and mixing performance overestimation. The results indicated that there are limitations in applying the Ostwald model and the conventional approaches for determining dead-zone. The Herschel-Bulkley model was more appropriate for the prevailing low shear rates and predicted large viscosity gradients in the digester, indicating two distinct compartments with different flow and mixing behaviour based on the gas-sparging height: a plug-flow compartment with dominant vertical convection above, and a dead-zone compartment with considerable segregation below. The results showed that the applied gas-sparging induced insufficient flow and mixing, but contributed to the well-functioning of the digester. To correctly assess flow and mixing, the applied rheological data should be in agreement with the type of sludge that is treated in the digester. Our results indicate that the shear rate in the digester must be increased and various options for achieving this are proposed.

Traditionally, industrial processes produce wastes that, even though often containing useful materials, are discarded, contributing to environmental pollution and depletion of natural resources. An example of such wastes are brines, flows of concentrated salts, produced in water treatment processes, which are now routinely discharged into receiving water bodies. Brines however can also be considered as flows of reusable materials which should be recovered, and the Zero Brine cooperation project aims to develop processes for that purpose. For a demineralized water production plant in the port of Rotterdam (the Netherlands), a closed water processing cycle was proposed to treat the large volume of spent Ion Exchange (IEX) regenerant brine which, apart from recovering demineralized water, is also intended to produce magnesium (Mg2+) and calcium (Ca2+) salts, with the highest purity possible, from the otherwise discharged brine. The process scheme includes nanofiltration (NF) for separating mono- and multivalent ions, followed by sequential chemical precipitation of Mg2+ and Ca2+ ions from the NF concentrate, and production of demineralized water by evaporation of the NF permeate. The concentrate of monovalent ions produced in the evaporator, essentially a concentrated sodium chloride solution, in its turn might be reused for IEX regeneration. Part of the supernatant of the sequential precipitation may be fed to the evaporator as well, but bleeding the other part of this supernatant is essential in order to maintain process stability, avoid accumulation of minor pollutants, and reduce scaling. In this study, various scenarios to operate the process were modeled, using PHREEQC and Excel. According to the simulation results, recovery of ≈97% of Mg2+ and Ca2+ is possible, the latter with a higher purity than the former. The main factors affecting the results are the concentration of carbonate present in the spent IEX regenerant, as well as characteristics of the NF membrane and the dosing of sodium hydroxide in the sequential precipitation steps. The results of the simulations were used for the design and operation of a pilot plant, comprising all mentioned process steps.

Abstract: Protein-rich agro-industrial waste streams are high in organic load and represent a major environmental problem. Anaerobic digestion is an established technology to treat these streams; however, retardation of protein degradation is frequently observed when carbohydrates are present. This study investigated the mechanism of the retardation by manipulating the carbon source fed to a complex anaerobic microbiota and linking the reactor performance to the variation of the microbial community. Two anaerobic acidification reactors were first acclimated either to casein (CAS reactor) or lactose (LAC reactor), and then fed with mixtures of casein and lactose. Results showed that when lactose was present, the microbial community acclimated to casein shifted from mainly Chloroflexi to Proteobacteria and Firmicutes, the degree of deamination in the CAS reactor decreased from 77 to 15%, and the VFA production decreased from 75 to 34% of the effluent COD. A decrease of 75% in protease activity and 90% in deamination activity of the microbiota was also observed. The microorganisms that can ferment both proteins and carbohydrates were predominant in the microbial community, and from a thermodynamical point of view, they consumed carbohydrates prior to proteins. The frequently observed negative effect of carbohydrates on protein degradation can be mainly attributed to the substrate preference of these populations. Keypoints: • The presence of lactose shifted the microbial community and retarded anaerobic protein degradation. • Facultative genera were dominant in the presence and absence of lactose. • Substrate-preference caused retardation of anaerobic protein degradation.

Treating petrochemical wastewater is a challenge for conventional anaerobic reactors. One example is coal gasification wastewater that, besides its salinity, is rich in toxic and inhibitory aromatics, such as phenol, cresols, and resorcinol. Studies have shown that phenol and p-cresol share the same degradation intermediates, whereas resorcinol is degraded via another route. This study investigated the simultaneous degradation of p-cresol or resorcinol with phenol under anaerobic saline conditions. Batch experiments with anaerobic phenol-degrading biomass were conducted to assess the feasibility of the degradation of p-cresol and resorcinol. Volumetric uptake rates of 11.4 ± 2.4 mg_p-cresol·L^–1d^–1 and 4.2 ± 1.9 mg_resorcinol·L^–1d^–1 were determined. The effect of p-cresol and resorcinol on the specific methanogenic activity and the cell viability in phenol-degrading and non-adapted biomass was assessed. Half maximal inhibitory concentration (IC₅₀) values of 0.73 g_p-cresol·L^-1 and 3.00 g_resorcinol·L^-1 were estimated for phenol-degrading biomass, whereas IC₅₀ values of 0.60 g_p-cresol·L^-1 and 0.25 g_resorcinol·L^-1 were estimated for the non-adapted biomass. p-Cresol caused a higher decrease in the non-damaged cell counts in comparison to resorcinol. Two anaerobic membrane bioreactors under saline conditions [8 g Na⁺·L^–1] were fed with mixtures of either phenol-p-cresol or phenol-resorcinol. At an influent phenol concentration of 2 g·L^-1, maximum conversion rates of 22 mg_p-cresol·gVSS^-1d^–1 and 16 mg_resorcinol·gVSS^–1d^–1 were found. In both AnMBRs, Syntrophorhabdus sp. and Methanosaeta sp. were the most abundant bacteria and methanogen, respectively. The feasibility of simultaneous conversion of phenolic compounds under saline conditions in AnMBRs opens novel perspectives for the high-rate anaerobic treatment of chemical wastewater.

Phenol conversion under saline thermophilic anaerobic conditions requires the development and sustenance of a highly specialized microbial community. In the present research, an anaerobic membrane bioreactor (AnMBR) fed with an influent containing 0.5 g·L⁻¹ phenol and 6.5 gNa⁺·L⁻¹ was operated at 55 °C for 300 days. Phenol degradation was limited when phenol was the sole substrate. However, the phenol removal efficiency significantly (p < 0.001) increased to 80 % corresponding to a conversion rate of 29 mgPhenol·gVSS⁻¹d⁻¹ when acetate (0.5 gCOD·L⁻¹) was simultaneously provided. Isotopic analysis using 1–¹³C labeled acetate and measuring ¹³CH₄ revealed that acetate was first oxidized to hydrogen and CO₂, prior to methanogenesis, resulting in an increased abundance of hydrogenotrophic methanogens. It is hypothesized that the latter is of crucial importance for achieving effective anaerobic oxidation of phenol and its metabolites. Remarkably, the phenol conversion rate in the membrane-associated biomass was three times higher than in the suspended biomass. The observed difference in the conversion rate could be explained by the presence of an increased abundance of hydrogenotrophic methanogens in the membrane-associated biomass confirmed by a microbial community analysis of Archaea. Benzoate was measured in the permeate suggesting that phenol degradation occurred via the benzoyl-CoA pathway. The results of the current study suggest that syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis, which results in the presence of an abundant electron sink, plays a key role in enhancing thermophilic phenol degradation. The obtained insights widen the application of anaerobic digestion to treat saline phenolic-rich wastewater at high temperatures.

Flux enhancers (FEs) have been successfully applied for fouling mitigation in membrane bioreactors. However, more research is needed to compare and optimise different dosing strategies to improve the filtration performance, while minimising the use of FEs and preventing overdosing. Therefore, the goal of this research is to develop an optimised control strategy for FE dosing into an AnMBR by developing a comprehensive integrated mathematical model. The integrated model includes filtration, flocculation, and biochemical processes to predict the effect of FE dosing on sludge filterability and membrane fouling rate in an AnMBR. The biochemical model was based on an ADM1, modified to include FEs and colloidal material. We developed an empirical model for the FE‐induced flocculation of colloidal material. Various alternate filtration models from the literature and our own empirical models were implemented, calibrated, and validated; the best alternatives were selected based on model accuracy and capacity of the model to predict the effect of varying sludge characteristics on the corresponding output, that is fouling rate or sludge filterability. The results showed that fouling rate and sludge filterability were satisfactorily predicted by the selected filtration models. The best integrated model was successfully applied in the simulation environment to compare three feedback and two feedforward control tools to manipulate FE dosing to an AnMBR. The modelling results revealed that the most appropriate control tool was a feedback sludge filterability controller that dosed FEs continuously, referred to as ∆R ₂₀_10. Compared to the other control tools, application of the ∆R ₂₀_10 controller resulted in a more stable sludge filterability and steady fouling rate, when the AnMBR was subject to specific disturbances. The simulation environment developed in this research was shown to be a useful tool to test strategies for dosing flux enhancer into AnMBRs.