Nitrification/denitrification mitigates excess nitrogen in wastewater and reduces nutrient pollution in recipient surface waters but emits substantial amounts of nitrous oxide (N₂O). Complete ammonia-oxidizing (comammox) bacteria provide novel opportunities to mitigate N₂O emissions from wastewater treatment systems. In this study, a down-flow hanging sponge (DHS) reactor with low-strength ammonia-based synthetic wastewater was used to culture comammox bacteria, to study the microbial community structure, and to assess the nitrogen removal performance. The results showed a high NH₄⁺-N removal efficiency of 98 ± 4 % and complete nitrification during the entire experimental period. 16S rRNA gene sequencing and metagenomic analysis showed that comammox-like Nitrospira dominated the DHS-retained sludge, and that comammox-like Nitrospira and ammonia-oxidizing archaea may have coexisted symbiotically. The dissolved N₂O emissions per NH₄⁺-N removed from the DHS reactor were much lower than those from conventional activated sludge processes, indicating that the DHS reactor could be effective in reducing N₂O emissions during wastewater treatment.

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Oil palm empty fruit bunch (OPEFB) is an abundant organic waste in Malaysia that is often disposed of through field burning. A previous study has shown that solar-driven steam gasification of OPEFB can produce hydrogen-rich syngas with an energy upgrade factor of 1.2 and a carbon conversion efficiency of 95.1 %. Beyond its potential as a biofuel, OPEFB can also act as a carbon sink, capturing photosynthetically stored carbon. This study explores the potential of amplifying OPEFB's negative carbon emissions through solar-driven gasification, using CO₂ as the gasifying agent. In this work, a Central Composite Design (CCD) approach was employed to assess the influence of temperature (1100–1300 °C) and CO₂/OPEFB molar ratio (1.6–3.0) on H₂/CO molar ratio and energy upgrade factor, with a constant OPEFB flow rate of 1.8 g/min. The results demonstrated that at an energy upgrade factor of 1.4, 94.9 % of the total carbon was converted into syngas with a H₂/CO molar ratio of 0.3. The maximum observed net carbon capture yield of 0.4 g C/g OPEFB was achieved at 1300 °C and a CO₂/OPEFB molar ratio of 3.0. The remaining carbon (94.4–95.7 wt %) was converted into biochar with low heavy metal content, which has potential as a soil enhancer.

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Faecal contamination across the lettuce value chain was assessed in Maputo, Mozambique. Escherichia coli was used as an indicator of faecal contamination, with concentrations ranging from 3.4 to 5.7 log units/100 ml in groundwater, river water and partially treated wastewater. Municipal tap water used to wash lettuce heads in the markets had lower than 1 log unit/100 ml. Irrespective of the source of irrigation water, the lettuce heads were contaminated throughout the value chain, with concentrations ranging between 6.5 and 7.8 log units/100 g. Interventions and awareness raising should be applied at every stage of the value chain.

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The study investigated the effects of long-chain fatty acids (LCFA) on anaerobic sludge treating lipid-rich wastewater. It involved batch experiments with three sludge samples: two acclimated to lipids and one non-acclimated. The experiments aimed to observe the degradation of LCFA, specifically oleate and palmitate, by dosing them at concentrations ranging from 50 to 600 mg/L. Measurements of the cumulative methane production and the LCFA concentration, quantified as fat, oil, and grease (FOG) were performed. To ensure the sludge was free from other biodegradable substrates, part of the samples was pre-incubated without feed. The tests were conducted with both pre-incubated and non-incubated inoculum sludge. The findings revealed that oleate was degraded more efficiently than palmitate across all sludge samples, with a greater conversion rate to methane. Sludge samples acclimated to lipids showed a superior capacity to degrade LCFA compared to non-acclimated ones. It was noted that at concentrations above 400 mg/L, the conversion of LCFAs to intermediate compounds was inhibited, although this did not affect the subsequent methane production. The study concludes with a recommendation for sludge adaptation strategies to boost the efficiency of anaerobic wastewater treatment systems dealing with lipid-rich waste. The presence of LCFA-degrading bacteria families like Kosmotogaceae, Petrotogaceae, and Synergistaceae in the acclimated sludge samples underscores the adaptation and potential for improved degradation performance.

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Vinasse is a by-product of sugarcane processing which is often used in fertigation; however, the direct use of vinasse harms the environment and reduces soil productivity due to its physicochemical properties. Anaerobic digestion (AD) offers an alternative to mitigate part of the negative effects. Anaerobic high-rate reactors, which mainly rely on sludge granulation, are mostly used in AD of vinasse wastewater. However, the composition of vinasse such as high concentration of solids and organic matter, high salinity, low pH, and high concentrations of sulfate, affect granule formation, leading to sludge washout. Anaerobic membrane bioreactors (AnMBR) present an alternative for vinasse treatment, eliminating the need for sludge granulation and producing a nutrient-rich effluent with minimal residual organics and no suspended solids. Research on sugarcane vinasse treatment using AnMBRs is limited. Most studies have employed submerged internal membrane modules, highlighting the need for further research with different reactor configurations to enhance process performance. In this study, an AnMBR equipped with an external inside-out crossflow ultrafiltration membrane was compared to an upflow anaerobic sludge blanket (UASB) reactor for the treatment of sugarcane vinasse. At a volumetric organic loading rate of up to 6 g COD. L-1.d-1, the UASB reactor reached 75% ± 7% of COD removal efficiency whereas the AnMBR generated a solids-free effluent and reached 88% ± 2% of COD removal efficiency. Microorganisms such as Clostridia, Bacteroidia, Mesotaga, Syner-01, Dehalococcoidia, Bacteroidia-DMER64, and Methanolinea were found as the most abundant. The results highlight the AnMBR potential as an effective alternative for treating sugarcane vinasse while overcoming the challenges posed by unsatisfactory sludge granulation.@en

Thermal hydrolysis process (THP) is a widely used pre-treatment method in the anaerobic digestion (AD) of waste municipal sewage sludge. A post AD dewatering step of the digestate produces a liquid stream called reject water. THP increases the concentration of humic substances (HSs) and nutrients in the produced reject water. Struvite precipitation is a widely used technique to remove and (potentially) recover PO₄³⁻ -P and the corresponding amount of total ammoniacal nitrogen from reject water. The chemical characteristics of the THP-produced HSs influence reaction yields and morphology of struvite. In our current study, struvite batch precipitation experiments were conducted at different pHs, and different concentrations of HSs, consisting of either melanoidins or humic acids. Our results showed that at pH 6.5 struvite precipitation was severely retarded. However, increased concentrations of melanoidins at pH 6.5 enhanced struvite precipitation. Batch experiments conducted at pH 7.25 and 8 with increased melanoidins concentrations showed PO₄³⁻-P precipitation yields over 86 %. Humic acids negatively impacted struvite precipitation at all analysed pH values, presumably because of Mg²⁺ complexation. Morphological analysis showed that the presence of both HSs affected Feret diameters, aspect ratio, and cleavage pattern of struvite. Also, HSs rendered coloured crystals. Overall, our results showed that struvite precipitation is affected by HSs intrinsic characteristics, affecting yield, morphology, and colour of the formed precipitates.

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Energy-efficient wastewater treatment plants (WWTPs) utilize systems like high-rate activated sludge (A-stage) system to redirect organics from wastewater are redirected into energy-rich sludge (A-sludge). Anaerobic membrane bioreactors (AnMBRs) offer lower footprint and higher effluent quality compared to conventional digesters. In this study, the biological treatment and the filtration performances of AnMBRs for A-sludge digestion under mesophilic and thermophilic conditions were comparatively evaluated through lab-scale experiments, mass balancing and dynamic modeling. Under thermophilic conditions, a higher COD fraction of the influent sludge was converted into methane gas than under mesophilic conditions (65% versus 57%). The energy balance indicated that the surplus energy recovery under thermophilic conditions was less than the additional energy required for heating the AnMBR, resulting in a more than three-fold higher net energy recovery under mesophilic conditions. Therefore, operating an AnMBR for sludge digestion under mesophilic conditions has a higher potential to improve the energy balance in WWTPs.

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A biokinetic model based on BioWin's Activated Sludge Digestion Model (ASDM) coupled with a nitrous oxide (N₂O) model was setup and calibrated for a full-scale wastewater treatment plant (WWTP) Amsterdam West, in the Netherlands. The model was calibrated using one year of continuous data to predict the seasonal variations of N₂O emissions in the gaseous phase. This, according to our best knowledge, is the most complete full-scale data set used to date for this purpose. The results obtained suggest that the currently available biokinetic model predicted the winter, summer, and autumn N₂O emissions well but failed to satisfactorily simulate the spring peak. During the calibration process, it was found that the nitrifier denitrification pathway could explain the observed emissions during all seasons while a combination of the nitrifier denitrification and incomplete heterotrophic denitrification pathways seemed to be dominant during the emissions peak observed during the spring season. Specifically, kinetic parameters related to free nitrous acid (FNA) displayed significant sensitivity leading to increased N₂O production. The obtained values of two kinetic parameters, i.e., the FNA half-saturation during ammonia oxidising bacteria (AOB) denitrification and the FNA inhibition concentration related to heterotrophic denitrification, suggested a strong influence of the FNA bulk concentration on the N₂O emissions and the observed seasonal variations. Based on the suboptimal performance and limitations of the biokinetic model, further research is needed to better understand the biochemical processes behind the seasonal peak and the influence of FNA.

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Nitrous oxide (N₂O) emissions from wastewater treatment plants (WWTPs) exhibit significant seasonal variability, making accurate predictions with conventional biokinetic models difficult due to complex and poorly understood biochemical processes. This study addresses these challenges by exploring data-driven alternatives, using long short-term memory (LSTM) based encoder-decoder models as basis. The models were developed for future integration into a model predictive control framework, aiming to reduce N₂O emissions by forecasting these over varying prediction horizons. The models were trained on 12 months and tested on 3 months of data from a full-scale WWTP in Amsterdam West, the Netherlands. The dataset encompasses seasonal peaks in N₂O emissions typical for winter and spring months. The best performing model, featuring a 256–256 LSTM architecture, achieved the highest accuracy with test R² values up to 0.98 across prediction horizons spanning 0.5 to 6.0 h ahead. Feature importance analysis identified past N₂O emissions, influent flowrate, NH₄⁺, NO_x, and dissolved oxygen (DO) in the aerobic tank as most significant inputs. The observed decreasing influence of historical N₂O emissions over extended prediction horizons highlights the importance and significance of process variables for the model's performance. The model's ability to accurately forecast short-term N₂O emissions and capture immediate trends highlights its potential for operational use in controlling emissions in WWTPs. Further research incorporating diverse datasets and biochemical process inputs related to microbial activities in the N₂O production pathways could improve the model's accuracy for longer forecasting horizons. These findings advocate for hybridising deep learning models with biokinetic and mechanistic insights to enhance prediction accuracy and interpretability.

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A full-scale high-rate cascade anaerobic digestion (CAD) system was evaluated for its ability to enhance enzymatic sludge hydrolysis. The system included a newly built digester, innovatively divided into three pie-shaped compartments (500 m³ each), followed by an existing, larger digester (1500 m³). The system treated a mixture of waste activated sludge and primary sludge, achieving a stable total chemical oxygen demand reduction efficiency (56.1 ± 6.8 %), and enhanced sludge hydrolytic enzyme activities at a 14.5-day total solids retention time (SRT). High-throughput sequencing data revealed a consistent microbial community across reactors, dominated by consortia that govern hydrolysis and acidogenesis. Despite relatively short SRTs in the initial reactors of the CAD system, acetoclastic methanogens belonging to Methanosaeta became the most abundant archaea. ‬‬‬‬‬‬‬‬‬‬‬‬‬ This study proves that the CAD system achieves stable sludge reduction, accelerates enzymatic hydrolysis at full-scale, and paves the way for its industrialization in municipal waste sewage sludge treatment.

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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.

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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.

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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.

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Vinasse, a by-product of ethanol production, is generated at significant rates. While rich in nutrients such as calcium, magnesium, and potassium, its high solids, organic matter, acidity, and sulfate content pose challenges when disposed directly on soil, necessitating treatment. Anaerobic digestion is a viable solution, reducing organic pollution while recovering energy in the form of biogas, aligning with the biorefinery concept. Traditionally, sludge bed reactors and anaerobic contact reactors are utilized for vinasse processing, with sludge granulation being vital for treatment success. However, challenges such as sludge wash-out due to recalcitrant compounds, high solids concentration in the influent, low pH, salinity, and temperature hinder granule formation. Anaerobic membrane bioreactors (AnMBR) offer an alternative, simplifying treatment by integrating intensified pre- and post-treatment units. Due to complete sludge retention, AnMBRs achieve high COD removal efficiencies, yielding a suspended solids-free and largely disinfected effluent. Therefore, AnMBRs show promise for vinasse treatment, eliminating the need for sludge granulation and producing nutrient-rich effluent with minimal residual organics and suspended solids. In this study, an AnMBR equipped with an inside-out external crossflow ultrafiltration membrane was proposed for the treatment of vinasse. The AnMBR reached a COD removal efficiency of 95% ± 2.6% and produced 0.3 CH4 L. g COD removed -1 working at organic loading rates of 8 g COD. L-1 d-1 and membrane fluxes of 10 LMH. At organic loading rates of 10 g COD. L-1 d-1 and fluxes of 12 and 14 LMH, the COD removal efficiency decreased to 77% ± 11% and 73% ± 7.9%, respectively. The AnMBR technology represents an innovation for wastewater treatment, however, more research using the cross-flow configuration and different types of effluents is needed. Literature studies that address the treatment of sugar beet or sugarcane vinasse using AnMBR are still scarce. This study explored the potentials of AnMBR technology for vinasse treatment and contributes to the dissemination of this technology, opening new possibilities for vinasse processing.@en

A small-scale (up to 5 kWe) biogas-solid oxide fuel cell (SOFC) energy system is an envisioned system, which can be used to meet both electrical and thermal energy demand of off-grid settlements. SOFC systems are reported to be more efficient than alternatives like internal combustion engines (ICE). In addition to energy recovery, implementation of biogas-SOFC systems can enhance sanitation among these settlements. However, the capital investment costs and the operation and maintenance costs of a biogas-SOFC energy system are currently higher than the existing alternatives. From previous works, H2S removal by biochar was proposed as a potential local cost-effective alternative. This research demonstrates the techno-economic potential of locally produced biochars made from cow manure, jackfruit leaves, and jack fruit branches in rural Uganda for purifying the biogas prior to SOFC use. Results revealed that the use of biochar from cow manure and jack fruit leaves can reduce H2S to below the desired 1 ppm and substitute alternative biogas treatments like activated carbon. These experimental results were then translated to demonstrate how this biochar would improve the economic feasibility for the implementation of biogas-SOFC systems. It is likely that the operation and maintenance cost of a biogas-SOFC energy system can in the long run be reduced by over 80%. Also, the use of internal reforming as opposed to external reforming can greatly reduce the system capital cost by over 25% and hence further increase the chances of system economic feasibility. By applying the proposed cost reduction strategies coupled with subsidies such as tax reduction or exemption, the biogas-SOFC energy system could become economically competitive with the already existing technologies for off-grid electricity generation, like solar photovoltaic systems.@en

This study investigates the effects, conversions, and resistance induction, following the addition of 150 μg·L⁻¹ of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in a laboratory-scale micro-aerated anaerobic membrane bioreactor (MA-AnMBR). TMP and SMX were removed at 97 and 86%, indicating that micro-aeration did not hamper their removal. These antibiotics only affected the pH and biogas composition of the process, with a significant change in pH from 7.8 to 7.5, and a decrease in biogas methane content from 84 to 78%. TMP was rapidly adsorbed onto the sludge and subsequently degraded during the long solids retention time of 27 days. SMX adsorption was minimal, but the applied hydraulic retention time of 2.6 days was sufficiently long to biodegrade SMX. The levels of three antibiotic-resistant genes (ARGs) (sul1, sul2, and dfrA1) and one mobile genetic element biomarker (intI1) were analyzed by qPCR. Additions of the antibiotics increased the relative abundances of all ARGs and intI1 in the MA-AnMBR sludge, with the sul2 gene folding 15 times after 310 days of operation. The MA-AnMBR was able to reduce the concentration of antibiotic-resistant bacteria (ARB) in the permeate by 3 log.@en

This research investigated the contribution of wastewater-based nutrient supply, viz., nitrogen (N), phosphorous (P), and potassium (K), for lettuce production in the Infulene Valley, Mozambique, from July to September 2019. The research was conducted in groundwater- and wastewater-irrigated agricultural plots. Water samples were collected weekly, soil samples were collected before planting and after harvest, and lettuce samples were collected at harvest time. The nutrient content (N, P, and K) was measured, and a mass balance method was applied. Wastewater had distinctly higher nutrient contents than groundwater, which guaranteed crop nutrition during the growing stage. Wastewater contributed 88%, 96%, and 97% to the N, P, and K requirements, respectively. The crop yield in the wastewater-irrigated areas was 43,8 ± 16 tons/ha, which was higher than 35 ± 8 tons/ha observed for the groundwater-irrigated areas, but results showed no statistically significant differences. Conclusively, wastewater led to reduced soil-nutrient gap and can be a source of nutrients. Therefore, wastewater is regarded as an alternative nutrient source of interest, and if properly applied, it might reduce environmental health hazards, resulting from run-off or leaching of excess nutrients@en

Thermal hydrolysis process (THP) is a well-established anaerobic digestion (AD) pre-treatment technology. Despite the THP benefits the pre-treatment increases the concentrations of nutrients and melanoidins in the digestate reject water after dewatering. The increased concentrations of nutrients and melanoidins formed during THP-AD can impact downstream processes, such as struvite precipitation and partial nitritation/anammox (PN/A). In our present work, six full-scale PN/A influents and effluents were sampled in The Netherlands (4 with THP and 2 without THP). Full-scale samples were characterised and the stoichiometric O₂ consumption and melanoidins chelated to trace elements were analysed. The results showed that THP increased the concentration of total ammoniacal nitrogen (TAN), chemical oxygen demand (COD), total organic carbon (TOC), UVA 254 and colour, which are indicators of melanoidins occurrence. THP furthermore decreased the stoichiometric NO₃⁻-N production from the PN/A reaction in effluents. The disparity between stoichiometric and measured NO₃⁻ -N in the THP-using plants was explained by the proliferation of denitrifiers. Moreover, denitrification improved the N removal efficiency due to the consumption of the stoichiometrically-produced NO₃⁻ -N. Also, the stoichiometric O₂ consumption increased in the plants using THP, reaching up to 56% of the O₂ used for partial oxidation of TAN. Trace elements analysis revealed that the plants with elevated concentrations of melanoidins in the effluent showed a high percentage of chelated multivalent cations, particularly transition metals such as Fe. Kendall correlation coefficient analysis showed that the chelation of multivalent cations was correlated mainly with colour occurrence in the reject waters. Overall, the results indicated that in PN/A systems using THP-AD increased O₂ consumption and trace elements availability should be considered during the process design.

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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.

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Microalgae-bacteria biomass was digested through anaerobic digestion (AD) to produce biogas. Since microalgae typically have a more resistant cell wall than activated sludge (AS), its anaerobic biodegradability is limited. Therefore, three different pre-treatment techniques were evaluated for their effect on anaerobic biodegradability, especially of the extracellular polymeric substances (EPS). Firstly, heat at 70 °C for 1.5 h. Secondly, exposure to a mixture of commercially available enzymes (cellulase, α-amylase and protease), and thirdly, adding crude hydrolytic enzymes extracted by ultrasonication from a highly loaded anaerobic digestion cascade reactor. The first and third treatments had better effects than enzymatic pre-treatment with commercial enzymes, improving anaerobic biodegradability, the solubilisation of organic matter and increasing the methane production rate by 78 and 21 %, respectively. The EPS content of microalgae-bacteria biomass was considerably lower than reported for WAS, and about 40–50 % of the EPS consisted of proteins and polysaccharides. The hydrolysis of proteins and polysaccharides was quantified, and its effect on AD was discussed. A COD balance showed that the increase of soluble COD is due to the conversion of tightly bound EPS into loosely bound and soluble EPS but also due to the release of organic matter from cellular material. Although all pre-treatments increased the soluble organic fractions, especially those corresponding to EPS, none significantly improved the overall methane yield. Nevertheless, the methane production rate increased after thermal and pre-treatment with hydrolytic enzymes, which could result in smaller and more efficient anaerobic reactors.

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