Anaerobic digestion (AD) is a key technology for energy recovery in wastewater treatment plants, converting organic matter into methane-rich biogas. However, its efficiency is constrained by slow reaction rates, particularly during hydrolysis and methanogenesis, necessitating large reactor footprints for effective sludge digestion. Alternative AD configurations for process intensification present a promising solution to address these limitations by altering the design and operational setup of the AD process. In this review, key configuration-based AD intensification strategies were systematically analyzed, including recuperative thickening, single-stage thermophilic AD, acid/gas two-stage AD, temperature-phased AD, and multi-stage AD systems. The mechanisms, governing factors, efficiency gains, and scalability of these technologies were critically examined. These configurations demonstrated substantial improvements in methane production rates, process intensification, and the removal of solids and organics. Single-stage thermophilic and cascade AD technologies showed the highest potential for full-scale implementation, supported by successful real-world applications. Conversely, recuperative thickening exhibited promising results at lab and pilot scales but remains limited by its lower technology readiness level. Furthermore, the integration potential of such alternative systems with other intensification technologies was explored, highlighting synergistic opportunities for further optimization. This review provides critical insights into means to intensify AD process through alternative process configurations, offering a comprehensive guide for their application in biogas upgrading. It also identifies key challenges and outlines actionable steps to advance these systems toward widespread adoption in full-scale AD operations.

Physics-Informed Neural Networks (PINNs) represent a hybrid modeling paradigm that embeds governing physical laws, expressed as partial differential equations (PDEs), directly into neural network training. This integration enables models to respect fundamental conservation principles while learning from sparse or incomplete data. This review critically examines PINN applications in water and wastewater systems over the period 2014-2024, focusing on drinking water distribution networks, wastewater treatment plants, urban drainage systems, and water treatment processes. The review shows that PINNs excel in inverse problem solving by enabling parameter estimation and system identification from indirect observations, while maintaining physical consistency in extrapolation regimes where purely data-driven models fail. Documented applications report performance advantages, including 3-30 × reductions in required training data compared to standard neural networks, improved generalization under distribution shift, and successful use in scenarios involving partial observations and uncertain boundary conditions. However, critical limitations emerge: PINNs require well-posed problems with reliable governing equations, struggle with complex networked systems involving discrete components, face major convergence challenges for stiff or multi-scale PDEs, and still lack mature uncertainty quantification frameworks. Rather than positioning PINNs as replacements for established numerical methods, this work frames them as complementary tools that bridge mechanistic modeling and data-driven learning, offering particular value in parameter calibration, sensor placement optimization, and real-time state estimation for water infrastructure systems.

The revised EU Urban Wastewater Treatment Directive (UWWTD) requires wastewater treatment plants (WWTPs) to implement quaternary treatment to achieve 80% average percentage removal of selected organic micropollutants (OMPs), while moving toward energy neutrality. In this context, this study investigated and compared the performance of various pilot-scale ozone (O3)-based and UV-assisted advanced oxidation processes (AOPs) for the removal of OMPs from real secondary- and tertiary-treated effluents, and their energy demands to comply with the UWWTD. O3-based AOPs robustly achieved UWWTD compliance across different wastewater matrices and contaminant combinations. This supports the implementation of O3-based processes within multi-barrier treatment systems coupled with BAC (biological activated carbon) post-treatment. In contrast, H2O2 overdosing in O3-based processes reduced the likelihood of meeting UWWTD targets, suggesting an optimal H2O2/O3 ratio of 1-1.5. The multi-matrix, multi-process energy assessment reveals that O3-based processes are more efficient and cost-effective processes for OMPs removal, and UV-assisted treatments are more sensitive to wastewater quality. Energy self-sufficiency of WWTPs is unrealistic. For instance, photovoltaic (PV)-based supply scenarios face spatial constraints, typically requiring PV areas 2-10 times larger than a conventional WWTP footprint. Sensitivity analysis of biogas energy recovery shows that AOPs self-sufficiency is governed by oxidant dose. Results suggest that achieving energy neutrality may require off-site renewable supply, highlighting the limits of full on-site energy self-sufficiency. Overall, the results identify ozonation as the most robust, energy-efficient, and UWWTD-aligned option for quaternary wastewater treatment.

Solid-phase denitrification using biodegradable polymers such as polycaprolactone (PCL) is increasingly proposed as a sustainable alternative to conventional soluble carbon dosing. However, reported kinetic and stoichiometric parameters for PCL-based systems are often confounded by mass-transfer and dissolution limitations, hindering accurate determination of biological kinetics. In this study, the dissolution step was explicitly decoupled from microbial growth by presolubilizing PCL prior to use, enabling the direct experimental determination of biomass yield (Y) and maximum specific growth rate (μmax) under strictly anoxic batch conditions. Methanol was investigated in parallel as a benchmark soluble carbon source. Yield assays conducted over 12 independent replicates produced statistically similar yields of 0.35 ± 0.08 and 0.38 ± 0.08 g COD per g COD for methanol and PCL, respectively, indicating comparable stoichiometric efficiency for biomass synthesis. Dynamic nitrate depletion profiles were resolved through high-frequency batch testing and fitted using SUMO process modeling. The resulting μmax values were 1.3 day-1 for methanol and 2.1 day-1 for presolubilized PCL, indicating that when carbon availability is not limited by dissolution, under the tested decoupled batch conditions, PCL-derived substrates can support higher growth rates than conventional methanol. Long-term acclimation tests showed lower net biomass accumulation with PCL, attributable to its slower carbon release rather than to microbial capacity limits. These results provide the first direct determination of true biological kinetic parameters for PCL-based denitrification, independent of polymer hydrolysis effects. The findings demonstrate that the apparent kinetic constraints previously reported for solid PCL systems primarily reflect physicochemical mass-transfer limitations and not biological capacity. This work establishes design-ready kinetic parameters for integrating biodegradable polymers into predictive denitrification models, supporting the rational implementation of biodegradable polymeric carbon sources in sustainable nitrogen removal processes.

This study investigated the applicability of side-stream vacuum for intensification of anaerobic digestion (AD) at organic loading rates (OLRs) of 3.8-4.5 kgVS/m(3)/d (6.1-7.3 kgCOD/m(3)/d), and ammonia recovery at four times the OLR of a conventional AD. Initial operation showed a performance decline due to Methanosaeta dominance and its inability to resist vacuum, resulting in low methane yield (0.06 L/gCOD(feed), 15 % COD destruction) and high SCOD accumulation (12 g/L). Methanosarcinaceae enrichment under vacuum restored stability, achieving 49 %-53 % VSS destruction. Ammonia inhibition was mitigated by 44 %-47 % TKN recovery through ex-situ vacuum stripping, maintaining ammonia concentrations below 1 gN/L, compared to a potential inhibitory level of > 4 gN/L without ex-situ vacuum. The dominance of Methanosarcinaceae and successful ammonia recovery corresponded with stable operation at four times the OLR of conventional digesters. Biokinetic studies revealed a 155 %-232 % improvement in biomass-specific acetoclastic methanogenic activity through ex-situ vacuum. Fluorescence excitation-emission matrix-parallel factor analysis showed accumulation of the slowly biodegradable fluorescing organic. High fermentative bacterial counts were maintained, with increased populations of DMER64, Mesotoga, Synergistaceae, Clostridium_sensu_stricto_1, Pelotomaculum, and Syntrophomonas, suggesting resistance to vacuum stress, while Smithella decreased.

Performic acid (PFA) has emerged as a promising disinfectant for wastewater effluents and combined sewer overflows (CSOs), offering strong microbial inactivation with minimal formation of harmful disinfection byproducts (DBPs). This review systematically evaluates existing research on PFA performance across primary effluent, CSOs, and secondary effluent, emphasizing microbial inactivation kinetics, exposure modeling, DBP formation, and toxicity, while identifying knowledge gaps. Compared with traditional disinfectants such as free chlorine, chlorine dioxide, chloramines, and peracetic acid, PFA demonstrates comparable or superior bacterial inactivation while generating substantially lower concentrations of regulated halogenated DBPs. PFA also generates diverse oxygenated and nitrogen-containing transformation products, with PAA behaving similarly, whereas chlorine and chloramines form more persistent halogenated and nitrogenous byproducts. Disinfection efficacy of PFA varies across microbial groups, with enterococci, spores, and protozoan cysts demonstrating greater resistance, consistent with patterns observed for other disinfectants. However, PFA achieves faster inactivation at equivalent doses. Studies indicate that integral CT (ICT)-based models more accurately describe PFA inactivation under real wastewater conditions by capturing disinfectant decay and non-ideal hydraulics. DBP formation during PFA disinfection remains low, with halogenated DBPs detected only at high PFA concentrations (≥30 mg/L), and no nitrosamine formation reported. Acute toxicity assays show low ecotoxicity, although responses differ among species. Despite these promising findings, research gaps remain regarding PFA reactivity with complex wastewater matrices, inactivation of human enteric viruses and resistant bacterial spores, environmental fate of transformation products, and long-term ecological impacts. Overall, this review highlights PFA’s strong potential as a safer, effective disinfectant for wastewater treatment and identifies critical areas for future investigation to support full-scale implementation.

Performic acid (PFA) is receiving increasing attention as a fast-acting disinfectant for municipal wastewater effluents and combined sewer overflows (CSOs), where short contact times and highly variable matrices constrain conventional treatment. However, its practical adoption is limited by intrinsic chemical instability, safety considerations, and dependence on point-of-use generation. This critical review integrates peer-reviewed literature and patent evidence to evaluate how PFA production and delivery architectures govern field deployability. We compare five technology families including on-site precursor blending, distillation and reactive separation, co-delivery formulations, microfluidic on-demand generation, and electrochemical synthesis using structured evidence base and readiness-aware scoring framework. Performance is interpreted through the lens of time-integrated residual exposure, reflecting rapid oxidant decay and matrix-dependent demand. Reported full-scale and pilot studies indicate that PFA can achieve rapid bacterial inactivation at low exposure values, and, in some cases, strong target-dependent viral inactivation, often with lower halogenated by-product formation than chlorination, but outcomes are highly sensitive to mixing, particulate shielding, and early-time oxidant consumption. Comparative analysis shows that on-site blending remains the only widely validated municipal-scale approach, while microreactors and reactive separation offer higher attainable strengths at the expense of scale-up and operational complexity, and electrochemical routes remain constrained by low titers and limited dynamic response. By linking disinfection performance to production logistics, safety, and control requirements, and environmental acceptability, this review provides an exposure-anchored framework for technology selection and identifies priority research needs for advancing PFA toward robust, scalable, and regulation-ready deployment in wastewater and CSO disinfection.

Carbon capture from sewage-derived biogas could offset greenhouse gas emissions from biogas production and other waste management practices in Canada.

This study compares integrated thermal hydrolysis-anaerobic digestion (THP-AD) with the IntensiCarb (TM) (IC) vacuum-enhanced AD (IC-AD) of mixed primary and secondary sludges under identical organic loading rates (OLR) of 8-8.7 kgCOD/m(3)& centerdot;d and solids retention times (SRT) of 18-20 d. IC-AD achieved a stable methane yield of 0.22 L-CH4/gCOD(fed) (55% COD destruction), while THP-AD produced < 0.1 L-CH4/gCOD(fed) and failed due to the toxicity of high ammonia (>3.3 gN/L) and propionate (>2.8 g/L) accumulation when using both acclimatized and unacclimatized THP biomass. The IC-AD reduced digester ammonia by 49%-56% via ex-situ vacuum application whereas in THP-AD, ammonia accumulated. Off-line batch tests showed acetate, butyrate and propionate degradation rates were 2.3-2.7 times higher in IC-AD than THP-AD. Ammonia inhibition batch tests showed methane production rate reductions of 27% in IC and 58% in THP at 2-4 g-ammonia/L, highlighting the higher inhibition threshold of the IC biomass. The microbial communities showed distinct differences: IC-AD was dominated by Firmicutes with enriched Petrimonas and Syntrophomonas, while THP-AD was dominated by Bacteroidota with enriched Corynebacterium and Syntrophomonas. Methanogen counts were 6.2 times higher in the IC-AD due to the presence of high-growth-rate acetoclastic Methanosarcinaceae while hydrogenotrophic Methanobacteriaceae were the most abundant methanogen in the THP-AD. In offline tests with acetate, the biomass-specific methane production rate in the IC-AD was 8.4 times higher, suggesting that the acetoclastic pathway associated with Methanosarcinaceae provided superior process performance to the hydrogenotrophic Methanobacteriaceae pathway. Overall, when operated at similar loadings IC-AD outperformed THP-AD, achieving stable methane production and enriched beneficial microbial communities while also recovering ammonia as an additional value-added product.

Greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) naturally occur in the atmosphere; however, emissions from anthropogenic activities have driven the rapid increase in global temperatures, with wastewater treatment plants (WWTPs) contributing nearly 5% of global non-CO2 GHG emissions. Plant-wide monitoring campaigns remain resource-intensive and often fail to capture temporal variability, whereas plant-wide models offer an effective and representative means of quantifying CH4 emissions across treatment processes. Since previous plant-wide models have poorly evaluated fugitive CH4 emissions, this study presents a novel plant-wide modelling framework developed using operational data from a full-scale WWTP to quantify fugitive CH4 emissions. Major contributors, including anaerobic digesters, biosolids handling, and bioreactors, were identified, while potential sources such as sewers, fermenters, and clarifiers were evaluated. Emission factors (EFs) were consistent with full-scale monitoring studies and were 70% higher than the current Canadian EF for biological nutrient removal (BNR) plants (0.0036 kg CH4/kg BOD) and 33% lower than that of the Intergovernmental Panel on Climate Change (IPCC; 0.018 kg CH4/kg BOD). Monte Carlo simulations revealed uncertainties ranging from 39.1% to 46.1% in fugitive emissions and EFs across multiple scenarios. The sensitivity analyses revealed that the influent wastewater and anaerobic digesters exerted the greatest influence on plant-wide emissions. Overall, the results demonstrate that plant-wide models provide an effective alternative to intensive monitoring campaigns while supporting targeted mitigation strategies.

The presence of 41 per- and polyfluorinated alkyl substances (PFAS) was investigated in raw and finished drinking water and in influent and effluent wastewater sampled from facilities in the Great Lakes Basin region of Southern Ontario, Canada (September-November 2023). Based on US Environmental Protection Agency Method 1633A, the method developed for analysis of these species demonstrates high sensitivity and recovery with limits of quantitation that range between 0.075 ng L-1 and 3.0 ng L-1. Linear chain PFAS with carboxylic acid and sulfonic acid groups were detected in finished water from all drinking water treatment plants (n = 6). Wastewater effluents (n = 2) had PFAS concentrations approximately 1 order of magnitude higher than those in finished drinking water samples and included several fluorotelomers and ether-linked species. Across all sites, 13 of the 41 PFAS were detected in drinking water and 21 in wastewater. Average sum of 25 PFAS in finished drinking water ranged between 8.69 and 14.0 ng L-1, well below Health Canada's objective of 30 ng L-1. These results highlight the persistence of PFAS across treatment systems and suggest a potential feedback loop where wastewater effluents reintroduce PFAS into surface waters used as drinking water sources.

Ozone is a powerful oxidant capable of degrading a wide range of contaminants, but its low mass transfer with conventional devices poses challenges for effective application in advanced oxidation processes and highly reactive matrices such as wastewater. This study evaluates the performance of MITO3X (R) technology, a system designed to enhance ozone mass transfer and radical yields therefore optimizing the reactivity between pollutants and oxidative species with almost instantaneous contact time (<1 s). This research investigates MITO3X (R) efficacy in degrading seven pollutants including Methylene blue (MB), 4-chlorobenzoic acid (pCBA), Caffeine (Caf), Acetaminophen (APAP), Ciprofloxacin (Cipro), Carbamazepine (CBZ), and Sulfamethoxazole (SMZ) as a function of water quality (high, medium, and low). Here, 'high' denotes dechlorinated, GAC-filtered water without added scavengers; 'medium' includes 5 mg. L--(1) nitrite (NaNO2); and 'low' includes both 5 mg. L--(1) nitrite and 10 mg. L--(1) TOC (as methanol) thereby reflecting progressively stronger radical/ozone-scavenging matrices. Results indicate that ozonation efficiency, measured as (C-0-C)/C-0*100, reached up to 85 +/- 5 % under high water quality, and approximately 65 % in medium quality, and 45 % in low quality, highlighting the impact of scavengers on advanced oxidation performance. A multivariate analysis examined the effects of MITO3X (R) operational parameters, including impeller speed, water flow rate, and ozone capacity, on pollutant removal. The mass of ozone injected (e.g., controlled via adjustment of ozone capacity of the ozone generator) was dominant, with mixing and water quality also contributing through their interactions. The results defined operating conditions that maximize removal under nearly zero (e.g., < 1 s) contact time and highlighted the potential of MITO3X (R) as a compact, efficient ozonation option for tertiary wastewater treatment and micropollutant control.

Biodegradable plastics (also known as bioplastics), with their potential to act as both a solid-phase carbon source (SCSs) and a biofilm carrier, provide a promising opportunity for sustainable wastewater denitrification. If effectively engineered, these materials could replace conventional liquid carbon sources, representing a significant advancement in wastewater treatment sustainability. However, their effectiveness depends on a more comprehensive understanding of their dissolution behavior, a topic that is currently underexplored. This study investigates the dissolution mechanisms and kinetics of polycaprolactone (PCL) under various conditions, assessing the impact of variables such as temperature, PCL mass (surface area), solvent type (tap water vs. filtered secondary effluent wastewater), and bead reuse on the release of soluble COD (SCOD) through a series of batch experiments. To capture the time-dependent behavior of SCOD release while considering temperature and bead mass dependencies, a mathematical dissolution model was developed, parameterized, and validated using experimental data by modifying the Noyes-Whitney equation. Building on the kinetic insights from batch studies, a continuous-flow experiment was then performed to examine the influence of hydraulic retention time (HRT) on cumulative carbon release. Shorter HRTs increased washout and reduced SCOD accumulation, whereas longer HRTs allowed greater buildup of dissolved carbon and resulted in higher steady-state SCOD concentrations. The findings highlight the importance of operating conditions as well as material properties in influencing the dissolution of PCL.

Contaminants of emerging concern (CEC) pose significant challenges to environmental and human health. The development of the wastewater reuse sector, coupled with progressively stringent regulations, needs innovative systems that integrate advanced treatment processes with in-situ and real-time monitoring of CEC. This study investigates the use of a tryptophan-like fluorescence sensor for real-time and online monitoring of CEC within a pilot plant employing O3-based advanced oxidation processes (AOPs). Two tertiary wastewater effluents (WW-1 and WW-2) were tested, placing the pilot system downstream of two different wastewater treatment plants (WWTPs). Priority substances and micropollutants detected in the investigated water matrixes such as pharmaceuticals, per- and polyfluoroalkyl substances (PFAS) were selected as targeted compounds in this study. Fluorescence degradation was detected in real-time by the sensor, showing a high capability to detect fast changes in water quality induced by oxidation. Furthermore, the real-time fluorescence showed better sensitivity than lab-scale fluorescence in detecting the fast action of hydroxyl radicals (·OH) during the O3/H2O2 process, highlighting the importance of online monitoring. Selected CEC were degraded by AOPs with different percentages of removal efficiency (RE) (0%<RE<100% in WW-1 and 15%<RE<90% in WW-2) depending on oxidant doses and the reactivity of compounds with O3 and ·OH. Fluorescence data by online sensor enabled accurate prediction of the removal of a wide spectrum of CEC during O3 and O3/H2O2 processes (R2≥0.93). Furthermore, real-time fluorescence data were successfully used to predict observed pseudo-first-order rate constants of CEC with O3 or O3/H2O2. Obtained results suggest that real-time fluorescence monitoring is an excellent tool to control CEC removal during O3-based AOPs and monitor the transferred ozone in wastewater (R2≥0.94), contributing to the optimization of reagent dose, energy and costs.

This study investigated the applicability of a protein-like fluorescence sensor for wastewater quality monitoring. Several wastewater matrices, including raw, primary, secondary and tertiary effluents from three different wastewater treatment plants were used. Furthermore, the sensor was tested for the monitoring of quaternary effluent in a pilot scale plant installed downstream of a water reuse facility. The pilot plant involved advanced oxidation processes (AOPs) and granular activated carbon (GAC) adsorption. Corrections on excitation/emission matrices (EEMs), including Inner Filter Effect (IFE) and scattering, showed no effect on linear correlation (R2=0.99) between sensor measurement and either raw or corrected benchtop protein-like fluorescence data, suggesting that for this application the signal from the sensor might be interpreted without the need for further adjustments. Furthermore, the use of quenched, diluted and filtered samples did not affect such correlations. Overall, the fluorescence sensor showed a very high capability to monitor a wide range of wastewater matrices, including raw, primary, secondary, tertiary, and quaternary effluents, providing fast information on the efficiency of the processes. The protein-like fluorescence monitoring by the real-time sensor was validated online through 9 days of 24-hour continuous monitoring of tertiary wastewater effluents. The employed fluorescence sensor was validated for monitoring the removal of contaminants of emerging concern (CEC), including a wide range of pharmaceuticals, in different AOP systems (ozone and UV based). In view of the results reported in this study, possible environmental implications for the reduction of the carbon footprint have emerged: the use of fluorescence sensors may contribute to the optimization of processes and the reduction of secondary pollution.

IntensiCarb® represents a vacuum-driven intensification technology with applicability in fermentation or anaerobic digestion. Implementation of this technology in fermentation facilitates a 50% reduction in process volume while concurrently enhancing the yield of volatile fatty acids (VFAs) for advantageous utilization such as carbon source for enhanced biological phosphorus removal (EBPR). An analysis was conducted to assess the process performance and life-cycle costs of IntensiCarb in comparison to chemical addition and conventional fermentation methodologies for Total Phosphorus (TP) removal. Experimental outcomes pertaining to vacuum-assisted process intensification informed the process performance analysis. Greenhouse gas (GHG) emissions were estimated and compared between alternatives. The findings of the assessment indicate that IntensiCarb is a competitive option among alternatives that reduce effluent TP through EBPR. TP removal via FeCl3 chemical addition was the most economically advantageous alternative based on current economics and estimated life-cycle cost. PRACTITIONER POINTS: Novel vacuum-assisted fermentation, IntensiCarb®, was evaluated against other alternatives for process and cost comparisons in enhanced biological phosphorus removal facilities. IntensiCarb® has a similar life-cycle cost with conventional fermentation and MicroC® 2000 alternatives for achieving lower effluent total phosphorus. The evaluation suggests this technology may be economically viable at full-scale for enhanced biological phosphorus removal facilities. FeCl3 addition and IntensiCarb had the highest greenhouse gas emission estimates relative to conventional fermentation or using MicroC® 2000.

Electrochemical methods show promise for wastewater treatment by removing pollutants, recovering nutrients, and generating hydrogen. To scale this technology, durable and affordable electrode materials are needed. This study evaluates aluminum 6061-T6, titanium grade II, ductile iron, and magnesium to understand their performance in promoting precipitation, gas production, and treating wastewater under several conditions. Electrodes were tested with ammonia-, magnesium-, and phosphate-spiked wastewater samples with induced precipitation at concentrations of 0.033 mol/L and 0.0033 mol/L; the liquid, gas, and precipitation phases were characterized. The results showed up to 35% reduction in ammonia, total phosphate recovery, and up to 70% reduction in magnesium. The cell generates hydrogen with purity levels of 95.6%, 96.1%, 87.9%, and 93.5% when utilizing iron, aluminum, titanium, and magnesium electrodes, respectively. The analyses of precipitants showed formation of vivianite crystals from iron, struvite precipitation from magnesium, and berlinite from aluminum. Overall, these results hold substantial promise for hydrogen generation from wastewater and potential for nutrient recovery and treatment.

Ex-situ vacuum-enhanced anaerobic digestion (IntensiCarb-AD) of primary and thickened waste activated sludge (PS/TWAS) was tested at an organic loading rate (OLR) of 11.0-11.3 kg COD/m(3)-d. IC-AD reactors with similar solids retention times (SRT = 20 d) and OLR, were operated at hydraulic retention times (HRT) of 5 days (IF defined as SRT/HRT of 4) and 3.33 days (IF6). IF4 had a higher steady-state methane yield of 0.214 +/- 0.009 L-CH4/gCOD(fed) compared to 0.148 +/- 0.029 L-CH4/gCOD(fed) in IF6. COD removals of 53.5 %+/- 2.25 % were obtained with IF4 but fluctuated with IF6 (37.0 %+/- 7.25 %). Both IF4 and IF6 processed 6 times the OLR of a conventional AD with comparable volatile solids reduction efficiency. The relative instability in IF6 was linked to a greater reduction in microbial activity due to longer vacuum application and higher propionate concentrations (>2.20 g/L), which affected the performance of hydrogenotrophic methanogens. Methanosarcinaceae and Methanobacteriaceae populations were 10.8 % and 35.2 % more abundant in IF4 than in IF6, respectively, corroborating the significantly higher methane yields observed in IF4 compared with IF6. Ammonia recovery efficiencies of 52.0 % and 49.1 % were observed in IF4 and IF6 respectively. Batch ammonia toxicity tests indicated a higher inhibitory constant (K-i) for IC-AD (5.60-5.70 gN/L) compared to conventional AD (1.90 gN/L). Acetate degradation was effective even with ammonia and propionate concentrations as high as 2,000 mg/L and 4,000 mg/L, respectively.