Upflow Anaerobic Sludge Blanket Research Articles

Removal of micropollutants by UASB reactor and post-treatment by Fenton and photo-Fenton: Matrix effect and toxicity responses

Literature is scarce on the performance of Fenton-based processes as post-treatment of municipal wastewater treated by upflow anaerobic sludge blanket (UASB) reactor. This study aims to perform Fenton and photo-Fenton from UASB influent and effluent matrices to remove micropollutants (MPs) models: atrazine (ATZ), rifampicin (RIF), and 17α-ethynylestradiol (EE2). A UASB reactor at bench-scale (14 L) was operated with these MPs, and the AOPs experiments at bench-scale were performed on a conventional photochemical reactor (1 L). A high-pressure vapor mercury lamp was used for photo-Fenton process (UVA-Vis) as a radiation source. Microcrustacean Daphnia magna (acute toxicity) and seeds of Lactuca sativa (phytotoxicity) were indicator organisms for toxicity monitoring. The UASB reactor showed stability removing 90% of the mean chemical oxygen demand, and removal efficiencies for ATZ, RIF, and EE2 were 16.5%, 45.9%, and 15.7%, respectively. A matrix effect was noted regarding the application of both Fenton and photo-Fenton in UASB influent and effluent to remove MPs and toxicity responses. The pesticide ATZ was the most recalcitrant compound, yet the processes carried out from UASB effluent achieved removal >99.99%. The post-treatment of the UASB reactor by photo-Fenton removed acute toxicity in D. magna for all treatment times. However, only the photo-Fenton conducted for 90 min did not result in a phytotoxic effect in L. sativa.

Performance evaluation of hybrid upflow anaerobic sludge blanket reactors with different inert media for sewage treatment

In this study, three HUASB reactors with different inert media viz. sea shells (R1), polyvinyl alcohol (PVA) gel beads (R2) and coconut fiber (R3), were simultaneously investigated in continuous mode at an ambient temperature ranging from 33 °C to 41 °C for six months. The reactors were employed with varying hydraulic retention times (starting from 6 h and reduced to 2 h) and organic loading rates (0.5–6.0 kg.COD.m−3.day−1) for sewage treatment. Sludge bed samples from each reactor were collected at the end of the process, and particle size distribution was determined using ocular micrometry, as well as the number of microorganisms present per ml using the neubauer chamber. According to the chemical and microbiological analysis, along with an overall assessment, it was found that the HUASB reactor with coconut fiber inert media has proved superior in its performance compared to the HUASB reactor with PVA gel beads and sea shells.

Biohydrogen from anaerobic treatment of brewery wastewaters: A preliminary study

Hydrogen gas is considered the energy of the future because it is renewable, clean, and does not generate greenhouse gas emissions. Among the existing processes for producing hydrogen, it is found biological production from residual wastewater with a high content of carbohydrates treated with an anaerobic process. The utilization of wastewater for hydrogen production is considered an economical alternative because the raw material is abundant and easy to access. In this sense, the present study assessed the hydrogen production from the wastewater of the beer industry treated by Up-flow Anaerobic Sludge Blanket Reactors (UASB). Then, it was applied a thermal shock (90 °C/15 min) to the inoculum, with a previous dark fermentation treatment. The results revealed that with an organic volumetric load of 9.1 gDQO/L.D., pH of 5.5, and a hydraulic retention time (HRT) of 2 h, the maximum percentage of hydrogen gas was 21 % which corresponds to a yield of hydrogen of 6.50 mMolH2/l. According to the results was found that the initial compound of wastewater influenced the stability and continuity of hydrogen gas (H2). Finally, this study identified the uncommon presence of methane gas (CH4) with hydrogen gas, despite keeping pH values nearby to 5.5, and has applied a thermal shock to the inoculum.

Two-stage anaerobic digestion system for biotransformation of an azo dye in the presence of sulfate: Minimizing competition for reducing equivalents

Anaerobic treatment of azo dyes is particularly challenging in the case of wastewaters containing sulfate. We studied the use of multiple stage anaerobic system to minimize the impacts of sulfidogenesis and methanogenesis on the decolorization and biotransformation of an azo dye. The system was composed of a 1st-stage anaerobic structured-bed reactor (R1), designed for removal of color, followed by a 2nd-stage upflow anaerobic sludge blanket reactor (R2) intended for organic matter and sulfate removals. Results showed that near complete decolorization was achieved in R1 when a dye loading rate of 222 ± 9 mg L−1 d−1 was applied. Sulfidogenic activity in this reactor was negligible due to the low pH and did not impair reductive decolorization. After increasing dye load, decolorization efficiency in R1 decreased, but gradually recovered in the following weeks. R2 kept decolorization around 90% even when R1 presented decreased efficiencies, keeping up with overall performance. Residual organic matter in the system's final effluent consisted of aromatic amines and other dye fragments recalcitrant to anaerobic digestion (AD), whose concentrations further increased after treatment in R2. The average volumetric methane production rate achieved in R2 was 472 ± 111 mL L−1 d−1. The two-stage AD system provided enhanced removals of color, organic matter and sulfate by eliminating issues related to the competition for reducing equivalents.

Evaluation of UASB effluent post-treatment in pilot-scale by microalgae HRP and macrophytes pond for nutrient recovery

The partially treated effluents discharge into water resources impacts water quality and living beings. These effluents contain nutrients such as phosphorus and nitrogen, which can promote the eutrophication of water sources and, consequently, the development of microalgae and macrophytes at levels above the environmental balance. However, the control of these photosynthetic beings can reduce and even prevent the eutrophication. The present work aims to evaluate the removal and recovery of nutrients from effluent treatment through high rate microalgae ponds (AP) and treatment ponds with the presence of macrophytes (MP) in two steps. In step I, the ponds were operated individually (parallel period), in step II they were operated in sequence, where the effluent from the AP to directed to the MP (series period). On the two steps, the performance evaluation regarding the climatic conditions to divide into two periods: warm (summer and spring) and cold (autumn and winter) and the HDT of 2.2, 3.3, and 4.1 days in each pond to evaluate the removal and recovery of nutrients from Algae Pond (AP) and Macrophyte Pond (MP), cultivation ponds fed with sanitary effluent pretreated by an Upflow Anaerobic Sludge Blanket reactor (UASB). The main results for nitrogen and phosphorus removal and recovery were for 4.1 days Hydraulic Detention Time in the warm period for the series system, reaching values below 1.0 mg/L for phosphorus and close to zero for ammonia nitrogen; non-detection by analysis method. For nutrient recovery, the maximum values found were 0.12 g/m2·day for phosphorus and 0.79 g/m2·day for nitrogen.

Importance of low-abundance microbial species in response to disturbances in wastewater bioreactors

This study demonstrates the importance of low-abundance species in maintaining biosystem stability in response to a changing reactor operation condition. Initiation and termination of effluent recirculation were applied as the operational disturbance factors in two upflow anaerobic sludge blanket (UASB) reactors treating high-strength wastewater, respectively. The microbial growth rates during the community evolution were calculated based on the non-steady-state mass balance model. Community evolution studies showed that directly following the initiation/termination of effluent recirculation, the microbial communities reached the highest diversity. The net growth rates of individual microbes during community evolution illustrated that low-abundance species played a critical role in response to the disturbance induced by initiating or discontinuing effluent recirculation. This study highlights the importance of the response of low-abundance species in maintaining biosystem stability when a disturbance is applied to a wastewater bioreactor.

Effect of formic acid inflow on microbial properties of the anaerobic granular sludge in a UASB reactor

In the production of natural rubber, formate or acetate is added to the latex solution to coagulate the rubber; therefore, the wastewater contains high concentrations of organic acids, requiring the application of anaerobic treatment technology. In this study, a two-phase continuous flow experiment using a laboratory-scale upflow anaerobic sludge blanket (UASB) was conducted to investigate the influence of formate inflow on the microbial and physical characteristics of the retained granular sludge. In phase 1, acetate-based wastewater was used as feed, while in phase 2, formate-based wastewater was used as feed. In phase 1, the UASB exhibited high COD removal efficiency (97.2%); in addition, the retained sludge showed increased methane production from acetate and proliferation of acetate-utilizing Methanosaeta species. In phase 2, the UASB performed as well as phase 1, with 98.2% COD removal efficiency. Microbial community structure analysis confirmed that relatives of Methanobacterium formicicum present in the retained sludge were responsible for the degradation of formate in phase 2. However, decreased diameter and slight deterioration of granular sludge settleability were observed. In conclusion, formate inflow has low risk of interference with the process performance of the UASB, but it has negative effects on the physical properties of the granular sludge.

Hydrothermal treatment enhances the removal of antibiotic resistance genes, dewatering, and biogas production in antibiotic fermentation residues

Antibiotics and antibiotic resistance genes (ARGs) are enriched in antibiotic fermentation residues (AFRs). In this study, we investigated the effect of hydrothermal treatment on dewatering, biogas production, and removal of ARGs in the penicillin fermentation residue (PFR). Solid, 120 µm particles in the PFR were disintegrated to 30 – 40 µm after 140 – 180 °C hydrothermal range. Of extracellular polymeric substance, 79.8 ± 0.4% was decomposed to release 82.2 ± 0.6% of bound water at 180 °C. The effective solid-liquid separation was achieved only after a hydrothermal treatment of 180 °C. More than 75% of organic matter in the filtrate was transformed into biogas by the upflow anaerobic sludge blanket (UASB). The absolute abundance of 16 S rRNA and ARGs decreased by 2.4 – 5.2 logs after hydrothermal treatment. The ratio of extracellular ARGs (eARGs) to total ARGs increased at 80 °C and decreased at higher temperature (>120 °C). The absolute abundance of ARGs increased by 0.7 – 1.6 logs in anaerobic digestion, and the relative abundances of ARGs based on 16 S rRNA plummeted by 3 logs. Most (98.7 ± 0.4%) ARGs were distributed in suspended solids and were removed by membrane filtration. Hydrothermal treatment demonstrated broad applicability to 10 varieties of AFRs.

Environmental performance of an integrated water supply and wastewater system through life cycle assessment — A Brazilian case study

The objective of this study was to evaluate the environmental performance of an integrated water supply and wastewater system that employs a system of ponds at the wastewater treatment system. Additionally, this study aimed to understand the contribution of each stage of the system to the analyzed impact categories, and to evaluate alternative scenarios that consider the reduction of water losses in distribution, as well as the operation of an upflow anaerobic sludge blanket (UASB) reactor in the wastewater treatment plant (WWTP). The evaluation was performed through life cycle assessment (LCA) that considered the stages of water withdrawal, treatment, and distribution along with wastewater collection and treatment. The system was modeled in the OpenLCA software using the Ecoinvent 3.7.1 database. Environmental impacts were assessed using the ReCiPe method and cumulative energy demand. The results show that the water withdrawal stage is the potential source of the greatest environmental impacts. There are exceptions in the categories of climate change and photochemical oxidant formation, which are most impacted by the WWTP. Analysis of alternative scenarios revealed that the decrease in water loss rates during distribution contribute to a linear reduction in potential environmental impacts of the analyzed categories. The operation of a UASB reactor in the WWTP leads to a reduction in impacts on the categories of climate change (41.4%) and formation of photochemical oxidants (11.6%), and to increases in impacts on the other categories analyzed. The data presented provide important information for the improvement of public policies aimed at sanitation in developing countries.

Metagenomic insights into direct interspecies electron transfer and quorum sensing in blackwater anaerobic digestion reactors supplemented with granular activated carbon

The addition of granular activated carbon (GAC) enhanced the performance of up-flow anaerobic sludge blanket (UASB) reactor treating blackwater at 35 °C. DNA were extracted from the sludge and biofilms attached to GAC and submitted for shotgun sequencing. In addition, the acyl-homoserine lactones (AHLs) were quantified. Diverse partners for direct interspecies electron transfer (DIET) were enriched in the sludge or biofilm (GAC-biofilm) of GAC amended UASB. Pedosphaera parvula, Syntrophus aciditrophicus and Syntrophorhabus aromaticivorans were dominant syntrophs. The analysis for type IV pilus assembly genes further suggested DIET may be functioned through GAC for GAC-biofilm, while through conductive pili for sludge aggregates. AHLs quantification and the analysis for quorum sensing (QS) related genes indicated higher QS activity at the population level was induced by GAC. Overall, the work illustrated the different DIET patterns, and suggested that QS played an important role in controlling the performance in GAC amended USAB.

Modeling and optimization of an upflow anaerobic sludge blanket (UASB) system treating blackwaters

In the present work, a novel mathematical dynamic model describing the upflow anaerobic sludge blanket (UASB) has been developed. The model incorporates both the biological processes and the transport of sludge particles specifically related to the UASB treatment of blackwater. The processes occurring in the reactor are modeled as a sequence of two completely-mixed reactive tanks, one representing the sludge bed where most solids concentrate and the other representing a less solid-concentrated liquid volume. Solids from the sludge bed are assumed to be dragged to the upper zone of the reactor by the methane gas produced. The time variation of the sludge bed volume is included by assuming a constant sludge density. The model is calibrated against published data obtained from a stable operation of a lab-scale UASB system treating at different organic loading rates blackwater collected from real vacuum toilets. Good model prediction compatibility with the measurements of emitted biogas and methane gas flow rates, effluent COD, volatile fatty acids, pH and sludge bed volume was revealed. Furthermore, the model was successfully validated against another independent set of data from a UASB reactor treating a more diluted type of blackwater collected from conventional toilets. A scenario analysis performed using such a validated model reveals higher methane production yield but also higher effluent COD concentration at increasing organic loading rates and sludge bed volumes. It is found that longer HRTs can improve COD removal efficiency and methane production in blackwater treatment processes.

Recent Developments in Biological Processing Technology for Palm Oil Mill Effluent Treatment-A Review.

Simple SummaryPalm oil mill effluent (POME) requires treatment prior to discharge to the environment. Biological processing technology is highly preferable due to its advantages of environmentally friendliness, cost effectiveness, and practicality. These methods utilized various designs and modifications of bioreactors fostering effective fermentation technology in the presence of fungi, bacteria, microalgae, and a consortium of microorganisms. This review highlights the recent biological processing technology for POME treatment as a resource utilization.POME is the most voluminous waste generated from palm oil milling activities. The discharge of POME into the environment without any treatment processing could inflict an undesirable hazard to humans and the environment due to its high amount of toxins, organic, and inorganic materials. The treatment of POME prior to discharge into the environment is utmost required to protect the liability for human health and the environment. Biological treatments are preferable due to eco-friendly attributes that are technically and economically feasible. The goal of this review article is to highlight the current state of development in the biological processing technologies for POME treatment. These biological processing technologies are conducted in the presence of fungi, bacteria, microalgae, and a consortium of microorganisms. Numerous microbes are listed to identify the most efficient strain by monitoring the BOD, COD, working volume of the reactor, and treatment time. The most effective processing technology for POME treatment uses an upflow anaerobic sludge blanket reactor with the COD value of 99%, hydraulic retention time of 7.2 days, and a working volume of 4.7 litres. Biological processing technologies are mooted as an efficient and sustainable management practice of POME waste.

Single step production of activated carbon from microalgae cultivated with urban wastewater

The production of activated carbon using as precursor a microalgae biomass produced in a wastewater treatment plant, consisting of an Upflow Anaerobic Sludge Blanket (UASB) reactor, followed by high-rate aerobic ponds, was studied. The harvest of microalgae biomass was carried out through coagulation with Tanfloc®, flocculation and settling. Activated carbon (AC) production was tested at 650 °C and 800 °C, with carbonization and activation performed in a single step, by the physical method with water vapor in different proportions of water mass relative to the sample mass. The specific surface area ranged from 10 to 177 m2·g−1 in samples produced at 650 °C and from 602 to 630 m2·g−1 in the ones produced at 800 °C. It is concluded that the harvested microalgae biomass can be used as a precursor of activated carbon. The best condition tested for the production of AC was carbonization at 800 °C and activation with water vapor in the ratio of 4 gwater/gsample. The results prove that the process of carbonization and physical activation can be done with water vapor in a single step and that activated carbons obtained under the highest temperature (>800 °C) are predominantly micro and mesoporous, with a predominantly aromatic structure.

EXPERIMENTAL ASSESSMENT OF THE AGRICULTURAL WASTES ENERGY POTENTIAL FROM SINALOA, MEXICO

ABSTRACT: In Sinaloa, agricultural and livestock practices are extensive but proportionally generate organic wastes that subsequently produce greenhouse gases and negatively impact water bodies. In this research, a laboratory-scale up-flow anaerobic reactor was configured and evaluated to treat combined agricultural and livestock wastes. Subsequently, the quality and yield of the biogas were used to make an energetic and economic comparison with Liquefied Petroleum Gas (LPG). The results were also projected for the energy needs of the pilot community from which the waste was obtained. The reactor used was a 2.4 L reactor operated continuously at 45±2 °C and HRT of 7.2 d, with an organic load of 15000 mg/L. Carbon/nitrogen ratios of 25:1 and 32:1 were evaluated. With the 25:1 ratio, 1650 mL/d of biogas were obtained. With this ratio, greater stability was observed, and a higher proportion of methane. On average, 70% was methane (once stabilization was reached), converting it into biofuel. The projection made for Sinaloa is that 59.65 m3 of methane could be obtained per year, which is equivalent to $2.25 million per year. All the information generated serves as a precedent for large-scale technical and economic feasibility studies. All these studies will allow the integral use of agricultural industry waste, mainly in rural communities, which will also improve the population's quality of life. Keywords: methane yield, biofuel, agricultural wastes management, methane, Upflow Anaerobic Sludge Blanket, carbon/nitrogen ratio

Assessment of Levonorgestrel Leaching in a Landfill and Its Effects on Placental Cell Lines and Sperm Cells

The Buenavista landfill is located east of the city of Medellín, but it has a slope steeper than 30% and is less than 600 m away from the Piedras River, possibly influencing the quality of the drinking water in the city. Many complex residues are disposed of in this landfill, including pharmaceuticals and personal care products (PPCPs) such as levonorgestrel (LNG), which may reach water bodies via runoff and leaching. We assessed the levels of LNG in the effluent of an upflow anaerobic sludge blanket (UASB) reactor from the Buenavista landfill by uHPLC–DAD, as well as the endocrine disruptor effect of LNG on placental cell lines (BeWo) and human sperm cells. Additionally, the potential leaching of LNG was assayed under laboratory conditions using soil layers that were sampled from the Buenavista landfill. LNG was detected at levels of 315 μg·L−1 in the effluents of the UASB reactor. Thus, the UASB reactor is not an efficient treatment method for the removal of recalcitrant pollutants. Additionally, we found that a layer of soil used as a cover material may adsorb more than 90% of LNG pollutants, but small amounts may still be leached, which means that a cover material is not a strong enough barrier to fully prevent the leaching of LNG. Finally, our results show that the leachate fraction decreased the levels of β-human chorionic gonadotropin, but not sperm motility or viability. Thus, leached LNG could trigger reproduction disorders, but further studies should be carried out to investigate its potential effects in more detail.

Effects of temperature and HRT on biogas production in moving and fixed bed of a novel upflow anaerobic hybrid (UAHB) reactor

ABSTRACT The upflow anaerobic hybrid (UAHB) reactor combines the advantages of a upflow anaerobic sludge blanket (UASB-type) reactor and an anaerobic filter in a single compartment. A novel configuration of the UAHB reactor, composed of two three-phase separators (3PHS), was proposed to evaluate the biogas production in the moving and fixed bed in the treatment of synthetic sewage at a temperature range of 14–21 °C and hydraulic retention time (HRT) of 12, 10 and 8 h. The bench-scale reactor was operated in three different phases with organic loading rate (VOLR) of 0.6 (0.3–0.7), 0.7 ± 0.2, and 1.1 ± 0.1 kg COD m−3 d−1, respectively, for 225 days. The average removal efficiency of chemical oxygen demand (CODt) was 78 (42–89)%, and the total biogas yield was 3090 (1704–4782) mL d−1, with 66% of the lower 3PHS (moving bed) and 34% of the upper 3PHS (fixed bed). However, no significant difference was observed between the biogas yield on the 3PHS (p-value = 0.5048), thus confirming the influence of temperature in the biogas production. The average percentage of methane was 76 (60–82)% for both beds, and the filter media increased the production by 21%. Thus, it can be concluded that the fixed bed suppressed the instability of the moving bed regarding the biogas production and contributed to the final quality of the effluent.

Psychrophilic treatment of municipal wastewater with a combined UASB/ASD system, and perspectives for improving urban WWTP sustainability

According to new paradigms of urban wastewater management, energy savings and resources and energy recovery from sewage will assume an ever-increasing importance. Anaerobic processes, aside from being more energy efficient than conventional aerobic ones, are particularly suited to recover embedded organic energy, improving the overall energy balance of treatment processes, however, their performance is limited by low temperatures and slower kinetics. In this study, a pilot Upflow Anaerobic Sludge Blanket (UASB) reactor was operated to treat municipal wastewater at low temperature regime (16.5–18.5 °C) for 22 weeks, both as standalone process and combined with a sidestream anaerobic sludge digester. Process performance highlighted good system robustness, as proved by stable pH and volatile fatty acid/total alkaline buffer capacity ratio, even though observed methane yield was low. Observed COD and TSS removal efficiencies were in the ranges of 60–69% and 63–73%, respectively. Methane production ranged between 0.106 and 0.132 Nm3CH4/kgCODrem. An economic assessment was carried out to evaluate the feasibility and benefits of implementing UASB pre-treatment of municipal wastewater in existing conventional facilities (activated sludge and anaerobic sludge digestion), showing that significant energy demand reduction could be achieved for both biological secondary treatment and sludge management, leading to considerable operational economies, and possible positive economic returns within a short pay-back period (3–4 yrs).

Phosphorus recovery from pig manure: Dissolution of struvite and formation of calcium phosphate granules during anaerobic digestion with calcium addition

Phosphorus is an essential but finite and scarce element, which is used extensively in pig farming. For recovering phosphorus from pig manure, we hypothesize that calcium addition during anaerobic treatment can trigger calcium phosphate granulation and enable efficient phosphorus recovery. In this study, we tested the recovery of phosphorus from pig manure by adding calcium during anaerobic treatment. Size–separated (<200 µm) pig manure was treated in two identical up-flow anaerobic sludge blanket reactors for 456 days. Calcium was supplied to one of the reactors to study calcium phosphate granulation.Calcium addition showed a positive effect on treatment stability and efficiency, increasing chemical oxygen demand and phosphorus removal. Phosphorus removal increased from 60% without calcium addition to 74% with calcium addition. The addition of calcium increased the phosphorus concentration in significantly larger particles, calcium phosphate granules, (79% >0.4 mm compared with 11% without calcium addition) in the reactor with calcium addition, which enables separation and a transport reduction of 85% for the recovered phosphorus. The main phosphorus phase in the reactor sludge bed changed from struvite to calcium phosphate with calcium addition. The Mg:P molar ratio was 0.09 with calcium addition and 0.88 without calcium addition in particles >2.5 mm. Thus, calcium addition enhances the treatment of pig manure and enables phosphate recovery as calcium phosphate granules.

Modified fractional-order model for biomass degradation in an up-flow anaerobic sludge blanket reactor at Zenein Wastewater Treatment Plant.

This paper presents a modified fractional-order model (FOM) for microorganism stimulation in an up-flow anaerobic sludge blanket (UASB) reactor treating low-strength wastewater. This study aimed to examine the famine period of methanogens due to biomass accumulation in the UASB reactor over long time periods at a constant organic loading rate (OLR). This modified model can investigate the substrate biodegradation in a UASB reactor while considering substrate diffusion into biological granules during the feast and famine periods of methanogens. The Grünwald-Letnikov numerical technique was used to indicate the effect of biomass degradation on the biogas production rate and substrate biodegradation in a UASB reactor installed at Zenein Wastewater Treatment Plant (WWTP) in Giza, Egypt. Several fractional orders were applied in the dynamic model at biomass concentrations of [Formula: see text] and [Formula: see text] in the reactor bed and blanket zones, respectively. An OLR of [Formula: see text] using the calibrated kinetic parameters at [Formula: see text] was applied to comply with the experimental outcomes. The simulation results indicate that the removal efficiency of chemical oxygen demand (COD) was maintained at approximately [Formula: see text], whereas the biogas production rate declined from [Formula: see text] in the reactor bed zone due to a decline in food to microorganism (F/M) ratio from [Formula: see text] during the sludge retention time (SRT) in the UASB reactor.

Enhancing the resistance to H2S toxicity during anaerobic digestion of low-strength wastewater through granular activated carbon (GAC) addition

Low-strength wastewater was treated using two laboratory-scale up-flow anaerobic sludge blankets (UASB) for 130 days under sulfate-reducing conditions. Granular activated carbon (GAC) was added to one of the reactors. The GAC addition increased the total chemical oxygen demand removal by 21–28% and total methane production by 32–78%. The sludge from the GAC-amended UASB showed higher specific methanogenic activities (SMA) and higher activities in the presence of H2S, indicating that the GAC addition enhanced the resistance of methanogens to H2S toxicity. Further, the microbial communities showed that the GAC addition shifted microbial communities. A robust syntrophic partnership between bacteria (i.e., Bacteroidetes_vadinHA17 and Trichococcus) and methanogens was established in the GAC-amended UASB. Sulfate-reducing bacteria (SRB) were enriched in the GAC biofilm, indicating the coexistence of competition and cooperation between SRB and methanogens. These findings provide significant insights regarding microbial community dynamics, especially SRB and methanogens, in a GAC-amended anaerobic digestion process under sulfate-reducing conditions.