Anaerobic Hybrid Reactor Research Articles

Valorization of the complex organic waste in municipal solid wastes through the combination of hydrothermal carbonization and anaerobic digestion

Municipal Solid Wastes (MSW) consist of the valorizable inorganic fraction, i.e., Refuse Derived Fuel, and the organic fraction which also can be valorized. However, the separated organic fraction, which is known as Complex Organic Waste (COW), contains traces of glass, plastics, non-ferrous metals, and stones. Thus, the aim of this work was to determine the value of the COW that comes from a MSW separation plant through the combination of Hydrothermal Carbonization (HTC) and Anaerobic Digestion (AD) for the production of biofuels. COWs were conditioned to undergo HTC for 1 h at 180 °C and 190 °C. HTC liquid was used as a substrate operating an Anaerobic Hybrid Reactor (AHR) in continuous mode with 5 gCOD/Ld at 35 ± 2 °C. The hydrochar contained on average (dry matter): (180 °C) 30.44 % carbon and 15.47 MJ/kg and (190 °C) 40.44 % carbon and 17.60 MJ/kg. The AHR removed more than 93 % (COD) reaching 0.34 LCH4 at STP/gCODrem, and no inhibitory effects were observed. The coupling of HTC with AD at low temperatures for short times turned out to be a promising alternative for the valorization of COW, i.e., it produced 10,888 MJ (94 % HTC and 6 % AD) per metric ton of COW.

Optimizing an Anaerobic Hybrid Reactor Series for Effective High-Strength Fresh Leachate Treatment and Biogas Generation

Treating high-strength fresh leachate is challenging and of great interest due to the inherent variability in its physical and chemical characteristics. This research aims to enhance the efficiency of the anaerobic hybrid reactor (AHR) series in treating high-strength fresh leachate and achieving biogas generation from fresh leachate at ambient temperatures. The AHR series used consists of two serially connected reactors termed the first anaerobic hybrid reactor (AHR-1) and the secondary anaerobic hybrid reactor (AHR-2). AHR-1 treated high-concentration fresh leachate with an organic loading rate (OLR) between 5 and 20 kgCOD/m3·d. AHR-2 treated the effluent from the first tank and removed organic matter from the system. The experiment was conducted for 210 days, showing that an OLR of 10 kgCOD/m3·d resulted in the most suitable COD removal efficiency, ranging from 82 to 91%. The most suitable OLR for biogas production was 15 kgCOD/m3·d. The AHR series proved to be an efficient system for treating high-strength fresh leachate and generating biogas, making it applicable to leachate treatment facilities at waste transfer stations and landfill sites. Treating leachate and utilizing it as a renewable energy source using the AHR series presents a practical and efficient waste management approach. High-strength leachate can be effectively treated with the AHR series; such methods may be integrated into industries treating leachates with high COD values.

Long-term temporal dynamics of total and potentially active microbiota affect the biogas quality from the anaerobic digestion of vinasse in a pilot-scale hybrid anaerobic reactor

The microbiota was evaluated through a time series of the 16S rrna gene in a pilot-scale Hybrid Anaerobic Reactor treating vinasse. The microbial composition, evenness and diversity differed between the DNA and cDNA, the latter showing a better response for %CH4 along monitoring of the microbiota. Moreover, the microbial composition and richness were distinct between the reactor's compartments, possibly contributing to the COD removal in the sludge blanket. The abundant Methanospirillum, Methanomassiliicoccaceae, Bacteroidetes-vadinHA17, Paludibacteraceae-H1, Prolixibacteraceae, Ruminococcaceae, Syntrophobacter and Desulfovibrio contributed to the %CH4, as well as the redundancy of fermentation and hydrogenotrophic and methylotrophic methanogenesis, and the evenness and diversity of potentially active microbiota and metabolisms. The microbial changes after the middle of reactor's operation required new adaptations and impacted the biogas quality, but did not affect COD removal. This study brings important knowledge about the microbial temporal dynamics, plasticity and contribution to the anaerobic digestion in pilot-scale reactors.

Residence time distribution experiments in a hybrid anaerobic blanket reactor treating real pharmaceutical wastewater

BackgroundThe phenomena of mixing is considered important due to its involvement in modelling and design of reactors. MethodsThe residence time distribution (RTD) experiments to find out the mixing characteristics were conducted in hybrid anaerobic blanket reactor (HABR) with four different OLRs of pharmaceutical wastewater using lithium chloride as tracer by means of stimulus-response technique. The mean hydraulic retention time, dispersion and Peclet number for various OLRs in HABR were determined. Significant findingsThe experimental COD removal efficiencies in HABR and the theoretical performance were found out using the axial dispersion flow model (ADFM) and plug flow model (PFM). The estimated theoretical chemical oxygen demand (COD) removal efficiencies, using the ADFM were 92.4%, 82.0%, 63.0% and 41.7% and the values respectively for PFM were 97.27%, 93.92%, 83.47% and 59.34%. The error percentage detected was less than 7% in ADFM which exhibited better flow representation in HABR. Furthermore, the value of correlation coefficient (R2 = 0.9956) between the theoretical COD removal efficiencies and experimental values confirmed the suitability of the ADF model.

A review of modified and hybrid anaerobic baffled reactors for municipal wastewater treatment with a focus on emerging contaminants

This review discusses municipal wastewater treatment using anaerobic baffled reactors (ABRs) and modified ABRs to remove C, N, P and emerging contaminants.

Enhancing biomethane production from citrus waste: An integrated approach of hydrothermal carbonization and anaerobic digestion for sustainable waste management

This study investigates the energy recovery potential of bio-oil derived from hydrothermal carbonization (HTC) of citrus waste through anaerobic digestion (AD). The bio-oil, a complex mixture containing 30-50% of the original carbon from biomass, serves as a valuable substrate for AD. Leveraging the HTC pretreatment, the hydrolysis step in AD becomes more efficient, facilitating faster degradation rates. Anaerobic digestion of the bio-oil was conducted in a high-loading hybrid anaerobic reactor. The reactor underwent stabilization using tomato liquid fraction, followed by bio-oil feeding with an applied volumetric loading of 5 g COD/L-d under mesophilic conditions. Remarkably, COD removals exceeded 90% when utilizing the tomato fraction and surpassed 80% in the bio-oil feed. Additionally, methane yield approached theoretical levels, highlighting the effectiveness of combining HTC and AD technologies. The study demonstrates that the integration of HTC and AD offers a promising alternative for the sustainable utilization of citrus industry wastes, showcasing high removal efficiencies and methane production. This approach aligns with circular economy principles, providing a pathway for efficient waste valorization and renewable energy generation.

Performance of an anaerobic biofilm reactor through the application of different operational conditions

Inadequate management of Municipal Solid Waste (MSW) and the energy crisis due to dependence on fossil fuels (carbon and hydrocarbons) are growing problems in Latin American countries such as Mexico. These problems are caused by various factors, including the lack of infrastructure and the limited development of technologies focused on addressing these areas. In Mexico, between 37.55 and 43.84 million tons of MSW are generated annually, while 5,896 PJ of fossil fuels are produced in the same period, contributing strongly to environmental pollution due to inadequate management and procurement-use processes respectively. In order to mitigate these problems, it is necessary to propose dual-purpose strategies, such as anaerobic digestion, that can help in the treatment of the organic fraction of MSW (OFMSW) and at the same time producing biogas as a renewable energy source. For these reasons, the aim of this work was to evaluate the performance of an anaerobic biofilm reactor through increases in the Organic Loading Rate (OLR) using the liquid fraction of the OFMSW as a substrate for biogas production. An anaerobic biofilm reactor called the Anaerobic Hybrid Reactor (AHR) was used to carry out this stud. The performance of the AHR in four stages applying different OLR values from 5 to 21 gCOD/L.d was analyzed. Anaerobic biofilm formation, pH, %COD and %solids removal, alkalinity, biogas production, and methane yield were evaluated. After 119 days of reactor operation, 93.45% colonization of the inverse fluidized bed, 85% total and soluble COD and removals greater than 80% for TS and VS, alkalinity less than 0.3, around 20 L of biogas per day with methane yields of 0.31 LCH4 at STP/gCODrem were obtained. The use of high OLR allows a larger volume of OFMSW liquid fraction to be treated producing a greater quantity of biogas with an excellent methane yield, thus demonstrating the high efficiency of the AHR.

A review of modified and hybrid anaerobic baffled reactors for industrial wastewater treatment

This review discusses high-strength wastewater treatment using anaerobic baffled reactors (ABRs) and modified ABRs. The research findings and applications of ABRs in treating various types of high strength wastewater generated from food companies, livestock, and industries were summarized and reported. Measurement parameters affecting the performance of ABRs are briefly discussed. The state-of-the-art laboratory studies are compiled and critically reviewed. Critical challenges and suggestions for future investigation are also addressed.

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.

Efficiencies of anaerobic hybrid and UASB reactors to alleviate the adverse effect of elevated salinity in wastewater

AbstractBACKGROUNDUntreated high‐strength salinity wastewaters pose a serious threat to the environment. Anaerobic treatment is an effective process with double advantages of waste stabilization and energy production. However, high organic compound and sodium toxicity in high‐salinity wastewaters adversely affect the performance of anaerobic treatment. In this study, anaerobic hybrid (AH) and upflow anaerobic sludge blanket (UASB) reactors were investigated for their efficiencies to alleviate the negative effects of high‐salinity wastewater.RESULTSDouble increases in the NaCl concentration drastically deteriorated the performances of both reactors. The activities of acetoclastic methanogens (ACM) and hydrogenotrophic methanogens (HTM) in both reactors decreased to 22–28% and 36–40% compared to the previous period, respectively. However, the methanogen population (Methanosarcinales and Methanobacteriales) was not affected negatively. The AH reactor exhibited excellent performance during the recovery and restart periods, which only required 7 days to complete the recovery period. Furthermore, during the restart period, the AH reactor showed high chemical oxygen demand (COD) removal efficiency, methane (CH4) production and yield as ≈90%, 2600 mL day−1 and 0.30 m3 CH4 kg−1 CODremoved, respectively. The rate of biomass washout from the AH reactor also was lower compared to the UASB reactor. The concentration of attached biomass in the packed zone of the AH reactor gradually increased indicating the growth of an active microbial biofilm.CONCLUSIONThe excellent performance of the AH reactor was presumably a result of its packed zone configuration which provided the supporting media to entrap smaller microbial aggregates, reduce biomass washout and support the growth of active biofilm. © 2021 Society of Chemical Industry (SCI).

Recovery of methane dissolved in the effluent of a novel upflow anaerobic hybrid reactor (UAHB) submitted to temperature variation

ABSTRACT Recent studies point out losses of 30–40% of the produced methane in the effluent of anaerobic reactors treating sewage, reducing the renewable energy potential and the environmental footprint. A novel bench-scale upflow anaerobic hybrid (UAHB) reactor combining a sludge blanket at the bottom and a filter media at the top, both with three-phase separators, was proposed to evaluate the recovery of dissolved methane. UAHB was operated with volumetric organic loading rate of 1.24 kg COD m−3 d−1 and hydraulic retention time of 8 h for 218 days to evaluate the influence of temperature (18°C, 23°C, and 28°C) in the methane dissolved in the effluent and collected from three-phase separators. Chemical oxygen demand (COD) and total suspended solids (TSS) removals efficiencies remained constant during the operation and equal to 90 and 95%, respectively, related to the activity of biomass retained in the filter media. Temperature increase influenced more the methane production in the sludge blanket rather than in the upper bed. The volume of recovered methane increased about 20% with the installation of the support media and the upper three-phase separator (3PHS). The loss of methane dissolved in the effluent was strongly influenced by the temperature, and higher with the decrease of this parameter. Non-statistically significant correlations were observed between the temperature and the methane production in the upper bed (p-value = 0.0943) and total (p-value = 0.0930). Thus, it can be concluded that the evaluated temperatures did not influence the global efficiency and the total methane yield of the UAHB reactor.

Evaluating the performance of anaerobic moving bed bioreactor and upflow anaerobic hybrid reactor for treating textile desizing wastewater

Performance and kinetic analysis of anaerobic moving bed bioreactor (AnMBBR) and upflow anaerobic hybrid reactor (UAHR) were investigated for the treatment of synthetic textile desizing wastewater (TDW) under organic loading rate (OLR) of 0.6–12 kgCOD/m3/day at thermophilic temperature (55 °C). The effects of increase in temperature (from 35 to 55 °C) on anaerobic treatment efficiency were studied. In the kinetic study for COD removal, first order substrate removal, Grau second order and modified Stover-Kincannon models were applied. By increasing temperature from 35 °C to 55 °C, COD removal, volumetric biogas production and methane content were increased 1.22, 2.58 and 1.08 times in AnMBBR. Whilst in the case of UAHR the increment for the aforementioned parameters were 1.10, 2.51 and 1.10 times, respectively. By increasing OLR from 0.6 to 6 kgCOD/m3/day, above 60% and 70% COD removal was observed, while the biogas increased from 0.12 to 0.97 L/L.day and 0.13–1.22 L/L.day for AnMBBR and UAHR, respectively. Up to an optimum OLR (6 and 8 kgCOD/m3/day for AnMBBR and UAHR) volumetric biogas production was also increased, simultaneously. Grau second order and modified Stover-Kincannon were found to be the best fit models (R2 =0.99). Biogas production and methane content in biogas were comparatively better in the case of real textile desizing wastewater due to lower sulfate concentration in the feed.

The methanogenic archaea characteristics and efficacy of aerobic waste sludge in the start-up of anaerobic hybrid reactors treating cassava wastewater

Inoculum is a crucial factor influencing the success of an anaerobic digester start-up. This study evaluated the efficacy of aerobic waste activated sludge (WAS) to start-up anaerobic hybrid reactors (AHR) treating cassava wastewater. The start-up performance and stability of five 6.2 L AHRs inoculated differently by WAS (AHR1) and WAS co-inoculated with pig manure (AHR2), cow dung (AHR3), chicken manure (AHR4), and anaerobic pond sludge (AHR5) were investigated. The results depicted the potential of WAS as starter seed for AHR's start-up. This sludge contained methanogenic populations, mainly Methanomicrobials, Methanosarcinales, and Thermoplasmatales, for 1.5 × 107 MPN/g VS compared to 4.0 × 103-6.0 × 107 MPN/g VS in manures and anaerobic sludge. Co-inoculation of WAS with cow dung (AHR3) and anaerobic sludge (AHR5) promoted a rapid start-up, achieved 4.0 kg COD/m3.d within 1.5-1.7 months, while about 2.5-3.3 months needed for the others. A satisfying performance, stability, microbial development and activity, depicted as high COD removal (CODrem) efficiency and methane productivity, were achieved in all digesters. About 0.32 and 0.21 m3/kg CODrem for biogas and methane yielded in AHR1, whereas 0.41-0.49 m3-biogas/kg CODrem and 0.25-0.32 m3-CH4/kg CODrem obtained in other reactors. This finding confirmed that inoculum's quality is critical for productive gas productivity and system stability maintenance.

Complementary Substrates-Brewery Wastewater and Piggery Effluent—Assessment and Microbial Community Profiling in a Hybrid Anaerobic Reactor

A hybrid anaerobic reactor was operated under the complementary effluents concept to reduce the unbalanced/inhibitory capacity of the provided piggery effluent. Brewery wastewater was chosen to complement piggery effluent (60:40% v/v, respectively). The HRT reduction from 6.7 to 3.0 days allowed the testing of an organic load increase from 4.5 to 10.0 g COD/L·d, which resulted in the almost doubling of biogas production. Biogas volumes (1.2 and 2.1 L/L·d, respectively) associated with its quality (>77% CH4) revealed that the hybrid anaerobic reactor responded positively to the operational changes and that piggery effluent can be advantageously digested using the brewery wastewater as the complementary effluent. The unit bottom and the packing bed were the main functional sections recognized in the hybrid. At the beginning of anaerobic digestion, bacterial populations belonged mostly to Bacteroidales (33%) and Clostridiales (35%). The process stability and the biogas quality at 3-d HRT were related to a change in the structure composition, since Flavobacteriales (18%), Bacillales (7%), Pseudomonadales (11%) and members of the Alcaligenaceae family (5%) also integrated the microbial communities. An evident change had also occurred in archaeal populations at this phase. Methanosaeta became the dominant genus (95%), confirming that acetoclastic methanogenesis was the main way for methane production.

Performance evaluation of an anaerobic hybrid reactor treating petrochemical effluent

Organic loading rate (OLR), Hydraulic Retention Time (HRT) and up flow velocity are important parameters significantly affecting microbial ecology and characteristics of anaerobic reactors. In this study, Performance of an anaerobic hybrid reactor (UASB/Filter) at mesophilic condition was evaluated in a 15.4 L reactor receiving petrochemical wastewater. The temperature of influent was adjusted by an inline heat exchanger at around 35 ˚C. The reactor was seeded with flocculent sludge from a UASB plant treating dairy wastewater. The sludge was acclimatized to petrochemical wastewater in twostage operation. After 39 weeks, a COD reduction of 70.3% was obtained at OLR=2.0 kg m-3 d-1 and HRT=18 h. Under steady state conditions, experiments were conducted at OLRs of between 0.5 and 24 kg TCOD m-3 d-1 , hydraulic retention times (HRT) of 4-48 h and up flow velocities 0.021-0.25 m h-1. Removal efficiencies in the range of 42-86% were achieved at feed TCOD concentrations of 1000- 4000 mg L-1 . The biogas production data used for determination of biogas production kinetics. The values of Gmax and GB estimated as 11.173 LL-1d -1 and 85.83 g L-1d -1 , respectively.

Evaluation of the production of biohydrogen during the co-digestion of organic wastes in an upflow hybrid anaerobic reactor

The effect of the hydraulic retention time (24, 12, and 6 h) during the co-digestion of organic residues was studied using a novel upflow hybrid anaerobic sludge reactor with a carbon/nitrogen ratio of 30, initial pH of 5.5, temperature of 35 °C, and a granular inoculum. The reactor performance at the tested HRTs followed the order 650 ± 50 (24 h) > 48 ± 4 (12 h) > 20 ± 2 mL BH2 g-1CDO removed (6 h). The content of the metabolites obtained using an HRT of 24 h followed the order acetic acid > isobutyric acid > butyric acid under acetogenic conditions. However, for HRTs of 12 and 6 h, the sequence was butyric acid > valeric acid > propionic acid > acetic acid. Based on molecular analyses, the biohydrogen selectivity was attributed to the presence of the genera Megasphaera, Clostridium, Lactobacillus, and Prevotella, which accounted for 26%, 2%, 12%, and 29% of the microbial biota at 24 h. Additionally, the yield of the upflow hybrid anaerobic reactor was superior to that of an upflow anaerobic reactor (24 h).

Treatment of slaughterhouse wastewater by upflow anaerobic hybrid reactor at pilot scale

Treatment of slaughterhouse wastewater by upflow anaerobic hybrid reactor at pilot scale

Enhancement of Biogas Production from Co-Digestion of Industrial Solid Pineapple Wastes by Two-Stage Anaerobic Digestion Systems

This study aimed to investigate the biogas and methane production, as well as the COD removal efficiency by AD from pineapple solid wastes (PSW) as co-digestion feedstock. The two-stage of anaerobic digestion system was configured as continuously stirred tank reactor (CSTR) installed with anaerobic hybrid reactor (AHR) in order to enhance the efficiency and stability in biogas production. The PSW were firstly characterized for chemical composition. Then, the total solids (TS) were controlled as 4% of TS in influent loadings and four different HRTs were determined to investigate the subsequent effects, such as pH, total volatile acids and alkaline (TVA/Alk) ratio, biogas and methane production, and COD removal efficiency. The results demonstrated that the overall pH condition in CSTR was more acidic than AHR system and simultaneously performed in less stability of AD process by presence of massive TVA/Alk ratio. Furthermore, the maximum biogas production and COD removal efficiency were also observed in AHR system at 2,702 mL and 80.53% under HRT7 and HRT15, respectively. Interestingly, more than thousand millilitres of biogas production were dramatically increased from CSTR system under parallel operation. Thus, the separated acidogenic and methanogenic stage in two-stage system obviously improved the potential of AD process. However, the methane yields in AHR system remained stable in the range of 0.16-0.19m3/kgCOD removed, excepted at the lowest HRT condition (HRT5) by increasing OLRs. Thus, the optimal conditions for biogas production and COD removal could be varied, which depending on the types of feedstocks and operational reactors.

Performance of a hybrid anaerobic reactor in the treatment of swine wastewater

Performance of a hybrid anaerobic reactor in the treatment of swine wastewater

Thermophilic Anaerobic Digestion of Second Cheese Whey: Microbial Community Response to H2 Addition in a Partially Immobilized Anaerobic Hybrid Reactor

In this study, we investigated thermophilic (55 °C) anaerobic digestion (AD) performance and microbial community structure, before and after hydrogen addition, in a novel hybrid gas-stirred tank reactor (GSTR) implemented with a partial immobilization of the microbial community and fed with second cheese whey (SCW). The results showed that H2 addition led to a 25% increase in the methane production rate and to a decrease of 13% in the CH4 concentration as compared with the control. The recovery of methane content (56%) was reached by decreasing the H2 flow rate. The microbial community investigations were performed on effluent (EF) and on interstitial matrix (IM) inside the immobilized area. Before H2 addition, the Anaerobaculaceae (42%) and Lachnospiraceae (27%) families dominated among bacteria in the effluent, and the Thermodesulfobiaceae (32%) and Lachnospiraceae (30%) families dominated in the interstitial matrix. After H2 addition, microbial abundance showed an increase in the bacteria and archaea communities in the interstitial matrix. The Thermodesulfobiaceae family (29%)remained dominant in the interstitial matrix, suggesting its crucial role in the immobilized community and the SHA-31 family was enriched in both the effluent (36%) and the interstitial matrix (15%). The predominance of archaea Methanothermobacter thermoautrophicus indicated that CH4 was produced almost exclusively by the hydrogenotrophic pathway.