Anaerobic Hybrid Reactor Research Articles

Energetic valorization of algal biomass in a hybrid anaerobic reactor

This study evaluated the operation of a hybrid anaerobic reactor fed with algal biomass cultivated in effluent from the brewery industry. Three stages of operation were distinguished during the 72 days of semi-continuous functioning of the reactor: Stage 1 (S1), in which algal biomass was used as substrate; Stage 2 (S2), in which 10% (v/v) of the algal biomass was substituted by olive mill wastewater (OMW); and Stage 3 (S3), in which algal biomass was heat pre-treated. During S1, a loss of solids was observed, with an increment of organic matter in the outlet. The substitution of 10% of the volume of algal biomass by OMW tripled the methane productivity obtained in the previous stage by digestion of pure algal biomass. Heat pre-treatment was not efficient in rupturing the cell wall, and consequently did not have any effect on the increase in biogas production. The complementarity of substrates in the assessed conditions led to better results than the pre-treatment of the algal biomass.

An anaerobic hybrid bioreactor for biologically enhanced primary treatment of domestic wastewater under low temperatures

Anaerobic hybrid reactor system for the generation of methane-rich biogas and energy. An energy-positive alternative to conventional primary treatment of raw domestic wastewater.

Anaerobic digestion of citrus industry effluents using an Anaerobic Hybrid Reactor

Mexico is one of the main citrus producers, ranking fourth in the world with approximately 7.4 million tons per year, with oranges contributing 4.08 million tons to that total. The effluents from the citrus industry have high loadings of organic matter and low pH levels. These effluents also are suitable for treatment by anaerobic digestion to reduce the organic matter and to obtain a value-added product, such as biogas. The aim of this work was to perform the anaerobic digestion of effluents from the citrus industry by using a high-rate reactor, evaluating the biogas production and use as an alternative energy source. An Anaerobic Hybrid Reactor (AHR) was used to treat the effluent from a citrus processing plant in Martinez de la Torre, Veracruz, Mexico. The AHR was operated at an organic loading rate (OLR) of 8 gCODT/Ld at steady state, obtaining a total and soluble COD removal of approximately 85%, with methane yields around 0.15 LCH4 to STP/gCODrem. An inhibitory effect was observed by the presence of D-limonene in the citrus effluent, although no pretreatment was used for elimination of this essential oil, a decrease in the COD removal and methane yields was observed due to the higher OLR. An energy estimate was obtained with the biogas, and it was found that up to 2.2% of the electricity required for the operation of a citrus processing plant can be generated using anaerobic treatment.

Biodegradation of Methylene Blue Dye by Sequential Treatment Using Anaerobic Hybrid Reactor and Submerged Aerobic Fixed Film Bioreactor

Laboratory scale experiments were carried out to access the feasibility of sequential anaerobic/aerobic biological treatment for the biodegradation of Methylene Blue (MB) dye. Anaerobic studies were performed using anaerobic hybrid reactor (consisting of UASB and Anaerobic filter) whereas submerged aerobic fixed film reactor was used as aerobic reactor. Degradation of MB dye was attempted using neutralized acetic acid (1000 mg/L) as co-substrate. MB dye concentration was stepwise increased from 10 to 70 mg/L after reaching steady state in each dye concentration. Such a gradual increase in the dye concentration helps in the proper acclimatization of the sludge to dyes thereby avoiding the possible inhibitory effects to biological activities at high dye concentrations. The overall treatment efficiency of MB through sequential anaerobic–aerobic reactor operation was 90% at maximum attempted dye concentration of 70 mg/L. The effluent from anaerobic reactor was analysed for intermediate biodegradation products through HPLC. It was observed that catechol, quinone, amino pyrine, 1,4 diamino benzene were present. However they were absent in final effluent.

Mainstream upflow nitritation-anammox system with hybrid anaerobic pretreatment: Long-term performance and microbial community dynamics

Mainstream nitritation-anammox is of strong interest to energy- and resource-efficient domestic wastewater treatment. However, there lack in-depth studies of pretreatment, tests of actual wastewater, and examination of long-term performance. Herein, an upflow nitritation-anammox granular reactor has been investigated to treat primary effluent with a hybrid anaerobic reactor (HAR) as pretreatment for more than 300 days. This system achieved 92% of COD removal, 75% of which was accomplished by the HAR, and had an average final effluent COD concentration of 22 mg L−1. More than 90% of ammonium was removed in the nitritation-anammox reactor, achieving a nitrogen removal rate of 81.0 g N m−3 d−1 in the last stage. The accumulation of sulfate-reducing bacteria in the HAR evidenced the effect of sulfate on COD removal and subsequent nitrogen removal. Anammox bacteria (predominantly Ca. Jettenia asiatica) accounted for up to 40.2% of total granular communities, but their abundance decreased over time in the suspended communities. The dynamics of major metabolisms and functional genes involved in nitrogen conversion were predicted by PICRUSt based on the taxonomic data, providing more insights into the functions of the microbial communities. These results have demonstrated the effectiveness and importance of anaerobic pretreatment to successful mainstream nitritation-anammox.

Comprehensive study on hybrid anaerobic reactor built-in with sleeve type bioelectrocatalyzed modules

The successful application of bio-electrocatalyzed system (BES) to wastewater treatment inevitably depends on the improvement of performance and the reduction of costs at a scale-up level. One efficient way to achieve these goals is to couple BES with traditional anaerobic processes to industrial wastewater treatment. Here we developed a hybrid anaerobic system built-in with electrode modules (HAR-BES, 30L) as an inexpensive but high-performance process for azo dye containing wastewater treatment. HAR-BES showed faster start-up, 10% higher azo dye decolorization efficiency, and 20% higher COD removal efficiency than an anaerobic reactor (AR) without electrode modules. Microbial community analysis showed functional diversity in electrode biofilm and sludge samples. Geobacter and Syntrophus, which would account for electrode respiration and reduction of azo dye, respectively, were dominant in electrode biofilms. Tracer experiments and modeling of residence time distribution indicated that the fluid pattern in HAR-BES was close to plug flow. Simulation of computational fluid dynamics showed faster water velocity near electrode modules and better sludge expansion in HAR-BES than AR. This study proved that HAR-BES improved anaerobic wastewater treatment comprehensively through the analysis of chemicals, microbial community, and modeling of fluid pattern.

A Mini Review of the Techno-environmental Sustainability of Biological Processes for the Treatment of High Organic Content Industrial Wastewater Streams

Industrial wastewater contains complex and slowly biodegradable compounds often ineffectively treated by conventional activated sludge (CAS) systems. Alternatively, advanced anaerobic technologies are implemented. The current study reviews different potential anaerobic schemes, factors influencing their final performance and optimum combinations of operational/design parameters. Anaerobic membrane bioreactors, upflow anaerobic sludge blanket reactors, expanded granular sludge beds, anaerobic hybrid reactors and inverse fluidized bed reactors are discussed. Their major advantages include: low energy requirements, energy recovery through biogas generation and high organic load removal. pH = 7, operation in a mesophilic environment and a hydraulic retention time long enough to enable anaerobic digestion in economically accepted reactor volumes are conditions that optimize the performance of anaerobic configurations. The evaluation additionally considers environmental aspects. The life cycle assessment of anaerobic industrial wastewater treatment reveals its positive environmental effect in terms of greenhouse gases emissions. Methane (a greenhouse gas) primarily contained in the biogas, despite being produced during anaerobic digestion, is utilized for energy production (heating, electricity) instead of being emitted to the atmosphere. Finally, anaerobic wastewater treatment is analyzed as part of the European Commission Innovation Deal that aims at converting conventional wastewater treatment plants to water resource recovery facilities able to combine sustainable wastewater treatment and water reuse.

Microbial Fuel Cell a Reliable Source for Recovery of Electrical Power from Synthetic Wastewater

Microbial fuel cells (MFCs) were successfully used as a biological process to remove organic load from synthetic wastewater. Electricity was produced via oxidation of biodegradable organic matter in the presence of active biocatalyst. The system was able to generate clean energy at high efficiency. Wastewater contained organic compound used as substrate in the anaerobic chamber of MFC. The chemical energy generated sufficient electrons which were passed through a resistance to identify current density and liberate electric power as energy source. Acetone as biodegradable substrate with concentration of 3g.l-1 was introduced as carbon source in the anode chamber of the MFC. The mixed culture of living microorganisms originated from a biological treatment unit used for anaerobic degradation of organic substrate. The inoculums were supplied by an up flow anaerobic hybrid reactor, a pilot scale bioreactor used for treating pulp and paper wastewater. In this course of treatment, once chemical oxygen demand was removed the current and power was generated while data were recorded via online acquisition system. Also polarization curve was obtained for each set of experiment. In cathode compartment several concentration of ferocynide and potassium permanganate were added to obtain the optimal concentration of oxidizing agents in the cathode chamber. At concentration of 300 μM potassium permanganate, the maximum power and current generated were 22 mW.m-2 and 70 mA.m-2, respectively.

Evaluation of anaerobic sludge volume for improving azo dye decolorization in a hybrid anaerobic reactor with built-in bioelectrochemical system

A hybrid anaerobic reactor with built-in bioelectrochemical system (BES) has been verified for efficiently treating mixed azo dye wastewater, yet still facing many challenges, such as uncertain reactor construction and insufficient electron donors. In this study, an up-flow hybrid anaerobic reactor with built-in BES was developed for acid orange 7 (AO7) containing wastewater treatment. Cathode and real domestic wastewater both served as electron donor for driving azo dye decolorization. The decolorization efficiency (DE) of AO7 (200 mg/L) in the hybrid reactor was 80.34 ± 2.11% with volume ratio between anaerobic sludge and cathode (VRslu:cat) of 0.5:1 and hydraulic retention time (HRT) of 6 h, which was 15.79% higher than that in BES without sludge zone. DE was improved to 86.02 ± 1.49% with VRslu:cat increased to 1:1. Further increase in the VRslu:cat to 1.5:1 and 2:1, chemical oxygen demand (COD) removal efficiency was continuously improved to 28.78 ± 1.96 and 32.19 ± 0.62%, but there was no obvious DE elevation (slightly increased to 87.62 ± 2.50 and 90.13 ± 3.10%). BES presented efficient electron utilization, the electron usage ratios (EURs) in which fluctuated between 11.02 and 13.06 mol e−/mol AO7. It was less than half of that in sludge zone of 24.73–32.06 mol e−/mol AO7. The present work optimized the volume ratio between anaerobic sludge and cathode that would be meaningful for the practical application of this hybrid system.

Comparative evaluation of biogas production from dairy manure and co-digestion with maize silage by CSTR and new anaerobic hybrid reactor.

This study aimed to investigate potential methane production through anaerobic digestion of dairy manure and co-digestion with maize silage. Two different anaerobic reactor configurations (single-stage continuously stirred tank reactor [CSTR] and hybrid anaerobic digester) were used and biogas production performances for each reactor were compared. The HR was planned to enable phase separation in order to improve process stability and biogas production under higher total solids loadings (≥4%). The systems were tested under six different organic loading rates increased steadily from 1.1 to 5.4 g VS/L.d. The CSTR exhibited lower system stability and biomass conversion efficiency than the HR. The specific biogas production of the hybrid system was between 440 and 320 mL/gVS with 81-65% volatile solids (VS) destruction. The hybrid system provided 116% increase in specific biogas production and VS destruction improved by more than 14%. When MS was co-digested together with dairy manure, specific biogas production rates increased about 1.2-fold. Co-digestion was more beneficial than mono-material digestion. The hybrid system allowed for generating methane enriched biogas (>75% methane) by enabling phase separation in the reactor. It was observed that acidogenic conditions prevailed in the first two compartments and the following two segments as methanogenic conditions were observed. The pH of the acidogenic part ranged between 4.7 and 5.5 and the methanogenic part was between 6.8 and 7.2.

Recovery of elemental sulphur from anaerobic effluents through the biological oxidation of sulphides

ABSTRACTThe aim of the present study was to evaluate the biological oxidation of sulphide in two different UASB reactors by assessing the occurrence of oxidized forms of sulphur in the effluents and the amount of S0 that could be recovered in the process. The bioreactors employed were an anaerobic hybrid (AH) reactor employing porous polyurethane foam as support media and a micro-aerated UASB reactor equipped with an aeration device above the digestion zone. The AH reactor produced a final effluent containing low concentrations of S2– (3.87% of total sulphur load). It was achieved due to a complete oxidation of 56.1% of total sulphur. The partial biological oxidation that occurred in the AH reactor allowed the recovery of 30% of the sulphur load as S0. The effluent from the micro-aerated UASB reactor contained 5% of the sulphur load in the form of S2–, while 20.9% was present as dissolved SO42– and 46% was precipitated as S0. It is concluded that the AH reactor or micro-aeration carried out above the digestion zone of the UASB reactor favoured the biological oxidation of S2– and the release of odourless effluents. Both technologies represent feasible and low-cost alternatives for the anaerobic treatment of domestic sewage.

Effect of electrode position on azo dye removal in an up-flow hybrid anaerobic digestion reactor with built-in bioelectrochemical system

In this study, two modes of hybrid anaerobic digestion (AD) bioreactor with built-in BESs (electrodes installed in liquid phase (R1) and sludge phase (R2)) were tested for identifying the effect of electrodes position on azo dye wastewater treatment. Alizarin yellow R (AYR) was used as a model dye. Decolorization efficiency of R1 was 90.41 ± 6.20% at influent loading rate of 800 g-AYR/ m3·d, which was 39% higher than that of R2. The contribution of bioelectrochemical reduction to AYR decolorization (16.23 ± 1.86% for R1 versus 22.24 ± 2.14% for R2) implied that although azo dye was mainly removed in sludge zone, BES further improved the effluent quality, especially for R1 where electrodes were installed in liquid phase. The microbial communities in the electrode biofilms (dominant by Enterobacter) and sludge (dominant by Enterococcus) were well distinguished in R1, but they were similar in R2. These results suggest that electrodes installed in liquid phase in the anaerobic hybrid system are more efficient than that in sludge phase for azo dye removal, which give great inspirations for the application of AD-BES hybrid process for various refractory wastewaters treatment.

Evaluation of a hybrid anaerobic biofilm reactor treating winery effluents and using grape stalks as biofilm carrier

ABSTRACTWine production processes generate large amount of both winery wastewater and solid wastes. Furthermore, working periods, volumes and pollution loads greatly vary over the year. Therefore, it is recommended to develop a low-cost treatment technology for the treatment of winery effluents taking into account the variation of the organic loading rate (OLR). Accordingly, we have investigated the sequential operation of an anaerobic biofilm reactor treating winery effluents and using grape stalks (GSs) as biofilm carrier with an OLR ranging from 0.65 to 27 gCOD/L/d. The result showed that, during the start-up with wastewater influent, the chemical oxygen demand (COD) removal rate ranged from 83% to 93% and was about 91% at the end of the start-up period that lasted for 40 days. After 3 months of inactivity period of the reactor (no influent feeding), we have succeeded in restarting-up the reactor in only 15 days with a COD removal of 82% and a low concentration of volatile fatty acids (1 g/L), which confirms the robustness of the reactor. As a consequence, GSs can be used as an efficient carrier support, allowing a fast reactor start-up, while the biofilm conserves its activity during a non-feeding period. The proposed hybrid reactor thus permits to treat both winery effluents and GSs.

Bio-Kinetic Analysis of Tannery and Sago Effluents Treated in UASB and HUASB Reactor

The present study is related to treatment of tannery and sago wastewater in up flow anaerobic sludge blanket reactor and hybrid reactor. The effectiveness of the biological treatment of wastewater involves appropriate microorganisms. COD was reduced to 91.67% and 92.38% in UASB reactor and HUASB reactor. Likewise the BOD was reduced to 83.73% and 90.96% in UASB and HUASB respectively at an HRT of 45 h. The reactor was operated at an OLR of 4.210 mg COD/min L. Various Bio-kinetic models were applied to data obtained from the experimental studies in batch operated UASB and HUASB reactors. Treatment efficiencies were investigated at different hydraulic retention times. Second order models were found to be the best fit for all the effluents treated in both the reactor. The second order model showed the fitness with regression coefficient more than 0.91.

Role of sludge volume index in anaerobic sludge granulation in a hybrid anaerobic reactor

This work focuses on microbial granulation in hybrid anaerobic reactors (HAR). Five HARs were used in two sets of experiments and all were seeded with the same inoculum. The volume of inoculum added was 10%, 20%, 30%, 40% and 50% in the first and 13%, 15%, 18%, 23%, and 27% in the second set of experiment. The volume of inocula added affects the sludge volume index, which in the present study proves to be important parameter for granulation. The results suggest that if SVI during the reactor start-up is kept between 150 and 210, reactors were able to form granules. Outside this range in the present set-up, no granulation was observed due to increased biomass wash-out, causing decreased SRT. Higher methane production was achieved in reactors with good granulation. The DGGE profiles show that the non-granulating systems had lesser diversity, due to increased wash out. Archaeal profile gave better correlation for granulation. Granulating reactors were rich in aceticlastic methanogens over hydrogen utilizing groups, especially Methanosaetaceae. Both Methanosarcina and Methanosaeta are required for better granulation as confirmed quantitatively. Bacterial profile of granulating reactors were rich in acetogens. SEM (Scanning electron microscopy) pictures show that granules are dominated by Methanosaeta-like microbes. Thus, the sludge characteristics at the start-up are of vital importance as they influence the sludge quality developed during the reactor operation and also the microbial communities retained.

Fate of parasites and pathogenic bacteria in an anaerobic hybrid reactor followed by downflow hanging sponge system treating domestic wastewater.

Treatment of domestic wastewater in a pilot-scale upflow anaerobic hybrid (AH) reactor (0.9 m(3)) in combination with downflow hanging sponge (DHS) system (1.3 m(3)) was investigated. The combined system was operated at a hydraulic retention time (HRT) of 6.0 h for AH and 3.2 h for DHS system. The total process achieved a substantial reduction of COD(total) resulting in an average effluent concentration of only 39 ± 12 mg/l. Moreover, 90 ± 7% of ammonia was eliminated in the DHS system. Nitrate and nitrite data revealed that 49 ± 3.2% of the ammonia removal occurred through nitrification process. The removal efficiency of total coliform (TC), fecal coliform (FC), and fecal streptococci (FS) was relatively low in the AH reactor. The major portion of TC, FC, and FS was removed in the DHS system resulting to an average count of 1.7 × 10(5) ± 1.1 × 10(2)/100 ml for TC, 7.1 × 10(4) ± 1.2 × 10(2)/100 ml for FC, and 7.5 × 10(4) ± 1.3 × 10(2)/100 ml for FS in the final effluent. Likely, the combined system was very efficient for the removal of protozoological species such as sarcodins (Entamoeba cysts), flagellates (Giardia cysts), and ciliates (Balantidium cysts). This was not the case for coccidia (Cryptosporidium oocysts), where 36.4 and 27.3% were detected in the effluent of AH and DHS system, respectively. Only 10% of intestinal nematode and cestode ova were recorded in the effluent of AH reactor and were completely removed in the DHS system.

Metagenomics shows that low-energy anaerobic-aerobic treatment reactors reduce antibiotic resistance gene levels from domestic wastewater.

Effective domestic wastewater treatment is among our primary defenses against the dissemination of infectious waterborne disease. However, reducing the amount of energy used in treatment processes has become essential for the future. One low-energy treatment option is anaerobic-aerobic sequence (AAS) bioreactors, which use an anaerobic pretreatment step (e.g., anaerobic hybrid reactors) to reduce carbon levels, followed by some form of aerobic treatment. Although AAS is common in warm climates, it is not known how its compares to other treatment options relative to disease transmission, including its influence on antibiotic resistance (AR) in treated effluents. Here, we used metagenomic approaches to contrast the fate of antibiotic-resistant genes (ARG) in anaerobic, aerobic, and AAS bioreactors treating domestic wastewater. Five reactor configurations were monitored for 6 months, and treatment performance, energy use, and ARG abundance and diversity were compared in influents and effluents. AAS and aerobic reactors were superior to anaerobic units in reducing ARG-like sequence abundances, with effluent ARG levels of 29, 34, and 74 ppm (198 ppm influent), respectively. AAS and aerobic systems especially reduced aminoglycoside, tetracycline, and β-lactam ARG levels relative to anaerobic units, although 63 persistent ARG subtypes were detected in effluents from all systems (of 234 assessed). Sulfonamide and chloramphenicol ARG levels were largely unaffected by treatment, whereas a broad shift from target-specific ARGs to ARGs associated with multi-drug resistance was seen across influents and effluents. AAS reactors show promise for future applications because they can reduce more ARGs for less energy (32% less energy here), but all three treatment options have limitations and need further study.

Pattern of Biogas Production and Removal of Chemical Oxygen Demand in Semi Continues Hybrid Anaerobic Reactor

Anaerobic process had been used for treated highly organic substances, such as canteen wastewater which had COD around 5000 mg/L. This research aims to investigate pattern of biogas production and COD removal in semi continue anaerobic process. HRT (Hydraulic Retention Times) were used in this research 1,5 hours. The reactor was contained of four cell coulombs from PVC, with height 1 meter. Gravel as media support in hybrid anaerobic reactor. The height of media support is 50 cm. This reactor operated for 14 days. Parameters had been observed are biogas production and COD.. Biogas production after reactor operated 7 days 0,6594 mL and after reactor operated 14 days is 1,4758 mL. COD removals are 38,89 mg/L after operated 7 days and 42,86 mg/L after operated 14 days. In conclusion, COD removal increased after reactor operated 7 and 14 days. The biogas production increased after 7 and 14 operated days. Increasing of biogas production more drastically than COD removal

A comprehensive review on utilization of wastewater from coffee processing.

The coffee processing industry is one of the major agro-based industries contributing significantly in international and national growth. Coffee fruits are processed by two methods, wet and dry process. In wet processing, coffee fruits generate enormous quantities of high strength wastewater requiring systematic treatment prior to disposal. Different method approach is used to treat the wastewater. Many researchers have attempted to assess the efficiency of batch aeration as posttreatment of coffee processing wastewater from an upflow anaerobic hybrid reactor (UAHR)-continuous and intermittent aeration system. However, wet coffee processing requires a high degree of processing know-how and produces large amounts of effluents which have the potential to damage the environment. Characteristics of wastewater from coffee processing has a biological oxygen demand (BOD) of up to 20,000 mg/l and a chemical oxygen demand (COD) of up to 50,000 mg/l as well as the acidity of pH below 4. In this review paper, various methods are discussed to treat coffee processing wastewaters; the constitution of wastewater is presented and the technical solutions for wastewater treatment are discussed.

Utilization of solid and liquid waste generated during ethanol fermentation process for production of gaseous fuel through anaerobic digestion – A zero waste approach

Preliminary investigations were performed in the laboratory using batch reactors at 10% solid concentration for the assessment of the biogas production at thermophilic and mesophilic temperatures using solid residues generated during ethanol fermentation process. One kg of solid residues (left after enzyme extraction and enzymatic hydrolysis) from thermophilic reactors (TR1 and TR2) produced around 131 and 84L of biogas, respectively, whereas biogas production from mesophilic reactors (MR1 and MR2) was 86 and 62L, respectively. After 20 and 35days of retention time, the TS and VS reductions from TR1, TR2 and MR1, MR2 were found to be 39.2% and 35.0%, 67.3% and 61.0%, 21.0% and 18.0%, 34.7% and 27.8%, respectively. Whereas the liquid waste was treated using four laboratory anaerobic hybrid reactors (AHRs) with two different natural and synthetic packing media at 15–3days HRTs. AHRs packed with natural media showed better COD removal efficiency and methane yield.