Anaerobic Fixed Bed Reactor Research Articles

Simultaneous nitrogen and phosphorus removal through an integrated partial-denitrification/anammox process in a single UAFB system

With the aim of obtaining enhanced nitrogen removal and phosphate recovery in mainstream sewage, we examined an integrated partial-denitrification/anaerobic ammonia oxidation (PD/A) process over a period of 189 days to accomplish this goal. An up-flow anaerobic fixed-bed reactor (UAFB) used in the integrated PD/A process was started up with anammox sludge inoculated and the influent composition controlled. Results showed that the system achieved a phosphorus removal efficiency of 82% when the influent concentration reached 12.0 mg/L. Batch tests demonstrated that stable and efficient removal of chemical oxygen demand (COD), nitrogen, and phosphorus was achieved at a COD/NO3−-N ratio of 3.5. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis indicated that hydroxyapatite was the main crystal in the biofilm. Furthermore, substrate variation along the axial length of UAFB indicated that partial denitrification and anammox primarily took place near the reactor's bottom. According to a microbiological examination, 0.4% of the PD/A process's microorganisms were anaerobic ammonia oxidizing bacteria (AnAOB). Ca. Brocadia, Ca. Kuenenia, and Ca. Jettenia served as the principal AnAOB generals in the system. Thauera, Candidatus Accumulibacter, Pseudomonas, and Acinetobacter, which together accounted for 27% of the denitrifying and phosphorus-accumulating bacteria, were helpful in advanced nutrient removal. Therefore, the combined PD/A process can be a different option in the future for sewage treatment to achieve contemporaneous nutrient removal.

Acclimatizing waste activated sludge in a thermophilic anaerobic fixed-bed biofilm reactor to maximize biogas production for food waste treatment at high organic loading rates

Thermophilic anaerobic digestion (TAD) provides a promising solution for sustainable high-strength waste treatment due to its enhanced methane-rich biogas recovery. However, high organic loading rates (OLR) exceeding 3.0 kgCOD/m3/day and short hydraulic retention times (HRT) below 10 days pose challenges in waste-to-energy conversion during TAD, stemming from volatile fatty acids (VFAs) accumulation and methanogenesis failure. In this study, we implemented a stepwise strategy for acclimatizing waste activated sludge (WAS) in a thermophilic anaerobic fixed-bed biofilm reactor (TA-FBBR) to optimize methanogen populations, thereby enhancing waste-to-energy efficiencies under elevated OLRs in food waste treatment. Results showed that following stepwise acclimatization, the TA-FBBR achieved stable methane production of approximately 5.8 L/L-reactor/day at an ultrahigh OLR of ∼20 kgCOD/m3/day and ∼15 kgVS/m3/day at 6-day HRT in food waste treatment. The average methane yield reached 0.45 m3/kgCODremoval, attaining the theoretical production in TAD. Moreover, VFA concentrations were stabilized below 1000 mg/L at the ultrahigh OLR under 6-day HRT, while maintaining an acetate/propionate ratio of > 1.8 and a VFA/TAK ratio of < 0.3 serving as effective indicators of system stability and methane yield potential. The microbial community analysis revealed that the WAS acclimatization strategy fostered the microbial diversity and abundance of Methanothermobacter and Methanosarcina. Methanosarcina in the biofilm were observed to be twice as abundant as Methanothermobacter, indicating a potential preference for biofilm existence among methanogens. The findings demonstrated an effective strategy, specifically the stepwise acclimatization of WAS in a thermophilic fixed-bed biofilm reactor, to enhance the food waste treatment performance at high OLRs, contributing valuable mechanistic and technical insights for future sustainable high-strength waste management.

Enhanced anaerobic degradation of azo dyes by biofilms supported by novel functionalized carriers

Azo dyes are significant organic pollutants known for their adverse effects on humans and aquatic life. In this study, anthraquinone-2-sulfonate (AQS) immobilized on biochar (BC) was employed as a novel carrier in up-flow anaerobic fixed-bed reactors to induce specific biofilm formation and promote the biotransformation efficiency of azo dyes. Novel carrier–packed reactor 1 (R1) and BC-packed reactor 2 (R2) were used to treat red reactive 2 (RR2) under continuous operation for 175 days. The decolorization rates of R1 and R2 were 96–83% and 91–73%, respectively. The physicochemical characteristics and extracellular polymeric substances (EPS) of the biofilm revealed a more stable structure in R1. Furthermore, the microbial community in R1 interacted more closely with each other and contained more keystone genera. Overall, this study provides a feasible method for improving the biotransformation of azo dyes, thus providing support for practical applications in wastewater treatment projects.

Impact of Temperature on the Performance and Character of the Methanogenic Community of a Fixed-Bed Anaerobic Reactor at Psychrophilic Temperature

To determine the effects of a gradual temperature decrease on reactor performance and the microbial community, four fixed-bed reactors that were packed with a biofilm carrier were operated for 217 days. The temperature of the reactors was decreased from 30 °C to 3 °C. The reactors initially soured at 3 °C and recovered when they were returned to 4 °C, as indicated by the stabilization of biogas production, methane production, VFA concentration, pH, and the COD removal rate. Our results also revealed that methanomicrobiales were the dominant methanogen, the concentration of the 16S rRNA gene in the carbon-fiber carrier sludge exceeded the same gene concentration in the deposited sludge, and that the carbon-fiber carrier played an important role in methanomicrobiale colonization at low temperatures. We suggest that 4 °C is the low-temperature threshold for optimal reactor performance.

Evaluation of anaerobic and anoxic reactors installed in serial to treat fish tank effluent

Effluent from a fish tank with Nile tilapia (Oreochromis niloticus) was treated in a system of two parallel fixed-bed anaerobic reactors followed by a suspended stirred, anoxic reactor for solids, organic matter and nitrogen removal. Microbial community structure was compared between the reactors and an enriched anammox culture originated from anaerobic sludge by using the PCR (Polymerase Chain Reaction) and DGGE (Denaturing Gradient Gel Electrophoresis) techniques. DGGE analysis revealed three large microbial clusters, namely, the biomass in the inoculum, the biomass growing in the reactors, and the enriched anammox culture. The similarity between the microbial community recovered from the anaerobic reactors and the anammox community was considered low (32.7%), suggesting differentiation of the bacterial community as a function of the selection of specific anammox groups. The last step in the anoxic reactor had worsened the effluent quality. The potential of organic matter and ammonia removal in a single anaerobic reactor was demonstrated.

The Simulation and Experimental Study of COD Removal from Rubber Industrial Wastewater using Anaerobic Fixed Bed Reactors

The Simulation and Experimental Study of COD Removal from Rubber Industrial Wastewater using Anaerobic Fixed Bed Reactors

Bacteria and archaea involved in anaerobic mercury methylation and methane oxidation in anaerobic sulfate–rich reactors

The identification of dominant microbes in anaerobic mercury (Hg) methylation, methylmercury (MeHg) demethylation, and methane oxidation as sulfate-reducing bacteria, methanogens or, probably, anaerobic methanotrophic archaea (ANMEs) is of great interest. To date, however, the interrelationship of bacteria and archaea involved in these processes remains unclear. Here, we demonstrated the dynamics of microorganisms participating in these processes. Anaerobic fixed-bed reactors were operated with swine manure and sludge to produce methane stably, and then, sulfate (reactor C), sulfate and Hg(II) (reactor H), and sulfate and MeHg (reactor M) were added, and the reactors were operated for 120 d, divided equally into four periods, P1–P4. The bacterial compositions changed nonsignificantly, whereas Methanosaeta in reactors H and M decreased significantly, revealing that it was irrelevant for Hg transformation. The abundances of Syntrophomonadaceae, Methanoculleus, Candidatus Methanogranum and Candidatus Methanoplasma increased continuously with time; these species probably functioned in these processes, but further evidence is needed. Desulfocella and Desulfobacterium dominated first but eventually almost vanished, while the dominant archaeal genera Methanogenium, Methanoculleus and Methanocorpusculum were closely related to ANME–1 and ANME–2. PLS-DA results indicated that both bacteria and archaea in different periods in the three reactors were clustered separately, implying that the microbial compositions in the same periods were similar and changed markedly with time.

Phosphorus recovery via the formation of hydroxyapatite crystals at various nitrogen loading rate in an anammox-based UAFB

A strategy that integrates the anammox and hydroxyapatite crystallization in an up-flow anaerobic fixed-bed reactor (UAFB) was investigated to simultaneously remove nitrogen and recover phosphorus. During the 430 days of operation, 73.1 ± 6.6% of influent phosphorus was removed with an efficient nitrogen removal efficiency of 87.8 ± 1.7%. After long-term operation, numerous acicular and micron-sized crystals were observed on the matured biofilm, of which the phosphorus content was around 10.21% (wt%) and hydroxyapatite was the main form of crystals through SEM-EDS, FT-IR and XRD analysis. The variation of substrates along the axial length of UAFB showed that phosphate removal was positively correlated with anammox and pH. Moreover, three anammox bacteria including Candidatus Brocadia (19.73%), Candidatus Jettenia (0.49%) and Candidatus Kuenenia (0.85%) were detected at the bottom of UAFB, while Candidatus Jettenia (4.67%) was dominant at the top. Hence, the anammox-based biofilm system could be alternative for the recovery of phosphorus from nutrient-rich wastewater.

Methane recovery from acidic tofu wastewater using an anaerobic fixed-bed reactor with bamboo as the biofilm carrier

Wastewater generated during acid coagulation in tofu processing has high organic concentrations and low pH. Several small industries in Indonesia discharge such wastewater without treatment, necessitating economical treatment to control water pollution. In this study, the feasibility of methane production from the treatment of acidic tofu processing wastewater was investigated. For this, anaerobic treatment of tofu processing wastewater using a fixed-bed reactor employing cut bamboo as the carrier was examined and compared to an upflow anaerobic sludge blanket reactor. Without neutralization, the fixed-bed reactor outperformed the upflow anaerobic sludge blanket reactor at a chemical oxygen demand load of 4.3 kg chemical oxygen demand/m3 day. The highest total organic carbon removal efficiency and methane gas yield were 95% and 0.98 L/g total organic carbon removed, respectively. The two most abundant bacteria were the genus Paludibacter and the unclassified Bacteriodetes; both from the family Porphyromonadaceae. Hydrogenotrophic methanogens from the genera Methanoculleus and Methanobacterium were the dominant archaea, indicating that hydrogenotrophic methanogenesis was a major methane formation pathway.

Efficiency of microbial fuel cells based on the sulphate-reduction by ethanol

The influence of hydraulic retention time (HRT) on the rate of sulphate-reduction and electricity generation of microbial fuel cell fed with ethanol was studied. The experiments were performed in the laboratory installation, consisting of an anaerobic fixed-bed reactor and a microbial fuel cell with air-cathode. An effective sulphate removal was achieved at hydraulic retention times 44 and 66 h. The effectiveness of COD removal raises with increasing the hydraulic retention time. The highest maximum power density of 258 mW/m2 was obtained at 22 h HRT. The use of ethanol as an electron donor had a great impact on the composition of the microbial community. The metagenomic data obtained showed that the most abundant phylum in bacterial community was Proteobacteria – 87.8 %, and particularly Gammaproteobacteria – 53,1%. The sulphate reducing bacteria that can incompletely oxidise organic compounds usually with acetate as an end product were presented in the microbial community in anodic chamber. The dominant microbial species among sulphate reducing bacteria was Desulfomicrobium mexicanus (19,79%).

Impact of Organic Loading Rate on Performance and Methanogenic Microbial Communities of a Fixed-Bed Anaerobic Reactor at 4 °C

We investigated the feasibility of producing biogas in a fixed-bed anaerobic reactor at 4 °C with a gradual increase in organic loading rate (OLR). Reactor efficiency was highest when OLR was 4.33 kg/m3·d, whereas the reactor acidification occurred when OLR was 4.67 kg/m3·d. The values of methane content, biogas production, chemical oxygen demand (COD) removal rate, biogas production rate, acetic acid content, and propionic acid content were 69.3%, 5.33 L, 59.8%, 1.03 L/OLR, 0.17 g/L, and 1.15 g/L, respectively. The pH was stable and ranged from 7.2 to 6.8 when the reactor was operating at 4 °C during OLR increase. The 16S rRNA gene analysis revealed that the dominant archaea were Methanosaetaceae at 30 °C. At 4 °C, the dominant archaea were Methanomicrobiales, which were more abundant in adhering sludge compared to settled sludge. In conclusion, operating a fixed-bed anaerobic reactor at psychrophilic temperatures is more suitable.

Influence of organic loading rate on ciprofloxacin and sulfamethoxazole biodegradation in anaerobic fixed bed biofilm reactors

Antibiotic compounds, notably sulfamethoxazole (SMX) and ciprofloxacin (CIP), are ubiquitous emerging contaminants (ECs), which are often found in domestic sewage. They are associated with the development of antimicrobial resistance. Operational parameters, e.g. organic loading rate (OLR), hydraulic retention time (HRT) and sludge retention time, may influence EC biodegradation in wastewater treatment plants. This study assessed the impact of the OLR variation on the biodegradation of CIP and SMX, applying two configurations of anaerobic fixed bed reactors: anaerobic packed bed biofilm reactor (APBBR) and anaerobic structured bed biofilm reactor (ASBBR). A significant reduction in the biodegradation of SMX (APBBR: 93–69%; ASBBR: 94–81%) and CIP (APBBR: 85–66%; ASBBR: 85–64%) was observed increasing OLR from 0.6 to 2.0 kgCOD m−3 d−1. The decrease in the HRT from 12 to 4 h resulted in higher liquid-phase mass transfer coefficient (APBBR: ks from 0.01 to 0.05 cm h−1; ASBBR: ks from 0.07 to 0.24 cm h−1), but this was not enough to overcome the decrease in the antibiotic-biomass contact time on biofilm, thus reducing the bioreactors’ performance. The ASBBR favored biomethane production (from 7 to 17 mLCH4 g−1VSS L−1 d−1) and biodegradation kinetics (kbio from 1.7 to 4.2 and for SMX and from 2.1 to 4.8 L g−1VSS d−1 for CIP) due to the higher relative abundance of the archaea community in the biofilm and the lower liquid-phase mass transfer resistance in the structured bed. CIP and SMX cometabolic biodegradation was associated to the hydrogenotrophic methanogenesis (mainly Methanobacterium genus) in co-culture with fermentative bacteria (notably the genera Clostridium, Bacillus, Lactivibrio, Syntrophobacter and Syntrophorhabdus). The anaerobic fixed bed biofilm reactors proved to be highly efficient in biodegrading the antibiotics, preventing them from spreading to the environment.

Performances of Conventional and Hybrid Fixed Bed Anaerobic Reactors for the Treatment of Aquaculture Sludge.

Aquaculture fish production is experiencing an increasing trend worldwide and determines environmental concerns mainly related to the emission of pollutants. The present work is focused on the improvement of the sustainability of this sector by assessing the anaerobic digestion (AD) of slurry. Wastewater from experimental plants for the production of trout (Udine, Italy) was subject to screening by a drum filter, and then to thickening in a settling tank. The thickened sludge, representing the input of AD, was characterized by total and volatile solids contents of 3969.1–9705.3 and 2916.4–7154.9 mg/L, respectively. The AD was performed in a containerized unit with two digesters (D1 and D2), biogas meters and monitoring of the temperature, pH and redox potential. Both reactors are mixed by a recirculation of the digestate, and reactor D2 is equipped with a fixed bed. The tests were performed at 38 °C with diversified loading rates and hydraulic retention times (HRT). HRT varied from 28.9 to 20.3 days for D1 and from 18.3 to 9.3 days for D2. Methane yields resulted as highest for the hybrid digester with the longest HRT (779.8 NL of CH4/kg VS, 18.3 days). The conventional digester presented its best performance, 648.8 NL of CH4/kgVS, with an HRT of 20.3 days.

Kinetic modeling of an anaerobic fixed-bed reactor treating industrial wastewater containing hydrothermally solubilized sugarcane bagasse and post-treatment evaluation

Kinetic modeling of an anaerobic fixed-bed reactor treating industrial wastewater containing hydrothermally solubilized sugarcane bagasse and post-treatment evaluation

Anaerobic biological treatment of industrial saline wastewater: fixed bed reactor performance and analysis of the microbial community structure and abundance

ABSTRACTThe purpose of the present work is to treat saline Tuna fish wastewater, with the salt concentration of 43 g L−1 and total organic carbon (TOC) of 8.3 g L−1, using an anaerobic fixed bed reactor involving salt-tolerant bacteria from the natural hypersaline environment during 150 days. The highest volatile solids (VS) removal efficiency of 84.1% was recorded for the organic loading rate (OLR) of 1.04 g TOC L−1.d−1 and the lowest salinity of 14.6 g NaCl L−1. In addition, the maximum biogas production of 0.8 L−1.d−1 for a working volume of 4 L and an organic loading rate of 2.07 g TOC L−1.d−1 correlated with the decrease of Volatile fatty acids (VFA) content. The Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and the phylogenetic analysis of the bacterial community showed the action of hydrolytic, acidogenic, halotolerant sulfate-reducing and halophilic fermentative bacterium during the processing time. A stable archaeal and methanogenic community’s diversity including hydrogenotrophic methanogens was demonstrated with Quantitative-PCR (Q-PCR). The highest bacterial population abundance was detected for 1.45 g TOC L−1.d−1 and the important methanogenic community abundance for 2.07 g TOC L−1.d−1 may be related to the highest biogas production in this charge for an effluent salinity of 27.7 g NaCl L−1.

An integrated anaerobic system for on-site treatment of wastewater from food waste disposer.

In this study, an integrated system of siphon-driven self-agitated anaerobic reactor (SDSAR) and anaerobic fixed bed reactor (AFBR) was conducted for the treatment of wastewater from food waste disposer (FWD), and the effect of influent total solids (TS) concentration on the process performance was evaluated. When the influent TS concentration increased from 7.04 to 15.5g/L, the methane gas production rate increased from 0.45 to 0.92L-CH4/L/day. However, with the influent TS concentration of food waste (FW) further increased to 23.5g/L, a large amount of scum formed and accumulated in the SDSAR. According to the result of chemical oxygen demand (COD) recovery, the proportion of COD remained in the effluent at different TS concentrations was only around 2%. On the other hand, with an increase in TS concentration, the proportion of COD remained in the reactors increased significantly. Our results demonstrated that effluent from the integrated system can meet the water quality requirements recommended by Japan Sewage Works Association (JSWA) for wastewater from FWD. In addition, to enhance the process stability, the influent TS concentration should be maintained below 15.5g/L.

Potential Use of Locally Available Filter Media in a UAFB Reactor Coupled with Natural Treatment in Soybean Industry Wastewater Treatment

Many food industries in developing countries cannot afford proper wastewater treatment and directly discharge their wastewater into surface water bodies causing several problems such as aesthetical, health and environmental problems. A new approach for low-cost wastewater treatment which is reliable, allows nutrients and energy recovery should be promoted. One of the alternative wastewater treatment technologies is anaerobic wastewater treatment which offers a number of advantages such as low energy requirement, low production of sludge and the possibility of energy recovery. As one of the disadvantages of using anaerobic method is that the effluent usually does not meet the authority’s regulation to be discharged directly into water bodies, to further treat the effluent in order to meet the standard, the up flow anaerobic fixed-bed reactor will be coupled with a ‘natural treatment’. This paper presents preliminary results of a research which has the main goal to examine the of several locally available materials as packing media in UAFB reactor and the appropriate vegetations for constructed wetland and/or macrophyte pond. Additionally, potential energy recovery from soybean wastewater is also calculated.

Strategies to improve the biohydrogen production from cassava wastewater in fixed-bed reactors

The biological production of hydrogen from cassava starch wastewater (CSW) was evaluated in an anaerobic fixed-bed reactor (UAFBR). The assays were carried out to evaluate the effects of organic loading rate (OLR) increase and strategies of inoculation (AS – anaerobic sludge thermally treated and NF – naturally fermented cassava starch wastewater) on UAFBR performance. The OLR increase (10–20 g L−1 d−1) associated with hydraulic retention time (HRT) decrease (4–2 h) improved the volumetric hydrogen production rate (VHPR, from 229 to 550 mLH2.L−1.d−1), molar hydrogen flow rate (MHFR, from 1.0 to 2.5 mmolH2.h−1) and hydrogen yield (HY, from 0.2 to 0.3 molH2.mol−1Carb) from CSW due to increase in substrate availability. Both inoculation alternatives (AS and NF) were effective for the selection of acidogenic microorganisms, which demonstrates that NF could be considered a simple and economic alternative for the acquisition of inoculum for continuous acidogenic reactors. Hydrogen production decreased after 10 days of operation when the specific organic loading rate (SOLR) reached reduced values (<1 gCarb.g−1VSS.d−1), which impairs hydrogen production. For all assays, methane was present in the biogas after the 20th day of operation mainly due to biomass accumulation, which alters the biota of the reactor. Although many factors could influence the process performance in UAFBR for the production of biohydrogen, the accumulation of biomass have been pointed as the main factor in the determination of the production time, thus demanding the implementation of systematic practices to remove the excess of biomass to maintain the SOLR in levels adequate for hydrogen production.

Integrated upflow anaerobic fixed-bed and single-stage step-feed process for mainstream deammonification: A step further towards sustainable municipal wastewater reclamation

The high energy consumption and excessive waste activated sludge (WAS) production have become the major concerns on the municipal wastewater treatment with conventional biological processes. To tackle these emerging issues, this study demonstrated the feasibility of a novel process integrating an upflow anaerobic fixed-bed reactor (UAFBR) followed by a continuous step-feed reactor for mainstream deammonification towards improved energy efficiency, minimized sludge production and cost-effective ammonium removal. The results showed that 48.8% of the influent chemical oxygen demand (COD) was directly converted to methane gas in UAFBR with minimized sludge production, while 80% of total nitrogen (TN) was removed in the step-feed reactor. Mass balance on the step-feed reactor revealed that the oxic chambers contributed 51.6% of the removed ammonium oxidation to mainly nitrite, while the produced nitrite was immediately removed via anammox with the ammonium supplied by the step-feed in the following anoxic chambers where about 87.1% TN removal occurred. Moreover, it was found that sustainable repression of nitrite oxidizing bacteria (NOB) was achieved without compromising the activity of ammonia oxidizing bacteria (AOB). The anammox bacteria were effectively retained in the anoxic chambers and showed a high specific anammox activity of 0.42 g N/(g VSS·day). These suggest that the step-feed configuration can offer a feasible engineering option towards single-stage mainstream deammonification. It appears that the integrated process developed in this study sheds light on the possible way towards sustainable, energy self-sufficient municipal wastewater reclamation.

Feasibility of anaerobic packed and structured-bed reactors for sulfamethoxazole and ciprofloxacin removal from domestic sewage

This study assessed the applicability of fixed bed bioreactors in two configurations - anaerobic structured bed reactor (ASBR) and anaerobic packed bed reactor (APBR) - in the removal of Sulfamethoxazole (SMX) and Ciprofloxacin (CIP), two antibiotics frequently detected in sanitary sewage. The problem of these pharmaceuticals as emerging contaminants in conventional sewage treatment systems is mainly because they encourage the development and spread of resistance genes in bacteria. Both reactors had similar performances, and the antibiotics were highly removed - APBR: 85 ± 10% for SMX and 81 ± 16% for CIP; ASBR: 83 ± 12% for SMX and 81 ± 15% for CIP. The ASBR showed to be potentially more feasible in operating and economic terms compared to the APBR, as the former presents a smaller amount of support material in the bed. SMX was completely biotransformed, while the influence of the sorption mechanism was observed for CIP, as its presence was detected sorbed onto biomass throughout the reaction bed of the reactors, with a partition coefficient (log KD) of around 2.8 L·kg−1TSS. The degradation kinetics of the pharmaceuticals were fitted using a first-order kinetic model, whereby the reactors behaved as plug flow ones, indicating the possibility of optimizing the operation for a hydraulic retention time of 6 h. The removal kinetics was more favorable for CIP (higher apparent constant kinetic - kCIPapp > kSMXapp), since its biodegradation is linked to the biomass, which is more concentrated in the bed bottom layer. The experimental results showed the potential of anaerobic fixed bed reactors in removing environmentally relevant concentrations of SMX and CIP found in sewage.