Fixed-film Reactor Research Articles

Dynamics of sulfate reduction in the thermophilic dark fermentation of sugarcane vinasse: A biohydrogen-independent approach targeting enhanced bioenergy production

Dark fermentation (DF) systems usually exploit bioH2 production aiming to improve the energetic potential (EP) of anaerobic digestion (AD) schemes. In the case of sulfate-rich substrates, the versatility of fermentative consortia may favor the establishment of sulfidogenic conditions, minimizing/eliminating the competition between sulfate-reducing bacteria (SRB) and methanogens in the sequential stage and providing sulfide-free biogas. This study details the establishment of sulfidogenesis on the thermophilic DF of sugarcane vinasse in a continuous polyurethane-filled fixed-film reactor, also estimating the EP for vinasses according to different AD-related approaches. High sodium levels naturally stimulated SRB by maintaining high pH values (> 6.0), whilst NaHCO3 dosing was required when natural buffering conditions were not maintained. High acetate (~ 3 g-COD L−1) and COD/sulfate ratio (> 25.0) levels indicated a high-quality substrate for further methanogenesis. High butyrate concentrations (~11 g-COD L−1) coupled to caproate detection indicated the occurrence of chain elongation processes, leading to low bioH2 production levels (<400 NmL-H2 L−1 d−1). However, estimates indicated 12.2%- and 51.7%-increases in the methane-based EP (MJ m−3) of sulfate-free fermented vinasse (216.72) relative to sulfate-rich fermented (193.10) and fresh (142.88) vinasses. Hence, the ultimate approach for maximizing bioenergy production from sugarcane vinasse is detailed in this study.

Biohydrogen-producing from bottom to top? Quali-quantitative characterization of thermophilic fermentative consortia reveals microbial roles in an upflow fixed-film reactor

Understanding specificities of biohydrogen (bioH2)-producing systems is a key factor to enable efficient energetic exploitation of organic substrates in dark fermentation systems. The use of fixed-film reactors has been pointed as a determining approach to enhance bioH2 evolution due to maintaining high cell densities within reactors. However, limiting substrate availability by excess cell accumulation has been associated with low hydrogenogenic activity levels due to stimulating bioH2-consuming or non-producing pathways. A compartmentalized assessment was used to discover the dynamics of substrate conversion, cell retention patterns and the microbial characterization in different zones of a thermophilic (55 °C) molasses-fed fixed-film reactor under an organic loading rate of 20.0 kg-COD m−3 d−1. Results indicated that microbial populations (e.g. Thermoanaerobacterium genus) in the basal portion of the reactor governed bioH2 production by acetic- and butyric-type fermentation from sugars so that localized substrate availability (3.71 ± 1.13 g-COD g−1VSS d−1) reached favorable levels for bioH2-producing populations. Lactate production by the Janthinobacterium genus occurred only as a secondary metabolic pathway in the bed-region, in which complementary bioH2 production by the co-fermentation of acetate and lactate (also by Thermoanaerobacterium genus) was identified. The obtained results provide insights to manage the operation, as well as the design of acidogenic systems, indicating where and why bioH2-producing populations prevail in fixed-film reactors.

Two-Stage Process by Bioelectrochemical Preprocessing/Conductive Carrier Filling Is Applied to Wastewater/Waste Treatment: Enhanced Methane Production from Cellulose Using a Bioelectrochemical System and a Fixed Film Reactor

Two-Stage Process by Bioelectrochemical Preprocessing/Conductive Carrier Filling Is Applied to Wastewater/Waste Treatment: Enhanced Methane Production from Cellulose Using a Bioelectrochemical System and a Fixed Film Reactor

Evaluation of various waste substrates for biofilm formation and subsequent use in aerobic packed-bed reactor for secondary treatment of domestic wastewater.

Immobilization of bacterial cells on suitable substrates is of utmost importance in the secondary treatment of wastewater using fixed-film reactors. Therefore, screening of efficient and cheaper materials for bacterial surface immobilization was carried out. Eleven waste materials were used as substrates, packed in a column, and bacterial surface immobilization was carried out using cow dung slurry/MLSS mixture. All the chosen substrates were screened for bacterial immobilization/biofilm formation by standard bacterial enumeration technique. The substrate with the highest biofilm-forming ability was used for secondary treatment of raw domestic wastewater. The results showed that high-density polyethylene and aluminium foil sheets have poor immobilizing characteristics with 2.2 × 108 and 2.4 × 108CFU/cm2 respectively, whereas jute fibres were observed to be the most efficient among the substrates with 5.1 × 1023CFU/cm2. The column packed with jute fibres was used for wastewater treatment. Various physico-chemical parameters were analyzed before and after treatment and there was a significant reduction in major parameters after treatment. The bacteria-immobilized jute fibres showed maximum immobilization potential and were highly efficient in wastewater treatment, and therefore these findings offer immense promise in the synthesis of composite polymers for bacterial immobilization and subsequent secondary treatment.

Start-up study of biohydrogen production from palm oil mill effluent in a lab-scale up-flow anaerobic sludge blanket fixed-film reactor

A start-up study of lab-scale up-flow anaerobic sludge blanket fixed-film reactor (UASFF) was conducted to produce biohydrogen from palm oil mill effluent (POME). The reactor was fed with POME at different hydraulic retention time (HRT) and organic loading rate (OLR) to obtain the optimum fermentation time for maximum hydrogen yield (HY). The results showed the HY, volumetric hydrogen production rate (VHPR), and COD removal of 0.5–1.1 L H2/g CODconsumed, 1.98–4.1 L H2 L−1 day−1, and 33.4–38.5%, respectively. The characteristic study on POME particles was analyzed by particle size distribution (PSD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX). The microbial Shannon and Simpson diversity indices and Principal Component Analysis assessed the alpha and beta diversity, respectively. The results indicated the change of bacterial community diversity over the operation, in which Clostridium sensu stricto 1 and Lactobacillus species were contributed to hydrogen fermentation.

Enhanced methane production from cellulose using a two-stage process involving a bioelectrochemical system and a fixed film reactor

BackgroundIt is desirable to improve the anaerobic digestion processes of recalcitrant materials, such as cellulose. Enhancement of methane (CH4) production from organic molecules was previously accomplished through coupling a bioelectrochemical system (BES); however, scaling-up BES-based production is difficult. Here, we developed a two-stage process consisting of a BES using low-cost and low-reactive carbon sheets as the cathode and anode, and a fixed film reactor (FFR) containing conductive material, i.e., carbon fiber textiles (CFTs) (:BES → FFR). By controlling the cathodic current at 2.7 μA/cm2 without abiotic H2 production, the three-electrode BES system was operated to mimic a microbial electrolysis cell.ResultsThe thermophilic BES (inlet pH: 6.1) and FFR (inlet pH: 7.5) were operated using hydraulic retention times (HRTs) of 2.5 and 4.2 days, respectively, corresponding to a cellulose load of 3555.6 mg-carbon (C)/(L day). The BES → FFR process achieved a higher CH4 yield (37.5%) with 52.8 vol% CH4 in the product gas compared to the non-bioelectrochemical system (NBES) → FFR process, which showed a CH4 yield of 22.1% with 46.8 vol% CH4. The CH4 production rate (67.5 mM/day) obtained with the BER → FFR process was much higher than that obtained using electrochemical methanogenesis (0.27 mM/day). Application of the electrochemical system or CFTs improved the yields of CH4 with the NBES → FFR or BES → non-fixed film reactor process, respectively. Meta 16S rRNA sequencing revealed that putative cellulolytic bacteria (identified as Clostridium species) were present in the BES and NBES, and followed (BES→ and NBES→) FFR. Notably, H2-consuming methanogens, Methanobacterium sp. and Methanosarcina sp., showed increased relative abundances in the suspended fraction and attached fraction of (BES→) FFR, respectively, compared to that of (NBES→) FFR, although these methanogens were observed at trace levels in the BES and NBES.ConclusionsThese results indicate that bioelectrochemical preprocessing at a low current effectively induces interspecies H2 transfer in the FFR with conductive material. Sufficient electrochemical preprocessing was observed using a relatively short HRT. This type of two-stage process, BES → FFR, is useful for stabilization and improvement of the biogas (CH4) production from cellulosic material, and our results imply that the two-stage system developed here may be useful with other recalcitrant materials.

Microbial population selection in integrated fixed-film sequencing batch reactors operated with different lengths of oxic and anoxic conditions

BNR granules rich in amyloid adhesins and denitrifying bacteria were formed in the SBRs that were operated with extended anoxic conditions.

Effect of HRT on biogas yield in treating dairy industry wastewater using Upflow Anaerobic Sludge Fixed Film reactor

Abstract Nowadays dairy and milk-based merchandise has become most essential and vital role in day-after-day lifetime of human. The milk undergoes varied process in dairy farm industries to supply different dairy products. More water and different chemicals are needed during a dairy unit. The amount of water employed in a dairy trade depends upon the supply of water, process technique and sort of flow. The wastewater after every step of process is discharged into either the natural water bodies or to the surroundings that alters the ecological balance. This study illustrates the impact of hormone replacement therapy on performance of work Upflow Anaerobic Sludge Fixed Film (UASFF) reactor on treatment of dairy industry. The UASFF reactor was designed for an efficient volume of 0.013 m3 with Fujino Spirals as packing media at the highest of reactor and operated underneath mesophilic condition. when startup amount, the reactor was operated with HRTs of 30, 24, 18, 12 and 6hr for the common inflowing COD concentrations of 8500 mg/L, 10000 mg/L, 11500 mg/L, 13000 mg/L and 14500 mg/L severally. The results showed that the utmost biogas yield efficiencies were within the vary of 0.162–0.505 m3/kg COD at inflowing concentration of 8500 mg/L and 14500 mg/L severally.

Heavy metals and antibiotics resistance of bacteria isolated from Marchica lagoon: biodegradation of anthracene on submerged aerated fixed bed reactor

ABSTRACT Heavy metals resistant and polyaromatic hydrocarbon (PAH)-degrading bacteria isolated from Marchica lagoon. Six isolates, Pseudomonas putida, Orchobactrum antropi, Staphylococus epidermidis, Brevundimonas diminuta, Serratia ficaria and Bacillus anthracis were characterized on the basis of biochemical and 16S rDNA. The strains that showed high resistance to heavy metals were also studied for their antibiotics resistance and growth kinetics. The minimal inhibitory concentrations (MIC) of metals at variant concentrations (10-38 mM) were determined in liquid and solid medium. Strains were showed an extreme resistance against metals with the MIC values of Cu (9 mM), Cd (6.25 mM), Cr (2.5 mM), Ag (0,625), and Hg (0,156). Furthermore, growth rates were decreased in the presence of metals (compared to the control). The anthracene elimination from synthetic wastewater was determined in a submerged aerobic fixed-film reactor. Optimal conditions for bacterium growth and biodegradation of anthracene are determined as: temperature of 37 °C, pH 7, and initial anthracene concentration of 20 mg/l. It emerged that at anthracene concentrations 5-40 mg/l, COD removal efficiency were 84.62%; 90.62%; 91.36% and 71.4% respectively.

AEROBIC TREATMENT OF WASTEWATER USING HYBRID SYSTEM. (Dept. C ( Public Works ) )

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Assessing the impact of synthetic estrogen on the microbiome of aerated submerged fixed-film reactors simulating tertiary sewage treatment and isolation of estrogen-degrading consortium

17α-ethinylestradiol (EE2) is a synthetic estrogen that can cause harmful effects on animals, such as male feminization and infertility. However, the impact of the EE2 contamination on microbial communities and the potential role of bacterial strains as bioremediation agents are underexplored. The aim of this work was to evaluate the impact of EE2 on the microbial community dynamics of aerated submerged fixed-film reactors (ASFFR) simulating a polishing step downstream of a secondary sewage treatment. For this purpose, the reactors were fed with a synthetic medium with low COD content (around 50 mg l−1), supplemented (reactor H) or not (reactor C) with 1 μg l−1 of EE2. Sludge samples were periodically collected during the bioreactors operation to assess the bacterial profile over time by 16S rRNA gene amplicon sequencing or by bacterial isolation using culture-dependent approach. The results revealed that the most abundant phyla in both reactors were Proteobacteria and Bacteroidetes. At genus level, Chitinophagaceae, Nitrosomonas and Bdellovibrio predominated. Significant effects caused by EE2 treatment and bioreactors operating time were observed by non-metric multidimensional scaling. Therefore, even at low concentrations as 1 μg l−1, EE2 is capable of influencing the bioreactor microbiome. Culture-dependent methods showed that six bacterial isolates, closely related to Pseudomonas and Acinetobacter genera, could grow on EE2 as the sole carbon source under aerobic conditions. These organisms may potentially be used for the assembly of an EE2-degrading bacterial consortium and further exploited for bioremediation applications, including tertiary sewage treatment to remove hormone-related compounds not metabolized in secondary depuration stages.

Removal of High Levels of Cyanide and COD from Cassava Industrial Wastewater by a Fixed-Film Sequencing Batch Reactor

The fixed-film sequencing batch reactor, or F-SBR, was developed to treat high organic compound levels and toxic cyanide concentrations in cassava wastewater. The performance of the F-SBR was compared with that of a conventional sequencing batch reactor, or SBR, that was operated with organic compound contents of 16,266.67–26,666 mg COD/L and 132.92–252.66 mg CN−/L. The cyanide and chemical oxygen demand removal efficiencies of the conventional SBR system were 42.61% and 36.83%, respectively, while those of the F-SBR were 77.95% and 74.43%, respectively; the cyanide removal efficiency reached 95.45% when the hydraulic retention time was increased to 5 days, and the F-SBR was very effective for the complete removal of cyanide when the hydraulic retention time was increased to 10 days. This effectiveness was similar to the effectiveness of chemical oxygen demand removal, which reached 40–78% efficiency with the F-SBR system. These results showed that the immobilization of cyanide-degrading bacteria such as Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2 carried out with a polypropylene ring in a fixed-film aerobic system enhanced the performance of the reactor and can be successfully applied for cyanide and chemical oxygen demand removal from industrial wastewater with high cyanide and chemical oxygen demand concentrations. This study may provide a promising alternative technique that reduces economic operation costs in solving wastewater contamination problems.

Kinetic evaluation of a partially packed upflow anaerobic fixed film reactor treating low-strength synthetic rubber wastewater

A bench-scale model of a partially packed upflow anaerobic fixed film (UAF) reactor was set up and operated at five different hydraulic retention times (HRTs) of (17, 14, 10, 8, and 5) days. The reactor was fed with synthetic rubber wastewater consisting of a chemical oxygen demand (COD) concentration of 6355–6735 mg/L. The results were analyzed using the Monod model, the Modified Stover-Kincannon models, and the Grau Second-Order Model. The Grau Second-Order model was found to best fit the experimental data. The biokinetic constant values, namely the growth yield coefficient (Y) and the endogenous coefficient (Kd) were 0.027 g VSS/g COD and 0.1705 d−1, respectively. The half-saturation constant (Ks) and maximum substrate utilization rate (K) returned values of 84.1 mg/L and 0.371 d−1, respectively, whereas the maximum specific growth rate of the microorganism (μmax) was 0.011 d−1. The constants, Umax and KB, of the Stover-Kincannon model produced values of 6.57 g/L/d and 6.31 g/L/d, respectively. Meanwhile, the average second-order substrate removal rate, ks(2), was 105 d−1. These models gave high correlation coefficients with the value of R2 = 80–99% and these indicated that these models can be used in designing UAF reactor consequently predicting the behaviour of the reactor.

A bio-kinetic study on liquid-to-biogas transfer in an up-flow anaerobic sludge fixed film reactor in the treatment of sago wastewater

A bio-kinetic study on liquid-to-biogas transfer in an up-flow anaerobic sludge fixed film reactor in the treatment of sago wastewater

Identification of Potentially active Methanogenic Population for Degradation of Organic Substances in UASFFR for Treating Sago Wastewater

Anaerobic digestion process is the best method for treating industrial wastewater with dynamic relationship between microorganisms. The objective of this research work is to assess the microbial population that coordinates with anaerobic codigestion of biomass cultivated on sago wastewater. An upflow anaerobic sludge fixed film reactor was used to achieve high rates of microbial decomposition. The bacterial colonies were counted and predominant culture was streaked in newer sterile nutrient agar plate. The predominant culture was subjected to molecular identification using 16S rRNA gene sequencing and Gram’s staining. Isolated organism chryseomicrobium species and the organism are identified as Chryseomicrobium palamuruense by using the biochemical and 16S rRNA gene sequencing.

Design of a continuous fixed film photocatalytic reactor based on Bi2WO6/ZnFe2O4 magnetic photocatalyst and application in tetracycline degradation

A kind of continuous magnetic fixed-film reactor was designed and applied in tetracycline degradation based on the Bi2WO6/ZnFe2O4 magnetic photocatalyst. The effects of light intensity, initial TC concentration and HRT on the photocatalytic effect were investigated. At the pollutant concentration of 51.58 mg/L, light intensity of 3.20×105 lux and HRT of 94 min, the TC removal rate in the reactor was enhanced to above 90% and maximized to 94.05%. From the different pollutant concentrations, the specific outflow criterion could be achieved by regulating the HRT within a certain range, so as to maximize the reactor use efficiency. Compared with conventional fixed-film reactors, the new reactor had larger reaction contact area and avoided the defect of catalyst shedding.

Treatment of low strength wastewater using compact submerged aerobic fixed film (SAFF) reactor filled with high specific surface area synthetic media.

Studies on laboratory-scale submerged aerobic fixed film reactor (SAFF) packed with synthetic media having specific surface area of 165 m2/m3 with a void volume of 89% were carried out to assess its performance under various organic loading rates (OLR) and hydraulic retention times (HRT). Synthetic wastewater having chemical oxygen demand (COD) and biochemical oxygen demand (BOD) of 400 ± 10% and 210 ± 10% mg/L respectively was fed and the reactor was subjected to OLRs ranging from 0.37 to 1.26 kg COD/m3.d. It was observed that steady sloughing of biofilm occurs within the SAFF reactor all the times and average concentration of sloughed biomass in the effluent was 26 mg/L. The COD and BOD removal efficiencies varied between 85 and 89% and 86 to 94%, respectively. The kinetic studies demonstrated that SAFF reactor followed Stover-Kincannon and Grau models, with high correlation coefficients (R2) of 0.9977 and 0.9916, respectively. Thus, the values of kinetic coefficients such as maximum substrate utilization rate, Umax = 64.1 g/(L.d); saturation value constant, KB = 72.31 g/(L.d) and Grau second-order substrate removal rate constant, Ks = 2.44 day-1 can be useful to develop and design large scale SAFF reactors. Finally, the study reveals that the optimum range for OLR can vary within 0.68-0.94 kg COD/m3.d.

High-rate anaerobic treatment of digestate using fixed film reactors

The effluent stream of the anaerobic digestion processes, the digestate, accommodates high residual organic content that needs to be further treated before discharge. Anaerobic treatment of digestate would not only reduce the residual organic compounds in digestate but also has a potential to capture the associated biogas. High-rate anaerobic reactor configurations can treat the waste streams using lower hydraulic retention times which requires less footprint opposed to the conventional completely stirred tank reactors. This study investigated the high-rate anaerobic treatment performance and the associated biogas capture from the digestate of a manure mixture composed of 90% laying hen and 10% cattle manures in fixed-film reactors. The results indicated that it was possible to reduce total chemical oxygen demand content of the digestate by 57–62% in 1.3–1.4 days of hydraulic retention time. The corresponding biogas yields obtained were in the range of 0.395–0.430 Lbiogas/g VSadded which were found to be comparable to many raw feedstocks. Moreover, significant total phosphorus reduction (36–47%) and greenhouse gas capture (over 14.5–18.1 tCO2e/d per m3 digestate) were also recorded in the anaerobic fixed-film reactors.

Uranium (VI) reduction in a fixed-film reactor by a bacterial consortium isolated from uranium mining tailing heaps

Biological uranium (VI) reduction was investigated using a mixed-culture of U(VI) reducing bacteria isolated from tailing dumps at an abandoned uranium mine in Pharaborwa (Limpopo Province, South Africa). A fixed-film reactor was used in the investigation, whereby the reactor was operated in the up-flow mode under fully submerged conditions at a recirculation ratio of, Qin/QR = 20. The performance of the bioreactor was evaluated over a range of influent U(VI) concentrations [75–100 mg U(VI)/L] and 24 h hydraulic retention time [HRT]. Complete U(VI) removal was observed in phases with 30–85 mg/L influent U(VI). When influent U(VI) was increased to 100 mg/L, approximately 60% U(VI) removal was achieved. The oxidation states of reduced uranium species were determined by Scanning and Transmission Electron Microscopy followed by X-ray Diffractometer (SEM/TEM-XRD). Earlier studies in batch systems showed that U(VI) was non-toxic to U(VI) reducing organisms at concentrations up to 400 mg/L. The decrease in U(VI) removal efficiency observed in the fixed-film reactor after 42 days was therefore attributed to the accumulation of U(IV) hydroxide precipitates in the reactor. Genetic identification using the 16S rRNA gene sequence analysis showed that the species Kocuria turfanensis, Arthrobacter creatinolyticus, Bacillus licheniformis, and Microbacterium aerolatum survived from the original cultures. The feasibility of continuous removal of U(VI) in an inoculated indigenous culture system was thus demonstrated.

Clogging limitation of nitrifying biofilters: BiostyrDuo® process study

Abstract The biological conventional removal of nitrogen is achieved through nitrification and denitrification steps using several types of technologies, including fixed-film reactors. This type of technology allows the nitrifying bacteria to grow on a media that remains inside the reactor. This process requires tight control and is known to progressively clog during treatment as the filtered particles accumulate and biofilm grows on the media. Thus, clogging management is generally considered as a key factor in biofiltration. So, increasing the filtration time and reducing the number of backwashes are possible ways of achieving a more efficient nitrification step. The objective of the work presented here is to verify the influence of a media, named K5, added to the Biostyr® beads inside a biofilter. With a greater density than Biostyr® beads, this media stays at the bottom of the biofilter and improves operating conditions, reducing both the headloss during filtration time and the number of backwashes. The addition of such media in biofilters may reduce significantly the energy consumption of the process and the risk of hydraulic short-circuiting while limiting biofilter clogging.