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A high rate upflow anaerobic polyfoam‐based bioreactor (UAPB) was developed for lab‐scale in‐situ biogas upgrading by H2 injection. The reactor, with a volume of 440 mL, was fed with synthetic wastewater at an organic loading rate (OLR) of 3.5 g COD/L·day and a hydraulic retention time (HRT) of 7.33 h. The use of a porous diffuser, alongside high gas recirculation, led to a higher H2 liquid mass transfer, and subsequently to a better uptake for high CH4 content of 56% (starting from 26%). Our attempts to optimize both operational parameters (H2 flow rate and gas recirculation ratio, which is the total flow rate of recirculated gas over the total outlet of gas flow rate) were not initially successful, however, at a very high recirculation ratio (32) and flow rate (54 mL/h), a significant improvement of the hydrogen consumption was achieved. These operational conditions have in turn driven the methanogenic community toward the dominance of Methanosaetaceae, which out‐competed Methanosarcinaceae. Nevertheless, highly stable methane production rates of 1.4–1.9 L CH4/Lreactor.day were observed despite the methanogenic turnover. During the different applied operational conditions, the bacterial community was especially impacted, resulting in substantial shifts of taxonomic groups. Notably, Aeromonadaceae was the only bacterial group positively correlated with increasing hydrogen consumption rates. The capacity of Aeromonadaceae to extracellularly donate electrons suggests that direct interspecies electron transfer (DIET) enhanced biogas upgrading. Overall, the proposed innovative biological in‐situ biogas upgrading technology using the UAPB configuration shows promising results for stable, simple, and effective biological biogas upgrading. [ABSTRACT FROM AUTHOR]

BACKGROUND The use of methane as electron donor for denitrification addresses nitrogen removal in anaerobic effluents and can help to abate greenhouse gas emissions from wastewater treatment plants. However, applicable rates of methanotrophic denitrification were only reached under temperature controlled conditions, and in membrane bioreactors, which are not widely available in low‐income countries. In this study, polyurethane foam was used as support media in an up‐flow fixed structured bed reactor (Up‐FSBR). Methane was provided as the sole electron donor and carbon source to the Up‐FSBR, fed with synthetic medium mimicking nitrified sewage pre‐treated anaerobically and operated without temperature control or previous medium sterilization. RESULTS: The denitrification rate was 16.7 ± 6.9 mg N·day−1 and the average efficiency was 42.7 ± 14.6%. Data dispersion is linked to the operation conditions, such as temperature variation that ranged up to 18 °C in a 24 h period. The temperature variation caused a swallow in the metallic valves used in the methane input device, leading to a high fluctuation in methane availability and bubble size, influencing gas–liquid transfer. 16S rDNA sequencing revealed a complex interplay among aerobic methane oxidizers (10.8% of relative abundance), non‐methanotrophic methylotrophs (7.0% RA), heterotrophic denitrifiers (14.3% RA), and microorganisms affiliated with the archaeal Methanosarcinales (13.2%). CONCLUSIONS: The Up‐FSBR is a promising alternative for methanotrophic denitrification. The operation challenges are linked with methane input rather than with the reactor configuration. The Up‐FSBR was efficient in selecting a microbial community that is capable of performing methane oxidation and heterotrophic denitrification. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Biomass samples from a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) were analyzed to investigate the bacterial community shift along with the changes in the C/N ratio. The C/N ratios tested were 7.6 ± 1.0 (LNC) and 2.9 ± 0.4 (HNC). The massive sequencing analyses revealed that the microbial community adjusted itself to different organic and nitrogenous applied loads, with no harm to reactor performance regarding COD and Total-N removal. Under LNC, conventional nitrification and heterotrophic denitrification steered the process, as indicated by the detection of microorganisms affiliated with Nitrosomonadaceae, Nitrospiraceae, and Rhodocyclaceae families. However, under HNC, the C/N ratio strongly affected the microbial community, resulting in the prevalence of members of Saprospiraceae, Chitinophagaceae, Xanthomonadaceae, Comamonadaceae, Bacillaceae, and Planctomycetaceae. These families include bacteria capable of using organic matter derived from cell lysis, ammonia-oxidizers under low DO, heterotrophic nitrifiers–aerobic denitrifiers, and non-isolated strains of Anammox. The DO profile confirmed that the stratification in aerobic, anoxic, and anaerobic zones enabled the establishment of different nitrogen degradation pathways, including the Anammox. [ABSTRACT FROM AUTHOR]

• Se(VI) removal was investigated in continuous-flow bioreactors packed with strain TB immobilized by gel beads. • Se(VI) removal efficiency ranged from 53.70 %–98.67 % under nine steady states. • The reduction product, Se(0), was largely retained in the reactor. • Selenium removal was affected by the HRT and the bed height of the reactor but not the influent Se(VI) concentration. • Four biokinetic parameters were optimized by a mathematical model using steady-state data. Selenium at high levels may cause adverse health effects on human beings and endanger aquatic lives due to its toxicity. Se(VI) reduction in continuous-flow reactors packed with Shigella fergusonii strain TB42616 immobilized by Ca2+-alginate gel beads was investigated under various hydraulic retention times (HRT) and influent Se(VI) concentrations. Removal efficiency up to 98.8 % was achieved after 96 days operation under an HRT of 5 days and an influent Se(VI) concentration of 400 mg/L. The results showed that the overall selenium removal efficiency was affected by the HRT and the bed height of the reactor but not the influent Se(VI) concentration. The steady-state data were analyzed using a mathematical model and Monod-type kinetics. Biokinetic parameters of half-velocity constants and maximum specific reduction rates were optimized using steady-state data obtained under a range of HRTs (0.73–5.0 days) at a constant influent Se(VI) concentration of 50 mg/L. The model was validated using steady-state data obtained under influent Se(VI) concentrations ranging from 10 to 400 mg/L while maintaining the HRT at 5.0 days. The high correlation coefficients between model calculated Se(VI) and Se(IV) concentrations and the experimental data indicate that the model is robust to predict the performance of the continuous-flow bioreactor. [ABSTRACT FROM AUTHOR]

In the present work, the biodegradation of natural rubber by means of three filamentous fungi, two Alternaria alternata strains (ANR and BNR) and Penicillium chrysogenum, is reported. The biodegradation process has been optimized in Erlenmeyer flasks and then scaled-up in Fernbach flasks. The biodegradation was performed in stationary liquid cultures with biomass immobilized on ceramic Berl saddles. In the presence of NR as the only carbon source, the maximum value of enzyme activity (0.242 IU/L) was reached at 41 days of incubation and at the end of incubation time, 65 days, a 2% weight loss of NR was detected. In Fernbach flasks, the maximum peroxidase activity value was doubled (0.500 IU/L) and reached earlier, after 6 days. In the same incubation time, a better biodegradation performance (4.3%) was obtained. Moreover, the application of a double biodegradation step allowed to obtain higher biodegradation percentage, 6.8%. Among the different tested microorganisms, A. alternata BNR showed the best biodegradation potentiality in terms of enzyme production and NR degradation. On the basis of the results obtained in liquid cultures, A. alternata BNR is currently applied in a lab-scale microcosm study which has to be considered the preliminary step of an in-field biodegradation process. [ABSTRACT FROM AUTHOR]

The main objective of wastewater treatment is to remove carbon and other nutrients from municipal and industrial effluents in order to protect the environment and human health. Typical wastewater treatment is usually achieved by a combination of physical, chemical and biological methods. In this work, municipal wastewater was depurated using chemically enhanced primary treatment (CEPT) in combination with a pilot-scale trickling filter. Lab scale experiments (Jar-tests) were carried out in order to determine the optimum dosage of chemicals. Selection criteria were the organic load removal efficiency and the low operational cost. Coagulation-flocculation process was conducted through polyaluminium chloride (PAC) and the cationic polyelectrolyte (Zetag 8180) addition. By combining CEPT and trickling filter, tCOD (total Chemical Oxygen Demand), sCOD (soluble Chemical Oxygen Demand), BOD5 (5-day Biochemical Oxygen Demand), NH4+-N, TSS (Total Suspended Solids), VSS (Volatile Suspended Solids) and PO43−-P removal efficiencies were estimated to be 89, 82, 93, 60, 96, 96 and 78%, respectively. It is concluded that biological filtration contributed significantly in nutrients removal processes. Moreover, the obtained effluent was low in carbon and rich in nitrogen, which can be applied for restricted irrigation after disinfection, complying with the discharge limits set in the Greek Joint Ministerial Decree 145116/2011. [ABSTRACT FROM AUTHOR]

A number of bacteria and fungi are known to degrade tannins. In this study, the efficiency of the white-rot fungus, Bjerkandera adusta MUT 2295, was evaluated for the treatment of a synthetic solution prepared with tannic acid. Tests were performed in continuously fed, bench-scale, packed-bed reactors, operated under non-sterile conditions with biomass immobilized within PolyUrethane Foam cubes (PUFs). The main parameters monitored to evaluate the process efficiency were: soluble Chemical Oxygen Demand (sCOD), Total Organic Carbon (TOC) removal, and activities. of Tannase and Lignin Peroxidase. At the end of the process, additional parameters were evaluated, including the increase of fungal dry weight and the presence of ergosterol. The reactor was operative for 210 days, with maximum sCOD and TOC removal of 81% and 73%, respectively. The reduction of sCOD and TOC were positively correlated with the detection of Tannase and Lignin Peroxidase (LiP) activities. Increases in biomass within the PUF cubes was associated with increases in ergosterol concentrations. This study proved that the fungal-based system tested was efficient for the degradation of tannic acid over a period of time, and under non-sterile conditions. Image 1 • Tannic acid was treated in a continuously-fed reactor using a white-rot fungus. • The reactor was operated for 210 days under non-sterile conditions. • Depletion of the stable recalcitrant compound was achieved after 164 days. • The process was associated with the detection of oxidative enzymes. • Fungal treatment for remediation of tannic acid was demonstrated to be feasible. [ABSTRACT FROM AUTHOR]

Methanotrophy has become a promising process for biotechnological applications. The initial goal of this study was to investigate methanotrophic denitrification as an alternative to nitrogen removal in waters that have a low organic content. Sequencing batch reactors (SBRs) were inoculated with a blend of marine and mangrove sediments (Sed-SBR), or anaerobic granular sludge from a upflow anaerobic sludge bed reactor treating poultry slaughterhouse wastewater (AnS-SBR) immobilized in polyurethane foams under anoxic conditions. Methane was provided as the sole external electron donor and organic carbon source. Methane supported denitrification to a small extent (<2.0 mg N.g total volatile solids−1 d−1) and supported biomass growth for the AnS-SBR in 10% of the initial volatile suspended solids. DNA sequencing of initial inocula showed high richness and low dominance for Sed inoculum, while the most abundant microorganisms in AnS inoculum were chemoorganotrophs typically found in anaerobic environments. In initial inocula, reads belonging to methanotrophs accounted for <0.5% of the sample. In enriched samples, aerobic methanotrophic organisms (especially those affiliated with the genera Methylomonas) were the only organisms found, which are capable of oxidizing methane, accounting for nearly 5% of the relative abundance, while there was a decay of initially abundant organisms. Various heterotrophic groups were also identified, indicating that methanotrophs allowed establishment of a diverse community, even under adverse environmental conditions. These results suggest aerobic methanotrophs are versatile under anoxic conditions and that it is a widespread phenomenon, since it was observed for both inocula tested. [ABSTRACT FROM AUTHOR]

Chemical oxidation of pyrite and chalcopyrite by ferric sulfate (Fe2(SO4)3) solution and biogenic ferric iron obtained by mixed culture of isolated thermotolerant Acidithiobacillus sp. 13Zn and Leptospirilum ferriphilum CC immobilized on natural carrierszeolite and shungite was studied. Oxidation rate of sulfide minerals was estimated by the decrease of Fe3+ (oxidant) and increase of Fe2+ ions in the solution. It was revealed that chemical oxidation of chalcopyrite by biogenic ferric iron occurred 2-3 times more intensively than that by Fe2(SO4)3 solution. Pyrite oxidation rate by biogenic ferric iron was twice higher than that by chemical ferric iron solution. It was shown that the treatment of pyrite and chalcopyrite by biogenic ferric iron allows to increase on average 1.5 - 2 times the bioleaching of iron from pyrite and iron and copper from chalcopyrite by the associations of iron and sulfur oxidizing bacteria. [ABSTRACT FROM AUTHOR]

A novel biomass/polymer composite was fabricated by embedding Thamnidium elegans cells in acrylic network of p(3-Methoxyprophyl)acrylamide p(MPA) enriched with 2-Akrylamido-2-methyl-1-propane sulfonic acid (AMPS). Cd(II) retention potential of hydrogel (p(MPA-co-AMPS)) increased by 20.66% times after this enrichment. The gel matrix could be effectively entrapped the biomass and resulting sorbent applied to remove Cd(II) from water in batch and continuous modes. The main physico-chemical parameters are discussed in addition to characterization, regeneration and application studies of the suggested sorbent. Equilibrium occurred within 30 min and Langmuir model predicted the equilibrium data. Kinetics of Cd(II) removal onto immobilized biomass is modeled using the pseudo-second-order rate equation. Maximum monolayer sorption capacity was estimated to be 123.76 mg g −1 at 25 °C. Designed composite was successfully applied for the removal of Cd(II) from industrial wastewater. EDTA and HNO 3 can be efficiently used for Cd(II) recovery and composite sorbent recycled for at least 12 cycles with nearly stable sorption performance. [ABSTRACT FROM AUTHOR]

The effects of dry biomass density in cryogel beads, shaking speed and initial concentration ratio of phenol to 4-chlorophenol (4-CP) on the bioregeneration efficiencies of binary phenol and 4-CP-loaded granular activated carbon (GAC) for phenol and 4-CP, respectively, were investigated under the simultaneous adsorption and biodegradation approach. The results revealed higher bioregeneration efficiencies of binary-loaded GAC for phenol and 4-CP at higher dry biomass density but moderate shaking speed. The optimum dry biomass density in cryogel beads and shaking speed for use in bioregeneration were found to be 0.01 g/mL and 250 rpm, respectively. With respect to the initial phenol to 4-CP concentration ratio, the bioregeneration efficiencies were lower under increasing phenol and 4-CP initial concentrations, respectively, with the effect being more conspicuous under increasing 4-CP concentration. Higher bioregeneration efficiencies were achieved with the use of immobilized rather than suspended biomasses. [ABSTRACT FROM AUTHOR]

Among various bioreactors examined in anaerobic digestion and dark fermentation, UASB bioreactor has shown to be a promising alternative. However, mass transfer resistance and biomass washout have been the issues that reported as draw backs of the granular system in the literature. Another problem associated with such a system is its long start-up period as a result of biomass washout and long microbial granulation stage. In this paper, the results obtained from an UASFF bioreactor in methane (AD process) and hydrogen (DF process) production from POME, are presented to assess mass transfer of substrate into the granules and also study the role of internal packing used in the middle part of reactor in the process stability. The value of effectiveness factor, η, for AD and DF processes were calculated to be 0.96 and 0.94, respectively, indicating that there was no mass transfer resistance due to internal and/or external factors. The results showed that the packing material could retain biomass in the reactor and had outstanding contribution in the granulation enhancement. Its role as a supplementing treatment stage was more significant at low HRTs and up-flow velocities. [ABSTRACT FROM AUTHOR]

O presente estudo teve o objetivo de avaliar a partida e a adaptação de um reator anaeróbio horizontal de leito fixo (RAHLF) no tratamento de águas residuárias do processamento primário dos frutos do cafeeiro (ARC). O reator foi construído com tubos de PVC de 0,2 m de diâmetro e 3,2 m de comprimento. O sistema foi preenchido com cubos de espuma de poliuretano para imobilização de biomassa ativa. O reator apresentou volume total de 0,1 m³ e volume útil equivalente a 0,04 m³. Em média, houve remoção de 49% da matéria orgânica, com o reator trabalhando sob carga orgânica volumétrica média de 2,66 kg m-3 d-1, medida como DQO. A suplementação de alcalinidade, somada à inoculação prévia de biomassa, proporcionou partida estável do RAHLF, confirmada pelo consumo de ácidos voláteis e adaptação da microbiota ao resíduo. O sistema apresentou resistência às variações de vazão e de carga orgânica observadas, e os teores de fenol e potássio monitorados não causaram inibição da atividade biológica no RAHLF. O maior controle sobre as variações de carga é fator importante na continuidade dos estudos.This study aimed to evaluate the start-up and the adaptation of an anaerobic horizontal-flow immobilized biomass (HAIB) reactor in order to treat wastewater from a primary processing of coffee fruits. The reactor was built with PVC tubes of 0.2 m in diameter and 3.2 m in length. The system was filled with cubes of polyurethane foam for immobilization of active biomass. The reactor presented a total capacity of 0.1 m³ and reaction volume equal to 0.04 m³. 49% of organic matter. Removal efficiency was observed, with medium organic volumetric loads equal to 2.66 kg m-3 d-1 (as chemical oxygen demand). The supplementary addition of alkalinity and the previous biomass inoculation provided a stable start-up of the reactor, as confirmed by the reduction of volatile acids and an adaptation of the present microbiology community. The systems showed resistance to changes in flow and in the organic load observed; the levels of phenol and potassium monitored did not cause inhibition of the biological activity. A better control on the changes in load rates is an important topic for the next studies.

Microbial bioremediation of petroleum wastewater by phenol-degrading-bacteria holds promise in circumventing the issue of petroleum-spill related pollution. Herein, biodegradation of petroleum wastewater samples collected from oil refinery site was carried out in a fluidized bed bioreactor by Ca-alginate immobilized biomass of phenol-degrading strains of Bacillus cereus (AKG1 MTCC9817 and AKG2 MTCC9818). Degradation performance of the system was evaluated by measuring the changes in chemical oxygen demand (COD) and level of phenolic compounds in the wastewater samples during the microbial treatment. The microbial treatment reduced initial COD level and concentration of phenolic compounds by 95 % or more, demonstrating the excellent efficacy of immobilized AKG1 and AKG2 strains in treating petroleum wastewater in continuous mode of operation. The present study demonstrates the potential of immobilized AKG1 and AKG2 in treating petroleum wastewater in fluidized bed bioreactors. [ABSTRACT FROM AUTHOR]

High rate membrane bioreactor (MBR) systems operated at extremely low sludge ages (superfast membrane bioreactors (SFMBRs)) are inefficient to achieve nitrogen removal, due to insufficient retention time for nitrifiers. Moreover, frequent chemical cleaning is required due to high biomass flux. This study aims to satisfy the nitrification in SFMBRs by using sponge as carriers, leading to the extension of the residence time of microorganisms. In order to test the limits of nitrification, bioreactor was run under 52, 5 and 2 days of carrier residence time (CRT), with a hydraulic retention time of 6 h. Different degrees of nitrification were obtained for different CRTs. Sponge immobilized SFMBR operation with short CRT resulted in partial nitrification indicating selective dominancy of ammonia oxidizers. At higher CRT, simultaneous nitrification-denitrification was achieved when accompanying with oxygen limitation. Process kinetics was determined through evaluation of the results by a modeling study. Nitrifier partition in the reactor was also identified by model calibration. [ABSTRACT FROM AUTHOR]

Depuration capacity of immobilizedPhanerochaete chrysosporiumwas tested on food effluents which showed high COD, sugar, and nitrogen concentration. Comparative study in airlift reactor and agitated flasks was performed to determine an effective depuration treatment with suspended and immobilized biomass into alginate spheres. While enzymetic production was analyzed in these sytems in order to evaluate influence of the immobilization micro-organism, effluent composition, and aeration mechanism. In addition, the use of seed lettuce allowed evaluating the quality and effectiveness of the studied effluent treatment system. In particular, all tests showed that COD and color of the effluent was reduced by airlift cultures. Treatment achieved a decline in 85% of COD in 120 h. While experiments with 33 PCU color showed high efficiency (100%) in decolourization period of 5 h. Maximum laccase production was mainly found in airlift system with suspended biomass, whereas manganese peroxidase was detected on immobilized micro-organism. Toxicity tests revealed that treated food effluent was not phytotoxic; conversely effluent contains sufficiently high concentrations of nutrients to ensure the germination and lettuce growth. [ABSTRACT FROM PUBLISHER]

The effects of initial cresol loading concentration, granular activated carbon (GAC) dosage, dry biomass density biomass immobilization matrix and chemical structure of cresol isomers on the bioregeneration efficiency of GAC loaded with o -, m - and p -cresol using polyurethane (PU) and polyvinyl alcohol (PVA) immobilized biomasses, respectively, were investigated. The results revealed higher bioregeneration efficiencies of cresol-loaded GAC when GAC was saturated with cresol. The dominating factor determining the bioregeneration efficiency was the distribution of cresol molecules within the micro-, meso- and macropores of GAC. Bioregeneration efficiency of cresol-loaded GAC could be enhanced by increasing the dry biomass density from 0.32 to 1.3 g/100 mL in PU-immobilized biomass beads. PU-immobilized biomass was found to yield higher bioregeneration efficiency than PVA-immobilized biomass. Among the cresol isomer-loaded GACs, bioregeneration efficiency of o -cresol-loaded GAC was the lowest due to more irreversibility of adsorbed o -cresol than m - and p -cresol. [ABSTRACT FROM AUTHOR]

Removal of cadmium ions was investigated using a newly developed biosorbent namely immobilized Bacillus subtilis beads in continuous flow packed bed column. In the bench scale reactor three packed bed columns with variable diameter and bed depth, were used. The effect of flow rate and initial metal ion concentration was also investigated. The experimental data was analyzed and model parameters were evaluated. Highest uptake capacity of 104.2 mg/g was obtained for cadmium ion influent concentration of 30.04 mg/L, column bed depth of 50 cm, flow rate of 5 ml/min and column internal diameter of 2.4 cm. Cyclic use of the biosorbent was also investigated and results demonstrated its suitability for industrial use. The value of the determination coefficient of Artificial Neural Network (ANN) model for prediction of breakthrough curves was found to be 0.99. It exhibited excellent capability of ANN model for predicting breakthrough curves and model coefficients. The estimated cost of treatment, using new biosorbent, was found to be $ 1.92 per cubic meter of wastewater. [ABSTRACT FROM AUTHOR]

This study focuses on the stability and tolerance of continuous-flow bioreactors inoculated with anaerobic methanogens in three different configurations: (R1) dried granular biomass immobilized in PAC-enriched hydrophilic polyurethane foam, (R2) dried granular biomass, and (R3) wet granular biomass. These systems were tested under two different organic loading rates (OLR) of 6.25 and 10.94 (g COD /(L reactor ∗d)), using a glucose-based synthetic mixture. The effect of an instantaneous shock load of phenol (5 g/L for three days), and of phenol inclusion in the feed (0.5 g/L) were also tested. At the lower OLR, all reactors performed similarly, however, increasing the OLR lead to a significant biomass washout and failure of R3. Biomass in R1 was more tolerant to phenol shock load than R2, though activity was recovered in both systems after about one month. PAC provided protection and shortened the adaptation time for 0.5 g/L phenol that continuously was fed. [ABSTRACT FROM AUTHOR]

In this study, refinery wastewater collected from Guwahati, India, was treated in an upflow packed bed reactor (PBR) with immobilizedArthrobacter chlorophenolicusA6. The wastewater was initially characterized using standard methods. The toxicity of the wastewater was determined using aerobic mixed microbial consortia following the resazurin toxicity assay. As the chemical oxygen demand (COD) level in the raw refinery wastewater was very low (190?mg?l?1), the raw wastewater was spiked with a mixture of substituted phenol at different concentrations. The batch shake flask experiment revealed that the COD removal efficiency was found to be less when the raw refinery wastewater was not spiked with nutrient. On the other hand, when supplemented with nutrients in the form of mineral salt medium, more than 98% COD removal was achieved. The PBR was operated by varying the influent phenolic concentration in the range of 250–350?mg?l?1and at a hydraulic retention time of 12.5?h. Results indicated that more than 99% pollutant removal and 94% effluent toxicity removal were achieved at a combined pollutants loading rate of 1707?mg?l?1?d?1. However, at higher pollutants loading rate, the reactor performance was found to be unstable, due to the transient accumulation of toxic intermediate products such as chlorocatechol and nitrocatechol. [ABSTRACT FROM PUBLISHER]

A feasibility study was carried out to assess the cultivation of Anammox bacteria in lab-scale closed sponge-bed trickling filter (CSTF) reactors, namely: CSTF-1 at 20 °C and CSTF-2 at 30 °C. Stable conditions were reached from day 66 in CSTF-2 and from day 104 in CSTF-1. The early stability of CSTF-2 is attributable to the influence of temperature; nevertheless, by day 405, the nitrogen removal performed by CSTF-1 increased up to similar values of CSTF-2. The maximum total nitrogen removal efficiency was 82% in CSTF-1 and 84% in CSTF-2. After more than 400 days of operation, CSTF-1 and CSTF-2 were capable to attain a total nitrogen removal efficiency of 74 ± 5% and 78 ± 4% with a total nitrogen conversion rate of 1.52 and 1.60 kg-N/m sponge 3 d, respectively. The proposed technology could be a suitable alternative for mainstream nitrogen removal in post-treatment units via the Anammox conversion pathway. [ABSTRACT FROM AUTHOR]

The feasibility of using polyvinyl alcohol (PVA) hydrogel beads encapsulating powdered activated carbon (PAC) and biomass for the enhancement ofo-cresol removal via simultaneous adsorption and biodegradation was investigated in this study. The optimum concentrations of PVA and PAC used to synthesize spherical PVA hydrogel beads with 3–4 mm diameter were found to be 7.5 and 0.5% (w/v), respectively. The results of kinetic studies showed that the rate constant ofo-cresol removal for the initialo-cresol concentration range of 100–400 mg/L could be sustained when the immobilized biomass supplemented with PAC in hydrogel beads was used. However, the removal ofo-cresol was inhibited for the initialo-cresol concentration above 150 mg/L when only immobilized biomass in the beads was used. Thus, the supplementation of PAC to the immobilized biomass in the beads could enhance the removal ofo-cresol via simultaneous adsorption and biodegradation. [ABSTRACT FROM PUBLISHER]

The potential for bisphenol A (BPA) removal by mixed consortia of immobilized microorganisms with high nitrification activity was investigated with BPA concentrations in the influent from 2.5 to 10.0 mg/L. The presence of BPA limited ammonium oxidation; nitrification efficiency decreased from 91.2 ± 1.3% in the control series to 47.4 ± 9.4% when BPA concentration in wastewater was the highest. The efficiency of BPA removal rose from 87.1 ± 5.5% to 92.9 ± 2.9% with increased BPA concentration in the influent. Measurement of oxygen uptake rates by biomass exposed to BPA showed that BPA was mainly removed by heterotrophic bacteria. A strong negative correlation between the BPA removal efficiency and nitrification efficiency indicated the limited contribution of ammonia-oxidizing bacteria (AOB) to BPA biodegradation. Exposure of biomass to BPA changed the quantity and diversity of AOB in the biomass as shown by real-time PCR and denaturing gradient gel electrophoresis. [ABSTRACT FROM AUTHOR]

Textile industry generates large quantities of dyes like azo dyes, direct dyes, reactive dyes, basic dyes, synthetic dyes which are very toxic and difficult to dispose. Many dyes are toxic, carcinogenic or prepared from known carcinogens such as benzidine or other aromatic compounds. Considering adverse effect of aniline dye and their product (present in textile effluent), decolourisation of aniline dye is essential before releasing it in environment. Immobilised fungal cells have several advantages over dispersed cells such as simple reuse of the biomass, easier liquid-solid separation and minimal clogging in continuous-flow systems. Cell immobilization lowers the apparent broth viscosity and makes the rheological features more favourable for oxygen supply and mass transfer. In present dye decolourisation process, we have used live biomass of two different fungi (Aspergillus terreus and one unknown fungus) and Actinomycete (Streptomyces). Live biomass of the two fungi and one actinomycetes gives maximum decolourisation of dye as compared to dead biomass. We have also assessed the effect of decolourised water on seed germination. [ABSTRACT FROM AUTHOR]

Biosorption of uranium ions from diluted solution (≤40 mg L) onto immobilized cells of Rhodotorula glutinis was investigated in a batch system. Equilibrium, kinetic and thermodynamic studies were conducted by considering the effect of initial uranium concentration, contact time and temperature. Non-linear forms of Langmuir, Freundlich and Sips isotherm models were used to fit the equilibrium data, Sips model was designated as the best one. Kinetic data were simulated by non-linear pseudo-first-order, pseudo-second-order and intra-particle diffusion equations. Pseudo-first-order kinetic equation described the experimental data better than pseudo-second-order equation and intra-particle diffusion equation can fit the kinetic data with two independent curves. Thermodynamic parameters, including ∆ H, ∆ G and ∆ S, were evaluated, the sorption process was determined to be spontaneous and endothermic. Uranium sorption from pure uranium solutions and uranium pit wastewater by immobilized biomass and blank beads, as well as the regeneration results indicated that immobilized R. glutinis can be use to recovery uranium from uranium pit wastewater. [ABSTRACT FROM AUTHOR]

Ethanol and biodiesel industries generate large volumes of by-products, such as vinasse and glycerol, which are suitable for biogas exploitation. This paper assessed the applicability and process performance of the anaerobic structured-bed reactor (AnSTBR) for the mesophilic (30 °C) continuous (105 days) anaerobic co-digestion of sugarcane vinasse and distilled glycerol under increasing organic loading rates (OLR) (0.5–5.0 kgCOD m−3d−1). The highest methane yield (211 NmL g−1COD rem.) and volumetric production (668 NmL L−1d−1) occurred at an OLR of 3.5 kgCOD m−3d−1. The performance of the AnSTBR showed high removal efficiencies of total COD (77.1%), carbohydrates (81.9%), and glycerol content (99.7%). Biofilm growth enhancement within the reactor offset the impairment of methanogenesis activity at high organic loads. The prompt biodegradability of glycerol reinforced the importance of gradually increase the organic load to prevent the buildup of volatile acids and maintain a stable long-term co-digestion system. [Display omitted] • Anaerobic co-digestion of sugarcane vinasse and distilled glycerol was assessed. • Biomass retention patterns in the co-digestion system were investigated. • The high biodegradability of glycerol required a gradual increase in organic load. • High organic matter removal (∼80%) was reached regardless of methanogenesis. • Enhanced biofilm growth offset impaired methanogenesis at high organic loads. [ABSTRACT FROM AUTHOR]

Highlights: [•] Use of immobilized biomass-PAC for bioregeneration of phenol- and o-cresol loaded GAC. [•] Comparison of bioregeneration using immobilized and suspended biomasses. [•] Minimization of biomass colonization on immobilized biomass bioregenerated GAC. [•] Shortening of bioregeneration duration using immobilized biomass-PAC. [Copyright &y& Elsevier]

Abstract: The present work investigates a novel water denitrification technique based on immobilized bacterial biomass using various plastic wastes as supports PVC (polyvinyl chloride), HDPE (high density polyethylene) and LDPE (low density polyethylene) in packed columns. The efficiency of these supports is compared with a conventional support, granular activated carbon (GAC). The results obtained for denitrification under various operating conditions showed that working at a high fluid velocity does not affect the bacterial behavior adversely. The denitrifying bacteria were able to treat water at an inlet nitrate concentration of 600mgL−1 with removal efficiency near to 100%. The column packed with porous GAC as a support quickly became plugged in contrast to the nonporous LDPE which possesses a rough surface for film support and delivers almost the same performance as GAC. It was found that sulfate ions promote denitrification, but chloride inhibits it. The effectiveness of the packed-bed process is not diminished significantly by the coexistence of both types of ion in the feed stream. [Copyright &y& Elsevier]

The effect of a lipase-rich enzyme preparation produced by the fungusPenicilliumsp. on solid-state fermentation was evaluated in two anaerobic bioreactors (up-flow anaerobic sludge blanket (UASB) and horizontal-flow anaerobic immobilized biomass (HAIB)) treating dairy wastewater with 1200 mg oil and grease/L. The oil and grease hydrolysis step was carried out with 0.1% (w/v) of the solid enzymatic preparation at 30°C for 24 h. This resulted in a final concentration of free acids eight times higher than the initial value. The bioreactors operated at 30°C with hydraulic retention times of 12 h (HAIB) and 20 h (UASB) for a period of 430 days, and had high chemical oxygen demand (COD) removal efficiencies (around 90%) when fed with pre-hydrolyzed wastewater. There was, however, an increase in the effluent oil and grease concentration (from values as low as 17 mg/L to values above 150 mg/L in the UASB bioreactor, and from 38–242 mg/L in the HAIB bioreactor), and oil and grease accumulation in the biomass throughout the operational period (the oil and grease content reached 1.7 times that found in the inoculum of the UASB bioreactor). The HAIB bioreactor gave better results because the support for biomass immobilization acted as a filter, retaining oil and grease at the entry of the bioreactor. The molecular analysis of the Bacteria and Archaea domains revealed significant differences in the microbial profiles in experiments conducted with and without the pre-hydrolysis step. The differences observed in the overall parameters could be related to the microbial diversity of the anaerobic sludge. [ABSTRACT FROM PUBLISHER]

Simultaneous removal of carbon, nitrogen and phosphorus was examined along with reduced generation of biological sludge during the treatment of synthetic wastewater and hog waste by the BioCAST technology. This new multi-environment wastewater treatment technology contains both suspended and immobilized microorganisms, and benefits from the presence of aerobic, microaerophilic, anoxic and anaerobic conditions for the biological treatment of wastewater. The influent concentrations during the treatment of synthetic wastewater were 1,300-4,000 mg chemical oxygen demand (COD)/L, 42-115mg total nitrogen (TN)/L, and 19-40mg total phosphorus (TP)/L. The removal efficiencies reached 98.9, 98.3 and 94.1%, respectively, for carbon, TN and TP during 225 days of operation. The removal efficiencies of carbon and nitrogen showed a minimal dependence on the nitrogen-to-phosphorus (NIP) ratio, while the phosphorus removal efficiency showed a remarkable dependence on this parameter, increasing from 45 to 94.1% upon the increase of N/P ratio from 3 to 4.5. The increase of TN loading rate had a minimal impact on COD removal rate which remained around 1.7 kg/m3 d, while it contributed to increased TP removal efficiency. The treatment of hog waste with influent COD, TN and TP concentrations of 960-2,400, 143-235 and 25-57 mg/L, respectively, produced removal efficiencies up to 89.2, 69.2 and 47.6% for the three contaminants, despite the inhibitory effects of this waste towards biological activity. The treatment system produced low biomass yields with average values of 3.7 and 8.2% during the treatment of synthetic wastewater and hog waste, respectively. [ABSTRACT FROM AUTHOR]

An integrated system, consisting of a bioreactor with a nitrifying immobilized biomass and a membrane reactor, was tested for its ability to remove two polycyclic aromatic hydrocarbons (PAHs)--phenanthrene (PHE) and 4-phenylphenanthrene (4-PPHE)--from wastewater. An almost complete removal of the selected PAHs was observed under the operational conditions applied (0.6mg PHE/l or a mixture of 0.6mg PHE/l and 0.6mg 4-PPHE/l in the influent, retention time in an aerated bioreactor of 1.5 h, transmembrane pressure of the ultrafiltration membrane 1 bar). Permeate concentration was below 2 lg PAH/l. The introduction of the PHE and an increase in organic loading (QV) from 4.9 kg chemical oxygen demand (COD)/(m³ day) to 6.7 kg COD/(m³ day) resulted in a decline in nitrification efficiency from 87.6 to 53.0%. A further increase in QV to 8.4 kg COD/(m³ day) by supplying an additional 4-PPHE induced neither ammonia oxidation nor PAH removal. The diversity of ammonia-oxidizing bacteria was not affected by operational conditions. The presence of the mixture of two PAHs induced a decline in the diversity of the total bacteria in the immobilized biomass. [ABSTRACT FROM AUTHOR]

Two-phase bioreactors consisting of bacterial consortium in suspension and sorbents with immobilized biomass were used to treat waste air containing chlorinated ethenes, trichloroethylene (TCE) and tetrachloroethylene (PCE). Synthetic municipal sewage was used as the medium for bacterial growth. The system was operated with loadings in the range 1.48–4.76gm−3 h−1 for TCE and 1.49–5.96gm−3 h−1 for PCE. The efficiency of contaminant elimination was 55–86% in the bioreactor with wood chips and 33–89% in the bioreactor filled with zeolite. The best results were observed 1 week after the pollutant loading was increased. However, in these conditions, the stability of the process was not achieved. In the next 7 days the effectiveness of the system decreased. Contaminant removal efficiency, enzymatic activity and the biomass content were all diminished. The system was working without being supplied with additional hydrocarbons as the growth-supporting substrates. It is assumed that ammonia produced during the transformation of wastewater components induced enzymes for the cometabolic degradation of TCE and PCE. However, the evaluation of nitrogen compound transformations in the system is difficult due to the sorption on carriers and the combined processes of nitrification and the aerobic denitrification. An applied method of air treatment is advantageous from both economic and environmental point of views. [Copyright &y& Elsevier]

This study reports the performance of a combined anaerobic-aerobic packed-bed reactor that can be used to treat domestic sewage. Initially, a bench-scale reactor was operated in three experimental phases. In the first phase, the anaerobic reactor was operated with an average organic matter removal efficiency of 77% for a hydraulic retention time (HRT) of 10 h. In the second phase, the reactor was operated with an anaerobic stage followed by an aerobic zone, resulting in a mean value of 91% efficiency. In the third and final phase, the anaerobic-aerobic reactor was operated with recirculation of the effluent of the reactor through the anaerobic zone. The system yielded mean total nitrogen removal percentages of 65 and 75% for recycle ratios ( r) of 0.5 and 1.5, respectively, and the chemical oxygen demand (COD) removal efficiencies were higher than 90%. When the pilot-scale reactor was operated with an HRT of 12 h and r values of 1.5 and 3.0, its performance was similar to that observed in the bench-scale unit (92% COD removal for r = 3.0). However, the nitrogen removal was lower (55% N removal for r = 3.0) due to problems with the hydrodynamics in the aerobic zone. The anaerobic-aerobic fixed-bed reactor with recirculation of the liquid phase allows for concomitant carbon and nitrogen removal without adding an exogenous source of electron donors and without requiring any additional alkalinity supplementation. [ABSTRACT FROM AUTHOR]

Our research determined the impact of operational conditions on the quantity of total and ammonia-oxidizing bacteria (AOB) in immobilized biomass. The experiment was conducted for two kinds of wastewater differing in organic carbon concentration at HRTs of 1.5 h, 1.0 h, and 0.5 h. The evaluation of bacteria number was accomplished by using the real-time PCR targeting ammonia monooxygenase (amoA) and 16S rDNA genes. In the absence of organic carbon in the influent, the shortening of HRT from 1.5 h to 0.5 h positively affected the AOB number in immobilized biomass, which reached even 30%. But their activity was limited. In the presence of organic carbon in the influent, the shortening of HRT below 1.5 h resulted in a decline of the abundance of ammonia-oxidizing bacteria and nitrification efficiency. [ABSTRACT FROM AUTHOR]

The abilities of Yarrowia lipolytica yeast to biodegradation of fatty substances in spent bleaching earth (SBE) were investigated. Yeasts inocula (of different number of propagation units) were added to SBE as free or aliginate immobilized (beads) biomass. The studied samples with SBE and yeasts were buried in soil and after winter the microbiological and chemical analyses were done as well as beads resistance and yeasts viability. The immobilized Y. lipolytica inoculum stimulated autochtonic microflora growth. The most important decrease of fatty substances in SBE was observed in presence of 50% of beads. Whereas, non depended on form and dose of yeasts was the composition of fatty acids in SBE samples, which was similar for different inocula but different from autonomous one. The effect of metabolic changes engendered by biomass suspension and immobilized cells was the decrease of contents of fatty acids of C6 - C8 and increase of C9, C16-C18. So, the inoculation of SBE with yeast could causes a specific bioconversion of fatty substances to long chain fatty acids. Noteworthy is the fact that bioremediaction was going on during winter period. [ABSTRACT FROM AUTHOR]

In sulfate-reducing reactors, it has been reported that the sulfate removal efficiency increases when the COD/SO42- ratio is increased. The start-up of a down-flow fluidized bed reactor constitutes an important step to establish a microbial community in the biofilm able to survive under the operational bioreactor conditions in order to achieve effective removal of both sulfate and organic matter. In this work the influence of COD/SO42- ratio and HRT in the development of a biofilm during reactor start-up (35 days) was studied. The reactor was inoculated with 1.6 g VSS/L of granular sludge, ground low density polyethylene was used as support material; the feed consisted of mineral medium at pH 5.5 containing 1 g COD/L (acetate:lactate, 70:30) and sodium sulfate. Four experiments were conducted at HRT of 1 or 2 days and COD/SO4 2- ratio of 0.67 or 2.5. The results obtained indicated that a COD/SO42- ratio of 2.5 and HRT 2 days allowed high sulfate and COD removal (66.1 and 69.8%, respectively), whereas maximum amount of attached biomass (1.9 g SVI/L support) and highest sulfate reducing biofilm activity (10.1 g COD-H2S/g VSS-d) was achieved at HRT of 1 day and at COD/sulfate ratios of 0.67 and 2.5, respectively, which suggests that suspended biomass also played a key role in the performance of the reactors. [ABSTRACT FROM AUTHOR]

Abstract: The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR – Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10min), reaction (460min) and discharge (10min) at 30°C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530±37mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller. [ABSTRACT FROM AUTHOR]

Abstract: Four anaerobic fluidized bed reactors filled with activated carbon (R1), expanded clay (R2), glass beads (R3) and sand (R4) were tested for anaerobic degradation of LAS. All reactors were inoculated with sludge from a UASB reactor treating swine wastewater and were fed with a synthetic substrate supplemented with approximately 20mgl−1 of LAS, on average. To 560mgl−1 COD influent, the maximum COD and LAS removal efficiencies were mean values of 97±2% and 99±2%, respectively, to all reactors demonstrating the potential applicability of this reactor configuration for treating LAS. The reactors were kept at 30°C and operated with a hydraulic retention time (HRT) of 18h. The use of glass beads and sand appear attractive because they favor the development of biofilms capable of supporting LAS degradation. Subsequent 16S rRNA gene sequencing and phylogenetic analysis of samples from reactors R3 and R4 revealed that these reactors gave rise to broad microbial diversity, with microorganisms belonging to the phyla Bacteroidetes, Firmicutes, Actinobacteria and Proteobacteria, indicating the role of microbial consortia in degrading the surfactant LAS. [Copyright &y& Elsevier]

The present study evaluated the degradation of formaldehyde in a bench-scale anaerobic sequencing batch reactor, which contained biomass immobilized in polyurethane foam matrices. The reactor was operated for 212 days at 35°C with 8h sequential cycles, under different affluent formaldehyde concentrations ranging from 31.6 to 1104.4mg/L (formaldehyde loading rates from 0.08 to 2.78kg/m3 day). The results indicate excellent reactor stability and over 99% efficiency in formaldehyde removal, with average effluent formaldehyde concentration of 3.6±1.7mg/L. Formaldehyde degradation rates increased from 204.9 to 698.3mg/Lh as the initial concentration of formaldehyde was increased from around 100 to around 1100mg/L. However, accumulation of organic matter was observed in the effluent (chemical oxygen demand (COD) values above 500mg/L) due to the presence of non-degraded organic acids, especially acetic and propionic acids. This observation poses an important question regarding the anaerobic route of formaldehyde degradation, which might differ substantially from that reported in the literature. The anaerobic degradation pathway can be associated with the formation of long-chain oligomers from formaldehyde. Such long- or short-chain polymers are probably the precursors of organic acid formation by means of acidogenic anaerobic microorganisms. [Copyright &y& Elsevier]

Abstract: The objective of this study was to determine the best performance of an anaerobic sequencing batch biofilm reactor (AnSBBR) based on the use of four different bed materials as support for biomass immobilization. The bed materials utilized were polyurethane foam (PU), vegetal carbon (VC), synthetic pumice (SP), and recycled low-density polyethylene (PE). The AnSBBR, with a total volume of 7.2L, was operated in 8-h batch cycles over 10 months, and fed with domestic sewage with an average influent chemical oxygen demand (COD) of 358±110mg/L. The average effluent COD values were 121±31, 208±54, 233±52, and 227±51mg/L, for PU, VC, SP, and PE, respectively. A modified first-order kinetic model was adjusted to temporal profiles of COD during a batch cycle, and the apparent kinetic constants were 0.52±0.05, 0.37±0.05, 0.80±0.04, and 0.30±0.02h−1 for PU, VC, SP, and PE, respectively. Specific substrate utilization rates of 1.08, 0.11, and 0.86mg COD/mgVS day were obtained for PU, VC, and PE, respectively. Although SP yielded the highest kinetic coefficient, PU was considered the best support, since SP presented loss of chemical constituents during the reactor''s operational phase. In addition, findings on the microbial community were associated with the reactor''s performance data. Although PE did not show a satisfactory performance, an interesting microbial diversity was found on its surface. Based on the morphology and denaturing gradient gel electrophoresis (DGGE) results, PE showed the best capacity for promoting the attachment of methanogenic organisms, and is therefore a material that merits further analysis. PU was considered the most suitable material showing the best performance in terms of efficiency of solids and COD removal. [Copyright &y& Elsevier]

Abstract: This study investigates the feasibility of an anaerobic bioreactor for treating low contents of organic matter to generate organic acids and hydrogen. The device employed for this purpose was a horizontal packed-bed bioreactor fed with glucose-based synthetic wastewater and operated with hydraulic retention times from 0.5 to 2h. A microbial biofilm was developed without previous inoculation, using expanded clay beads (4.8–6.3mm) as support material. Alkalinity was found to be the main parameter affecting the production of hydrogen and organic acids, and the system produced optimal output when operating without a buffer agent. The average hydrogen production was 2.48, 2.15 and of glucose for NaHCO3 influent concentrations of 0, 1000 and , respectively. The operational regime of the bioreactor, the support material and the controlled alkalinity were effective in selecting and immobilizing microbial fermenting biofilms, which successfully produced hydrogen and organic acids throughout the operating period. Exploratory assays indicated the feasibility of organic acid extraction using an anionic polymeric resin. [Copyright &y& Elsevier]

This paper presents and discusses data obtained from 125 days of operation of an anaerobic sequencing batch biofilm reactor (ASBBR) containing biomass immobilized in inert support (polyurethane foam cubes) applied for the treatment of domestic sewage. The reactor, with a total volume of 1.2m3, was operated in 8-hour cycles treating 0.65m3 per batch. Each batch cycle comprised feeding (2h), reaction (5h), discharge (0.5h) and idle (0.5h). The reactor took approximately 20 days to reach operational stability, confirming that anaerobic fixed film reactors require a shorter start-up period than anaerobic suspended growth reactors. Under stable operating conditions after the startup period, the mean values of COD removal efficiency and effluent total COD achieved 66% and 133 (±39) mgl−1, respectively, demonstrating the potential applicability of this reactor configuration for treating domestic sewage. Even so, a post-treatment unit is required as occurs generally when anaerobic reactors are applied for domestic sewage treatment. [Copyright &y& Elsevier]

Abstract: This work reports on experiments for an anaerobic sequencing batch reactor containing immobilized biomass which aimed at verifying the effects of solid-phase mass transfer on the reactor’s overall performance. Four experiments were carried out at 30°C with cubic polyurethane foam particles previously inoculated with anaerobic biomass. Different solid-phase mass transfer conditions were reached in each experiment by varying the size of the bioparticle from 0.5 to 3.0cm. The reactor was fed with a low-strength synthetic wastewater containing protein, carbohydrates and lipid and the effects of mass transfer were evaluated through dynamic substrate concentration profiles during 8-hour batch cycles. A modified first-order kinetic model provided a good representation of the behavior of the dynamic concentration profiles. The solid-phase mass transfer was found to slightly affect the concentration of effluent organic matter expressed as chemical oxygen demand (COD). The concentration of residual effluent substrate increased as the size of the bioparticle was increased. The cycle time was not affected as the size of the bioparticle was increased from 0.5 to 2.0cm. However, it was found that the cycle time in a reactor with 3.0-cm cubic particles should be higher than that required in systems with smaller particles. The apparent first-order kinetic parameter was estimated as 0.59±0.01h−1 for experiments with bioparticle sizes ranging from 0.5 to 2.0cm, while a value of 0.48h−1 was obtained in the experiment with 3.0-cm bioparticles. [Copyright &y& Elsevier]

The ever-increasing diversity of industrial activity is responsible for the discharge of compounds that are toxic or difficult to degrade into the environment. Some of the compounds found in surface and ground waters, usually deriving from the contamination of oil-based products, are benzene, toluene, ethylbenzene and xylenes (BTEX). To remove these compounds from contaminated water, a bench-scale horizontal-flow anaerobic immobilized biomass reactor, containing anaerobic biomass from various sources immobilized in polyurethane foam matrices, was employed to treat a synthetic substrate composed of protein, carbohydrates and BTEX solution in ethanol, as well as a BTEX solution in ethanol as the sole carbon source. The reactor removed up to 15. 0 mg/l of each BTEX compound over a hydraulic detention time of 11. 4 h. A first-order kinetic model fitted the experimental data well, showing correlation coefficients higher than 0. 994. The apparent first-order coefficient values, k1app, ranged from 8. 4±1. 5 day-1 for benzene to 10. 7±1. 4 day-1 for o-xylene in the presence of ethanol, protein and carbohydrates, and from 10. 0±2. 0 day-1 for benzene to 13. 0±1. 7 day-1 for o-xylene in the presence of ethanol. The BTEX degradation rates estimated here were 10-to 94-fold higher than those found in reports on microcosm studies. [ABSTRACT FROM AUTHOR]

Activated sludge was immobilised in a porous ceramic carrier to create a stationary core of a bio-reactor. Municipal wastewater was treated in this reactor under varied conditions of volumetric organic loading rate (expressed by chemical oxygen demand (COD)) that were the following: 6.5, 8.0, 20.8, 48.8 g COD l&minus1 d-1. The rate constants of ammonification, nitrification and denitrification under aerobic conditions were determined. All rate constants increased with a growth in volumetric loading rate, but the highest loading value of 48.8 g COD l&minus1 d-1 limited the ammonification and nitrification rates. [ABSTRACT FROM AUTHOR]

Abstract: Data on the performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor subjected to step increases of organic loading rates (OLR) and to organic shock loads (OSL) are presented and discussed. The tubular reactor (100cm long and 5cm diameter) with a useful volume of 1995mL was filled with polyurethane foam cubic matrices holding immobilized biomass and fed with synthetic wastewater. The reactor was operated at the controlled temperature of 30±1°C and hydraulic retention time of 7h. After about 15 days, the HAIB reactor attained operating stability. Thereafter, it was subjected to step increases of the applied OLR that ranged from 6.8 to 18.8kgCOD/m3 d. After steady state had been achieved at each step, OSL corresponding to approximately three times the operating OLR were applied for 7h. No disturbance was observed due to the step increase in OLR. An increase in effluent chemical oxygen demand (COD) and volatile fatty acids (VFA) concentrations and a decrease in the percentage of methane in the biogas were observed due to OSL applications. However, stability of the monitoring parameters was always restored approximately 17h after the application of OSL for all conditions tested. [Copyright &y& Elsevier]

Abstract: The main objectives of this study were to evaluate the performance of an anaerobic sequencing batch reactor when subjected to a progressive increase of influent glucose concentration and to estimate the kinetic parameters of glucose degradation. The reactor was initially operated in 8-h cycles, treating glucose in concentrations of 500, 1000 and 2000mgl−1. No glucose was detected in the effluent under these three conditions. The reactor showed operating stability when treating a glucose concentration of approximately 500mgl−1, with filtered chemical oxygen demand (COD) removal efficiencies varying from 93% to 97%. Operational instability occurred in the operation with glucose concentrations of approximately 1000 and 2000mgl−1, caused mainly by a production of extracellular polymeric substances (EPS), which led to hydrodynamic and mass transfer problems in the reactor. The mean volatile acid concentration values in the effluent were approximately 159±72 and 374±92mgl−1, respectively. A first-order model was adjusted to glucose concentration profiles and a modified model, including a residual concentration of substrate, was adjusted to COD temporal profiles. To check the formation of EPS, the reactor was operated in 3-h cycles with concentrations of 500 and 1000mgl−1. The purpose of this step was to discover if the production of EPS resulted from the biomass''s exposure to a low concentration of substrate over a long period of time. Thus, it was hypothesized that a reduction of the time cycle would also reduce the exposure to low concentrations. However, this hypothesis could not be confirmed because large amounts of EPS were formed already under the first operational condition, using approximately 500mgl−1 of glucose in the influent, thus indicating the fallacy of the hypothesis. The production of EPS proved to depend on the organic volumetric load applied to the reactor. [Copyright &y& Elsevier]

Abstract: This work focuses on the influence of the source of organic matter on the process of biomass adhesion on polyurethane foam matrices in fixed-bed anaerobic immobilized-sludge reactors. Five experiments were performed in differential ‘gradientless’ reactors fed with meat extract (protein), glucose, starch, lipids and complex substrate. The polyurethane foam colonization process was monitored temporally in each experiment to identify the amount of biomass buildup, extracellular polymer production and the morphological characteristics of the cells adhering to the support. Different immobilization patterns were observed for the different substrates used. The morphological variety was found to be dependent on the substrate constituents. Polymer excretion was apparently crucial in the colonization process of the polyurethane matrices and was likely related to cell fixation on the support. The production of extracellular polymeric substances speeded up the initial fixation of microorganisms on the polyurethane surface. [Copyright &y& Elsevier]