Immobilized Biomass Reactor Research Articles

A new mathematical model to evaluate simazine removal in three different immobilized-biomass reactors

A new mathematical model based on the cinetical Langmuir equation is developed to interpret and predict the effectiveness of simazine (SZ) removal in immobilized-biomass reactor (IBR), to consider herbicide-support affinity (Cx), and herbicide-cell affinity (Cy). Three solid supports: sepiolite monolith, granular sepiolite, and alginate were used in pilot-scale reactors that were inoculated with Klebsiella planticola DSZ. The abiotic process was analysed by measuring the SZ sorption capacity of the reactor supports. Sepiolite monolith showed the maximum value for herbicide-support affinity (28.02±0.9%). The effectiveness of the biotic process was estimated considering the formation of biomass and SZ biodegradation. Granular sepiolite showed either higher affinity with SZ and viability rate (0.90) throughout the process, and SZ removal rate was 3.39±0.06 mg/h. The mathematical model presented in this paper provides useful insights into the interpretation of experimental data as well as prediction for the implementation of biological reactors.

Detoxification of wastewater containing five common pesticides by solar AOPs–biological coupled system

A mixture of five pesticides commonly used in intensive agriculture in the southeast of Spain, Methomyl, Dimethoate, Oxamyl, Cymoxanil and Pyrimethanil, has been completely mineralized in a combined solar photocatalytic–biological pilot plant. Two advanced oxidation processes (AOPs: TiO 2 and photo-Fenton) were employed for enhancing the biodegradability of wastewater and an aerobic immobilised biomass reactor (IBR) was used for the following continuous biological treatment. TiO 2 photocatalysis experiments were performed in a 35-L solar pilot plant made up of three compound parabolic collectors (CPCs), whereas photo-Fenton tests were carried out in a 75-L solar pilot plant with four CPCs units. The initial pesticide concentrations in the mixture were 50 mg L −1 each. The TiO 2 catalyst concentration employed was 200 mg L −1, and two different Fe 2+ concentrations, 20 mg L −1 and 55 mg L −1, were used in the photo-Fenton tests. Toxicity ( Vibrio fischeri) and biodegradability assays (Zahn-Wellens test) were also performed to monitor toxicity and biodegradability of samples at different stages of photo-Fenton treatment. Biodegradable compounds generated during the preliminary oxidative process were mineralized in a 60-L activated sludge biological reactor filled with 30 L of propylene Pall Ring supports. Total disappearance of the parent compounds, more than 90% mineralization and complete nitrification were achieved by the combined system.

Evaluation of the microbial diversity in a horizontal-flow anaerobic immobilized biomass reactor treating linear alkylbenzene sulfonate

The purpose of this work was to assess the degradation of linear alkylbenzene sulfonate (LAS) in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The reactor was filled with polyurethane foam where the sludge from a sanitary sewage treatment was immobilized. The hydraulic detention time (HDT) used in the experiments was of 12 h. The reactor was fed with synthetic substrate (410 mg l(-1) of meat extract, 115 mg l(-1) of starch, 80 mg l(-1) of saccharose, 320 mg l(-1) of sodium bicarbonate and 5 ml l(-1) of salt solution) in the following stages of operation: SI-synthetic substrate, SII-synthetic substrate with 7 mg l(-1) of LAS, SIII-synthetic substrate with 14 mg l(-1) of LAS and SIV-synthetic substrate containing yeast extract (substituting meat extract) and 14 mg l(-1) of LAS, without starch. At the end of the experiment (313 days) a degradation of approximately 35% of LAS was achieved. The higher the concentration of LAS, the greater the amount of foam for its adsorption. This is necessary because the isotherm of LAS adsorption in the foam is linear for the studied concentrations (2 to 50 mg l(-1)). Microscopic analyses of the biofilm revealed diverse microbial morphologies, while Denaturing Gradient Gel Eletrophoresis (DGGE) profiling showed variations in the population of total bacteria and sulphate-reducing bacteria (SRB). The 16S rRNA gene sequencing and phylogenetic analyses revealed that the members of the order Clostridiales were the major components of the bacterial community in the last reactor operation step.

Advanced oxidation process–biological system for wastewater containing a recalcitrant pollutant

Two advanced oxidation processes (AOPs), ozonation and photo-Fenton, combined with a pilot aerobic biological reactor at field scale were employed for the treatment of industrial non-biodegradable saline wastewater (TOC around 200 mgL(-1)) containing a biorecalcitrant compound, alpha-methylphenylglycine (MPG), at a concentration of 500 mgL(-1). Ozonation experiments were performed in a 50-L reactor with constant inlet ozone of 21.9 g m(-3). Solar photo-Fenton tests were carried out in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed in this system was 20 mgL(-1) of Fe2+ and the H2O2 concentration was kept in the range of 200-500mgL(-1). Complete degradation of MPG was attained after 1,020 min of ozone treatment, while only 195 min were required for photo-Fenton. Samples from different stages of both AOPs were taken for Zahn-Wellens biocompatibility tests. Biodegradability enhancement of the industrial saline wastewater was confirmed (>70% biodegradability). Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralised in a 170-L aerobic immobilised biomass reactor (IBR). The global efficiency of both AOP/biological combined systems was 90% removal of an initial TOC of over 500 mgL(-1).

Remoção de etanol e benzeno em reator anaeróbio horizontal de leito fixo na presença de sulfato

Reator anaeróbio horizontal de leito fixo (RAHLF), preenchido com espumas de poliuretano, foi usado para tratar benzeno em solução etanólica, sob condições sulfetogênicas. Benzeno foi adicionado em concentração inicial de 2,0 mg.l-1, seguido de aumentos que variaram até 10 mg.l-1. O etanol foi adicionado em concentrações de 170 mg.l-1 a 980 mg.l-1. Soluções de sulfato ferroso e sulfato de sódio foram usadas, nas concentrações de 91 e 550 mg.l-1, respectivamente. O reator foi operado a 30 (± 2) ºC com tempo de detenção hidráulica de 12 h. A remoção da matéria orgânica foi próxima a 90% com taxa máxima de degradação de benzeno de 0,07 mg benzeno.mg-1SSV.d-1. O presente trabalho corrobora os dados obtidos por Cattony et al (2005), na medida em que torna mais consistente a proposta do uso de unidades compactas de RAHLF, para a biorremediação in situ de compostos aromáticos.

Coupling solar photo-Fenton and biotreatment at industrial scale: Main results of a demonstration plant

This paper reports on the combined solar photo-Fenton/biological treatment of an industrial effluent (initial total organic carbon, TOC, around 500 mg L −1) containing a non-biodegradable organic substance (α-methylphenylglycine at 500 mg L −1), focusing on pilot plant tests performed for design of an industrial plant, the design itself and the plant layout. Pilot plant tests have demonstrated that biodegradability enhancement is closely related to disappearance of the parent compound, for which a certain illumination time and hydrogen peroxide consumption are required, working at pH 2.8 and adding Fe 2+ = 20 mg L −1. Based on pilot plant results, an industrial plant with 100 m 2 of CPC collectors for a 250 L/h treatment capacity has been designed. The solar system discharges the wastewater (WW) pre-treated by photo-Fenton into a biotreatment based on an immobilized biomass reactor. First, results of the industrial plant are also presented, demonstrating that it is able to treat up to 500 L h −1 at an average solar ultraviolet radiation of 22.9 W m −2, under the same conditions (pH, hydrogen peroxide consumption) tested in the pilot plant.

Kinetics of organic removal in fixed-bed aerobic biological reactor

The process kinetics of a lab-scale upflow aerobic immobilized biomass (UAIB) reactor using simulated sugar-manufacturing wastewater as feed was investigated. The experimental unit consisted of a 22 l reactor filled with high porosity pumice stone. The UAIB reactor was tested under different organic loads and different hydraulic retention times (HRT) and the substrate loading removal rate was compared with prediction of Stover–Kincannon model, second-order model and the first order substrate removal model. After obtaining steady-state conditions, organic loading rate was increased from 750 to 4500 g COD/m 3 day to resemble wastewater from sugar production lines, and hydraulic retention time was decreased from 1 to 0.5 days, stepwise. Nine different operational conditions were applied changing these two parameters in a certain program. As a result of the calculations, Stover–Kincannon model and second-order model known as “Grau” model were found to be the most appropriate models for this reactor. Stover–Kincannon model and Grau second-order model gave high correlation coefficients, which were 99.7% and 99.4%, respectively. Therefore, these models could be used in predicting the behavior or design of the UAIB reactors.

Removal of Nitrogen and Organic Matter in a Radial-Flow Aerobic-Anoxic Immobilized Biomass Reactor Used in the Posttreatment of Anaerobically Treated Effluent

This work reports on the removal of organic matter and nitrogen in a radial-flow aerobic-anoxic immobilized biomass (RAIB) reactor fed with domestic sewage pretreated in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Polyurethane foam was used as support material for biomass attachment in both reactors. In batch experiments, a first-order kinetic model with residual concentration represented the organic matter removal rate, whereas nitrogen conversion followed a pseudo-first-order reaction in series model, with kinetic constants k1 (ammonium to nitrite) and k2 (nitrite to nitrate) of 0.25 and 6.62 h(-1), respectively. The RAIB reactor was operated in continuous-flow mode and changes in the airflow rate and hydraulic retention time were found to interfere in the apparent kinetic constants to the nitritation (k1) and nitratation (k2). Nitrification and denitrification were achieved in the partially aerated RAIB reactor operating with hydraulic retention times of 3.3 h and 2.7 h in the aerobic and anoxic zones, respectively. Ethanol was added in the anoxic zone of the reactor to promote denitrification. The effluent flow of the RAIB reactor presented a COD of 52 mg l(-1), and concentrations of 2 mg N - NH4(+)1(-1), 1.24 mg N - N02(-)1(-1) and 3.46 mg N - N03(-)1(-1).

A combined solar photocatalytic-biological field system for the mineralization of an industrial pollutant at pilot scale

A coupled solar photocatalytic-biological pilot plant system has been employed to enhance the biodegradability and complete mineralization of a biorecalcitrant industrial compound, α-methylphenylglycine, dissolved in distilled water and simulated seawater at 500 mg L −1. The pollutant was completely degraded by a solar photo-Fenton treatment in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed was 2 and 20 mg L −1 of Fe 2+ and the H 2O 2 concentration was kept in the range of 200–500 mg L −1. A Zahn–Wellens (Z–W) test applied to photo-treated samples demonstrated that intermediates produced within a short time of starting the photo-Fenton process were biodegradable. Consequently, the photocatalytic and biological processes were combined. Biodegradable compounds generated during the preliminary oxidative process were biologically mineralized in a 170-L aerobic immobilised biomass reactor (IBR), filled with 90–95 L propylene Pall ® Ring supports colonized by activated sludge. Almost total mineralization (90% overall total organic carbon removed) was attained in the combined treatment system (for both distilled and seawater experiments). Moreover, nitrification and denitrification phenomena were also observed.

Anaerobic biodegradation of pentachlorophenol in a fixed-film reactor inoculated with polluted sediment from Santos–São Vicente Estuary, Brazil

This paper discusses the results of pentachlorophenol (PCP) anaerobic biodegradation in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor operated under methanogenic and halophylic conditions. The system was inoculated with autochthonous microorganisms taken from a site in the Santos-São Vicente Estuary (state of São Paulo, Brazil) severely contaminated with PCP, phenolic compounds, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and heavy metals. The inoculum was previously enriched for methanogenesis activity by changing glucose concentrations and under halophylic condition. PCP was added to the HAIB reactor as sodium salt (NaPCP) at an initial concentration of 5 mg l(-1) and increased to 13, 15, and 21 mg l(-1). Organic matter removal efficiency ranged from 77 to 100%. PCP removal efficiency was 100%. Denaturing gradient gel electrophoresis profile showed changes in the structure of Bacteria domain, which was associated with NaPCP and glucose amendments. The diversity of Archaea remained unaltered during the different phases. Scanning electron microscope examinations showed that cells morphologically resembling Methanosarcina and Methanosaeta predominated in the biofilm. These cells were detected by fluorescence in situ hybridization with the Methanosarcinales (MSMX860) specific probe. The results are of great importance in planning the estuary's restoration by using anaerobic technology and autochthonous microorganisms for bioremediation.

Biofilm adaptation to sulfate reduction in anaerobic immobilized biomass reactors sujected to different COD/sulfate ratios

Various aspects of biofilm adaptation to sulfate reduction in horizontal-flow anaerobic immobilized biomass (HAIB) reactors subjected to increasing sulfate concentrations and different COD/sulfate ratios are presented and discussed. Four bench-scale HAIB reactors filled with vegetal carbon (R1 and R2) and polyurethane foam matrices (R3 and R4) were utilized. Influent sulfate concentrations ranging from 500 to 3000 mg/L were applied at COD/sulfate ratios ranging from 5.0 to 1.7. Reactors R1 and R4 were operated with higher sulfate loads than those applied to R2 and R3. For the same COD/sulfate ratio, the highest sulfate reduction efficiency (approximately 80%) was displayed by the vegetal carbon reactor (R2) subjected to low sulfate loads. According to the results of our molecular biology analyses, the different support materials provided different biomass colonization conditions. The lowest diversity of sulfate-reducing bacteria was found in the HAIB filled with polyurethane foam matrices operating with high sulfate loads.

Influence of the addition of sulphate and ferric ions in a methanogenic anaerobic packed-bed reactor treating gasoline-contaminated water

Benzene, toluene and xylene (BTX) are relatively soluble aromatic compounds of gasoline. Gasoline storage tank leakages generally lead to an extensive contamination of groundwater. In the natural environment for instance, these compounds might be biodegraded under a variety of reducing potentials. The objective of this work was to examine the influence of the addition of sulphate and Fe(OH)3 in a methanogenic horizontal-flow anaerobic immobilized-biomass reactor treating gasoline-contaminated water. Three different conditions were evaluated: methanogenic, sulphidogenic and sulphidogenic with the addition of ferric ions. Methanogenic condition showed the higher BTX degradation rates and the addition of sulphate negatively affected BTX removal rates with the production of H2S. However, the addition of ferric ions resulted in the precipitation of sulphur, improving BTX degradation by the consortium. Metanosphaera sp., Methanosarcina barkeri and Methanosaeta concilii were identified in the consortium by means of 16S and directly related to the addition of ferric ions.

Performance of a reactor containing denitrifying immobilized biomass in removing ethanol and aromatic hydrocarbons (BTEX) in a short operating period

A horizontal-flow anaerobic immobilized biomass reactor (HAIB) containing denitrifying biomass was evaluated with respect to its ability to remove, separately and in a short operating period (30 days), organic matter, nitrate, and the hydrocarbons benzene (41.4 mg L −1), toluene (27.8 mg L −1), ethylbenzene (31.1 mg L −1), o-xylene (28.5 mg L −1), m-xylene (28.4 mg L −1) and p-xylene (32.1 mg L −1). The purified culture, which was grown in the presence of the specific hydrocarbon, was used as the source of cells to be immobilized in the polyurethane foam. After 30 days of operation, the foam was removed and a new immobilized biomass was grown in the presence of another hydrocarbon. The average hydrocarbon removal efficiency attained was 97%. The organic matter, especially ethanol, was removed with an average efficiency of 83% at a mean influent concentration of 1185.0 mg L −1. A concomitant removal of 97% of nitrate was observed for a mean influent concentration of 423.4 mg L −1. The independent removal of each hydrocarbon demonstrated that these contaminants can be biodegraded separately, without the need for a compound to be the primary substrate for the degradation of another. This study proposes the application of the system for treatment of areas contaminated with these compounds, with substitution and formation of a biofilm in a 30-day period.

BTEX and ethanol removal in horizontal-flow anaerobic immobilized biomass reactor, under denitrifying condition

A denitrifying consortium was used as inoculum to form a biofilm in horizontal-flow anaerobic immobilized biomass reactor. The reactor was fed with hydrocarbons, separately (benzene at 13.8, 15.4 and 26.5 mg/L; toluene 30.8 mg/L; ethylbenzene 33.3 mg/L; xylene 32.1 mg/L), and also with a benzene, toluene, ethylbenzene and xylene (BTEX) mix solution of approximately 5.0 mg/L of each hydrocarbon. The hydrocarbons were dissolved in a solution containing ethanol. Organic matter removal efficiencies were of 95% with benzene and toluene amendments and about 76% with ethylbenzene, m-xylene and the BTEX-mix amendments. Hydrocarbons removal efficiencies were of 99% at an initial concentration of benzene 26.5 mg/L, toluene 30.8 mg/L, m-xylene 32.1 mg/L, ethylbenzene 33.3 mg/L and BTEX 26.5 mg/L. Microbial diversity assessed by a small portion of 16S DNA suggested the predominance of species related to the phylotypes Pseudomonas, Paracoccus and Bacteroides. This system showed to be an alternative to treating wastewater contaminated with nitrate, ethanol and hydrocarbons.

Kinetics of BTEX degradation in a packed-bed anaerobic reactor

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, k1(app), 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.

Development and evaluation of a radial anaerobic/aerobic reactor treating organic matter and nitrogen in sewage

The design and performance of a radial anaerobic/aerobic immobilized biomass (RAAIB) reactor operating to remove organic matter, solids and nitrogen from sewage are discussed. The bench-scale RAAIB was divided into five concentric chambers. The second and fourth chambers were packed with polyurethane foam matrices. The performance of the reactor in removing organic matter and producing nitrified effluent was good, and its configuration favored the transfer of oxygen to the liquid mass due to its characteristics and the fixed polyurethane foam bed arrangement in concentric chambers. Partial denitrification of the liquid also took place in the RAAIB. The reactor achieved an organic matter removal efficiency of 84%, expressed as chemical oxygen demand (COD), and a total Kjeldahl nitrogen (TKN) removal efficiency of 96%. Average COD, nitrite and nitrate values for the final effluent were 54 mg.L-1, 0.3 mg.L-1 and 22.1 mg.L-1, respectively.

Morphological study of biomass during the start-up period of a fixed-bed anaerobic reactor treating domestic sewage

This work focused on a morphological study of the microorganisms attached to polyurethane foam matrices in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor treating domestic sewage. The experiments consisted of monitoring the biomass colonization process of foam matrices in terms of the amount of retained biomass and the morphological characteristics of the cells attached to the support during the start-up period. Non-fluorescent rods and cocci were found to predominate in the process of attachment to the polyurethane foam surface. From the 10th week of operation onwards, an increase was observed in the morphological diversity, mainly due to rods, cocci, and Methanosaeta-like archaeal cells. Hydrodynamic problems, such as bed clogging and channeling occurred in the fixed-bed reactor, mainly due to the production of extracellular polymeric substances and their accumulation in the interstices of the bed causing a gradual deterioration of its performance, which eventually led to the system's collapse. These results demonstrated the importance and usefulness of monitoring the dynamics of the formation of biofilm during the start-up period of HAIB reactors, since it allowed the identification of operational problems.

Performance and stability of an anaerobic fixed bed reactor subjected to progressive increasing concentrations of influent organic matter and organic shock loads

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 (100 cm long and 5 cm diameter) with a useful volume of 1995 mL 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 7 h. 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 18.8 kg COD/m 3 d. After steady state had been achieved at each step, OSL corresponding to approximately three times the operating OLR were applied for 7 h. 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 17 h after the application of OSL for all conditions tested.

Ethanol and toluene removal in a horizontal‐flow anaerobic immobilized biomass reactor in the presence of sulfate

In this study it is reported the operation of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and toluene. The system was inoculated with sludge taken from up-flow anaerobic sludge blanket (UASB) reactors treating refuses from a poultry slaughterhouse. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg/L, respectively), to promote a sulfate-reducing environment. Toluene was added at an initial concentration of 2.0 mg/L followed by an increased range of different amendments (5, 7, and 9 mg/L). Ethanol was added at an initial concentration of 170 mg/L followed by an increased range of 960 mg/L. The reactor was operated at 30(+/-2) degrees C with hydraulic detention time of 12 h. Organic matter removal efficiency was close to 90% with a maximum toluene degradation rate of 0.06 mg(toluene)/mg(vss)/d. Sulfate reduction was close to 99.9% for all-nutritional amendments. Biofilm microscopic characterization revealed a diversity of microbial morphologies and DGGE-profiling showed a variation of bacterial and sulfate reducing bacteria (SRB) populations, which were significantly associated with toluene amendments. Diversity of archaea remained unaltered during the different phases of this experiment. Thus, this study demonstrates that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatics bioremediation.

Anaerobic packed-bed reactor for bioremediation of gasoline-contaminated aquifers

Two bench-scale horizontal-flow anaerobic immobilized biomass (HAIB) reactors were assayed with the purpose of evaluating their performance in removing gasoline from contaminated groundwater. The first reactor was fed initially with synthetic substrate containing protein, carbohydrates and benzene, toluene, ethylbenzene, and xylene (BTEX) solubilized in ethanol. The BTEX concentration of each compound ranged from 3.0 to 15.0 mg/l. The BTEX solution in ethanol was then used as the sole carbon source. The hydraulic retention time (HRT) was 11.4 h and the temperature was kept constant at 30±1 ° C . Chemical oxygen demand (COD) removal efficiencies of about 96% and BTEX removal efficiencies varying from 75 to 99% were achieved during this experimental period. The second reactor was operated to simulate actual field conditions. Thus, the HAIB reactor was fed with a mixture of water and commercial gasoline devoid of ethylbenzene. The concentration of each compound considered in BTX composition (benzene, toluene, and m-xylene) was gradually raised to 15.0 mg/l. The HRT was 20.0 h and the temperature was kept at 25±1 ° C . The HRT was progressively lowered to 8.0 h to investigate the reactor loading rate capacity. The best COD and BTX removal efficiencies achieved were about 99% and 95%, respectively, with a HRT exceeding 12 h. The results indicate the viability of using the HAIB reactor to treat wastewater and groundwater contaminated with BTEX and gasoline.