Study of microbial community structures in UASB sludge treating municipal wastewater by denaturing gradient gel electrophoresis of 16S rDNA

The structures of microbial communities in lab-scale upflow anaerobic sludge blanket (UASB) reactors for treating municipal wastewater with different ratios of COD_soluble/ COD_total were studied using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. The microbial structure of the inoculum sludge obtained from a full-scale UASB reactor of treating potato processing wastewater was compared with the structures of sludges collected from three lab-scale UASB reactors after eight months feeding with raw municipal wastewater, with CEPS (chemically enhanced primary sedimentation) pretreated municipal wastewater, and with a synthetic municipal sewage, respectively. Computer-aided numerical analysis of the DGGE fingerprints showed that the bacterial community underwent major changes. The sludges for treating raw and CEPS pretreated wastewater had very similar bacterial and archaeal communities (82% and 96% similarity) but were different from that for treating the synthetic sewage. Hence, despite similar % COD in the particulate form in the synthetic and the real wastewater, the two wastewaters were selected for different microbial communities. Prominent DGGE bands of Bacteria and Archaea were purified and sequenced. The 16S rRNA gene sequences of the dominant archaeal bands found in the inoculum, and UASB sludge fed with raw sewage, CEPS pretreated wastewater, and synthetic sewage were closely associated withMethanosaeta concilii. In the UASB sludge fed with synthetic sewage, another dominant band associated with an uncultured archaeon 39-2 was found together withM. concilii.     

Thermophilic anaerobic treatment of sulphur rich forest industry wastewater

Thermophilic anaerobic treatment of sulphur-rich paper mill wastewater (0.8-3.1 gCOD/l, 340–850 mgSO₄/l; COD:SO₄ 3.4-5.3) was studied in three laboratory-scale, upflow anaerobic sludge blanket (UASB) reactors and in bioassays. The reactors were inoculated with non-adapted thermophilic granular sludge. In the bioassays, no inhibition of the inoculum was detected and about 62% COD removal (sulphide stripped) was obtained. About 70 to 80% of the removed COD was methanised. In the reactors, up to 60–74% COD removal (effluent sulphide stripped) was obtained at loading rates up to 10–30 kgCOD/m³d and hydraulic retention times down to 6 to 2 hours. The effluent total sulphide was up to 150–250 mg/l. Sulphide inhibition could not be confirmed from the reactor performances. The results from bioassays suggested that both the inoculum and sludge from the UASB reactor used acetate mainly for methane production, while sulphide was produced from hydrogen or its precursors.     

Study of microbial community structures in UASB sludge treating municipal wastewater by denaturing gradient gel electrophoresis of 16S rDNA

The structures of microbial communities in lab-scale upflow anaerobic sludge blanket (UASB) reactors for treating municipal wastewater with different ratios of COD soluble/COD total were studied using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes.The microbial structure of the inoculum sludge obtained from a full-scale UASB reactor of treating potato processing wastewater was compared with the structures of sludges collected from three lab-scale UASB reactors after eight months feeding with raw municipal wastewater, with CEPS (chemically enhanced primary sedimentation) pretreated municipal wastewater, and with a synthetic municipal sewage, respectively. Computer-aided numerical analysis of the DGGE fingerprints showed that the bacterial community underwent major changes. The sludges for treating raw and CEPS pretreated wastewater had very similar bacterial and archaeal communities (82%and 96% similarity) but were different from that for treating the synthetic sewage. Hence, despite similar % COD in the particulate form in the synthetic and the real wastewater, the two wastewaters were selected for different microbial communities. Prominent DGGE bands of Bacteria and Archaea were purified and sequenced. The 16S rRNA gene sequences of the dominant archaeal bands found in the inoculum, and UASB sludge fed with raw sewage, CEPS pretreated wastewater, and synthetic sewage were closely associated with Methanosaeta concilii. In the UASB sludge fed with synthetic sewage, another dominant band associated with an uncultured archaeon 39-2 was found together with M. concilii.     

Development of a fixed-bed anammox reactor with high treatment potential

A plug-flow type anaerobic ammonium oxidation (anammox) reactor was developed using malt ceramics (MC) produced from carbonized spent grains as the biomass carriers for anammox sludge. Partial nitrified effluent of the filtrate from the sludge dehydrator of a brewery company was used as influent to a 20 L anammox reactor using MC. An average volumetric nitrogen removal rate (VNR) of 8.78 kg-N/m³/day was maintained stably for 76 days with 1 h of HRT. In a larger anammox reactor (400 L), an average VNR of 4.84 kg-N/m³/day could be maintained for 86 days during the treatment of low strength synthetic inorganic wastewater. As a result of bacterial community analysis for the 20 L anammox reactor, Asahi BRW1, probably originating from the wastewater collected at Asahi Breweries, was detected as the dominant anammox bacterium. These anammox reactors were characterized by a high NH₄-N removal capacity for low strength wastewater with a short hydraulic retention time.     

Study of microbial community structures in UASB sludge treating municipal wastewater by denaturing gradient gel electrophoresis of 16S rDNA

The structures of microbial communities in lab-scale upflow anaerobic sludge blanket (UASB) reactors for treating municipal wastewater with different ratios of COD soluble/ COD total were studied using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. The microbial structure of the inoculum sludge obtained from a full-scale UASB reactor of treating potato processing wastewater was compared with the structures of sludges collected from three lab-scale UASB reactors after eight months feeding with raw municipal wastewater, with CEPS (chemically enhanced primary sedimentation) pretreated municipal wastewater, and with a synthetic municipal sewage, respectively. Computer-aided numerical analysis of the DGGE fingerprints showed that the bacterial community underwent major changes. The sludges for treating raw and CEPS pretreated wastewater had very similar bacterial and archaeal communities (82% and 96% similarity) but were different from that for treating the synthetic sewage. Hence, despite     

Comparison of startup and anaerobic wastewater treatment in UASB, hybrid and baffled reactor

An experimental study was carried out to compare the performance of selected anaerobic high rate reactors operated simultaneously at 37?°C. The three reactors, namely upflow anaerobic sludge bed reactor (UASB), hybrid of UASB reactor and anaerobic filter (anaerobic hybrid reactor – AHR) and anaerobic baffled reactor (ABR), were inoculated with the anaerobic digested sludge from municipal wastewater treatment plant and tested with synthetic wastewater. This wastewater contained sodium acetate and glucose with balanced nutrients and trace elements (COD 6000?mg?·?l^?1). Organic loading rate (B _v ) was increased gradually from an initial 0.5?kg?·?m^?3?·?d^?1 to 15?kg?·?m^?3?·?d^?1 in all the reactors. From the comparison of the reactors' performance, the lowest biomass wash-out resulted from ABR. In the UASB, significant biomass wash-out was observed at the B _v 6?kg?·?m^?3?·?d^?1, and in the AHR at the B _v 12?kg?·?m^?3?·?d^?1. The demand of sodium bicarbonate for pH maintenance in ABR was two times higher as for UASB and AHR. The efficiency of COD removal was comparable for all three reactors – 80–90%. A faster biomass granulation was observed in the ABR than in the other two reactors. This fact is explained by the kinetic selection of filamentous bacteria of the Methanotrix sp. under a high (over 1.5?g?·?l^?1) acetate concentration.     

Decreased activity of a propionate degrading community in a UASB reactor fed with synthetic medium without molybdenum,tungsten and selenium

The composition and dynamics of the propionate degrading community in a propionate-fed upflow anaerobic sludge bed (UASB) reactor with sludge originating from an alcohol distillery wastewater treating UASB reactor was studied. The rather stable propionate degrading microbial community comprised relatives of propionate degrading Syntrophobacter spp., the hydrogen and formate consuming Methanospirillum hungatei and the acetate consuming Methanosaeta concilii. The effect of the long-term absence of molybdenum, tungsten and selenium from the feed to the UASB reactor on microbial community dynamics and activity was examined. Measurements for metal concentrations of the sludge and specific methanogenic activity tests with supplied molybdenum, tungsten and selenium were found to be unsuitable to detect the potential limitation of the microbial activity of the UASB sludge by these trace metals. During a long-term absence of molybdenum, tungsten and selenium from the feed to the UASB reactor, the methanogenic activity decreased while relatives of Smithella propionica and Pelotomaculum spp. competed with Syntrophobacter spp. for propionate consumption.     

Effect of starch addition on the biological conversion and microbial community in a methanol-fed UASB reactor during long-term continuous operation

The effect of starch addition on the microbial composition and the biological conversion was investigated using two upflow anaerobic sludge bracket (UASB) reactors treating methanolic wastewater: one reactor was operated with starch addition, and another reactor was operated without starch addition. Approximately 300 days of operation were performed at 30 kg COD/m³/d, and then, the organic load of the reactors was gradually increased to 120 kg COD/m³/d. Successful operation was achieved at 30 kg COD/m³/d in both reactors; however, the methanol-fed reactor did not perform well at 120 kg COD/m³/d while the methanol-starch-fed reactor did. The granule analysis revealed the granule developed further only in the methanol-starch-fed reactor. The results of the microbial community analysis revealed more Methanosaeta cells were present in the methanol-starch-fed reactor, suggesting the degradation of starch produced acetate as an intermediate, which stimulated the growth of Methanosaeta cells responsible for the extension of granules.     

Anaerobic treatment of distillery wastewater from barley-Shochu making by UASB

Distillery wastewater from barley-shochu making was anaerobically treated by a single upflow anaerobic sludge blanket (UASB), and stable operation at a volumetric TOC loading rate of 3 g/l·d could be attained by diluting raw wastewater to give a TOC concentration of less than 6,000 mg/l (18,000 mg/l as CODer). When the distribution of the concentrations of aliphatic acids at various levels within the reactor was investigated, it was found that the methanogenic gasification reaction did not occur in the sludge blanket of the reactor. Distillery wastewater from barley-shochu making with various TOC concentrations was preliminary adjusted to pH 7 and treated by a single passage without circulation of effluent to the bottom of the reactor. As a result, a maximum TOC removal rate (V_max) of 28.5 g/l·d and a saturation constant (K_s) of 0.63 g/l were obtained.     

Production of hydrogen from domestic wastewater in a pilot-scale microbial electrolysis cell

Addressing the need to recover energy from the treatment of domestic wastewater, a 120-L microbial electrolysis cell was operated on site in Northern England, using raw domestic wastewater to produce virtually pure hydrogen gas (100?±?6.4 %) for a period of over 3 months. The volumetric loading rate was 0.14 kg of chemical oxygen demand (COD) per cubic metre per day, just below the typical loading rates for activated sludge of 0.2–2 kg?COD?m^?3?day^?1, at an energetic cost of 2.3 kJ/g?COD, which is below the values for activated sludge 2.5–7.2 kJ/g?COD. The reactor produced an equivalent of 0.015 L?H₂?L^?1?day^?1, and recovered around 70 % of the electrical energy input with a coulombic efficiency of 55 %. Although the reactor did not reach the breakeven point of 100 % electrical energy recovery and COD removal was limited, improved hydrogen capture and reactor design could increase the performance levels substantially. Importantly, for the first time, a ‘proof of concept’ has been made, showing that this technology is capable of energy capture as hydrogen gas from low strength domestic wastewaters at ambient temperatures.     

Anammox bacteria enrichment in upflow anaerobic sludge blanket (UASB) reactor

We investigated the anaerobic ammonium oxidation (anammox) reaction in a labscale upflow anaerobic sludge blanket (UASB) reactor. Our aim was to detect and enrich the organisms responsible for the anammox reaction using a synthetic medium that contained low concentrations of substrates (ammonium and nitrite). The reactor was inoculated with granular sludge collected from a full-scale anaerobic digestor used for treating brewery wastewater. The experiment was performed during 260 days under conditions of constant ammonium concentration (50 mg NH₄/⁺-N/L) and different nitrite concentrations (50∼150 mg NO₂-N/L). After 200 days, anammox activity was observed in the system. The microorganisms involved in this anammox reaction were identified as CandidatusB. Anammoxidans andK. Stuttgartiensis using fluorescencein situ hybridization (FISH) method.     

Performance and microbial community analysis of a pilot-scale UASB for corn-ethanol wastewater treatment

The performance and microbial community structure of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor inoculated with flocculent sludge were investigated over 52 days. The characteristics of corn-ethanol wastewater were as follows: COD_Cr, 1,050–4,970 mg l^?1; ammonia, 14–298 mg l^?1; and alkalinity, 332–2,867 mg l^?1. The UASB could start up smoothly with a hydraulic loading rate lower than 180 l h^?1 and a ratio of volatile fatty acid versus alkalinity between 0.04 and 0.48. The maximum gas production rate was 432 l h^?1 and the highest volumetric loading rate of 7.2 kg m^?3 day^?1 was obtained after 48 days. The 1 mm granules could form a complex network and were composed of many Methanosaeta. Aceticlastic methanogens served as a dominant methanogenic group, which accounted for the relatively high resistance to shock loading.     

Development of anaerobic sludge bed (ASB) reactor technologies for domestic wastewater treatment: motives and perspectives

During the treatment of raw domestic wastewater in the upflow anaerobic sludge blanket (UASB) reactor, the suspended solids (SS) present in the wastewater tend to influence negatively the methanogenic activity and the chemical oxygen demand (COD) conversion efficiency. These problems led to the emergence of various anaerobic sludge bed systems such as the expanded granular sludge bed (EGSB), the upflow anaerobic sludge blanket (UASB)-septic tank, the hydrolysis upflow sludge bed (HUSB), the two-stage reactor and the anaerobic hybrid (AH) reactor. However, these systems have, like the UASB reactor, limited performance with regard to complete treatment (e.g., removal of pathogens). In this respect, a new integrated approach for the anaerobic treatment of domestic wastewater is suggested. This approach combines a UASB reactor and a conventional completely stirred tank reactor (CSTR) for the treatment of the wastewater low in SS and sedimented primary sludge, respectively. The principal advantages of the proposed system are energy recovery from organic waste in an environmentally friendly way; lowering the negative effect of suspended solids in the UASB reactor; production of a high quality effluent for irrigation; and prevention of odour problems.     

Effect of nickel deprivation on methanol degradation in a methanogenic granular sludge bioreactor

The effect of omitting nickel from the influent on methanol conversion in an Upflow Anaerobic Sludge Bed (UASB) reactor was investigated. The UASB reactor (30°C, pH 7) was operated for 261 days at a 12-h hydraulic retention time (HRT) and at organic loading rates (OLRs) ranging from 2.6 to 7.8 g COD l reactor⁻¹ day⁻¹. The nickel content of the sludge decreased by 66% during the 261-day reactor run because of washout and doubling of the sludge bed volume. Nickel deprivation initially had a strong impact on the methanogenic activity of the sludge with methanol; e.g., after 89 days of operation, this activity was doubled by adding 2 μM nickel. Upon prolonged UASB reactor operation, methanol and VFA effluent concentrations decreased whereas the sludge lost its response to nickel addition in activity tests. This suggests that a less nickel-dependent methanol-converting sludge had developed in the UASB reactor. Received 09 April 2002/ Accepted in revised form 13 July 2002     

Process contribution evaluation for COD removal and energy production from molasses wastewater in a BioH<Subscript>2</Subscript>–BioCH<Subscript>4</Subscript>–MFC-integrated system

In this study, a three-stage-integrated process using the hydrogenic process (BioH₂), methanogenic process (BioCH₄), and a microbial fuel cell (MFC) was operated using molasses wastewater. The contribution of individual processes to chemical oxygen demand (COD) removal and energy production was evaluated. The three-stage integration system was operated at molasses of 20 g-COD L^?1, and each process achieved hydrogen production rate of 1.1 ± 0.24 L-H₂ L^?1 day^?1, methane production rate of 311 ± 18.94 mL-CH₄ L^?1 day^?1, and production rate per electrode surface area of 10.8 ± 1.4 g m^?2 day^?1. The three-stage integration system generated energy production of 32.32 kJ g-COD^?1 and achieved COD removal of 98 %. The contribution of BioH₂, BioCH₄, and the MFC reactor was 20.8, 72.2, and, 7.0 % of the total COD removal, and 18.7, 81.2, and 0.16 % of the total energy production, respectively. The continuous stirred-tank reactor BioH₂ at HRT of 1 day, up-flow anaerobic sludge blanket BioCH₄ at HRT of 2 days, and MFC reactor at HRT of 3 days were decided in 1:2:3 ratios of working volume under hydraulic retention time consideration. This integration system can be applied to various configurations depending on target wastewater inputs, and it is expected to enhance energy recovery and reduce environmental impact of the final effluent.     

Improvement of the anaerobic treatment of potato processing wastewater in a UASB reactor by co-digestion with glycerol

The effect of three different types of glycerol on the performance of up-flow anaerobic sludge blanket (UASB) reactors treating potato processing wastewater was investigated. High COD removal efficiencies were obtained in both control and supplemented UASB reactors (around 85%). By adding 2 ml glycerol product per liter of raw wastewater, the biogas production could be increased by 0.74 l biogas ml⁻¹ glycerol product, which leads to energy values in the range of 810–1270 kWh_electric per m³ product. Moreover, a better in-reactor biomass yield was observed for the supplemented UASB reactor (0.012 g VSS g⁻¹ COD_removed) compared to the UASB control (0.002 g VSS g⁻¹ COD_removed), which suggests a positive effect of glycerol on the sludge blanket growth.     

Analysis, evaluation, and optimization of kinetic parameters for performance appraisal and design of UASB reactors

Studies have been undertaken to explore the applicability of different kinetic models for the performance appraisal of upflow anaerobic sludge blanket (UASB) reactors treating wastewater in the range of 300-4000 mg COD/l. Three kinetic models namely, Monod, Grau second-order, and Haldane model are considered for the analysis. Both linear and nonlinear regressions have been performed to examine the best-fit among the kinetic models. In this process, five error analysis methods have been used to analyze the data. Apart from optimization of kinetic coefficients with minimization of associated errors, prediction of effluent COD has also been undertaken to verify the applicability of kinetic models. In both the cases, Grau second-order model is found to be the best class of fit for wide range of data sets in UASB reactor.     

Reactivation of effluent granular sludge from a high-rate Anammox reactor after storage

In this study, effluent sludge from a high-rate Anammox reactor was used to re-start new Anammox reactors for the reactivation of Anammox granular sludge. Different start-up strategies were evaluated in six upflow anaerobic sludge blanket (UASB) reactors (R₁–R₆) for their effect on nitrogen removal performance. Maximal nitrogen removal rates (NRRs) greater than 20 kg N/m³/day were obtained in reactors R₃–R₅, which were seeded with mixed Anammox sludge previously stored for approximately 6 months and 1 month. A modified Boltzmann model describing the evolution of the NRR fit the experimental data well. An amount of sludge added to the UASB reactor or decreasing the loading rate proved effective in relieving the substrate inhibition and increasing the NRR. The modified Stover–Kincannon model fit the nitrogen removal data in the Anammox reactors well, and the simulation results showed that the Anammox process has great nitrogen removal potential. The observed inhibition in the Anammox reactors may have been caused by high levels of free ammonia. The sludge used to seed the reactors did not settle well; sludge flotation was observed even after the reactors were operated for a long time at a floating upward velocity (F_s) of greater than 100 m/h. The settling sludge, however, exhibited good settling properties. Scanning electron microscopy showed that the Anammox granules consisted mainly of spherical and elliptical bacteria with abundant filaments on their surface. Hollows in the granules were also present, which may have contributed to sludge floatation.     

Comparative anaerobic treatment of wastewater from pharmaceutical,brewery, paper and amino acid producing industries

This study concerned the anaerobic treatment of five different industrial wastewaters with a diverse and complex chemical composition. The kinetics of biotransformation of this wastewater at different chemical oxygen demand (COD) were studied in a batch reactor. Wastewater from an amino acid producing industry (Fermex) and from a tank that received several types of wastewaters (collector) contained 0.83 g l⁻¹ and 0.085 g l⁻¹ sulfate, respectively. During the study period of 20 days, methane formation was observed in all types of wastewaters. Studies on COD biodegradation showed the reaction velocity was higher for Fermex wastewater and lower for collector wastewater, with values of 0.0022 h⁻¹ and 0.0011 h⁻¹, respectively. A lower methanogenic activity of 0.163 g CH₄ day⁻¹ g⁻¹ volatile suspended solids (VSS) and 0.20 g CH₄ day⁻¹ g⁻¹ VSS, respectively, was observed for paper producing and brewery wastewater. Adapted granular sludge showed the best biodegradation of COD during the 20-day period. The sulfate-reducing activity in pharmaceutical and collector wastewater was studied. A positive effect of sulfate-reducing activity on methanogenic activity was noted for both types of wastewaters, both of which contained sulfate ions. All reactions of methane generation for the tested industrial wastewaters were first-order. The results of this study suggest that the tested wastewaters are amenable to anaerobic treatment.

     

Effective anaerobic treatment of fresh leachate from MSW incineration plant and dynamic characteristics of microbial community in granular sludge

We investigated the treatment of fresh leachate from municipal solid waste incineration plants with high-strength organics using a lab-scale expanded granular sludge bed (EGSB) reactor. The reactor was operated at a mesophilic temperature (33 °C) for 118 days. The influent chemical oxygen demand (COD) of the leachate gradually increased to over 70,000 mg/L, and the organic loading rate increased to 18 kg COD/(m³?day). An average COD removal efficiency of 86.7 % was achieved when the reactor was fed with raw leachate, which suggests the feasibility of the EGSB process for leachate treatment. The microbial communities in the sludge from the reactor during the trial operation were constructed by denaturing gradient gel electrophoresis, clone libraries, and real-time quantitative polymerase chain reaction. The dominant group for archaea was Methanosaeta, with 68.4 % proportion at the start of the operation, and then changed to Methanosarcina, with a proportion of 62.3 %, after 118 days of operation. The dominant group of eubacteria was confirmed to be Firmicutes throughout the operation process, with the proportion increasing from >50 to 81.2 %. Almost all the operational taxonomic units of Firmicutes belonged to the order Clostridiales, with characteristic spore formation. The microbial diversity of the population was low under raw leachate as feed in the reactor. The dynamics of the microbial community in the anaerobic granular sludge was discussed relating with the operating status of the EGSB reactor.