Upflow Anaerobic Sludge Bed Reactor Research Articles

Phosphorus removal from UASB reactor effluent by reactive media filtration

ABSTRACT The phosphorus (P) and BOD7 removal performance of an upflow packed bed reactor (PBR) filled with two reactive filter media was studied over 50 weeks. The lower one-fifth of the reactor was filled with calcium–silicate–hydrate (Sorbulite®) and the upper four-fifth with calcium–silicate (Polonite®). A laboratory-scale upflow anaerobic sludge bed reactor (UASB) delivered wastewater to the PBR. A model was developed to describe the gradient in P concentration change in the reactor, based on reaction kinetics. The reaction terms were assumed to follow the Langmuir isotherm, based on the results obtained in a batch test. First, a comparison was made between experimental and simulated results. The capability of the model to forecast P removal capacity was then tested for three hypothetical cases: (i) reactor filled with Sorbulite and Polonite, (ii) reactor filled with only Sorbulite, and (iii) reactor filled with only Polonite. Finally, a sensitivity analysis was performed for the main parameters in the model. The average removal of P and BOD7 from the UASB effluent was 98% and 90%, respectively. The starting pH of the dual-medium effluent was 12.2 and decreased gradually over time to 11.1. The simulation both overestimated and underestimated mean measured P removal but was within the range of maximum and minimum measured values. The hypothetical cases revealed that most P was removed by Polonite due to calcium phosphate precipitation. The removal capacity of the two filter materials and their layer height in the reactor were the most sensitive parameters in the simulation.

Gas-enhanced operation and stepwise organic stressing as a new alternative in realising successful sludge granulation in high-rate anaerobic bioreactor for wastewater treatment

ABSTRACTAnaerobic biotechnology is becoming the method of choice for many types of wastewater treatment. Application of granular sludge in the upflow anaerobic sludge bed (UASB) is important in maximising the overall treatment capacity benefiting from its fast settling ability and excellent biological activities. This study explores a new alternative for achieving sludge granulation in a sulfidogenic UASB reactor. Granules were first observed at day 30 and achieved the average diameters of 820 µm at day 162. The scanning electron microscope analysis showed that the granules have a regular spherical-shaped outline boundary, and a rough outer surface layer with a channel-like porous structure. The confocal laser scanning microscopy analysis illustrated that the extracellular polymeric substances (EPS) were more evenly distributed across the granules under a gas-enhanced operation than at the control stage. For the control stage operation without gas-enhanced operation, no granule disintegration was observed...

A super high-rate sulfidogenic system for saline sewage treatment

This study proposes a novel approach to resolve the challenging issue of sludge bed clogging in a granular sulfate-reducing upflow sludge bed (GSRUSB) reactor by means of introducing intermittent gas sparging to advance it into a super high-rate anaerobic bioreactor. Over a 196-day lab-scale trial, the GSRUSB system was operated from nominal hydraulic retention time of 4-hr to 40-min and achieved the highest organic loading rate of 13.31 kg COD/m3·day which is substantially greater than the typical loading of 2.0–3.5 kg COD/m3·day in a conventional upflow anaerobic sludge bed reactor treating dilute organic strength wastewater. The average organic removal efficiency and total dissolved sulfide of this system were 90 ± 4.2% and 158 ± 28 mg S/L, while organics residual in the effluent was 34 ± 14 mg COD/L. The control stage (without gas sparging) revealed that the sludge bed clogging happened concomitantly with the significant drop in extracellular polymeric substance content of granular sludge, through relevant chemical measurements and confocal laser scanning microscopy analyses. On the other hand, compared with increasing the effluent recirculation ratio (from 1.4 to 5), the three-dimensional computational fluid dynamics modeling in combination with energy dissipation analysis demonstrated that the gas sparging (at a superficial gas velocity of 0.8 m s−1) can create a 23 times higher liquid shear as well as enhanced particle attrition. Overall, this study not only developed a super high-rate anaerobic bioreactor for saline sewage treatment, but also shed light on the role of intermittent gas sparging in control of sludge bed clogging for anaerobic bioreactors.

Biomethanation of Syngas Using Anaerobic Sludge: Shift in the Catabolic Routes with the CO Partial Pressure Increase.

Syngas generated by thermal gasification of biomass or coal can be steam reformed and purified into methane, which could be used locally for energy needs, or re-injected in the natural gas grid. As an alternative to chemical catalysis, the main components of the syngas (CO, CO2, and H2) can be used as substrates by a wide range of microorganisms, to be converted into gas biofuels, including methane. This study evaluates the carboxydotrophic (CO-consuming) methanogenic potential present in an anaerobic sludge from an upflow anaerobic sludge bed (UASB) reactor treating waste water, and elucidates the CO conversion routes to methane at 35 ± 3°C. Kinetic activity tests under CO at partial pressures (pCO) varying from 0.1 to 1.5 atm (0.09–1.31 mmol/L in the liquid phase) showed a significant carboxydotrophic activity potential for growing conditions on CO alone. A maximum methanogenic activity of 1 mmol CH4 per g of volatile suspended solid and per day was achieved at 0.2 atm of CO (0.17 mmol/L), and then the rate decreased with the amount of CO supplied. The intermediary metabolites such as acetate, H2, and propionate started to accumulate at higher CO concentrations. Inhibition experiments with 2-bromoethanesulfonic acid (BES), fluoroacetate, and vancomycin showed that in a mixed culture CO was converted mainly to acetate by acetogenic bacteria, which was further transformed to methane by acetoclastic methanogens, while direct methanogenic CO conversion was negligible. Methanogenesis was totally blocked at high pCO in the bottles (≥1 atm). However it was possible to achieve higher methanogenic potential under a 100% CO atmosphere after acclimation of the sludge to CO. This adaptation to high CO concentrations led to a shift in the archaeal population, then dominated by hydrogen-utilizing methanogens, which were able to take over acetoclastic methanogens, while syntrophic acetate oxidizing (SAO) bacteria oxidized acetate into CO2 and H2. The disaggregation of the granular sludge showed a negative impact on their methanogenic activity, confirming that the acetoclastic methanogens were the most sensitive to CO, and a contrario, the advantage of using granular sludge for further development toward large-scale methane production from CO-rich syngas.

Performance of a microbial fuel cell-based biosensor for online monitoring in an integrated system combining microbial fuel cell and upflow anaerobic sludge bed reactor

A hybrid system integrating a microbial fuel cell (MFC)-based biosensor with upflow anaerobic sludge blanket (UASB) was investigated for real-time online monitoring of the internal operation of the UASB reactor. The features concerned were its rapidity and steadiness with a constant operation condition. In addition, the signal feedback mechanism was examined by the relationship between voltage and time point of changed COD concentration. The sensitivity of different concentrations was explored by comparing the signal feedback time point between the voltage and pH. Results showed that the electrical signal feedback was more sensitive than pH and the thresholds of sensitivity were S=3×10−5V/(mg/L) and S=8×10−5V/(mg/L) in different concentration ranges, respectively. Although only 0.94% of the influent COD was translated into electricity and applied for biosensing, this integrated system indicated great potential without additional COD consumption for real-time monitoring.

Novel zero-valent iron-assembled reactor for strengthening anammox performance under low temperature.

To further expand the application of anammox biotechnology, a novel zero-valent iron-assembled upflow anaerobic sludge bed reactor was employed to strengthen anammox performance under low temperature and shock load. Packed with sponge iron and polyester sponge, this novel reactor could speed up the recovery of anammox activity in 12days and improve the adaptability of anammox bacteria at the temperature of 10-15°C. The high nitrogen loading rate of 1109.2mg N/L/day could be adapted in 27days and the new nitrogen pathway under the effect of sponge iron was clarified by batch experiment. Moreover, the real-time quantitative PCR analysis and Illumina MiSeq sequencing verified the dominant status of Candidatus Kuenenia stuttgartiensis and planctomycete KSU-1, as well as demonstrated the positive role of sponge iron on anammox microorganisms' proliferation. The findings might be beneficial to popularize anammox-related processes in municipal and industrial wastewater engineering.

Anaerobic digestion of wastewater from the production of bleached chemical thermo‐mechanical pulp – higher methane production for hardwood than softwood

ABSTRACTBACKGROUNDChemical thermo‐mechanical pulp (CTMP) mills holds a large biomethane potential in their wastewater. Their broadened market has involved increased bleaching and utilization of different raw materials. Therefore, the main aim of this study was to obtain and maintain a well‐functioning anaerobic digestion (AD) process, with a high methane yield and total organic carbon (TOC) reduction, when digesting CTMP wastewater, from different production protocols including shifts in raw material and bleaching. A lab‐scale upflow anaerobic sludge bed (UASB) reactor was used for the tests.RESULTSThe variations in raw material (spruce, birch and aspen) and consequently in TOC‐loading (3.6–6.6 kg TOC m−3 and day−1) did not affect the UASB process negatively. Methane production values from 360 to 500 NmL g−1 TOC were obtained, with the highest yield for wastewater from the production of birch‐ followed by aspen‐ and spruce pulp. The acetic acid and filtered‐TOC (fTOC) reduction ranged from 90 to 95% and 61 to 73%, respectively.CONCLUSIONSA well‐functioning process maintained during shifts in raw material for pulp production which shows that AD is feasible for CTMP mills with a diversified product portfolio. Furthermore, the increased use of hardwood and bleaching will most likely increase their potential as a biomethane producer. © 2016 Society of Chemical Industry

Insight into the influence of magnesium on the properties of heterotrophic denitrifying granules

This paper examined the influence of magnesium on denitrifying sludge. Two up-flow anaerobic sludge bed (UASB) reactors were used in the study. R1 was continuously supplied with 50mgL−1 of divalent magnesium in the wastewater and R0 was used as a control without magnesium. On the 258th day, the sludge properties in R0 and R1 were analyzed when the nitrogen loading rates were both 36.0 kgN m−3 d−1 and the nitrogen removal rates of R0 and R1 were 33.8 and 34.6 kgN m−3 d−1, respectively. The diameters of R0 and R1 were 0.95and1.35mm, settling velocity (74.5±20.8 and102.0±22.6m h−1), extracellular polymeric substance (60.8±2.1 and76.0±2.7mgg−1VSS)and specific denitrifying activity (794.4±9.6 and825.6±4.9 mgN d−1) were also compared. These results addressed that the addition of magnesium to denitrifying reactor is an effective alternative to enhance sludge properties.

An Exploratory Study on the Pathways of Cr (VI) Reduction in Sulfate-reducing Up-flow Anaerobic Sludge Bed (UASB) Reactor

Electroplating wastewater contains both Cr (VI) and sulfate. So Cr (VI) removal under sulfate-rich condition is quite complicated. This study mainly investigates the pathways for Cr (VI) removal under biological sulfate-reducing condition in the up-flow anaerobic sludge bed (UASB) reactor. Two potential pathways are found for the removal of Cr (VI). The first one is the sulfidogenesis-induced Cr (VI) reduction pathway (for 90% Cr (VI) removal), in which Cr (VI) is reduced by sulfide generated from biological reduction of sulfate. The second one leads to direct reduction of Cr (VI) which is utilized by bacteria as the electron acceptor (for 10% Cr (VI) removal). Batch test results confirmed that sulfide was oxidized to elemental sulfur instead of sulfate during Cr (VI) reduction. The produced extracellular polymeric substances (EPS) provided protection to the microbes, resulting in effective removal of Cr (VI). Sulfate-reducing bacteria (SRB) genera accounted for 11.1% of the total bacterial community; thus they could be the major organisms mediating the sulfidogenesis-induced reduction of Cr (VI). In addition, chromate-utilizing genera (e.g. Microbacterium) were also detected, which were possibly responsible for the direct reduction of Cr (VI) using organics as the electron donor and Cr (VI) as the electron acceptor.

Super-high-rate performance and its mechanisms of a spiral symmetry stream anaerobic bioreactor

An anaerobic process, termed the spiral symmetry stream anaerobic bioreactor (SSSAB), had been developed by setting inner components of elliptic plates and gas collection pipes. And our previous study had demonstrated that a SSSAB was more efficient and stable than a same-sized up-flow anaerobic sludge bed (UASB) reactor. This study investigated the optimum treatment efficiency and super-high-rate mechanisms for the SSSAB. The performance with super-high-rate organic loading rate (OLR), volumetric removal rate (VRR) and improved volumetric methane production (VMP) of 361.5kgCOD/(m3d), 268.3kgCOD/(m3d) and 73.0m3/(m3d), respectively, were revealed for a lab-scale SSSAB. The elliptic plates set in the SSSAB could form spiral flow which increased along with the shortening of hydraulic retention time (HRT). The super-high-rate mechanisms were analyzed in terms of biomass, transfer condition around granules and sludge activity. The sludge retention ability in the SSSAB was achieved by the gas entrapment role of elliptic plates and gas collection pipes. The transfer condition around the granular sludge was changed to adapt to the variation of OLR. The rich channels of granules provided a favorable environment for substrate in and product out. The difference of methane productions between the batch test and the reactor operation illustrated that high substrate concentration and especially dramatic mixing condition in the SSSAB were significantly responsible for the super-high efficiency of SSSAB.

A combined upflow anaerobic sludge bed, aerobic, and anoxic fixed-bed reactor system for removing tetramethylammonium hydroxide and nitrogen from light-emitting diode wastewater

ABSTRACTA laboratory study using a combined upflow anaerobic sludge bed (UASB) and aerobic and anoxic fixed-bed reactor system was undertaken to explore its capability for removing tetramethylammonium hydroxide (TMAH) and nitrogen from light-emitting diode wastewater. When the organic loading rate was maintained at 0.26–0.65 kg TMAH m−3 d−1, the UASB reactor removed 70–100% of TMAH through methanogenesis. When the -N loading rate was maintained at 0.73–1.4 kg -N m−3 d−1, the aerobic reactor oxidized 31–59% of -N to -N through nitritation. When the nitrogen loading rate was maintained at 0.42–0.75 kg N m−3 d−1, the anoxic reactor removed 27–63% of nitrogen through anammox. The performance data of the combined reactor system agreed well with the stoichiometric relationships of methanogenesis, nitritation, and anammox. The batch studies showed that a higher initial TMAH concentration of up to 2520 mg L−1 gave a higher methanogenic activity of up to 16 mL CH4 g−1 VSS d−1. An increase in the initial TMAH concentration of up to 500 mg L−1 gradually decreased the activity of ammonia-oxidizing bacteria; whereas an increase in the initial TMAH concentration of up to 47 mg L−1 imposed a marked inhibiting effect on the activity of anammox bacteria.

Mitigation of micropollutants for black water application in agriculture via composting of anaerobic sludge

The excess sludge from Up-flow anaerobic sludge bed (UASB) reactor operated on source separated toilet wastewater is a potential source of nutrients and organic matter. It can be further stabilized and dried by composting and applied as a soil amendment. Presence of pathogens, heavy metals and micropollutants in the compost derived from anaerobic sludge is thus undesirable. This paper focuses on removal of micropollutants, typically present in domestic wastewater, via composting of UASB sludge with waste wood. Estrone, diclofenac, ibuprofen, metoprolol, carbamazepine, galaxolide and triclosan were spiked to a mixture of UASB sludge and waste wood. Their concentrations were monitored during 92 days of composting at controlled temperature conditions. All studied micropollutants were removed at various rates with overall removal ranging from 99.9% for ibuprofen, diclofenac and estrone to 87.8% for carbamazepine. Accumulation of methyltriclosan as by-product of triclosan degradation was observed. The prospects and limitations of the integration of a composting process into Source Separated Sanitation concepts are discussed.

An alternative anaerobic treatment process for treatment of heavy oil refinery wastewater containing polar organics

Heavy oil is an important part of energy sources, but the refining wastewater is difficult to treat by the conventional anaerobic process, which has low efficiency and poor ability to resist impact load. In this study, an up-flow anaerobic sludge bed (UASB) reactor was applied to treat heavy oil refinery wastewater containing large amounts of polar organics. Through a progressive increase of hydraulic conditions, the average removal efficiencies of COD and total oil reached 70% and 72%, respectively, at an organic loading rate (OLR) of 3.44kg COD/m3d. GC–MS analysis revealed that more biodegradable organic acids and alcohols were generated and macromolecular polar organics were degraded into small molecular intermediates after UASB treatment. The morphology observation of the sludge demonstrated that granular sludge with an average particle size of 1mm was formed. Moreover, the predominant species and microbial community shift could reflect the performance of the reactor. The long-term operation of UASB exhibited excellent polar organic removal efficiency. The study demonstrated the potential of UASB as an alternative for high-efficiency anaerobic treatment of heavy oil refinery wastewater.

Efficient anaerobic treatment of synthetic textile wastewater in a UASB reactor with granular sludge enriched with humic acids supported on alumina nanoparticles.

A novel technique to co-immobilize humus-reducing microorganisms and humic substances (HS), supported on γ-Al2O3 nanoparticles (NP), by a granulation process in an upflow anaerobic sludge bed (UASB) reactor is reported in the present work. Larger granules (predominantly between 1 and 1.7mm) were produced using NP coated with HS compared to those obtained with uncoated NP (mostly between 0.25 and 0.5mm). The HS-enriched granular biomass was then tested for its capacity to achieve the reductive decolorization of the recalcitrant azo dye, reactive red 2 (RR2), in the same UASB reactor operated with a hydraulic residence time of 12h and with glucose as electron donor. HS-enriched granules achieved higher decolorization and COD removal efficiencies, as compared to the control reactor operated in the absence of HS, in long term operation and applying high concentrations of RR2 (40-400mg/L). This co-immobilizing technique could be attractive for its application in UASB reactors for the reductive biotransformation of several contaminants, such as nitroaromatics, poly-halogenated compounds, metalloids, among others.

Continuous removal and recovery of palladium in an upflow anaerobic granular sludge bed (UASB) reactor

AbstractBACKGROUNDThe aim of this study was to investigate the feasibility of utilizing a continuous‐flow anaerobic granular sludge bed (UASB) reactor for the removal of palladium (II) from aqueous streams and the recovery of this precious metal as biogenic Pd(0). Anaerobic methanogenic granular sludge has been recently shown to reduce Pd(II) in the presence of a suitable electron donor leading to the formation of biomass‐associated Pd(0).RESULTSTwo laboratory‐scale UASB reactors were fed with ethanol or acetate, in order to compare their performance in terms of Pd removal and reduction. Pd(II) was added in two periods of increasing concentration, 5 mg Pd(II) L−1 and then 15 mg Pd(II) L−1. Extensive removal of Pd (up to 99%), was attained in both reactors. X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDS) analysis confirmed significant differences in the content of Pd(0) in the biomass, depending on the electron donor used. The main mechanisms of Pd(II) removal when acetate and ethanol were used as electron donor were biosorption and reduction to Pd(0) by biogenic H2 released as fermentation product, respectively.CONCLUSIONSThe results obtained demonstrate that it is possible to apply a continuous process for Pd reduction and recovery using a methanogenic consortium. © 2015 Society of Chemical Industry

Anaerobic degradation of dairy wastewater in intermittent UASB reactors: influence of effluent recirculation

This work studied the influence of effluent recirculation upon the kinetics of anaerobic degradation of dairy wastewater in the feedless phase of intermittent upflow anaerobic sludge bed (UASB) reactors. Several laboratory-scale tests were performed with different organic loads in closed circuit UASB reactors inoculated with adapted flocculent sludge. The data obtained were used for determination of specific substrate removal rates and specific methane production rates, and adjusted to kinetic models. A high initial substrate removal was observed in all tests due to adsorption of organic matter onto the anaerobic biomass which was not accompanied by biological substrate degradation as measured by methane production. Initial methane production rate was about 45% of initial soluble and colloidal substrate removal rate. This discrepancy between methane production rate and substrate removal rate was observed mainly on the first day of all experiments and was attenuated on the second day, suggesting that the feedless period of intermittent UASB reactors treating dairy wastewater should be longer than one day. Effluent recirculation expressively raised the rate of removal of soluble and colloidal substrate and methane productivity, as compared with results for similar assays in batch reactors without recirculation. The observed bed expansion was due to the biogas production and the application of effluent recirculation led to a sludge bed contraction after all the substrates were degraded. The settleability of the anaerobic sludge improved by the introduction of effluent recirculation this effect being more pronounced for the higher loads.

Full-scale hybrid constructed wetlands incorporated with an initial anaerobic stage for domestic wastewater treatment in a drinking water catchment area

This study involves sequential treatment of domestic wastewater by anaerobic reactors followed by horizontal (HSSF-CW) and vertical (VSSF-CW) subsurface flow-constructed wetlands. Two full-scale systems constructed in two villages were operated in order to treat domestic wastewaters of about 2,000 and 500 inhabitants. Anaerobic treatment of domestic wastewater served as a pretreatment step before the constructed wetland (CW) systems. Anaerobic pretreatment was performed by an upflow anaerobic sludge bed reactor or an anaerobic baffled reactor. Anaerobically pretreated wastewater was first introduced into parallel HSSF-CWs and then parallel VSSF-CWs before being discharged. Efficient treatment of wastewaters of the two villages was particularly important since they are located in the watershed of a drinking water reservoir. The treatment efficiencies of systems were 88 and 83% for chemical oxygen demand, 89 and 81% for BOD5, 57 and 39% for total nitrogen, 55 and 53% for total phosphorus, 94 and 90% for total suspended solids removal on average, respectively, in Balcik and Orucoglu villages. The effluent concentrations met the discharge limits. The study showed that hybrid CW system with anaerobic pretreatment is an effective method to treat domestic wastewaters of small communities with populations below 2,000.

Anaerobic digestion of alkaline bleaching wastewater from a kraft pulp and paper mill using UASB technique

Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250 ± 50 vs. 120 ± 30 NmL g ) and reduction of filtered total organic carbon (fTOC) (60 ± 5 vs. 43 ± 6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14 h. Lowering the HRT (from 13.5 to 8.5 h) did not significantly affect the process, and the stable performance at 8.5 h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization.

Biotrickling Filtration of Biogas Produced from the Wastewater Treatment Plant of a Brewery

AbstractThe performance of a lab-scale biotrickling filter treating H2S from biogas produced from an upflow anaerobic sludge bed reactor of the wastewater-treatment plant of a brewery was evaluated. A sulfide-oxidizing culture obtained from the anaerobic sludge of the same upflow anaerobic sludge bed reactor was immobilized on polyurethane foam. The nitrate and nitrite (final electron acceptor) depletion on the trickling medium resulted in remarkable destabilization in the performance of the system. The optimum temperature was in the range from 31 to 42°C (removal efficiency=91.8±5.5%). At a temperature of 22°C the removal efficiency reduced to 39% [inlet load (IL)=5.3 gS-H2S m−3 h−1, empty bed residence time (EBRT)=2.9 min]. Trickling liquid velocity (TLV) of 4.4, 7.4, and 11 m h−1 did not affect the system at EBRT of 6.2 min (removal efficiency=94.2±1.3%, IL=1.86±0.18 gS m−3 h−1). A TLV effect was observed at an EBRT of 1.6 min where the removal efficiency decreased from 50.9% (4.4 m h−1) to 33.7%...

Prediction and quantifying parameter importance in simultaneous anaerobic sulfide and nitrate removal process using artificial neural network.

The present investigation deals with the prediction of the performance of simultaneous anaerobic sulfide and nitrate removal in an upflow anaerobic sludge bed (UASB) reactor through an artificial neural network (ANN). Influent sulfide concentration, influent nitrate concentration, S/N mole ratio, pH, and hydraulic retention time (HRT) for 144days' steady-state condition were the inputs of the model; whereas output parameters were sulfide removal percentage, nitrate removal percentage, sulfate production percentage, and nitrogen production percentage. The prediction performance was evaluated by calculating root mean square error (RMSE), mean absolute error (MAE), mean absolute relative error (MARE), and determination coefficient (R (2)) values. Generally, the ANN model exhibited good prediction of the simultaneous sulfide and nitrate removal process. The effect of five input parameters to the performance of the reactor was quantified and compared using the connection weights method, Garson's algorithm method, and partial derivatives (PaD) method. The results showed that HRT markedly affects the performance of the reactor.