Performance Of Upflow Anaerobic Sludge Blanket Reactor Research Articles

Performance enhancement of up-flow anaerobic sludge blanket reactor for psychrophilic temperature during the dry season: Kality wastewater treatment plant

The main purpose of wastewater treatment plant (WWTP) is to reduce organic and inorganic pollutants to meet standards. But WWTPs employing up flow anaerobic sludge blanket (UASB) reactors under psychrophilic temperature are currently removing about 55% chemical oxygen demand (COD) and 70% total dissolved solids (TSS). The research was done to increase the treatment efficiencies of UASB reactor working under psychrophilic conditions through optimization of operational parameters like temperature, organic loading rate (OLR), pH and hydraulic retention time (HRT). Experimentation was carried out in a 0.0486 m3 square-shaped pilot-scale UASB reactor. Experimental design response surface method (RSM) for performance enhancement and optimization of UASB reactor operational parameters through five levels of central composite design (CCD) was used. The optimized operational parameters obtained from CCD-RSM were as follows: temperature of 21.58 °C, OLR of 2.99 kg COD/m3.d, HRT of 4.37hrs and pH of 6.3. Using optimized parameters, tests yielded efficiencies of 92.70%, 99.06%, and 94.50% for COD, TSS, and volatile suspended solid (VSS) respectively. The outlet concentrations of alkalinity, and volatile fatty acids (VFA), were found to be lower than the inlet concentrations. The alkalinity in the system accepts the hydrogen ion released by acids and the system is taken over by methanogensis to maintain the pH. The outlet concentration of sulfate ion was found to be increasing due to inhabitation of sulfur-reducing bacteria by an anaerobic condition of VFA and alkalinity at a pH less than 7.8.This process favors the production of CH4 than H2S gas. In general, there was a high likelihood of improving the performance of UASB reactor operating at psychrophilic temperature by optimizing operational parameters.

A comparative study for hybrid UASB reactor performance using polyethylene media and luffa sponge as biofilm support.

This paper study the performance of a lab-scale hybrid up-flow anaerobic sludge blanket (UASB) reactor treating low-strength synthetic wastewater using different biofilm supporting materials. Two identical reactors are constructed and operated at constant up-flow velocity of 0.1m/hr., inflow rate of 9.76L/d, and hydraulic retention time (HRT) of 8.26hours. The Start-up phase, using seed sludge for existing wastewater treatment plant, lasted until the efficiency of chemical oxygen demand (COD) removal of both reactors reached 80%. Polyethylene (PE) media are added to one of the reactors and luffa sponge is used in the second reactor. Results show increased COD removal efficiency up to about 90% at 20°C and biogas production rates from 3.8*10-3 till 7.5*10-3m3 CH4/kg CODr using PE media. The COD removal efficiency reaches about 95% at 20°C using luffa sponge and biogas production rates up to 6.5*10 -3m3 CH4/kg CODr are achieved before clogging problem is observed. Effect of HRT reduction, from 8.26 to 4.13hours, on removing clogging is investigated. Reduction in COD removal efficiencies is observed at low ambient temperatures during seasonal variations of 15-25°C. AFM and SEM analysis are used to examine sludge granulation and biofilm formation.

Performance and Kinetic Evaluation of Palm Oil Mill Effluent (POME) Digestion in a Continuous High Rate Up-Flow Anaerobic Sludge Blanket (UASB) Bioreactor

In this study, we operated a 10 litre upflow anaerobic sludge blanket (UASB) reactor continuosly at mesophilic temperature (38 °C). UASB reactor performance was evaluated based on the impact of the hydraulic retention time (HRT) ranged between 1 and 5 days and influent COD concentration in the range of 4540 mgL-1 and 20,820 mgL-1. The pH of the UASB was maintained in the range of 6.5 to 7.2 by adding buffering solution containing of 5 gL-1 of calcium oxide (CaO) derived from waste cockle shells. A simplified Monod’s model was employed to describe kinetics of anaerobic digestion of POME by using UASB reactor at organic loading rates (OLR) in the range between 1.17 g.CODL-1d-1 and 17.22 g.CODL-1d-1. A high COD degradation rate of 93.26 % was recorded at OLR of 3.92 g.COD L-1d-1 and HRT of 4 days. The UASB reactor generated the maximum biogas production at 34.95 L/d when operated at HRT 1 day and OLR 7.70 g.CODL-1. The proposed kinetic equations are applicable to describe anaerobic treatment of palm oil mill effluent with the UASB reactor. Biokinetic coefficients evaluated were, the growth yield (YG), 3.906 g VSS/g CODremoved.d-1; the specific biomass decay (b), 0.233 d-1; the specific biomass growth rate (μmax), 1.861 d-1; and the saturation constant (Ks), 3.459 g-CODL-1.

Effect of low temperature on the performance of UASB reactor for municipal wastewater treatment: recent advances and future perspectives

Upflow anaerobic sludge blanket (UASB) reactor is a widely used anaerobic treatment technology, which is essential in municipal sewage treatment, in tropical and subtropical areas. However, UASB reactors have been underutilized in low-temperate zones due to the poor performance of UASB reactors under psychrophilic conditions. This study has three primary purposes: to review the performance of UASB reactors with different parameters, to describe the limiting factors at low temperatures, and to prospect the future solutions. In the low-temperature environment, lower COD removal efficiency and production of methane in the UASB reactor have been observed in various studies. The key limiting factors are increased dissolved methane, decreased activity of methanogens and hydrolytic bacteria. This article proposed that five technologies could reduce the impact of low temperature on the treatment of municipal wastewater by the UASB reactor, which are denitrifying anaerobic methane oxidation (DAMO), direct interspecies electron transfer (DIET), bio-electrochemical systems (BES), pre-hydrolysis, and degassing membrane (DM). These technologies are promising to be developed into highly-efficient engineering strategies for treating municipal wastewater in the UASB reactor at low temperatures in the future.

Evaluation of UASB Reactor Performance During Start-Up Operation Using Glucose Bearing Synthetic Wastewater

This research article describes start-up performance of an UASB (Upflow Anaerobic Sludge Blanket) reactor in terms of chemical oxygen demand (COD) removal efficiency, biogas production, sludge loading rate (SLR), volatile fatty acids (VFA), pH, alkalinity, total solids (TS) and volatile suspended solids (VSS), fed with synthetic wastewater with increased concentrations of glucose. The reactor was loaded up to an OLR (Organic Loading Rate) of 15 kg COD m-3 d-1 and achieved a COD removal efficiency of 82 ±3%. The results showed that digested seed sludge was successfully acclimatized and transformed finally into granular sludge within a period of 120 days. An increase in the accumulation of VFA at high OLRs showed that methanogenesis could be the rate-limiting step in the reactor operation. The SLR and VSS/TS ratio were increased with an increase in OLR. During the initial stages, uniform distribution of VSS concentration and later on maximum VSS concentration were found at port number two at a height of 350 mm. The carbon balance depicts that the maximum percentage of influent COD converted to methane COD. An increase in specific methanogenic activity values with the age of sludge confirmed the transformation of the seed sludge in to a granular sludge.

The effect of temperature reduction on the performance and stability of UASB reactors treating synthetic sewage

The objective of this investigation is to determine the effect of temperature reduction on the performance and stability of laboratory-scale up-flow anaerobic sludge blanket (UASB) treating synthetic sewage. The work was carried out using four 4-litre continuously fed UASB reactors. The operation started at a constant hydraulic retention time of ~24 hours (up flow velocity ~0.02 m hour -1 ) and an influent COD concentration of ~2250 mg l -1 , with an organic loading rate of ~2.25 g COD l -1 day -1 . During the experiment, the operating temperature was reduced in a single step from 35 to 30 ⁰C, then stepped down to 25 ⁰C. COD removal efficiency fell slightly from ~96 % in all reactors to ~93%. Effluent TSS concentrations remained below 20 mg l -1 and TSS removal efficiency ranged between 93-98%. Gas production showed a slight disturbance following the initial drop in temperature to 30 ⁰C, but stabilised at around 0.74 l CH 4 l -1 , 0.30 l CH 4 g -1 COD added and 0.31 l CH 4 g -1 COD removed. The subsequent drop to 25 ⁰C produced a stronger disturbance, but both volumetric and specific methane production recovered to the previous values by about day 412. The average biogas methane content in all reactors was unchanged or marginally higher at 78-79%.

Long-term effects of multi-walled carbon nanotubes on the performance and microbial community structures of an anaerobic granular sludge system.

Multi-walled carbon nanotubes (MWCNTs) released into the sewage may cause negative and/or positive effects on the treatment system. The objective of this study was to explore over 110days' effect of MWCNTs on the performance of anaerobic granular sludge and microbial community structures in an upflow anaerobic sludge blanket (UASB) reactor. The results showed that MWCNTs had no significant effect on the removal of chemical oxidation demand (COD) and ammonia in UASB reactor, but the total phosphorus (TP) removal efficiency increased by 29.34%. The biogas production of the reactor did not change. The anaerobic granular sludge tended to excrete more EPS to resist the effects of MWCNTs during the long-term impact. Illumina MiSeq sequencing of 16S rRNA gene revealed that MWCNTs did not affect the microbial diversity, but altered the composition and structure of microbial community in the reactor. In this process, Saccharibacteria replaced Proteobacteria as the highest abundant bacterial phylum. MWCNTs promoted the differentiation of methanogen structure, resulting in increase of Methanomassiliicoccus, Methanoculleus, and the uncultured WCHA1-57. These results indicated that MWCNTs impacted the performance of UASB reactor and the structures of the microbial community in anaerobic granular sludge.

Nutrient mineralization and organic matter reduction performance of RAS-based sludge in sequential UASB-EGSB reactors

There is a recognized need for mineralizing aquaculture-derived sludge in aquaponics systems in order to reduce waste production. Many recent studies of aquacultural waste treatment have focused only the production of biogas as opposed to the potential for mineralization of nutrient-rich sludge. Upflow anaerobic sludge blanket (UASB) reactors provide one possible solution for breaking down sludge into bioavailable nutrients that can subsequently be delivered to plants. As such, this study examines the mineralization performance of sequential UASB reactors that are designed with an expanded granular sludge bed (EGSB) and compared to standard aerobic and anaerobic batch reactors. Results of our experiments demonstrate that only chemical oxygen demand reduction is significantly different. An unexpected drop in pH of one of the three reactor systems revealed that a pH below 6 was able to significantly increase the mineralization and mobilization of nutrients. Approximately 25% of phosphorus, potassium, and calcium could also be recovered from the sludge under lower pH conditions, as compared to the mineralization performance of standard UASB reactors running at a higher pH. However, the opposite effect was observed with respect to organic sludge reduction, where diminished performance was observed in the low-pH reactor. The current study implies that anaerobic reactors operating at low pH can potentially contribute towards improved nutrient recovery in multi-loop aquaponics systems and reduction of additive agents for pH control of the hydroponic subsystem.

Performance, granule conductivity and microbial community analysis of upflow anaerobic sludge blanket (UASB) reactors from mesophilic to thermophilic operation

Effects of temperature variations from mesophilic to thermophilic on the performance of UASB reactors with glucose and ethanol as substrate were investigated. The reactor with ethanol as substrate had better resistance to temperature variations with over 93% COD degradation rate and 75% methane content. The conductivity of granular sludge that degraded ethanol was also considerably higher. High-throughput sequencing indicated that the abundance of Methanobacterium decreased, while Methanosaeta increased with increasing temperature. Moreover, the abundance of Geobacter and Methanosaeta were higher in the reactor with ethanol as substrate than that with glucose, whereas a higher abundance of Klebsiella was observed in the glucose reactor. More importantly, significant correlations were observed between granular sludge conductivity and COD removal rate (R2 = 0.73), between the abundance of Geobacter and COD removal rate (R2 = 0.895). These results indicate that the growth of Geobacter and Methanosaeta which promote transfer electrons in the manner of DIET in anaerobic methanogenic systems might alleviate the effect of temperature variation and facilitate reaction rate.

Review of Upflow Anaerobic Sludge Blanket Reactor Technology: Effect of Different Parameters and Developments for Domestic Wastewater Treatment

The upflow anaerobic sludge blanket (UASB) reactor has been recognized as an important wastewater treatment technology among anaerobic treatment methods. The objective of this study was to perform literature review on the treatment of domestic sewage using the UASB reactor as the core component and identifying future areas of research. The merits of anaerobic and aerobic bioreactors are highlighted and other sewage treatment technologies are compared with UASB on the basis of performance, resource recovery potential, and cost. The comparison supports UASB as a suitable option on the basis of performance, green energy generation, minimal space requirement, and low capital, operation, and maintenance costs. The main process parameters such as temperature, hydraulic retention time (HRT), organic loading rate (OLR), pH, granulation, and mixing and their effects on the performance of UASB reactor and hydrogen production are presented for achieving optimal results. Feasible posttreatment steps are also identified for effective discharge and/or reuse of treated water.

Modeling of biogas production from cattle manure with co-digestion of different organic wastes using an artificial neural network

The present study utilizes an artificial neural network (ANN) as an estimation model of biogas production from laboratory-scale up-flow anaerobic sludge blanket (UASB) reactors treating cattle manure with co-digestion of different organic wastes. It can be estimated depending on working days, influent chemical oxygen demand, influent pH, influent alkalinity, influent ammonia, influent total phosphorus, hydraulic retention time, waste adding ratio, pretreatment and additive waste sorts. The suitable architecture of an ANN for use in biogas prediction consists of 10 input factors, tangent sigmoid transfer function (tansig) at the four hidden layer neurons and a linear transfer function (purelin) at the output layer neuron. The R 2 was found to equal 0.89, 0.79 and 0.75 in the training, validation and testing steps, respectively. ANN estimation modeling can effectively predict the biogas production performance of laboratory-scale UASB reactors. These results indicate that biogas production was optimized to occur in the 20–30% addition range with different organic wastes.

Continuous micro-current stimulation to upgrade methanolic wastewater biodegradation and biomethane recovery in an upflow anaerobic sludge blanket (UASB) reactor

The dispersion of granules in upflow anaerobic sludge blanket (UASB) reactor represents a critical technical issue in methanolic wastewater treatment. In this study, the potentials of coupling a microbial electrolysis cell (MEC) into an UASB reactor for improving methanolic wastewater biodegradation, long-term process stability and biomethane recovery were evaluated. The results indicated that coupling a MEC system was capable of improving the overall performance of UASB reactor for methanolic wastewater treatment. The combined system maintained the comparatively higher methane yield and COD removal efficiency over the single UASB process through the entire process, with the methane production at the steady-state conditions approaching 1504.7 ± 92.2 mL-CH4 L−1-reactor d−1, around 10.1% higher than the control UASB (i.e. 1366.4 ± 71.0 mL-CH4 L−1-reactor d−1). The further characterizations verified that the input of external power source could stimulate the metabolic activity of microbes and reinforced the EPS secretion. The produced EPS interacted with Fe2+/3+ liberated during anodic corrosion of iron electrode to create a gel-like three-dimensional [-Fe-EPS-]n matrix, which promoted cell-cell cohesion and maintained the structural integrity of granules. Further observations via SEM and FISH analysis demonstrated that the use of bioelectrochemical stimulation promoted the growth and proliferation of microorganisms, which diversified the degradation routes of methanol, convert the wasted CO2 into methane and accordingly increased the process stability and methane productivity.

Performance of Full-Scale UASB Reactors Treating Low or Medium Strength Municipal Wastewater

Upflow Anaerobic Sludge Blanket (UASB) reactors treating low or medium strength municipal wastewater were monitored under field conditions in India. The study aimed to evaluate the efficiency of the UASB process (in terms of organics, solids and nutrients removal) and to highlight the causes and remedies for odour nuisances. The UASB reactors represent a robust and efficient technology for sewage pre-treatment (COD removal: 51%; BOD: 56%; TSS: 54%), capable to generate renewable energy (biogas yield: 0.20–0.40 m3 kg−1 COD removed) under the conditions prevailing in India. The UASB performed significantly better when low strength wastewater (COD ~300 mg L−1) was treated, giving a final effluent COD of around 120 mg L−1, similar to aerobic treatment systems. In the case of medium strength municipal wastewater with high sulphate content (COD: 600 mg L−1; SO4: 175 mg L−1), a 10-fold increase of the effluent sulphide concentrations was recorded (from 3 to 34 mg L−1), compared to low strength sewage processing (from 1.5 to 7.0 mg L−1). As such, major odour nuisances (release of H2S) may originate from the anaerobic effluent itself, as well as from spontaneous biogas losses.

Anaerobic biodegradation of olive mill wastewater: batch and UASB reactor performance

Batch biodegradability tests were carried out to determine the digestibility of olive mill waste water (OMW), the COD removal and potential methane (CH4) yield. The tests were prepared with anaerobic sludge and different volumes of OMW (0 ml, 10 ml unfiltered, 20 ml unfiltered and 10 ml of filtered sample). The biodegradability of the mixtures based on the gas production rate was 43, 58, 53, and 59%, respectively. Anaerobic treatment of OMW was also investigated in an up flow anaerobic sludge blanket (UASB) reactor at organic loading rates (OLRs) between 1.6 and 8 kg COD m−3 d−1 at a hydraulic retention time of 15 h. The results showed stable COD removal efficiencies (∼85%) for OLRs up to 7.6 kg m−3 d−1. Gradual improvement in the biogas production rate was observed with higher OLRs. The highest CH4 yield was about 0.37 L CH4 g−1 of COD removed.

Anaerobic biodegradation of olive mill wastewater: batch and UASB reactor performance

Batch biodegradability tests were carried out to determine the digestibility of olive mill waste water (OMW), the COD removal and potential methane (CH4) yield. The tests were prepared with anaerobic sludge and different volumes of OMW (0 ml, 10 ml unfiltered, 20 ml unfiltered and 10 ml of filtered sample). The biodegradability of the mixtures based on the gas production rate was 43, 58, 53, and 59%, respectively. Anaerobic treatment of OMW was also investigated in an up flow anaerobic sludge blanket (UASB) reactor at organic loading rates (OLRs) between 1.6 and 8 kg COD m−3 d−1 at a hydraulic retention time of 15 h. The results showed stable COD removal efficiencies (∼85%) for OLRs up to 7.6 kg m−3 d−1. Gradual improvement in the biogas production rate was observed with higher OLRs. The highest CH4 yield was about 0.37 L CH4 g−1 of COD removed.

Impact of roxarsone on the UASB reactor performance and its degradation

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX) has been widely used for decades as an organoarsenic feed additive to control intestinal parasites and improve feed efficiency in animal production. However, most of the ROX is excreted into the manure, causing arsenic contamination in wastewater. The arsenic compounds are toxic to microorganisms, but the influence of continuous ROX loading on upflow anaerobic sludge blanket (UASB) reactor is still unknown. In this study, the impact of ROX and its degradation products on the performance of the UASB reactor and the degradation and speciation of ROX in the reactor were investigated. The UASB reactor (hydraulic retention time: 1.75 d) was operated using synthetic wastewater supplemented with ROX for a period of 260 days. With continuous ROX addition at 25.0 mg·L–1, severe inhibition to methanogenic activity occurred after 87 days operation accompanied with an accumulation of volatile fatty acids (VFAs) and a decline in pH. The decrease of added ROX concentration to 13.2 mg·L–1 did not mediate the inhibition. As(III), As (V), MMA(V), DMA(V), HAPA and an unknown arsenic compound were detected in the reactor, and a possible biotransformation pathway of ROX was proposed. Mass balance analysis of arsenic indicated that 60%–70% of the arsenic was discharged into the effluent, and 30%–40% was precipitated in the reactor. The results from this study suggest that we need to pay attention to the stability in the UASB reactors treating organoarsenic-contaminated manure and wastewater, and the effluent and sludge from the reactor to avoid diffusion of arsenic contamination.

Quality Assessment of Full-Scale Municipal Wastewater Treatment Plant Consisting UASB Reactors and Polishing Ponds During its Start-Up Phase in India

Amongst the technologies available, the up flow anaerobic sludge blanket (UASB) process has been one of the most widely applied methods for municipal waste water treatment especially in countries of warm climatic conditions like India. However, past about one decade has witnessed rapid decline in the UASB popularity and its implementation. There has been criticism from various sections on the performance of UASB reactors for not complying with the prescribed discharge standards. It is a general hypothesis that the UASB reactors are not meant for diluted waste water like municipal sewage when typically the BOD is less than 150 mg/l, COD 250 mg/l and sulphates are more than 150mg/l. An attempt has been made through this study to investigate the reasons on the basis of quality assessment and field observations on UASB reactors and it’s post-treatment of a newly commissioned (start-up) municipal (sewage) wastewater treatment plant commonly called ‘STP’ having capacity of 14 million litres per day (MLD). Study was aimed to know the gaps during the commissioning stage which could be related to poor removal efficiencies. This paper briefly discusses some issues related to operation and maintenance of the UASB plants with purpose for improvements.

Mathematical modeling of upflow anaerobic sludge blanket (UASB) reactors: Simultaneous accounting for hydrodynamics and bio-dynamics

Hydrodynamics and bio-dynamics are equally important in upflow anaerobic sludge blanket (UASB) reactors, but few studies have been conducted to consider both issues when developing a mathematical model. Therefore a novel ADM1-based dispersive model was developed in this study to provide a better description of UASB reactor performance by simultaneously taking into account the hydrodynamics and bio-dynamics of the reactor. Organic overloading shock experiments were carried out in a laboratory-scale UASB reactor to validate the developed model. The results of the simulation model were in good agreement with experimental data. Although considerable calculation time was required, the ADM1-based dispersive model showed obvious advantages in predicting reactor status, which may give an early warning of reactor abnormalities. The models developed here are expected to simulate UASB reactors more effectively and to provide useful information for their design and operation.

Significant performance enhancement of a UASB reactor by using acyl homoserine lactones to facilitate the long filaments of Methanosaeta harundinacea 6Ac.

Methanosaeta strains are frequently involved in the granule formation during methanogenic wastewater treatment. To investigate the impact of Methanosaeta on granulation and performance of upflow anaerobic sludge blanket (UASB) reactors, three 1-L working volume reactors noted as R1, R2, and R3 were operated fed with a synthetic wastewater containing sodium acetate and glucose. R1 was inoculated with 1-L activated sludge, while R2 and R3 were inoculated with 200-mL concentrated pre-grown Methanosaeta harundinacea 6Ac culture and 800mL of activated sludge. Additionally, R3 was daily dosed with 0.5mL/L of acetyl ether extract of 6Ac spent culture containing its quorum sensing signal carboxyl acyl homoserine lactone (AHL). Compared to R1, R2 and R3 had a higher and more constant chemical oxygen demand (COD) removal efficiency and alkaline pH (8.2) during the granulation phase, particularly, R3 maintained approximately 90% COD removal. Moreover, R3 formed the best granules, and microscopic images showed fluorescent Methanosaeta-like filaments dominating in the R3 granules, but rod cells dominating in the R2 granules. Analysis of 16S rRNA gene libraries showed increased diversity of methanogen species like Methanosarcina and Methanospirillum in R2 and R3, and increased bacteria diversity in R3 that included the syntrophic propionate degrader Syntrophobacter. Quantitative PCR determined that 6Ac made up more than 22% of the total prokaryotes in R3, but only 3.6% in R2. The carboxyl AHL was detected in R3. This work indicates that AHL-facilitated filaments of Methanosaeta contribute to the granulation and performance of UASB reactors, likely through immobilizing other functional microorganisms.

Performance of UASB reactor treating synthetic textile wastewater: effect of physicochemical pretreatment

AbstractThe study explores the influence of physicochemical pretreatment on the performance of upflow anaerobic sludge blanket (UASB) reactors treating synthetic textile wastewater. Physicochemical pretreatment in this study utilized a new composite coagulant magnesium chloride added with aluminum chlorohydrate which produced nearly complete color removal and a partial chemical oxygen demand (COD) removal (~55%) efficiency. Various parameters such as volatile fatty acids (VFA), bicarbonate alkalinity (B-Alk.), gas production, total aromatic amines (TAAs) generation, COD, and color removal efficiency were monitored in the UASB reactors operated at different operating conditions. For the UASB reactor treating pretreated textile wastewater, a maximum of 99% COD removal was obtained at an organic loading rates (OLRs) of 1.2 kg COD m−3 d−1 and hydraulic retention time (HRT) of 20 h. Whereas in case of without pretreatment, a maximum of both 92% COD and color removal efficiency were achieved at an OLR of 2.4 kg...