Performance Of UASB Reactor Research Articles

Start-up performance of UASB reactors in low pH for acid mine drainage treatment

Start-up performance of UASB reactors in low pH for acid mine drainage treatment

Performance of UASB reactor treating waste activated sludge: Effect of electro-chemical disintegration on the anaerobic microbial population structure and abundance

The electro-Fenton (EF) disintegration using iron electrodes was performed for the pretreatment of waste activated sludge (WAS). The effect of this electro-chemical pretreatment on anaerobic digestion (AD) performance and microbial population structure was studied. An improvement of biodegradability and bioaccessibility of organic matter was demonstrated. AD of pretreated WAS in an up-flow anaerobic sludge blanket reactor (UASB) resulted to an increase of biogas production by 60 % compared to control reactor without disintegration. PCR-DGGE and real-time qPCR analyses showed that the high abundance of bacteria and the coexistence of Coprothermobacter in the UASB digestate fed with disintegrated sample established a stable bacterial association which is in line with the AD performance. Besides, the increased number of methanogens along the process allowed the improvement of methane production in comparison to control reactor.

Removal mechanisms of β-blockers by anaerobic digestion in a UASB reactor with carbon feeding

Efficient removal of medical wastewater and pharmaceutical production wastewater containing Beta-blockers is currently the focus and difficulty of research. In this study, the UASB reactor was used to achieve efficient removal of Beta-blockers. The removal rate of atenolol, metoprolol and propranolol is about 80%, 60% and 60%, respectively. The relevant functional microorganisms were Thermotogae, Anaerolineae and Bacteroidetes. Beta-blockers interfered with the metabolism of bacteria and methanogens, resulting in reduction of methane production and accumulation of acetic acid, which in turn affected the performance of UASB reactor. Metoprolol, atenolol and propranolol are mainly removed by anaerobic co-metabolism with starch, of which oxidative degradation is the main route. This study provides a new idea for the complete and efficient biodegradation of Beta-blockers wastewater.

Comparative assessment of modeling and experimental data of ammonia removal from pre-digested chicken manure

The aim of this study was to interpret the development of Anammox activity by a mathematical model in an UASB reactor -originally inoculated with methanogenic granules- at which Anammox progress has been also experimentally observed while treating chicken manure digestate. Since ammonium is derived from anaerobic degradation of nitrogenous compounds in chicken manure similar to any other nitrogen-rich organic wastes; the reactor was operated intentionally at favorable conditions [i.e.; with external nitrite source for NH4 +:NO2 -≅1.0] in order to make Anammox process to prevail as operation continued. Results indicated significant ammonia removals (60% on average) although influent concentration was gradually increased up to 200 mg L-1. A modeling exercise has been undertaken to investigate the performance of the laboratory scale UASB reactor. In this scope, the experimental results were modeled by using Mantis2 model within GPS-X 6.5 simulation software that included several built in libraries. Accordingly, effluent chemical oxygen demand (COD) and total ammonia nitrogen (TAN) concentrations could be predicted with reasonably good accuracy demonstrating successful calibration. The regression coefficient (R2 ) and mean relative absolute error (MRAE) parameters were found as 0.66 and 16% and 0.70 and 19%, respectively.

Biogas production from the liquid waste of distilled gin production: Optimization of UASB reactor performance with increasing organic loading rate for co-digestion with swine wastewater

This study is the first test that proves high rate anaerobic digestion as an efficient technological process for the treatment of gin spent wash. The gin spent wash was co-digested in UASB reactors with swine wastewater, which provided nutrients and alkalinity. The process was optimized by increasing the proportion of gin spent wash in the feed, and thus the organic loading rate (OLR) up to reactor failure. Stable high- efficiency operation was reached at an OLR as high as 28.5 kg COD m−3 d−1, yielding 8.4 m3 CH4 m−3 d−1 and attaining a COD removal of 97.0%. At an organic loading rate of 32.0 kg COD m−3 d−1, the process became unstable and the reactor underwent over-acidification that drastically lowered the pH and suppressed methanogenesis. The failure of the reactor was caused by a combination of an organic overloading and alkalinity deficit that uncoupled acidogenesis and methanogenesis.

Modification of UASB reactor by using CFD simulations for enhanced treatment of municipal sewage.

Up-flow anaerobic sludge blanket (UASB) has been in use since last few decades for the treatment of organic wastewaters. However, the performance of UASB reactor is quite low for treatment of low strength wastewaters (LSWs) due to less biogas production leading to poor mixing. In the present research work, a modification was done in the design of UASB to improve mixing of reactor liquid which is important to enhance the reactor performance. The modified UASB (MUASB) reactor was designed by providing a slanted baffle along the height of the reactor having an angle of 5.7° with the vertical wall. A two-dimensional computational fluid dynamics (CFD) simulation of three phase gas-liquid-solid flow in MUASB reactor was performed and compared with conventional UASB reactor. The CFD study indicated better mixing in terms of vorticity magnitude in MUASB reactor as compared to conventional UASB, which was reflected in the reactor performance. The performance of MUASB was compared with conventional UASB reactor for the onsite treatment of domestic sewage as LSW. Around 16% higher total chemical oxygen demand removal efficiency was observed in MUASB reactor as compared to conventional UASB during this study. Therefore, this MUASB model demonstrates a qualitative relationship between mixing and performance during the treatment of LSW. From the study, it seems that MUASB holds promise for field applications.

Influence of phase separator design on the performance of UASB reactors treating municipal wastewater

The objective of anaerobic sewage treatment is to maximize the fraction of influent organic material that is transformed into methane, thus minimizing the COD fractions that are discharged with the effluent or in the excess sludge production. Experimental data in this paper show that in the case of application of a UASB reactor for sewage treatment, the phase separator design has an important influence on digestion efficiency. An efficient phase separator leads to retention of a larger sludge mass, which means that the mean solids retention time is increased. The data show that the mean solids retention time or sludge age is the fundamental operational parameter that determines the efficiency of the anaerobic treatment. A simple way to improve the phase separator performance is to apply parallel plates in the settling section of the UASB reactor, above the conventional phase separator design of triangular prisms with an open base.

Influence of phase separator design on the performance of UASB reactors treating municipal wastewater

Influence of phase separator design on the performance of UASB reactors treating municipal wastewater

English

The use of anaerobic process for domestic wastewater treatment would achieve lower carbon footprint as it eliminates aeration and generate methane. Among several anaerobic treatment processes, high rate anaerobic digesters receive great attention due to its high loading capacity and chemical oxygen demand removal rate. Up-flow anaerobic sludge blanket reactor (UASB) is getting wide acceptance among several anaerobic processes. However, its application is still limited to industrial wastewater treatment. There are some unresolved problems to be accepted it in developing countries with lower temperature conditions for domestic wastewater treatment. Several studies have been carried out for the performance of UASB reactor but there is still lack of updated information especially on the issue of low temperature domestic wastewater treatment. Considering the gravity of the issue, an attempt have been made to compile updated information so as to help engineers, researchers and practitioners in the selection of reactors and future prospects of research. Key words: Wastewater, anaerobic, up-flow anaerobic sludge blanket reactor (UASB), carbon footprint.

Methanol induces low temperature resilient methanogens and improves methane generation from domestic wastewater at low to moderate temperatures

Low temperature (<20°C) limits bio-methanation of sewage. Literature shows that hydrogenotrophic methanogens can adapt themselves to low temperature and methanol is a preferred substrate by methanogens in cold habitats. The study hypothesizes that methanol can induce the growth of low-temperature resilient, methanol utilizing, hydrogenotrophs in UASB reactor. The hypothesis was tested in field conditions to evaluate the impact of seasonal temperature variations on methane yield in the presence and absence of methanol. Results show that 0.04% (v/v) methanol increased methane up to 15 times and its effect was more pronounced at lower temperatures. The qPCR analysis showed the presence of Methanobacteriales along with Methanosetaceae in large numbers. This indicates methanol induced the growth of both the hydrogenotrophic and acetoclastic groups through direct and indirect routes, respectively. This study thus demonstrated that methanol can impart resistance in methanogenic biomass to low temperature and can improve performance of UASB reactor.

Assessment of a UASB reactor with high ammonia concentrations: Effect of zeolite addition on process performance

The UASB process for wastewater treatment has been extensively studied, but the use of zeolite to improve UASB reactor performance has rarely been explored. In this study, a UASB reactor modified with natural zeolite operating at high nitrogen concentrations (0.5, 0.7 and 1g/L) was evaluated. Two laboratory bioreactors, one with zeolite and one without, were operated at ambient temperatures ranging between 18°C and 21°C. The experimental phase had a start-up period of 21 days. In the reactor with zeolite, the pH was found to be between 7.9 and 9.1, with a COD removal efficiency of about 60% after 80 days of operation at ammonia concentrations of between 0.229 and 0.429g/L in the effluent. In the reactor without zeolite, the pH was between 8.3 and 9.3, and the COD removal efficiency was about 40% at ammonia concentrations between 0.244 and 0.535g/L in the effluent. The addition of zeolite also decreased the volatile suspended solids (VSS) concentration in the effluent, generating a biomass with larger granules and higher settling rates as compared to a UASB reactor without zeolite. Taking the lower ammonia concentration, the higher COD removal and the improved granulation into account, it can be concluded that natural zeolite positively influenced the behavior and performance of the UASB reactor operating with high nitrogen concentrations.

Start-up and performance of UASB reactors using zeolite for improvement of nitrate removal process

A first study on the use of Chilean natural zeolite of different particle sizes (0.5, 1 and 2mm in diameter) in laboratory-scale batch denitrificant reactors was carried out with the aim of assessing the microbial communities adhered to this material. Molecular techniques such as fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) fingerprints revealed a high microbial diversity with a strong presence of Gammaproteobacteria (70% of the total microorganisms) in reactors with zeolite 0.5mm in diameter. Archaea were only detected in the reactors with zeolite 1mm in diameter. In addition, the acclimatization and start-up of two UASB reactors (one without zeolite and the other with added zeolite 1mm in diameter) were conducted following three consecutive and progressive stages using upward velocities from 0.10 to 0.44m/h in order to establish an experimental protocol suitable for the start-up of this type of reactors. Total (100%) nitrate reduction was achieved in the UASB reactors with and without zeolite on the 7th and 11th days, respectively, of the second stage of the start-up period, showing the suitability of the use of this material in this type of reactors. Finally, a third study carried out with both UASB reactors operating in continuous mode at a high organic loading rate (44kgCOD/m3d) and a very low HRT (2.5h) revealed that the reactor with zeolite achieved a nitrate removal efficiency of 92.4% at a nitrogen load of 6.42kgNO3−/(m3d). This last study also demonstrated the robustness of the UASB reactor with zeolite under nitrate load variations.

Enhanced Biogas Production from Canned Seafood Wastewater by Co-digestion with Glycerol Waste and Wolffia Arrhiza

Anaerobic co-digestion of canned seafood wastewater (CSW) with glycerol waste (GW) and wolffia arrhiza (WA) for methane production was investigated. Methane yields from anaerobic co-digestion of CSW with 1%GW, CSW with 1%GW and 5%WA, CSW with 1%GW and 10%WA and CSW with 1%GW and 15%WA were 577, 789, 545 and 474 mL CH4/g VS-added, respectively. Methane production from CSW with 1%GW and 5%WA increased approximately 4-fold when compared with CSW alone (278 mLCH4/g VS-added). Co-digestion of CSW with 1% GW and 5% WA was the best condition and gave the maximum methane production of 8.8 m3 CH4/m3 mixed wastewater and 96.8% biodegradability. The maximum methane production rate and yield were 3.71 L CH4/L-reactor.day and 858 mL CH4/g VS-added (352 mLCH4/g COD-removed) at OLR of 4 g COD/L. day in UASB reactor. The methane composition in biogas was 62.3%. The Monod, Modified Stover–Kincannon and Grau second-order models were used to explain the performance of UASB reactor. The results showed that the kinetic coefficient of the Modified Stover–Kincannon model could explain the performance of UASB reactor in term of COD removal efficiency and microbial growth by having the regression coefficient (R2) as 0.987.

Mathematical modeling of high-rate Anammox UASB reactor based on granular packing patterns

A novel mathematical model was developed to estimate the volumetric nitrogen conversion rates of a high-rate Anammox UASB reactor based on the packing patterns of granular sludge. A series of relationships among granular packing density, sludge concentration, hydraulic retention time and volumetric conversion rate were constructed to correlate Anammox reactor performance with granular packing patterns. It was suggested that the Anammox granules packed as the equivalent simple cubic pattern in high-rate UASB reactor with packing density of 50–55%, which not only accommodated a high concentration of sludge inside the reactor, but also provided large pore volume, thus prolonging the actual substrate conversion time. Results also indicated that it was necessary to improve Anammox reactor performance by enhancing substrate loading when sludge concentration was higher than 37.8gVSS/L. The established model was carefully calibrated and verified, and it well simulated the performance of granule-based high-rate Anammox UASB reactor.

Comparative Study on Startup Performance of UAHR and UASB Reactors in Anaerobic Treatment of Distillery Spentwash

In this paper, startup performance of Upflow Anaerobic Hybrid Reactor and Upflow Anaerobic Sludge Blanket reactors in anaerobic treatment of distillery spentwash has been studied under identical conditions of operation. Various effluent characteristics like pH, Electrical Conductivity, Chemical Oxygen Demand, Biochemical Oxygen Demand and Total Solids and other process parameters like biogas production and methane per cent in biogas were studied until the attainment of steady state. The startup of the reactors has been completed and steady state condition attained on 25th day of reactor operation in UAHR and 34th day in UASB reactor. The treated effluent characteristics of both reactors were fairly steady after attaining the steady state condition. The pH of treated effluent during steady state condition was almost neutral for both reactors even though the influent had an acidic pH. The maximum COD, BOD and TS removal efficiencies were as high as 79.60%, 87.39% and 69.96% in UAHR as compared with UASB of 72.98%, 81.34% and 66.23%, respectively during the steady state period. The maximum volumetric gas production of 149 L m-3 produced more in UAHR than in UASB reactor during steady state condition. The population of total anaerobic bacteria and methanogenic bacteria also more as that of the other parameters in UAHR than in UASB reactor and it were 55.2 x 103 ml-1 and 40.0 x 102 ml-1 respectively in UAHR. It is found that from an overall assessment the UAHR has proved superior in its performance compared to the UASB reactor during the startup process.

Process Performance and Sludge Behaviors of Multi-staged UASB reactor for Treatment of Palm Oil Mill Effluent (POME)

Process Performance and Sludge Behaviors of Multi-staged UASB reactor for Treatment of Palm Oil Mill Effluent (POME)

The Effect of Shock Loading to the Performance of Thermophilic UASB reactor in terms of Deterioration and Recovery

The Effect of Shock Loading to the Performance of Thermophilic UASB reactor in terms of Deterioration and Recovery

Effect of influent pH and alkalinity on the removal of chlorophenols in sequential anaerobic–aerobic reactors

This study was carried out to determine the effect of influent pH and alkalinity on the performance of sequential UASB and RBC reactors for the removal of 2-CP and 2,4-DCP from two different simulated wastewaters. The performance of methanogens at low (<6.0) to high (>8.0) pH values and at sufficiently high alkalinity (1500–3500 mg/l as CaCO 3) is described in this paper. Sequential reactors were capable of handling wastewaters with influent pH, 5.5–8.5. However, with influent pH 7.0 ± 0.1 UASB reactor showed best performance for 2-CP (99%) and 2,4-DCP (88%) removals. Increase in alkalinity/COD ratio in the influent (>1.1) caused gradual decrease in the chlorophenol removal in UASB reactors. The UASB reactors could not tolerate wastewater with higher alkalinity/COD ratio (2.6) and showed significant deterioration of its performance in terms of chlorophenols removal achieving only 74.7% 2-CP and 60% 2,4-DCP removals, respectively.

Performance of UASB and DAEB reactors in the anaerobic digestion of synthetic wastewater containing sodium oleate and sodium stereate

This study aimed at evaluating the performance of five laboratory-scale reactors, three UASB and two downflow anaerobic expanded bed (DAEB), fed with saccharose and long chain fatty acids (LCFA) for 410 days. Reactors operated at a temperature of 35 degrees C. The organic load rates were changed between 3.45 and 6.38 kg COD.m3.d(-1). During period I the substrate was saccharose and in periods II, III and IV it was saccharose plus sodium oleate, stereate and a mixture of sodium oleate and stereate. The UASB and DAEB reactors showed a similar performance. In UASB reactors specific methanogenic activity decreased in the periods II, III and IV. COD removal, biogas production and CH4 concentration in biogas decreased in all reactors at the end of the study. A washout occurred in UASB 2 and 3 when sodium stereate exceeded 500 mg.L(-1). In DAEB reactors the main problem was adsorption of LCFA particles onto the solid support.

A full-scale UASB reactor for treatment of pig and cattle slaughterhouse wastewater with a high oil and grease content

This paper discusses the performance of an 800m³ full-scale UASB reactor in treating meat-packing plant and slaughterhouse effluents containing high concentrations of oil and grease (O&G) (413-645 mg/L), resulting in a COD/O&G ratio of 26-32%. Those macromolecules were considered responsible for the unbalance of the system resulting in a total washout of the biomass. The removal of O&G from the influent using a physicochemical system (coagulation-flocculation) improved the physical characteristics of the anaerobic sludge, controlling the biomass washout. Reactor performance was significantly improved when the COD/O&G ratio influent was maintained in the 10%. The COD and O&G removal rates obtained after implantation of the physicochemical system were 70-92% and 27-58%, respectively. The specific methanogenic activity (SMA) of the biomass shows towards a tendency stabilisation and adaptation to the substrate influent. Pretreatment of the influent allowed the maximum organic load to be increased (1.46 to 2.43 Kg COD/m³.d) and improved the quality of the effluent.