Expanded Granular Sludge Bed Reactor Research Articles

Impact of Supplemental Hydrogen on Biogas Enhancement and Substrate Removal Efficiency in a Two-Stage Expanded Granular Sludge Bed Reactor

In two-stage anaerobic expanded granular sludge bed (EGSB) reactors, up to one-third of the chemical oxygen demand (COD) content is naturally preacidified in a first stage preacidification (PA) tank and then fed to a second stage digester for conversion to methane. Hydrogen, an intermediate product of the first stage, could be theoretically captured escaping from the PA tank and sent to the digester to biologically convert the carbon dioxide to methane for biogas enhancement. Pilot-scale tests were conducted to assess the impact of introducing hydrogen gas on biogas quality enhancement and substrate removal efficiency in an EGSB digester fed with distillery wastewater at mesophilic temperature (35°C). The amount of hydrogen introduced, 0.15 or 0.30 L/(Lbiogas·day), was less than what could be theoretically captured escaping from the PA tank. Biogas quality was enhanced by ∼10% to 20% and the energy yield increased by ∼33–42% depending on the hydrogen injection rate. COD removal efficiency remained constant at about ∼98% with and without hydrogen. The Monod model maximum substrate removal rate constant slightly increased, while the half-saturation coefficient slightly decreased with the added hydrogen, both indicating that hydrogen injection did not negatively affect substrate removal efficiency or biomass culture stability.

Performance and microbial diversity of an expanded granular sludge bed reactor for high sulfate and nitrate waste brine treatment

The disposal of waste brines has become a major challenge that hinders the wide application of ion-exchange resins in the water industry in recent decades. In this study, high sulfate removal efficiency (80%–90%) was achieved at the influent sulfate concentration of 3600 mg/L and 3% NaCl after 145 days in an expanded granular sludge bed (EGSB) reactor. Furthermore, the feasibility of treating synthetic waste brine containing high levels of sulfate and nitrate was investigated in a single EGSB reactor during an operation period of 261 days. The highest nitrate and sulfate loading rate reached 6.38 and 5.78 kg/(m3·day) at SO2−4-S/NO–3-N mass ratio of 4/3, and the corresponding removal efficiency was 99.97% and 82.26% at 3% NaCl, respectively. Meanwhile, 454-pyrosequencing technology was used to analyze the bacterial diversity of the sludge on the 240th day for stable operation of phase X. Results showed that a total of 9194 sequences were obtained, which could be affiliated to 14 phyla, including Proteobacteria, Firmicutes, Chlorobi, Bacteroidetes, Synergistetes and so on. Proteobacteria (77.66%) was the dominant microbial population, followed by Firmicutes (12.23%) and Chlorobi (2.71%).

Influence of the organic loading rate on the performance and the granular sludge characteristics of an EGSB reactor used for treating traditional Chinese medicine wastewater

The effects of the organic loading rate (OLR) on the performance and the granular sludge characteristics of an expanded granular sludge bed (EGSB) reactor used for treating real traditional Chinese medicine (TCM) wastewater were investigated. Over 90% of the COD removal by the EGSB reactor was observed at the OLRs of 4 to 13 kg COD/(m(3) day). However, increasing the OLR to 20 kg COD/(m(3) day) by reducing the hydraulic retention time (HRT 6 h) reduced the COD removal efficiency to 78%. The volatile fatty acid (VFA) concentration was 512.22 mg/L, resulting in an accumulation of VFAs, and propionic acid was the main acidification product, accounting for 66.51% of the total VFAs. When the OLR increased from 10 to 20 kg COD/(m(3) day), the average size of the granule sludge decreased from 469 to 258 μm. There was an obvious reduction in the concentration of Ca(2+) and Mg(2+) in the granular sludge. The visible humic acid-like peak was identified in the three-dimensional excitation-emission matrix (EEM) fluorescence spectra of the soluble microbial products (SMPs). The fatty acid bond, amide II bond, amide III bond, and C-H bond bending were also observed in the Fourier transform infrared (FTIR) spectra of the SMPs. Methanobacterium formicicum, Methanococcus, and Bacteria populations exhibited significant shifts, and these changes were accompanied by an increase in VFA production. The results indicated that a short HRT and high OLR in the EGSB reactor caused the accumulation of polysaccharides, protein, and VFAs, thereby inhibiting the activity of methanogenic bacteria and causing granular sludge corruption.

Fast start-up of expanded granular sludge bed (EGSB) reactor using stored Anammox sludge

Stored Anammox sludge (SAS) was used in an expanded granular sludge bed (EGSB) reactor treating synthetic wastewater with the aim of evaluating its possible use as seed sludge. The SAS had been kept in a refrigerator (4 °C) without any feed. After 2 years, only 1-2% Anammox bacteria could survive in the SAS. However, it soon prevailed in the EGSB reactor after loading. Accordingly, the start-up of the EGSB reactor was successfully completed in 34 days. The biomass turned to round reddish granular sludge from irregular brown floc at the end of this study. The results indicate that SAS could serve well as seed sludge. The required time for start-up of the Anammox reactor using SAS was thus demonstrated to be shorter than that of uncultivated sludge under experimental conditions.

Concept and application of anaerobic suspended granular sludge bed (SGSB) reactor for wastewater treatment

Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed (EGSB) reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed (SGSB) reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upflow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency (about 90%) at high loading rates (average 40 kg-COD·m−3·d−1, maximum to 52 kg-COD·m−3·d−1) based on the SGSB theory, and its expansion degree is between 22% and 37%.

Anaerobic biodegradability of mixtures of pesticides in an expanded granular sludge bed reactor

The biodegradability and toxicity of three commercial pesticides containing 2-methyl-4-chlorophenoxyacetic acid (MCPA), imidacloprid and dimethoate were evaluated individually, and a complex mixture of these pesticides was treated in an expanded granular sludge bed (EGSB) reactor. MCPA was partially biodegraded, while imidacloprid and dimethoate remained almost unaltered during the individual biodegradability tests. Cyclohexanone was identified as the major solvent in the dimethoate-bearing insecticide, which was completely removed regardless of the presence of other pesticides. The analysis of the inhibition over the acetoclastic methanogenesis showed IC(50) (half maximal inhibitory concentration) values of 474 and 367 mg/L for imidacloprid and dimethoate, respectively. The effect on the methanogenesis was negligible in the case of MCPA and cyclohexanone. Pesticides caused a dramatic decrease of the EGSB reactor performance. After 30 d acclimation, the EGSB reactor achieved a stable chemical oxygen demand (COD) removal efficiency and methane production of around 85% and 0.9 g CH(4)-COD/g COD, respectively, for MCPA, imidacloprid, dimethoate and cyclohexanone feed concentrations of 57, 20, 25 and 27 mg/L, respectively. The presence of complex pesticide mixtures led to synergistic/antagonistic responses, reducing the MCPA biodegradation and improving the removal of the insecticides' active ingredients, which were completely removed in the EGSB reactor.

Accelerated startup of hydrogen production expanded granular sludge bed with l-Cysteine supplementation

l-Cysteine (l-Cys) was added to EGSB (expanded granular sludge bed) reactors during the startup process. A parallel EGSB without l-Cys addition was started as a control. The results showed that the startup process of the EGSB with l-Cys supplementation was well accelerated compared to the control reactor (without supplementation). Supplementation of l-Cys every four HRT (hydraulic retention time) had shortened the startup time. Hydrogen production rate was stimulated by 23.7% when adding 0.5 g/L l-Cys to the EGSB. The maximum hydrogen production yield was 1.93 mol/mol glucose, which was 20.6% higher than the control. The main liquid metabolites were ethanol and acetate. The substrate utilization rate was also increased. Scanning electron microscopy observations showed that obvious micro channels formed in the l-Cys supplemented reactors, which might well promote the mass transfer and energy exchange. The results showed that l-Cys supplementation was a feasible method to accelerate the continuous reactor startup.

Influence of volatile fatty acid concentration stability on anaerobic degradation of linear alkylbenzene sulfonate

Linear alkylbenzene sulfonate (LAS) is an anionic surfactant used in cleaning products, which is usually found in wastewaters. Despite the greater LAS removal rate related to a lower concentrations of volatile fatty acids (VFA), the influence of different ranges of VFA on LAS degradation is not known. LAS degradation was evaluated in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors at different ranges of VFA concentrations. The reactors were fed with a synthetic wastewater containing LAS (14 mg/L). A greater LAS removal rate (40–80%) was related to the lower and narrower range of acetic acid concentration (1–22 mg/L) in the EGSB reactor. In the UASB reactor, the acetic acid concentrations presented a wider range (2–45 mg/L), and some low LAS removal rates (around 20–25%) were observed even at low acetic acid concentrations (<10 mg/L). The high recirculation rate in the EGSB reactor improved substrate-biomass contact, which resulted in a narrower range of VFA and greater LAS removal rate.

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/(m(3) 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.

Kinetic Analysis of COD Removal from Actual Domestic Wastewater in an Expanded Granular Sludge Bed (EGSB) Reactor

Treatment of actual domestic wastewater at ambient temperature, even low temperature is considered to be difficult by traditional systems. The present study is related to treatment of actual domestic wastewater in an EGSB reactor. The study showed the effectiveness of biological treatment of actual domestic wastewater involving appropriate microorganism and granules in an EGSB reactor. At 26°C, the reactor was operated at 18.7kg COD.m−3.d−1 of average organic loading and 83% high COD removal efficiency, and even at the highest loading rate of 57.12kgCOD.m−3.d−1, the COD removal efficiency still could attain to 68%. Varied influent flow need to supply varied optimal and thus to ensure the optimal removal effect. Low temperature would cause pollutant removal rate decrease. However, enhancing could optimize the contact of sludge and wastewater and thus strengthen the performance effect. Modified Stover–Kincannon model was applied to data obtained from experimental studies in EGSB reactor. Treatment efficiencies of the reactor were investigated at different hydraulic retention times (0.5-1.3h) and different operation temperature (15°C, 26°C). The modified Stover–Kincannon model was best fitted to the EGSB reactor, and the substrate utilization rate( ), saturation constant value( ), and actual pollutant removal rate( ) were found to be , , and for 26°C, , , and for 15°C( before increasing ), and , , and for 15°C(after increasing ). Low temperature could cause decrease and thus cause distinct decreasing of COD removal efficiency. However, increasing could increase and accordingly increase COD removal efficiency.

The operation of two EGSB reactors under the application of different loads of oxytetracycline and florfenicol

This study evaluated the effect of the antibiotics oxytetracycline (OTC) and florfenicol (FLO) on the operation of two EGSB (expanded granular sludge bed) reactors. The experiment was conducted for 210 d in reactor R1 and 245 d in reactor R2. The reactors were inoculated with granular sludge from a upflow anaerobic sludge blanket (UASB) reactor on a local dairy farm. The sludge had an average pellet size of 2.35 mm, good sedimentability and a high percentage of organic material. The antibiotic tolerance and the inhibitory action on the bacterial population were different for each antibiotic studied. The results showed a more severe inhibitory effect on microorganisms that were in contact with increases in loads of FLO than those that were in contact with increasing loads of OTC, a condition reflected in the chemical oxygen demand (COD) removal efficiency.

Effect of Operation Conditions on Performance of Treating Actual Domestic Wastewater Bioreactor at Ambient Temperature

To determine the operation parameters of the expanded granular sludge bed (EGSB) reactor treating actual domestic wastewater at ambient temperature of 15-26°C, the effects of influent flow, HRT, recycle ratio,Vup and temperature on the performance of the EGSB reactor were investigated in this paper. The results indicated that when treating actual domestic wastewater, the EGSB reactor could support high influent flow and low HRT. For 9L.h-1, 11L.h-1, 15L.h-1, 24L.h-1 influent flow, with the optimal recycle ratios of 1.6-2.5, 1.2-1.6, 0.4-0.8, 0.0, the COD removal efficiencies could attain to 86-90%, 88-89%, 83%, 83%, respectively. For lower influent flow, higher Vup could slightly increase COD removal, but accordingly higher recycle ratio need to supply. Meanwhile, for higher influent flow, higher Vup will damage the granular characteristic and thus cause the decreasing of COD removal, and thus for the EGSB reactor treating actual domestic wastewater, 2.7-3.0m.h-1 optimal Vup should be employed. The EGSB reactor could work well at ambient temperature of 15°C-26°C. The optimal influent flow and Vup were 15-24L.h-1 and 3.0m.h-1. High average OLR of 18.6kgCOD.m-3.d-1 and high average COD removal efficiencies of above 81.4% could achieve, and only very low recycle ratio of 0.0 to 0.4 need employ.

Effects of ORP, recycling rate, and HRT on simultaneous sulfate reduction and sulfur production in expanded granular sludge bed (EGSB) reactors under micro-aerobic conditions for treating molasses distillery wastewater

An expanded granular sludge bed (EGSB) reactor was adopted to incubate the sludge biogranule that could simultaneously achieve sulfate reduction and sulfide reoxidization to elemental sulfur for treating molasses distillery wastewater. The EGSB reactor was operated for 175 days at 35 °C with a pH value of 7.0, chemical oxygen demand (COD) loading rate of 4.8 kg COD/(m³ d), and sulfate loading rate of 0.384 kg SO(4)(2-)/(m³ d). The optimal operation parameters, including the oxidation reduction potential (ORP), recycling rate, and hydraulic retention time (HRT), were established to obtain stable and acceptable removal efficiencies of COD, sulfate, and higher elemental sulfur production. With an ORP of -440 mV, a recycling rate of 300%, and HRT of 15 h, the COD and sulfate removal efficiencies were 73.4 and 61.3%, respectively. The elemental sulfur production ratio reached 30.1% when the elemental sulfur concentration in the effluent was 48.1 mg/L. The performance results were also confirmed by the mass balance calculation of sulfate, sulfide, and elemental sulfur over the EGSB reactor.

Effect of Low Concentration Cyanide on Startup of Expanded Granular Sludge Bed for the Treatment of Tapioca Starch Wastewater

In this investigation, An Expanded Granular Sludge Bed (EGSB) was used to treat tapioca starch wastewater containing low concentration cyanide and the influence of cyanide concentration on the startup of EGSB reactor was conducted. On the condition of 13.4h of HRT, the chemical oxygen demand (COD) and cyanide concentration varied, The EGSB performance was assessed in terms of COD, pH, alkalinity, volatile fatty acids (VFA) and methane variation during the process. The results showed that cyanide was harmful to the anaerobic bacteria of the granular sludge in EGSB reactor for the treatment of tapioca starch waster, as the cyanide concentration was at 15mg/L, COD removal efficiency for cyanide free wastewater nearly 90%, however the efficient dropped to 80% with increasing cyanide concentration up to15mg/L; the methane production was nearly 200mg/L with cyanide concentration and dropped to a value of 2mg/L for 15 mg/L cyanide; and methanogenic activity decreased; while the influent VFA was increased, at an cyanide concentration of 0 and 5mg/L, the concentration of VFA was maintained below 100.00mg/L, but it was higher than 600mg/L in most of the cases with influent cyanide concentration of 15mg/L; SEM observation of the granules showed the predominance of Methanosaeta. sp. and the obvious damage of the bacteria located on the surface or in the inner part of some granules, leading to a deterioration of granular sludge settling velocity, and even some granules washed out.

Quick Cultivation of Micro-Aerobic Granular Sludge for Simultaneous Nitrogen Removal

In order to accelerate the cultivation of micro-aerobic granular sludge for domestic sewage treatment, an expanded granular sludge bed (EGSB) reactor seeded with excess sludge was employed. It was found that micro-aerobic granules can form and grew compact within one month, and remained stable during the later operation, the mature cultivation had average particle size of 0.81mm, and 64% of the granules had settling velocity above 35m•h-1. Moreover, excellent COD and nitrogen removal were obtained. For hydraulic retention time (HRT) of 5h, as the recirculation ratio and oxygenation rate were set at 6.5 and 0.25g•L-1d-1respectively, COD removal ranged in 80%-91%, leaving effluent COD below 50mg•L-1. The removal efficiency of ammonium and total nitrogen (TN) were 72%-89% and 76%-87%, respectively with effluent concentration down to 3-12mg•L-1and 5-14mg•L-1. Results showed that the efficiency of simultaneous nitrogen removal was much influenced by effluent recirculation and oxygenation rate in micro-aerobic EGSB reactor.

The effect of operational conditions on the hydrodynamic characteristics of the sludge bed in UASB reactors

This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Sludge Blanket (UASB) reactors based on its settleability and expansion characteristics. The methodologies used for the evaluation of the settleability of aerobic activated sludge, and for the expansibility of a sludge bed of Expanded Granular Sludge Bed reactors and Fluidised Bed Reactors were adapted and applied to the particular characteristics of the sludge of UASB reactors. An easy-to-build experimental set-up was developed to assess the parameters necessary for the equations of settleability and of expansibility. The results obtained from the sludges of seven differently operated reactors show that, for the treatment of low strength wastewater, settleability increased and expansibility decreased at decreased hydraulic retention time, from 6 to 1 h, and/or increased influent concentrations, from 136 to approximately 800 mg chemical oxygen demand/L. The results also show that it is useless to design an UASB reactor with a longer hydraulic retention time to cope with hydraulic shock loads, as a more expansible sludge will develop at such condition.

Anaerobic biodegradation of 2,4,6-trichlorophenol in expanded granular sludge bed and fluidized bed biofilm reactors bioaugmented with Desulfitobacterium spp.

The biodegradation of 2,4,6-trichlorophenol (246TCP) was studied using expanded granular sludge bed (EGSB) reactors and a fluidized bed biofilm reactor (FBBR) filled with activated carbon. One of the EGSB reactor and the FBBR were bioaugmented with Desulfitobacterium strains. 246TCP loading rate was gradually incremented from 10 to 250 mg L(-1) day(-1). The main pathway of dechlorination was in ortho-position, generating 4-chlorophenol and 2,4-dichlorophenol. The maintenance of both COD degradation efficiency (higher than 80%) and methanogenic efficiency (between 0.3 and 0.6 g CH4-COD g(-1) COD consumed) in EGSB reactor implies a great stability of the process. Through isotherm studies in FBBR, it could be deduced that around 52% of 246TCP was completely dechlorinated, whereas the adsorption involved around 16%. By means of FISH studies it was proved that the methanogenic Archaea community was maintained in the bioaugmented EGSB reactor, whereas in the FBBR this community was gradually developed until reaching stability. Desulfitobacterium community was also maintained in the reactors, although D. chlororespirans proportion rise in the FBBR at the higher 246TCP loading rates, implying that this species can withstand the 246TCP toxicity better than D. hafniense.

Evaluation of process of the Expanded Granular Sludge Bed (EGSB) reactor for performance treatment of municipal sewage

Evaluation of process of the Expanded Granular Sludge Bed (EGSB) reactor for performance treatment of municipal sewage

Investigation of a sewage-integrated technology combining an expanded granular sludge bed (EGSB) and an electrochemical reactor in a pilot-scale plant

A sewage-integrated treatment system (SITS) for the treatment of municipal wastewater, consisting of an expanded granular sludge bed (EGSB) reactor to remove soluble organic matter and an electrochemical (EC) reactor to oxidize the NH 3–N, was evaluated. The performance of the EGSB reactor was monitored for 12 months in a pilot-scale plant. Iron shavings were added to the EGSB reactor on the sixtieth day to improve the removal efficiency of the chemical oxygen demand (COD), suspended solids (SS) and total phosphorus (TP). After the iron shavings were added, the effluent COD, SS and TP decreased from 104 to 46 mg L −1, 21 to 8.6 mg L −1 and 3.62 to 1.36 mg L −1, respectively. Moreover, in the EC reactor, which was equipped with IrO 2/Ti anodes, the NH 3–N and total nitrogen (TN) concentrations decreased from 25 to 12 mg L −1 and 29 to 15 mg L −1, respectively. The NH 3–N was directly oxidized to N 2, resulting in no secondary pollution. The results demonstrated the possibility of removing carbon and nutrients in a SITS with high efficiency. The system runs efficiently and with a flexible operation, making it suitable for low-strength wastewater. The results and parameters presented here can provide references for the practical project.

Treatability study of using low frequency ultrasonic pretreatment to augment continuous biohydrogen production

Low frequency ultrasonic treatment was investigated to enhance hydrogen production by bacteria under both batch and continuous operation. Optimal ultrasonic time and intensity as examined in batch experiments were found to be 10 s and 100 W, respectively. Hydrogen production was increased by 20% while ultrasonic treatment could effectively shorten batch test reaction times. Using these optimized conditions, continuous experiments were conducted in two parallel expanded granular sludge bed (EGSB) reactors. The ultrasonic treated EGSB reactor obtained a specific hydrogen production rate of 4.38 L/g VSS·d, which was 32% higher than that in the control reactor. Ethanol-type fermentation was achieved at a faster rate and with a 72.7% shorter startup time using ultrasonic treatment. Microbial activity under ultrasonic treatment was shown to resist lower pH and to maintain satisfactory hydrogen production.