The influence of anaerobic pretreatment on the nitrogen removal from biosynthetic pharmaceutical wastewaters

The C:N ratio of the pharmaceutical wastewaters is usually suitable for a combination of the anaerobic pretreatment with the high COD removal and aerobic posttreatment with the efficient biological N removal. This kind of anaerobic-aerobic process was tested in semipilot scale by using a UASB reactor and an activated sludge system with a predenitrification (total volume 100 1). It was found that at a total HRT of 2.3 days an average of 97.5% of COD and 73.5% of total N was removed. The UASB reactor was operated at 30°C with a volumetric loading rate of 8.7 kg.m^-3.d^-1, the efficiency of COD removal was 92.2%. The processes, which take part in the biological removal of nitrogen, especially the nitrification, were running with lower rates than usually observed in aerobic treatment systems.Abbreviations AAO anaerobic anoxic oxic configuration - AOO anaerobic oxic oxic configuration - B _V volumetric organic loading rate (kg COD.m^-3. d^-1) - dB _x specific COD removal rate (mg COD. g^-1 VSS. d^-1) - DNR denitrification rate (mg N–NO₃. g^-1 VSS. h^-1) - E_COD efficiency of COD removal (%) - HRT hydraulic retention time (d) - NR nitrification rate (mg N–NO₃. g^-1 VSS. h^-1) - R recirculation ratio (%) - SBP specific biogas production (m³.kg^-1 removed COD) - SRT solids retention time; sludge age (d) - SS suspended solids (g.1^-1) - UASB upflow anaerobic sludge blanket reactor - VSS volatile suspended solids (g.1^-1)     

Thermophilic anaerobic treatment of sulphur rich forest industry wastewater

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

Anaerobic degradation of benzaldehyde in methanogenic granular sludge: the influence of additional substrates

Summary The degradation of benzaldehyde in methanogenic granular sludge was investigated in batch and in upflow anaerobic sludge blanket (UASB) reactors. The effect due to the presence of co-substrates, such as H₂, sodium butyrate and sucrose, was studied using formaldehyde as a reference compound. The additional substrates enhanced the activity of benzaldehyde- and formaldehyde-degrading microorganisms (ACT_bdm and ACT_fdm, respectiveky) and increased the transient production of benzyl alcohol and methanol. As a consequence, the concentrations of benzaldehyde and formaldehyde that caused 50% inhibition of the methanogenic activity (50% IC_m) on sucrose were 3133 and 254 mg chemical oxygen demand (COD)/l respectively, three times higher than the literature data values on acetate. Experiments performed in UASB reactors on benzaldehyde showed that the replacement of volatile fatty acids with sucrose as co-substrate improved the treatment capacity of the system from 0.73 to 4.36 kg COD benzaldehyde·m^–13·day^–1. Correspondence to: O. Todini     

Long-term adaptation of methanol-fed thermophilic (55 °C) sulfate-reducing reactors to NaCl

A laboratory-scale upflow anaerobic sludge bed (UASB) reactor was operated during 273 days at increasing NaCl concentrations (0.5–12.5 g NaCl l^–1) to assess whether the stepwise addition of the salt NaCl results in the acclimation of that sludge. The 6.5-l thermophilic (55 °C), sulfidogenic [a chemical oxygen demand (COD) to SO₄^2– ratio of 0.5] UASB reactor operated at an organic loading rate of 5 g COD l^–1 day^–1, a hydraulic retention time of 10 h and was fed with methanol as the sole electron donor. The results show that the adaptation of the thermophilic, sulfidogenic methanol-degrading biomass to a high osmolarity environment is unlikely to occur. Sulfide was the main mineralization product from methanol degradation, regardless of the NaCl concentration added to the influent. However, sulfide production in the reactor steadily decreased after the addition of 7.5 g NaCl l^–1, whereas acetate production was stimulated at that influent NaCl concentration. Batch tests performed with sludge harvested from the UASB reactor when operating at different influent salinities confirmed that acetate is the main metabolic product at NaCl concentrations higher than 12.5 g l^–1. The apparent order of NaCl toxicity towards the different trophic groups was found to be: sulfate-reducing bacteria > methane-producing archaea > acetogenic bacteria.     

Effects of alternative carbon sources on biological transformation of nitrophenols

The removal of nitrophenols under denitrifying conditions was studied in bench-scale upflow anaerobic sludge blanket (UASB) reactors (R1, R2, R3 and R4) using three different carbon sources. Initially acetate was used as carbon source (substrate) in all the four reactors followed by glucose and methanol. Reactor R1 was kept as control and R2, R3, R4 were fed with 30 mg/l concentration of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP), respectively. Throughout the study the hydraulic retention time (HRT) and COD/NO₃ ^-–N ratio were kept as 24 h and 10, respectively. 2-Aminophenol (2-AP), 4-aminophenol (4-AP) and 2-amino,4-nitrophenol (2-A,4-NP) were found as the major intermediate metabolites of 2-NP, 4-NP and 2,4-DNP degradation, respectively. Methanol was found to be a better carbon source for 4-NP and 2,4-DNP degradation as compared to acetate and glucose, while 2-NP degradation was not influenced much by the change of substrate. Nitrate nitrogen removal was always more than 99%. COD removal efficiency of the nitrophenol fed reactors varied from 85.7% to 97.7%. The oxidation-reduction potential (ORP) inside the reactors dropped, up to –300 mv, with glucose as carbon source. As the reactors were switched over to methanol, ORP increased to –190 mv. The granular sludge developed inside the reactors was light brown in colour when acetate and glucose were used as substrate, which turned dark brown to black at the end of methanol run. Biomass yield in terms of volatile suspended solids was observed as 0.15, 0.089 and 0.14 g per gram of COD removal for acetate, glucose and methanol, respectively.     

Rapid granulation and sludge retention for tetrachloroethylene removal in an upflow anaerobic sludge blanket reactor

A laboratory scale upflow anaerobic sludge blanket (UASB) reactor was operated at 35 °C for over 200 days to investigate the granulation mechanism during tetrachloroethylene (TCE) biodegradation. Anaerobic, unacclimated sludge and glucose were used as seed and primary substrate, respectively. TCE-degrading granules developed after 1.5 months of start-up. They grew at an accelerated pace for 7 months. The TCE-degrading granules had a maximum diameter of 2.5 mm and specific methanogenic activity of 1.32 g chemical oxygen demand (COD) g^–1 total suspended solid (TSS) day^–1. 94% COD and 90% TCE removal efficiencies were achieved when the reactor was operating at loading rates as high as 160 mg TCE l^–1 day^–1 and 14 g COD l^–1 day^–1, after 230 days of continuous operation.     

Influence of pH shocks on trace metal dynamics and performance of methanol fed granular sludge bioreactors

The influence of pH shocks on the trace metal dynamics and performance of methanol fed upflow anaerobic granular sludge bed (UASB) reactors was investigated. For this purpose, two UASB reactors were operated with metal pre-loaded granular sludge (1mM Co, Ni and Fe; 30°C; 96h) at an organic loading rate (OLR) of 5gCOD l reactor^–1d^–1. One UASB reactor (R1) was inoculated with sludge that originated from a full scale reactor treating alcohol distillery wastewater, while the other reactor (R2) was inoculated with sludge from a full scale reactor treating paper mill wastewater. A 30h pH shock (pH 5) strongly affected the metal retention dynamics within the granular sludge bed in both reactors. Iron losses in soluble form with the effluent were considerable: 2.3 and 2.9% for R1 and R2, respectively, based on initial iron content in the reactors, while losses of cobalt and nickel in soluble form were limited. Sequential extraction of the metals from the sludge showed that cobalt, nickel, iron and sulfur were translocated from the residual to the organic/sulfide fraction during the pH shock in R2, increasing 34, 47, 109 and 41% in the organic/sulfide fraction, respectively. This is likely due to the modification of the iron sulfide precipitate stability, which influences the extractability of iron and trace metals. Such a translocation was not observed for the R1 sludge during the first 30h pH shock, but a second 4day pH shock induced significant losses of cobalt (18%), iron (29%) and sulfur (29%) from the organic/sulfide fraction, likely due to iron sulfide dissolution and concomitant release of cobalt. After the 30h pH shock, VFA accumulated in the R2 effluent, whereas both VFA and methanol accumulated in R1 after the 4day pH shock. The formed VFA, mainly acetate, were not converted to methane due to the loss of methanogenic activity of the sludge on acetate. The VFA accumulation gradually disappeared, which is likely to be related to out-competition of acetogens by methanogens. Zinc, copper and manganese supply did not have a clear effect on the acetate removal and methanol conversion, but zinc may have induced the onset of methanol degradation after day 152 in R1.     

Enzymatic pre-hydrolysis and anaerobic degradation of wastewaters with high fat contents

Dairy wastewaters containing elevated fat and grease levels (868 mg l^–1) were treated in an upflow anaerobic sludge blanket reactor (UASB) and resulted in effluents of high turbidity (757 nephelometric turbidity units), volatile suspended solids up to 944 mg l^–1 and COD removal below 50%. When the same dairy wastewater was pre-treated with 0.1% (w/v) of fermented babassu cake containing Penicillium restrictum lipases, turbidity and volatile suspended solids were decreased by 75% and 90%, respectively, and COD removal was as high as 90%.     

Inorganic composition and microbial characteristics of methanogenic granular sludge grown in a thermophilic upflow anaerobic sludge blanket reactor

An upflow anaerobic sludge blanket reactor was operated under thermophilic conditions (55° C) for 160 days by feeding a wastewater containing sucrose as the major carbon source. The reactor exhibited a satisfactory performance due to the formation of well-settling granulated sludge, achieving a total organic carbon (TOC) removal of above 80% at an organic loading rate of 30 kg total organic C m^–3 day^–1. Structural and microbial properties of the methanogenic granular sludge were examined using scanning electron microscope X-ray analyses and serum vial activity tests. All the thermophilic granules developed showed a double-layered structure, comprised of a black core portion and a yellowish exterior portion. The interior cope portion contained abundant crystalline precipitates of calcium carbonate. Calcium-bound phosphorus was also present more prominently in the core portion than in the exterior portion. Methanogenic activities of the thermophilic granules both from acetate and from H₂ increased with increasing vial-test temperature in the range of 55–65° C [from 1.43 to 2.36 kg CH₄ chemical oxygen demand (COD) kg volatile suspended solids (VSS)^–1 day^–1 for acetate and from 0.85 to 1.11 kg CH₄ COD kg VSS^–1 day^–1 for H₂]. On the other hand, propionate-utilizing methanogenic activity was independent of vial-test temperature, and was much lower (0.1–0.12 kg CH₄ COD kg VSS^–1 day^–1) than that from either acetate or H₂. Acetate consumption during vial tests was considerably inhibited by the presence of H₂ in the headspace, indicating that a syntrophic association between acetate oxidizers and H₂-utilizing methane-producing bacteria was responsible for some portion of the overall acetate elimination by the theromophilically grown sludge.     

Characteristics of methanogenic granules grown on propionate in an upflow anaerobic sludge blanket (UASB) reactor

Granulation of a propionate-degrading consortia was performed with a mesophilic propionate-acclimatized sludge in an upflow anaerobic sludge blanket (UASB) reactor. The granules formed were relatively small, ranging mainly from 0.3 to 0.6 mm in diameter, but had an excellent sedimentation velocity due to a high specific gravity of 1.355 g/cm³ (ash content, 48.2%). The ash consisted mainly of calcium (30.2%), phosphorus (19.7%), and magnesium (3.95%) forming plate crystals in the granules. The populations of three bacterial trophic groups present in the granules, propionate-degraders, hydrogenotrophic and aceticlastic methanogens were 5.6 × 10⁸, 1.6 × 10¹⁰, and 2 × 10⁹ (in most probable number/g mixed-liquor volatile suspended solids [MLVSS]), respectively, while the specific utilization rates of propionate, hydrogen, and acetate of the granules were 9.4, 850, and 20.9 (mmol/g MLVSS·d), respectively. Electron microscopic analysis showed that Methanothrix spp. appeared dominant over the granules. Total granular sludge concentration retained in the UASB reactor during 178 d of operation was 80.0 g mixed-liquor suspended solids (MLSS)/l-reactor, corresponding to 41.4 g MLVSS/l-reactor, which realized a high-rate methanogenic fermentation of propionate of 85 g chemical oxygen demand (COD)/l-reactor·d.     

Acetate treatment in 70°C upflow anaerobic sludge-blanket (UASB) reactors: start-up with thermophilic inocula and the kinetics of the UASB sludges

This study focused on the use of thermophilic anaerobic granulae in the start-up of 70°C acetate-fed upflow anaerobic sludge-blanket (UASB) reactors and the kinetics of granulae grown at 70°C. In the UASB reactors, chemical oxygen demand removal commenced within 48 h of the start-up. The maximum reduction in chemical oxygen demand was 84% with the feed containing yeast and 71% without a yeast supplement. In the bioassays, the yeast-grown sludge converted 98% of the acetate consumed to methane as compared to 92% for the sludge grown without yeast. The highest initial specific methane production rate (µ_{CH 4}) of the UASB sludges grown at 70°C was 0.088 h^–1 at an acetate concentration of 4.6 mM. The higher initial acetate concentration was found to prolong the lag-phase in methane production significantly and to decrease the µ_{CH 4}. The half-saturation constant (K _s), the inhibition constant (K _i), the inhibition response coefficient (n), and the µ_{CH 4} ^max, calculated according to a modified Haldane equation, were 1.5 mM, 2.8 mM, 0.8, and 0.28 h^–1, respectively. The prolonged starvation of the 70°C sludge (15 days) decreased the µ_{CH 4} from about 0.022 h^–1 to 0.011 h^–1 and increased the lag phase in methane production from 6 h to 24 h as compared to non-starved sludge.     

Anaerobic ammonium oxidation process in an upflow anaerobic sludge blanket reactor with granular sludge selected from an anaerobic digestor

The purpose of this work was to evaluate the development of the anammox process by the use of granular sludge selected from a digestion reactor as a potential seed source in a lab-scale UASB (upflow anaerobic sludge blanket) reactor system. The reactor was operated for approximately 11 months and was fed by synthetic wastewater. After 200 days of feeding with NH₄ ⁺ and NO₂ ⁻ as the main substrates, the biomass showed steady signs of ammonium consumption, resulting in over 60% of ammonium nitrogen removal. This report aims to present the results and to more closely examine what occurs after the onset of anammox activity, while the previous work described the start-up experiment and the presence of anammox bacteria in the enriched community using the fluorescencein situ hybridization (FISH) technique. By the last month of operation, the consumed NO₂ ⁻N/NH₄ ⁺-N ratio in the UASB reactor was close to 1.32, the stoichiometric ratio of the anammox reaction. The obtained results from the influentshutdown test suggested that nitrite concentration would be one key parameter that promotes the anammox reaction during the start-up enrichment of anammox bacteria from granular sludge. During the study period, the sludge color gradually changed from black to red-brownish.     

Kinetic Modelling and Characterization of Microbial Community Present in a Full-Scale UASB Reactor Treating Brewery Effluent

The performance of a full-scale upflow anaerobic sludge blanket (UASB) reactor treating brewery wastewater was investigated by microbial analysis and kinetic modelling. The microbial community present in the granular sludge was detected using fluorescent in situ hybridization (FISH) and further confirmed using polymerase chain reaction. A group of 16S rRNA based fluorescent probes and primers targeting Archaea and Eubacteria were selected for microbial analysis. FISH results indicated the presence and dominance of a significant amount of Eubacteria and diverse group of methanogenic Archaea belonging to the order Methanococcales, Methanobacteriales, and Methanomicrobiales within in the UASB reactor. The influent brewery wastewater had a relatively high amount of volatile fatty acids chemical oxygen demand (COD), 2005 mg/l and the final COD concentration of the reactor was 457 mg/l. The biogas analysis showed 60–69 % of methane, confirming the presence and activities of methanogens within the reactor. Biokinetics of the degradable organic substrate present in the brewery wastewater was further explored using Stover and Kincannon kinetic model, with the aim of predicting the final effluent quality. The maximum utilization rate constant U _max and the saturation constant (K _B) in the model were estimated as 18.51 and 13.64 g/l/day, respectively. The model showed an excellent fit between the predicted and the observed effluent COD concentrations. Applicability of this model to predict the effluent quality of the UASB reactor treating brewery wastewater was evident from the regression analysis (R ²?=?0.957) which could be used for optimizing the reactor performance.     

Extending the diffuse layer model of surface acidity constant behaviour: II. Estimation of intrinsic acidity and electrolyte ion site binding constants

Abstract

The main objective of this work was to study the capacity of bioaccumulation of copper in an upflow anaerobic sludge blanket (UASB) reactor, for the treatment of acid mine drainages (AMD). UASB reactor of 0.8 L was fed with sodium acetate, the organic loading rate (OLR) was set at 2.0gCOD/Ld, and experiments were performed in the reactor during 115 days. After 30 days, the COD removal efficiency was 90%. In the stationary stage, the higher production methane was 0.253 L/Ld. The reactor was added with 20 mgCu(II)/L during 30 days. The copper bioaccumulation was 98% and it was accumulated gradually in sludge until reaching a 61.6 mgCu(II)/gTS. The toxicity study demonstrated that the copper concentration at which the level of specific methanogenic activity (SMA) of the biogranules was reduced to 50% of the control (IC₅₀), was 280 mgCu(N)/L     

Acetate Degradation at 70°C in Upflow Anaerobic Sludge Blanket Reactors and Temperature Response of Granules Grown at 70°C

Anaerobic acetate degradation at 70°C and at 55°C (as a reference) was studied by running laboratory upflow anaerobic sludge blanket (UASB) reactors inoculated with mesophilic granular sludge. In UASB reactors fed with acetate-containing media (3 g of chemical oxygen demand [COD] per liter, corresponding to 47 mM acetate) approximately 50 days was needed at 70°C and less than 15 days was needed at 55°C to achieve an effluent COD of 500 to 700 mg/liter. In the UASB reactors at both 70 and 55°C up to 90% of the COD was removed. Batch assays showed that sludges from two 70°C UASB reactors, one run at a low effluent acetate concentration and the other run at a high effluent acetate concentration, exhibited slightly different responses to temperatures in the range from 37 to 70°C. Both 70°C sludges, as well as the 55°C sludge, produced methane at temperatures of 37 to 73°C. The 55°C sludge exhibited shorter lag phases than the 70°C sludges and higher specific methane production rates between 37 and 65°C.     

Scanning electron microscopy of biofilm development in anaerobic fixed-bed reactors: Influence of the inoculum

Summary Scanning electron microscopy was applied to evaluate the influence of inoculum on efficiency of initial biofilm formation and reactor performance. Five anaerobic fixed-bed reactors were inoculated with anaerobic sludges from different sources and operated in parallel under identical conditions with defined wastewater and acetate, propionate and butyrate as constituents In all sludges Methanothrix sp. was the predominant acetotroph. The reactors inoculated with anaerobic sludge adapted to the wastewater achieved the highest space loading with 21.0 g COD/l·d after 58 days. The inoculation with granular sludge from an upflow anaerobic sludge blanket (UASB) reactor resulted in significantly less reactor efficiency. Time course of biofilm formation and biofilm thickness (ranging from 20–200 m) depended on the type of inoculum.     

A novel UASB–MFC–BAF integrated system for high strength molasses wastewater treatment and bioelectricity generation

An up-flow anaerobic sludge blanket reactor–microbial fuel cell–biological aerated filter (UASB–MFC–BAF) system was developed for simultaneous bioelectricity generation and molasses wastewater treatment in this study. The maximum power density of 1410.2 mW/m² was obtained with a current density of 4947.9 mA/m² when the high strength molasses wastewater with chemical oxygen demand (COD) of 127,500 mg/l was employed as the influent. The total COD, sulfate and color removal efficiencies of the proposed system were achieved of 53.2%, 52.7% and 41.1%, respectively. Each unit of this system had respective function and performed well when integrated together. The UASB reactor unit was mainly responsible for COD removal and sulfate reduction, while the MFC unit was used for the oxidation of generated sulfide with electricity generation. The BAF unit dominated color removal and phenol derivatives degradation. This study is a beneficial attempt to combine MFC technology with conventional anaerobic–aerobic processes for actual wastewater treatment.     

Different types of sludge granules in UASB reactors treating acidified wastewaters

The influence of a high energy substrate, i.e. sucrose, on the granular sludge yield and the development of different types of granular sludge was investigated by using Upflow Anaerobic Sludge Bed (UASB) reactors fed with synthetic wastewater. The feed COD was a mixture of volatile fatty acids (VFA) i.e., 20, 40, and 40% of the COD as C₂-, C₃-, and C₄-VFA, respectively. Furthermore, experiments were carried out in which 10 and 30% of the VFA COD was substituted with sucrose. The following distinctly different types of granules were observed in each testrun: in the reactor fed with solely VFA, black (B) and white (W) granules developed; in the reactor fed with a mixture of 90% VFA and 10% sucrose, three types of granules i.e., B, W, and grey (G) granules could be seen; in the reactor fed with 70% VFA and 30% sucrose, only W and G granules were found. The granular sludge yield increased proportional to the amount of sucrose COD. At steady-state performance of the reactors, specific acidogenic (SAA) and methanogenic (SMA) activity tests on these granules revealed that B granules had the highest SMA with low SAA. The W granules had very high SMA with low SAA. G granules gave the highest SAA with a considerable SMA. Measurement of coenzyme F₄₂₀ revealed that B granules consist mainly of acetoclastic methanogens. The fore-mentioned tests were supplemented with analyses of the wash-out cells present in the reactor effluent and the results suggested that acidogens, if present, prevail at the granule surface. The B granules were particularly rich in Ca, Mn, and Zn minerals. The size distribution analysis showed that the granule diameter increased in the following order: B相似文献   

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

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

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

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