Granules In Sequencing Batch Reactor Research Articles

Effects of high-concentration influent suspended solids on aerobic granulation in sequencing batch reactors treating real textile wastewater

The formation of aerobic granular sludge (AGS) in real textile wastewater (TWW) is time-consuming and challenging. The present study investigated the effects of high-concentration influent suspended solids (SS) on aerobic granulation, pollutant removal, microbial activity, and community in the real TWW treatment by using two sequencing batch reactors (R1: 41.7 ± 22.8 mg influent-SS/L; R2: 416.1 ± 21.4 mg influent-SS/L). The results showed that complete granulation was achieved in R1 within 97 days (SVI30: 34.5 mL/g, SVI30/SVI5 = 0.91), while it only required 52 days in R2 (SVI30: 18.2 mL/g, SVI30/SVI5 = 0.92). The high-concentration influent SS also enhanced compactness and settleability of AGS. Long-term adaption of sludge improved the COD removal from real TWW, which was possibly due to the increase in phyla Firmicutes and Actinobacteria abundances. The real TWW did not adversely affect the nitrification process as indicated by the high NH4+-N removal in both reactors (>93 %). Although the formation of compact AGS in R2 did not exhibit better removal performance under the present experimental condition, it exhibited the potential for better COD removal from real TWW as indicated by the higher microbial activity and functional bacterial abundances in R2 than in R1.

Formation, extracellular polymeric substances and microbial community of aerobic granules enhanced by microbial flocculant compared with poly-aluminum chloride

This study is the first reported research in which microbial flocculant (MBF) was applied to accelerate the formation and strengthen the stability of aerobic granules in sequencing batch reactors. To better evaluate the effects of MBF, poly-aluminum chloride (PAC) was used as a reference. The main metrics were the characteristics of granule formation, extracellular polymeric substances (EPS) and characteristics of the microbial community. MBF resulted in granules that matured 13 days earlier than in the control reactor (without flocculant), but 17 days later than PAC-fed granules. Scanning electron microscope images showed granules from both MBF and control reactors were covered with a mesh structure; in contrast, the surface of PAC-fed granules was smoother. All three flocculant treatments achieved high contaminant removal rates. EPS analysis demonstrated that protein and β-polysaccharide were uniformly distributed in the MBF-fed granules, while a bilayer consisting of a protein shell and β-polysaccharide core existed in PAC-fed granules. Both MBF and PAC strengthen the resistance of granules to hydrolase. At the genus level and compared to that of the control reactor, the microbial community in the MBF-fed and PAC-fed reactors was dominated by relatively heavy bacteria that improved sludge settling performance. Furthermore, the MBF reactor had the lowest abundance of EPS producers, while the PAC reactor had the highest abundance of these microorganisms.

Biodiesel production from microbial granules in sequencing batch reactor

Effect of reaction variables of in situ transesterification on the biodiesel production, and the characteristic differences of biodiesel obtained from aerobic granular sludge (AG) and algae-bacteria granular consortia (AAG) were investigated. The results indicated that the effect of variables on the biodiesel yield decreased in the order of methanol quantity > catalyst concentration > reaction time, yet the parameters change will not significantly affect biodiesel properties. The maximum biodiesel yield of AAG was 66.21 ± 1.08 mg/g SS, what is significant higher than that of AG (35.44 ± 0.92 mg/g SS). Although methyl palmitate was the dominated composition of biodiesel obtained from both granules, poly-unsaturated fatty acid in the AAG showed a higher percentage (21.86%) than AG (1.2%) due to Scenedesmus addition. Further, microbial analysis confirmed that the composition of biodiesel obtained from microbial granules was also determined by bacterial community, and Xanthomonadaceae and Rhodobacteraceae were the dominant bacteria of AG and AAG, respectively.

Treatment of Adsorbable Organic Halide (AOX) from pulp and paper industry wastewater using aerobic granules in pilot scale SBR

Aerobic granulation of activated sludge was achieved in a pilot scale column type sequencing batch reactor (SBR) employed for the treatment of pulp and paper industry wastewater containing Adsorbable Organic Halide (AOX) in the range of 15–20mg/L. Throughout the 780days of operation the biomass trends to remain in between 7 and 8g/L MLVSS and SVI reduced to 60–80mL/g MLSS. After applying different selection pressure the average size of aerobic granule in the SBR was in the range of 2–4mm. After achieving steady state conditions in the pilot plant, at an organic loading rateof 4.5kg COD m−3day−1 at 6h HRT the degradation of AOX was significant and the effluent AOX concentration of below 5mg/L was achieved. The results achieved in the study exhibit the viability of formation of aerobic granules in pilot scale SBR and maintenance of long-term strength of aerobic granular sludge with a high reduction of AOX in pulp and paper industry wastewater.

Mass transfer kinetics of biosorption of nitrogenous matter from palm oil mill effluent by aerobic granules in sequencing batch reactor

ABSTRACTUnderstanding of mass transfer kinetics is important for biosorption of nitrogen compounds from palm oil mill effluent (POME) to gain a mechanistic insight into future biological processes for the treatment of high organic loading wastewater. In this study, the rates of global and sequential mass transfer were determined using the modified mass transfer factor equations for the experiments to remove nitrogen by aerobic granular sludge accumulation in a sequencing batch reactor (SBR). The maximum efficiencies as high as 97% for the experiment run at [kLa]g value of 1421.8 h−1 and 96% for the experiment run at [kLa]g value of 9.6 × 1037 h−1 were verified before and after the addition of Serratia marcescens SA30, respectively. The resistance of mass transfer could be dependent on external mass transfer that controls the transport of nitrogen molecule along the experimental period of 256 days. The increase in [kLa]g value leading to increased performance of the SBR was verified to contribute to the future applications of the SBR because this phenomenon provides new insight into the dynamic response of biological processes to treat POME.

Effects of phenol on physicochemical properties and treatment performances of partial nitrifying granules in sequencing batch reactors

This study attempts to investigate the effect of phenol on physicochemical properties and treatment performances of partial nitrifying granules (PNGs). Two sequencing batch reactors (SBRs) fed with synthetic ammonium wastewaters were operated in absence (R1) or presence (R2) of phenol. The PNGs in R1 maintained excellent partial nitrification performance and relatively stable physicochemical properties, and exhibited compact and regular shaped structure with a cocci-dominant surface. However, as phenol concentration was stepwise increased from 0 to 300mg/L in R2, filamentous bacteria appeared and gradually dominated within granules, which in turn resulted in settleability deterioration. Most notably, granules in R2 got easier to agglomerate in the reactor walls and then been washed out with effluent, leading to significant biomass loss, frequent outflow pipe blockage, and eventual system failure. The extracellular polymeric substances (EPS) contents including proteins and polysaccharides in R2 reached 1.8 and 1.7 times of that in R1, respectively, indicating that the presence of phenol played an important role on EPS production. Removal efficiency of ammonium and phenol remained high, but dropped sharply when phenol concentration reached 300mg/L. Moreover, the failed maintenance of partial nitrification was observed due to the revival of nitrite oxidizing bacteria (NOB) within granules after phenol exposure, which was confirmed by quantitative fluorescence in situ hybridization (FISH) analysis. Overall this study demonstrates that phenol had negative effects on PNGs, and pretreatment to eliminate phenolic substances is recommended when using PNGs for wastewater treatment.

Operation mode and external carbon dose as determining factors in elemental composition and morphology of aerobic granules

Abstract The elemental composition and morphology of aerobic granules in sequencing batch reactors (GSBRs) treating high-nitrogen digester supernatant was investigated. The investigation particularly focused on the effect of the number of anoxic phases (one vs. two) in the cycle and the dose of external organics loading (450 mg COD/(L·cycle) vs. 540 mg COD/(L·cycle)) on granule characteristics. Granules in all reactors were formed of many single cells of rod and spherical bacteria. Addition of the second anoxic phase in the GSBR cycle resulted in enhanced settling properties of the granules of about 10.6% and at the same time decreased granule diameter of about 19.4%. The study showed that external organics loading was the deciding factor in the elemental composition of biomass. At 540 mg COD/(L·cycle) the granules contained more weight% of C, S and N, suggesting more volatile material in the granule structure. At lower organics loadings granules had the higher diameter of granules which limited the diffusion of oxygen and favored precipitation of mineral compounds in the granule interior. In this biomass higher content of Mg, P and Ca, was observed.

Denitrification accelerates granular sludge formation in sequencing batch reactors

In this study, the role of denitrification on aerobic granular sludge formation in sequencing batch reactors (SBRs) was investigated. Formation of aerobic granular sludge was faster in SBRs fed with varying concentrations of nitrate or nitrite as compared to control, which received no nitrate or nitrite in the feed. The majority of the fed nitrate or nitrite was denitrified in the anoxic static fill phase, prior to aerobic reaction phase. Sludge characterization showed accumulation of calcium and chemical signature of calcium carbonate in the nitrate-fed SBRs. Feeding of sodium nitroprusside, a known nitric oxide (NO) donor, enhanced aggregation, production of extracellular polymeric substances and formation of aerobic granular sludge. The results support the hypothesis that denitrification facilitates cell aggregation and accelerates aerobic sludge granulation through NO signaling and CaCO3 formation. Nitrate or other intermediates of heterotrophic denitrification, therefore, have a positive effect on aerobic granulation in SBRs.

Rapid start-up and improvement of granulation in SBR

BackgroundThe aim of this study is to accelerate and improve aerobic granulation within a Sequencing Batch Reactor (SBR) by cationic polymer addition.MethodsTo identify whether the polymer additive is capable of enhancing granule formation, two SBRs (R1 and R2, each 0.15 m in diameter and 2 m in height) are used by feeding synthetic wastewater. The cationic polymer with concentration of 30 to 2 ppm is added to R2, while no cationic polymer is added to R1.ResultsResults show that the cationic polymer addition causes faster granule formation and consequently shorter reactor start-up period. The polymer-amended reactor contains higher concentration of biomass with better settling ability (23% reduction in SVI15) and larger and denser granules (112% increase of granular diameter). In addition, the results demonstrate that the cationic polymer improve the sludge granulation process by 31% increase in Extracellular Polymer Substance(EPS) concentration, 7% increase in Specific Oxygen Uptake Rate(SOUR), 18% increase in hydrophobicity, and 17% reduction in effluent Mixed Liquor Suspended Solid(MLSS) concentration.ConclusionsConcludingly, it is found that using the cationic polymer to an aerobic granular system has the potential to enhance the sludge granulation process.

Effects of antibiotics on characteristics and microbial resistance of aerobic granules in sequencing batch reactors

AbstractThe response of characteristics and microbial resistance of aerobic granules to sulfamethazine, oxytetracycline, and ciprofloxacin at ppb level in swine wastewater was investigated in this study. Results showed that no significant changes in physical strength, average granules size, and settling property of aerobic granules were observed with target antibiotics exposure (p > 0.05). However, compared to the control group, the protein/polysaccharide ratio and zeta potential of aerobic granules in treatment groups showed a higher level (p < 0.05). Meanwhile, the specific removal rates of organics and ammonia nitrogen in reactors with antibiotics addition all decreased greatly, and the inhibition rates of those were 21–29% and 35–42%, respectively. In terms of microbial resistance, the presence of target antibiotics would obviously increase the relative abundances of antibiotics resistance bacteria and antibiotics resistance genes in aerobic granules, ranging from 0.5 to 5 orders of magnitude; thereby...

Studies on the interactions of Ca2+ and Mg2+ with EPS and their role in determining the physicochemical characteristics of granular sludges in SBR system

The main objectives of the present study were to investigate the interactions of divalent metals (Ca2+ and Mg2+) with protein and polysaccharide components of extracellular polymeric substances (EPS) and to deduce their role in imparting different physicochemical characteristics to aerobic granules in sequencing batch reactor (SBR) system. Three reactors were run for 60 days; R-1 functioned as a control reactor, whereas R-2 and R-3 were operated by dosing 25mg/L of Ca2+ and Mg2+, respectively, and the other operating conditions were similar in all of the SBRs. The granulation rate, particle size and sludge settleability were rapidly increased by Ca2+ addition, whereas the sludge dewaterability was significantly enhanced by Mg2+ augmentation. During the investigations, R-1, R-2 and R-3 had 1.31, 2.98 and 1.58 times higher quantities of polysaccharides, whereas proteins were 1.28, 1.74 and 2.41 times, respectively, more abundant than seed sludge. The divalent metals profoundly changed the composition of EPS, but their total contents were almost similar. XPS and FTIR results showed that Ca2+ bonded strongly with hydroxyl groups of polysaccharides due to there being less steric hindrance than proteins, and Mg2+ preferably bonded with amide groups of proteins and found no such hindrance due to its smaller size and thus changed the composition of EPS, which eventually altered the granular sludge characteristics.

Cultivation of aerobic granules under different pre-anaerobic reaction times in sequencing batch reactors

This work investigated the influence of pre-anaerobic reaction time on aerobic granulation in sequencing batch reactors (SBRs). For this purpose, a purely aerobic SBR (R1) was operated as a reference, while two other reactors, namely R2 and R3, were running with anaerobic/aerobic reaction times of 85min/265min and 175min/175min, respectively. Results showed that the compact granules cultivated in R1 disappeared in the early days of operation and gradually transited to large-sized ones with filamentous microorganisms as the backbone mostly ranging in size between 2 and 5mm. The aerobic granules in R2 appeared to be more compact in structure, while the cultivated granules in R3 showed a fluffy, loose and dispersed structure morphology with poorer settling ability (SVI30=673mL/g at the end of experiment). Investigation of tightly bound extracellular polymeric substances (TB-EPS) showed that the aerobic granules in R2 produced lower TB-EPS in comparison with two other reactors, which indicates that higher TB-EPS quantity in R1 and R3 did not guarantee the stability of granular structure. As a result, pre-anaerobic reaction time of 85min in R2 positively affected the compactness and structural stability of granules, while more than 91% of influent COD could remove all the time.

Fungi aerobic granules and use of Fe(III)-treated granules for biosorption of antimony(V)

This study cultivated fungi aerobic granules in sequencing batch reactor with glucose as carbon source at pH 4.5, which were mainly composed of single fungus Geotrichum fragrans. Iron precipitate was then produced with 0.1M FeCl3 onto the granules surface, accompanied with removal of Ca, Mg, K and Na from the biomass matrix. The Fe(III)-treated granules had 4.3-folds higher adsorption capacity of antimony(V) than the original granules, peaked at pH 3.4 at a Langmuir maximum capacity of 111mgg−1 of dry mass. Fe(III) treatment was for the first time applied to convert fungi aerobic granules to cost-effective biosorbent for Sb(V).

Modeling and optimization of granulation process of activated sludge in sequencing batch reactors

Aerobic granulation is a promising process for wastewater treatment, but this granulation process is very complicated and is affected by many factors. Thus, a mathematical model to quantitatively describe such a granulation process is highly desired. In this work, by taking into account all of key steps including biomass growth, increase in particle size and density, detachment, breakage and sedimentation, an one-dimensional mathematic model was developed to simulate the granulation process of activated sludge in a sequencing batch reactor (SBR). Discretization methodology was applied by dividing operational time, sedimentation process, size fractions and slices into discretized calculation elements. Model verification and prediction for aerobic granulation process were conducted under four different conditions. Four parameters indicative of granulation progression, including mean radius, biomass discharge ratio, total number, and bioparticle size distribution, were predicted well with the model. An optimum controlling strategy, automatically adjusted of settling time, was also proposed based on this model. Moreover, aerobic granules with a density higher than 120 g VSS/L and radius in a range of 0.4-1.0 mm were predicted to have both high settling velocity and substrate utilization rate, and the corresponding optimum operating conditions were be determined. Experimental results demonstrate that the developed model is appropriate for simulating the formation of aerobic granules in SBRs. These results are useful for designing and optimizing the cultivation and operation of aerobic granule process.

Biodegradation of p-cresol by aerobic granules in sequencing batch reactor

The cultivation of aerobic granules in sequencing batch reactor for the biodegradation of p-cresol was studied. The reactor was started with 100 mg/L of p-cresol. Aerobic granules first appeared within one month of start up. The granules were large and strong and had a compact structure. The diameter of stable granules was in the range of 1–5 mm. The integrity coefficient and granules density was found to be 96% and 1046 kg/m3, respectively. The settling velocity of granules was found to be in the range of 2×10−2–6×10−2 m/sec. The aerobic granules were able to degrade p-cresol upto 800 mg/L at a removal efficiency of 88%. Specific p-cresol degradation rate in aerobic granules followed Haldane model for substrate inhibition. High specific p-cresol degradation rate up to 0.96 g p-cresol/(g VSS·day) were sustained upto p-cresol concentration of 400 mg/L. Higher removal efficiency, good settling characteristics of aerobic granules, makes sequencing batch reactor suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.

Effect of sludge discharge positions on steady-state aerobic granules in sequencing batch reactor (SBR)

We have investigated the effect of sludge discharge location on the steady-state aerobic granules in sequencing batch reactors (SBRs). Two SBRs were operated concurrently with the same sludge retention time using sludge discharge ports at: (a) the reactor bottom in R1; and (b) the reactor middle-lower level in R2. Results indicate that both reactors could maintain sludge granulation and stable operation, but the two different sludge discharge methods resulted in significantly different aerobic granule characteristics. Over 30 days, the chemical oxygen demand (COD) removal of the two reactors was maintained at similar levels (above 96%), and typical bioflocs were not observed. The average aerobic granule size in R2 was twice that in R1, as settling velocity increased in proportion to size increment. Meanwhile, the production yields of polysaccharide and protein content in R2 were always higher than those in R1. However, due to mass transfer limitations and the presence of anaerobes in the aerobic granule cores, larger granules had a tendency to disintegrate in R2. Thus, we conclude that a sludge discharge port situated at the reactor bottom is beneficial for aerobic granule stability, and enhances the potential for long-term aerobic granule SBR operation.

Influence of aeration intensity on mature aerobic granules in sequencing batch reactor

Aeration intensity is well known as an important factor in the formation of aerobic granules. In this research, two identical lab-scale sequencing batch reactors with aeration intensity of 0.8 (R1) and 0.2 m(3)/h (R2) were operated to investigate the characteristics and kinetics of matured aerobic granules. Results showed that both aeration intensity conditions induced granulation, but they showed different effects on the characteristics of aerobic granules. Compared with the low aeration intensity (R2), the aerobic granules under the higher aeration intensity (R1) had better physical characteristics and settling ability. However, the observed biomass yield (Y obs) in R1 [0.673 kg mixed liquor volatile suspended solids (MLVSS)/kg chemical oxygen demand (COD)] was lower than R2 (0.749 kg MLVSS/kg COD). In addition, the maximum specific COD removal rates (q max) and apparent half rate constant (K) of mature aerobic granular sludge under the two aeration intensities were at a similar level. Therefore, the matured aerobic granule system does not require to be operated in a higher aeration intensity, which will reduce the energy consumption.

Development of aerobic granules in sequencing batch reactor with p-nitrophenol as sole carbon source

The present study was aimed at the development of aerobic granules in sequencing batch reactor (SBR) for the biodegradation of p-nitrophenol (PNP). The reactor was started with 50 mg L−1 of PNP. Aerobic granules first appeared within 1 month of the start up of the reactor. The granules were large and strong and had a compact structure. The diameter of stable granules on day 200 was in the range of 2–3 mm. The integrity coefficient and granule density was found to be 98% and 1,031 kg m−3 respectively. The settling velocity of granules was found to be in the range of 3 × 10−2 to 4 × 10−2m s−1. The aerobic granules were able to degrade PNP up to 700 mg L−1 at a removal efficiency of 87%. Gas chromatography–mass spectrometry studies confirmed that the biodegradation of PNP occurred by an initial oxygenase attack that resulted in the release of nitrite and the accumulation of hydroquinone. The specific PNP degradation rate in aerobic granules followed the Haldane model for substrate inhibition. A high specific PNP degradation rate up to 0.872 g PNP g−1 VSS−1 d−1 was sustained up to PNP concentration of 200 mg L−1. Higher removal efficiency, good settling characteristics of aerobic granules, makes a SBR suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.

Essential roles of eDNA and AI-2 in aerobic granulation in sequencing batch reactors operated at different settling times

Settling time has been considered as one of the most effective selection pressures for aerobic granulation in sequencing batch reactors (SBRs), i.e., poorly settleable bioparticles would be washed out from SBRs, and the heavy and good settling ones would be retained at a shorter setting time. However, its biological implication remains unclear. This study investigated the microbiological mechanisms of aerobic granulation at different settling times. It provided experimental evidence for the first time showing that a shorter settling time could enhance release of extracellular DNA through cell lysis, which in turn initiated microbial aggregation leading to increased biomass size and density, while AI-2-mediated quorum sensing was found not to be involved in initial aggregation. It was further shown that the AI-2-mediated quorum sensing system was activated to regulate the growth and maturation of aerobic granules when the biomass density reached a threshold of 1.025 g ml(-1). It appears from this study that a short settling time of SBR would induce microbiological and physiological responses of bacteria which are required at different stages of aerobic granulation and provide new insights into biological mechanisms of settling time-triggered aerobic granulation.

The study of membrane fouling in the view of operating conditions and parameters

Aerobic granulation of activated sludge was achieved in a pilot scale column type sequencing batch reactor (SBR) employed for the treatment of pulp and paper industry wastewater containing Adsorbable Organic Halide (AOX) in the range of 15–20 mg/L. Throughout the 780 days of operation the biomass trends to remain in between 7 and 8 g/L MLVSS and SVI reduced to 60–80 mL/g MLSS. After applying different selection pressure the average size of aerobic granule in the SBR was in the range of 2–4 mm. After achieving steady state conditions in the pilot plant, at an organic loading rateof 4.5 kg COD m−3day−1 at 6 h HRT the degradation of AOX was significant and the effluent AOX concentration of below 5 mg/L was achieved. The results achieved in the study exhibit the viability of formation of aerobic granules in pilot scale SBR and maintenance of long-term strength of aerobic granular sludge with a high reduction of AOX in pulp and paper industry wastewater.