Aerobic Granulation

The present paper has examined the degrading ability of phenol-oxidizing bacterium, Ralstonia eutropha, for biological removal of methylene blue (MB) from aqueous solutions under aerobic conditions. Results show that MB has been extensively eliminated as a co-metabolism in the presence of supplementary carbon (glucose) and nitrogen (yeast extract and peptone) sources and the experimental observations indicate that MB is initially adsorbed on the cell"s surface, in accordance to Langmuir Theory, then to be degraded by the cell. The type of nitrogen source, initial pH, aeration rate, and the presence of CaCl 2 are all influential factors in the process of MB removal. The biodegradation kinetics modeling has determined that while playing an uncompetitive role, MB inhibits its biodegradation at high concentrations. According to the best fit Han-Levenspiel Model, the maximum MB specific biodegradation rate (r max), half-saturation concentration of MB (K S), maximum allowable MB conc...

Granulation of activated sludge is an increasingly important area within the field of wastewater treatment. Granulation is usually achieved by high hydraulic selection pressure, which results in the wash-out of slow settling particles. The effect of the harsh wash-out conditions on the granular sludge ecosystem is not yet fully understood, but different bacterial groups may be affected to varying degrees. In this study, we used high-throughput amplicon sequencing to follow the community composition in granular sludge reactors for 12 weeks, both in the granular phase and the suspended phase (effluent). The microbiome of the washed out biomass was similar but not identical to the microbiome of the granular biomass. Certain taxa (e.g. Flavobacterium spp. and Bdellovibrio spp.) had significantly (p < 0.05) higher relative abundance in the granules compared to the effluent. Fluorescence in situ hybridization images indicated that these taxa were mainly located in the interior of granules and therefore protected from erosion. Other taxa (e.g. Meganema sp. and Zooglea sp.) had significantly lower relative abundance in the granules compared to the effluent, and appeared to be mainly located on the surface of granules and therefore subject to erosion. Despite being washed out, these taxa were among the most abundant members of the granular sludge communities and were likely growing fast in the reactors. The ratio between relative abundance in the granular biomass and in the effluent did not predict temporal variation of the taxa in the reactors, but it did appear to predict the spatial location of the taxa in the granules.

Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.

Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wastewater. In this study, a novel technique involving granular activated carbon (GAC) was developed for rapid aerobic granulation under a low organic loading condition. Laboratory experiments were conducted with two sequencing batch reactors (SBRs) running side by side. One reactor had fine GAC added to the sludge mixture, and the other had no GAC added. A low-strength organic wastewater with a chemical oxygen demand (COD) concentration of only 200 mg/L was used as the influent to the SBRs. The morphology, 2 physical properties, and bacterial community structure of the sludge in the two reactors were characterized and compared throughout the experiments. The results showed that granules could not be formed in the SBR without added GAC. However, complete granulation was achieved in the SBR with GAC addition. Selective discharge of slow settling sludge was also essential to the granulation process. Adding GAC to the seed sludge mixture, together with the selective discharge of small and loose sludge flocs, facilitated the retention and growth of bacterial cells on GAC in attached-growth mode, leading to complete granulation. In addition, the use of GAC produced aerobic granules with strong cores to help maintain the long-term stability of mature granules. With granulation, the solid-liquid separation property of the sludge was greatly improved. Once granules were formed, the granules were quite stable and GAC addition was no longer needed. Therefore, adding GAC is a simple and effective strategy to initiate granule formation for complete sludge granulation in bioreactors treating low-strength organic wastewater.

Laboratory experiments were carried out to investigate the effect of the sludge loading, or the food-to-microorganism (F/M) ratio, on the rate of aerobic granulation and the size of the granules in biological wastewater treatment. Four column batch reactors were used with a similar sludge suspended solids (SS) concentration of around 2000 mg/L. The reactors were fed with a glucose-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.3 to 1.1 g COD/g SS-d. A higher F/M ratio appeared to promote faster formation of larger granules and a lower F/M ratio led to slower 2 formation of smaller granules. Upon complete granulation, the granules became rather stable in size, and the mean diameter of the granules in different reactors increased from 1.2 to 4.5 mm linearly with the F/M ratio applied. Molecular analysis of the sludge did not show the domination of any particular bacterial species during the granulation process. In is apparent that applying different F/M ratios in different granulation stages, e.g., a higher F/M in the early stage and a reduced F/M in the later stage, can be an effective start-up strategy to facilitate rapid granule formation and sustain small and healthy granules in bioreactors.

Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.

Today's ecosystem and its long-term water supplies are also under pressure. Because of our society's rapid urbanization and industrialization, cutting-edge water treatment technologies are needed. In response to the strong consumption and demands that our new generation puts on water, a technology capable of providing reliable, filtered water. Aerobic granulation is the process of converting activated seed sludge into a broad granule with self-immobilizing properties that adsorb and consume polluted and harmful microorganisms. The activated sludge (AS) method is utilized in wastewater treatment facilities (WWTPs) all over the globe to treat urban and industrial wastewater via biological treatment. In 2014, the discovery of AS was commemorated with a centennial year to commemorate its fruitful journey in providing sanitation and mitigating environmental harm. However, because of its huge land footprint, recirculation flows, and complicated process structures involving several process units to remove biomass, nitrogen, and phosphorus from wastewater, it is no longer deemed viable (Sheik et al. 2014). Because of bottlenecks and new advances in sustainable wastewater treatment, the AS method is now facing

The success of the UASB reactor depends largely on the settling properties and stability of the sludge bed which comprises the anaerobic active biomass. The solid-liquid separation behaviour of the sludge bed in 2 UASB reactors (R1 at 35 o C and R2 at 20 o C) fed with primary sewage sludge and sulphate was investigated because this appeared to be a retention timedefining feature of the system. Consequently, the settling rate of the various solids fractions in the sludge was measured in a settleometer to determine if bed expansion or sludge settleability was the capacity-limiting process. It was found that both sludges settled well and at an upflow velocity of up to 1.16 m/h 99% of the total sludge mass was retained. This upflow velocity was 9.1 and 13.7 times higher than the maximum operating upflow velocity of UASB reactors R1 (0.127 m/h) and R2 (0.085 m/h) respectively that caused system failure. Tests were also done to demonstrate the effect of upflow velocity (V up) on the sludge bed expansion. Relative to the settled sludge volume at zero upflow, the R1 sludge expanded 1.8 times at a V up of 0.127 m/h while R2 sludge expanded 2.0 times at a V up 0.085 m/h. From the tests, R1 (35 o C) sludge had a better settleability and expanded less compared to R2 (20 o C) sludge for the same applied upflow velocity. Because in operating R1 and R2, the bed volume was kept constant, the mass of sludge removed from the system correspondingly increased as upflow increased and the bed expanded, causing a reduced sludge age and sludge bed mass to mediate the bioprocesses. It was concluded that the system failure was caused by bed expansion rather than by the sludge settleability.

This study aims to cultivate aerobic granular sludge by using low-strength domestic wastewater. The cultivation was conducted by modifying the seeding condition whereby the seed sludge was mixed with anaerobic granular sludge. Sequencing batch reactor system consisted of two columns were used namely R c as control reactor and R e containing anaerobic granular sludge were utilized to produce aerobic granular sludge. The results indicated that anaerobic granular sludge may be used to induce rapid granulation process, resulting in aerobic granular sludge with more desirable characteristics as compared to the conventional activated sludge. The developed granular sludge exhibited excellent settling velocity (74.6 m/h) and low SVI 30. Total phosphorus removal was also enhanced in reactor R e. Cocci-shaped bacteria were mainly observed on the granular surface along with few of rod-shaped and filamentous bacteria. Moreover, Proteobacteria dominated the microbial population in the aerobic granules. This study demonstrated the possibility to achieve rapid granulation using anaerobic granules and activated sludge as the seeding materials.

Aerobic granulation from floccular sludge is difficult to detect in first stages with the naked eye. This work proposes a combination of multi-way principal components and case-based reasoning to predict the granulation state of a sequencing batch reactor, based solely on the on-line registered profiles of common sensors (i.e. pH, dissolved oxygen and oxidation-reduction potential). The methodology is able to discriminate between two active sludge granularities (floccular and granular). Two different scenarios are presented: one in which both granularities are present, and another scenario for which the granular state is not initially available. Analysis reported pH as the key variable in the transition between both states according to its variation, and that, in general, the granularity of the process can be correctly predicted at the end of the anaerobic phase. This methodology improves process monitoring capabilities during granulation and is an on-line alternative to a microscope analysis before the batch release.

Propionate is a quantitatively important methanogenic intermediate in anaerobic digesters and only limited number of microbes can utilize it under syntrophic association with methanogens. The syntrophic propionate oxidizing bacterias are known to be slow growers due to the low energy yield. Thus, propionate get accumulated frequently in anaerobic digesters and it negatively affect digester performance. In this study, propionate degrading consortia from four different seeding sources were enriched in sequential bath mode in two phases; first adaption phase with 1 g/L of propionate concentration and later, high-strength phase with 3 g/L. From 16s rRNA gene based metagenomics analysis of the former phase, four syntrophic microbial groups, Syntrophaceae, Syntrophomonadaceae, Methanobacterium and Methanosaeta were found to be dominant with complete degradation of propionate. The substrate accelerated microbial shifts were observed at high-strength phase with significant decrease of Syntrophaceae up to 26.9%. Using Response Surface Methodology, pH 6.8-6.9 and temperature 34.5-34.9 o C were found to be optimum growth conditions for the propionate degradation culture. Observed results could be useful to improve degradation efficiencies and obtained enriched culture can be used to recover propionate-accumulated digesters by bio-augmentation.

Aerobic granular sludge has recently become a promising environmental biotechnology process for wastewater treatment. Understanding the aerobic granulation process in all its facets is, therefore, of major importance. This study contributes for a better understanding of the aerobic granulation process, focussing on the kinetic, stoichiometric, and morphological characteristics.

Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3)kg/m(3)d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in fa...

The biodegradability and treatability of a young (3 years old) municipal landfill leachate was evaluated by means of chemical oxygen demand (COD) fractionation tests, based on respirometric techniques. The tests were performed using two different biomasses: one cultivated from the raw leachate (autochthonous biomass) and the other collected from a conventional municipal wastewater treatment plant after its acclimation to leachate (allochthonous biomass). The long term performances of the two biomasses were also studied. The results demonstrated that the amount of biodegradable COD in the leachate was strictly dependent on the biomass that was used to perform the fractionation tests. Using the autochthonous biomass, the amount of biodegradable organic substrate resulted in approximately 75% of the total COD, whereas it was close to 40% in the case of the allochthonous biomass, indicating the capacity of the autochthonous biomass to degrade a higher amount of organic compounds present in the leachate. The autochthonous biomass was characterized by higher biological activity and heterotrophic active fraction (14% vs 7%), whereas the activity of the allochthonous biomass was significantly affected by inhibitory compounds in the leachate, resulting in a lower respiration rate (SOUR = 13 mg O2 gVSS -1 h -1 vs 37 mg O2 gVSS -1 h -1 ). The long-term performance of the autochthonous and allochthonous biomasses indicated that the former was more suitable for the treatment of raw landfill leachate, ensuring higher removal performance towards the organic pollutants.

This study investigated the formation and evolution of biofilm on a fixed cylindrical structure wrapped in geotextile, in a multi-zone wastewater treatment system called BioCAST. The organic, nitrogen and phosphorus loading rates of (OLR) 0.95-1.86 g COD/(m 3 d), (NLR) 0.02-0.08 kg N/(m 3 d), and (PLR) 0.014-0.02 kg P/(m 3 d), were applied. The results demonstrated high removal efficiencies of carbon, nitrogen and phosphorus, reaching 98.9%, 98.3% and 94.1%, respectively, after 250 d of operation. The biofilm biomass showed a fast formation (reaching 54.2 g/L) and maximum phosphorus content of about 7% (dry basis). Biofilm demonstrated the ability to remove phosphorus, and its characteristics correlated with nitrogen and phosphorus removal rates. The geotextile material with filamentous structure causing rapid attachment and formation of biofilm can solve many problems encountered in conventional attachedgrowth wastewater treatment systems such as slow start-up, low reactor biomass content and low capacity to handle high organic loading rates.

In the present work, aerobic granulation of activated sludge was achieved in a sequencing batch airlift reactor (SBAR) fed with acetate as sole carbon source. Aerobic granulation process was followed by the assessment of the biomass kinetic and stoichiometric parameters through respirometric pulse experiments, and by the assessment of aggregates morphology through quantitative image analysis. This study contributes for a better understanding of the aerobic granulation process, introducing tools for aerobic granular biomass characterisation.

Water supply system has an inherently high operational cost. This is significantly due Palm oil mill effluent (POME) from palm oil industries and unmetabolic micropollutants produced by pharmaceutical industries had recently emerged as pollutants with increasing concentration in wastewater, surface water and ground water. Two identical SBR bioreactors without granules (R1) and with granules (R2) were fed with known combinations of POME and acetaminophen, and organic loading rates (OLR) in a range 2.5 to 3.5 g COD L-1 were used. On day 50 the biomass concentration and the sludge volume index (SVI) for both reactors were between 11,160 mg L-1 to 11,430 mg L-1 and 15 mL g SS-1 to 17 mL g SS-1, respectively, indicating fair biomass accumulation in the reactor and good settling properties of granular sludge. Moreover, COD removal was 81% and 67% for R2 and R1, respectively. Phosphate was removed at 28% in R1 while R2 removed a higher phosphorous removal at 55%. The average color removal ...

This research examined novel configuration of SBAR in lab-scale for industrial wastewater treatment. To evaluate COD removal efficiency and granules formation of the novel reactor (R1), SBAR system (R2) was operated under similar conditions during the experimental period. R1 and R2 with working volume of 3.6 and 4.5 L were used to cultivate aerobic granules. Both reactors were operated for 4 hr/cycle. Experiments were done at different OLRs ranging from 0.6 to 4.5 Kg COD/m.d for R1 and from 0.72 to 5.4 Kg COD/m.d for R2. After 150-day operation, large-sized black filamentous granules with diameters of 0.5-2 and 2-11 mm were formed in R1 and R2, respectively. In the second part of the experiment, the removal efficiency of toxic aniline by aerobic granules was investigated. It was found that COD removal efficiency of the novel airlift reactor was over 97 and 94.5 percent using glucose and aniline carbon source, respectively. Keywords— Aerobic granules, Aniline removal efficiency, Sequ...

This work presents the first success at aerobic granulation in a nitrogen deficient system. Two sequencing batch reactors (SBRs) were used to treat nitrogen deficient (the N-fix system) or nitrogen-sufficient (containing NH 4 Cl) synthetic wastewater (acetic acid as the sole carbon source). Granulation was observed in both systems, with particularly large granules (average diameter: 7 mm) grown in the N-fix system. We propose that the unique morphology of nitrogen-fixing granules is a consequence of the response of oxygen-sensitive diazotrophs to elevated oxygen concentrations. Both the nitrogen-fixing and nitrogen-supplemented systems were shown to be capable of removing all of the influent substrate carbon. Excellent biomass settleability characteristics were obtained, with the N-fix system having a final sludge volume index (SVI) of less than 100 mL g À1 and its granules having settling velocities of over 1.4 cm s À1. However, moderately high solids discharges were recorded for both systems, which revealed a potential limitation of granular sludge processes that is not widely discussed in the literature.

This work presents the first success at aerobic granulation in a nitrogen deficient system. Two sequencing batch reactors (SBRs) were used to treat nitrogen deficient (the N-fix system) or nitrogen-sufficient (containing NH4Cl) synthetic wastewater (acetic acid as the ...

Aerobic granular sequencing batch reactors (SBRs) are usually inoculated with activated sludge which implies sometimes long start-up periods and high solids concentrations in the effluent due to the initial wash-out of the inoculum. In this work, the use of aerobic mature granules as inoculum in order to improve the start-up period was tested, but no clear differences were observed compared to a reactor inoculated with activated sludge. The effect of the aeration rate on both physical properties of granules and reactor performance was also studied in a stable aerobic granular SBR. The increase of the aeration flow rate caused the decrease of the average diameter of the granules. This fact enhanced the COD and ammonia consumption rates due to the increase of the DO level and the aerobic fraction of the biomass. However, it provoked a loss of the nitrogen removal efficiency due to the worsening of the denitrification capacity as a consequence of a higher aerobic fraction.

Aerobic granular sequencing batch reactors (SBRs) are usually inoculated with activated sludge which implies sometimes long start-up periods and high solids concentrations in the effluent due to the initial wash-out of the inoculum. In this work, the use of aerobic mature granules as inoculum in order to improve the start-up period was tested, but no clear differences were observed compared to a reactor inoculated with activated sludge. The effect of the aeration rate on both physical properties of granules and reactor performance was also studied in a stable aerobic granular SBR. The increase of the aeration flow rate caused the decrease of the average diameter of the granules. This fact enhanced the COD and ammonia consumption rates due to the increase of the DO level and the aerobic fraction of the biomass. However, it provoked a loss of the nitrogen removal efficiency due to the worsening of the denitrification capacity as a consequence of a higher aerobic fraction.

Fish canning effluents characterized by their salt content, up to 30 g NaCl/L, were treated, previously diluted to desired concentration, in a SBR where aerobic granular sludge was produced. The formation of mature aerobic granules occurred after 75 days of operation with 3.4 mm of diameter, SVI of 30 mL/g VSS and density around 60 g VSS/L-granule. Treated organic loading rates were up to 1.72 kg COD/(m3·d) with fully organic matter depletion. Ammonia nitrogen was removed via nitrification-denitrification up to 40% when nitrogen loading rates were of 0.18 kg N/(m3·d). The presence of salt in the treated effluent did not cause a detrimental effect on the operation of the reactor once the aerobic granules were formed.

Aerobic granular sludge grown in a sequential batch reactor was proposed as an alternative to anaerobic processes for organic matter and nitrogen removal from swine slurry. Aerobic granulation was achieved with this wastewater after few days from start-up. On day 140 of operation, the granular properties were: 5 mm of average diameter, SVI of 32 mL (g VSS)−1 and density around 55 g VSS (Lgranule)−1. Organic matter removal efficiencies up to 87% and nitrogen removal efficiencies up to 70% were achieved during the treatment of organic and nitrogen loading rates (OLR and NLR) of 4.4 kg COD m−3 d−1 and of 0.83 kg N m−3 d−1, respectively. However, nitrogen removal processes were negatively affected when applied OLR was 7.0 kg COD m−3 d−1 and NLR was 1.26 kg N m−3 d−1. The operational cycle of the reactor was modified by reducing the volumetric exchange ratio from 50 to 6% in order to be able to treat the raw slurry without dilution.

Using aerobic granular sludge for wastewater treatment has multiple advantages compared to conventional activated sludge systems, most important being the ability of simultaneous removal of the pollutants responsible for eutrophication: organic load, compounds of nitrogen (NH4+; NO3-) and phosphorus (PO43-). The advantages are currently exploited for developing the next generation of wastewater treatment systems while the identified limitations are approached by experimental and theoretical researches worldwide. The aim of the study consists in evaluating the possibility of predicting the system�s response to different changes in the influent wastewater loadings. The paper presents simulations results backed up by experimental data for pollutants removal efficiencies evaluation for a sequential batch reactor (SBR) with aerobic granular sludge. The mathematical model is based on the activated sludge model no. 3, which was updated by considering the simultaneous biological nitrificati...

Arsanilic acid (ASA) and amprolium hydrochloride (AMP) are widely used as feed additives to control coccidial intestinal parasites and improve feed efficiency, but due to low metabolism most of the drugs are excreted by the animals unchanged and eventually end up in wastewaters. Little is known about the impacts of AMP and ASA on the performance of activate sludge in sequencing batch reactors (SBRs) as well as about their fate in wastewater treatment. In this study, the long-term performance of activated sludge in SBRs exposed to ASA and AMP was investigated. The COD removal and nitrification were not affected when the concentration of ASA or AMP was lower than 20 mg L-1 , but were markedly inhibited at 100 mg L-1 of ASA or AMP. The inhibition to of COD removal was reversible whereas the inhibition to nitrification was irreversible. Phosphate removal was not affected by the continuous exposure to ASA or AMP. ASA and AMP were very resistant to be degraded by the activated sludge in SBRs, and only a small quantity of ASA was degraded to inorganic arsenic (no more than 300 µg L-1) in the form of As (III) and As (V).

In order to evaluate the characteristics of aerobic granular sludge, a sequencing batch reactor, feeding with synthetic wastewater at the organic loading rate of 8 kg COD/m3 d, was employed on the laboratory scale. Granules occurred in the reactor within 1 week after ...

In addition to N load, cold weather nitrification is an important consideration for stabilized performance of biological processes applied to continuous animal production systems. A winter simulation experiment was conducted in the laboratory to evaluate performance of immobilized bacteria for treatment of swine wastewater under cold weather conditions. Bench fluidized reactors (1.2 L) containing 120 mL polyethylene glycol nitrifying pellets (10% v/v) were operated under continuous flow using swine wastewater containing 330 to 450 mg NH 4-N/L, and 140 to 290 mg BOD 5 /L. Water temperature in the reactors was controlled using a refrigerated circulating bath with car antifreeze liquid. Starting at 15 o C and a hydraulic residence time (HRT) of 18 hrs, wastewater process temperatures were decreased 2.5-3 o C every three weeks to a low of 3 o C. Ammonia was completely removed in all of these runs, which precluded calculation of nitrification potential. For this reason, the continuous flow experiment was repeated using higher N loads obtained with HRT of 12 hrs, each temperature run lasting 2 weeks. In addition to continuous flow, batch tests were also done at various process temperatures to determine nitrification rate at cold temperatures with a different method, each batch temperature test lasted 8 hrs and was replicated three times. As expected, the effect of process temperature on nitrification rate was well described by an exponential function. But nitrification activity was not severely affected by the lower temperatures in the experiment (3-5 o C) as previously thought, indicating acclimation of the entrapped nitrifying bacteria to the winter conditions. The temperature coefficient (Q 10) obtained was consistent between continuous flow and batch conditions and averaged 1.41. This means that nitrification rate decreased only by 29% for each 10 o C decrease in water temperature. This decrease is significantly different than the Q 10 of 3 (70% rate decrease per 10 o C) commonly used to predict activity of nitrifying bacteria under cold weather conditions. Thus, the immobilized technology appears well suited for nitrification of high-ammonia livestock wastewater under cold weather conditions.

Aerobic granules were developed in four identical sequencing batch reactors (SBRs) with synthetic wastewater to compare different strategies for the enhancement of granulation. The SBRs were operated by (a) increasing organic loading rate in R1; (b) reducing settling time in R2; (c) extending starvation period in R3; and (d) increasing shear force in R4. The results showed that four operational strategies were able to enhance aerobic granulation successfully in SBR, but that also showed different effect on the granulation process and characteristics of mature aerobic granules. The rapidest granulation was observed by using short settling time (R2) and the granules had higher extracellular polymeric substance (EPS) than other reactors. Extended starvation period (R3) and high shear force (R4) resulted in longer granulation period and the granules with higher integrity and smaller size. Higher organic loading rate (R1) resulted in the granules with larger size and higher K value. The maximum specific COD removal rates (q max) of the granules in all SBRs were at a similar level (0.13-0.16 g COD/h-g VSS) but the granules in R1 and R2 had higher apparent half rate constant (K) of 18 and 16 mg/L, than those in R3 and R4 (2.8 and 3.3 mg/L).

Wastewater treatment methods are energy intensive. Although, activated sludge process is effective in removing organic matter but it consume large amount of energy, particularly in the aeration process. However, wastewater itself is a source of energy, if we capture this energy from wastewater, wastewater treatment might become an energy producer rather than a consumer. Compared to activated sludge process, oxygenic photogranules have potential to treat wastewater without external aeration. In addition it produces algal biomass, which is favorable to use for bio-fuel production. Hence wastewater treatment system with oxygenic photogranules reduces energy consumption and produce energy feed stock. This study was mainly focused on the synthesis of oxygenic photogranules from activated sludge in the presence of sunlight under unagitated condition for 42 days and then conducted the treatment of real municipal wastewater with these oxygenic photogranules. OPGs can remove COD and nitrogenous compounds without external aeration. In the present study, COD and nutrients like nitrogen and phosphate removal efficiencies obtained was 98.5%, 97.09% and 99.18% respectively. The OPG process eliminate the need of external mechanical aeration, which is the most energy intensive part of wastewater treatment processes, and allow the recovery of chemical energy from wastewater in the form of bioenergy feedstock. OPGs are easily harvestable biomass, overcoming the main challenges of algal based wastewater treatment technologies. In this study, efficiency of OPG in treating real municipal wastewater without external aeration was discovered.

An ammonia loading rate of 4.1 kg N-NH 4 + /m 3 d was fully oxidized to nitrate using a nitrifying airlift without biomass carrier. The developed sludge, with a concentration of 12 gVSS/L and high density (100 gVSS/L particle ), allowed particles to be retained with small diameter, having very low concentrations of solids in the effluent (5-10 mg VSS/L). The mean diameter of particles containing the majority of total biomass increased from 220 to 360 m during the operation time. The particle size analysis showed that the percentage of flocs with small diameter (1-3 m) is very high but the biomass content of these flocs is negligible with respect to the total biomass value. The oxygen transfer coefficient (K La ) was measured operating at different air flow rates, obtaining similar values during the overall operational period. The use of activated sludge without support gives high nitrifying rates with an easier fluidization and a lower critical air flow rate than in a biofilm airlift reactor.

Aerobic granulation is a promising technology for the removal of nutrients in wastewater. Since research to date is mainly focused at laboratory scale, a pilot-scale sequencing batch reactor (100 L) was operated to obtain granular sludge in aerobic conditions grown on acetate as organic carbon substrate. Selective pressure created by means of decreasing settling time and increasing organic loading rate (OLR) enhanced the formation of aerobic granular sludge. Granules appeared after 6 days and reached an average diameter around 3.5 mm. The settling velocity value should be higher than 11 m h −1 in order to remove flocculent biomass. The reactor treated OLRs varying between 2.5 and 6.0 g COD L −1 d −1 reaching removal efficiencies around 96%, which demonstrates the high activity and the ability of the system to withstand high OLR. Nevertheless, a rapid increase in the OLR produced a loss of biomass in the reactor due to breakage of the granules.

Aerobic granules to treat wastewater containing methylene blue (MB) were successfully developed in a sequencing batch reactor (SBR) using activated sludge as inoculum. After cultivation for 87 days, stable aerobic granules were obtained with a clearly defined shape and a diameters ranging from 2 to 4 mm. After granulation, the removal efficiencies of MB and chemical oxygen demand (COD) reached 56% and 93%, respectively. Specific MB biodegradation rates followed the Haldane model and the associated kinetic parameters were as follows: V max =184.15 mg L − 1 h − 1 , K s =209.96 mg L − 1 , and K i = 21.23 mg L − 1. The aerobic granules proved to be a feasible and effective way to degrade MB-containing wastewater. Crown

The formation and application of aerobic granules for the treatment of real wastewaters still remains challenging. The high fraction of particulate organic matter (X S ) present in real wastewaters can affect the granulation process. The present study aims at understanding to what extent the presence of X S affects the granule formation and the quality of the treated effluent. A second objective was to evaluate how the operating conditions of an aerobic granular sludge (AGS) reactor must be adapted to overcome the effects of the presence of X S . Two reactors fed with synthetic wastewaters were operated in absence (R1) or presence (R2) of starch as proxy for X S . Different operating conditions were evaluated. Our results indicated that the presence of X S in the wastewater reduces the kinetic of granule formation. After 52 d of operation, the fraction of granules reached only 21% in R2, while in R1 this fraction was of 54%. The granules grown in presence of X S had irregular and filamentous outgrowths in the surface, which affected the settleability of the biomass and therefore the quality of the effluent. An extension of the anaerobic phase in R2 led to the formation of more compact granules with a better settling ability. A high fraction of granules was obtained in both reactors after an increase of the selection pressure for fastsettling biomass, but the quality of the effluent remained low. Operating the reactors in a simultaneous fill-and-draw mode at a low selection pressure for fast-settling biomass showed to be beneficial for substrate removal efficiency and for suppressing filamentous overgrowth. Average removal efficiencies for total COD, soluble COD, ammonium, and phosphate were 87 ± 4%, 95 ± 1%, 92 ± 10%, and 87 ± 12% for R1, and 72 ± 12%, 86 ± 5%, 71 ± 12%, and 77 ± 11% for R2, respectively. Overall our study demonstrates that the operating conditions of AGS reactors must be adapted according to the wastewater composition. When treating effluents that contain X S , the selection pressure should be significantly reduced.

Aerobic granulation is a promising technology for the removal of nutrients in wastewater. Since research to date is mainly focused at laboratory scale, a pilot-scale sequencing batch reactor (100 L) was operated to obtain granular sludge in aerobic conditions grown on acetate as organic carbon substrate. Selective pressure created by means of decreasing settling time and increasing organic loading rate (OLR) enhanced the formation of aerobic granular sludge. Granules appeared after 6 days and reached an average diameter around 3.5 mm. The settling velocity value should be higher than 11 m h −1 in order to remove flocculent biomass. The reactor treated OLRs varying between 2.5 and 6.0 g COD L −1 d −1 reaching removal efficiencies around 96%, which demonstrates the high activity and the ability of the system to withstand high OLR. Nevertheless, a rapid increase in the OLR produced a loss of biomass in the reactor due to breakage of the granules.

Samples from Pagla sewage treatment plant at different treatment stages showed more or less similar temperature (26.9 -27.5 0 C). The pH ranged from 7.2 -7.9. Influent water and primary sedimentation tank water were brownish in colour while sludge water was light black. The lagoon water and treated water were greenish. The ammonium-nitrogen (NH + 4-N) and nitrate-nitrogen (NO -3-N) ranged from 5.24 -61.94 mg/l and 2.55 -11.02 mg/l, respectively. Phosphorus of the water was 1.34 -4.50 mg/l. The suspended solids (SS) ranged from 25.48 -374.69 mg/l. In the present study the amount of SS in the treated water were found to be quite satisfactory. The total bacterial population in Pagla sewage treatments plant was in between 2.9 × 10 4 and 2.5 × 10 6 cfu/ml. The qualitative bacterial spectrum showed a potential consortium of bacteria associated with the treatment plant. Both Gram positive and Gram negative bacteria were present. Gram positive bacteria were represented by the different species of the genus Bacillus, Aureobacterium and Kurthia. Among them Bacillus was the dominant genus. The different species of Bacillus were Bacillus sphaericus, B. fastidiosus, B. circulans and B. pasteurii. Gram negative bacteria were Zoogloea, Yersinia, Citrobacter and Pseudomonas. A good number of microorganisms were found to be associated with the bio-oxidation of the organic compounds of the influent. The Zoogloea along with other free flowing aerobic heterotrophic bacteria like Bacillus, Pseudomonas could play the major role in the sewage treatment.

Aerobic granulation in SBR systems can be an interesting alternative to treat slurry in small livestock facilities where the implementation of anaerobic digestion systems is not a feasible option from an economical point of view. Aerobic granulation technology has been successfully applied to remove both organic matter and nitrogen from swine slurry in lab-scale reactors [1] but it was not yet tested at pilot-scale under variable conditions. The objective of this work was to test the effect of the high variability in the feeding composition of a pilot-scale granular SBR reactor treating swine slurry .

Full Paper Published in: Operation of an aerobic granular pilot scale SBR plant to treat swine slurry: Process Biochemistry 08/2013; DOI:dx.doi.org/10.1016/j.procbio.2013.06.004 A pilot-scale Sequencing Batch Reactor was operated in order to remove organic matter and nutrients from pig slurry with high variable composition. Aerobic granules grew successfully in the reactor in the first weeks of operation. The characteristics of the biomass remained rather stable during the long term operation of the reactor (307 days) despite the high variation in the Organic and Nitrogen Loading Rates, which varied from 1.4 to 6.3 kg CODs/(m3·d) and from 0.5 to 2.5 kg N/(m3·d), respectively. Furthermore the C/N ratio also varied in a wide range (1.9-9.4 g CODs/g N). The reactor had a good biomass retention capacity to select for granular biomass. Hhowever, it was not able to retain the colloidal solids that were fed to the reactor, as consequence, the VSS concentration in the effluent was almost th...

A pilot-scale Sequencing Batch Reactor was operated during 307 days in order to treat swine slurry characterized by its high variable composition: organic and nitrogen applied loading rates and C/N ratio were 1.4-6.3 kg COD s /(m 3 d), 0.5-2.5 kg N/(m 3 d) and 1.9-9.4 g COD s /(g N), respectively. Aerobic granules successfully developed in the reactor and their physical properties remained rather stable despite the feeding composition variability. Organic and ammonia removal efficiency reached 61-73% and 56-77%, respectively, however ammonia was mainly oxidized to nitrite. The reactor had a good biomass retention capacity to select for granular biomass. However, its efficiency to retain the solids present in the feeding was low. Aerobic granulation in SBR systems appears as an interesting alternative to treat slurry in small livestock facilities where the implementation of anaerobic digestion systems is not a feasible option or the removal of nitrogenous compounds is required.

This work presents the first success at aerobic granulation in a nitrogen deficient system. Two sequencing batch reactors (SBRs) were used to treat nitrogen deficient (the N-fix system) or nitrogen-sufficient (containing NH4Cl) synthetic wastewater (acetic acid as the ...

The aim of the research was to evaluate the possibility of using the crude glycerol fraction from biodiesel manufacturing processes for granular sludge production. The experiment was carried out simultaneously in four sequencing batch reactors (SBRs) at different carbon loads: 0.2 AE 0.08, 0.6 AE 0.16, 1.1 AE 0.27, and 1.3 AE 0.35 g COD/g TSS per cycle (COD -chemical oxygen demand, TSS -total suspended solids). Granulation did not occur in the reactor with the lowest organic carbon load. In the remaining reactors small granules began to appear after 25 cycles of reactor operation. In all reactors the efficiency of carbon removal remained at ca. 80%. The highest granular sludge production per cycle was 0.31 AE 0.28 g TSS/L; it was obtained at an organic load of 1.1 AE 0.27 g COD/g TSS per cycle. Most of the introduced COD was removed in the reactors during the first 5 h of aeration; the COD removal rate was correlated with the organic load and varied from 123.12 to 472.76 mg COD per litre and hour.

Filamentous bulking is caused by the excessive growth of filaments over floc formers, and their competition was previously described using kinetic selection. However, recent studies reported that instead of kinetic selection, diffusion limitation inside the flocs may be the crucial factor in microbial selection. To clarify the roles of these factors in explaining filamentous bulking, a new conceptual qualitative framework was developed in this study. We hypothesize that the growth rates of filaments and floc formers are affected by the combination of kinetic selection and substrate diffusion limitation. Three different regions (bulking, transitional, and non-bulking region) based on substrate concentration are suggested. In the bulking region, kinetic selection controls the growth rate process and favors filaments. In the non-bulking region, kinetic selection also is controlling, and favors the growth of floc formers. However, in the transitional region, substrate diffusion limitation, determined by the floc size, plays an important role in causing bulking. To test this framework, sequencing batch reactors (SBRs) were operated with influent COD of 100, 300, 600 and 1000 mg/L, and the sludge settleability was measured at various floc size distributions developed using different mixing strengths. The experimental data in the bulking and transitional regions supported the proposed framework.