Granular Sludge Technology Research Articles

Full scale performance of the aerobic granular sludge process for sewage treatment

Recently, aerobic granular sludge technology has been scaled-up and implemented for industrial and municipal wastewater treatment under the trade name Nereda®. With full-scale references for industrial treatment application since 2006 and domestic sewage since 2009 only limited operating data have been presented in scientific literature so far. In this study performance, granulation and design considerations of an aerobic granular sludge plant on domestic wastewater at the WWTP Garmerwolde, the Netherlands were analysed. After a start-up period of approximately 5 months, a robust and stable granule bed (>8 g L−1) was formed and could be maintained thereafter, with a sludge volume index after 5 min settling of 45 mL g−1. The granular sludge consisted for more than 80% of granules larger than 0.2 mm and more than 60% larger than 1 mm. Effluent requirements (7 mg N L−1 and 1 mg P L−1) were easily met during summer and winter. Maximum volumetric conversion rates for nitrogen and phosphorus were respectively 0.17 and 0.24 kg (m3 d)−1. The energy usage was 13.9 kWh (PE150·year)−1 which is 58–63 % lower than the average conventional activated sludge treatment plant in the Netherlands. Finally, this study demonstrated that aerobic granular sludge technology can effectively be implemented for the treatment of domestic wastewater.

Comparing aerobic granular sludge and flocculent sequencing batch reactor technologies for textile wastewater treatment

Textile wastewaters are rated among the most polluting in all industrial sectors, including high organic loads and dyes that are generally resistant to aerobic biotreatment. Alternative, staged anaerobic/aerobic regimes have been tested, with clear success in the biodecolorization of the widely used azo dyes. The novel aerobic granular sludge (AGS) technology has excellent potential in this context, due to the anoxic/anaerobic zones within granules and their increased tolerance to toxicity. In this study the performance of anaerobic/aerobic, flocculent and AGS sequencing batch reactors (SBR) was compared in the treatment of a simulated textile wastewater. Similar color removal yields (75–80%) of an azo dye were attained in both systems but with higher anaerobic and overall COD removal yields in the AGS SBR, thus demonstrating the latter's good potential. Comparison of the toxicity of samples collected from both SBR using yeast-based assays highlighted the better performance of the AGS SBR as compared with the flocculent SBR, with respect to detoxification potential.

Effect of sequencing batch cycle strategy on the treatment of a simulated textile wastewater with aerobic granular sludge

Aerobic granular sludge was successfully developed on a simulated textile effluent with an added azo dye, on a non-tubular sequential batch reactor (SBR), with better granulation results than in a dye-free control SBR fed with the same base medium. The overall performance of the treatment was very good, with high color and chemical oxygen demand (COD) removal yields (up to 85% and 80%, respectively). Operation under two sequencing batch cycle strategies, i.e., with a single anaerobic/aerobic reaction phase or under intermittent aeration, showed that the latter generally improved the treatment performance. Under intermittent aeration, biomass accumulation was induced, with faster settling aggregates, leading to a higher COD removal yield. Although a lower decolorization rate was observed in the first 30min of anaerobic reaction, as compared to the single phase strategy, the overall color removal remained high. This work demonstrates the applicability of the new aerobic granular sludge technology for the treatment of textile effluents.

Aerobic granular sludge technology and nitrogen removal for domestic wastewater treatment.

This study evaluated aerobic granulation and nitrogen removal via assimilation, nitrification, and denitrification of a system fed with real domestic wastewater. The granulation process was complete after 160 days of operation. The mature granules had an almost spherical structure, an average size of 473.0 μm, and a good settling ability (SVI30 of 75.6 mL g⁻¹). Ammonium assimilation for cell growth varied between 3.5 and 64.6% during reactor start-up. After granule formation, assimilation accounted for less than 5% and nitrogen was mainly removed by partial nitrification up to nitrite, followed by denitrification via nitrite. Average efficiencies of 86.6% for nitrification, 59.5% for denitrification, and 60.5% for total nitrogen were obtained in this period. The assimilation ability of the mature granules grown on domestic wastewater was lower than the commonly reported results obtained for synthetic granules.

Zastosowanie oraz perspektywy rozwoju technologii granulacji tlenowej w oczyszczaniu ścieków

Recently an extensive studies have been carried out on aerobic granular sludge technology in both laboratory and technical scale. Aerobic granules are compact, spherical microbial consortia created by a spontaneous immobilization. Amongst their advantages are a very good settling ability, long biomass age and simultaneous pollutant removal in the granule structure that enables full biological treatment of wastewater in a single reactor. This review outlines up-to-date information on granule formation, morphology, microbial structure as well as on the applications of aerobic granular sludge technology for wastewater treatment including the treatment of high-nitrogen wastewater with a low COD/N ratio and wastewater of high toxicity. Aerobic granular sludge technology is presented as both environmentally and financially attractive alternative to wastewater treatment systems based on activated sludge or biofilm. This paper also reports on already existing full-scale installations in world and seeks to explore the potential of aerobic granular sludge within the Polish conditions.

Aerobic granules formation and simultaneous nitrogen and phosphorus removal treating high strength ammonia wastewater in sequencing batch reactor

The objective of this study was to evaluate aerobic granules formation and simultaneous nitrogen and phosphorus removal treating high strength ammonia wastewater in sequencing batch reactor (SBR). After successful aerobic granulation, mixed liquor suspended solids (MLSS) concentrations of the SBR increased from 3.11 to 14.52g/L, while sludge volume index (SVI) values decreased from 144.61 to 30.32mL/g. Protein (PN) and polysaccharide (PS) concentrations increased from 60.2 and 12.5mg/L to 101.1 and 15.8mg/L, respectively. Simultaneous nitrogen and phosphorus removal was enhanced by altering the influent chemical oxygen demand/nitrogen (COD/N) ratio. At COD/N ratio of 9, total nitrogen (TN) and total phosphorus (TP) removal efficiencies were up to 89.8% and 77.5%, respectively. Three-dimensional excitation–emission matrix (3D-EEM) spectroscopy showed that the chemical compositions of sludge EPS were changed during granulation process. The results could provide useful information to promote nitrogen and phosphorus removal using aerobic granular sludge technology.

Physicochemical optimization of granular sludge in rubber industrial wastewater

Aerobic granular sludge (AGS) technology is a novel and promising development in the field of biological wastewater treatment where it develops granulated sludge without any additional of supporting carrier material. Self-immobilized granular sludge has high settling velocity and contribute to high efficiency of solid-liquid separation in wastewater. Current problem of rubber manufacturing wastewater are low solid:liquid separation ratio and therefore, this study aims to incorporate aerobic granulation technology into rubber industry treatment in order to improve the problems. Aerobic granules were developed in two identical sequencing batch reactors (SBRs) with different strategies for the enhancement of granulation. The characteristic of the microbial granular sludge was monitored throughout the study period and the results demonstrated good removal of COD and ammonia of 90% and 85%, respectively at the end of the study. Findings of this study show that granular sludge could be developed in rubber industry wastewater and is capable in treating the wastewater.

Analysis of the characteristics of short-cut nitrifying granular sludge and pollutant removal processes in a sequencing batch reactor

Aerobic granular sludge is a new type of microbe auto-immobilization technology; in this paper, short-cut nitrification and denitrification were effectively combined with the granular sludge technology. Simultaneous nitrification and denitrification granules were developed in a sequencing batch reactor (SBR) using synthetic wastewater with a high concentration of ammonia nitrogen at 25 °C with a dissolved oxygen concentration above 2.0 mg/L and a 15 days sludge retention time. The characteristics of the sludge and the removal efficiency were studied, and the removal mechanisms of the pollutants and the process of short-cut nitrification were analyzed. The average granule diameter of the granular sludge was 704.0 μm. The removal rates of pollutants and the accumulation rate of nitrite in the SBR were studied. During treatment of wastewater with a high concentration of ammonia nitrogen, simultaneous nitrification, and denitrification and the stripping process could contribute to the removal of total nitrogen. The high pH value, the high concentration of free ammonia, and the delamination of granular sludge were the main factors contributing to the short-cut nitrification property of granular sludge in the reaction process.

Long-term impact of anaerobic reaction time on the performance and granular characteristics of granular denitrifying biological phosphorus removal systems

Removal of nitrogen and phosphorus (P) from wastewater is successfully and widely practiced in systems employing both granular sludge technology and enhanced biological P removal (EBPR) processes; however, the key parameter, anaerobic reaction time (AnRT), has not been thoroughly investigated. Successful EBPR is highly dependent on an appropriate AnRT, which induces carbon and polyphosphate metabolism by phosphorus accumulating organisms (PAOs). Therefore, the long-term impact of AnRT on denitrifying P removal performance and granular characteristics was investigated in three identical granular sludge sequencing batch reactors with AnRTs of 90 (R1), 120 (R2) and 150 min (R3). The microbial community structures and anaerobic stoichiometric parameters related to various AnRTs were monitored over time. Free nitrite acid (FNA) accumulation (e.g., 0.0008–0.0016 mg HNO2–N/L) occurred frequently owing to incomplete denitrification in the adaptation period, especially in R3, which influenced the anaerobic/anoxic intracellular intermediate metabolites and activities of intracellular enzymes negatively, resulting in lower levels of poly-P and reduced activity of polyphosphate kinase. As a result, the Accumulibacter-PAOs population decreased from 51 ± 2.5% to 43 ± 2.1% when AnRT was extended from 90 to 150 min, leading to decreased denitrifying P removal performance. Additionally, frequent exposure of microorganisms to the FNA accumulation and anaerobic endogenous conditions in excess AnRT cases (e.g., 150 min) stimulated increased extracellular polymeric substances (EPS) production by microorganisms, resulting in enhanced granular formation and larger granules (size of 0.6–1.2 mm), but decreasing anaerobic PHA synthesis and glycogen hydrolysis. Phosphorus removal capacity was mediated to some extent by EPS adsorption in granular sludge systems that possessed more EPS, longer AnRT and relatively higher GAOs.

The stability of aerobic granular sludge under 4-chloroaniline shock in a sequential air-lift bioreactor (SABR)

The aerobic granular sludge technology has a great potential in treatment of municipal wastewater and industrial wastewater containing toxic non-degradable pollutants. However, the formation and structural stability of aerobic granular sludge is susceptible to toxic shock. In the study, the effect of 4-chloroaniline (4-ClA) as a common toxic pollutant on the granular structure and performance was investigated, and the mechanism was revealed to provide more information on 4-ClA degradation with aerobic granular sludge process. The results showed that a 4-ClA shock at influent 200 mg L(-1) could cause the disintegration of aerobic granular sludge and decrease of the pollutant removal performance. The analysis of extracellular polymeric substances (EPS) within the mature and disintegrated granular sludge showed that the decrease of protein content in EPS, especially the components like Amide I 3-turn helix and β-sheet structures and aspartate, was not good for the stability of aerobic granular sludge. The microbial community results demonstrated that the disappearance of dominant bacteria like Kineosphaera limosa or appearance like Acinetobacter, might contribute to the reduction of EPS and disintegration of aerobic granular sludge.

Advancements in the application of aerobic granular biomass technology for sustainable treatment of wastewater

Aerobic granular sludge technology can be regarded as the future standard for industrial and municipal wastewater treatment. As a consequence, a growing number of institutes and universities focus their scientific research on this new technology. Recently, after extensive Dutch research and development effort, an aerobic granular biomass technology has become available to the market. Full scale installations for both industrial and municipal applications are already on stream, under construction or in design. The technology is distinguished by the name ‘Nereda®’ and based on the specific characteristics of aerobic granular sludge. It can be considered as the first mature aerobic granular sludge technology applied at full scale. It improves on traditional activated sludge systems by a significantly lower use of energy and chemicals, its compactness and its favorable capital and operational costs.

Biochemical conversions and biomass morphology in a long-term operated SBR with aerobic granular sludge

The experiment was carried on for about one year (995 cycles) in a constantly aerated, column sequencing batch reactor with granular sludge fed with a mixture of anaerobic sludge digester supernatant and synthetic wastewater. The research proved the usefulness of granular sludge technology for the removal of ammonium from highly concentrated ammonium streams with an unfavorable chemical oxygen demand (COD)/nitrogen (N) ratio. In the period of stable reactor performance, all ammonium in the influent was oxidized and nitrification–denitrification via nitrite occurred with an efficiency of 26%. The calculated carbon (COD) and N balances showed how the substances were distributed in the reactor under the conditions of low organic accessibility and high N load. Despite the low organic availability, intracellular storage occurred and the yield of polyhybroksybutyrate (PHB) was YPHB = 0.206g COD/g COD. Detailed characteristics of the biomass operating under conditions of low COD/N was performed and showed that the wastewater composition and reactor operational parameters promoted the growth of dense, smooth granules with an average fractal dimension of 2.75 ± 0.15, characterized by settling velocity and equivalent diameter of 11.6±7.9 mm/s and 2.13±1.29 mm, respectively. The presented results can be used for the modeling of reactors with granular sludge for treating wastewater with the very low COD/N ratio.

Correlation analysis of major control factors for the formation and stabilization of aerobic granule

In recent years, aerobic granular sludge technology has demonstrated significant advantages in areas such as the sludge-water separation, residual sludge minimization, simultaneous biological nitrogen and phosphorus removal, and toxic organic compounds degradation in biological wastewater treatment. However, the critical control factors and their relation during sludge granulation have not been revealed indeed, and the stability of aerobic granular sludge is still not good. The Gray's correlation analysis was used to investigate the relationship of aerobic granular characteristics and control factors in the study. Results showed that the organic loading rate, hydraulic shear stress, and sludge settling time were the major factors affecting the aerobic sludge granulation, and the associated regulating strategy was important for the stabilization of granular sludge system. Based on above results, the mechanism of aerobic sludge granulation was proposed, and it was expected to favor the application of aerobic granular sludge technology.

Measuring biomass specific ammonium, nitrite and phosphate uptake rates in aerobic granular sludge

Aerobic granular sludge (AGS) technology offers the possibility to remove organic carbon, nitrogen and phosphorus in a single reactor system. The granular structure is stratified in such a way that both aerobic and anaerobic/anoxic layers are present. Since most of the biological processes in AGS systems occur simultaneously, the measurement and estimation of the capacity of specific conversions is complicated compared to suspended biomass. The determination of the activities of different functional groups in aerobic granular sludge allows for identification of the potential metabolic capacity of the sludge and aids to analyze bioreactor performance. It allows for comparison of different sludges and enables improved understanding of the interaction and competition between different metabolic groups of microorganisms. The most appropriate experimental conditions and methods to determine specific ammonium, nitrite and phosphate uptake rates under normal operation of AGS reactors were evaluated and described in this study. Extra biomass characterization experiments determining the maximum uptake rate of these compounds on optimized conditions were performed as well to see how much spare capacity was available. The methodologies proposed may serve as an experimental frame of reference for investigating the metabolic capacities of microbial functional groups in biofilm processes.

Temperature and salt effects on settling velocity in granular sludge technology

Settling velocity is a crucial parameter in granular sludge technology. In this study the effects of temperature and salt concentrations on settling velocities of granular sludge particles were evaluated. A two-fold slower settling velocity for the same granules where observed when the temperature of water decreases from 40 °C to 5 °C. Settling velocities also decreased with increasing salt concentrations. Experiments showed that when granules were not pre-incubated in a solution with increased salt concentration, they initially floated. The time dependent increase in mass and hence in settling speed of a granule due to salt diffusion into the granule was dependent on the granule diameter. The time needed for full salt equilibrium with the bulk liquid took 1 min for small particles from the top of the sludge bed and up to 30 min for big granules from the bottom of the sludge bed. These results suggest that temperature and salt concentration are important parameters to consider in the design, start-up and operation of granular sludge reactors and monitoring of these parameters will aid in a better control of the sludge management in anaerobic and aerobic granular sludge technology. The observations also give an explanation for previous reports which were suggesting that a start-up of granular sludge reactors is more difficult at low temperatures.

Dewaterability of Aerobic Granular Sludge

Dewatering characteristics of aerobic granular sludge, activated sludge and sludge which mixed flocculant was studied. It was shown that the specific resistance of aerobic granular sludge is lower than activated sludge and sludge with mixed flocculant was in the range of 1.07~1.80×109 S2/g, and it increased with the increase of diameters of the granules. The water ratio of aerobic granular sludge by pressure filtrate dehydration was decreased to 83.5~86.1%, activated sludge and sludge which mixed flocculant were 94.2% and 91.4%, respectively. The structural characteristics, distribution features of extracellular polymeric substances and PN/PS values of aerobic granular sludge were important factors of its excellent dewaterability. Aerobic granular sludge technology was regarded as one of the promising biotechnologies in sludge treatment.

Reducing the startup time of aerobic granular sludge reactors through seeding floccular sludge with crushed aerobic granules

One of the main challenging issues for the aerobic granular sludge technology is the long startup time when dealing with real wastewaters. This study presents a novel strategy to reduce the time required for granulation while ensuring a high level of nutrient removal. This new approach consists of seeding the reactor with a mixture of crushed aerobic granules and floccular sludge. The effectiveness of the strategy was demonstrated using abattoir wastewater, containing nitrogen and phosphorus at approximately 250 mgN/L and 30 mgP/L, respectively. Seven different mixtures of crushed granules and floccular sludge at granular sludge fractions (w/w in dry mass) of 0%, 5%, 10%, 15%, 25%, 30% and 50% were used to start eight granulation processes. The granulation time (defined as the time when the 10th percentile bacterial aggregate size is larger than 200 μm) displayed a strong dependency on the fraction of granular sludge. The shortest granulation time of 18 days was obtained with 50% crushed granules, in comparison with 133 days with 5% crushed granules. Full granulation was not achieved in the two trials without seeding with crushed granules. In contrast to the 100% floccular sludge cases, where a substantial loss of biomass occurred during granulation, the biomass concentration in all other trails did not decrease during granulation. This allowed that good nitrogen removal was maintained in all the reactors during the granulation process. However, enhanced biological phosphorus removal was achieved in only one of the eight trials. This was likely due to the temporary accumulation of nitrite, a strong inhibitor of polyphosphate accumulating organisms.

Application of Granular Sludge Membrane Bioreactor in the Treatment of Wastewater

The technology of aerobic granular sludge has the advantages of high biomass content, high biomass retention, strong ability to withstand shock-loadings, and capacity of simultaneous nitrogen and phosphorus removal; it is a promising option for efficient wastewater treatment. Membrane bioreactor (MBR) is a novel biotechnology for wastewater treatment, and has the potential advantages of low excess sludge production, small land requirement, and high loading rate capability. Thus, the combination of aerobic granular sludge technology and membrane bioreactor was proposed and became the research hotspot and frontier in the field of wastewater treatment. The background, operation characteristics and problems of the combination of the two technologies are discussed and summarized in this study. The latest research achievements and prospects are also presented.

Simultaneous Nitrogen and Phosphorus Removal from High-Strength Industrial Wastewater Using Aerobic Granular Sludge

Aerobic granular sludge technology was applied to the simultaneous nitrogen and phosphorus removal from livestock wastewater that contains high concentrations of nitrogen and phosphorus (TN: 650 mg∕L ; TP: 125 mg∕L ). A lab-scale sequencing batch reactor was operated in an alternating anaerobic/oxic/anoxic denitrification mode. Granular sludge was first formed using synthetic wastewater. When livestock wastewater was diluted with tap water, the shape and settleability of aerobic granular sludge were maintained even though livestock wastewater contained suspended solids. Simultaneous nitrification, denitrification, and phosphate uptake were observed under an aerobic condition. However, when nondiluted livestock wastewater was used, the diameter of granular sludge and the denitrification efficiency under an oxic condition decreased. When the concentrations of nitrogen and phosphorus in wastewater increased, hydraulic retention time (HRT) increased resulting in a decrease in selection pressure for granular s...

Organics and nitrogen removal and sludge stability in aerobic granular sludge membrane bioreactor

Novel aerobic granular sludge membrane bioreactor (GMBR) was established by combining aerobic granular sludge technology with membrane bioreactor (MBR). GMBR showed good organics removal and simultaneous nitrification and denitrification (SND) performances for synthesized wastewater. When influent total organic carbon (TOC) was 56.8-132.6 mg/L, the TOC removal of GMBR was 84.7-91.9%. When influent ammonia nitrogen was 28.1-38.4 mg/L, the ammonia nitrogen removal was 85.4-99.7%, and the total nitrogen removal was 41.7-78.4%. Moreover, batch experiments of sludge with different particle size demonstrated that: (1) flocculent sludge under aerobic condition almost have no denitrification capacity, (2) SND capacity was caused by the granular sludge, and (3) the denitrification rate and total nitrogen removal efficiency were enhanced with the increased particle size. In addition, study on the sludge morphology stability in GMBR showed that, although some granular sludge larger than 0.9 mm disaggregated at the beginning of operation, the granular sludge was able to maintain the stability of its granular morphology, and at the end of operation, the amount of granular sludge (larger than 0.18 mm) stabilized in GMBR was more than 56-62% of the total sludge concentration. The partial disaggregation of large granules is closely associated with the change of operating mode from sequencing batch reactor (SBR) system to MBR system.