activated sludge Articles
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Effect of extended feeding time on aerobic granulation in SBR
Two different feeding lengths were applied to control the granule size. It was found that the size of granules was considerably controlled in R2 (60 min for feeding). However, the settleability in R2 was not as good as that in R1 (12 min for feeding). However, this approach of controlling the granule size also loosens the structure concerning on the difference between SVI5 and SVI30, which might ...
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Application of nitrifying granules to improvement of nitrification activity in activated sludge process
Nitrifying granules were used to improve nitrification performance of activated sludge process under high organic load. After inoculation of nitrifying granules, nitrification activity immediately increased, and kept for at least 70 days. Fluorescence in situ hybridisation analysis confirmed that nitrifying bacteria were retained in the granules even though nitrifying granules had been served in ...
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Modeling and verification of selective sludge discharge as the controlling factor for aerobic granulation
Mathematical simulation and laboratory experiments were conducted to investigate the controlling factor for aerobic sludge granulation. A model was used to describe the biomass dynamics during the granulation process. The simulation results indicate that the selective discharge of small and loose sludge flocs is the key controlling factor for granulation. In the experimental studies, tests were ...
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Granularity determination of activated sludge through on-line profiles by means of case-based reasoning
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 ...
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Selection pressure theory for aerobic granulation – an overview
Aerobic granulation technology is an improvement over conventional activated sludge process, where cell-to-cell interactions lead to the formation of stable granules with excellent settleability. Selection pressures are the factors that can strongly influence the formation and growth of aerobic granules. Settling time and the volume exchange ratio (VER) will decide how long the bioparticles ...
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Strength characteristics of aerobic granular sludge
Aerobic granular sludge has a number of advantages over conventional activated sludge flocs, such as cohesive and strong matrix, fast settling characteristic, high biomass retention and ability to withstand high organic loadings, all aspects leading towards a compact reactor system. Still there are very few studies on the strength of aerobic granules. A procedure that has been used previously for ...
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Enhanced membrane bioreactor process without chemical cleaning
In membrane bioreactors (MBR) for wastewater treatment, the separation of activated sludge and treated water takes place by membrane filtration. Due to the small footprint and superior effluent quality, the number of membrane bioreactors used in wastewater treatment is rapidly increasing. A major challenge in this process is the fouling of the membranes which results in permeability decrease and ...
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Determine the operational boundary of a pilot-scale single-stage partial nitritation/anammox system with granular sludge
The partial nitritation/anammox (PN/A) process has been applied to ammonium-rich wastewater treatment, but the operational boundary has not been well determined for long-term stability. This pilot-scale study was targeted at a single-stage PN/A process using a sequencing batch reactor (SBR) (volume: 53 m3) and granulated activated sludge. The maximum nitrogen removal rate reached 0.83 kg ...
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Aerobic sludge granulation: state-of-the-art
Recently, the research focused on the development and operation of aerobic granular biomass has increased in interest, due to the advantages of this option as compared to the conventional activated sludge systems traditionally used for the biological treatment of wastewater. The aerobic granular sludge is produced in Sequential Batch Reactors (SBR) where a large amount of biomass is accumulated ...
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Strong selection pressures impact the capacity of flocculating activated sludge bacteria to granulate
The capacity of activated sludge (AS) microbial populations to form dense granules offers the potential to establish efficiently settleable biomass. This has the potential to circumvent problems around ineffective solids–liquid separation and sensitivity to variable chemical oxygen demand (COD) loads. Although a number of studies have evaluated aerobic laboratory granulation reactors as ...
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Aerobic granule formation in a sequencing batch reactor treating newsprint effluent under low phosphate conditions
Pulp and paper mills are under increasing pressure to minimize the discharge of phosphate to receiving waters. We investigated the operation of two laboratory sequencing batch reactors (SBR) under low phosphate conditions over a period of eight months. Performance characteristics in terms of COD and TSS removal were similar to the full-scale mill activated sludge operation, but the floc density ...
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High-rate nitrification of electronic industry wastewater by using nitrifying granules
Nitrifying granules have a high sedimentation property and an ability to maintain a large amount of nitrifying bacteria in a reaction tank. Our group has examined the formation process of nitrifying granules and achieved high-rate nitrification for an inorganic synthetic wastewater using these granules. In this research, a pilot-scale test plant with an 850-liter reaction tank was assembled ...
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Ecology and performance of aerobic granular sludge treating high-saline municipal wastewater
The successful development of aerobic granular sludge (AGS) for secondary wastewater treatment has been linked to a dedicated anaerobic feeding phase, which enables key microbes such as poly-phosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms to gain a competitive advantage over floc-forming organisms. The application of AGS to treat high-saline sewage and its ...
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Formation and characteristics of nitritation granules cultivated in sequencing batch reactor by stepwise increase of N/C ratio
The cultivation of nitritation granules in sequencing batch reactor (SBR) by seeding conventional floccular activated sludge was investigated using ethanol-based synthetic wastewater. Reducing settling time offers selection pressure for aerobic granulation, and stepwise increase of influent N/C ratio can help to selectively enrich ammonia oxidizing bacteria (AOB) in aerobic granules. The ...
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Considering microbial and aggregate heterogeneity in biofilm reactor models: how far do we need to go?
A model describing a given system should be as simple as possible – but not simpler. The appropriate level of complexity depends both on the type of system and on the intended use of the model. This paper addresses the critical question of which purposes justify increased complexity of biofilm (reactor) models. Additional model features compared to conventional models considered are: (1) the ...
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Promotion of partial nitritation-anammox process by improving granule proportion
For enhancing the partial nitritation-anammox (PN/A) process, the effects of granule fraction on system performance were investigated in this study. Two sequencing batch reactors (SBRs) were inoculated with PN/A biomass with a floc mass fraction of 53%. In SBR1, when the nitrogen removal rate (NRR) was stable, flocculent sludge was gradually discharged from the reactor using a screen, and the ...
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Effects of oxygen concentration on the nitrifying activity of an aerobic hybrid granular sludge reactor
The aim of the work was to quantify the influence of the simultaneous presence of flocs and granules in the nitrifying activity in a sequencing batch airlift reactor (SBAR). The nitrification rate and oxygen limitation of flocs, granules and hybrid sludge was investigated using respirometric assays at different dissolved oxygen concentrations. The spatial distribution of Ammonium Oxidizing ...
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Biomass aggregation influences NaN3 short-term effects on anammox bacteria activity
The main bottleneck to maintain the long-term stability of the partial nitritation-anammox processes, especially those operated at low temperatures and nitrogen concentrations, is the undesirable development of nitrite oxidizing bacteria (NOB). When this occurs, the punctual addition of compounds with the capacity to specifically inhibit NOB without affecting the process efficiency might be ...
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