scholarly journals Enhanced settling in activated sludge: design and operation considerations

2018 ◽  
Vol 78 (2) ◽  
pp. 247-258 ◽  
Author(s):  
Glen T. Daigger ◽  
Eric Redmond ◽  
Leon Downing
Keyword(s):  
Activated Sludge ◽  
Quality Criteria ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
Water Quality Criteria ◽  
Subsequent Removal ◽  
Solids Concentration ◽  
Activated Sludge Processes ◽  
Sludge Settleability ◽  
Activated Sludge Systems

Abstract Settling of activated sludge particles has long been the key to successfully achieving secondary treatment. While soluble products can be converted to particulate components via microbial reactions in the activated sludge process, it is the subsequent removal of these particulate components that is the key to achieving ultimate water quality criteria. An understanding of the operating parameters for selecting good settling activated sludge particles was first documented in the 1970s and 1980s. An understanding of the growth pressures that can be imposed on filamentous organisms, and the impacts of selector zones in general, allowed the design and operation of activated sludge processes to routinely achieve good sludge settleability. More recently, research has identified what could be the next evolution in flocculant growth, with the growing interest in aerobic granular sludge. Aerobic granular sludge is purported to provide superior settling properties, and many of the growth pressures identified for aerobic granular sludge are also present in activated sludge systems. These enhanced settling sludge systems are gaining significant interest, but the factors leading to enhanced sludge settleability could be present in historical and existing systems. Three facilities were evaluated that exhibited enhanced settleability (i.e. sludge volume indices of less than 70 mL/g the majority of the time) to determine how these enhanced settling sludges compare to typical settling curves from the literature. The enhanced settling sludge facilities exhibit key differences related to surface overflow rate, return activated sludge (RAS) pumping requirements, and sensitivity to solids concentration that are critical for developing effective settling designs for enhanced settling sludge facilities. As more facilities aim to achieve enhanced settling sludge for intensification of infrastructure, it will be important to carefully consider historic settling curves and to develop site-specific settling criteria when possible.

Textile wastewater treatment: Aerobic granular sludge vs activated sludge systems

2014 ◽  
Vol 54 ◽  
pp. 337-346 ◽  
Author(s):  
Adriana Maria Lotito ◽  
Marco De Sanctis ◽  
Claudio Di Iaconi ◽  
Giovanni Bergna
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Granular Sludge ◽  
Textile Wastewater ◽  
Aerobic Granular Sludge ◽  
Textile Wastewater Treatment ◽  
Activated Sludge Systems

scholarly journals Removal of bacterial and viral indicator organisms in full-scale aerobic granular sludge and conventional activated sludge systems

2020 ◽  
Vol 6 ◽  
pp. 100040 ◽  
Author(s):  
Mary Luz Barrios-Hernández ◽  
Mario Pronk ◽  
Hector Garcia ◽  
Arne Boersma ◽  
Damir Brdjanovic ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Granular Sludge ◽  
Full Scale ◽  
Aerobic Granular Sludge ◽  
Indicator Organisms ◽  
Conventional Activated Sludge ◽  
Activated Sludge Systems

scholarly journals Recovery of Biodegradable Bioplastics from Different Activated Sludge Processes during Wastewater Treatment

2021 ◽  
pp. 145-162
Author(s):  
S. Ghosh
Keyword(s):  
Tissue Engineering ◽  
Wastewater Treatment ◽  
Environmental Factors ◽  
Activated Sludge ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
Activated Sludge Process ◽  
Structure Synthesis ◽  
Simultaneous Process ◽  
Activated Sludge Processes

To overcome the environmental hazards of petroleum based plastics, synthesis and use of microbial bioplastics became popular. Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers having plastic like properties mainly used in tissue engineering and packaging. Bacteria can produce bioplastics in carbon abundance. Activated sludge process is a simultaneous process for treating wastewater and producing PHAs. Wastewaters are treated by using mixed sludge, aerobic granular sludge and chemically treated sludge which provided more than 40% PHA yield. This chapter describes the PHA structure, synthesis pathways, types of wastewaters and activated sludge processes used with reactor parameters and environmental factors effecting PHA productions.

New approaches to minimize excess sludge in activated sludge systems

2001 ◽  
Vol 44 (10) ◽  
pp. 203-208 ◽  
Author(s):  
G.-H. Chen ◽  
S. Saby ◽  
M. Djafer ◽  
H.-K. Mo
Keyword(s):  
Activated Sludge ◽  
Activated Sludge Process ◽  
Conventional System ◽  
Excess Sludge ◽  
Active Sludge ◽  
New Approaches ◽  
Conventional Activated Sludge ◽  
Sludge Settleability ◽  
Activated Sludge Systems ◽  
Sludge Production

This paper presents three new approaches to reduce excess sludge production in activated sludge systems: 1) modification of conventional activated sludge process with insertion of a sludge holding tank in the sludge return line; 2) chlorination of excess sludge so as to minimize excess sludge production; and 3) utilization of a metabolic uncoupler, 3, 3′, 4′, 5-Tetrachlorosalicylanilide (TCS) to maximize futile activity of sludge microorganisms thereby leading to a reduction of sludge growth. Pilot study was carried out to evaluate this modified activated sludge process (OSA). It has been confirmed that the OSA process is effective in reducing excess sludge; particularly when the ORP level in the sludge holding tank was kept at -250 mV, more than 50% of the excess sludge was reduced. This process can maintain the effluent quality and even perform with a better sludge settleability than a conventional system. Experimental work on the second approach showed that chlorination treatment of excess sludge at a chlorine dose of 0.066 g Cl2/g MLSS reduced the excess sludge by 60%, while concentration of THMS was found below 200 ppb in the treated sludge. However, such sludge chlorination treatment sacrificed sludge settleability. Thus, it is not feasible to introduce the chlorination step to a conventional system. The third approach confirmed that addition of TCS could reduce sludge growth effectively if the TCS concentration is greater than 0.4 ppm. A 0.8-ppm concentration of TCS actually reduced excess sludge by 45%. It was also experimentally demonstrated that presence of TCS increases the portion of active sludge microorganisms over the entire microbial population.

The SBR and its biofilm application potentials

2004 ◽  
Vol 50 (10) ◽  
pp. 1-10 ◽  
Author(s):  
P.A. Wilderer ◽  
B.S. McSwain
Keyword(s):  
Activated Sludge ◽  
Batch Reactor ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
Waste Streams ◽  
Sludge Flocs ◽  
Biofilm Reactors ◽  
Volatile Organic ◽  
High Level ◽  
Slow Growing

Twenty plus years of experience, innovation, and research in the field of biological wastewater treatment and biofilm applications lead to the conclusion that biofilms are in many cases more desirable in reactors than suspended activated sludge. Biofilm reactors can provide very long biomass residence times even when the hydraulic influent loading is low. This makes them particularly suitable when treatment requires slow growing organisms with poor biomass yield or when the wastewater concentration is too low to support growth of activated sludge flocs. Regardless of the settling characteristics of biological aggregates or the hydraulic influent loading the metabolic activity in the reactor can be maintained at a high level. This paper reviews the application of biofilms in sequencing batch reactor (SBR) systems to treat non-readily biodegradable substrates, volatile organic waste constituents, complex waste streams requiring co-metabolism, and particulate wastewaters. Recent research using the SBR to form aerobic granular sludge as a special application of biofilms is also discussed.

Sequencing batch reactor (SBR) as optimal method for production of granular activated sludge (GAS) – fluid dynamic investigations

2007 ◽  
Vol 55 (8-9) ◽  
pp. 151-158 ◽  
Author(s):  
B.E. Zima ◽  
L. Díez ◽  
W. Kowalczyk ◽  
A. Delgado
Keyword(s):  
Multiphase Flow ◽  
Activated Sludge ◽  
Sequencing Batch Reactor ◽  
Fluid Dynamic ◽  
Batch Reactor ◽  
Aerobic Condition ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
Major Influence ◽  
Optimal Method

Fluid dynamic investigations of multiphase flow (fluid, air, granules) in a sequencing batch reactor (SBR) are presented. SBR can be considered as an attractive technology for cultivation of granular activated sludge (GAS). Granulation is a complicated process and its mechanism is not fully understood yet. Many factors influence the formation and structure of aerobic granular sludge in a bioreactor. Extracellular polymer substances (EPS) and superficial gas velocity (SGV) play a crucial role for granules formation. Additionally, it is supposed that EPS production is stimulated by mechanical forces. It is also assumed that hydrodynamic effects have a major influence on the formation, shape and size of GAS in SBR under aerobic condition. However, the influence of stress on granulation is poorly investigated. Thus, in the present paper, fluid dynamic investigations of multiphase flow in a SBR, particularly effect of normal and shear strain, are reported. In order to analyse multiphase flow in the SBR, optical in-situ techniques with particle image velocimetry (PIV) and particle tracking velocimetry (PTV) are implemented. Obtained results show a characteristic flow pattern in a SBR. It is pointed out that additional effects like particle-wall collisions, inter particle collisions, erosion can also affect significantly granules formation.

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