Impacts of SRT on Particle Size Distribution and Reactor Performance in Activated Sludge Processes

Li, Zhongtian; Stenstrom, Michael K.

doi:10.2175/106143017x15054988926523

Cited by 18 publications

(9 citation statements)

References 34 publications

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“…Settling test conducted on activated sludge with sludge retention time ranging from 0.25 to 12 days showed that increased SRTs resulted in an exponential decrease in percent dispersion (non-flocculent or pinpoint floc), and an increase in the particle size of the floc, leading to a good sludge settling property. However, SRTs greater than 12 d resulted in a reduce in the diameter of the floc and the decline in sludge settling property 57 . Significantly long SRT can lead to poor sedimentation performance of activated sludge, resulting in further sludge bulking.…”

Section: Discussionmentioning

confidence: 95%

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Zhang

Yao

Wang

et al. 2019

Sci Rep

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Sludge bulking is a major problem that restricts the development of the activated sludge process. The microbial community responsible for sludge bulking varies depending on water quality and operational conditions. This study analysed the microbial community of bulking sludge in oxidation ditch with ultra-low sludge loading and long sludge retention time using high-throughput sequencing. The study found that the relative abundance of bacterial genus Saprospiraceae_norank was the highest in bulking sludge, reaching 13.39–28.83%, followed by Comamonadaceae_unclassified, Ardenticatenia_norank and Tetrasphaera, with the relative abundance of 4.59–11.08%, 0.52–16.60% and 0.17–8.92% respectively. In contrast, the relative abundance of bacteria that easily caused sludge bulking including Microthrix (0.54–2.47%), Trichococcus (0.32–1.71%), Gordonia (0.14–1.28%), and Thiothrix (0.01–0.06%) were relatively low. Saprospiraceae_norank was predominant and induced sludge bulking in oxidation ditch. The relative abundance of fungal genus Trichosporon was the highest in bulking sludge, reaching 16.95–24.98%, while other fungal genera were Saccharomycetales_unclassified (5.59–14.55%), Ascomycota_norank (1.45–13.51%), Galactomyces (5.23–11.23%), and Debaryomyces (7.69–9.42%), whereas Trichosporon was the dominant fungal genus in bulking sludge. This study reported that excessive Saprospiraceae_norank can induce sludge bulking for the first time, which provides important knowledge to control sludge bulking.

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Section: Discussionmentioning

confidence: 95%

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Zhang

Yao

Wang

et al. 2019

Sci Rep

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“…Abbasi et al [84] and Pilli et al [85] indicated that gas entrapment in sludge flocs can lower the cavitation threshold pressure. Richard [86] found that small flocs (usually with diameter < 50 μm), consisting only of floc-forming bacteria without a filament backbone, that commonly occur under starvation (typically when the food to microorganism ratio (F/M) [18], is very small [87], or the sludge age is extended [88]) or chronic toxicity conditions, are particularly susceptible to disruption by external forces such as ultrasound, which is consistent with other work on the effects of floc size. Zielewicz [60] suggested that the mineral/organic matter ratio of sludge was another important factor influencing the efficiency of ultrasound disruption, due to its effect on the mechanical strength, but did not explain how they were related.…”

Section: Factors Influencing the Efficiency Of Enzyme Extraction By Smentioning

confidence: 99%

Enzyme Recovery from Biological Wastewater Treatment

Liu¹,

Smith²

2020

Waste Biomass Valor

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Enzymes are high value industrial bio-catalysts with extensive applications in a wide range of manufacturing and processing sectors, including the agricultural, food and household care industries. The catalytic efficiency of enzymes can be several orders higher compared to inorganic chemical catalysts under mild conditions. However, the nutrient medium necessary for biomass culture represents a significant cost to industrial enzyme production. Activated sludge (AS) is a waste product of biological wastewater treatment and consists of microbial biomass that degrades organic matter by producing substantial quantities of hydrolytic enzymes. Therefore, enzyme recovery from AS offers an alternative, potentially viable approach to industrial enzyme production. Enzyme extraction from disrupted AS flocs is technically feasible and has been demonstrated at experimental-scale. A critical review of disruption techniques identified sonication as potentially the most effective and suitable method for enzyme extraction, which can be scaled up and is a familiar technology to the water industry. The yields of different enzymes are influenced by wastewater treatment conditions, and particularly the composition, and can also be controlled by feeding sludge with specific target substrates. Nevertheless, hydrolytic enzymes can be effectively extracted directly from waste AS without specific modifications to standard wastewater treatment processes. Purification, concentration and stabilisation/immobilisation techniques can also greatly expand the industrial application and increase the economic value and marketability of enzyme products extracted from AS. Concentrated and purified AS enzymes could readily substitute inorganic and/or commercial bioenzyme catalysts in many industrial applications including, for example, leather processing, and in detergent and animal feed formulation. Enzyme extraction from AS therefore offers significant economic benefits to the Water Industry by recovering valuable resources from wastewater. They can also optimise important waste treatment processes, such as the anaerobic digestion (AD) of sewage sludge, increasing biogas and renewable energy production. The enzyme-extracted sludge exhibits improved treatment properties, such as increased settleability, dewaterability, and anaerobic digestibility for biogas production, assisting sludge management by wastewater treatment plants (WWTPs) and enabling the further utilisation of the residual sludge. Graphic Abstract

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“…Using laboratory-scale MLE and IFAS reactors data fed synthetic wastewater and a survey of five full-scale WRRFs, Li and Stenstrom (2018) determined that SRT changes had immediate effect on the particle size distribution in the mixed liquor.…”

Section: Optimizationmentioning

confidence: 99%

Modeling, instrumentation, automation, and optimization of water resource recovery facilities (Review of 2018 Literature) DIRECT

Sweeney

Kabouris

2020

Water Environment Research

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Impacts of SRT on Particle Size Distribution and Reactor Performance in Activated Sludge Processes

Cited by 18 publications

References 34 publications

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

The microbial community in filamentous bulking sludge with the ultra-low sludge loading and long sludge retention time in oxidation ditch

Enzyme Recovery from Biological Wastewater Treatment

Modeling, instrumentation, automation, and optimization of water resource recovery facilities (Review of 2018 Literature) DIRECT

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