Assessing activated sludge morphology by laser and image analysis

Jun, Wu; Wheatley, Andrew D.

doi:10.1680/wama.2010.163.3.139

Cited by 7 publications

(3 citation statements)

References 14 publications

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“…indicated that the apparent K O,AOB was higher than K O,NOB when the floc size was above 100 µm diameter. Since the activated sludge floc diameter was usually above 100 µm, this explained the high apparent NOB oxygen half‐saturation index reported in the literature …”

Section: Discussionmentioning

confidence: 98%

Activated sludge floc morphology and nitrifier enrichment can explain the conflicting reports on the oxygen half‐saturation index for ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB)

Zhang

2017

J of Chemical Tech & Biotech

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BACKGROUND: Ammonium oxidizing bacteria (AOB) have been suggested to have a lower oxygen half-saturation index than that of nitrite oxidizing bacteria (NOB), i.e. K O,AOB < K O,NOB . However, recent research has shown the opposite. We propose that biomass floc morphology and nitrifier enrichment are the causes of the conflicting reports, thus sludge samples with low NOB enrichment were ultrasonicated to produce samples with different floc diameters and tested for their K O,AOB and K O,NOB . RESULTS: Experimental results showed that the apparent K O,NOB values stabilized at c. 0.20 mg O 2 L −1 after the activated sludge sample was ultrasonicated and the medium floc diameter was reduced from c. 420 to 50 m. In comparison, the apparent K O,AOB dropped significantly from c. 1.5 to 0.24 mg O 2 L −1 . Simulation results were in agreement with the experimental observations. CONCLUSIONS: High floc diameter and low NOB enrichment were identified to be the reason for the reversion in the comparison of measured K O,AOB and K O,NOB . The study explains the conflicting reporting on the relative comparison of measured K O,AOB and K O,NOB .the comparison of K O,AOB and K O,NOB was noted when the AOB and NOB composition was 30% and 5%, respectively. DISCUSSION The anomaly of K O,AOB and K O,NOBThe NOB repression is a vital step to apply the recently developed autotrophic nitrogen removal. 24 The relative comparison of K O,AOB and K O,NOB is critical in choosing the appropriate DO concentration to achieve NOB repression and nitritation. The low DO concentration used for NOB repression was based on the belief that the NOB oxygen half-saturation index was lower than that of AOB. The K O,AOB and K O,NOB reported in Ref. 10 was 1.16 and 0.16 mg O 2 L −1 , therefore, a relative high DO concentration of 1.5 mg O 2 L −1 was used by the authors to achieve nitritation, instead of the low DO concentration of 0.4-0.6 mg O 2 L −1 used by others. 7,25 This study showed that the activated sludge floc morphology not only changed the absolute value of apparent K O,AOB and K O,NOB (i.e. high K O,AOB and K O,NOB at large floc diameter), but also the relative values of K O,AOB and K O,NOB . The impact of increasing floc

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Section: Discussionmentioning

confidence: 98%

Activated sludge floc morphology and nitrifier enrichment can explain the conflicting reports on the oxygen half‐saturation index for ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB)

Zhang

2017

J of Chemical Tech & Biotech

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“…An excess of filamentous bacteria is a common settlement problem affecting the activated sludge process. In the paper by Wu and Wheatley (2010), the activated sludge morphology was monitored by image analysis and laser scattering. These were compared with the conventional sludge volume index (SVI).…”

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confidence: 99%

“…The second, third and fourth papers describe solutions to improve river water quality through the design of detention ponds, (Prohaska et al, 2010); design of biological aerated filters for the treatment of food-related industrial effluents (Osorio et al, 2010); and improvements to monitoring of the activated sludge process used to treat sewage (Wu and Wheatley, 2010). The fifth paper (Rao et al, 2010) continues with the water quality theme but focuses on the issue of drinking water quality, evaluating the use of magnesium oxide in India to reduce excessive fluoride levels.…”

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confidence: 99%

Editorial

Pollard¹

2010

Proceedings of the Institution of Civil Engineers - Water Manag

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Most of the papers in this issue of Water Management are concerned with the area of water quality analysis and management. This is an area of engineering which is vital to the health and well-being of millions of people worldwide. For example, fluoride contamination of groundwater from geochemical sources is a serious environmental and public health issue in India and 62 million people are potentially at risk from drinking fluoride-contaminated water.The first paper by Huong et al. (2010) illustrates the problems of heavy metal contamination to river sediments in Vietnam, which occurred due to inadequate industrial wastewater treatment. The second, third and fourth papers describe solutions to improve river water quality through the design of detention ponds, (Prohaska et al., 2010); design of biological aerated filters for the treatment of food-related industrial effluents (Osorio et al., 2010); and improvements to monitoring of the activated sludge process used to treat sewage (Wu and Wheatley, 2010). The fifth paper (Rao et al., 2010) continues with the water quality theme but focuses on the issue of drinking water quality, evaluating the use of magnesium oxide in India to reduce excessive fluoride levels. The final paper (Clayton et al., 2010) is concerned with the issue of leakage from water supply pipes and evaluates the contribution due to tree root-induced desiccation of clay soils.The paper by Huong et al. (2010), analyses the issue of heavy metal contamination of river sediments in Hanoi, Vietnam. The environmental impact of this industrial wastewater pollution is high as the rivers are the main source of irrigation water for suburban agricultural land and feed water sources for fish farming ponds. The level of heavy metals in aquatic environments has been of much concern due to the adverse effects of some metals on living organisms in the food chain as well as on human health. Most of the heavy metals have exceeded the maximum permissible level for crop growth. Metal concentrations in sediments appear to be closely related to the type of manufacturing plants located along the rivers. Countermeasures by the government and the technological improvement of wastewater treatment in manufacturing processes are needed.It is well known that detention storage ponds reduce flood risk. They also play a vital role in protecting the water quality of natural water systems by retaining contaminated storm water runoff from construction sites, agricultural land or industrial areas. In order to design detention ponds the outflow characteristic must be accurately known. The paper by Prohaska et al. (2010) examines the discharge characteristics of a circular orifice cut into a vertical riser pipe as an outflow mechanism for the detention pond. In particular, the effects of the head above the orifice, the size of the orifice and the size of the riser pipe on the discharge coefficient are evaluated.Some food and agricultural industries consume a great deal of water and generate large quantities of wastewater. This wastewat...

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Comparison of laser diffraction and image analysis for measurement of Streptomyces coelicolor cell clumps and pellets

et al. 2012

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Morphology is important in industrial processes involving filamentous organisms because it affects the mixing and mass transfer and can be linked to productivity. Image analysis provides detailed information about the morphology but, in practice, it is often laborious including both collection of high quality images and image processing. Laser diffraction is rapid and fully automatic and provides a volume-weighted distribution of the particle sizes. However, it is based on a number of assumptions that do not always apply to samples. We have evaluated laser diffraction to measure cell clumps and pellets of Streptomyces coelicolor compare to image analysis. Samples, taken five times during fed-batch cultivation, were analyzed by image analysis and laser diffraction. The volume-weighted size distribution was calculated for each sample. Laser diffraction and image analysis yielded similar size distributions, i.e. unimodal or bimodal distributions. Both techniques produced similar estimations of the population means, whereas the estimates of the standard deviations were generally higher using laser diffraction compared to image analysis. Therefore, laser diffraction measurements are high quality and the technique may be useful when rapid measurements of filamentous cell clumps and pellets are required.

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Assessing activated sludge morphology by laser and image analysis

Cited by 7 publications

References 14 publications

Activated sludge floc morphology and nitrifier enrichment can explain the conflicting reports on the oxygen half‐saturation index for ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB)

Activated sludge floc morphology and nitrifier enrichment can explain the conflicting reports on the oxygen half‐saturation index for ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB)

Editorial

Comparison of laser diffraction and image analysis for measurement of Streptomyces coelicolor cell clumps and pellets

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