Using Existing Facility to Maximize the Wet Weather Treatment Capacity of the Akron, Oh Water Reclamation Facility: Optimizing Existing Secondary Clarifiers

Siczka, John; Smith, Thomas F.; Hanna, Eugenie M; Cooper, James P.; Frank, David

doi:10.2175/193864714815941171

Cited by 2 publications

(5 citation statements)

References 2 publications

(2 reference statements)

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“…These results represent the culmination of a process that began in 2010 with completion of the initial assessment described above (CH2M HILL, 2010) based on modeling the biological treatment process using an International Water Association (IWA) Activated Sludge Model (ASM) and CFD analysis of proposed secondary clarifier modifications (the condition of the existing secondary clarifiers necessitated some level of modification). The potential increase in peak wet weather secondary treatment capacity identified in that evaluation, while quite surprising at the time, has been verified by subsequent field testing as described here and elsewhere (CH2M, 2010;Daigger et al, 2016;Siczka et al, 2014Siczka et al, , 2015Siczka et al, , 2016. The following lessons learned through application of the process followed for the City of Akron can be applied when this approach is used at other locations:…”

Section: Resultssupporting

confidence: 58%

“…Secondary clarifier stress tests were conducted in the relatively standard manner by sequentially altering the loading conditions on the clarifiers while collecting effluent TSS samples sequentially, and then analyzing the data to develop performance versus loading curves (Daigger and Buttz, 1998;Ontario Ministry of the Environment and Energy, 1996;Wahlberg, 2001). The results of these investigations have been reported elsewhere (CH2M, 2015;Daigger et al, 2016;Siczka et al, 2014Siczka et al, ., 2015 and were used to initially indicate potential increases in peak wet weather secondary treatment capacity and to guide further testing. They indicated that SORs approaching 3 m/h could be successfully sustained in the modified clarifiers.…”

Section: Methodssupporting

confidence: 60%

“…Test critical assumptions and develop contingency plans. Modification of Unit 6 to implement step feed and clarifier improvements and modification of Unit 5 clarifiers, followed by the testing program documented here and elsewhere (CH2M, 2010); Daigger et al, 2016;Siczka et al, 2014Siczka et al, , 2015Siczka et al, , 2016) allowed assessment of the actual peak wet weather secondary treatment achievable. Compliance with other effluent parameter limits (ammonia, phosphorus) was also verified.…”

Section: Resultsmentioning

confidence: 99%

“…The model includes laminar and turbulent flow with Newtonian flow in the inlet and clarified zone and non-Newtonian flow in the sludge blanket. The model was calibrated and validated using operational and stress test data, as described elsewhere (CH2M, 2015;Daigger et al, 2016;Siczka et al, 2014Siczka et al, , 2015Siczka et al, , 2016. The stress tests were accompanied by Vesilind settling tests as well as DSS and FSS tests.…”

Section: Methodsmentioning

confidence: 99%

“…The ease with which these capabilities could be retrofitted to Unit 6 for testing purposes made it the obvious focus for initial investigations. The objective of the work presented here and elsewhere (CH2M, 2015;Daigger et al, 2016;Siczka et al, 2014Siczka et al, , 2015Siczka et al, , 2016) was to determine the increased peak wet weather secondary treatment capacity achievable, with the objective of reducing the size of supplemental peak wet weather secondary treatment facilities needed. Full-scale testing was conducted using a portion (one of six trains) of the existing City of Akron WRF, supplemented with CFD analysis of the modified clarifiers.…”

Section: Introductionmentioning

confidence: 99%

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Marrying Step Feed with Secondary Clarifier Improvements to Significantly Increase Peak Wet Weather Treatment Capacity: An Integrated Methodology

Siczka¹,

Smith

Frank

et al. 2017

Water Environment Research

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The need to increase the peak wet weather secondary treatment capacity of the City of Akron, Ohio, Water Reclamation Facility (WRF) provided the opportunity to test an integrated methodology for maximizing the peak wet weather secondary treatment capacity of activated sludge systems. An initial investigation, consisting of process modeling of the secondary treatment system and computational fluid dynamics (CFD) analysis of the existing relatively shallow secondary clarifiers (3.3 and 3.7 m sidewater depth in 30.5 m diameter units), indicated that a significant increase in capacity from 416 000 to 684 000 m3/d or more was possible by adding step feed capabilities to the existing bioreactors and upgrading the existing secondary clarifiers. One of the six treatment units at the WRF was modified, and an extensive 2-year testing program was conducted to determine the total peak wet weather secondary treatment capacity achievable. The results demonstrated that a peak wet weather secondary treatment capacity approaching 974 000 m3/d is possible as long as secondary clarifier solids and hydraulic loadings could be separately controlled using the step feed capability provided. Excellent sludge settling characteristics are routinely experienced at the City of Akron WRF, raising concerns that the identified peak wet weather secondary treatment capacity could not be maintained should sludge settling characteristics deteriorate for some reason. Computational fluid dynamics analysis indicated that the impact of the deterioration of sludge settling characteristics could be mitigated and the identified peak wet weather secondary treatment capacity maintained by further use of the step feed capability provided to further reduce secondary clarifier solids loading rates at the identified high surface overflow rates. The results also demonstrated that effluent limits not only for total suspended solids (TSS) and five-day carbonaceous biochemical oxygen demand (cBOD5) could be maintained, but also for ammonia-nitrogen and total phosphorous (TP). Although hydraulic limitations in other parts of the WRP prevent this full capacity to be realized, the City is proceeding to implement the modifications identified using this integrated methodology.

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Section: Resultssupporting

confidence: 58%

Section: Methodssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Marrying Step Feed with Secondary Clarifier Improvements to Significantly Increase Peak Wet Weather Treatment Capacity: An Integrated Methodology

Siczka¹,

Smith

Frank

et al. 2017

Water Environment Research

Self Cite

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Characterizing shallow secondary clarifier performance where conventional flux theory over-estimates allowable solids loading rate

Siczka¹,

Smith

Frank

et al. 2016

Water Science and Technology

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The performance characteristics of relatively shallow (3.3 and 3.7 m sidewater depth in 30.5 m diameter) activated sludge secondary clarifiers were extensively evaluated during a 2-year testing program at the City of Akron Water Reclamation Facility (WRF), Ohio, USA. Testing included hydraulic and solids loading stress tests, and measurement of sludge characteristics (zone settling velocity (ZSV), dispersed and flocculated total suspended solids), and the results were used to calibrate computational fluid dynamic (CFD) models of the various clarifiers tested. The results demonstrated that good performance could be sustained at surface overflow rates in excess of 3 m/h, as long as the clarifier influent mixed liquor suspended solids (MLSS) concentration was controlled to below critical values. The limiting solids loading rate (SLR) was significantly lower than the value predicted by conventional solids flux analysis based on the measured ZSV/MLSS relationship. CFD analysis suggested that this resulted because mixed liquor entering the clarifier was being directed into the settled sludge blanket, diluting it and also creating a 'thin' concentration sludge blanket that overlays the thicker concentration sludge blanket typically expected. These results indicate the need to determine the allowable SLR for shallow clarifiers using approaches other than traditional solids flux analysis. A combination of actual testing and CFD analyses are demonstrated here to be effective in doing so.

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Using Existing Facility to Maximize the Wet Weather Treatment Capacity of the Akron, Oh Water Reclamation Facility: Optimizing Existing Secondary Clarifiers

Cited by 2 publications

References 2 publications

Marrying Step Feed with Secondary Clarifier Improvements to Significantly Increase Peak Wet Weather Treatment Capacity: An Integrated Methodology

Marrying Step Feed with Secondary Clarifier Improvements to Significantly Increase Peak Wet Weather Treatment Capacity: An Integrated Methodology

Characterizing shallow secondary clarifier performance where conventional flux theory over-estimates allowable solids loading rate

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