Full-Scale Step-Feed Nutrient Removal Systems: A Comparison between Theory and Reality

Johnson, Bruce R.; Crawford, George; Wable, Milind V.; Goodwin, Steve

doi:10.2175/193864703784679288

Cited by 2 publications

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“…The step‐feed activated sludge process has many advantages over other types of activated sludge processes, including more uniform distribution of oxygen demand, superior ability to handle peak wet‐weather flows, and flexible operation. Step‐feed systems can often achieve treatment objectives in a smaller bioreactor volume ( Johnson et al, 2003 ), and the process can also be operated to achieve low effluent total inorganic nitrogen concentrations ( Amad, 2003 ).…”

Section: Introductionmentioning

confidence: 99%

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Maximum Nitrogen Removal in the Step‐Feed Activated Sludge Process

Tang¹,

Kuo²,

Weiss³

2007

Water Environment Research

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This paper presents a mathematical framework that can be used to determine the flow distributions for a step-feed activated sludge process that result in maximum nitrogen removal. The model indicates that nitrogen removal efficiency in a step-feed activated sludge process is highly dependent on the ultimate biochemical oxygen demand (BOD L )-to-total Kjeldahl nitrogen (TKN) ratio of the wastewater. For typical domestic wastewater, which has a relatively high BOD L -to-TKN ratio, the step-feed process will outperform the Modified Ludzack-Ettinger process for nitrogen removal, when the flow to each step is optimally distributed. Using plantspecific water quality data and operating conditions from a 1-year period, nitrogen removal performance for four step-feed activated sludge plants operated by the Sanitation Districts of Los Angeles County (California) was calculated using the developed model. The calculated nitrogen removal efficiencies match well with the actual plant performance data. These results validate the model as a useful tool for predicting nitrogen removal in a stepfeed activated sludge process. Other analyses revealed that improvements in nitrogen removal at existing facilities are achievable by adjusting the split of primary effluent flow to each anoxic zone several times during the day. The timing of the adjustments and the optimal flow splits can be determined from data on diurnal fluctuations in BOD L and TKN concentrations. An example is provided to illustrate the application of such an operating strategy and the potential enhancement of nitrogen removal. Water Environ. Res., 79, 367 (2007).

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Section: Introductionmentioning

confidence: 99%

“…Step-feed systems can often achieve treatment objectives in a smaller bioreactor volume (Johnson et al, 2003), and the process can also be operated to achieve low effluent total inorganic nitrogen concentrations (Amad, 2003).…”

Section: Introductionmentioning

confidence: 99%

Maximum Nitrogen Removal in the Step‐Feed Activated Sludge Process

Tang¹,

Kuo²,

Weiss³

2007

Water Environment Research

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“…The step-feed activated sludge process has many advantages including more uniform oxygen demand, ability to handle peak wet-weather flows, flexible operation, and reduced bioreactor volume for a defined capacity (Johnson et al, 2003). The process can also be operated to achieve very low effluent total nitrogen concentrations (Amad, 2003).…”

Section: Introductionmentioning

confidence: 99%

Maximum Nitrogen Removal in the Step-Feed Activated Sludge Process

Tang¹,

Kuo²,

Weiss³

et al. 2004

proc water environ fed

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This paper presents a mathematical framework that can be used to determine the flow distributions in a step-feed activated sludge process for achieving the greatest nitrogen removal efficiency. The model indicates that the nitrogen removal efficiency in a step-feed activated sludge process is highly dependent on the BOD to TKN ratio of the wastewater. For typical domestic wastewater, which has a relatively high BOD to TKN ratio, the step-feed process will outperform the Modified Ludzack-Ettinger (MLE) process for nitrogen removal, if the flow to each step is optimally distributed. Nitrogen removal performance of four step-feed activated sludge plants operated by the Los Angeles County Sanitation Districts is calculated with the developed model using plant specific water quality data and operating conditions, and is compared with actual observations over a one-year period. The calculated nitrogen removal efficiencies match closely with the actual data at these four plants indicating the model is a useful tool for predicting nitrogen removal in a step-feed activated sludge process. To achieve the greatest nitrogen removal efficiency in a step-feed activated sludge process, the operator may consider the use of two or three daily adjustments of primary effluent flow to each step based on diurnal fluctuations of BOD and TKN. An example is provided to illustrate the application of such an operating strategy and the potential enhancement of nitrogen removal.

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Full-Scale Step-Feed Nutrient Removal Systems: A Comparison between Theory and Reality

Cited by 2 publications

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Maximum Nitrogen Removal in the Step‐Feed Activated Sludge Process

Maximum Nitrogen Removal in the Step‐Feed Activated Sludge Process

Maximum Nitrogen Removal in the Step-Feed Activated Sludge Process

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