Reducing Energy Needs at a Wastewater Treatment Plant Through Enhanced Solid Capture by High-Rate Contact Stabilization (HiCS) Primary Treatment Process

Extended aeration treatment processes at wastewater treatment plans are designed to reduce the nitrogen load in the wastewater by allowing extra treatment time for nitrification. The process also allows treatment plants a choice to bypass primary sedimentation, because the extended aeration process can degrade particulate organic loads that typically require primary treatment.

One of the disadvantages of relying on secondary treatment to remove particulate organics, instead of utilizing primary treatment, is that secondary sludge has a lower methane potential than primary sludge. As a result, there is an overall reduced energy recovery from methane production and may not even produce sufficient methane to maintain digester temperature. Relying primarily on extended aeration for treatment, and eliminating primary treatment, therefore, can impact subsequent residual management program of the plant. Modified primary treatment processes, including high-rate contact stabilization (HiCS), is designed to enhance carbon capture to the primary sludge. In addition to enhanced carbon capture, the produced sludge also presents a higher methane potential than secondary sludge that have gone through an extended aeration period. Extended aeration process, on the other hand, takes in most carbons that would otherwise have been removed by the primary, oxidize them into CO2. Therefore, in addition to reduced carbon capture, it also requires additional aeration energy to oxidize these carbons. Therefore, installing an HiCS process not only can produce more methane from enhanced carbon capture, but also reduce subsequent aeration energy consumption.

A case study of an existing 2 MGD plant was carried out to determine if adding a HiCS primary treatment process would better sustain anaerobic digestion and result in an overall energy saving for the plant. The plant that was evaluated struggled to generate sufficient methane once primary treatment was mostly eliminated when an extended aeration process was installed as part of a plant upgrade. The case study centered on utilizing a mass-balance approach of carbon, measured as COD, of both the existing plant and the plant altered to include a HiCS primary treatment phase.

The result shows that adding an HiCS primary treatment process to the plant almost doubled (97% increase) the potential methane production. The required aeration energy of the altered treatment process was 6% less than the existing plant setup. The increased methane production alone could theoretically cover all the energy requirements of the plant.

To realize the theoretical methane production at the plant, capital improvements would be required. There are existing tanks at the plant that could be repurposed for primary treatment. New piping, diffusers, mixers, electrical system, and baffling would likely be required to convert the tanks. The structural integrity of the tanks would need to be evaluated and existing imperfections (i.e. cracks) would need to be fixed. An epoxy coating or other liner would likely need to be added to the tanks, to increase their lifespan. Another required improvement at the plant would be upgrades to the plant’s existing methane collection system, which was previously used to heat the anaerobic digester. To achieve net zero energy requirements at the plant, a modern and efficient gas turbine or other methane conversion system would need to be installed.

The costs for such improvements would be on the order of magnitude of ten million dollars ($10M). The annual electricity costs for the plant are around two hundred thousand dollars ($200K), which could be eliminated by implementing an HiCS primary treatment process. The payback period for when these annual benefits would cumulatively exceed the upfront capital costs would exceed the expected lifespan of the new system.

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Work Title Reducing Energy Needs at a Wastewater Treatment Plant Through Enhanced Solid Capture by High-Rate Contact Stabilization (HiCS) Primary Treatment Process
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Open Access
Creators
  1. Patrick Raymond Boggs
Keyword
  1. The Master of Engineering in Environmental Engineering
  2. ENVE
License In Copyright (Rights Reserved)
Work Type Research Paper
Publication Date December 2023
Deposited December 08, 2023

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  • Created

    December 08, 2023 10:22 by hpl5273

  • Updated

    December 08, 2023 10:22 by [unknown user]

  • Added Creator Patrick Raymond Boggs

    December 08, 2023 10:24 by hpl5273

  • Added Patrick Boggs - ENVE_MENG Final Paper FA23.pdf

    December 08, 2023 10:24 by hpl5273

  • Updated License Show Changes

    December 08, 2023 10:25 by hpl5273

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    • https://rightsstatements.org/page/InC/1.0/
  • Published

    December 08, 2023 10:25 by hpl5273

  • Updated Keyword, Description Show Changes

    December 11, 2023 10:54 by avs5190

    Keyword
    • The Master of Engineering in Environmental Engineering, ENVE, Reducing Energy Needs at a Wastewater Treatment Plant Through HiCS
    • The Master of Engineering in Environmental Engineering, ENVE
    Description
    • Abstract
    • Extended aeration treatment processes at wastewater treatment plans are designed to reduce the nitrogen load in the wastewater by allowing extra treatment time for nitrification. The process also allows treatment plants a choice to bypass primary sedimentation, because the
    • extended aeration process can degrade particulate organic loads that typically require primary treatment.
    • One of the disadvantages of relying on secondary treatment to remove particulate organics, instead of utilizing primary treatment, is that secondary sludge has a lower methane
    • potential than primary sludge. As a result, there is an overall reduced energy recovery from methane production and may not even produce sufficient methane to maintain digester
    • temperature. Relying primarily on extended aeration for treatment, and eliminating primary treatment, therefore, can impact subsequent residual management program of the plant.
    • Modified primary treatment processes, including high-rate contact stabilization (HiCS), is designed to enhance carbon capture to the primary sludge. In addition to enhanced carbon capture, the produced sludge also presents a higher methane potential than secondary sludge that
    • have gone through an extended aeration period. Extended aeration process, on the other hand, takes in most carbons that would otherwise have been removed by the primary, oxidize them into CO2. Therefore, in addition to reduced carbon capture, it also requires additional aeration energy to oxidize these carbons. Therefore, installing an HiCS process not only can produce more methane from enhanced carbon capture, but also reduce subsequent aeration energy consumption.
    • One of the disadvantages of relying on secondary treatment to remove particulate organics, instead of utilizing primary treatment, is that secondary sludge has a lower methane potential than primary sludge. As a result, there is an overall reduced energy recovery from methane production and may not even produce sufficient methane to maintain digester temperature. Relying primarily on extended aeration for treatment, and eliminating primary treatment, therefore, can impact subsequent residual management program of the plant.
    • Modified primary treatment processes, including high-rate contact stabilization (HiCS), is designed to enhance carbon capture to the primary sludge. In addition to enhanced carbon capture, the produced sludge also presents a higher methane potential than secondary sludge that have gone through an extended aeration period. Extended aeration process, on the other hand, takes in most carbons that would otherwise have been removed by the primary, oxidize them into CO2. Therefore, in addition to reduced carbon capture, it also requires additional aeration energy to oxidize these carbons. Therefore, installing an HiCS process not only can produce more methane from enhanced carbon capture, but also reduce subsequent aeration energy consumption.
    • A case study of an existing 2 MGD plant was carried out to determine if adding a HiCS primary treatment process would better sustain anaerobic digestion and result in an overall energy saving for the plant. The plant that was evaluated struggled to generate sufficient methane once primary treatment was mostly eliminated when an extended aeration process was installed as part of a plant upgrade. The case study centered on utilizing a mass-balance
    • approach of carbon, measured as COD, of both the existing plant and the plant altered to include a HiCS primary treatment phase.
    • The result shows that adding an HiCS primary treatment process to the plant almost doubled (97% increase) the potential methane production. The required aeration energy of the altered treatment process was 6% less than the existing plant setup. The increased methane
    • production alone could theoretically cover all the energy requirements of the plant.
    • To realize the theoretical methane production at the plant, capital improvements would be required. There are existing tanks at the plant that could be repurposed for primary treatment. New piping, diffusers, mixers, electrical system, and baffling would likely be required to convert
    • the tanks. The structural integrity of the tanks would need to be evaluated and existing imperfections (i.e. cracks) would need to be fixed. An epoxy coating or other liner would likely need to be added to the tanks, to increase their lifespan. Another required improvement at the
    • plant would be upgrades to the plant’s existing methane collection system, which was previously used to heat the anaerobic digester. To achieve net zero energy requirements at the plant, a modern and efficient gas turbine or other methane conversion system would need to be installed.
    • The costs for such improvements would be on the order of magnitude of ten million dollars ($10M). The annual electricity costs for the plant are around two hundred thousand dollars ($200K), which could be eliminated by implementing an HiCS primary treatment process. The payback period for when these annual benefits would cumulatively exceed the
    • upfront capital costs would exceed the expected lifespan of the new system.
    • The costs for such improvements would be on the order of magnitude of ten million dollars ($10M). The annual electricity costs for the plant are around two hundred thousand dollars ($200K), which could be eliminated by implementing an HiCS primary treatment process. The payback period for when these annual benefits would cumulatively exceed the upfront capital costs would exceed the expected lifespan of the new system.
  • Updated

    April 04, 2024 10:22 by [unknown user]