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Framework for Energy Neutral Treatment for the 21st Century Through Energy Efficient Aeration (WERF Report INFR2R12)
Citation:
Rosso, D. AND A. Shaw. Framework for Energy Neutral Treatment for the 21st Century Through Energy Efficient Aeration (WERF Report INFR2R12). Water Environment Research Foundation, Alexandria, VA, 2014.
Impact/Purpose:
Benefits: ♦ Demonstrates increased lifespan of diffusers and blowers. ♦ Demonstrates application of low-fouling diffusers and assessment of them using present value analysis. ♦ Increases understanding of the mechanisms that cause fouling. ♦ Demonstrates the science of, and techniques to, mitigate fouling. ♦ Promotes high-efficiency aeration systems. ♦ Provides standardized biological methods for assessing biofouling on diffusers.
Description:
Aeration is commonly identified as the most significant energy use in the treatment of wastewater and therefore garners significant focus in reducing energy use in the ultimate aspirational goal of achieving net energy neutrality for water resource recovery. This research establishes the mechanistic link between biofilm DNA concentration and reduced aeration efficiency caused by biofilm fouling. Although the connection between biofilm growth and fouling has been implicit in discussions of diffuser fouling for many years, this research provides directly measured evidence of the connection between biofouling and reduced diffuser efficiency. This was clearly established by studying systematically the evolution of aeration diffusers’ efficiency over time, concurrently with the biological study of the biofilm fouling the diffusers in order to understand the major factors contributing to diffuser fouling.While all diffusers foul eventually, some novel materials exhibited fouling resistance. Fouling mitigation techniques, such as chemical cleaning and membrane reverse-flexing were studied. However, during the course of this study the research could not conclude that these techniques were always effective in curbing effects of fouling. By linking bacterial growth with aeration efficiency and calculating the aeration process energy requirements from the latter, the research was able to show quantitatively the causal connection between bacterial fouling and energy wastage during aeration. The methodology applied here can be extended to perform parallel tests during the initial phases of aeration design to yield site-specific data that increase the robustness of design.Fine-pore diffused aeration is the most commonly used aeration system for new activated sludge treatment processes due to its high oxygen transfer efficiency. However, fouling of fine- pore diffusers has the double-negative effect of greatly diminishing their oxygen transfer efficiency and increasing the back-pressure on the blower, which decreases its operating efficiency. Development of a fundamental understanding of the science of fouling and its impact on fine-pore diffusers facilitates the development of mitigation strategies and guidelines. Overall, application of the findings of this research will result in reduced energy usage at water resource recovery facilities (WRRFs) that will enable them to close the gap between energy use and energy generation to ultimately reach the goal of energy neutrality. [NOTE: The link below connects to a WERF site where the Final Report can be downloaded for free, after registering at the WERF site. To view the WERF registration link, which is on the WERF home page (www.werf.org), it may be necessary to move the page so the top right corner is visible. For some projects the Executive Summary is available and can be downloaded for free without registering on the WERF site.]
