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Odor Management I — Quantifying and Treating
Published in Roger T. Haug, of Compost Engineering, 2018
One disadvantage with the use of activated sludge is the requirement that the gases be compressed to about 4 to 10 psig for introduction to the submerged diffusers. The compost gases can be delivered to the suction side of the aeration compressors. The City of Los Angeles blended sewer gases with aeration air in this manner for over 20 years with no significant deterioration of the centrifugal compressors. Ostojic et al.65 recommended that materials selection consider the potentially corrosive properties of compost exhaust. High quality stainless steel or non-ferrous piping and diffusers were recommended. It was also recommended that coarse bubble diffusers be used to avoid fouling and plugging problems observed with fine-bubble devices. Many compost plants, including facilities at Springfield, Massachusetts and Bickenbach, Germany use dedicated coarse-bubble diffusers to introduce the compost gases into the activated sludge process to reduce plugging problems. Return loads to the activated sludge system should be considered, particularly ammonia when nitrification is required.
Secondary treatment
Published in Rumana Riffat, Taqsim Husnain, Fundamentals of Wastewater Treatment and Engineering, 2022
Air Diffusers – used to inject air into the aeration tank. The diffusers may be mounted along the side of the tank, or they may be placed in a manifold along the bottom of the aeration tank, as illustrated in Figure 8.10. Air diffusers may produce coarse bubbles or fine bubbles. Coarse bubbles may be up to 25 mm in diameter, while fine bubbles are 2–2.5 mm in diameter. There are advantages and disadvantages of both types of diffusers. Fine bubble diffusers have greater energy requirements and clog easily, even though they have better oxygen transfer due to larger surface area per volume. Coarse bubble diffusers have lower oxygen transfer rates, but require less maintenance and have a lower headloss.
Application of real-time nitrogen measurement for intermittent aeration implementation in a biological nitrogen removal system: performances and efficiencies
Published in Environmental Technology, 2019
R. Ferrentino, M. Langone, M. Vian, G. Andreottola
One of the key factors for the control of aeration is maintaining the defined dissolved oxygen (DO) levels in the aeration step for aerobic microorganisms performing organic carbon removal and nitrification. The energy efficiency criteria have gradually led to the replacement of mechanical aerators by diffused aerators, which have a higher oxygen transfer efficiency. Fine-bubble diffusers have been preferred compared to coarse-bubble diffusers, because of high oxygen transfer and energy efficiency. In the last decade, a gas-permeable membrane (often a hollow fiber membrane), immersed in a suspended biomass, used both for biofilm growth on the carrier and for oxygen diffuser supply to the biofilm, has proved to transfer oxygen very efficiently [6,7]. Further, the replacement of existing conventional blower technology with direct-drive, high-speed, turbo blowers is often identified in energy audits as high priority projects for improving the WWTPs energy efficiency [8]. A substantial reduction of oxygen consumption could be obtained by automatically controlling the oxygen required for the aeration, both in continuous aeration systems [9] and in intermittent aeration activated process, where oxic and anoxic periods alternate [10]. These changes favor a significant decrement of the energy consumption and thus of the operational costs of the whole WWTP.