(Chapter8)Aeration Control of Activated Sludge Wastewater Treatment Plants by Continuous Oxygen Respiration Rates Measurements

摘要

The design and operation of an efficient and reliable aeration control system in the activated sludge wastewater treatment plants is very important for achieving valuable energy savings, biological process stability and improved treated effluent qualities. What is typically used as an aeration control method is to change plant oxygenation capacity at pre-established times of the day based on operator experience, or the installation of dissolved oxygen meters at various locations and depths of the aeration tank, in order to monitor and keep concentrations within the desired range. Deviations from nominal values should be prevented by stepwise adjustments of the oxygen transfer capacity, given by either a manual or an automatic control of the aerators or blowers in operation. The main goal of this publication is to highlight, to plant design engineers and operators, the potential implementation of an alternative aeration control system based on field equipment, specifically designed and operated for the continuous measurement of the mixed liquor oxygen respiration rate. This provides a good indication of the variable oxygen consumption in the aeration tank. Either more or less aeration should be supplied at higher or lower respiration rate results, respectively. This technology can be applied to any type of activated sludge treatment plants, including municipal, industrial and mining camp operations. This approach is particularly recommended in plants integrated with oxidation ditches and carrousel type biological reactors, with localized oxygen input applied by mechanical aerators and, when aerobic and anoxic zones are present simultaneously in the aeration tank due to the nitrification-denitrification process, or caused by mixing conditions. The respirometer operation should deliver a fast return on investment due to the aeration energy savings. The author?s experience in Israel is described, with the design and use of a continuous respirometer equipment, implemented during the operation of a technical scale pilot plant, and in the Soreq (Tel-Aviv)full-scale wastewater treatment plant. A continuously working instrument is described, including its operational principle, interpretation of results and potential applications.