An aeration control strategy for oxidation ditch processes based on online oxygen requirement estimation

• Published in: Water science and technology 2013-01, Vol.68 (1), p.76-82
• Main Authors: ZHAN, J. X, IKEHATA, M, MAYUZUMI, M, KOIZUMI, E, KAWAGUCHI, Y, HASHIMOTO, T
• Format: Article
• Language: English
• Subjects: Activated sludge; Aeration; Applied sciences; Biochemical oxygen demand; Computer simulation; Control systems; Control theory; Electricity consumption; Exact sciences and technology; Feedback control; Feedforward control; Models, Theoretical; Nitrogen; Nitrogen removal; Oxidation; Oxidation-Reduction; Oxygen; Oxygen - metabolism; Oxygen requirement; Pollution; Sewage - microbiology; Strategy; Suspended solids; Temperature; Waste Disposal, Fluid - methods; Wastewater treatment; Wastewater treatment plants; Water treatment and pollution
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2013.226

A feedforward-feedback aeration control strategy based on online oxygen requirements (OR) estimation is proposed for oxidation ditch (OD) processes, and it is further developed for intermittent aeration OD processes, which are the most popular type in Japan. For calculating OR, concentrations of influent biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN) are estimated online by the measurement of suspended solids (SS) and sometimes TKN is estimated by NH4-N. Mixed liquor suspended solids (MLSS) and temperature are used to estimate the required oxygen for endogenous respiration. A straightforward parameter named aeration coefficient, Ka, is introduced as the only parameter that can be tuned automatically by feedback control or manually by the operators. Simulation with an activated sludge model was performed in comparison to fixed-interval aeration and satisfying result of OR control strategy was obtained. The OR control strategy has been implemented at seven full-scale OD plants and improvements in nitrogen removal are obtained in all these plants. Among them, the results obtained in Yumoto wastewater treatment plant were presented, in which continuous aeration was applied previously. After implementing intermittent OR control, the total nitrogen concentration was reduced from more than 5 mg/L to under 2 mg/L, and the electricity consumption was reduced by 61.2% for aeration or 21.5% for the whole plant.