Adaptive control of the oxidation ditch reactors in a wastewater treatment plant

Abstract

This paper describes the application of adaptive predictive expert (ADEX) control methodology to the oxidation ditch reactor in the wastewater treatment plant of Ceutí (Murcia, Spain) and evaluates the performance of the ADEX control system against that of the previous control system operating the plant. After a basic description of ADEX control methodology, the ditch reactor is described, as well as the control objectives and the control strategy, which focused on energy consumption reduction. The results of the application of the ADEX control system show significant improvement compared with the previous control system in terms of higher stability and precision of controlled variables, reduction of energy consumption of the plant, and better quality of the effluent water. Figure 4, the upper plot of Figure 7 shows the trend curves and operational limits of the redox in both reactors; the middle plot shows the evolution of the DO in both reactors and the common set point. The third plot shows the gate valve openings. As inThe ADEX controllers used during the nitrification phase to control the DO in the biological reactors, operated in an AP domain, and their sequence of calculations was basically that described in Section 2.2. These were single-input single-output controllers with a control period of 15 s and an AP model described by Equation (3), that is, two Ǫ i .k/ and three O b i .k/ parameters. The driver block dynamics were consistent with those of a second-order model with damping ratio equal to one and time constant equal to one control period. The performance of these controllers is illustrated by the results presented in Figures 7 and 8 and discussed in the next section. Figure 8. Dissolved oxygen control redox evolution during one nitrification/denitrification cycle.The dynamics in one nitrification/denitrification cycle is shown in more detail in Figures 8 and 9. The upper plot of Figure 9 shows the trend curves of the mean position deviation variable o and its set point; the second plot shows the pressure in the common collector and its set point, and the third, the evolution of the frequency converter of the blower. DISCUSSION OF THE RESULTSThe Ceutí WWTP currently operates with a wastewater flow of 3000 m 3 /day that is considerably lower than the designed wastewater flow. A single blower is therefore sufficient to provide the Figure 9. Pressure evolution during one nitrification/denitrification cycle.

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“…Furthermore, according to [34][35][36], the average daily effluent ammonia-N concentration was 0.15 mg/L, while the average daily effluent BOD 5 concentration was 5 mg/L, resulting in effluent ammonia-N and BOD 5 reductions of 89 percent and 50%, respectively. Every gram of nitrate-N converted to nitrogen gas saves 2.86 g of oxygen in terms of CBOD 5 removal.…”

Nonlinear Adaptive Control of Heat Transfer Fluid Temperature in a Parabolic Trough Solar Power Plant

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