Dynamic Control of the Activated Sludge Process Utilizing Oxidation Reduction Potential

Unpredictable nature for the flow and quality of livestock wastewater is the problem usuallyoccurred in the treatment process. This study tried to solve this problem using the onlinemonitoring ORP to control the inflow of the activated sludge process. The influent was startedpumping into the aeration tank when ORP of the system reached the upper operational limit, andpumping was stopped when ORP dropped to the lower operational limit. Therefore, the adverseeffect of variable inflow would be lessened.

In order to determine the optimal operational criteria, both MLSS and ORP range were selectedas the experimental parameters. There were 9 sets of experiments were conducted in this study:three ORP ranges for each designated MLSS were chosen: 130~100 mV, 130~80 mV, 130~60mV (MLSS 7000 mg/L); 130~110 mV, 130~90 mV, 130~70 mV (MLSS 5000 and 3000 mg/L).Additionally, One set of parameter were selected and long term operation were then conductedfor observing the stability of the system performance after the above 9 sets of experiment werefinished.

The experimental results showed that 94% and 95% of COD and SS removal efficiencies, F/M of0.295 g/g-d, and the shortest HRT of 1.23 days were achieved when operated at MLSS of 7000mg/L and ORP range of 130~100 mV. Also, it was found that higher MLSS concentration andreducing the ORP operational range would improve the system performance and increase theremoval efficiency. The results of long term operation showed that the control strategydeveloped of this study was feasible.