New operational support system for high nitrogen removal in oxidation ditch process

A new operational support system for the oxidation ditch process has been developed. It calculates the operational index from the concentration of the dissolved oxygen in the ditch and the operator decides the aeration conditions to keep the index within the target range. Simulation and experimental results have led to creation of an operational index with an optimum value for every type of aeration. For example, the ratio of aerobic to anaerobic zone length (L_AER/L_ANA ratio) is for the 1-point continuous aeration process, the ratio of aerobic to anaerobic duration time (T_AER/T_ANA ratio) is for the 2-point intermittent aeration process and so on. Their optimum values are all 1, suggesting that the ratio of denitrification to nitrification rates is around 1 under typical conditions of the general oxidation ditch process. These indexes are very practical because they can be obtained without complex calculation.