Process modeling and energy optimization of a full scale advanced biological wastewater treatment plant in Istanbul

When standard design methods are applied directly to projects, they can lead to serious design errors. Due to the low nitrification growth rate in Istanbul, treatment plants generally cannot meet total nitrogen discharge standards. During the study, an innovative treatment process was discovered. The pilot plant with "Biofilm Nitrification - Contact Denitrification System" and the real plant were operated simultaneously and their performances were compared. In the pilot plant, the return sludge was sent to the reactive pre-sedimentation tank and 80 per cent of the organic matter was removed without the use of chemicals. Another advantage of this system is that nitrification in the hybrid system is less affected by inhibition because it occurs in a separate biofilm reactor. Nitrogen removal performance was also improved. Since the organic matter settled in the preliminary clarifier is sent directly to the denitrification tank, it is not exposed to aerobic conditions and therefore there is no loss of organic matter. Sending the organic matter first to nitrogen removal and then to biogas production is another advantage of this process. Modeling studies have shown that a higher amount of biogas can be obtained from anaerobic digestion of this sludge. The hybrid system was found to have lower operating costs (i.e., 9% less air and 39% less energy required for mixing). It also requires 40% less volume than other BNR systems, resulting in significantly lower capital costs. Therefore, the new hybrid configuration was found to be a more efficient and attractive option for treating wastewater.