Sequential Nitrification-denitrification Process using Biofilter Reactor for the Removal of Chemical Oxygen Demand and Nitrogen for Tofu Wastewater Treatment

Abstract

This study aims to optimize the sequential performance of a nitrification-denitrification (ND) biofilter reactor for nitrogen removal from tofu industry wastewater. The study also supports the Indonesian government’s policy to achieve the Sustainable Development Goals through the implementation of sustainable water management in Indonesia. Seeding and acclimatization were conducted at hydraulic retention times (HRTs) of 24, 12, and 6 hours. During nitrification, removal efficiency improved with increasing substrate concentration at a 24-hour HRT. At 100% substrate concentration (915 mg/L), chemical oxygen demand (COD) removal increased until day 19, reaching a maximum of 77.95% at pH 7.3. The maximum ammonia nitrogen (NH₃–N) removal was 86.95% at pH 7.3. However, COD removal efficiency dropped below 70% when the HRT was reduced to 12 and 6 hours at both 50% and 100% substrate concentrations. At a 24-hour HRT, the denitrification reactor achieved 83.25% NH₃–N and 67.55% COD removal, while nitrate removal reached 90.75%. Proper HRT was directly related to nitrate removal efficiency, and higher influent nitrate concentrations tended to increase the denitrification rate. The highest nitrate removal efficiency (90.75%) occurred at a 24-hour HRT and pH 7.8