Evaluation of Alternative Electron Donors in Anoxic Moving Bed Biofilm Reactors (MBBRs) Configured for Post-Denitrification

The effectiveness of four different electron donors, specifically methanol, ethanol, glycerol, and sulfide, was evaluated in post-denitrifying bench-scale moving bed biofilm reactors (MBBRs). With increased concern for wastewater treatment plants to meet lower effluent nitrogen levels, alternate substrates could promote quicker startup/acclimation times and higher denitrification rates than methanol, which is most commonly used. While application of alternative substrates in suspended growth processes has been studied extensively, fixed film post denitrification processes have been designed to use primarily low yield substrates like methanol. Preliminary results indicate that ethanol and glycerol both provide consistent denitrification, with average COD consumption factors of 0.96 and 1.07 at assumed anoxic yield values of 0.5 and 0.55, respectively. Both ethanol and glycerol have shown substantially shorter acclimation times and much higher removal rates at 20°C than either methanol or sulfide.