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.

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The Nansemond Treatment Plant (NTP) operated by the Hampton Roads Sanitation District (HRSD) has experienced sporadic nitrification for a number of years, and some indication of continuous nitrification inhibition, as demonstrated by calibration of a process simulation model to historical data. A study was undertaken using a wide variety of NTP, targeted industry, and control wastewater and biomass samples to evaluate, understand, and identify sources of inhibition through batch rate measurements, profile sampling and process simulation modeling. Using plant performance data, a calibrated dynamic model was generated over the period of profile samples and compared to the profile sampling data to better estimate the level of continuous nitrification inhibition. Experimental results confirmed the sporadically inhibitory nature of NTP primary effluent when combined with other nitrifying biomasses. Based on this work, there was definitely some degree of continuous nitrification inhibition characterized by an apparent reduction in $2% ȝ max .

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