Full-Scale Methanol Optimization at a Step-Feed BNR Demonstration Facility

摘要

A study at a 25-mgd full-scale, four pass step-feed BNR treatment plant was carried out tooptimize supplemental carbon addition. The study began with methanol addition to all fourpasses, which showed that carbon addition was only needed in the final two passes (Passes C andD) to achieve optimal denitrification. Further optimization to single-point (Pass D) carbonaddition revealed that at low methanol doses, the traditional denitrification theory significantlyover estimated the actual denitrification (nitrate removal) seen in the full-scale plant by 65%.Denitrification theory over-predicted methanol-driven nitrate removal by 900 lbs, with only 230lbs being removed by methylotrophs. When the methanol dose was doubled, the amount ofnitrate removal that was expected from the increased dose was achieved (～1,130 lbs), yet the65% short-fall (900 lbs of nitrate) seen at the lower dose was still observed indicating that themethanol denitrification kinetics at the low methanol dose do not accurately predict nitrateremoval in this high rate system.