Denitrification in a methanol-fed fixed-bed reactor. Part 1: Physico-chemical and biological characterization

In a municipal two-stage biological wastewater treatment plant with full nitrification, methanol-fed post-denitrification was investigated in a succeeding sand filter system originally designed for the retention of suspended solids in the secondary effluent. Temperature, pH, redox potential, concentration of oxygen and nitrogen-compounds and gas production were determined in situ in the filter bed. In addition, biological parameters such as volatile solids, biofilm thickness, and nitrate elimination efficiency of denitrifying bacteria isolates were determined. The data characterize the microbial processes underlying denitrification in the filter cells and support operation optimization by avoiding detrimental effects on denitrification efficiency such as accumulation of biomass, pH drop and accumulation of undesired intermediates such as nitrite and nitrous oxide.