Evaluation of Sulfide-driven Autotrophic Denitrification in a Moving Bed Biofilm Reactor

Abstract

While the 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. Autotrophic denitrification using reduced sulfur compounds could be a low yield alternative to conventional heterotrophic denitrification to polish effluent nitrate. Three lab-scale MBBRs (using sulfide, methanol and ethanol as electron donor sources) were operated continuously at 12°C. The performance of each reactor was monitored by weekly sampling and batch rate profile testing. Sulfide visually exhibited biofilm carrier biomass content similar to or slightly less than that of methanol, yet provided increased removal rates (1.1±0.5 versus 0.6±0.3 g NO X -N/m 2 /day, respectively.) SDNR profile testing also suggested that maximum NO X -N removal rates for sulfide (1.8 g NO X -N/m 2 /day) were more than three times that of methanol (0.57 g NO X -N/m 2 /day.) Although the sulfide reactor produced the highest removal rates, significant uncertainties must be addressed prior to full-scale implementation.

Mass Transfer Characteristics of Floating Media in MBBR and IFAS Fixed-Film Systems

“…Tap water was used to provide a source of trace elements. The tap water residual chlorine was removed by bubble aeration for 24 hours (h) following the addition of 1.5 mg/L sodium bisulfite (NaHSO 3 ) (Bill et al, 2010). Net concentrations of the synthetic feed (as added to the reactor after mixing with water) are shown in Table 4-2.…”

“…Most of the high G values are associated with plants operating at high oxygen uptake rates. For comparison, a recent study of mechanical mixing (with an impeller) in laboratoryscale MBBRs included experiments that were conducted over the range from 50/s to 253/s (Bill et al, 2010).…”