Quantification of Denitrification Potential in Carbonaceous Trickling Filters

Abstract

Biofilm samples from a carbonaceous trickling filter were evaluated in bench scale reactors to determine their maximum potential denitrification rates. The samples were collected as intact, undisturbed biofilms by inserting clean microscope slides into the trickling filter at various locations, leaving them in place for 28 days, and then removing them and bringing them back to the laboratory. In the laboratory, they were placed into 0.6 L bench-scale reactors filled with sterilized, primary clarifier effluent that had been spiked with nitrate to a final concentration of 16-18 mg/L as N. Dissolved oxygen (D.O.) concentrations were maintained between 2 and 4 mg/L in the bulk aqueous phase to simulate conditions within the full-scale system. Nitrate loss from the reactors was monitored over a five hour period. Denitrification rates of 3.09 to 5.55 g-N/m 2 ·d were observed with no initial lag period. This suggests that the capacity for denitrification is inherent in the biofilm and that denitrification can take place in the deeper layers of the biofilm even when oxygen is present at significant concentrations in the bulk aqueous phase. There were no significant differences in denitrification rates per unit area of media (g-N/m 2 ·d) either between (a) experimental runs or (b) sampling locations over the TF. This suggests that denitrification potentials are uniform over the entire volume of the full-scale TF. For wastewater treatment plants with TFs that currently nitrify downstream, recycle flows may be used to remove nitrate in their existing upstream TFs. This approach may be used to meet less stringent permitted discharge concentrations and may allow some facilities to postpone or eliminate construction of additional unit processes for denitrification.

Catalytic Denitrification in a Trickle Bed Reactor: Ion Exchange Waste Brine Treatment

“…TBRs are often characterized by high gas‐to‐liquid mass transfer rates and are used extensively in a variety of industrial applications—i.e., petroleum processing, oxidation reactions, and hydrogenation reactions (Ranade et al 2011a, Al‐Dahhan et al 1997). One form of a TBR—i.e., the trickling filter or biofilter—is common in wastewater treatment and used for biological nitrification (Parker & Richards 1986) to remove organic matter (Satterfield 1975) and, more recently, for biological denitrification (Biesterfeld et al 2003). The authors are unaware of any catalytic TBR used for drinking water purification in the United States.…”

Spatially distributed denitrification in a karst springshed

“…This mixing could effectively decouple the local measured redox state from the conditions where denitrification occurred. Alternatively, local reduction zones in microbial biofilms on aquifer substrates may have created favourable conditions where transformations could occur locally despite high DO concentrations in the bulk aquifer, as was observed by Biesterfeld, Farmer, Figueroa, Parker, and Russell () and Henson et al ().…”

Nitrate reduction mechanisms and rates in an unconfined eogenetic karst aquifer in two sites with different redox potential

“…Mass balance methods for DNRA and Bio‐N accumulation due to ANRA in recovered porewater cannot explain all observed nitrate reduction in the PPTT experiments (Figure ). Although some N functional genes were not detected in the recovered porewater this does not preclude their presence in microbial mats on aquifer substrates or surfaces where many nitrogen transformations can occur [ Sexstone et al ., ; Biesterfeld et al ., ; Macalady et al ., ; Sahl et al ., ; Gray and Engel , ]. Together, this suggests that microbial biofilms may be a significant location of nitrate reduction through denitrification, ANRA, or DNRA.…”

“…Together, this suggests that microbial biofilms may be a significant location of nitrate reduction through denitrification, ANRA, or DNRA. This finding is not unexpected, biofilms on aquifer material have been found to be a significant location of biogeochemical reactions [ Holm et al ., ; Hancock et al ., ; Macalady et al ., ; Zhang et al ., ], and significant N reduction in biofilms has been detected even under high DO conditions [ Biesterfeld et al ., ; Chang et al ., ]. Observed nitrate reduction at the oxic site, where porewater conditions are unfavorable for denitrification and DNRA further supports that observed nitrate reduction occurred in aquifer biofilms.…”