Suchergebnisse

AbstractExisting heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual‐media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen‐sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen‐sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

AbstractHydraulic performance issues in drinking‐water biofilters have sometimes been associated with phosphorus limitation and increased production of extracellular polymeric substances in previous bench‐scale studies. However, field studies utilizing phosphorus supplementation to improve biofilter hydraulic performance have produced mixed results. Here, we determined the ratio of activities for phosphatase to glycosidase (PHO:GLY), which are enzymes involved in acquiring orthophosphate and biodegradable organic carbon from complex organic substrates, to assess phosphorus limitation in 21 pilot‐ and full‐scale biofilters. Supplementation of the pilot‐scale biofilter influents with 37 μg/L orthophosphate‐P reduced the PHO:GLY from 1.8–40.3 (mean 14.8) to 0.3–15.9 (mean 5.3), demonstrating that increased orthophosphate availability decreases PHO:GLY. In the absence of phosphorus supplementation, the PHO:GLY of the pilot‐ and full‐scale biofilters ranged from 0.3 to 40.3 (mean 10.1), and no hydraulic performance issues were noted. Thus, severe phosphorus limitation appears uncommon in the field, suggesting that phosphorus supplementation is unlikely to improve hydraulic performance in typical drinking water biofilters.