Raschig rings offer an effective tertiary denitrification solution with rates ten to fifteen times greater than traditional systems for producing nitrogen and carbon dioxide at once. This process is particularly suitable for wastes containing high concentrations of calcium and ammonium as they produce nitrogen at significantly faster rates than previous systems.
Friedrich Raschig invented these cylindrical packings made of metal or glass for efficient distillation. When used in a column, materials that are harder to evaporate fall downward while easily evaporateable material rises – this allows production of nitrogen and carbon gases without multiple stages.
Each polypropylene raschig ring was incubated with a nitrate solution of similar composition to that found in waste to be denitrified, in an aquarium-style cylindrical glass column. By monitoring effluent quality and microbial mass during incubation, it was confirmed that denitrification rates remained consistent over the course of incubation whereas with anthracite coal packing the denitrification rate was less.
The difference in performance between these two nitrate solutions may be attributable to lower availability of reducing equivalents released by wood chips as they decompose, as well as any delays between when an environment with high nitrate concentration is introduced and denitrification starting; and perhaps due to needing denitrifying bacteria to adapt and get used to different carbon sources.