The Denitrifying Deep Bed Filter (DDBF™) is a wastewater treatment process of the Poseidon Filtration System®. It provides fixed‑film biological denitrification in a downflow filter configuration. With proper chemical treatment, the DDBF™ is capable of meeting stringent effluent limits of total nitrogen as low as 3 mg/l, total suspended solids to 2 mg/L, and total phosphorus to 0.3 mg/L or less.
In the DDBF™, denitrifying organisms attach to the filter media. Supplemental carbon is augmented to the filter influent to drive the denitrification process. Wastewater flows around nitrogen gas bubbles that accumulate in the media and reduce the space between sand grains, which improves biomass contact and filtration efficiency.
Orthos’ Centurion™ structurally-superior filter underdrains feature nozzles with solid-expelling slots, specifically‑sized to retain the DDBF™ media and prevent biological fouling. No gravel layer is necessary, which reduces hydraulic profile and eliminates related horizontal short‑circuiting.
A backwash cycle is initiated when the nitrogen release cycle no longer reestablishes sufficient headloss, filter effluent rate is minimized, or the filter run maximum time is reached. Backwash frequency for the DDBF™ is comparable to that of a conventional filter.
After backwash, reduced denitrification performance may initially occur for several minutes due to biomass loss. Thus, more DDBF™ cells are typically designed than for a conventional filter arrangement in order to produce the required blended effluent nitrogen concentration.
Orthos’ compound loop algorithm of feed-forward and feedback with effluent concentration control delivers required effluent quality with no carbon increase through the DDBF™.
Ortho-Wash™ filter controls may be either split-flow/ constant-level or variable-level. Constant-level operation prevents influent cascade, minimizing DO and its related carbon addition expense, whereas variable-level typically provides longer run times.