Oxidation Ditch (Carrousel / Orbal) Design
1Duty & reactor
Results — reactor & oxygen
| Item | Value | Basis |
|---|
2DO zoning & nitrification
| Zone | Volume | DO target |
|---|
Aerator / rotor duty
| Item | Value | Basis |
|---|
Quote the ditch instruments at factory price
An oxidation ditch is instrument-dense: DO per channel, ORP in the anoxic zone, MLSS, NH₃-N, NO₃-N, level and flow. We supply them at the manufacturer's ex-works price — margin from the export rebate only.
Request a quote for this duty ← Primary Clarifier Secondary Clarifier →Sources & parameter basis
| [1] | Metcalf & Eddy / U.S. EPA — oxidation ditch: HRT 10–40 h, MLSS 2–5 g/L, F/M 0.05–0.15 kg/kg·d, SRT 15–30 d; Orbal 3-channel, Carrousel anoxic selector. |
| [2] | Nitrification SRT via Q₁₀=2: SRTₙ(T)=SRTₙ(20)·2^((20−T)/10), SRTₙ(20)≈3 d [WEF MOP-8]. |
| [3] | Oxygen: carbon 0.9 kg O₂/kg BOD removed; nitrification 4.57 kg O₂/kg N; denitrification −2.86 kg O₂/kg N; biomass credit 1.42 kg O₂/kg VSS (VSS≈0.3·BOD removed). |
| [4] | Rotor/brush OAE ≈ 1.0–1.5 kg O₂/kWh (Orbal brush ~1.2, Carrousel rotor ~1.5); SAE for blowers 1.8–2.5. |
How do I size an oxidation ditch tank?
Tank volume comes from the HRT you want together with the MLSS you intend to hold, and the calculator returns the volume for the design flow so the retention matches the biology.
What F/M and oxygen demand does an oxidation ditch need?
The calculator returns the F/M ratio and the oxygen demand for the load you enter, and rotor power follows from that demand.
How should DO be zoned between anoxic and aerobic sections?
The ditch is zoned by dissolved oxygen - anoxic where nitrate is recycled, aerobic where carbon is oxidised - and the calculator shows the DO zoning for the split you enter.
How does temperature affect the nitrification SRT check?
Nitrification slows in cold water, so the required SRT rises as temperature falls; the calculator flags the design when the temperature-driven SRT is not met, which matters for tropical plants.