Calculator Inputs
Enter process, geometry, and design assumptions. The layout shows three columns on large screens, two on medium screens, and one on mobile.
Example Data Table
Illustrative design case for checking the calculator workflow.
| Flow (m³/day) | Influent BOD (mg/L) | Target BOD (mg/L) | Disk Diameter (m) | Disks/Stage | Stages | Total Area (m²) | Required Area (m²) | Estimated Effluent (mg/L) | Status |
|---|---|---|---|---|---|---|---|---|---|
| 450 | 220 | 30 | 3.6 | 120 | 4 | 9,380.60 | 8,938.00 | 20.58 | Meets target |
Formula Used
1) Projected Disk Area
Aprojected = πD² / 4
2) Effective Wetted Area per Disk
Adisk = Aprojected × 2 × fmedia × fsubmergence
3) Total Media Area
Atotal = Adisk × Ndisks/stage × Nstages
4) BOD Removal Required
Lremove = Q × (Sin − Sout,target) / 1000
5) Temperature-Corrected Flux
FT = F20 × θ(T−20) / SF
6) Required Media Area
Arequired = 1000 × Lremove / FT
7) Estimated Effluent from Available Capacity
Sestimated = Sin − (Atotal × FT / Q)
This page uses a practical preliminary sizing method based on media area and areal removal capacity. Final design should still be checked against pilot data, local standards, oxygen transfer, nutrient balance, and secondary clarification limits.
How to Use This Calculator
- Enter the average wastewater flow in cubic meters per day.
- Enter the influent BOD concentration and the target effluent BOD.
- Provide disk geometry, disk count per stage, and number of stages.
- Set submergence and media surface factor for the selected media type.
- Enter the allowable BOD removal flux at 20°C.
- Adjust temperature coefficient and safety factor for local conditions.
- Optionally enter rotor speed to estimate disk tip speed.
- Press the calculate button to display summary results above the form.
- Review stage profile, summary table, and design adequacy message.
- Use the CSV or PDF buttons to export the calculation package.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates RBC media area, loading rates, required BOD removal, corrected areal flux, expected effluent concentration, stage profile, and whether the proposed arrangement meets the target.
2) Why is submergence included?
Only the submerged portion of the rotating media is wetted at any moment. Submergence changes the active contact area and therefore affects removal capacity and hydraulic loading.
3) What is the media surface factor?
It scales projected disk area into effective developed surface area. Structured or corrugated media expose more biofilm surface than a smooth flat disk.
4) Why apply a temperature correction?
Biological reaction rates change with temperature. The correction factor adjusts the allowable removal flux above or below the reference condition of 20°C.
5) Is the stage graph a full process simulation?
No. It is a practical stage profile derived from the overall estimated performance. It helps compare stage-by-stage concentration decline during preliminary design.
6) Can I use COD instead of BOD?
Use caution. The equations are arranged for BOD-based sizing. COD may be used only when your design basis, removal flux, and permit limits are all COD-based.
7) What if the calculator shows extra area needed?
Increase stage count, add disks, enlarge disk diameter, select higher-surface media, or review the allowable flux with validated site data before finalizing equipment size.
8) Does meeting the target guarantee final compliance?
No. Final compliance also depends on flow variation, temperature swings, nutrient balance, clarifier performance, sludge handling, oxygen transfer, and operating discipline.