Trickling Filter Designer

Design a single-stage trickling filter by the NRC equations. Enter the design flow, the influent (post-primary) BOD and the target effluent BOD, plus the recirculation ratio and filter depth — the app finds the recirculation factor, the required volume, area & diameter, the organic and hydraulic loading rates, and the BOD-removal efficiency achieved.

⭐ Free to use · Balance … EP

① Flow & BOD loading

Design flow Q (m³/day)

Wastewater flow to the filter (after primary).

Influent BOD₅ S₀ (mg/L)

BOD entering the filter (after primary settling).

Target effluent BOD₅ S_e (mg/L)

Required BOD leaving the filter → sets efficiency.

Filter depth (m)

Rock media commonly 1.5–3 m (1.83 m = 6 ft).

② Recirculation

Recirculation ratio R = Q_r / Q

Recycled flow ÷ design flow. Use 0 for no recirculation.

Max organic loading (kg BOD/m³·day)

Optional check vs a typical limit (low-rate ≈ 0.08–0.4).

NRC (SI): E = 100 / (1 + 0.4432·√(W/(V·F))) with recirculation factor F = (1+R)/(1+R/10)², where W = BOD load (kg/day) and V = filter volume (m³).

🦠 Trickling filter design

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Single-stage NRC trickling filter

Loading & efficiency

Required efficiency

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BOD load W

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Recirculation factor F

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Filter dimensions

Required volume

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Surface area

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Diameter

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Depth

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Loading-rate checks

Organic loading

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Hydraulic loading

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Effluent BOD

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Worked solution

⚠️ Verify before design. The NRC equations assume specific media, temperature and conditions; loading limits and effluent targets are typical design figures. Final media type, depth, number of stages and effluent standards must follow DENR DAO 2016-08, accepted texts (Davis & Cornwell / Metcalf & Eddy), and your course references. This tool is a study/estimating aid.