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MBBR Design — Carrier & Nitrification Area

Moving-bed biofilm reactors size by protected biofilm area, not by MLSS. Set the flow, nitrogen and BOD loads, carrier type and fill fraction — get the required carrier volume, reactor size and HRT, with the temperature correction that makes MBBR such a good tropical retrofit.

1Duty & carrier

Design by the binding load — nitrification area or organic area — whichever needs more carrier.

Avg flow Q^[1] (1k–500k)m³/d

Carrier^[2]

TKN_inf^[1] (30–70)mg/L

NH₃-N_eff^[1] (2–10)mg/L

BOD_inf^[1] (150–400)mg/L

Temp T^[3] (15–34)°C

Fill fraction ∅^[1] (0.35–0.67)%

r_A,20^[3] (0.5–1.2)gN/m²·d

Results — carrier & reactor

Carrier volume

—m³

Reactor volume

—m³

HRT

—h

Item	Value	Basis

2Load vs capacity

The binding constraint sets the carrier. Tropical water lifts both rates via the θ correction.

Parameter	Load	Capacity

Order note

Quote the MBBR instruments at factory price

An MBBR needs DO, NH₃-N, temperature, level and flow — plus a mag flowmeter on the recirculation. We supply them at the manufacturer's ex-works price; our margin is the export tax rebate only.

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Sources & parameter basis

[1]	Ødegaard / AnoxKaldnes design guides — MBBR by protected biofilm area; fill 35–67 % (design ~40–50 %); K1 a≈500, K3 a≈650, high-area a≈800 m²/m³.
[2]	Carrier catalogue — specific surface area a (protected) 500–800 m²/m³ depending on type.
[3]	Area-specific nitrification r_A ≈ 0.5–1.0 g N/m²·d at 20 °C; temperature θ ≈ 1.05–1.10 (r_A(T)=r_A20·θ^(T−20)). Organic r_BOD20 ≈ 15 g/m²·d, θ_B≈1.04.

Full derivation and worked example: MBBR-Calculation-Sheet.md. MBBR is the compact, retrofit-friendly biological variant — size the carrier, then carry the effluent into the clarifier tool.

How is the MBBR carrier fill fraction chosen?

The carrier fill fraction is an input that trades off biofilm area against tank volume, and the calculator uses it together with the carrier specific surface area to size the reactor.

Why does temperature change the nitrification rate?

Nitrification slows in cold water, so the area-specific rate is temperature dependent; the calculator corrects it to the operating temperature before it sizes the protected biofilm area.

How much protected biofilm area is required?

The required area comes from the nitrification load divided by the temperature-corrected area-specific rate, so the area matches the load at your actual temperature.

How do carrier volume and reactor size follow from that?

Carrier volume is derived from the required area and the specific surface area of the media, and the reactor size follows from that volume - the calculator returns the full chain.

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1Duty & carrier

Results — carrier & reactor

2Load vs capacity

Order note

Quote the MBBR instruments at factory price

Sources & parameter basis

Cite this tool / 引用此工具

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