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.
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.
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.
