Moving bed biofilm reactor sized by the biofilm area it holds. The surface area loading rate, chosen by what the reactor is for, fixes the carrier area; the carrier's protected surface and the fill fraction turn it into a volume:
A=TASQS0V=fenchasA
| Goal | BOD5 loading (g/(m².d)) | Soluble BOD5 removal | Sludge (kg TSS/kg BOD5 removed) |
|---|---|---|---|
| High rate (roughing, ahead of further treatment) | 20 | 75 % | 0.70 |
| Normal rate (BOD removal) | 10 | 85 % | 0.50 |
| Low rate (ahead of nitrification) | 5 | 90 % | 0.35 |
| Carrier | Protected surface (m²/m³) |
|---|---|
| K1, K3 | 500 |
| K5 | 800 |
| BiofilmChip M | 1200 |
Typical values at the design temperature; the carrier supplier's are better. Fill above about 70 % stops the carriers moving freely. When ammonia to nitrify is given, the area for nitrification at its surface rate is compared and the larger governs; nitrification develops on the carriers only at a low organic load.
Oxygen by the COD balance, as in the activated sludge blocks, plus nitrification:
RO=fCrem−1.42SSTSSVPx+4.57QNox
An MBBR has no clarifier of its own: the influent solids and the biomass that sloughs off the carriers leave with the effluent, and the effluent suspended solids reported are what the next unit receives.
ØDEGAARD, H. Innovations in wastewater treatment: the moving bed biofilm process. Water Science and Technology, v. 53, n. 9, p. 17-33, 2006.
METCALF & EDDY. Wastewater Engineering: Treatment and Resource Recovery. 5th ed. McGraw-Hill, 2014. Chapter 9 (attached growth processes).