Abstract
A moving bed biofilm reactor (MBBR), where biomass is attached to small carrier elements that move freely along with the water in the reactor, has been tested for organic matter removal at five different organic loading rates. A lab-scale reactor with a volume of 2L was built and fed continuously with synthetic wastewater. The reactor was filled with the Kaldnes biomedia K1 which is used in the patented Kaldnes Moving Bed™ biofilm process at 50% of the volume of empty reactor. Hydraulic retention times (HRT) in the reactor and in the settler were adjusted to between 8 and 4 hours, respectively. A start-up period of about 4 weeks for biofilm growth on the carrier was followed by 10 weeks of testing period. By changing the wastewater composition, the operation of the system was adjusted, one after the other, to five different organic loading rates: 6, 12, 24, 48 and 96 g COD/m2 .d. Organic removal efficiency decreased with increasing organic loading rate, ranging from 95.1%, 94.9%, 89.3%, 68.7% and 45.2% as the organic loading rate was increased form 6 to 96 g COD/m2 .d. In the MBRR reactor, the biofilm reached an average concentration of 3.28 kg TSS/m3 at the highest organic loading rate. The ratio between the TSS production and the total COD removal was 0.12 kg TSS/kg total COD at an influent total COD of 500 mg/l.