Competition between planktonic and fixed microorganisms during the start-up of methanogenic biofilm reactors.
The influence of the hydraulic retention time (HRT) on the start-up phase of a methanogenic inverse turbulent bed bioreactor was investigated. Two identical reactors were monitored, the only differing parameter being the HRT: one of the reactors was fed with a diluted wastewater at a constant HRT of 1 day, the organic loading rate (OLR) being increased by decreasing the substrate dilution; the second reactor was fed at a constant influent concentration of 20 g COD L(-1), the OLR being increased by decreasing the HRT from 40 days to 1 day. After 45 days of start-up, both reactors were operated at an OLR of 20 g COD L(-1)d(-1) and a HRT of 1 day. However, strong differences were observed on biofilm growth. In the reactor operated at a constant short HRT, biofilm concentration was 4.5 as high as in the reactor operated at an increasing HRT. This difference was attributed to the competition between planktonic and biofilm microorganisms in the latter reactor, whereas suspended biomass was quickly washed out in the former reactor because of the low HRT.
Cresson
Romain
R
Laboratoire de Biotechnologie de l'Environnement, INRA, UR050, Avenue des Etangs, Narbonne F-11100, France.
Escudié
Renaud
R
Steyer
Jean-Philippe
JP
Delgenès
Jean-Philippe
JP
Bernet
Nicolas
N
D000693:Anaerobiosis; D018441:Biofilms; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D010933:Plankton / Q000502:physiology*; D014865:Waste Disposal, Fluid / Q000379:methods*