Effect of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part I: biofilm growth and activity

摘要

Two similar anaerobic fixed-bed bioreactors which allowed the biomass to be periodicallywithdrawn were run in parallel. After feeding each digester with synthetic dairy wastes of different lipidcontent (Period I), both digesters were fed with increasing sodium oleate concentrations with skim milkas co-substrate (Period II) and oleate as the sole carbon source (Period III). In Period I, the digesterfed with lipids was more effcient and exhibited lower levels of volatile fatty acids than the digester fedwithout lipids. The biofilm built up in the presence of lipids was thinner, but more resistant to thepresence of oleate than the biofilm formed in the absence of lipids, which lost 53% of its solids aftercontacting with oleic acid. The specific methanogenic activity with butyrate as substrate was enhancedin the presence of lipids, but no significant effect was detected on the acetoclastic and hydrogenophilicactivities, which remained similar for both digesters along the trial period.