EFFECTS OF REACTOR CONFIGURATION AND BIOMASS ACTIVITY ON THE PERFORMANCE OF UPFLOW STATIC MEDIA ANAEROBIC REACTORS

Three upflow, static-media anaerobic reactors (US-MARs), each with clean-bed volumes of 85 L but with different heights: diameter ratios were operated at 35-degrees-C, with COD loadings varying from 1 to 12 g/L.d. Height-to-diameter ratios investigated were 1.2, 4.1, and 14.3. The reactors were fed a synthetic substrate made from nonfat dry milk and minerals. It was hypothesized that the effect of biogas mixing on reactor performance would be greater in tall reactors than in short ones. This was found not to be the case. Based on COD removal, the tall reactor performed only slightly better than the shorter ones at loadings less than 9 g/L.d. At higher COD loadings, there was no significant difference in performance. Tracer studies using lithium chloride indicated a completely mixed flow regime at COD loadings in excess of 9 g/L.d. The acetogenic methanogenic activity of the VSS in all reactors varied between 0.1 and 0.2 L CH4/g VSS.d at reactor VSS concentrations higher than 1000 mg/L.