Start up of UASB reactors treating sucrose‐containing substrates with a low cod/sulfate ratio

The performance during the start up of two identical UASB reactors (UASB = Upflew Anaeribic Sludge Bed) of 23, 5 liters was studied to determine the effeet of a high sulfate concentration. A synthetic, sucrose=containing substrate (3000 mg COD/l) with COD/sulfate ratios of 5 and 100 respectively (w/w) was fed to two the reactors, The space leading rate could be increased to a value of 10 g COD, l=1,day=1 for both reactors. The mean sulfate reduction amounted to 95=99%, and no toxic levels of hydrogen sulfide could be detested. After 157 days of operation only a minority of the sludge in the reastors was growing in distinct agglomerates. Because of a positive influence of a lower COD/nitrogen ratio in the influent of both reactors on the reacter performance, the maintenance of a concentration of ammonia, supplied as a nitrogen source, of mere than 100 mg:l=1 in the influent of anaerobic reactors can be recommended.