PRODUCTION AND INHIBITANT-AFFECTED UTILIZATION OF BUTYRIC-ACID IN ANAEROBIC-DIGESTION PROCESS

The fates of both forms of butyric acid (HBu) in anaerobic digesters w ere discussed. HBu production was investigated by using glucose as the substrate in continuous feeding digestion at 35 degrees C at pH 5.7, 6.4 and 6.9 and at the SRTS (solid retention times) of 2.5, 2.0, 1.5, 1.0, 0.5 and 0.25 days. Production of n-HBu increased with increasing SRT. No production of i-HBu was determined at SRT > 2.0 days when the pH was low. Inhibitant effect on the utilization of HBu were investiga ted by batch test at 35 degrees C. The CSTR seed sludge digesters were continuously fed with n-HBu or i-HBu, and the SRT were 20,14,10,6,5 a nd 20,14,10,8,7,6 days, respectively. In the batch test, the acclimate d sludge (SRT 10 days) was used. Isomerization between n-HBu and i-HBu wa evident from the experimental results but the isomerization of i-H Bu was readily affected by oleate, sulfate or ammonia. The relative to xicities were oleate much greater than sulfate > ammonia for the utili zation of both forms of HBu.