FORMATION OF SOLUBLE MICROBIAL PRODUCTS DURING ANAEROBIC TREATMENT

Stock (fill-and-draw) reactors and chemostats (CSTR) fed acetate and g lucose were used to investigate the production of soluble microbial pr oducts (SMP) during anaerobic treatment. These reactors were maintaine d at solids retention times (SRT) from 15 to 56 days with organic load ing rates (OLR) from 0.18 to 0.50 g chemical oxygen demand (COD)/L . d . Results showed that longer SRTs resulted in higher levels of SMP, wi th SMP ranging from 17 to 59 mg COD/L when acetate was the sole carbon and energy source and 50 to 291 mg COD/L when glucose was the substra te. Normalized production of SMP (SMP/influent COD = SMP/S-o) ranged f rom 0.2% to 1.0% for acetate reactors and 0.6% to 2.5% for glucose rea ctors. Steady-state results from chemostats fed glucose showed that as SRT increased, SMP/S-o decreased to a minimum and then increased, ind icating the existence of an optimal operating SRT that would result in a minimum normalized production of SMP. Effluent soluble COD was most ly SMP; the fraction of effluent soluble COD made up of SMP increased with increasing SRT. Production of SMP from glucose reactors was model ed. Normalized production of SMP during anaerobic treatment appears to be lower when compared with aerobic production of SMP reported in the literature.