BIODEGRADATION OF ACRYLIC-ACID POLYMERS AND OLIGOMERS BY MIXED MICROBIAL COMMUNITIES IN ACTIVATED-SLUDGE

The biodegradability (mineralization to carbon dioxide) of acrylic aci d oligomers and polymers was studied in activated sludge obtained from continuous-flow activated sludge (GAS) systems exposed to mixtures of low molecular weight (Mw < 8000) poly(acrylic acid)s and other water- soluble polymers [poly(ethylene glycol)s] in influent wastewater. Dilu te preparations of activated sludge from the CAS units were tested for their ability to mineralize acrylic acid monomer and dimer, as well a s a series of model acrylic acid oligomers and polymers (Mw 500, 700, 1000, 2000, and 4500), as sole carbon and energy sources. Complete min eralization of acrylic acid monomer and dimer was observed in low-biom ass sludge preparations previously exposed to the polymer mixture, bas ed on carbon dioxide production and residual dissolved organic carbon analyses. Extensive (though incomplete) degradation was also observed for the low molecular weight acrylic acid oligomers (Mw 500 and 700), but degradation dropped off sharply for the 1000, 2000, and 4500 Mw po lymers. Radiochemical (C-14) data also confirmed the low degradation p otential of the 1000, 2000, and 4500 Mw materials. Degradation of two commercial poly(ethylene glycol)s at 1000 and 3400 Mw was complete and comparable to that of the acrylic acid monomer and dimer. Our results indicate that mixed populations of activated sludge microorganisms ca n extensively metabolize acrylic acid oligomers of seven units or less . Complete mineralization, however, could be confirmed only for the mo nomer and dimer material, and carbon mass balance data suggested that the true molecular weight cutoff for complete biodegradation was signi ficantly less than the 500-700 Mw range tested.