Environmental fate assessment of two synthetic polycarboxylate polymers

In order to estimate the proportion which may enter the aquatic environment and characterize exposure potential, the environmental fate properties of two polycarboxylate polymers in activated sludge were determined. The polycarboxylates studied were a polymer emulsion (PE), a high-molecular-weight polymer (MW 50,000-60,000), and a resin polymer (RP), a low-molecular-weight polymer (MW 4500 to 9000). Both polymers exhibited a high degree of sorption to sludge solids in a series of sorption/ desorption studies, indicating a high potential for removal during wastewater treatment. In isotherm tests, the adsorption coefficient, Koc, was 1060 and 2730 for the RP and the PE, respectively. The biodegradation of the two polymers was measured under aerobic conditions in a 60-day semicontinuous activated sludge test and in a 60-day modified Sturm test using 14C-labeled compounds. In both studies, polymers accumulated in sludge solids over time and there was no evidence of significant biodegradation, although small amounts of radiolabeled CO2 were produced, suggesting the potential for biodegradation. Testing confirmed that the lack of biodegradation was not due to inhibition of microbial respiration by the polymers. High removals of PE and RP during wastewater treatment were confirmed in a field study at a facility receiving polymer inputs from households and manufacturing plants.