Ecotoxicological hazard assessment of two polymers of distinctively different molecular weights.

Assessment of ecological risks during manufacturing, use, transport, and disposal are becoming increasingly important as planning tools during development of new products. The objective of this study was to establish the potential ecotoxicological hazard associated with two polycarboxylate polymers in water, sludge, sediment, and soil. The concentrations of both polymers were quantified using 14C-radiolabeled synthesis and liquid scintillation counting (LSC). The program included water column acute and chronic exposures with Ceriodaphnia dubia, Pimephales promelas, and Selenastrum capricornutum, sediment exposures with Chironomus riparius, and soil exposures with Eisenia foetida. Sludge treated with either polymer, from a semicontinuous activated sludge unit, was used to evaluate the effect on growth of five plants. The hazard assessment program for both polymers indicated a very low order of toxicity as defined by the U.S. EPA and OECD. Very small fractions of each polymer may not be removed by waste treatment and could accumulate in sediments, but should not pose a significant risk because of their low toxicity to benthic organisms. Terrestrial testing demonstrated that soil needs to be saturated with these chemicals to produce adverse effects. Bioaccumulation potential for both polymers was extremely low. Use of these polymers does not appear to pose a significant risk to the environment, based on their low inherent toxicity.

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.