Presentation Abstract

Pharmaceuticals and Personal Care Products as Environmental Contaminants (2): Biodegradability Studies and Occurrence in Sewage Treatment Plant Influent and Effluent
Jim Yu, Kevin Bisceglia, Ed Bouwer, Mehmet Coelhan, and A. Lynn Roberts
Johns Hopkins University, Baltimore, MD

The two major objectives for this research project are to: (1) examine the biodegradability of selected pharmaceuticals and antiseptics; and (2) study the occurrence and removal of selected pharmaceuticals and antiseptics in wastewater influents and effluents.

For examining the biodegradability of acidic pharmaceuticals and personal care products (PPCPs), batch biodegradation experiments have been conducted. Different electron acceptors, microbial inocula, and PPCP concentrations were investigated to elucidate the biodegradability of PPCPs under different environmental conditions.

The occurrence and removal of these PPCPs has been investigated in different sewage treatment plants (STPs) located in the Northeastern seaboard of the United States. These STPs employ different treatment processes and operational characteristics (e.g., different solid residence times and different nutrient removal processes). Quadruplicate 24-hour composite influent and effluent samples were obtained at each site, and U.S. Environmental Protection Agency Method 526 guidelines were followed for quality assurance and quality control in analyzing wastewater samples.

For aerobic biodegradation experiments, 13 of the 18 PPCPs tested underwent extensive (> 80%) biotransformation after 50 days of incubation. Anaerobic conditions (nitrate reducing and iron reducing) seemed to be less favorable for biodegradation of pharmaceuticals. All antiseptics were biotransformed under all testing conditions, whereas phenytoin, 5-fluorouracil, and diclofenac did not biodegrade readily. In general, aerobic conditions were more favorable for biotransformation than anaerobic conditions, and i ron-reducing conditions were the least favorable. Experiments with different microbial inocula generally showed little difference in the aerobic biotransformation of different PPCPs, even though the inocula comprised very different microbial communities. A naerobic microbial communities (nitrate vs. iron reducing) revealed some difference in biodegradability for a few compounds. Experiments with varying initial concentration showed little influence on the extent of biotransformation. By understanding the biodegradability of the target PPCPs, human and ecosystem risks resulting from the presence of these compounds in aquatic systems can be established further.

The majority of the target analytes were detected in the STP influents. Influent concentrations of PPCPs varied between geographic locations, potentially reflecting regional differences in drug usage. The removal efficiencies for different PPCPs also varied from treatment plant to treatment plant, depending on the specific treatment processes and operational characteristics, although incomplete removals were observed for many compounds. Overall, the majority of the target analytes were detected in both the influent and effluent STP streams at ng/L levels, although some PPCPs (e.g., naproxen and ibuprofen) were encountered at µg/L levels.

After reviewing all occurrence and removal data from STPs, a plant will be chosen for further detailed study. This research project will encompass a mass balance study on this single wastewater treatment plant to determine the removal efficiencies of each unit process. Samples will be taken at the influent and effluent of each unit processes to provide further insight on the removal of PPCPs in STPs.

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