Across the United States, there is a rapidly growing awareness of the occurrence and the toxicological impacts of natural and synthetic trace compounds in the environment. These trace compounds, referred to as emerging contaminants (ECs), are reported to cause a range of negative impacts in the environment, such as adverse effects on biota in receiving streams and interference with the normal functions of the endocrine system, which controls growth and development in living organisms.

Wastewater treatment plants (WWTPs) have been identified as a key collection point for ECs in the water cycle and potentially an ideal location at which to treat to remove them, thereby mitigating their release into the environment (Figure 1). This presents wastewater industry professionals with both a significant opportunity and a tremendous challenge: to identify cost effective treatment processes that can remove or reduce these contaminants before they are released into the environment.

Although WWTPs have been identified as strategic focal points and potential treatment locations for the removal of ECs from the environment, little is known about the nature, variability, transport and fate of this class of compounds in typical wastewaters and treatment facilities in the United States. Furthermore few studies have been performed to monitor or understand the capability of conventional or innovative wastewater treatment processes to remove or reduce the concentrations of a wide variety of ECs at wastewater facilities.

This study was designed to provide baseline information on this topic. While other studies have examined the occurrence of a limited number of representative contaminants in the environment (generally five to 10 compounds), this study is unique in that it provides information on a comprehensive list of ECs (63 ECs in total, Contaminant List in Appendix A, not included here) in the wastewater collection and treatment systems for four diverse communities over a two-year period. (It should be noted that the study is ongoing and additional data are pending but only 18 months of data are presented in this paper).

The study was conducted in two phases. Phase 1 was designed to provide information concerning the general character and concentration of ECs commonly detected in wastewaters, the variability over a prolonged period of time, the transport and fate of ECs through typical wastewater treatment plants operating with a range of conventional technologies and the impact of WWTP discharges on receiving streams. It also provided guidance in understanding the capability of distinct wastewater treatment processes or technologies to reduce or remove ECs.

The second phase of the study focused on one of the most common wastewater treatment processes operated in the United States, the Activated Sludge process. Using four controlled parallel activated sludge pilots, a more detailed assessment of the impact of Sludge Retention Time (SRT) on the reduction or removal of ECs was performed.