Comparison of Microcontaminants and Net Estrogen Activity of Anaerobically Treated Mixed Municipal Sludge

The estrogen activity associated with aqueous extracts of biosolids, to simulate runoff from biosolids application sites, was investigated in this study. The biosolids were generated from mixed municipal sludge treated by a conventional anaerobic digester (AD) and an anaerobic membrane bioreactor (AnMBR) operating over a range of conditions at pilot scale. The qualities of the aqueous extracts were assessed in terms of the presence of a suite of environmentally relevant microcontaminants and using the in-vitro yeast estrogen screen bioassay (YES). There did not appear to be any identifiable relationships between the digester configuration and operating conditions and YES responses of the biosolids extracts. The frequency of occurrence of MCs in the extracts of the biosolids from the AnMBR reactor appeared to be greater than that of the conventional anaerobic digester. The findings suggest that estrogenicity, as measured by the in-vitro YES bioassay associated with the presence of microcontaminants, persists during anaerobic digestion of mixed municipal sludges. Further the YES bioassay may be used as a metric to evaluate the quality of treated sludge to assess its estrogenic potential. The findings of this study will inform policy makers and operating agencies on the potential estrogenic effect from microcontaminants that can desorb into the aqueous runoff from land applied biosolids and potentially impact non-target organisms in the natural environment. Further work on the sensitivity and robustness of the application of the YES metric is recommended.