Fate and Removal of Steroidal Hormones during Advanced Municipal Biosolids Treatment Processes

This research evaluates the fate of 16 steroidal (estrogenic, androgenic and progestogenic) hormones during advanced anaerobic digestion of municipal sludge cake produced at the Kelowna's wastewater treatment plant using microwave (MW) pretreatment. Effect of sludge pretreatment temperature (80, 120, 160°C), digester operating temperature (mesophilic at 35 ± 2°C, thermophilic at 55 ± 2°C) and sludge retention time (SRT: 20, 10, 5 days) were studied employing eight lab-scale semi-continuously fed digesters. To determine the potential effect of MW hydrolysis, hormones were quantified in sludge (total) and supernatant (soluble) phases of the digester influent and effluent streams. Seven of 16 hormones were above reporting limit (RL) in one or more of the samples. MW hydrolysis resulted in both release and attenuation of hormones in the soluble phase. High accumulations (upto 30 times of the influent concentration) of hormones were observed in the effluents suggesting that anaerobic digestion was inefficient to remove these compounds. Pretreatment by MW also increased total chemical oxygen demand (TCOD), volatile solids (VS) removals and methane production compared to unpretreated (control) digesters, especially at the shortest SRT (5 days).