Standardized application of yeast bioluminescent reporters as endocrine disruptor screen for comparative analysis of wastewater effluents from membrane bioreactor and traditional activated sludge.

A standardized protocol is demonstrated for bioluminescent strains Saccharomyces cerevisiae BLYES, BLYAS and BLYR as high-throughput screening tools to monitor the estrogenic, androgenic and toxic potencies in wastewater. The sensitivity and reproducibility of the assay in wastewater monitoring was evaluated for 7 day semi-continuous batch reactor using activated sludge with hormones spiked raw sewage. Yeast bioluminescent assay successfully captured the rapid removal of estrogenic and androgenic activities in the bioreactors, and demonstrated rapid response (≤4 h) with good reproducibility. This standardized protocol was then applied in a 12 months monitoring of the effluent of a WWTP located at Powell, TN, USA featuring parallel-operated full-scale membrane bioreactor (MBR) and traditional activated sludge (TAS) treatment. Monitoring results showed that estrogenic activity was persistent in all TAS and most MBR effluent samples, while residual androgenic activity was non-detectable throughout the monitored period. The estrogenic equivalents (EEQ) in TAS effluent ranged from 21.61 ng/L to 0.04 pg/L and averaged 3.25 ng/L. The EEQ in MBR effluent ranged from 2.88 ng/L to 0.0134 pg/L and averaged ~10 fold less (0.32 ng/L) than TAS. Despite the large temporal variation, MBR effluent EEQ was consistently lower than TAS on any given sampling date. Most MBR effluent samples also exhibited less cytotoxicity than TAS. Further analysis did not demonstrate significant correlation between effluent EEQ level and WWTP operational parameters including MLSS, SRT, HRT and BOD.