ERY exhibited the greatest adverse effect on both MPA and SRB, emphasizing the risk to wastewater biological treatment containing ERY. The concentration of ERY in this study was not analyzed but McArdell et al. (2003) reported that ERY was not removed during aerobic processes. However, a more recent paper found 67% removal rate in an anaerobic multi-chamber bed reactor (Celebi and Sponza, 2009). These results indicated that anaerobic treatment may be more efficient in eliminating ERY.