Influence of low and high dosages of methyl and propyl parabens on membrane bioreactor (MBR) performance.

This study aimed to evaluate the degradation of methylparaben (MeP) and propylparaben (PrP) in synthetic wastewater in a membrane bioreactor (MBR) whose operation involved three stages: stage 1 (stabilization period), with no addition of parabens; stage 2, in which the MBR was fed with 0.5 mg L−1 of each paraben; and stage 3, in which both MeP and PrP were added, at 10 mg L−1each. The system performance was assessed by monitoring pH, temperature, effluent flow rate, transmembrane pressure, BOD, COD, suspended solids, and paraben concentration. The results confirmed that the MBR showed a good organic matter removal efficiency (> 92.2% for BOD; >91.6% for COD) and was not significantly affected by the addition of parabens at either low or high dosages. The volatile to total suspended solids ratio remained nearly constant, suggesting that the addition of parabens at a high concentration did not negatively impact the control of suspended solids. It was possible to achieve 96.0% of MeP and PrP removal in stage 2 ([parabens]0 = 0.5 mg L−1), and 86.0% of PrP removal in stage 3 ([PrP]0 = 10 mg L−1). Finally, biodegradation was found to be the main removal mechanism of parabens in the investigated MBR. [ABSTRACT FROM AUTHOR]