Enzyme response of activated sludge to a mixture of emerging contaminants in continuous exposure.

Georgiana Amariei,Karina Boltes,Roberto Rosal,Pedro Leton,Ilaria Corsi

doi:10.1371/journal.pone.0227267

Abstract

The relevant information about the impacts caused by presence of emerging pollutants in mixtures on the ecological environment, especially on the more vulnerable compartments such as activated sludge (AS) is relatively limited. This study investigated the effect of ibuprofen (IBU) and triclosan (TCS), alone and in combination to the performance and enzymatic activity of AS bacterial community. The assays were carried out in a pilot AS reactor operating for two-weeks under continuous dosage of pollutants. The microbial activity was tracked by measuring oxygen uptake rate, esterase activity, oxidative stress and antioxidant enzyme activities. It was found that IBU and TCS had no acute toxic effects on reactor biomass concentration. TCS led to significant decrease of COD removal efficiency, which dropped from 90% to 35%. Continuous exposure to IBU, TCS and their mixtures increased the activities of glutathione s-transferase (GST) and esterase as a response to oxidative damage. A high increase in GST activity was associated with non-reversible toxic damage while peaks of esterase activity combined with moderate GST increase were attributed to an adaptive response.

Highlights

Pharmaceuticals and personal care products (PPCP) are one of the most relevant group of emerging pollutants because of their worldwide detection in practically all environmental compartments and their adverse biological effects [1,2,3]
Performance, oxygen respiration rate, viability and microbial enzymatic activity were investigated in activated sludge (AS) reactors continuously exposed to IBU and TCS, alone and in combination, for 14 days, and the results related to the oxidative stress suffered by bacterial cells
IBU had no significant impact on reactor performance, while TCS led to significant decrease of chemical oxygen demand (COD) removal efficiency

Summary

Introduction

Pharmaceuticals and personal care products (PPCP) are one of the most relevant group of emerging pollutants because of their worldwide detection in practically all environmental compartments and their adverse biological effects [1,2,3]. PPCP includes many active substances, some of which, like antibiotics and antiseptics, target bacteria and can affect other microorganisms [4]. Most PPCP reach the environment through industrial, hospital, and household wastewaters, which are discharged as effluents of wastewater treatment plants (WWTP) to receiving bodies [5,6,7,8,9,10]. WWTP represent the final defense for preventing PPCP from discharging into water environments, but the rate of biodegradation in conventional AS processes is low for most of these compounds [11]. AS processes are designed to remove chemical oxygen demand (COD), nutrient substances and pathogens, but not to deal with emerging

Methods

Results

Conclusion