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

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.

SUBMITTER: Amariei G

PROVIDER: S-EPMC6957336 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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

Amariei Georgiana G Boltes Karina K Rosal Roberto R Leton Pedro P

PloS one 20200113 1

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 po ...[more]

PMID: 31931513

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Project description:Understanding ecosystem response to disturbances and identifying the most critical traits for the maintenance of ecosystem functioning are important goals for microbial community ecology. In this study, we used 16S rRNA amplicon sequencing and metagenomics to investigate the assembly of bacterial populations in a full-scale municipal activated sludge wastewater treatment plant over a period of 3 years, including a 9-month period of disturbance characterized by short-term plant shutdowns. Following the reconstruction of 173 metagenome-assembled genomes, we assessed the functional potential, the number of rRNA gene operons, and the in situ growth rate of microorganisms present throughout the time series. Operational disturbances caused a significant decrease in bacteria with a single copy of the rRNA (rrn) operon. Despite moderate differences in resource availability, replication rates were distributed uniformly throughout time, with no differences between disturbed and stable periods. We suggest that the length of the growth lag phase, rather than the growth rate, is the primary driver of selection under disturbed conditions. Thus, the system could maintain its function in the face of disturbance by recruiting bacteria with the capacity to rapidly resume growth under unsteady operating conditions.IMPORTANCE Disturbance is a key determinant of community assembly and dynamics in natural and engineered ecosystems. Microbiome response to disturbance is thought to be influenced by bacterial growth traits and life history strategies. In this time series observational study, the response to disturbance of microbial communities in a full-scale activated sludge wastewater treatment plant was assessed by computing specific cellular traits of genomes retrieved from metagenomes. It was found that the genomes observed in disturbed periods have more copies of the rRNA operon than genomes observed in stable periods, whereas the in situ mean relative growth rates of bacteria present during stable and disturbed periods were indistinguishable. From these intriguing observations, we infer that the length of the lag phase might be a growth trait that affects the microbial response to disturbance. Further exploration of this hypothesis could contribute to better understanding of the adaptive response of microbiomes to unsteady environmental conditions.

Project description:IntroductionSimultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood.MethodsBatch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism.ResultsExperimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress.DiscussionThese findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Dataset Information

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

Publications

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

Similar Datasets

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