The organic loading rate affects organic micropollutants’ cometabolic biotransformation kinetics under heterotrophic conditions in activated sludge

Kennes-Veiga, David M.; González-Gil, Lorena; Carballa, Marta; Lema, Juan M.

doi:10.1016/j.watres.2020.116587

Cited by 39 publications

(13 citation statements)

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“…On the other hand, Kennes‐Veiga et al. did not observe a difference in OMP removal efficiency by increasing acetate concentrations in a continuous bioreactor (Kennes‐Veiga et al ., 2020). Instead, they only reported increasing biodegradation rate constants with increasing acetate loads.…”

Section: Resultsmentioning

confidence: 99%

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Rios‐Miguel

Jetten

Welte

2021

Microbial Biotechnology

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Pharmaceuticals are often not fully removed in wastewater treatment plants (WWTPs) and are thus being detected at trace levels in water bodies all over the world posing a risk to numerous organisms. These organic micropollutants (OMPs) reach WWTPs at concentrations sometimes too low to serve as growth substrate for microorganisms; thus, co-metabolism is thought to be the main conversion mechanism. In this study, the microbial removal of six pharmaceuticals was investigated in a membrane bioreactor at increasing concentrations (4-800 nM) of the compounds and using three different hydraulic retention times (HRT; 1, 3.5 and 5 days). The bioreactor was inoculated with activated sludge from a municipal WWTP and fed with ammonium, acetate and methanol as main growth substrates to mimic co-metabolism. Each pharmaceutical had a different average removal efficiency: acetaminophen (100%) > fluoxetine (50%) > metoprolol (25%) > diclofenac (20%) > metformin (15%) > carbamazepine (10%). Higher pharmaceutical influent concentrations proportionally increased the removal rate of each compound, but surprisingly not the removal percentage. Furthermore, only metformin removal improved to 80-100% when HRT or biomass concentration was increased. Microbial community changes were followed with 16S rRNA gene amplicon sequencing in response to the increment of pharmaceutical concentration: Nitrospirae and Planctomycetes 16S rRNA relative gene abundance decreased, whereas Acidobacteria and Bacteroidetes increased. Remarkably, the Dokdonella genus, previously implicated in acetaminophen metabolism, showed a 30-fold increase in abundance at the highest concentration of pharmaceuticals applied. Taken together, these results suggest that the incomplete removal of most pharmaceutical compounds in WWTPs is dependent on neither concentration nor reaction time. Accordingly, we propose a chemical equilibrium or a growth substrate limitation as the responsible mechanisms of the incomplete removal. Finally, Dokdonella could be the main acetaminophen degrader under activated sludge conditions, and non-antibiotic pharmaceuticals might still be toxic to relevant WWTP bacteria.

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Section: Resultsmentioning

confidence: 99%

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Rios‐Miguel

Jetten

Welte

2021

Microbial Biotechnology

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show abstract

“…Thus, a specific growth substrate concentration might be able to support only partial biotransformation of pharmaceuticals in WWTPs. On the other hand, Kennes-Veiga et al did not observe a difference in OMP removal efficiency by increasing acetate concentrations in a continuous bioreactor (Kennes-Veiga et al, 2020). Instead, they only reported increasing biodegradation rate constants with increasing acetate loads.…”

Section: Pharmaceutical Removal At Different Hydraulic Retention Timesmentioning

confidence: 93%

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Rios‐Miguel

Jetten

Welte

2021

Preprint

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Pharmaceuticals are often not fully removed in wastewater treatment plants (WWTPs) and are thus being detected at trace levels in water bodies all over the world posing a risk to numerous organisms. These organic micropollutants (OMPs) reach WWTPs at concentrations sometimes too low to serve as growth substrate for microorganisms, thus co-metabolism is thought to be the main conversion mechanism. In this study, the microbial removal of six pharmaceuticals was investigated in a membrane bioreactor at increasing concentrations (4-800 nM) of the compounds and using three different hydraulic retention times (HRT; 1, 3.5, 5 days). The bioreactor was inoculated with activated sludge from a Dutch WWTP and fed with ammonium, acetate, and methanol as main growth substrates to stimulate and mimic co-metabolism in a WWTP. Each pharmaceutical compound had a different average removal efficiency: acetaminophen (100%) > fluoxetine (50%) > metoprolol (25%) > diclofenac (20%) > metformin (15%) > carbamazepine (10%). Higher pharmaceutical influent concentrations proportionally increased the removal rate of each compound, but surprisingly not the removal percentage. Furthermore, only metformin removal improved to 80-100% when HRT or biomass concentration was increased in the reactor. Microbial community changes were followed with 16S rRNA gene amplicon sequencing in response to the increment of supplied pharmaceutical concentration: it was found that Nitrospirae and Planctomycetes 16S rRNA relative gene abundance decreased, whereas Acidobacteria and Bacteroidetes increased. Remarkably, the Dokdonella genus, previously implicated in acetaminophen metabolism, showed a 30-fold increase in abundance at the highest (800 nM) concentration of pharmaceuticals applied. Taken together, these results suggest that the incomplete removal of most pharmaceutical compounds in WWTPs is neither dependent on concentration nor HRT. Accordingly, we propose a chemical equilibrium or a growth substrate limitation as the responsible mechanisms of the incomplete removal. Finally, Dokdonella could be the main acetaminophen degrader under activated sludge conditions, and non-antimicrobial pharmaceuticals might still be toxic to relevant WWTP bacteria.

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“…4,10,109 Research on the link between bulk organic carbon metabolism and OMP biotransformation is missing. 112 In the following, we review the OMP biotransformation by isolated aerobic ammonia oxidizers together with other functionally important N-converting microorganisms, in order to shed light on their importance for OMP biotransformation in complex microbial communities.…”

Section: ■ Omp Biotransformations In Pure Cultures Of N-converting Mi...mentioning

confidence: 99%

“…Under aerobic conditions, some HAB may also contribute to cometabolic OMP biotransformation as they harbor enzymes like oxygenases or peroxidases − and can generate highly reactive oxygen-containing radicals, like •O 2 – , hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (•OH) . However, the abundance and significance of heterotrophic cometabolic enzymes in WWTPs is essentially unexamined, − while the removal of OMPs through primary metabolism by HAB is assumed minimal. ,, Research on the link between bulk organic carbon metabolism and OMP biotransformation is missing . In the following, we review the OMP biotransformation by isolated aerobic ammonia oxidizers together with other functionally important N-converting microorganisms, in order to shed light on their importance for OMP biotransformation in complex microbial communities.…”

Section: Omp Biotransformations In Pure Cultures Of N-converting Micr...mentioning

confidence: 99%

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations

Schittich

Jensen

et al. 2021

Environ. Sci. Technol.

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Organic micropollutants (OMPs) are a threat to aquatic environments, and wastewater treatment plants may act as a source or a barrier of OMPs entering the environment. Understanding the fate of OMPs in wastewater treatment processes is needed to establish efficient OMP removal strategies.Enhanced OMP biotransformation has been documented during biological nitrogen removal and has been attributed to the cometabolic activity of ammonia oxidizing bacteria (AOB) and, specifically, to the ammonia monooxygenase (AMO) enzyme. Yet, the exact mechanisms of OMP biotransformation are often unknown. This review aims to fundamentally and quantitatively evaluate the role of ammonia oxidation in OMP biotransformation during wastewater treatment processes. OMPs can be transformed by AOB via direct and indirect enzymatic reactions: AMO directly transforms OMPs primarily via hydroxylation, while biologically produced reactive nitrogen species (hydroxylamine (NH2OH), nitrite (NO2 − ) and nitric oxide (NO)) can chemically transform OMPs through nitration, hydroxylation and deamination and can contribute significantly to the observed OMP transformations. OMPs containing alkyl-, aliphatic hydroxyl-, ether-, and sulfide functional groups as well as substituted aromatic rings and aromatic primary amines can be biotransformed by AMO, while OMPs containing alkyl groups, phenols, secondary amines and aromatic primary amines can undergo abiotic transformations mediated by reactive nitrogen species.Higher OMP biotransformation efficiencies and rates are obtained in AOB-dominant microbial communities, especially in autotrophic reactors performing nitrification or nitritation, than in non-AOB-dominant microbial communities. The biotransformations of OMPs in wastewater treatment systems can often be linked to ammonium (NH4 + ) removal following two central lines of evidence:(i) similar transformation products (i.e. hydroxylated, nitrated and desaminated TP) are detected in wastewater treatment systems as in AOB pure cultures; (ii) consistency in OMP biotransformation (rbio, µmol/g VSS/d) to NH4 + removal (rNH4+, mol/g VSS/d) rate ratios (rbio/rNH4+) are observed for 3 individual OMPs across different systems with similar rNH4+ and AOB abundances. In this review, we conclude that AOB are the main driver of OMP biotransformation during wastewater treatment processes. The importance of biologically driven abiotic OMP transformation is quantitatively assessed and functional groups susceptible to transformations by AMO and reactive nitrogen species are systematically classified. This review will improve the prediction of OMP transformation and facilitate the design of efficient OMP removal strategies during wastewater treatment.

show abstract

The organic loading rate affects organic micropollutants’ cometabolic biotransformation kinetics under heterotrophic conditions in activated sludge

Cited by 39 publications

References 50 publications

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Role of Ammonia Oxidation in Organic Micropollutant Transformation during Wastewater Treatment: Insights from Molecular, Cellular, and Community Level Observations

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