Abstract
This study covers three widely detected non-steroidal anti-inflammatory pharmaceuticals (NSAIDs), diclofenac (DCF), ibuprofen (IBP) and naproxen (NPX), as NSAIDs pollutants. The objective is to evaluate the impact of NSAIDs at their environmental concentrations on microbial community assembly and activity. The exposure experiments were conducted under three conditions (5 μg L-1 DCF, 5 μg L-1 DCF+5 μg L-1 IBP and 5 μg L-1 DCF+5 μg L-1 IBP+ 5 μg L-1 NPX) in sequencing batch reactors (SBRs) for 130 days. Removals of COD and NH4+-N were not affected but total nitrogen (TN) removal decreased. IBP and NPX had the high removal efficiencies (79.96% to 85.64%), whereas DCF was more persistent (57.24% to 64.12%). In addition, the decreased removals of TN remained the same under the three conditions (p > 0.05). The results of oxidizing enzyme activities, live cell percentages and extracellular polymeric substances (EPS) indicated that NSAIDs damaged the cell walls or microorganisms and the mixtures of the three NSAIDs increased the toxicity. The increased Shannon-Wiener diversity index suggested that bacterial diversity was increased with the addition of selected NSAIDs. Bacterial ribosomal RNA small subunit (16S) gene sequencing results indicated that Actinobacteria and Bacteroidetes were enriched, while Micropruina and Nakamurella decreased with the addition of NSAIDs. The enrichment of Actinobacteria and Bacteroidetes indicated that both of them might have the ability to degrade NSAIDs and thereby could adapt well with the presence of NSAIDs.
Highlights
The non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs worldwide
The results indicated that environmentally relevant concentrations of selected NSAIDs stimulated superoxide dismutase (SOD) activity, suggesting that the three NSAIDs could induce the oxidative stress of microorganisms in activated sludge
The results of the ratio of Live/Dead cell and oxidizing enzymes activities provided that environmental concentrations of selected NSAIDs caused toxicity to microbial communities, and the mixtures of three NSAIDs improved the toxicity
Summary
The non-steroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs worldwide. Diclofenac (DCF), ibuprofen (IBP) and naproxen (NPX) are frequently detected in the environment as trace emerging contaminants [1]. DCF has been in the watch list of compounds in EU and had already harmfully affected several environmental species at concentration of < 1 μg L-1 [2]. IBP usually has the highest influent concentrations. Impact of selected pharmaceuticals on microorganism analysis, decision to publish, or preparation of the manuscript
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