Impact of selected non-steroidal anti-inflammatory pharmaceuticals on microbial community assembly and activity in sequencing batch reactors

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.