Effect of ibuprofen on extracellular polymeric substances (EPS) production and composition, and assessment of microbial structure by quantitative image analysis

Abstract

A Sequencing Batch Reactor (SBR) with activated sludge was operated with synthetic wastewater containing ibuprofen (IBU) to investigate the biomass stress-responses under long-term IBU exposure. There were 3 different phases: phase I as the control without IBU for 56 days, phase II (40 days), and phase III (60 days) containing IBU at 10 and 5 mg L − 1 each. The overall performance of the SBR as well as the extracellular polymeric substances (EPS) in terms of polysaccharides, proteins, and humic acid substances were estimated. Morphological parameters of microbial aggregates in the presence of IBU (phase II and phase III) were assessed by quantitative image analysis (QIA). Removal efficiencies of chemical oxygen demand (COD) and ammonium (NH 4 + ) were significantly reduced by IBU. Loosely bound EPS (LB-EPS) decreased during phase II and phase III, and tightly bound EPS (TB-EPS) was slightly higher in phase II than phase I. TB-EPS proteins were greater in phase II, perhaps to protect microbial cells from IBU exposure. These findings provided insight into both activated sludge stress-responses and EPS composition under long-term IBU exposure. Spearman correlation showed that EPS and morphological parameters significantly affected sludge settleability and flocculation. QIA also proved to be a powerful technique in investigating dysfunctions in activated sludge under IBU exposure.

Effects of desloratadine on activated sludge: Behaviour of EPS and sludge properties

“…In this work, a sequencing batch reactor (SBR) with a working volume of 2 L was inoculated with AS from a full-scale WWTP and fed with synthetic wastewater (the composition can be found in [23]). The initial mixed liquor suspended solids (MLSS) in the system was ca.…”

“…Quantification of chemical oxygen demand (COD), ammonium (NH 4 + -N), nitrite (NO 2 − -N), and nitrate (NO 3 − -N) was performed as described by Melo et al [23]. MLSS, mixed liquor volatile suspended solids (MLVSS), and the sludge volume index at 30 min (SVI) were determined in accordance with standard methods [24].…”

The Role of Extracellular Polymeric Substances in Micropollutant Removal

“…Large amounts of DNA in the EPS may indicate that the cells suffered cell lysis during the rigorous extraction process (Liu and Fang, 2002). Besides, amphiphilic compounds (phospholipids), glycosylated proteins (glycoproteins), and HAS have also been shown to appear in significant amounts or even predominate in EPS preparations from AS, trickling filter biofilms, and anammox granular sludge (Boleij et al, 2018;Oliveira et al, 2020;Liu et al, 2021;Melo et al, 2021). Additionally, HAS are constituted of complex heterogeneous mixtures of organic compounds, such as polyaliphatic and poly-aromatic compounds, containing carboxylic, phenolic, and hydroxyl, which give a highly negative charge.…”

“…For instance, Shen et al (2020) found that EPSt production decreased with a bulking phenomenon. Furthermore, the research work of Melo et al (2021) revealed that, despite the poor floc structure, the rising in EPS content, especially TB-EPS, was the critical point to reaching an AS with wellsettling ability properties. In turn, PN and DNA content in EPS seems to have more significant effects on the settling ability of microbial aggregates, presenting a positive relationship with SVI, and it was not possible to establish a relationship between PS and SVI (Sheng et al, 2010).…”

“…Changes in microbial aggregates' structure have been associated with the variation in EPS composition and production (Melo et al, 2021). Furthermore, a positive correlation between EPS components (PS, PN, and HAS) and large aggregation formation has been found, suggesting that high levels of biopolymers produced by biomass influence the size of the aggregates (Melo et al, 2021).…”