Annual dynamics of antimicrobials and resistance determinants in flocculent and aerobic granular sludge treatment systems. (15th February 2021)

• Record Type: Journal Article
• Authors: Pallares-Vega, Rebeca; Hernandez Leal, Lucia; Fletcher, Benjamin N.; Vias-Torres, Eduardo; van Loosdrecht, Mark C.M.; Weissbrodt, David G.; Schmitt, Heike
• Is Part Of: Water research. Volume 190(2021)
• Publication Date: 2021-02-15
• Subjects: WWTP -- ARGs -- Antibiotics -- Granular sludge -- Rainfall -- Temperature; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.116752
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Warmer temperatures decreased influent ARGs concentrations but increased E. coli's. Rainfall diluted influent concentrations of antimicrobials & E. coli, but not ARGs. Rainfall reduced the efficiency of wastewater treatment in removing ARGs & E. coli. ARGs patterns in flocculent activated sludge followed influent trends. Similar removal of antimicrobial & ARGs by granular and flocculent sludge systems. Abstract: The occurrence and removal patterns of 24 antimicrobial agents and antimicrobial resistant determinants namely 6 antibiotic resistance genes (ARGs) and 2 mobile genetic elements (MGEs), and the fecal indicator E. coli were investigated in three full-scale wastewater treatment plants. Their waterlines and biosolids lines (including secondary treatment based on both granular and activated sludge) were sampled monthly throughout one year. Samples were analyzed by means of LC-MS/MS, qPCR and cell enumeration, respectively. The influence of rainfall, temperature, and turbidity on the occurrence and removal of the aforementioned agents was assessed through statistical linear mixed models. Ten of the antimicrobial agents (macrolides, fluoroquinolones, tetracyclines, and sulfonamides) were commonly found in influent in concentrations of 0.1-2 µg L −1, and the predominant ARGs were ermB and sul1 (6.4 and 5.9 log10 mL −1 respectively). Warmer temperatures slightly reduced gene concentrations in influent whilst increasing that of E. coli and produced an uneven effect on the antimicrobial concentrations across plants. Rainfall diluted both E. coli (-0.25 logs, p < 0.001) and antimicrobials but not genes. The wastewater treatment reduced the absolute abundance of both genes (1.86 logs on average) and E. coli (2.31 logs on average). The antimicrobials agents were also partly removed, but 8 of them were still detectable after treatment, and 6 accumulated in the biosolids. ARGs were also found in biosolids with patterns resembling those of influent. No significant differences in the removal of antimicrobials, genes and E. coli were observed when comparing conventional activated sludge with aerobic granular sludge. Irrespective of the type of sludge treatment, the removal of genes was significantly reduced with increasing hydraulic loads caused by rainfall (-0.35 logs per ∆ average daily flow p < 0.01), and slightly decreased with increasing turbidity (-0.02 logs per ∆1 nephelometric turbidy unit p < 0.05) . Graphical abstract: Image, graphical abstract