Biosolids for safe land application: does wastewater treatment plant size matters when considering antibiotics, pollutants, microbiome, mobile genetic elements and associated resistance genes?

Abstract

Soil fertilization with wastewater treatment plant (WWTP) biosolids is associated with the introduction of resistance genes (RGs), mobile genetic elements (MGEs) and potentially selective pollutants (antibiotics, heavy metals, disinfectants) into soil. Not much data are available on the parallel analysis of biosolid pollutant contents, RG/MGE abundances and microbial community composition. In the present study, DNA extracted from biosolids taken at 12 WWTPs (two large-scale, six middle-scale and four smallscale plants) was used to determine the abundance of RGs and MGEs via quantitative real-time PCR and the bacterial and archaeal community composition was assessed by 16S rRNA gene amplicon sequencing. Concentrations of heavy metals, antibiotics, the biocides triclosan, triclocarban and quaternary ammonium compounds (QACs) were measured. Strong and significant correlations were revealed between several target genes and concentrations of Cu, Zn, triclosan, several antibiotics and QACs. Interestingly, the size of the sewage treatment plant (inhabitant equivalents) was negatively correlated with antibiotic concentrations, RGs and MGEs abundances and had little influence on the load of metals and QACs or the microbial community composition. Biosolids from WWTPs with anaerobic treatment and hospitals in their catchment area were associated with a higher abundance of potential opportunistic pathogens and higher concentrations of QACs.

Quaternary Ammonium Compounds: A Chemical Class of Emerging Concern

“…Levels in sludge and biosolids as high as 500 mg/kg (dry weight) have been measured. ,− The presence of QACs in soils could arise from amendment with QAC-containing biosolids, as well as from direct use as surfactants in pesticide/herbicide formulations. QACs have also been detected in soil irrigated with municipal wastewater .…”

Antibiotic resistomes and microbial communities in biosolid fertilizers collected from two Canadian wastewater treatment plants in a 10-years interval-potential risks to food chains?

“…Further LDA effect size-based cladogram showed Proteobacteria and Planctomycetes phyla, especially Planctomycetacia class, enriched in biosolid sample from 2019, while bacterial species enriched in biosolid samples collected from 2009 were taxa in the Spirochaetae phylum and Actinobacteria class (Figure 2E). The bacterial communities inhabiting biosolid collected from WWTPs can vary between different treatment facilities over time, due to the differences in treatment procedures between various facilities and the sources of WWTP influents (Yergeau et al, 2016;de Celis et al, 2020;Wolters et al, 2022). However, interestingly, given the fact that there is no significant differences in antibiotic resistome between these two facilities (Figure 1D), observation of significantly different microbiota compositions between these two facilities indicated potential ARG transfer between different bacterial species or existence of large amount of cell-free ARGs in biosolids.…”

Antibiotic concentrations in raw hospital wastewater surpass minimal selective and minimum inhibitory concentrations of resistant Acinetobacter baylyi strains

“…2014) as well as in treated sewage sludge (Wolters et al . 2022) and, on the other hand, strains affiliated to this genus were reported from vegetables, meat and livestock (Al Atrouni et al . 2016).…”

“…Experimental MSCs for bacterial species have been published for a number of systems, however, with a strong focus on Enterobacterales, e.g., for E. coli and S. enterica harboring resistance genes or chromosomal mutations (Gullberg et al 2011;Klümper et al 2019), for the evolution of resistance in mutator strains of S. enterica (Wistrand-Yuen et al 2018), horizontal gene transfer into E. coli (Jutkina et al 2016), or with a focus on complex communities, e.g., the selection of resistance genes in wastewater communities (Lundström et al 2016;Kraupner et al 2018;Murray et al 2018;Stanton et al 2020). So far, to our knowledge, there is no experimental system that examines the effects of low antibiotic concentrations on species of other bacterial orders.…”

“…Here, especially environmental bacteria that are able to proliferate in the environment and are associated with wastewater, like Acinetobacter species, are interesting. For example, in soil irrigated with wastewater, Gammaproteobacteria, among them Acinetobacter strains, are enriched (Broszat et al 2014) as well as in treated sewage sludge (Wolters et al 2022) and, on the other hand, strains affiliated to this genus were reported from vegetables, meat and livestock (Al Atrouni et al 2016). In hospitals, several Acinetobacter species (A. baumannii, A. pittii, A. lwoffii, etc.)…”