Nature-based bioreactors: Tackling antibiotic resistance in urban wastewater treatment

Abstract

The overuse and misuse of antibiotics have accelerated the selection of antibiotic-resistant bacteria, significantly impacting human, animal, and environmental health. As aquatic environments are vulnerable to antibiotic resistance, suitable management practices should be adopted to tackle this phenomenon. Here we show an effective, nature-based solution for reducing antibiotic resistance from actual wastewater. We utilize a bioreactor that relies on benthic (biofilms) and planktonic microbial communities to treat secondary effluent from a small urban wastewater treatment plant (<10,000 population equivalent). This treated effluent is eventually released into the local aquatic ecosystem. We observe high removal efficiency for genes that provide resistance to commonly used antibiotic families, as well as for mobile genetic elements that could potentially aid in their spread. Importantly, we notice a buildup of sulfonamide (sul1 and sul2) and tetracycline (tet(C), tet(G), and tetR) resistance genes specifically in biofilms. This advancement marks the initial step in considering this bioreactor as a nature-based, cost-effective tertiary treatment option for small UWWTPs facing antibiotic resistance challenges.

Keywords: ARGs; Biofilms; MGEs; NBS; UWWTPs.

Graphical abstract

Fig. 1

Real image and scheme of the bioreactor. Dark blue: input effluent; red: output effluent; green: benthic compartment; Light blue: output/planktonic compartment; yellow: recirculating compartment; orange: water pumps.

Fig. 2

NMDS of the most abundant and frequently occurring ARGs reads normalised by 16S rRNA reads in different compartments and sampling times.

Fig. 3

The most abundant and frequently occurring logarithmic mean relative abundances of antibiotic families with minority groups and total relative abundances between different compartments. Letters represented the significance between compartments in each group.

Fig. 4

Pheatmap of the most abundant and frequently occurring antibiotic resistance genes (ARGs) from logarithmic relative abundance ARG reads normalised to the 16S rRNA gene reads at different compartments (input, benthos and output) and sampling times (T0, T14, and T28). Antibiotic families are represented with different colours on the right axis of the pheatmap.

Fig. 5

The logarithmic removal rate of the most abundant and frequently occurring ARG reads normalised to the 16S rRNA reads in the bioreactor.

Fig. 6

NMDS of the most abundant and frequently occurring MGEs read normalised to the 16S rRNA reads in different compartments and sampling times.

Fig. 7

Pheatmap of the most abundant and frequently occurring mobile genetic elements (MGEs) from logarithmic relative abundance MGEs reads normalised to the 16S rRNA gene reads at different compartments (input, benthos and output) and sampling times (T0, T14, and T28). MGE groups are represented with different colours on the right axis of the pheatmap.

Fig. 8

The logarithmic removal rate of the most abundant and frequently occurring MGEs reads normalised to the 16S rRNA reads in the bioreactor.

Fig. 9

Relative abundance of the most abundant and frequently occurring bacterial families normalised to the 16S rRNA gene reads in the input and output samples and sampling times (T0, T14, and T28) (a) and non-metric multi-dimensional scaling (NMDS) (b).