Performance Efficiency of Conventional Treatment Plants and Constructed Wetlands towards Reduction of Antibiotic Resistance

Abstract

Domestic and industrial wastewater discharges harbor rich bacterial communities, including both pathogenic and commensal organisms that are antibiotic-resistant (AR). AR pathogens pose a potential threat to human and animal health. In wastewater treatment plants (WWTP), bacteria encounter environments suitable for horizontal gene transfer, providing an opportunity for bacterial cells to acquire new antibiotic-resistant genes. With many entry points to environmental components, especially water and soil, WWTPs are considered a critical control point for antibiotic resistance. The primary and secondary units of conventional WWTPs are not designed for the reduction of resistant microbes. Constructed wetlands (CWs) are viable wastewater treatment options with the potential for mitigating AR bacteria, their genes, pathogens, and general pollutants. Encouraging performance for the removal of AR (2–4 logs) has highlighted the applicability of CW on fields. Their low cost of construction, operation and maintenance makes them well suited for applications across the globe, especially in developing and low-income countries. The present review highlights a better understanding of the performance efficiency of conventional treatment plants and CWs for the elimination/reduction of AR from wastewater. They are viable alternatives that can be used for secondary/tertiary treatment or effluent polishing in combination with WWTP or in a decentralized manner.

Wastewater treatment plants, an “escape gate” for ESCAPE pathogens

“…Generally, conventional WWTP treatments can reduce ARGs’ overall richness, concentration, and relative abundance in variable proportions ( Yang et al, 2014 ; Pallares-Vega et al, 2019 ; Li et al, 2022 ). The primary treatment is usually not efficient in removing pathogens and ARB, requiring the use of advanced treatments (e.g., sand and membrane filtration) or disinfection methodologies (e.g., chlorination, UV radiation, and ozonation) after conventional activated sludge treatment ( Hazra and Durso, 2022 ). Many WWTPs only use conventional activated sludge for wastewater treatment, which, however, has been shown to have better removed fecal coliforms, enterococci, and E. coli in comparison to septic tank systems; but, despite this reduction, an increase in the MDR profiles has been observed during wastewater treatment ( Barrios-Hernández et al, 2019 ; Hazra and Durso, 2022 ).…”

“…The primary treatment is usually not efficient in removing pathogens and ARB, requiring the use of advanced treatments (e.g., sand and membrane filtration) or disinfection methodologies (e.g., chlorination, UV radiation, and ozonation) after conventional activated sludge treatment ( Hazra and Durso, 2022 ). Many WWTPs only use conventional activated sludge for wastewater treatment, which, however, has been shown to have better removed fecal coliforms, enterococci, and E. coli in comparison to septic tank systems; but, despite this reduction, an increase in the MDR profiles has been observed during wastewater treatment ( Barrios-Hernández et al, 2019 ; Hazra and Durso, 2022 ). From an analysis of the influent concentrations and the removal of ARGs in a large number of WWTPs in the Netherlands, the researchers concluded that WWTP design parameters such as size, presence of primary clarification, type of phosphorus removal, and operational parameters such as hydraulic retention time, sludge retention time, anaerobic contact time and effluent total suspended solids did not affect the removal of the studied ARGs and MGEs significantly ( Pallares-Vega et al, 2019 ).…”

“…The ozone treatment causes DNA damage but has a reduced effect on guanine-rich DNA ( Alexander et al, 2016 ). UV light is partially absorbed by organic and inorganic matter present in wastewater; thus, the DNA damage depends on the UV dosage; additionally, different sensitivity of ARB to UV radiation was noticed ( Hazra and Durso, 2022 ). A membrane bioreactor has been shown to increase the municipal WWTP efficiency for decreasing the abundance of ARGs and loads of E. coli , enterococci, and P. aeruginosa strains ( Ng et al, 2019 ).…”

“…Still, the ARGs of 12 antibiotic classes, including aminoglycosides, beta-lactams, macrolides-lincosamides-streptogramins, polymyxins, quinolones, rifamycin, tetracyclines, and multidrug resistance, persisted during treatment. Constructed wetlands (CWs) seem to be a sustainable “green” wastewater treatment option that can be used as an alternative to WWTP or as a component of conventional WWTP, having the ability to remove antibiotics, ARB, and ARGs ( Dires et al, 2018 ; de Oliveira et al, 2019 ; Riaz et al, 2020 ; Hazra and Durso, 2022 ). CWs can be used alone or even after primary treatment, contributing to 2–4 log pathogens reduction ( Sleytr et al, 2007 ; Karimi et al, 2014 ) and increasing the performance of WWTP when coupled as secondary/tertiary units to primary treatment ( Chen et al, 2014 ).…”

“…A recent comprehensive review on the performance of primary, secondary and tertiary treatments of wastewater in removing antibiotics, bacterial pathogens, ARB and ARGs concludes that combinations of different methods are more efficient in the elimination of a large number of ARB ( Hazra and Durso, 2022 ).…”