The potential implications of reclaimed wastewater reuse for irrigation on the agricultural environment: The knowns and unknowns of the fate of antibiotics and antibiotic resistant bacteria and resistance genes – A review

Abstract

The use of reclaimed wastewater (RWW) for the irrigation of crops may result in the continuous exposure of the agricultural environment to antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). In recent years, certain evidence indicate that antibiotics and resistance genes may become disseminated in agricultural soils as a result of the amendment with manure and biosolids and irrigation with RWW. Antibiotic residues and other contaminants may undergo sorption/desorption and transformation processes (both biotic and abiotic), and have the potential to affect the soil microbiota. Antibiotics found in the soil pore water (bioavailable fraction) as a result of RWW irrigation may be taken up by crop plants, bioaccumulate within plant tissues and subsequently enter the food webs; potentially resulting in detrimental public health implications. It can be also hypothesized that ARGs can spread among soil and plant-associated bacteria, a fact that may have serious human health implications. The majority of studies dealing with these environmental and social challenges related with the use of RWW for irrigation were conducted under laboratory or using, somehow, controlled conditions. This critical review discusses the state of the art on the fate of antibiotics, ARB and ARGs in agricultural environment where RWW is applied for irrigation. The implications associated with the uptake of antibiotics by plants (uptake mechanisms) and the potential risks to public health are highlighted. Additionally, knowledge gaps as well as challenges and opportunities are addressed, with the aim of boosting future research towards an enhanced understanding of the fate and implications of these contaminants of emerging concern in the agricultural environment. These are key issues in a world where the increasing water scarcity and the continuous appeal of circular economy demand answers for a long-term safe use of RWW for irrigation.

Complexities in understanding antimicrobial resistance across domesticated animal, human, and environmental systems

“…Antibiotics in irrigation water can be taken up into crop tissues (mostly roots), but levels of uptake are typically low unless antibiotic concentrations are very high . However, whether uptake occurs depends on the specific crop–antibiotic combination.…”

“…However, whether uptake occurs depends on the specific crop–antibiotic combination. No general rules have yet been established for which antibiotic–crop combinations lead to greater uptake, but, overall, uptake tends to be limited, quite selective, and plant and antibiotic specific . While there is a substantial amount of literature on the plant uptake of antibiotics, there is less information on the uptake of ARGs and ARB into crop tissues, especially where exposure concentrations are within normal ranges and the experiments have been well designed with controls .…”

Carbamazepine as a Possible Anthropogenic Marker in Water: Occurrences, Toxicological Effects, Regulations and Removal by Wastewater Treatment Technologies

“…PhACs can contaminate groundwater through different pathways such as percolation of landfill leachate, artificial recharge, percolation of storm water runoff and leakages from sewers and septic tanks [5]. Depending on the organic fraction of the soil, high attenuation of some PhACs such as hydrophobic compounds (log D > 3) can occur in soil strata en route to groundwater [98,99]. Nevertheless, CBZ concentration in groundwater has been reported to be in the range of 1-100 ng/L in available studies from Canada, Germany, Japan and USA (Table 2).…”

Rapid treatment of greywater (household sewage) by terrestrial weed Achyranthes aspera in SHEFROL® reactors

“…But that is done more out of compulsion than choice-due to the shortage of raw water prevailing now in most regions. But wastewater irrigation, unless done with greywater that has been treated to meet the standards for use in irrigation, can seriously contaminate the environment and pose health risks [8][9][10][11]. In a few studies, suits of several species of plants along with sand or soil as filter media have been used to reduce the pollutant load of greywater and enhance its utility for irrigation [12][13][14][15], but no study exists on the use of any specific terrestrial plant for greywater treatment [16,17].…”