Technologies Employed in the Treatment of Water Contaminated with Glyphosate: A Review

Abstract

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide with several commercial formulations that are used generally in agriculture for the control of various weeds. It is the most used pesticide in the world and comprises multiple constituents (coadjutants, salts, and others) that help to effectively reach the action’s mechanism in plants. Due to its extensive and inadequate use, this herbicide has been frequently detected in water, principally in surface and groundwater nearest to agricultural areas. Its presence in the aquatic environment poses chronic and remote hazards to human health and the environment. Therefore, it becomes necessary to develop treatment processes to remediate aquatic environments polluted with glyphosate, its metabolites, and/or coadjutants. This review is focused on conventional and non-conventional water treatment processes developed for water polluted with glyphosate herbicide; it describes the fundamental mechanism of water treatment processes and their applications are summarized. It addressed biological processes (bacterial and fungi degradation), physicochemical processes (adsorption, membrane filtration), advanced oxidation processes—AOPs (photocatalysis, electrochemical oxidation, photo-electrocatalysis, among others) and combined water treatment processes. Finally, the main operating parameters and the effectiveness of treatment processes are analyzed, ending with an analysis of the challenges in this field of research.

Glyphosate Pollution Treatment and Microbial Degradation Alternatives, a Review

“…Physicochemical processes such as adsorption, membrane filtration, and coagulation have proven to be efficient and economical for removing glyphosate [107,108]. Adsorption is a widely used process for treating and purifying water contaminated with glyphosate due to its simplicity, non-toxicity, low-cost design, and high efficiency.…”

“…The adequate selection of adsorbent material is crucial, among the materials that have been used as adsorbents to remove glyphosate from wastewater are clay substances [109], activated carbon [110,111], zeolite [112]; biochar [113,114], graphene oxide and iron-based adsorbing materials [115], resins [116,117]. The glyphosate adsorption process occurs through physical and chemical interactions between the functional groups of the glyphosate molecule (-COOH, -NH 2 , and -PO(OH) 2 ) and the surface of the adsorbent [107]. In general, it has been found that under acidic conditions, the adsorption of glyphosate by different adsorbents is more favorable, so it has been proposed that pH is one of the most determining factors affecting the glyphosate adsorption process [108,113].…”

“…Likewise, the concentration of the pollutant, the temperature, the adsorbent dose, and the ionic strength are also key factors for the overall efficiency of this process [115]. Although adsorption is an efficient method for the treatment of glyphosate in low concentrations, some drawbacks limit its application in practice: (1) successful glyphosate adsorption requires acidic conditions, it is not recommended to drastically change the pH of the wastewater that later could be released into the environment, so that the treated water needs a neutralization step prior to the its environment release; (2) there is no selectivity of adsorbents for glyphosate, which is a disadvantage considering that wastewater contains many other pollutants; (3) most of the studies have been at the laboratory level using ex-professo prepared glyphosate aqueous solutions; and (4) the removal of the residue after adsorption continues to be a problem that also needs to be considered [107,108]. Using this technology as the principal treatment is not recommended (although the affinity of glyphosate with some of the adsorbents is quite good), so it has been suggested to use it as a possible secondary treatment when the concentration of other pollutants is low.…”

“…In addition, the contaminant could be recovered after the membranes are saturated. However, a disadvantage of membrane filtration could be its specificity to reject specific pollutants since, in real conditions, the characteristics and composition of the water could change, compromising the efficiency of the filtration process [107]. Additionally, in several studies, glyphosate removal has not been done in real polluted water.…”

Glyphosate-Eating Fungi: Study on Fungal Saprotrophic Strains’ Ability to Tolerate and Utilise Glyphosate as a Nutritional Source and on the Ability of Purpureocillium lilacinum to Degrade It

“…Glyphosate as a post-emergent, non-selective systemic herbicide eliminating several weed species at the early growth stage is mainly used in agricultural land. Nevertheless, despite agricultural use accounting for 90% of the total usage, glyphosate is also utilised in non-agricultural land such as ruderal, industrial, or urban areas [10,[13][14][15][16]. Its action is based on the inhibition of the 5-enolpyruvyl-shikimate-3-phosphate synthase, an essential enzyme responsible for the synthesis of amino acids in the shikimate pathway in plants and in some microorganisms.…”