Electron Beam Technology for the Removal of the Cyanotoxin, Microcystin-Lr, and the Cyanobacteria, Microcystis Aeruginosa, in Contaminated Waters

Abstract

Increasing global water scarcity is underscoring the need for efficient and reliable treatment technologies within the water treatment process. Ionizing radiation technologies present promising strategies for the remediation of many emerging contaminants. In particular, high energy electron beam (eBeam) technology is a chemical-free advanced oxidation reduction process (AORP) that is generated from commercial electricity and has been proven effective for the breakdown of various organic and inorganic pollutants. Similar variables effecting water availability, such as rising temperatures and nutrient pollution, are also feeding the rising occurrence of harmful cyanobacterial blooms (cyanoHABs). CyanoHABs are responsible for producing an array of hepato- and neuro-toxins that pose threats to human and animal health. Drinking water sources that are affected by a cyanoHAB provide a critical human exposure scenario. The cyanobacterium Microcystis aeruginosa is commonly associated with freshwater cyanoHABs and is responsible for producing a class of hepatotoxins termed microcystins. Of the over 100 variants of microcystin, microcystin-LR (MC-LR) is the most prevalent and most toxic.

This project aimed to investigate the effects of eBeam treatment on the cyanotoxin, MC-LR, and the cyanobacteria, Microcystis aeruginosa. The results demonstrated that low doses of eBeam treatment (<400 Gy) are sufficient to degrade MC-LR at environmentally relevant concentrations. The degradation mechanism of MC-LR appears to be primarily oxidative and degradation products fail to exhibit cytotoxicity in vivo. eBeam doses ˃2 kGy were sufficient to prevent M. aeruginosa cell growth and induced cell lysis. Cell lysis occurred on a time delay of approximately 2 hours following irradiation. However, cell lysis was seen to be coupled to light damage during incubation following eBeam treatment and not the eBeam treatment itself. Finally, eBeam treatment was able to degrade MC-LR in surface water samples by >99% regardless of water quality. The results of these studies suggest eBeam technology is a promising addition into the drinking water treatment scheme for the remediation of cyanoHABs in drinking water.