Laboratory desalination experiments with some algal toxins

Abstract

Over the last several decades, countries throughout the world have experienced an escalating and worrisome trend in the incidence of harmful algal blooms (HABs). A concern is that highly potent algal toxins might be retained in the treated water, posing a threat to human health. Seawater contaminated with saxitoxins, domoic acid, okadaic acid, and brevetoxins was desalinated using small (<100mL capacity) reverse osmosis and distillation equipment. Analyses of desalinated water samples indicated efficient removal of the four toxins to greater than 99%, except brevetoxins for which some carry-over was observed during distillation. Hypochlorite concentrations of 4ppm or higher were sufficient to react with all of the saxitoxins, domoic acid and okadaic acid in the samples that contained initial toxin concentrations up to 1250ngmL−1. Brevetoxins appeared to be unaffected in experiments in which the toxins were exposed to up to 30ppm hypochlorite in seawater at 35°C for 60min. These results and their implications in terms of desalination plant design and operation are discussed.