Cyanobacteria has been reported to be ubiquitously present in many source waters around the world. Overgrowth of cyanobacteria in source water may complicate the operation of drinking water treatment plants (DWTPs) and deteriorate water quality due to increased cell concentrations and production of harmful cyanotoxins, respectively. β-N-Methylamino-L-alanine (BMAA), a neurotoxin produced by more than 20 genera of cyanobacteria, and its isomers, 2,4-diaminobutyric acid (DAB) and N-(2-aminoethy) glycine (AEG) have been recently reported to present in source and finished waters in Taiwan and other places in the world. However, the studies on the treatment and removal in DWTPs of these cyanotoxins have been limited to oxidation of BMAA only. Therefore, there is an urgent need to understand the treatment of the three cyanotoxins in water treatment processes so that better water can be provided for those with cyanobacteria in their source waters. In this study, the reaction kinetics between the three neurotoxins and five oxidants commonly used in DWTPs, including chlorine, ozone, permanganate, hydrogen peroxide, and hydroxyl radical were investigated. Chlorination of BMAA were found to produce four chlorinated intermediates, following a second-order type of reaction. The chlorinated intermediates may further react with free chlorine, also following a second-order reaction, and may auto-decompose slowly following a first-order type of reaction. Under reducing condition, the chlorinated intermediates were reduced back to BMAA. Oxidation of BMAA, DAB and AEG with ozone and OH radical also followed the second order reaction rate law. Permanganate and H2O2 were not able to destruct BMAA and DAB, while permanganate was able to degrade AEG. The rate constants were found to be pH dependent, with similar pH dependency for OH radicals and chlorine, and different for ozone. The reaction rates obtained were in the order of OH radicals &gt; ozone &gt;&gt; chlorine &gt;&gt;permanganate ~ H2O2 ~ direct photolysis. In addition, water matrix was found to slow down the degradation of BMAA and DAB during the oxidation if compared with that in deionized water. The rate constants obtained between the three neurotoxins and the five oxidants may be used as useful references for water utilities to estimate the removal efficiency for BMAA, DAB, and AEG in DWTPs.

Oxidation treatment of new cyano-neurotoxins BMAA and two isomers

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.