Stimulant drugs such as methamphetamine and MDMA are well-known to enter wastewater treatment plants via excretion into sewage, and to be incompletely removed by traditional wastewater treatment. However, much less is known about the fate of these compounds during water reuse processes, such as ozonation, reverse-osmosis treatment, and advanced oxidation. In this work, we find that application of ozone, commonly employed before either membrane filtration (to control biofouling) or biological activated carbon (to break down larger molecules into digestible fragments) reacts in a predictable fashion with the N-methylamine functional group common to many stimulants (e.g., methamphetamine, MDMA, ephedrine, epinephrine). This reaction leads to high yield (~30 – 80%) formation of nitromethane, a hydrophilic, low molecular weight toxic compound. This oxidation reaction proceeds through a series of oxygen transfer reactions leading from the secondary amine to hydroxylamine, then nitrone, then nitro-compound. Nitromethane is the industrial precursor to the potent genotoxin chloropicrin (trichloronitromethane), and in this work we show that the nitromethane formed during wastewater ozonation can be transformed to chloropicrin at nearly 100% yield by drinking water chlorination, and demonstrate via standard addition assays that nearly 100% of the chloropicrin formation in ozonated wastewater during subsequent chlorination (as would likely happen in a direct potable reuse scenario) can be attributed to nitromethane. High-yield transformation of these drugs to nitromethane in water reuse processes, followed by nearly-quantitative transformation of nitromethane to chloropicrin during subsequent drinking water treatment, has potentially serious public health implications. Nitromethane is expected to be poorly removed by both reverse osmosis and advanced oxidation processes in advanced treatment, so it will likely persist through reuse treatment trains. Ongoing work seeks to quantify the importance of individual drugs to the pool of nitromethane precursors in wastewater.

Transformation of N-methylamine stimulant drugs to (halo)nitromethanes during wastewater reuse

2019 Fall National Meeting

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