Understanding the fundamentals of 2-butene-1,4-dial formation in water disinfection: occurrence, transformation, and control

Disinfection is crucial in water treatment. The use of chlorination, the most common disinfection process, has significantly decreased waterborne diseases. However, recent research reveals that chlorination can produce toxic disinfection byproducts (DBPs) from reactions between chlorine and impurities in source water.

Researchers have identified only a small fraction of the DBPs being produced. Small molecules are particularly hard to identify. Given the huge number of these unknown byproducts, priority should be given to compounds that are inherently toxic or might be become toxic during water treatment. Therefore, a novel approach, combining toxicology and high-resolution mass spectrometry, is being used to identify reactive and potentially toxic compounds formed in water treatment. 2-butene-1,4-dial (BDA) is among one such byproduct recently identified through applying this approach.

BDA is a toxic metabolite of furan; furans are halogenated aromatic hydrocarbons produced by fossil fuel combustion, municipal waste incineration, and various industrial processes. This problematic compound is now found to be formed when phenol-containing water is chlorinated. Most micropollutants contain phenols, e.g. bisphenols; thus, most drinking water sources provide precursors for the production of BDA during chlorination. In addition, the structural diversity of micropollutants means that not only BDA, but also substituted BDAs, could be formed. Two such substituted BDAs, chlorinated BDA and methylated BDA, have recently been discovered. To evaluate the impact of these novel byproducts on chlorinated drinking water safety, we need to know: (a) the relevance of phenolic groups present in emerging contaminants as precursors of BDA; (b) the formation mechanism of BDA and substituted BDAs and (c) their occurrence data in our drinking water.

To answer these questions, the present work will trace the formation of BDA and substituted BDAs using bisphenol S as a model compound under chlorination. Different parameters used in chlorination will be evaluated for their impact on BDA formation. Other substituted BDAs will be comprehensively characterized. With this information we will be able to not only extrapolate to other micropollutants with similar chemical structure, but also develop suitable analytical methods to quantify BDA/substituted BDAs in drinking water. A comprehensive occurrence study of finished drinking water from water treatment works and complementary tap water in different regions of Hong Kong will also be conducted. Experimental factors that could control these byproducts’ formation and minimize the risk to humans from drinking water exposure will then be studied.

The chemical data produced in this study will provide details of the fundamental mechanisms of BDA and substituted BDAs formation through micropollutants as precursors. The success of this work will on one hand, provoke usage of this novel approach to prioritize and identify toxic byproducts in drinking water, and on the other hand, provide the fundamental understanding and control of BDA and substituted BDAs formation in drinking water and their relevant occurrence data. This will protect our most vital resource, water, particularly with regard to the ever- increasing of micropollutants.