Advanced water treatment technologies to minimise nitrogenous disinfection by-products in drinking water

Unintended chemical disinfection byproducts (DBPs) are produced during disinfection of drinking water treatment, a result of reaction of disinfectant, e.g. chlorine, with a diverse group of precursors, including natural organic matter (NOM).

Many DBPs have been implicated in adverse health risks associated with reproduction and cancer. The two most abundant classes of DBPs, the trihalomethanes (THMs) and haloacetic acids (HAAs), have received considerable study; however, one group of DBPs that has not been studied extensively are nitrogenous DBPs (N-DBPs).

While few N-DBPs are currently regulated, many N-DBPs have been shown to be more toxic than the regulated DBPs. There is therefore an urgent need to better understand the health risks and formation mechanisms of N-DBPs for appropriate regulation.

The aim of this research is to further investigate N-DBPs in drinking water, particularly to identify N-DBP precursors, assess their associated health risk, and design advanced treatment methods for their removal. Specifically, the project will investigate the chemistry of a suite of N-DBPs (N-nitrosamines, HNs, HNMs and HAAms) focussing on:

• Testing strategies for N-DBP minimisation in water disinfection, particularly N-DBP precursor removal
• Characterisation of dissolved organic nitrogen (DON) and precursors of N-DBPs in key source waters.

By addressing both characterisation and treatment, the data can then be used to develop risk-based management tools to facilitate the adoption of improved treatment practices and technologies by drinking water utilities, which will be of significant value nationally and internationally.

The treatment technologies and DON characterisation methods developed will be transferable to drinking water schemes globally and project outcomes will be directly translatable into treatment plant design.

PhD Project (based at UNSW) "Advanced characterisation of dissolved organic nitrogen in drinking water sources: implications for mitigating against nitrogenous disinfection by-product formation"

The PhD project focussed on the characterisation of DON and applied numerous techniques previously used for dissolved organic carbon (DOC) characterisation to DON. These procedures included fractionation methods such as size exclusion chromatography, using an LC-OCD (DOC Labor, Germany) and resin fractionation, as well as spectroscopic methods including fluorescence and mass spectroscopy.

The first stage of the project was on establishing characterisation protocols using well understood model compounds before applying these techniques to key source waters in the second stage. Overall, the PhD project aimed to determine the specific characteristics of the source water that increase the potential for N-DBP formation and, in doing so, identify the critical parameters for assessing source water N-DBP formation potential and lend insight into the treatment processes required to remove the precursor material.