Legislative Council

QUESTION: Trihalomethanes in Adelaide's drinking water

December 6th, 2016

On the 6th of December, Mark asked the Minister for Water and the River Murray questions about water quality and, in particular, the presence of trihalomethanes in Adelaide's drinking water.

The Hon. M.C. PARNELL: The issue of trihalomethanes in drinking water has arisen most recently during debate over the expansion of Adelaide Hills townships and extra residential development in the Mount Lofty Ranges water protection area. Trihalomethanes are compounds that can occur in chlorinated water supplies as a by-product of organic materials present in the water reacting with the chlorine.

One of the submissions to the Adelaide Hills Council's public consultation on increasing development in the Adelaide Hills refers to this problem and suggests that, as the amount of housing increases, the quality of water will decrease and the amount of chlorine required to treat Adelaide's water supply will increase. The submission goes on to say that they believe that Adelaide has one of the highest levels of THM (trihalomethanes) of any city in the developed world.

A quick look at the SA Water Drinking Water Quality Report 2014-15 shows that, of all the different pollutants in our water that we measure, the only one that failed across the metropolitan area was trihalomethanes. I also note that the health level that it failed to meet is actually three times the US level. We already have, it seems, on the government's own data a problem with this pollutant in our drinking water.

My question to the minister is: what steps is he taking to ensure that the quality and safety of drinking water in Adelaide will not be compromised by increased development in the Mount Lofty Ranges water protection area?

The Hon. I.K. HUNTER  (Minister for Sustainability, Environment and Conservation, Minister for Water and the River Murray, Minister for Climate Change): I am not exactly sure what the honourable member is referring to in terms of increased development. Is he suggesting perhaps (and I do this by way of a hypothetical because I know that he can't respond, and undertake to check this out for him) that further housing development in the Adelaide Hills area—for example, Mount Barker, Murray Bridge or other areas—will put increased pressure on the water supply and therefore increase interactions between organic matter that is in the water system currently with chlorine, resulting in chloramines, which is the chlorine smell people have coming out of their taps; or is he saying that in fact increased development means more run-off into the water supply reservoirs?

The Hon. M.C. Parnell interjecting: 
The Hon. I.K. HUNTER: He is nodding and saying that's exactly what he means. Indeed, we have a big problem in the Adelaide Hills in particular, but in South Australia I suppose, in terms of our water storages because they are very close indeed to developed areas and agricultural and farming areas. If you fly over Victoria or New South Wales, for example, and glance out of the plane as you do, you will see that most of those large water storages—which hold water at great depth and in great quantity and provide those cities with water security for a period of years compared to our storages, which provide storage security for a period of months—are in fact often surrounded by vast areas of either commercial forest or natural native vegetation.

That is not the situation with us. We have to work with what we've got—low hills, essentially with country towns or hills-based towns and, cheek by jowl, you will find agricultural production. So, you get all these effects that you get from town run-off, road run-off and agricultural production in terms of, for example, manure and urine run-off, and chemicals of course used for agricultural production. These are all issues that challenge our water supply system, not the least of those being town run-off as well, but these are areas in which SA Water has great expertise in managing.

We have dosing stations at most of our storages that supply water to actually do what we need to do: to decrease the amounts of chemicals that are coming into the system, usually by treating them with other chemicals and floating them out of the system or some other method perhaps using membranes, and additionally to treat it with levels of chlorine which will make it safe, and particularly with agricultural practices, you have to worry about cryptosporidium, which is one of the obvious ones. These are things that SA Water has great expertise in. They have great expertise in this in terms of the metropolitan area and also our storages in the Hills, and I have no reason to suspect that they won't be able to manage this into the future.

The PRESIDENT: The Hon. Mr Parnell, supplementary.

The Hon. M.C. PARNELL: I thank the minister for his answer, but will he take on notice that part of my question that related to his investigating the potential future safety of Adelaide's water because the chemical that I am talking about is in fact a by-product of the chlorination process—the more chlorine you add, the more of these toxic, carcinogenic by-products you get? Could the minister take that on notice?
The Hon. I.K. HUNTER  (Minister for Sustainability, Environment and Conservation, Minister for Water and the River Murray, Minister for Climate Change): I am very happy to indicate that I will take that on notice and try to get some advice from the Department for Health and Ageing as well for the honourable member in relation to that chemical in particular. But, of course, unless you are using some other form of disinfection, which probably has cost impacts as well, we will probably always be in a position where we need to use chlorination for our water system in this state.

On the 14th February 2017 the following response was provided:

Hon Ian Hunter MLC: SA Water continues to work with relevant agencies (DPTI, DEWNR/NRM and EPA) to ensure planning policies and on-ground implementation of adequate water development controls take regard of water quality protection in the drinking water supply catchments.

With appropriate development and catchment management, there is no evidence to suggest that increases in chlorine dosing will be required to treat drinking water, or that Trihalomethan (THM) concentrations will increase.

SA Water publishes a Drinking Water Quality Report each year to provide transparency of performance of wter quality against the health requirements.

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