Rights: The University of Waikato Published 18 June 2008 Download

ESR scientist Dr Brent Gilpin describes how the presence of chemicals from washing detergents indicate that the water has come from the sewage system and therefore may contain faecal matter. Brent is also able to detect the presence of sterols – these are chemicals that are broken down in our digestive system – to indicate that the water may contain poo.


The initial focus of our work has been finding tools that we can use to identify human faecal contamination, often in the background of animal, and we have taken chemical approaches and microbial approaches. So I guess to explain some of the chemical approaches first – in your washing powders, there are fluorescent whitening agents, or FWAs, which are used to whiten and brighten your clothing. These get lost – every time you wash your clothing, they get lost, and they are also added to washing powder, so that the water that comes our of your washing machine contains considerable amounts of these FWAs, and these are a human, man-made compound that aren't found in nature. The water out of your washing material usually gets mixed with the water from your toilet and is then disposed of collectively. So the faecal material that comes out of a toilet contains these FWAs when it’s mixed and it leaves your household. So we are using tests that looks specifically for these fluorescent whitening agents in water, and when they are detected, it’s an indication that you've got human faecal pollution present. A second tool that we have been using is looking for faecal sterols, which are breakdown products of cholesterol. And the sterols that are present in the faeces of an animal or a human are dependent on three basic things. So the diet… so the sterols that you actually consume such as cholesterol, which is found in meat, and various plant sterols, which are found in plants and vegetables and other things you might eat. These then go into your digestive system where the bacteria in your gut will convert these sterols into a range of compounds. So the bacteria, which are different in the guts of all these animals, will convert these sterols into a range of different product. So, for example, humans contain the sterol coprostanol and up to 60 percent of the sterol we excrete, whereas many other animals contain quite different ratios of the different sterols.