Micropollutants, mixtures and transformation products in recycled water: How much do we really know?

Recycled water usually contains extremely low levels of many different chemicals. The Australian Guidelines for Water Recycling (AGWR) require that some of these cannot exceed levels that would pose a risk to health, safety or the environment but there are concerns that one or more of these, or other, unmonitored micropollutants, might present a risk, or that chemicals that individually are harmless might add together and have undesirable effects. This research measured 300 organic micropollutants (listed by the AGWR) in a range of recycled waters and conducted a series of laboratory experiments. It was concluded that the toxic effects of individual chemicals often do add together but that this can be predicted accurately in most cases. Some disinfecting processes used to recycle water produce new micropollutants and it will never be possible to completely analyse the thousands of chemicals in any one water sample. These results led to the recommendation that classical chemical analytical measurement techniques should be complimented by a suite of bioassays which can quantify the total toxicity of all the mixed chemicals within recycled water.