Research into chemicals found in recycled water is offering a promising insight into the viability of using aquifers for water storage.
In a project funded by the National Ground Water Research and Educational Foundation (NGWREF), RMIT lecturers Dr Matthew Currell, a hydrogeologist and Dr Oliver Jones, an analytical chemist, have teamed up with Will McCance, an engineering student, to investigate contaminants in the recycled water plant at Werribee.
Using recycled water is an attractive water management strategy in drought prone areas worldwide, but the lack of places to store the water is often an issue.
One solution to this problem is aquifer storage and recovery (ASR). This involves pumping highly treated wastewater into a depleted aquifer to replenish supply and then pumping this water back out when it is needed.
“ASR schemes such as the one at Werribee have considerable potential in urban water management because water companies don’t need to build expensive new surface reservoirs - and since the water is stored underground, there is no loss by evaporation,“ said Dr Currell.
“This sounds good in practice but what if the recycled water still had potentially harmful contaminants in it? What would this mean for the future use of the water?“
The team are based at Werribee Western Treatment Plant where around half of Melbourne's sewage is processed and almost 40 billion litres of recycled water is produced each year.
“Our research is determining what is in the water and what happens to any pollutants once they enter the aquifer,“ says Dr Currell.
“They might be degraded or they might still be there once the water is recovered. If they are still present, then that presents a risk to anybody using that water.“
The research is focused on a selection of chemicals labelled by the US EPA as “contaminants of emerging concern“ (or CECs). These are chemicals in water that had previously either not been detected, or which are now being detected at levels significantly different than expected.
The term CEC refers to a diverse range of compounds including pharmaceuticals and personal care products, pesticides and food additives among others. Environmental regulators are worried about these compounds because the risk to human health and the environment is unknown and there are very few (if any) regulations regarding their presence in the environment.
“This is really exciting work as it is one of the very first times an ASR scheme has been investigated for CECs so the results are cutting edge research,“ said Dr Jones.
After a detailed literature review and discussions with EPA Victoria, the team selected a range of CECs including five pharmaceuticals, three disinfection by-products, two industrial chemicals, two pesticides and one food additive.
Each compound was then tested thoroughly to determine recovery rates and detection limits before they undertook any sampling.
Over a four-month period samples were found to contain low traces of chemicals which included an artificial sweetener, a detergent, a pesticide and pharmaceuticals.
The team saw some differences in concentrations and presence of some of the compounds across the sampling period, which they think reflects either seasonal variability in the amount of these substances in the influent wastewater and/or differing degrees of persistence during treatment.
Much of the work on this project has been undertaken by Mr McCance as part of his final year project. For him it was a great opportunity to receive real work experience and learn new skills.
“I agreed to participate in the project as I wanted to gain more experience in groundwater and hydrogeology,“ said Mr McCance.
“The project appealed to me as it not only covered both these disciplines, but it also involved field and lab work, and it also meant that I would gain valuable industry experience.
The group are now working on publishing their results as a scientific paper in the journal Ground Water published by the National Ground Water Association.