How to Make Clean Water Faster and Cheaper

A few seemingly non-descript ponds in the bush 250 kilometres north-east of Adelaide in South Australia are the catalyst for some innovative thinking on wastewater management.

Water authorities from the neighbouring state of Victoria are already using the system to generate on-site energy from Melbourne’s wastewater, and the Flinders University researchers who developed it are following up interest in China.

“We’re talking with people in Hunan province about designing a wastewater treatment plant for a small community that could be replicated in many parts of China and elsewhere,” said Professor Howard Fallowfield, who heads the Health and Environment Group in University’s School of the Environment.

The water industry these days talks about the water-energy nexus and that is a real focus.

What he calls “our pond work” is just one of two related Flinders projects creating interest.

He is also talking with officials in China and Vietnam about a biological filtration system that uses naturally occurring bacteria to chlorinate water quickly and safely.

Both projects have been many years in the making but have found their time as the world seeks new ways to provide clean water without spending lots of money and using large amounts of energy.

“The water industry these days talks about the water-energy nexus and that is a real focus,” Prof Fallowfield said.

Pond or lagoon systems have been around since the 1960s and are pretty simple in principle. Wastewater flows through a series of plastic-lined cells and emerges cleaner and safer two months later.

A new approach and careful tweaking have allowed the Flinders team to create a high-rate system that needs half the surface area, costs half as much to build, and provides the same degree of treatment in five days rather than 65. That means greater efficiency and less water lost to evaporation.

Importantly, the system is very robust. The original demonstration model sits in the bush at rural Kingston on Murray and essentially runs itself.

The key to its viability is the use of naturally occurring algae rather than fossil fuels to aerate the wastewater.

“There has been a tendency to just throw energy at systems to meet water treatment requirements but thinking has to change if we want to curb energy use,” Prof Fallowfield said.

“With this system, where you’re reusing the nutrients in the wastewater, you grow a lot of algae, so you’ve got a really productive system. We can produce 70 tonnes dry weight of algae per hectare a year. That’s three or four times what an agricultural crop will produce.”

If you’ve got enough wastewater, and thus enough algae, you’ve potentially got enough to convert into methane and then electrical energy.

That’s currently happening at Melbourne Water’s Werribee facility, where Flinders has built and commissioned two pond systems.

Power company AGL already is generating electricity from methane produced on-site from biosolids.

Meanwhile Flinders PhD candidate Mai Lei is working with China’s Hunan University to further refine the Flinders-made filtration system, which improves the efficiency of chlorine when trying to strip harmful chemicals from wastewater for reuse.

“A lot of drinking water comes from rivers and lakes but, particularly in developing countries, these waters are contaminated with high levels of ammonia from industry and agriculture run-off,” Prof Fallowfield said.

“Ammonia reacts with chlorine, reducing its disinfection capacity. For every milligram of ammonia it takes 10 milligrams of chlorine before you even start the disinfection process, so there is a huge additional expense.

“We created a biological filtration system that uses naturally-occurring bacteria to convert the ammonia into nitrate which doesn’t react with chlorine, and over the years we have adapted it work at even very low ammonium concentration.”

While similar systems are already in use around the world, the researchers believe they are the first to extend the application to drinking water treatment.

Now they are going a step further by testing whether the system can degrade other chemicals that leach into waterways, including pharmaceutical compounds and personal care products such as shampoo.