Underground aquifers clean water for recycling

A study by a leading Australian research organisation has revealed that the storage of wastewater and storm runoff water in underground aquifers purges it of disease-causing organisms, allowing the water to then be recycled for irrigation.

Scientists from Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) have found that after 40 days of storage in an underground aquifer, all bacteria and viruses are removed from water due to a variety of unfavourable conditions, such as temperature changes, lack of oxygen, lack of nutrients and an army of naturally occurring groundwater micro-organisms that kill or inactivate them. The water is also protected from evaporation and further pollution.

“We’ve been studying the behaviour and fate of various microbes in groundwater taken from different parts of the country,” said CSIRO microbiologist, Dr Simon Toze. “We’ve looked at [intestinal] viruses, the protozoan Cryptosporidium, and disease-causing bacteria like Salmonella and Aeromonas.” As for Cryptosporidium, the researchers are not yet sure of its survival ability, so do not wish to make any claims as to its fate in an underground aquifer. “As for other pollutants, under the right conditions we have observed the removal of disinfection by-products (DBPs) and some other organic pollutants, along with reductions in BOD and inorganic nitrogen,” Toze told edie.

“This makes underground storage one of the most promising ways to cleanse and recycle water,” said Toze. “Australia is naturally a dry continent, and in many areas our groundwater resources are being heavily exploited. This appears to offer a safe, clean way to recharge them.” Work of this sort means that Australia is showing the world a lead in a field that will be increasingly vital to humans and the environment in the future, he added.

There are a number of concerns that need to be assessed before storing water underground, Toze admitted to edie. These include issues such as how much water can be recovered from an aquifer, and whether an aquifer would be seriously impacted by the addition of the water. There are also geochemical or biogeochemical issues such as clogging of the aquifer or dissolution of the aquifer, and the economic feasibility of such a project. “Some of these problems, in some cases, will prevent an artificial recharge scheme from getting underway, sometimes they just need managing and sometimes they are not an issue,” he said.

There is already considerable interest in the project around Australia, says Toze. The research has been funded by the consortium running the Virginia water reuse project and the group running a water reuse scheme at Willunga, both in Adelaide. There are also some pilot artificial recharge projects in Perth, funded by the state government agencies, and there is a trial project in the Northern Territory, again funded by the Territory government. Finally, there is also considerable interest in Victoria, New South Wales and Queensland, although nothing definite has begun there as yet.

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