Researchers starve toxic algae to nourish rivers

Australian researchers apply a thin layer of absorbent clay to deter the growth of toxic algae.

January 10, 2000
Web posted at: 12:31 p.m. EST (1731 GMT)

By Environmental News Network staff

Water managers may soon have a new tool to clean up polluted waters.

Researchers from CSIRO, Australia's federal science agency, have developed a technology to deprive toxic algae blooms of phosphorus, one of their major food sources.

A research project led by Malcolm Robb of Australia's Water and Rivers Commission and Grant Douglas of CSIRO's Land & Water Division, will attempt to trap phosphorus in water and river sediments by lacing a stretch of the Canning River with a thin layer of an absorbent substance called "phoslock."

Researchers will spread the clay-like substance over the water with a spray gun. The material will gradually sink to the bottom of the river.

Lab tests and previous smaller-scale field tests indicate that the phoslock is capable of removing more than 90 percent of the phosphorus available to algae.

"We know this technique works in the test tube, in a fish tank and a large tank. This is the big test to see if it works in a real river," said Douglas.

The researchers will measure levels of phosphorus in the water and sediments before and after the application of phoslock. They will also monitor its effect on algae, fish and water quality.

A lab experiment shows how phoslock makes river and lake water cleaner and safer (left) by immobilizing nutrients that seep out of the mud and give rise to blooms of toxic algae (right).

"If trials in the Canning River prove a success, the team plans further tests in other famous water bodies in Australia's great cities which are similarly afflicted by toxic blooms," said Douglas.

Douglas notes that the clay treatment is not a "quick fix" for rivers and lakes affected by blue-green algae. The phoslock is a kind of stopgap that must be supported by urgent measures to cut the flow of nutrients entering the water.

"The most important thing is to understand how each river or lake system functions, how and when the nutrients enter it, how they are released from the sediment, and the conditions that trigger algae blooms," Douglas said.

Algae blooms can be deadly to fish and plants. They also can cause poisoning in livestock and humans. They emit bad odors and drive up water-treatment costs.

Algae nutrients, including phosphorus, enter Australia's water bodies from a wide range of sources: sewage effluent, eroded soil, agricultural and industrial runoff. High nutrient levels cause populations of algae to explode through a process known as eutrophication.

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