WITH its free-floating fibrous roots and rapid growth rate, the water hyacinth (Eichhornia crassipes) is one of the most invasive aqueous weeds in Australia and, for many countries around the world, a serious environmental and economic issue.
However, the South American-native’s ability to absorb heavy metals, such as Cd, Cr, Co, Ni, Pb, Hg, and its resilient growth in some of the most polluted waterways on the planet has led some affected countries to utilise the weed as a natural filter.
The use of the hyacinth for controlled phytoremediation—a process that uses plants to remove pollutants from soil or water—is not a new concept.
The Iron Bridge Facility, one of the United State’s largest wastewater treatment plants began using a hyacinth system in the mid 80s, successfully removing large amounts of nitrogen and phosphorous from their 12-hectare pond system.
US Environmental Protection Agency (EPA) figures demonstrated phosphorous removal to be from 35 per cent to 80 per cent with other figures showing a 72 per cent reduction in cadmium.
A research paper released in 2002 by Bangladesh’s Bangabandhu Sheikh Mujib Medical University outlined how, given the right circumstances, the water hyacinth effectively removed arsenic (As) from contaminated water, a serious problem in the country’s water supply.
That same year, the Kenyan-based Water Hyacinth Utilization Project (WHUP) and Kisumu Innovation Centre Kenya (KICK) backed by the Global Environment Facility (GEF) and United Nations Development Program (UNDP) attempted to establish water hyacinth purification ponds along the Nairobi Dam.
The implementation of controlled systems such as these may be beneficial and feasible in WA due to the state’s large focus on the mining industry and eutification that waterways, such as the Swan River, often face.
Water hyacinth use research within Australia may have been hindered further last month when species—already a banned species in WA—was added to the Weeds of National Significance (WoNS) list.
“Any economic use or beneficial attributes of the new Weeds of National Significance are minor compared with the damage they are already causing nationally or have the potential to cause.
“It is a serious weed that can choke rivers, lakes and other waterways. Water hyacinth cannot be sold and must be destroyed,” the spokesperson for DAFWA says.
According to a spokesperson for the Department of Agriculture and Food of Western Australia (DAFWA), no controlled phytoremediation trials have been undertaken in WA by the Department.