In the United States just outside the town of Butte in Montana lies a pit of greenish poison two kilometres wide and 500m deep. It was once a thriving copper mine but now abandoned, the pit is full of toxic water containing heavy metal poisons like arsenic, lead, copper and zinc.
No fish live there and no plants line the shores. Birds that land on the surface often die and have to be removed by a skimming boat to prevent additional organic build-up. The water level is rising at a rate of 15cm a month and, left unchecked, it will spill over into the area’s groundwater in less than fifteen years.
Normally acid mine water is treated by adding lime to the water to reduce the acidity and remove much of the metal, but the Berkeley Pit is so saturated with undesirables that this process would produce tons of toxic sludge every day. Other methods are safer, but are prohibitively expensive.
Now the US’s Environmental Protection Agency and local townsfolk are looking towards an ion exchange solution that has been developed and patented by South African company Trailblazer Technologies.
In this process, called the KNeW (Potassium Nitrate ex Waste) process polluted water from mines or other industry is neutralised, filtered to remove coarse particles and precipitated heavy metals, then pumped through an ion exchange battery to remove all the dissolved ions leaving behind water of any designed quality.
This is one of the few processes that can beneficially remove the worst and most difficult to deal with pollutant, namely sodium, says John Bewsey, the chemical scientist who developed the process. Over 60% of South Africa’s water is used in agriculture, he says. “As the water evaporates on the soil it leaves behind the salt which is causing more devastation to our soils than all other dissolved solids together and must be removed from the environment.”
The KNeW process also removes all other dissolved ions from the water, in the process converting toxic effluent into profitable end products like potassium nitrate and ammonium sulphate, both valuable agricultural chemicals. The fact that chemicals produced in the process can help to defray the costs and even earn a modest profit is part of the technology’s attraction.
In November the KNeW process beat five other shortlisted technology processes to take the prize for the best Water Management and Supply solution at the prestigious annual Institute of Chemical Engineers awards, held in the UK. The institute is the hub for 38 000 chemical, biochemical and process engineering professionals worldwide.
The additional attention since winning the award has been electrifying, says Bewsey. Companies that wanted him to build pilot plants on their sites are now prepared to go ahead without a pilot, instead relying on the results from his own pilot plant which is being built in Krugersdorp west of Johannesburg.
One of these is the California State Water authority. California’s Imperial Valley supplies vast quantities of fruit and vegetables across the US and is irrigated from the Colorado River. However this lifeblood threatens the very existence of the valley itself as the river water is highly saline and is slowly destroying the farmland itself. Saline soils prevent absorption of water and other nutrients.
Similarly in water-scarce New Mexico the state government is in talks with Trailblazer Technologies. There the state government is in urgent need of an affordable process to clean up the huge saline groundwater aquifers that can be used to water the thirsty state.
Locally, farmers in the Eastern Cape are also waiting for the results of the pilot plant. The sustainability of the Eastern Cape’s R1bn/year citrus industry is under threat. The Sunday’s River is used to irrigate 17000 hectares of citrus fields, but high levels of salinity in the water have over time led to excessive sodium levels in the soil, causing yields and fruit quality to decline.
The only ‘local’ mining company to show any interest is heavy-minerals mine, Namakwa Sands, majority owned by US company Tronox. The company has been searching for an improved treatment process for its effluent and the KNeW process is the only one selected for testing. Tronox has ordered the installation of a pilot plant at Koekenaap in the North Western Cape to prove the process for them.
Interest from other local mining companies has been slow. In part this is because the technology is new and big established interests are more interested in protecting their own turf. Bewsey believes there is more interest coming from the US because strict environmental rules and penalties make finding solutions there more urgent.