February 4, 2004
By Bontle Moeng
ALONGSIDE the flamingo pan stands a dark green funnel-shaped construction and a series tanks lined with rows of reeds. This strange contraption forms part of the Johannesburg Zoo's new wetlands system.
The zoo created the wetlands system to celebrate World Wetlands Day, commemorated on Monday 2 February. World Wetlands Day has been commemorated since 1997 and marks the signing of the Convention on Wetlands that was signed in Ramsar, Iran, on 2 February 1971.
Clean water from the wetlands system can be used by the zoo
A wetland is an area saturated with water that can sustain a variety of animals and plants adapted to saturated conditions, such as swamps, marshes and bogs. Water permanently covers the soil or is very near to the surface of the soil. The zoo's wetland forms part of the zoo's attempts to educate the public and "raise awareness about the value of wetlands.
Currently the zoo pumps water from the Braamfontein Spruit into a sieve-like catchment tank, which starts the purifying process. Water moves through the system into a settlement tank that catches heavy pollutants and then through more refined filters such as gravel and reed beds. The purified water is then released into the neighbouring Zoo Lake. Some 35 000 litres are pumped through the system an hour.
The zoo's wetlands project has two phases: the first phase, which has already been established, is the cleaning of pollutants from the water; the second phase will see some of the water currently flowing into Zoo Lake being redirected back to the zoo.
Wetlands can be used to filter out pollutants in a water system, said Joburg Zoo educationist Martin-John van Rooyen. "As water flows toward the ocean, a lot of rubble and pollutants accumulate in the natural rivers and streams. Pollutants such as hazardous chemicals and plastic form a major part of the harmful substances that need to be filtered out of the water systems."
A wetland system could be used to filter out a lot of the rubbish accumulated in river systems. Reeds, gravel, sand, bacteria and wildlife that feed on plant and other matter in the water can all act as filters.
According to Van Rooyen: "The zoo's wetland system was constructed as a sieve tank to collect large pollutants with a catchment tank for smaller pollutants which sink to the bottom. The pollutants are pumped out into the city's sewer system."
The clean water is then allowed to flow into three reed-bed ponds. "The reeds are planted in rows to maximise the natural biological filtration process. Water is allowed to flow from one bed to another, through gravel layers to further cleanse it," Van Rooyen added.
"The next project will be to redirect the flow of some of the water back into the Zoo. We will save a considerable amount of money with the implementation of this project," he added.
This system means that the zoo itself will have an endless supply of clean water to use around the property and for the animals. "The beauty of this system is that it cleans the water to such an extant that it is fit for human consumption and it attracts birds, insects and other wildlife," Van Rooyen said.
A large number of fish and bacteria have been released to feed off the nutrients in water. Free-flying birds have also settled in the area, adding to the beauty and serenity of the wetland.
Van Rooyen urged the public to make a point of visiting the extensive bird collection, both resident and free flying. "The zoo hosts a large number of water fowl, cranes and storks - species that are sensitive to changes in wetland systems."
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