Water, Sewage & Effluent Mar Vol 30 No 2 | Page 25

debate

industry

“Wetlands do for free what engineered
systems do at great cost,” he continues.
Turton says that he has conducted initial
research on the species of wetland plants
that are capable of assimilating different
metals and toxins.
“A floating system is a ‘quick and
dirty’ response that can lead to more
sophisticated system, such as a vertical
flow constructed wetland. Vertical flow
constructed wetlands are a relatively
new and rapidly evolving technology in
the field of ecological and environmental
engineering,” he says.

Advantages

tech news

infrastructure

The vetiver grass system for wastewater
treatment is an innovative technology. Its
effectiveness has been proven across the
globe. It is green, low-carbon, sustainable,
low-tech and low-cost and is ideal for
cash-strapped municipalities. Beyond the
design, installation comprises construction
of simple floats or pontoons, and only
low-level skills are needed to operate and
maintain them. This presents a welcome
opportunity to cuts costs and support local
workers. Another major attribute is that
vetiver grass treatment systems are easily
scaled up or down as needed.

Shortcomings
Naturally, the system also has its
shortcomings. Most of these disadvantages
arise when it is compared to large-scale
wastewater treatment applications. Under
high flows, the vetiver system requires
substantially more space, and this poses
a problem in large metropoles. Passive
systems require longer retention periods
to treat wastewater effectively and special
care has to be taken to prevent shortcircuiting. Each situation has to be assessed
to determine the best approach and
design to ensure a long-term sustainable
solution.
Possibly the biggest shortcoming of
vetiver is that it is simple. Engineers, in
particular, are accustomed to a particular
image of a mechanised wastewater
treatment system, with moving parts. The
perception is that if it doesn’t look like
mechanical treatment plant, it can’t be
doing the job properly.
Passive systems are static and the work
they do is not clearly visible. The system’s
greatest attribute – simplicity – is also its
greatest drawback. Its proponents have
a tough job to convince both the public
and the government that this a viable
wastewater treatment system.

Water Sewage & Effluent March/April 2016

networking

final warning. The processes to treat the
eutrophic water to potable levels become
significantly more complex and expensive,
and if not implemented, could lead to the
contamination of the entire potable water
network through the country.
“The problem, of course, can be fixed.
Anything is possible, with the money and
the will. We believe effective passive, low
maintenance biological treatment systems
and process can play an important role
in proving a sustainable solution to this
widespread issue.
“We have to go back to basics. We need to
look at solutions we can afford. They’ve been
there all along.” he says. Although we do not
have a full scale treatment system operation
in South Africa, a number of municipalities
and metros in South Africa are considering
the system. Australia has implemented a
number of these plants successfully, for up to
500 million litres per day.
“Many wastewater treatment ideas exist
and many are good,” says Wits academic
and previous chairman of the Global
Agenda Council on Water Security, Mike
Muller. “Artificial wetlands to treat sewage
are not new. They are widely practised with
urban wastewater. One of the challenges
municipal managers face is that there are
lots of solutions to fewer problems, so the
difficulty is to choose not just the most
convincing parties, but the solution that
suits that application best.”
Water expert at University of Free State
Centre for Environmental Management,
Prof Anthony Turton agrees that floating
systems have a place and offers an example.
In a small Karoo town, the bucket system
was replaced with water-borne system but
the treatment works were not upgraded
and the system was quickly overwhelmed.
“Here floating islands were suggested as the
solution to the problem.”
Turton explains that a range of plants,
not