Water, Sewage & Effluent Mar Vol 30 No 2 | Page 21

industry
debate
infrastructure

The public sees traditional passive
biological treatment as inferior and
antiquated, and they are therefore not
considered during new plant selection
or upgrades. So, the system that
failed before is replaced with similar
technology. And so the vicious cycle
continues, he says.
“It is not that the technology isn’t
working – we need to look at the real
problems and reasons for such massive
contamination and pollution problems.
The municipalities need to ask – what
can we afford in terms of capital outlay,
ability to operate and maintain from
both financial and resource perspective?
“Do we have the billions to upgrade?
And if it fails? Do we replace again? We
have a situation where the technology
fails, but is then replaced with more
high-tech technology that is even more
onerous to maintain,” La Trobe says.
“What we at WSE propose is that we
go ‘back to the future’, by using a natural
system, and improve the nutrient and
phosphate removal with the use of
phytoremediation of specially selected
plants. This route is seen as primitive,
but it isn’t. Nature has perfected its
processes over millennia, which we know
how to package and design. It does not
break down and one can pretty much
guarantee effluent compliance.
“Decades ago, we had the oxidation
ponding system. It worked and
continues to work. In places where they
are still in operation you don’t need

tech news

Vicious cycle

much in terms of energy and expertise.
We propose that we go back to passive
systems. We start with a conventional
oxidation ponding system and then
add another phase of phytoremediation
treatment.
“Instead of constructing a wetland,
we float a vetiver wetland on the surface
of the polishing pond, where this grass
grows hydroponically. Once the system
is in, it requires very few inputs and it
runs itself.”
These polishing ponds with the
hydroponic pontoons can be placed
downstream of all existing plants as
a polishing phase or back-up system.
La Trobe explains that there is still
a great deal of work for the civil
engineering sector, as the wastewater
treatment plants need to be adapted to
accommodate the additional ponds for
this system.
In addition, pontoons can be used on
open water bodies such as dam to reduce
the nutrient and phosphate build-up
within the water body and will reduce
the eutrophication of these, resulting in
improved water quality and a reduction
in the blue-green algae blooms.

Floating hydroponic wetland
Vetiver grass