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26
Mechanical Technology — March 2016
⎪
Automation, mechatronics and electro-mechanical systems
⎪
“
G
lobally we have been
automating water treat-
ment plants for many
years, and for the past
few years we have been growing our
water offering in the southern and South
African market,” begins Perumal. “A key
focus for us is providing complete turnkey
solutions for municipalities, water utilities
and industrial treatment plants,” he adds.
“South Africa has many manual sys-
tems where operators need to open and
closer valves using wheels and levers.
Festo provides fully automated systems,
which offer much better control of water
or wastewater treatment processes and
deliver better and more consistent water
quality. Equally important, though, is
maintenance and these systems have
built-in diagnostics and are designed for
easy plug-and-play maintenance,” he
tells
MechTech
.
“In partnership with water infrastruc-
ture contractors, we provide turnkey
installation packages for water service
providers with all media valves, pneu-
matic actuators, controls and up to the
SCADA and software for the main control
room – and we are able to optimise an
automation solution regardless of the
plant’s size or location,” Perumal assures.
Describing the needs of a typical
municipal treatment plant for potable
water, he says that water is generally
pumped into the plant from a river into a
raw water reservoir. From there it is first
chemically treated (pre-chlorination) to
minimise algae growth, before being aer-
ated for the removal of dissolved solids.
The water is then treated with clarify-
ing agents or flocculants, which cause
tiny dispersed particles called colloids to
coagulate onto larger ones. “The treated
water is then slowly mixed before being
passed into a clarifier tank where the
heavier particles sink, forming a sludge
at the bottom of the tank, while the clear
water is tapped off over a weir at the top.
The clear water then passes into filter
beds, typically gravity-fed sand beds that
remove the remaining fine solid particles.
“Between cycles, though, these beds
are cleaned via a backwash process,”
Perumal points out. The filtered water
is again dosed to remove any remain-
ing bacteria and transferred to storage
reservoirs as potable water.
“At every stage of this process, valves
are used to control the process flow.
Valve actuators open and close these
valves. This used to be done manually
but we are now able to automate every
Festo is combining measurement, control and regulation technology with
pneumatic actuators and valve terminal blocks, along with its Aquatronics
training capability, to supply customised automation solutions for water and
wastewater treatment.
MechTech
talks to Durban-based industry segment
specialist for water & wastewater at Festo, Strini Perumal (right).
Left:
The dynamic automated skid from Festo demonstrates the company’s
water industry automation expertise and product range.
Above:
Nader Imani, head of business field education (left), demonstrates
one of Festo’s Aquatronics learning systems, which are available for water and
wastewater management training from basic to advanced levels.
Automated and connected water
part of the process, from level control to
dosing management and back purging,”
Perumal explains.
There are two technologies available
for automating valve actuation: electri-
cal or pneumatic actuation. “Based on
extensive research by Festo, we have
found pneumatic actuation to be far more
economical than electrical. Pneumatic
systems need a compressor, air driers and
filtration units, which have to be piped
through to the valves and actuators,
while electrical systems only need power.
But electrical systems are more expensive
and they need specialised technicians
to manage them. They also need more
complicated programming, since they are
continuously variable devices,” he says,
adding that, “pneumatic valve actuators
are much easier to manage. All they need
are two air lines into each valve.”
Perumal argues that cost comparisons
need to be evaluated over time. “While it
is often assumed that pneumatic actua-