Water & Wastewater Asia March/April 2021

WATER & WASTEWATER ASIA | MARCH/APRIL 2021
largest municipal councils and diverse
food, beverage and primary producers,
ranging from small plants to major
meat, dairy and crop multinationals.
CST’s Services Division was founded
to complement its design-and-build
capabilities to ensure that WWTP plant
operators – and the full spectrum of
water treatment plant operators – get
best value out of their plant for the
longest economic time while avoiding
process and production glitches and
systemic failures.
Mr Bambridge explained that such
services thoroughly earn their place,
because fewer organisations these
days can afford to have specialist
engineering staff on hand 24/7 to
ensure compliance with hygiene,
public safety and Duty of Care
Regulation issues that may arise
only occasionally – but sometimes
expensively. This is because:
1. Screens do have parts that
wear over time. They may have
a design life of many years in
normal service – but regular routine
service and maintenance is needed
to keep them in peak operating
condition. This can be particularly
important in sandy areas (noting
that municipal councils’ WWTPs
serve more the 80% of Australia’s
population living within 50km of the
coast. Many industrial processing
plants fall within the same heavily
populated areas).
2. Screen technology does evolve
over time. What was a fine mesh
screen 10 or 15 years ago, may no
longer be up to the job of protecting
newer processes downstream. It
could be a matter of upgrading
the screen to a finer mesh type
now available with systems that
can remove down to 500 microns.
Similarly, removal of fine grit
down to 105 microns can now be
achieved using updated grit removal
technologies.
3. Asset management. Inlet pretreatment,
including screens, is a
robust but finite asset we all depend
in the waste management business.
The value of this asset should be
maintained by regular servicing, just
like a car. CST has some screens still
operating after more than 25 years,
because the companies involved
have invested in cost-effective
regular maintenance to extend
product life and effectiveness.
4. Risk Management. Because
screens are front-line defence, they
prevent or limit damage occurring
in expensive processes downstream.
These processes can be hard to
get to if they do fail, then cause
many more OH&S issues to rectify.
Compounding the issue is the fact
that many remote and smaller
public and private waste treatment
plants these days do not have the
engineering manpower on hand
to quickly rectify unexpected or
complex and expensive events.
“We know how important the risk
management is, and where the
weak spots are likely to be, because
we engineer dozens of waste
management (and waste-to-energy)
processes purpose-built to minimise
maintenance,” said Mr Bambridge.
“Sometimes the first indication owners
have that their wastewater plant
screens need maintenance is when
they are subjected to sudden heavy
load. This is both the time that they are
most needed, and also the time when
the worst failures can occur if screens
haven’t been properly maintained.
Then, the problem becomes all too
obvious.”
“Raw sewage, or untreated food
waste, can escape through plant
and into neighbouring surroundings,
including sensitive land and
waterways, with potential production
halts, OH&S clean-up risks, pointed
questions and potentially serious
environmental consequences for
public and private entities.”
“Most companies these days
are pretty risk-aware. They know
production stoppages are costly,
and environmental spills can affect
their statutory licence to operate.
“But we still do see, reasonably
often, some obviously poorly
maintained plants causing issues
for the operator. These should be
a thing of the past, when small
investment in yearly maintenance
and check-ups can return good
value and ROI throughout the long
term - particularly as municipals and
industry have to cope with increased
demand on community water
resources as the economy ramps up
post-COVID.”
New rotary drum
technologies, left,
screen out waste
more thoroughly,
while output from
downstream
technologies, such
as KDS solid-liquid
separators, can be
used for wastewater,
sludge, livestock
manure, food waste,
algae, grease trap
waste Oval plates
push down the stuck
solid matter to keep
the filtering zone
clean while dewatered
digested sludge is
easier, cheaper and
more hygienic to
transport to treatment
and recycling plants.
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