Water & Wastewater Asia November/December 2020

FOCUS 29
WWA: What did you have to do to resolve
this issue?
LAI: Firstly, we dosed chlorine dioxide in
the bypass to remove the existing biofilm
using Grundfos’ Oxiperm Pro. To ensure
the cooling towers has the adequate water
reuse infrastructure to avoid running into
the issue of biofouling again, Grundfos
proposed implementing digital dosing
pumps into the system for the dosing of
antiscalants and pH correction.
To ensure appropriate dosing with an
accurate and efficient system, Grundfos
employed an optimum solution through
the use of SMART Digital DDA and the
DID measuring and control system. The
digital dosing pumps not only regularly
introduces chlorine dioxide into the
system, it ensures that the right amount
of chlorine dioxide is used for each
dose, by measuring the chlorine dioxide
concentration, pH and conductivity in the
recirculation loop. To control the dosage,
a measurement and control system has
been installed. The whole system is
connected to the BMS or SCADA to provide
documentation and insights.
The concentration in the water is also
measured continuously online, where the
dosing is only done if the chlorine dioxide
concentration drops below a certain level.
These measures in turn minimises the use
of chlorine dioxide as much as possible,
while still ensures the water is disinfected
without requiring valuable labour
resources for cleaning.
Meanwhile, the DID measuring and control
system allows the monitoring of
concentration level of impurities in
the water system. This consists of two
conductivity sensors which constantly
measures the water’s conductivity,
ensuring the constant monitoring of any
changing feed water condition or corrosion
risk due to increasing salt concentration
in the cooling tower loop. This puts the
system owner in control of the cycles of
concentration that the cooling tower is
operating at any time, without the need
to wait for laboratory results or manual
measurement.
In summary, Grundfos was able to achieve
three key benefits:
1. Reduced operation expenses: The
SMART Digital DDA has a dosing
accuracy better than +/- 1% of the
set point, which enables increased
system performance and savings of
chemical consumables.
2. Water efficiency: Through the precise
measuring and controlling capabilities
of the DID measuring and control
system, unnecessary production
downtime is avoided while the
intelligent system also enables
reduction of cleaning water to lower the
environmental footprint of facility.
3. Optimised process: Operators will feel
more confident in using and adjusting
the SMART Digital DDA equipment,
as the clear plain texts is available in
25 languages, and the traffic light
system indication the operating status,
are easy to operate.
WWA: We understand some methods
of treating water include using UV
sterilisation - what are some fallbacks
of using this method, and how does the
technology that Grundfos offers compare?
LAI: While UV sterilisation has proven to be
effective in the rapid, effective inactivation
of microorganisms, it might not work
in some cases as demonstrated by the
Singapore cooling towers case, where the
system was still overtaken by a biofouling
issue three years into its operations.
On the other hand, chemical disinfectant
like chlorine dioxide have a residual effect,
which means that they remain active in
the water after disinfection. It continues to
prevent pathogenic microorganisms from
growing in the plumbing after disinfection.
Concerns around exceeding the required
amount of chemicals into the water is
addressed through our technology’s
ability to measure the concentration in
the water continuously online, where the
dosing is only done if the chlorine dioxide
concentration drops below a certain level.
In addition to what I had shared on the
digital dosing pumps and other measuring
applications, Grundfos has also developed
an app to ease the chemical management
in dosing applications. Managing
hazardous chemicals, reporting, logging,
and surveillance will no longer be a worry
for cooling tower owners and operators.
All components function perfectly on their
own but with the chemical management
app, users can add another layer of safety,
while ensuring compliance with legislation.
The onsite chemical preparation combined
with the digital dosing technology, the
measurement and control devices deliver
safe and reliable operations for the
system’s end-user. For chemical suppliers
and the system builders or operating
companies, the solution helps secure the
chemical handling and the operation of the
overall cooling system.
WWA: Is there anything else you would
like to add?
LAI: Digitalisation unlocks efficiency,
profitability, and resilience in the water
sector, and this is best exemplified by new
technologies that are currently emerging
for industrial water reuse. As industries
continue to evolve, business leaders
should not neglect opportunities to also
innovate in all aspects of their operations,
especially water management, which
plays a big role in operational cost and
consumption of resources. With water
being an increasingly scarce resource,
industries need to play their part in
reducing their water consumption to
strengthen global water security.
November / December 2020 • waterwastewaterasia.com