Download Keeping Water In Cooling Tower Clean Without The Aid Of Chemicals

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Keeping Water In Cooling Tower
Clean Without The Aid
Of Chemicals
Water treatment technology aids in keeping cooling towers maintenance low and save water
By Infra Aktif Sdn Bhd
I
t is another hot and sweltering
day. The phone has not stopped
ringing. People from all parts of
the building are calling to tell you that
the air conditioning system has
broken again. With a heavy sigh, you
head outside to check the chiller. An
idle chiller and a slimy, scaleencrusted cooling tower greet you.
People choose to install watercooled cooling systems for good
reasons. They are twice as energy
efficient, quieter and last longer than
their air-cooled counterparts.
However, if the water is not treated
properly, these systems can quickly
become a maintenance nightmare. For
decades, the industry has chosen
chemicals to treat cooling towers and
other water-cooled equipment. There
were no alternative non-chemical
water treatment systems then.
The most common problems
encountered are scale deposition,
corrosion, fouling and microbio
(bacteria, algae, fungi, etc) growth.
Today, there is an even greater threat,
the emergence of pathogenic bacteria
like Legionella Pneumophilia.
A consistent, effective water
treatment programme is absolutely
essential for cooling towers and other
water-cooled equipment. Lack of
proper treatment will eventually lead
to serious problems, including:
● Excessive equipment downtime
and premature failure
● Occupant
discomfort and
complaints
● Possible health and safety issues
● High water and energy costs
● An
ideal water treatment
programme would:
● Prevent scale formation on
equipment surfaces
● Provide corrosion protection
● Control microbiological growth
● Minimize maintenance costs
●
●
Minimize water consumption
Be environmentally responsible
The search for a non-chemical
way to reduce scale formation has
been the “wish” of those seeking a
“green” solution to this problem.
Chemical water treatment can be
successful at controlling scale.
However, the problems associated
with adding chemicals with various
degrees of toxicity are widely noted.
Chemicals in the concentrated form
are often acute toxins and their
chronic toxicity in the diluted form
is often uncertain. Chemicals must be
added at the right time and rate or
they are not as effective. If
improperly added to a system, they
may cause severe operational
problems.
Non chemical treatment using
electromagnetic and ionization is now
very reliable, less expensive and
requires less energy to operate.
Electromagnetic and copper-silver
ionization can provide the sole
treatment with no additional
chemicals added. This method of
treatment will not allow bacteria to
grow and will not harm cooling
system metals, pump or valve
components. Scaling and corrosion
will be controlled more effectively.
Having to clean the chiller tubes to
remove biofouling is not necessary.
No chemical residual in the blowdown
Figure 1: Chemical deposit on pipe wall
B U L E T I N I N G E N I E U R 60
means environmentally friendly
operation with no environmental
impact or permit requirements.
Microbio is a concern because it
contributes to and amplifies
deposition, corrosion and fouling by
acting as a catalyst for these
problems. Traditionally, nonoxidizing biocides and oxidizing
biocides are used to control microbio.
Most of these biocides have a longterm negative impact on the
environment. As such, there is a
growing pressure to reduce or restrict
these biocides in the blowdown water,
especially if the water is being
discharged to a waterway. In addition
to the discharge burden, these
biocides have to be stored, transported
and handled, which increases
potential health and injury risks to
personnel.
Keeping scaling, corrosion and
microbial growth under control
Scaling: Water usually contains
several dissolved minerals, including
calcium carbonate CaCO3 iron and
silica. As long as these minerals stay
in suspension or dissolve, they do not
pose a problem to equipment.
However, when water evaporates, the
minerals are left behind. Eventually,
the water becomes supersaturated and
can no longer hold the minerals in
suspension. When this happens, the
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minerals fall out of suspension or
precipitate. Since minerals have a
natural electrical charge, they are
attracted to the metal surfaces of
equipment and will form scale. The
mineral content of water is expressed
in either parts per million (PPM) or
total dissolved solids (percentage).
Calcium carbonate or CaCO 3 will
usually precipitate and form scale
sooner than most other minerals.
Microbial Growth: Warm, moist
environments are ideal for the
production of bacteria, mould, slime
and other organisms. If not properly
controlled, these organisms may
cause restricted airflow, clogged
pumps, valves or filters and other
problems. Most experts agree that
one of the best ways to control
biological growth is by keeping the
cooling tower clean and free from
scale and slime. This can be
accomplished through the use of
chemicals,
exposure
to
electromagnetic energy and manual
cleaning. However, if chemical
bactericides are used, they are often
species-specific and must be
periodically switched to maintain
adequate control.
Corrosion Protection: Oxidizing
biocides (bromine, chlorine, ozone,
etc.) are the most effective chemical
biocides for controlling bacteria.
Unfortunately, they are also very
corrosive. Chlorine is often used since
it is very inexpensive. However, it is
not very effective at the higher pH
ranges at which most cooling towers
systems are operated. It is very
corrosive to both the internal tower
components and the surrounding
piping exposed to the vapour.
Water is often referred to as the
“universal solvent”. It has an amazing
ability to break down many different
types of materials, including metals.
The corrosiveness of water is
determined by the number of
hydrogen ions present and measured
using the pH scale.
Care must be taken to maintain
the pH within acceptable ranges. If
the pH is too low, the water will
corrode
unprotected
metal
components of the cooling system. If
the pH is too high, scale may deposit
onto the equipment surfaces. When
Figure 2: Typical electromagnetic treatment Fe ion level
electronic circuitry to induce a high
frequency,
time
varying
electromagnetic field into the
circulating water via an inductor coil
unit. The inductor coil unit (shown
below) is essentially a section of the
PVC pipe wrapped with a solenoid
coil. However, these coils are not
Technology Description:
merely a few turns of wire; they are
How Does It Work?
very complex devices resulting from
Preventing
Scale:
The years of experience. This helps to
electromagnetic system consists of ensure the water molecules are
two primary components: a high- completely exposed to the pulsating
frequency electromagnetic wave electromagnetic field.
Cooling tower water is transmitted
generator and an inductor coil unit.
The controller uses proprietary from the cooling tower basin and
pumped through the inductor
coil for treatment by a
continuous constant flow
submersible pump. The treated
water is then discharged back
into the cooling tower via a
PVC pipe with discharge holes
installed around the periphery
of the water basin. The
preferred location for
installing the inductor coil
unit is between the discharge
side of the condenser water
circulation pump and the
chiller. However, the inductor
coil unit may be installed
between the chiller and the
cooling tower. For some
applications, an additional
unit may also be installed on
the incoming (makeup) water
line.
Electromagnetic system
does not filter out or remove
the minerals in water; they
Figure 3: Electromagnetic Descaler and
simply affect the way minerals
Inductor Coil Unit
precipitate out of solution by
using chemical treatment, phosphates,
silicates or triazoles must usually be
added to the water to offset the acidity
of the biocides. However, this caused
other problems as they served as
nutrient for bacteria to grow.
B U L E T I N I N G E N I E U R 61
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altering the electrical charge of the
particles.
With effective electromagnetic
water treatment, the water hydrogen
bond, polar bonds, ionic substances
in the water will be excited to produce
the various beneficial effects. One of
the effects is the increased solubility
of water. As a result, more calcium
and carbonate ions can be dissolved
in water and prevent the precipitation
of hard scale calcium carbonate. In
simple terms, exposing the water to
varying electromagnetic energy
causes minerals to ‘clump together’
rather than depositing onto the
equipment surfaces. In the event that
calcium carbonates do form, it shall
be in the higher energy calcium
carbonate soft scale “Aragonite”
instead of low energy calcium
carbonate hard scale “Calcite” that
can adheres strongly along the pipe
walls
Aragonite will not stick well on
heat exchanger surface and will be
readily carried off in the discharge
water during blow-down.
A few years ago, several efforts
were made to treat water by using
fixed, permanent magnets. Most of
these attempts were unsuccessful.
Subsequent experience has shown
that the minerals must be exposed to
a
sufficient
amount
of
electromagnetic energy to effectively
treat the water. So far, one of the best
ways to accomplish this task is to
repeatedly expose the water to a timevarying electromagnetic field. The
intensity, frequency and pulsating
action of the electromagnetic field are
the key to effective water treatment.
Removal of Existing Scale: One of
the more outstanding benefits of
using electromagnetic water
treatment is its ability to remove
existing scale. When this system is
installed on a system with a history
of scale problems, customers are
cautioned to check their filters, traps
and sumps for chunks of scale that
often fall off in the weeks immediately
following an installation. This may
occur very rapidly within a week or
gradually depending on the type of
equipment, the composition of the
scale and a variety of other factors.
Under normal conditions, existing
scale develops minute cracks due to
the expansion and contraction of the
material beneath it, especially the
boilers. These cracks weaken the scale
until the minerals in the water
replenish and strengthen it. When the
electromagnetic system is installed,
the minerals are no longer attracted
to the existing scale. They now
precipitate out in the form of powder.
Consequently, the scale becomes
weakened to the point that the force
of the water moving across its surface
is sufficient to dislodge it.
When cracks develop in the scale,
the treated water penetrates the scale.
Because the molecular charge of the
water has been altered, the calcium
in the scale is attracted to the excited
water molecules and becomes part of
the calcium carbonate powder
(Aragonite). This further weakens the
integrity of the scale.
Chemicals and Sludge: If the cooling
tower was previously treated by
chemical, it is quite reasonable to
expect that the cooling water system
has accumulated a lot of chemical
deposits. When descaling starts,
besides gradually removing the hard
scale, very fine chemicals, including
phosphates, will be released from the
deposit and enters the main water
flow stream. These sticky chemicals
can coagulate with other particulate
and settle down at the condenser tube
surface. These sticky coagulation
substances are usually greenish or
dark grayish in color. It is these
chemical coagulated substances from
the previous chemical treatment that
cause the increase in approach
temperature or sometime compressor
overloading.
Corrosion Protection: There are two
levels of corrosion protection. First,
the excited water molecules will trap
the dissolved oxygen ions and reduce
the chances of formation of iron oxide
at the steel surface. Hence, reducing
the corrosion rate. Secondly, when
steel surface and water are
electromagnetically excited they
acquired a higher energy, causing the
formation of “black rust” called
“magnetite” instead of the common
“red rust”, Fe2O3. The magnetite has
the composition of Fe3O4 adhering
to steel surfaces in contact with water.
Unlike Fe2O3, the Fe3O4 layer is
stable and will act as a protective
layer preventing further corrosion.
Figure 4: Effects of boiler descaling
Microbial Growth: Cooling towers are
just like giant air washers. Bugs, pollen,
spores and dust moving by the air inlet
side of a tower will end up dissolved
Figure 5: 14 days after electromagnetic treatment
B U L E T I N I N G E N I E U R 62
The electromagnetic descaler and
magnetite generator are housed in one
enclosure and mounted outside the
cooling tower together with the
copper-silver ionization unit and
ELCB enclosures.
Submersible pump placed in the
sump delivers water through the coil
unit and discharges back to the sump
through the holes drilled along the
PVC pipe.
Figure 6: BacComber ionization is a continuous disinfection process and
will maintain the bacteria count at low levels at all times.
in the water. This organic material in
itself is not harmful to heat exchange
equipment but is an excellent food
source for bacteria and viruses to feed
on. Bacteria multiply quickly forming
slime layers on all wetted surfaces in
the cooling system. Left uncontrolled,
heat exchange efficiencies deteriorate
and equipment comes off line.
Electromagnetic and copper-silver
ionisation used for cooling tower water
treatment are not true bactericides.
Instead, they control microbe
populations by limiting their ability to
reproduce. This is accomplished
through two mechanisms:
The effective control of bacteria
(including Legionella bacteria) and
algae growth in the cooling water
system is performed by the coppersilver ionization system. The fact that
copper and silver ions can be used for
disinfection and algae control has been
widely recognised and proven.
To a large extent, the
electromagnetic generator will
compliment the copper-silver
ionization system in controlling the
bacteria and algae growth. The
performance of the copper-silver
ionization system is depending on the
effective discharge of copper and
silver ions into the cooling water.
When the transformer rectifier
energizes the copper and silver
electrodes, copper and silver ions are
discharged into the water which will
kill the bacteria and algae, hence
controlling their growth. The copper
ions in water will kill bacteria while
the silver ions will alter the bacteria
DNA to prevent the bacteria from
multiplying.
When electromagnetic and
ionisation is first operated on an existing
tower where a moderate chemical
treatment programme has been in place,
the water actually gets dirtier for the first
few weeks. The dirt, slime, rust and
deposits on the inside of the piping start
to come off. This shows that this system
is indeed starting to work.
This debris is held together on the
surface by biological glue. This treatment
destroys the food source for the
biological glue. If the bacteria have no
food source they cannot multiply and if
they cannot multiply they will die off in
the natural cycles.
B U L E T I N I N G E N I E U R 63
How can it provide savings?
These are the important factors
that potential savings can be realised.
● Avoided chemical costs
● Reduced water consumption
● Reduced maintenance (scale
prevention, no chemical feed
pumps to maintain or switch
over)
● Increased cooling tower and
chiller efficiency (prevention and
removal of existing scale)
● Enhanced safety-no need to store,
handle or use hazardous water
treatment chemicals
● More environmentally friendly
than chemical treatment; may
avoid costly environmental fees
and penalties
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How is it installed?
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The users
After more than 20 months of
continuous outstanding system
performance in the Asia region, the
cooling tower owners are switching to
this combined electromagnetic and
copper-silver ionization system, the
BacComber. The private sector takes the
lead in using BacComber, especially ISO
14000 multinational companies. These
include big names such as:
● Matsushita
● Maxtor
● Asahi Techno Vision
● Grand Hyatt Hotel
● Novetel Hotel
and many more.
In this short period of less than
20 months, over 600 BacComber
systems are already installed
spreading over more than 120 sites.
It is becoming an increasing
trend in the region to switch
from chemical water treatment to
the non-chemical BacComber
system and the driving force
behind these changes are due to
the following factors:
1) Environmental friendly - No
chemical required therefore no
pollution problems.
2) Water savings
3) Effective control of scale,
corrosion, bacteria, algae and
bio-film
4) Less chemical corrosion related
maintenance work required and
less damages to systems.
5) Considering the overall savings
and system cost, it is more
economical than chemical or
other systems.
6) Consistent performance, no
cyclic performance problem as
compared to chemical treatment.
7) Reliability
With extensive research and
development, BacComber has proven
to be the most effective non-chemical
water treatment available in the
market. The expansion in the areas
of application for BacComber
includes:
B U L E T I N I N G E N I E U R 64
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Boiler Water
Process Equipment Water
Irrigation
Water Storage Tank
Chilled Water System
Potable Water System
Agricultural/Hydroponics
Closed Circuit Cooling Water System
Fountains
Swimming Pools
Aquarium
Drinking Water
Hot Spas and Tubs
Portable Water Storage and
Distribution System
• Cooling Water System Recycled
Wastewater
• Cooling Towers
Let Infra Aktif Sdn Bhd and you
join forces to make this change and
utilize a more environmental friendly
water treatment process. Our web page
www.infraaktif.com will be able to serve
you with additional information.
With this collaborative effort, we
believe that together we will create a
better environment. BEM