Peristaltic Pumps for Sodium Hypochlorite Injection
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The use of peristaltic pumps as the most effective method to pump sodium
hypochlorite in water treatment plant applications
The quality of life for Americans was greatly enhanced in the early
1900’s due to the introduction of chlorinated drinking water throughout
the United States water systems. From the stockyards of Chicago to the
Boonton Reservoir of Jersey City, the case was established that
filtration alone was not sufficient to guarantee clean water. By the
1920’s, chlorination was well entrenched as the primary means of
disinfecting drinking water. The combination of filtration and
chlorination reduced typhoid fever by 91 percent within five years which
lead to its near eradication by 1936, according to a statistical study
of disease rates.
Chlorine-based disinfectants have been the choice for treating drinking
water since the turn of the 20th century. This is the only type of
disinfectant that provides a residual in the distribution system that is
vital to preventing waterborne diseases. Three forms of chlorine that
are commonly used are: gaseous chlorine, calcium hypochlorite tablets,
and sodium hypochlorite solution. However, safety concerns and costs
have prompted many municipalities to switch from chlorine gas to sodium
hypochlorite. The most common disinfection method is some form of
chlorine or its compounds such as chloramine or chlorine dioxide. Other
non chlorine-based disinfectants are Ozone and UV radiation.
According to the Water Quality and Health Council, 98 percent of systems
that treat water utilize chlorine-based disinfectants. Moreover, the
World Health Organization concurs that disinfection by chlorine is still
the best guarantee of microbiologically safe water. |
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CASE STUDY
The Orange Water and Sewer Authority (OWSA) operates the Jones Ferry
Road Water Treatment Plant, located in Chapel Hill, NC. The plant serves
as a model for state of the art improvements and is routinely used as an
engineering maintenance example for the engineering students studying at
the local university and universities worldwide. The plant can treat up
to 20 million gallons of raw water daily, nearly double the average
demand of water usage from the local population of 70,000 people. The
water treatment process encompasses several phases. The first phase is
the addition of powdered carbon to the water supply from the lakes to
improve the taste and control odor in the water. Secondly, the solid
particles are separated from the water in settling tanks. Once that
process is complete the water is pretreated with sodium hypochlorite and
then filtered through layers of sand and anthracite coal. Lastly,
chemicals are added for disinfection and public health. The chemicals
include chlorine, ammonia, and fluoride.
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Diaphragm Hypo Pumps are Replaced
with Peristaltic Pumps
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The pretreatment stage consisted of a bank of ten
diaphragm pumps injecting sodium hypochlorite continuously and
simultaneously at a rate of 1.3 GPH
against zero back pressure. OWSA noticed numerous problems with the
diaphragm pumps in this particular application. The central issue
was the outgassing or off gassing of the sodium hypochlorite and the
inability of the diaphragm pump to operate efficiently due to the
gas build- up in the pump head. Enviably, a loss of prime would
occur, costing OWSA valuable down time. Despite the fact that
auto-degassing valves were implemented, the problem was not totally
eliminated. Consequently, the WTP chief operator, Dusty Martin, was
compelled to make the switch to peristaltic pumps. He was enticed by
the new technological developments that some of the peristaltic
pumps featured, such as Blue-White’s Flex-Pro A3V model. |
Bank of Ten Sodium Hypochlorite
Pumps
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First and foremost, the Blue-White
peristaltic pumps eliminate the core problem with outgassing of the
sodium hypochlorite by utilizing precision engineered rollers to
optimally squeeze a heavy duty Norprene tube with unparallel
accuracy and efficiently. Gas has no effect on this simplistic
pumping method. Furthermore, the tube life has been greatly
increased through an innovative rotor design that allows the pump to
handle the same maximum pressure in either direction. The ability to
reverse the motor, in essence, doubles the tube life. Of course, the
tube life will always vary depending on the chemical used, the
output pressure, the size of the tube, and the rpm of the motor.
Other notable advancements with Blue-White’s Flex-Pro A3V model
peristaltic pump include; a tube failure detection system built into
the pump head, increase output pressure of up to 125 psi, precision
SS ball bearings supporting the front and back of the rotor shaft,
and highly advanced electronics to connect to SCADA (Supervisory
Control and Data Acquisition) systems. |
Four Additional Hypo Pumps |
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At the Jones Ferry Road WTP, the
Blue-White Flex-Pro A3V peristaltic pumps are wired via 4-20mA into
the SCADA system for monitoring and alarm responses. Martin stated
that he was amazed how easily the peristaltic pump hooked up into
their SCADA system. Continual monitoring using powerful graphic and
alarm software programs allow the SCADA system to ensure the exact
amount of chemicals have been dispersed into the water supply. In
addition, Martin cites that the dosing is much more precise,
accurate, and consistent using a peristaltic pump compared to a
diaphragm pump. Overall, Martin highly recommends the Blue-White
Flex-Pro A3V peristaltic pump over a diaphragm pump for sodium
hypochlorite injection. |
Hypo Pumps Displayed on SCADA
System |
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Written by: Gary Rose
Rose Industrial Marketing, Inc.
10006 Cross Creek Blvd #423
Tampa, FL 33647
800-975-5469 Cell: 813-453-8419
Email: garycrose@msn.com
www.RoseIndMktg.com
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