Municipal water decision makers now face the choice
of which dechlorination method to
employ in their water system maintenance program and emergency spill
plan. AWWA standards issued in 2010 now require that most field water
discharge be dechlorinated before release into the local environment.
This issue involves a choice between two fundamental approaches to water
dechlorination, passive and active; the two primary categories all
methods available fall into. The following discussion reviews important
points to consider when choosing between passive or active treatment
The primary difference with these two approaches lies in how chlorine is
neutralized. Passive dechlorination involves bringing a portion of the
water into contact with chemical which then mixes with the main flow of
water which neutralizes chlorine as the chemical dissolves and
disperses. Active dechlorination involves preparing neutralization
chemical for injection into waters through a mechanical device, causing
neutralizing chemical to mix with water as it passes through the device.
Passive treatment can also be done by holding waters in open impoundment
and letting chlorine oxidize and break down naturally, but time and
space requirements make it impractical.
The remainder of this discussion will explore mechanical devices used
for dechlorination and will compare the practicalities of passive versus
active equipment.
Passive
DeChlorination
Passive dechlorination involves bringing a
portion of the water into contact with chemical which then mixes with
the main flow of water which neutralizes chlorine as the chemical
dissolves and disperses.
Passive treatment can also be done by holding
waters in open impoundment, but this approach requires more time and
space for water storage and dechlorination than is practical in the
majority of situations.
This approach works adequately for low level
residual chlorine at medium to high flow rates.
Active DeChlorination
Active devices rely on preparing neutralizing
chemical as liquid solution for injection into discharged water. A
mechanical injection device draws water by vacuum from the solution
supply and injects it into the main discharge stream as it passes
through the device. In most cases mixing is so thorough and chlorine
neutralization so complete that the water can be released directly to
the local environment without additional holding time.
Cost
of Owenership
Passive
Devices
Because of their relative simplicity passive
devices have lower cost to manufacture and frequently less expensive
than active devices. Their performance range varies with each device
and typically only neutralizes potable drinking water. If you are going
to protect the environment, ascorbic acid tablet would be the choice of
chemical however that will come with the highest cost in chemical.
Active
Devices
More complex and higher tolerance, active devices
are preferable when large volumes of water with high or low chlorine
residual levels are involved. Their primary strength is in achieving
complete mixing within the tube of the injector device. Active devices
also offer the user to use the lowest in cost and most environmentally
safe dechlorination chemical with a wider performance range than passive
devices, and some models can be used for chlorination as well as
dechlorination.
Which Method to Choose
Selecting a device should be based on three
dominant areas of concern, 1)Total Cost of Ownership, 2)ease of use,
3)overall chemical consumption. For operators dealing only with low
flows and residual levels passive dechlorination can be cost effective,
given the availability of sufficient time and holding capacity for
complete neutralization of residual chlorine to occur.
For the remainder of situations one is likely to encounter,
active dechlorination offers many advantages.
First issue of importance is lower overall chemical
consumption.
Because active
devices more closely meter chemical into the discharge stream less
chemical is needed to treat the same volume of water as that needed for
passive dechlorination.
Because of time constraints often faced in passive treatment it is
frequently necessary to use more chemical than active treatment
requires, to reduce chlorine residual to levels necessary for release,
within the time constraints of the project.
Active devices are frequently easier to use because
once set they meter a consistent volume of chemical into the discharge
stream based on water flow rate.
Passive treatment requires constant monitoring to assure chemical
is replenished as it dissolves.
Tablet and granulated chemical can dissolve at variable rates
over the period of treatment and must be continually replenished as
chemical dissipates into solution. With active treatment one only needs
to stage the quantity of chemical needed to complete each leg of
discharge treatment, setup the equipment and wait for necessary volume
of water to pass through the equipment.
A number of firms manufacture and sell
dechlorination devices. For
a more complete discussion of each and their capabilities download our
free report, Making the Right Choice in Field Dechlorination.
It offers a complete comparison of each manufacturer’s equipment
and discusses the performance range of each.
Making the right choice
While the different devices discussed in our free
report Making the Right Choice in Field Dechlorination each have strong points, one manufacturer’s
active dechlorination device offers the widest range of performance and
chlorinates as well as dechlorinates.
The H2O Neutralizer from Measurement Technologies offers the
widest range of performance of all devices currently available.
Built with a patented venturi induction design, the H2O
Neutralizer has no moving parts and works based on the natural physics
of flowing water. Relying
on the same principals as old fashioned vehicle carburetors to draw
liquid from an external reservoir into the main discharge flow, the H2O
Neutralizer requires no electrical or mechanical power to operate.
With a wider range of performance and the most
consistent draw rate of all active treatment devices, the H2O
Neutralizer has the lowest Total Cost of Ownership of any dechlorination
device currently on the market.
To review what the H2O Neutralizer can do to meet
your chlorination and dechlorination needs and get your free copy of
Making the Right Choice in Field Dechlorination visit our website at
www.h2oneutralizer.com and
learn more about how our active dechlorination system can help you meet
your needs.
Special offer - 30 Gal. of
No-Chlor CTS
with your Trade in...
Trade in any of the other devices reviewed in
Making the Right Choice in Field Dechlorination, with your purchase of an H2O Neutralizer,
and receive thirty gallons of
No-Chlor Calcium Thiosulfate DeChlorination
Solution free when we receive your trade-in.
Municipal water decision makers now face the choice
tion
Active DeChlorination
Cost
of Owenership
Active
Devices
Active devices are frequently easier to use because
once set they meter a consistent volume of chemical into the discharge
stream based on water flow rate.
chlorinates as well as dechlorinates.
The H2O Neutralizer from Measurement Technologies offers the
widest range of performance of all devices currently available.
Built with a patented venturi induction design, the H2O
Neutralizer has no moving parts and works based on the natural physics
of flowing water. Relying
on the same principals as old fashioned vehicle carburetors to draw
liquid from an external reservoir into the main discharge flow, the H2O
Neutralizer requires no electrical or mechanical power to operate.
To review what the H2O Neutralizer can do to meet
your chlorination and dechlorination needs and get your free copy of
Making the Right Choice in Field Dechlorination visit our website at
Trade in any of the other devices reviewed in
Making the Right Choice in Field Dechlorination, with your purchase of an H2O Neutralizer,
and receive thirty gallons of