Chlorination / DeChlorination
Procedures
-A New Twist to an Old TechnologyRobert Gordhamer
Measurement Technologies, Inc.
Redmond, Washington
Chlorination / Dechlorination
• Field Chlorination
– Forms of chlorine
– Reducing the amount of chlorine
– Methods of chlorination
• Field Dechlorination
– Discharge requirements
– Dechlorination chemicals
– Methods of dechlorination
FIELD CHLORINATION
• AWWA/ANSI C651-05
– Disinfecting Water Mains
• First standard approved Sept. 30, 1947
• Latest revision June 1, 2005
– Standards are reviewed every five years.
– AWWA standards describe minimum
requirements AND is not a SPECIFICATION.
Forms of Chlorine
Liquid chlorine (Cl2)...
Calcium hypochlorite (Ca(OCl)2)
granules or tablets...
Sodium hypochlorite (NaOCl)
solution...
*It is recommended that you follow the current AWWA C651 specification with the following modifications.
FIELD CHLORINATION
• Liquid Chlorine
– Least expensive with the highest danger.
– Requires specially trained treatment crews.
– Requires safety equipment for the operator
and all other personnel at the site.
– Requires containment container for cylinder.
FIELD CHLORINATION
• Calcium Hypochlorite (HTH)
– Available in two forms
• Tablets
• Granular
– Contains approximately 65% available
chlorine.
– Placed in pipeline during construction.
– Recommended to be used in pipe sizes to 24”
diameter.
FIELD CHLORINATION
• Sodium Hypochlorite
– Contains between 5% to 15% available
chlorine. (12.5% typical)
– Available in 1 qt. to 55 gallon containers.
– Must be stored properly to prevent
deterioration.
– Must be NSF 60, household bleach is not an
acceptable chlorine.
What determines how hot you
cook the line …
• Chlorine Residual Level…
– The specifier determines the chlorine
residual level the line should be targeted
for?
– Did your crews let dirt get into the pipeline
during the installation?
– Did you not seal the pipeline at night?
Could there be animals inside the line?
How can I use
less
Chlorine…
Alternate Procedures
Alternate Procedures
Disinfecting Water Mains
Basic Disinfection Procedure
1. Inspect materials to insure their integrity.
2. Preventing contaminating materials from
entering the watermain.
3. Remove, by flushing those materials that
may have entered the line.
4. Pressure test new installation.
5. Chlorinating the new installation
cont.
Disinfecting Water Mains
Basic Disinfection Procedure
6. Document that an adequate level of
chlorine contacted each pipe.
7. Flushing the highly chlorinated water
from the main.
8. Determining the bacteriological quality by
laboratory test after disinfection.
9. Final connection of the approved new
water main to the active distribution
system.
How do you COOK a line?
Tablet or Granular
Continuous-feed method
Slug method
NOW...
By using a
Modified Continuous-Feed
method.
• Mixes the chlorine solution with every
gallon of water that is filling your new
system. This will insure total contact at
the desired chlorine residual level.
Why use a combination
Venturi / Orifice Design?
Reliability
How does an Orifice design work?
The size of the orifice
determines performance.
How does a venturi design work?
The lateral by-pass venturi works by
combining two principles together…
• 2” Mainline orifice.
Plus three additional orifice insert…
And,
And the lateral by-pass venturi…
Side view Showing the mainline orifice ring.
Flow direction
This orifice directs
part of the water flow
into the lateral bypass venturi.
By inserting the smaller orifices you can
control your discharge rate OR increase bypass pressure to insure a full vacuum is
achieved.
Incoming water flow
Pressurizes the lateral by-pass to start the vacuum.
When the by-pass water
re-enters the main flow, it will
enter at the
higher incoming pressure.
The Pros & Cons of
Venturi / Orifice designs…
• The smaller the opening , the quicker you
get a vacuum, HOWEVER, you take away
high flow performance.
• The larger the opening, the higher the
flow must be before a vacuum is achieved.
This takes away low end performance.
Lateral By-Pass Venturi
Design with Mainline Orifice…
• FEATURES:
– Full vacuum throughout entire flow
range.
– Wide range of FLOW.
– Controllability of feed solution.
Lateral By-Pass Venturi
Design with Mainline Orifice…
• CONSISTENT FEED RATE:
– ONE GALLON per minute, FROM
START TO FINISH.
– Feed control valve allows for proper
balancing of feed solution.
– Gives operator the ability to make feed
solution strength based on flow.
Chlorinating Set-Up
Source Hydrant
Any length of
hose can be
attached in front
of the venturi
device...
Chlorinating Set-Up
Source Hydrant
No outside power
required when you
use a venturi style
device.
Enter point
Chlorinating Set-Up
Testing for CRL
• Locate sampling points, having the first
point within ten feet of the entry point.
• Number of sampling points to be
determined by the size of the project.
Set-up Discharge area
• You will need to discharge water from
the system during the chlorinating
operation.
• Some of this water will have a chlorine
residual level that needs to be
neutralized.
Entry Point
Device with Test Port
Taking a test sample
Procedure for chlorinating the
system
• Adjust feed control valve to full open position.
• Turn on the water supply to start filling.
• Test chlorine residual level at a sample point
within ten feet of the entry point.
• Follow Engineer’s specifications on the chlorine
residual level.
• Take test samples at selected sites throughout
the project.
• Adjust the control valve to increase or decrease
the amount of chlorine entering the system.
COOK
Dechlorinate
Liability
If you allow chlorinated water to be discharge
into the environment and you have not
enforced your state regulations, YOU will share
in the responsibility. OR, in other words the
fine.
This will be true for the consulting engineer, the
owner and the person or company that
discharges the chlorinated water.
EPA has set guidelines…
• The US-EPA has a recommended set of
guidelines.
– Each state has adapted there own standards.
– Some states, have even broken it down into
regions.
• However, all states have discharge limits
on chlorine or chloraminated water.
• AWWA is developing a new dechlorination
standard.
And, it’s good for the
Environment…
• Even a trace of
chlorine will kill fish.
• Your discharge
water effects the
beginning of the
food chain.
Washington, Oregon and Idaho’s
Requirements
• Regulation Standard:
– State Controlled
• DISCHARGE LIMITS:
– Fresh Water CMC (Acute)
• 19 ug/L
– Fresh Water CCC (Chronic)
• 11 ug/L
mg/L vs. ug/L
• mg/L means milligrams per liter
or parts per million (PPM).
1 mg/L = 1 PPM
• ug/L means micrograms per
liter or parts per billion (PPB).
1 ug/L = 1 PPB
Convert
ug/L (PPB) to mg/L (PPM)
• To convert micrograms per liter to
milligrams per liter, divide by 1000.
• 11 ug/L divided by 1000 = 0.011 mg/L
• 19 ug/L divided by 1000 = 0.019 mg/L
• .8 mg/L multiplied by 1000 = 800 ug/L
PPB
What you should
know…
So, you are going to specify DECHLORINATION.
There are many different styles of dechlorination
devices, so be sure, that if you specify a device
that it works at the chlorine residual levels that
will be encountered.
Liability
Consideration should be given to specifying
only the performance that is needed and
let the contractor determine what
equipment to use to achieve the chlorine
residual level specified for the discharge.
This way you do not assume liability on what
equipment was used.
Dechlorination
• Two major methods of Dechlorination
– Non-Chemical Dechlorination
• Only to be used for low chlorinated water.
• Chloraminated water can take 3 – 4 times longer to
decay the chlorine residual.
– Chemical Dechlorination
• Faster and more predictable method.
• Available in solid, liquid and gaseous forms.
• Works well with chloraminated water.
Non-Chemical Methods
for Dechlorination
•
•
•
•
•
•
Holding Tanks or Ponds
Land Applications
Groundwater recharge
Releases though hay bales
Discharge into Strom Sewers
Discharges into Sanitary Sewers
Chemical methods
for Dechlorination
Types of Chemical Dechlorination
•
•
•
•
Drip – style devices
Injection Pumps
Passive device
Vacuum - Induced
Forms of Dechlorination Equipment
• Passive
– A device which requires that the water
discharge to make contact with the
dechlorination chemical.
• Vacuum-induced
– Any device that produces a vacuum and
provides a means of controlling the flow of
dechlorination chemical.
Tablet style devices
Liquid Feed style devices
Dechlorination Chemicals
Common chemicals used in field dechlorination
Sodium Sulfite
Sodium Thiosulfate
Sodium Bisulfite
Ascorbic acid
Sodium Ascorbate
Calcium Thiosulfate
Why should you use only
environmentally safe chemicals
• We are neutralizing the chlorine to
protect aquatic life.
• We have to be aware of pH.
• NO effect dissolved oxygen in the water.
• Safe for humans to handle.
• Easier shipping and handling of freight.
What chemicals are safe for
aquatic life?
• Calcium Thiosulfate (Domestic)
– Liquid solution
• Ascorbic acid (Imported)
– Granular or tablet form
• Sodium Ascorbate (Imported)
– Granular form only
Cost comparison of chemicals that
are safe for aquatic life?
• Calcium Thiosulfate (Domestic)
– Low cost
• Ascorbic acid (Imported)
– Granular – three times the cost
– Tablet – five times the cost
• Sodium Ascorbate (Imported)
– Granular – over 6 times the cost
Basic Dechlorination Procedure
• The selected dechlorination process must be
able to neutralize the chlorine to levels below
0.01 mg/l.
• Testing needs to be done at the point of
discharge, the point you lose control of the water
flow.
• Spread dechlorination chemical in the path of
the discharge water to insure that the initial
water will make contact with the chemical.
Basic Dechlorination Procedure
• Make sure that either your feed solution or
your tablet chamber has the proper
amount of chemical to handle the chlorine
residual to be neutralized.
• Start your discharge and check your
chlorine residual at the discharge point.
• Make any adjustments that may require
proper neutralization of chlorine.
Basic Dechlorination Procedure
• If using a manufactured device follow the
manufacturers directions.
• Monitor chlorine residual at per determine
times during the discharge and record in
log book.
• When you achieve the desired chlorine
residual level in your discharge water, stop
flushing.
Required Equipment
• Proper dechlorination device that will
neutralize the chlorine residual.
• The proper amount of dechlorination
chemical.
• Proper chlorine test equipment that will
measure to 0.01 mg/l this means
TEN PARTS PER BILLION.
Set-up Discharge area
• You will need to discharge water from the
system during the flushing operation.
• Make sure that the area will handle the
amount of the discharge.
• Store chemicals properly.
• Set-up additional
monitoring
equipment.
Set-up
• Determine where the device will be located in
relationship to the discharge point from the outlet
of the system.
• It is preferred to have the discharge point away
from the device.
Set-up
• Testing for chlorine…
Testing your discharge
• If your test shows no chlorine, turn feed solution
control valve down until you show a sign of
chlorine in your discharge.
• Then open feed solution control valve a slight
amount to balance feed solution strength to
chlorine residual discharge.
• As you are flushing you may test your incoming
residual level of chlorine by drawing a sample
from the make-up water valve.
Always Dechlorinate when
discharging chlorinated water…
For more information:
Measurement Technologies, Inc.
P.O. Box 2195
Redmond, WA 98073-2195
877-889-VITC (8482)
425.836.8683
E-Fax: 425.484.6664
www. H2ONeutralizer.com
© 2009