DDW-2025-002761

Disinfection
Pre-certification Training
Pathogenic
Disease causing organisms
Includes viruses, cysts, or bacteria
Causes diseases such as typhoid, cholera and dysentery
Organisms that don’t cause disease are non-pathogenic
Process to kill is called disinfection
Bacteria
Organism Disease Primary Source
Shigella Bacillary disentary Human Feces
Salmonella Salmonellosis Human/animal Feces
E. Coli Gastroenteritis Human Feces
Vibro Cholerae Cholera Human Feces
Viruses
Organism Disease Primary Source
Hepatitus A Infectious Hepatitis Human Feces
Coxsackievirus A&B Aseptic meningitis Human Feces
Rotavirus Gastroenteritis Human Feces
Adenoviruses Upper respiratory & Human Feces
Gastrointestianilln
Protozoans
Organism Disease Primary Source__
Giardia lamblia Giardiasis Human/animal Feces
Cryptosporidium Cryptosporidiosis Human/animal Feces
Entamoeba Aomebic dysentary Human/animal Feces
histolytica
Methods of Detection
Membrane Filter
Test
Multiple-tube
Fermentation Test
Colilert, P/A
Disinfection
Process to kill or inactivate most microorganisms in water.
There are several ways to disinfect
Chlorine is most popular method because of cost and it leaves a residual throughout the system
Other methods include UV and ozone
Methods of Disinfection
Heat; boiling
Radiation; UV light
Chemical
*Bromine
*Ozone
*Chlorine Dioxide
*Chloramination
*Iodine
Oxidizing Reagent Oxidizing Potential
Ozone 2.00Permanganate 1.67 Hypobromous acid 1.59 Chlorine dioxide 1.50 Hypochlorus acid 1.49 Chlorine 1.36 Oxygen 1.23 Bromine 1.09Hypochlorite 0.94

What is OZONE?
Ozone is a natural
component of the
earth's upper
atmosphere, where it is
primarily formed photo
chemically.
Ozone doesn’t leave a
lasting residual
Ozone
Ozone or trioxygen
molecule contains three
oxygen atoms, having
the chemical symbol
O3.
Ozone is nothing more
than another molecular
form of oxygen, the
chemical symbol for
oxygen is O2.
UV
Is the only method of
disinfection that does not
alter the pH, taste, or affect
the chemical composition of
water.
Operates best when
Suspended Solids is <10 – 15
mg/L & Turbidity is <5 – 10
NTU.
Gas Chlorine Properties
Heavier than air
Used primarily for disinfection
Boiling Point -34 C , -29 F
Liquid form expands 460 times
Lowers pH of the water
Testing and Safety
When changing
cylinders, shut gas off
at cylinder first,
evacuate lines
DPD kit to test residual,
should take samples
from several locations,
reagent turns
chlorinated water pink
SCBA should be stored
away from chlorine
building
Three Types of Chlorine
Calcium Hypochlorite or HTH (High Test Hypochlorite) Dry Powder 65%
Sodium Hypochlorite is Liquid:
*Bleach 5%
*T-Chlor 15%
GAS 99.9% considered 100% for calculations
*extremely corrosive with water/humidity
*compressible
*changes to liquid at 82 psi
*68 deg. F
*2.5 times heavier than air
*greenish-yellow color
* Must meet NSF approval
Chlorine Terms
Free Chlorine- chlorine remaining in water after chlorination
Total Chlorine- sum of combined residual chlorine & free available chlorine
Demand- difference between the chlorine added and the chlorine remaining
Chlorine Processes
Pre-chlorination-
injected prior to
treatment
Post-chlorination-
injected after treatment
Breakpoint chlorination-
amount of chlorine
added to the water until
the demand is satisfied.
Breakpoint Chlorination Graph
Chlorinators
Gas- Dry or Direct Feed (uses pressure from cylinder) *Solution feed -gas mixed w/H2O under pressure -vacuum feed the water pulls Cl2
Hypochlorinators - Dry or Liquid Uses
-Systems with Low flows -Emergencies -Intermittent- seasonal (winter use)
-Clean deposits on pump parts with an acid solution

Note air intake at top, exhaust fan at bottom, ammonia
bottle for checking leaks (vapors look like white smoke).
Cylinders chained down, wrench on shutoff, exhaust fan
near the floor.
Chlorine Scales
Typical Hypochlorinator
Safety Hazards
When chlorine comes in
contact with petroleum
or other combustibles,
the reaction can cause a
fire
When mixed with
hydrogen sulfide it
reacts to cause sulfuric
acid
Chloramines
Formation of chloramines is a chemical
reaction
The reaction is between hypochlorous
acid (or aqueous chlorine) with
ammonia.
Formation of chloramines weakens the
disinfecting strength of chlorine
Chloramination
Cloramines are a reaction
between applied chlorine
and ammonia
When done intentionally it
can reduce tastes and
odors
Chloramines are a weaker
disinfection than chlorine
Disinfection By-products
TTHM- Total
Trihalomethanes
Combination of free
chlorine and
organics
Warmer
temperatures and
pH form THM’s
faster
Reducing Agents
Readily give up electrons
Opposite of oxidizing agents
React with chlorine
Cause a demand on chlorine
Ferrous, Nitrite & Hydrogen Sulfide ions are examples
Suspended Solids
Chlorine reacts with hydrogen sulfide to form sulfuric acid
5 Principles of Chlorine
Disinfection
Concentration
Contact time
Temperature of the water
pH of the water
Foreign substances in the water
Concentration & Contact Time
If chlorine concentration is decreased then the contact time must be increased
Longer detention times would have higher bacteria kill rates
A minimum of 0.2 mg/L leaving the chlorination station and a measurable residual should be maintained at the extremities of the distribution system
Chlorine penetrates the cell wall
Dt = volume (in gallons) / flow rate (in gallons/time)
Temperature
Low temperatures the bacteria
kill rate is lower
Chlorine residual will remain
longer in cold water
Chlorine dosages should be
adjusted with changes in water
temperatures
Higher temperatures cause
faster rates of THM formation
pH
pH should be checked routinely
If the pH of the water system is
raised for corrosion control, then
the chlorine dose needs to be
raised to maintain an effective
level
Chlorine is most effective at a
pH of 7.0
Turbidity
Chlorine is effective only if it comes in contact with bacteria
Turbidity can prevent good contact time and
protect pathogens
Chlorine also reacts with
organic matter & ammonia
Can mask the bacteria
Gas Chlorine System
150 lb. Chlorine Cylinders:
The proper position for the
withdrawal of chlorine gas is
upright.
Maximum feed rate is 40
lb/day for each
A yoke is the connection
between the tank &
regulator or gas piping
Chlorine Cylinder Valve
Always inspect the cylinder valve
before opening.
Check cylinder fittings for leaks
with ammonia gas
Once the connection has been
made, the valve should only be
opened 1/4 of a turn & check for
leaks.
Close cylinder valve first to allow
gas drain from pigtail
Fusible Plug
Safety Device
Made out of lead
Melts between 160 to
165 degrees
Keep cylinders away
from direct heat
150 lb. Cylinder Valve
Maximum Chlorine Feed Rates
When the feed rates
exceed the maximum
rates icing can occur
For higher feed rates
you can manifold the
cylinders in a series to
prevent icing
85% Full for Expansion
One Ton Cylinder
6 fusible lead plugs- 3
on each end
Valves are aligned
vertically
Upper is for gas
Lower for liquid
85% full for expansion
Weigh 3550 lbs. full
Chlorine Cylinders
Rupture or tank failure
most serious type of
leak
For leaks on ton
chlorine cylinders,
rotate the cylinder until
leak is on top
400 lb/day max feed
rate for each ton
cylinder
Ton cylinders on scales
Rotometer for Ton Cylinders
Rotometer, continued
Scales, Ton Cylinders
Chlorine Ejector
Evaporator
Ton Cylinder Lifting Bar
Lead Gasket
Never re- use a lead gasket.
Never stack lead gaskets on top of each
other
Tighten connection 1/2 to 3/4 of a turn
after making contact with the lead
gasket
Preventive Maintenance (PM)
After one year of service, pm kits
should be installed
Always use new diaphrams, o-
rings, etc. “Never re-use parts”
O-rings need to be made of viton
Use special grease to lube o-ring
before installing
Inspect pvc parts for damage or
cracking
Use an acid solution to clean
parts
Chlorine Train Cars
C kit for repairs
Used for larger sized
plants
Repair Kits
A kit for 150 lb.
B kit for ton
cylinders
C kit for train cars
150 lb Cylinder A Kit
Ton Cylinder Valve Repair
Respirators
Canister type masks should be worn during the changing of cylinders
Canister type masks should be used only for escape purposes only, because they
don’t work in an oxygen deficient environment
SCBA’s or fresh air masks should be worn for repairs, troubleshooting, and finding leaks
Self Contained Breathing Apparatus
(SCBA)
Never enter a room
suspected of leak
without SCBA
PVC Piping
Only corrosion resistant piping should be
used
Schedule 80 PVC is not recommended in
chlorine
Plastic can deteriorate in a relatively short
period of time
Schedule 80 PVC is used because of the cost
& should replace every 5 to 10 years.
Polyvinyldene Fluoride (PVDF) should be
used
Chlorine Institute sets standards for piping,
valves, & manifolds
Chlorine Valves
Should be replaced or
maintained annually
Stainless Steel
300 have useful properties
for low temperature
service
Can fail due to chloride
stress corrosion cracking
Particularly in the presence
of moisture at ambient or
elevated temperatures.
Water Needs to be Metered
New & Repaired Water Mains
Disinfected in accordance with AWWA standard C651
Must be disinfected with some type of chlorine
Tablet or a solution are typically used
Chlorine must be flushed with potable water
Take bacti samples
Reservoir Maintenance
After entry reservoir
must be disinfected
AWWA standard C652
Take bacti samples
Disinfection
Prevent Contamination
From Entering Pipe During
Construction Or Repair
Flush Out Contamination
Chlorinate Pipe For
Required Time
Flush Out Super Chlorinated
Water
Determine Bacteriological
Quality
Prevent Contamination
Keep pipe clean and dry
Plug pipe ends when not working
Use only approved pipe lube
Clean and swab pipes as necessary
Keep trench dewatered while working or disinfect
submerged pipe
Keep a positive pressure in pipe when doing repairs if possible
Flushing
Flush at a velocity 2.5 fps or greater
Required gpm flow for velocity
4" pipe 100 gpm
6" pipe 200 gpm
8" pipe 400 gpm
10" pipe 600 gpm
12" pipe 900 gpm
CHLORINE NEUTRALIZING
CHEMICALS
SULFUR DIOXIDE
SODIUM BISULFITE
SODIUM SULFITE
SODIUM
THIOSULFATE
Fluoride
Fluoride shall not exceed 4 mg/L
If fluoride levels exceed 2 mg/L, the water system must notify the public.
Water system must notify the public in their first set of water bills after the violation
Must provide specific health effects language
Over Feeding Fluoride
Can Mottle Teeth