Replacing Gas Chlorine with Onsite Sodium Hypochlorite Generation

Report
Replacing Gas Chlorine with
Onsite Sodium Hypochlorite
Generation
Tim Geraghty, P.E.
Division Manager
Alliance Water Resources, Inc.
Replacing Gas Chlorine with
Onsite Sodium Hypochlorite
Generation
 Goal: help other utility managers
decide if changing disinfectants would
be worth considering
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What made us consider a change
What options we considered
Costs & benefits
Design
Construction
Background
 Most water treatment
facilities use chlorine as
their primary disinfectant
 Chlorine use became
widespread in the early
1900’s
 Chlorine has a proven track
record
 Chlorine gas is a highly
hazardous chemical
Background
 St. Charles County, MO
Water Treatment Plant
has successfully used
chlorine gas in 1-ton
containers as a
disinfectant since 1941
 Plant capacity
 8 MGD average
 22 MGD peak
Water Treatment Plant,
St. Charles County, MO
1940
2013
They don’t build ‘em like they used to
Water Treatment Plant
1940
2013
Not much has changed
Background
 2005 - Water District
purchased the treatment plant
 2012 - Water District
completed an overall WTP
assessment
 Reviewed existing
condition of the plant
facilities & equipment
 Reviewed plant processes
 Developed and prioritized
a capital improvement
plan
Background
 Results of the plant assessment
 Electrical/efficiency upgrades
$1.4M
 Filter upgrades
$2.3M
 Booster pump station
replacement
$4.0M
 Replacement of the gas
chlorine feed system
$2.5M
 Lime, ammonia and fluoride
system improvements $0.9M
 Total
$9.7M
Why consider changing from
chlorine gas?
 Need to update existing
chemical processes,
controls and equipment
due to age
 Safety
 Employees
 People in the
surrounding
community
 Environment
Why consider changing from
chlorine gas?
1997 – one ton container split 25 miles away
in Kirkwood, Missouri
2012 – one ton container leaking 10 miles
away in Chesterfield, Missouri
Why consider changing from
chlorine gas?
2002 – leaking 1” hose connected to 90-ton
railcar 50 miles away in Festus, Missouri
48,000 pounds released - 63 people injured
Pictures from US Chemical Safety & Hazard Investigation Board Report, 2003
Why change?
Federal OSHA Safety Regulations
(TOSHA requirements may be more stringent)
EMPLOYEES
OSHA Process Safety
Management (29 CFR
1910.119)
 Respirators – fit testing,
medical baselines and
periodic evaluations
 Hot Work
 Confined Space
 Contractor Safety &
Record Keeping

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Coordination with LEPC
Management of Change
Chlorine Institute
Pamphlet 65 for PPE
Chlorine Institute
Pamphlet 155 for water
and wastewater operators
Training
Record keeping, record
keeping, record keeping
Why change?
Federal Safety Regulations - EPA
PEOPLE IN THE
SURROUNDING
COMMUNITY
US EPA Risk Management (in
section 112(r) of the Clean Air
Act)
 Worst case release
scenario
 Alternative release
scenarios
 Offsite consequence
analysis
 Estimating offsite
receptors
 Hazard reviews
 Operating procedures
 Compliance Audits
 Mechanical integrity
 Employee participation
 Coordinating with LEPC
 Communication with the
Public
 Regular re-submittals
Why change?
Protect the Environment
 Water Plant
 Missouri
Conservation
Department Wildlife Area
 US Army Training Area
 University
Research Area
 (added political
pressure from
regulators)

To decide if a
disinfectant
change was
worthwhile, we
reviewed our
goals and other
disinfectants
Review of Alternatives Water Quality Considerations
Requirements for disinfection
 Groundwater Rule
 4-log removal of viruses
 Chlorine contact time
 Effects of chlorination on pH
 Distribution system bacteria regrowth potential
 THM’s/HAA’s
 Nitrate formation
 Chlorite formation
Review of Alternatives Selection Criteria
Criteria
 Safety
 Life Cycle Costs
 Capital
 O&M labor
 Power
 Chemicals
 Waste
treatment/hauling
 Chemical & power cost
stability
 Chemical strength stability
 Chemical availability
Review of Alternatives Selection Criteria
Criteria
 Need for additional
treatment
 Level of automation
 Permitting issues
 Space requirements
 Operational flexibility,
familiarity &
simplicity
 Equipment reliability
Review of Alternatives
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Gas chlorine
Ozone
Ultraviolet (UV) Light
Chlorine dioxide
Hypochlorite
 Calcium hypochlorite
 Sodium hypochlorite
 Onsite hypochlorite
generation
 Bulk deliveries
 Combinations of the above
Review of Alternatives
 Gas Chlorine in 1-ton
containers (current practice)
 Advantages – low capital
and operating cost, simple
operation, low
maintenance
 Disadvantages – hazardous
and toxic chemical,
potential of leaks & high
level of regulation
Review of Alternatives
 Gas Chlorine in 150-pound cylinders
 Advantages – low capital and operating cost, simple operation,
low maintenance
 Disadvantages – hazardous and toxic chemical, potential of leaks
& high level of regulation
 Switching to smaller cylinders would reduce the quantity
released during a major leak, but more changeovers & handling
would be required
Review of Alternatives
 Ozone
 Expensive
 Additional disinfectant needed for
maintaining residual in distribution
 Often used to eliminate a specific
contaminant
 Ultraviolet (UV) Light
 Additional disinfectant needed for
maintaining residual in distribution
 Often used to eliminate a specific
contaminant
Review of Alternatives
 Chlorine dioxide
 Strong disinfectant
 Stops THM formation
 May require additional treatment for
chlorite
 Often used for pre-treatment – not as
the lone disinfectant
Review of Alternatives
 Bulk Sodium
Hypochlorite (typically
12.5% solution)
 Advantages – Low
capital cost, generally
safer than chlorine gas
 Disadvantages – High
operating cost,
degradation, corrosive
health hazard
Review of Alternatives
 Generated Sodium
Hypochlorite (0.8% solution)
 Advantages – no storage of
highly hazardous chemicals,
consistent product
concentration
 Disadvantages – High
capital cost, hydrogen gas
byproduct, short product
storage time
Review of Alternatives Process Schematic
Bulk hypochlorite
components
Onsite hypochlorite
generation components
Hazardous to Environment, Users, and Community
Chlorine Gas
NFPA Rating
Health = 4
Flammability = 0
Bulk Sodium Hypochlorite (11 - 15%)
0
4
NFPA Rating
0
OX
Instability = 0
Oxidizer
Health = Lethal
Short Term Exposure = Burns,
Chest Pain, Emotional
Disturbances, Lung Damage,
Death
Physical Hazards = Containers
may rupture or explode.
Health = 2
Flammability = 0
0
2
1
OX
Instability = 1
Oxidizer
Health = Intense or continued
exposure could cause
temporary incapacitation or
residual injury.
Instability = Can become
unstable at elevated
temperatures and pressures.
Environmentally Benign
0.45% Generated FAC
or
0.8% Generated FAC
NFPA Rating
Health = 1
Flammability = 0
NaCl (SALT)
NFPA Rating
0
1
0
Health = 1
Flammability = 0
0
1
0
Instability = 0
Instability = 0
Health = Exposure may cause mild
irritation
Health = Exposure may cause mild
irritation
Instability = Normally stable, even
under fire conditions.
Instability = Normally stable, even
under fire conditions.
Review of Alternatives
Comparison
Capital
Cost
Annual
O&M
Hazard Potential*
Chlorine Gas (add
$900,000
$50,000
highly hazardous gas
Ozone
High
High
limited
UV
Bulk Sodium
Hypochlorite
Generated Sodium
Hypochlorite
High
High
low
$650,000
$160,000
highly corrosive liquid
$1,900,000
$100,000
hydrogen gas by-product
scrubber & other controls)
Of these alternatives, only gas chlorine requires PSM & RMP programs
Review of Alternatives
Cost savings due to eliminating PSM training and
administration
 60 training hours annually for operators & maintenance
staff
 200 hours annually for contractor training
 100 hours annually for administration per year
 training reports, maintenance reports, PSM Manual updates,
PSM and RMP annual SOP certifications, periodic
resubmission of PSM and RMP documentation, internal
compliance audits, testing of chlorine sensors, …
 $10,000 - $15,000 per year
Review of Alternatives
 UV and Ozone were ruled out - high costs
+ additional need for residual disinfectant
 For the two hypochlorite alternatives,
onsite generation preferred because of
lower O&M
 Chosen Alternative: Onsite Generation
of Sodium Hypochlorite because of
reduced safety concerns; estimated
additional cost of treated water less than
$0.04 per 1,000 gallons (<1% of user
rate)
Design Considerations
First step – choose a hypochlorite generator manufacturer
 Equipment varies by manufacturer
 Major considerations
 Safety considerations
 Ease of operation/number of components
 Equipment footprint
 Life cycle costs
 Availability
Design Considerations
Choosing a hypochlorite generator manufacturer
The cost of materials varies by manufacturer but one pound of
chlorine is generated by roughly:
 15 gallons soft water (at 15-40 gpm and about 60 psi)
 3 pounds salt
 2 kilowatt-hours
Design Considerations –
Site Visits

Designers and operators
visited several installations of
various manufacturers
Design Considerations
Efficiency & Complexity

Indoor Equipment
(generators, blowers,
power and control panels)
 Room arrangement/
available space
 HVAC requirements &
equipment heat loss
 Outdoor Equipment
(tanks & accessories)
 Sunshades
Design Considerations
Sodium Hypochlorite Storage
Tanks
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Storage time
Degradation (esp. for 12.5%)
Sodium Hypochlorite Metering
Pumps
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Based on each feed point’s
chlorine demand
Sized for both 12.5% and 0.8%
solution
Design Considerations
Standby Options
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Standby generator
Provisions for bulk delivery
Plant Shutdown (generally
available at this location
September through May)
Capital Costs
 Equipment Bids
 ChlorTec (two 750 ppd units)$ 536,500
 MIOX (three 500 ppd units) $ 572,980
 PSI (two 800 ppd units)
$ 619,500
 Construction Bids (includes equipment)
 Engineer’s final estimate
 Low of 5 bids:
KCI Construction
$2,041,000
$2,213,500
Chosen Alternative - MIOX
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Simplicity / fewest components
Smallest footprint / able to fit most
equipment in the existing building
Design Considerations for Chosen
Alternative
System Control Panel Inputs
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Water hardness
Brine tank level
Storage Tank Level
System Components
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Brine pump
Generators/rectifiers
Hydrogen dilution blowers
Sodium hypochlorite storage tank level
Chosen Alternative - MIOX
Construction
 Construction Sequence
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Site work
Install outdoor hypochlorite tanks
Install new process piping and
metering pumps
Place bulk hypochlorite (12.5%)
system in operation
Remove existing gas chlorine
piping and equipment
Install hypochlorite generators in
the space vacated by the gas
chlorine system
Construction
Schedule and current progress
 Site work completed (relocated storm & sanitary sewers)
 Bulk tanks, piping, water softeners, pumps and dilution
panel installed
Construction
Schedule and current progress
 SOP’s written and operators trained in bulk chemical feed
process
 Bulk chemical (12.5%) and tanks being put in operation
next week
 Remaining work to be completed by July 2013
 Remove existing gas chlorination system
 Install hypochlorite generation and other equipment
inside the building and start-up
Key Points
Ultimately, the Water
District Board decided
that increasing the level of safety was worth
the additional capital and O&M costs
Our
chosen disinfection alternative was not
the lowest cost alternative
The
chosen manufacturer’s equipment was
not the lowest cost alternative
Involving
the operators in the decisionmaking was critical and strongly influenced
the decision
The
operators (and probably their spouses)
can’t wait for the workplace to be safer
For More Information
Tim Geraghty, P.E.
Division Manager
Alliance Water Resources
100 Water Drive
O’Fallon, MO 63368
636-561-3737 x101
[email protected]
www.alliancewater.com
Special Thanks to
Black & Veatch
and Parkson
Disinfection for
technical
information they
provided for the
presentation

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