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

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 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

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

Background

They don’t build ‘em like they used to

Water Treatment Plant,St. Charles County, MO

1940 2013

Not much has changed

Water Treatment Plant

1940 2013

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?

Pictures from US Chemical Safety & Hazard Investigation Board Report, 2003

2002 – leaking 1” hose connected to 90-ton railcar 50 miles away in Festus, Missouri

48,000 pounds released - 63 people injured

Federal OSHA Safety Regulations (TOSHA requirements may be more stringent)

EMPLOYEESOSHA Process Safety

Management (29 CFR 1910.119) Respirators – fit testing,

medical baselines and periodic evaluations

Hot Work Confined Space Contractor Safety &

Record Keeping

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 - EPAPEOPLE 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)

Why change?

To decide if a disinfectant change was worthwhile, we reviewed our goals and other disinfectants

Water Quality ConsiderationsRequirements for disinfection

Groundwater Rule 4-log removal of viruses

Chlorine contact time Effects of chlorination on pH

Distribution system bacteria re-growth potential

THM’s/HAA’s Nitrate formation

Chlorite formation

Review of Alternatives -

Selection CriteriaCriteria 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 CriteriaCriteria

Need for additional treatment

Level of automation Permitting issues

Space requirements Operational flexibility,

familiarity & simplicity

Equipment reliability

Review of Alternatives -

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

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

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

Review of Alternatives

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 CommunityChlorine Gas

NFPA Rating

Health = 4

Flammability = 0

Instability = 0

Oxidizer

Health = Lethal

Short Term Exposure = Burns, Chest Pain, Emotional Disturbances, Lung Damage, Death

Physical Hazards = Containers may rupture or explode.

4

0

0

OX

Bulk Sodium Hypochlorite (11 - 15%)

NFPA Rating

Health = 2

Flammability = 0

Instability = 1

Oxidizer

Health = Intense or continued exposure could cause temporary incapacitation or residual injury.

Instability = Can become unstable at elevated temperatures and pressures.

2

0

1

OX

Environmentally Benign

1

0

0

NFPA Rating

Health = 1

Flammability = 0

Instability = 0

Health = Exposure may cause mild irritation

Instability = Normally stable, even under fire conditions.

0.45% Generated FACor

0.8% Generated FAC

1

0

0

NaCl (SALT)

NFPA Rating

Health = 1

Flammability = 0

Instability = 0

Health = Exposure may cause mild irritation

Instability = Normally stable, even under fire conditions.

Comparison Capital Cost

Annual O&M

Hazard Potential*

Chlorine Gas (add scrubber & other controls)

$900,000 $50,000 highly hazardous gas

Ozone High High limited

UV High High low

Bulk Sodium Hypochlorite

$650,000 $160,000 highly corrosive liquid

Generated Sodium Hypochlorite

$1,900,000 $100,000 hydrogen gas by-product

Review of Alternatives

Of these alternatives, only gas chlorine requires PSM & RMP programs

Review of AlternativesCost 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 ConsiderationsFirst 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 ConsiderationsChoosing 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 ConsiderationsEfficiency & Complexity

Indoor Equipment (generators, blowers, power and control panels) Room arrangement/

available space HVAC requirements &

equipment heat loss Outdoor Equipment

(tanks & accessories) Sunshades

Design ConsiderationsSodium Hypochlorite Storage

Tanks Storage time Degradation (esp. for 12.5%)

Sodium Hypochlorite Metering Pumps Based on each feed point’s

chlorine demand Sized for both 12.5% and 0.8%

solution

Design ConsiderationsStandby Options

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 $2,041,000 Low of 5 bids:

KCI Construction $2,213,500

Chosen Alternative - MIOX

Simplicity / fewest components Smallest footprint / able to fit most

equipment in the existing building

Design Considerations for Chosen Alternative

System Control Panel Inputs Water hardness Brine tank level Storage Tank Level

System Components Brine pump Generators/rectifiers Hydrogen dilution blowers Sodium hypochlorite storage tank level

Chosen Alternative - MIOX

Construction Construction Sequence

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

ConstructionSchedule and current progress

Site work completed (relocated storm & sanitary sewers) Bulk tanks, piping, water softeners, pumps and dilution

panel installed

ConstructionSchedule 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 PointsUltimately, the Water District Board decided that increasing the level of safety was worth the additional capital and O&M costsOur chosen disinfection alternative was not the lowest cost alternativeThe chosen manufacturer’s equipment was not the lowest cost alternativeInvolving the operators in the decision-making was critical and strongly influenced the decision The operators (and probably their spouses) can’t wait for the workplace to be safer

For More InformationTim 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