Cross-connection Control for Wastewater Treatment Plants

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Cross-connection Control for Wastewater Treatment Plants
Cross-connection Control for
Wastewater Treatment Plants
Department of Health Mission
We work with others to
protect and improve the
health of all people in
Washington State.
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Presentation Overview
•
•
•
•
Descriptions
Requirements
The Project
Common Deficiencies
Descriptions
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Wastewater Treatment Plants
• Many of the wastewater treatment and collection
facilities are now old and worn, and require
improvement, repair or replacement to maintain
their useful life.
• The character and quantity of contaminants
presenting problems today are far more complex
than those that presented challenges in the past.
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Wastewater Plant Schematic
RAS/WAS Pumps
Digesters
Secondary Clarifier
Solids Handling
Primary Clarifier
Head works
Aeration Basin
Backflow Incidents
• Hundreds of incidents documented
– USC CCC Manual (2009)
– EPA’s CCC Issue Paper (2002)
– PNWS-AWWA Incident Manual (1995)
• Incident impacts
– Health
– Costs of investigation and clean-up
– Litigation
• Incidents are under-reported
– Not detected or not reported
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Reported WA Backflow Incidents
Cause and Number
Number of Reports (1996-2017)
74
Caused by backpressure
51
Caused by backsiphonage
18
Unknown cause
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• Corpus Christi and Chicago
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BACKFLOW AT A WASTEWATER
TREATMENT PLANT
• In December 1983, effluent from a wastewater
treatment plant in San Antonio, Texas,
backflowed into the potable water system at the
plant because of maintenance activities.
• Eight employees reportedly suffered
gastrointestinal problems. Fortunately, a reducedpressure principle backflow-prevention assembly
was in place at the water service connection to
the plant. This assembly contained contamination
within the plant site.
Requirements
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CCC at Sewage Facilities
Cross-connection control (CCC) at sewage
facilities has two functions:
• Protecting the public potable water system
from contamination
• Protecting the onsite domestic potable water
system from contamination.
Basis
Three concepts form the basis for cross-connection
control at sewage facilities.
• The public water supply is protected by premise
isolation RPBAs and RPDAs and in-plant air gaps.
• On-site domestic potable water is protected by
RPBAs and in-plant air gaps.
• Actual or potential connections to sewage, process
water or toxic chemicals are downstream of an air
gap.
Potable Water
• Do not use potable water for purposes other than
drinking, personal hygiene and emergency
washing facilities.
• Laboratory usage is permissible provided that the
laboratory supply line is fitted with an RPBA and,
where appropriate, there are in-lab air gaps.
“Ideal” Situation
Complicated Situation
The Orange Book
• Must locate air gaps, RPBAs and RPDAs above
ground level
• Must locate premise isolation backflow preventer
adjacent to meter or property line
• Supply all hose bibs, wall hydrants, and yard
hydrants, whether above or below ground,
interior or exterior, through an air gap
The Orange Book
“Facility designs must include a pressurized
water system supplied through an air gap to
facilitate cleaning or flushing of wet wells, dry
wells, tanks, basins and equipment.”
Reclaimed water
• Must protect potable water from reclaimed
water as if reclaimed water were sewage
• Reclaimed water is protected as if reclaimed
water were potable water
Potable Water
• Recommended that designers locate all
potable water piping at ground level or above
to prevent future inadvertent cross
connection.
• Do not route city water/potable water piping
through wet well areas to prevent future
inadvertent cross-connection.
Emergency Washing
• Designers should try not to locate emergency
washing facilities(eye wash stations/showers)
below ground level.
• If designers cannot avoid locating emergency
wash stations below-ground must
demonstrate that the installation will protect
potable water supplies from accidental
contamination.
Irrigation
• Irrigations systems may use non-potable water
taken downstream of a backflow preventer,
disinfected plant effluent, reclaimed water or
stormwater collected within the facility’s
perimeter.
• Ecology discourages use of potable water for
irrigation; such use must include an RPBA.
Fire Protection
The water supply to any fire protection system
must be equipped with an RPBA located and
installed in accordance with the requirements
for the premise isolation backflow preventer.
Chemicals and Substances
• Properly equipped water systems used with,
connected to, or have the potential to come into
contact with hazardous chemicals and substances
• Proper equipment includes supplementary air
gaps and backflow prevention devices
appropriate to the degree of hazard that would
result if those chemicals were to backflow into
the facility piping systems
Odor Control
• Odor control involves sewage aerosols and
particulates. Water supplied to odor control
equipment or to hose bibs in the odor control
area is considered to be in direct contact with
sewage.
• Water supplied to odor control areas and
equipment must utilize an air gap.
WAC 246-290-490 (4)(b)
(ii) For service connections to premises posing a
severe health cross-connection hazard including
wastewater treatment plants, radioactive material
processing plants, and nuclear reactors, the
purveyor shall ensure that either an:
(A) Approved air gap is installed for premises
isolation; or
(B) Approved RPBA or RPDA is installed for
premises isolation in combination with an inplant approved air gap.
Project
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Background
• Since 2007, ODW has collected cross-connection
control data from the largest community water
systems on the status of backflow prevention at
wastewater treatment plants.
• Water systems self-report their CCC data and
ODW has not independently verified the
information reported
Project Goals
• Perform CCC hazard surveys of 47 severe health
hazard facilities
• Evaluate self-reported data for the associated
PWS
• Report findings to ODW, PWS, and the facility
surveyed
• Compile data to determine:
– Program effectiveness.
– Guidance, training, and resources needed.
– Compliance with regulations.
Process
• Contact the public water system CCS and
discuss project.
• Contact WWTP operator with PWS CCS to
discuss the project.
• Gather as much information as available to
review before the survey.
• Perform survey of the facility.
• Write survey report.
• Send report to all parties.
Findings
Deficiencies
Total found in
all plants
Number of
plants
% Of Plants
Improper air gaps (majority of problem was
not enough distance between outlet and
flood rim)
14
12
41%
No RPBA prior to air gap
8
5
17%
Moving RPBA for hydrant tested annually
3
3
10%
Improper protection for Chemical Injection
4
3
10%
RPBA's installed below ground
31
18
62%
Access restricted
0
0
0%
Potential spoolpiece connection
2
2
7%
Improper protection for Pump seal water
4
4
17%
Valves installed downstream of AVB
5
4
14%
Findings
Deficiencies
Total found in
all plants
Number of plants % Of Plants
No hosebib vacuum breaker
14
8
28%
No RPBA for laboratory
12
9
31%
Double check on hydrant construction
1
1
3%
Non potable pipe before fire sprinkler
1
1
3%
Complicated piping
1
1
3%
Processed water to eye station
1
1
3%
Washdown water not air gapped
4
4
14%
Premise Isolation not at property line
2
2
7%
Reclaimed an potable supplied to restroom
1
1
3%
Data
• 29 surveys have been performed
• 72 percent of facilities did not meet the
regulations
• All facilities were up to date on their backflow
assembly testing
• 88 percent of water systems coordinate with their
authority having jurisdiction
• 84 percent of systems have a Quality
Control/Quality Assurance Program
Common Deficiencies
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Spool Piece
RPBA Not at Property Line
Direct Connection to Sewer Line
Improper Assembly
Improper Assembly
Proper Air Gap
Air Gap Below Flood Rim
Improper Air Gap
Air Gap Below Ground
Air Gap Defeated
No Hose Bib Vacuum Breaker
No Hose Bib Vacuum Breaker
RPBA Located Below Ground
Improper Protection for Chemical
Injection
Proper Labeling
Improper Labeling
Pump Seal Water
Pump Seal Water
Eye Wash Stations
Corroded Assembly
Odor Control Station
Auxiliary Water Supply
Access To Assemblies
Mystery Assembly
Unable to Maintain
Direct Cross Connections
Autoclave
Shut Off Valve Moved
Shut Off Valves Removed
Bypass
Valve Downstream of AVB
No HBVB
Old Service Line
References
• Department of Ecology, Criteria for Sewage
Works Design
• Washington Administrative Code
• Washington Department of Health/Office of
Drinking Water Guidance
• Uniform Plumbing Code Amended for
Washington State
• Manual of Cross connection Control (University
of Southern California)
• AWWA (American Water Works Association)
Yellow Book
Contact Information
Scott Hemingway
Washington Environmental Training Center
Director
253-288-3381
[email protected]
Bill Bernier
Operator Certification and Training
Distribution/CCC Advisor
360-236-3562
[email protected]
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Questions?
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