Why Optimize in the
Distribution System?
XXX
Distribution System Field Event
June 8, 2010
What is Optimization?
• An approach for water systems to voluntarily improve
drinking water quality beyond compliance levels to
enhance public health protection.
• Optimization is achieved through enhanced process
monitoring and control using existing staff and facilities.
Performance is measured relative to optimization goals.
• Program began in 1989 with turbidity optimization (0.1
NTU) at surface water treatment plants. Now the EPA’s
Technical Support Center supports a voluntary
optimization program that provides technical tools and
implementation approaches in 21 states.
• For this project we are focusing on maintaining
disinfectant residual and reducing disinfection byproduct
(DBP) formation in the distribution system.
Why Optimize in the Distribution System?
Alamosa, CO Case Study
• Alamosa, CO Waterborne Salmonella Disease Outbreak
– 442 reported illnesses, 122 laboratory confirmed
– Estimated 1300 may have been sick
– 20 hospitalized, 1 death
• System Description:
– Serves 8,900 plus 1,000 through
purchase systems
– Groundwater, deep artesian wells
– Disinfection waiver since 1974
– 3 Storage tanks (1 ground level)
– 50 miles of pipe
• In compliance with all regulatory
requirements, except arsenic
• Total coliform samples were
negative prior to the outbreak
Series of Events
• March 14, 2008 – 3 cases of
salmonellosis reported to Alamosa
County nursing service
• March 15-16 – “Active surveillance” for more cases
• March 17 – Water system was most likely source
– Alamosa directed to take TC samples by SDW response team.
– Emergency response team was deployed including – CO Dept
of Public Health & Environment, Alamosa County, CO Division
of Emergency Management, CO National Guard, and others.
With all elements of a managed disaster response under FEMA
guidelines.
• March 18 – 43 cases and 18 confirmed
• March 19 – Two of 10 samples were TC positive,
Bottled water advisory issued, CoWARN activated, city
and county emergency declared.
Series of Events (cont’d)
• March 21 – System disinfection (at 25
mg/L) and flushing begins (all pipes
and tanks). Governor declares
emergency.
• March 23 (Easter Sunday) – Tank
repairs and cleaning. System-wide
survey for cross connections.
• April 2 – Disinfection and flushing
efforts are completed.
• April 3 – Boil water advisory begins
• April 11 – Boil water order lifted, with
provisions: ground tank disconnected
from system, two elevated tanks to be
repaired, chlorination of wells to
begin, ongoing DS monitoring.
Source: CDPHE
Salmonella
• Spread through human/ animal feces,
rarely spread through drinking water
• Symptoms include fever, diarrhea,
and abdominal cramps. May last 4-7
days. Most need no treatment, some
may require hospitalization. Death is
rare.
• Strain of Salmonella found exists in
the natural environment in the western US
• Sample results (DNA pattern) indicate it is likely a
single source of contamination
• Infective dose for small child 10 to 100 organisms
• Feces of an infected bird could contain 10 million to 1
billion organisms per gram.
• Bacterial growth favorable in tank sediment and
biofilm
Suspected Cause of Outbreak
• Contamination of Weber
Reservoir (ground storage
tank)
– Cracks and holes in
structure to allow small
animal or water to carry
contamination into tank (via
snowmelt?)
– Evidence of wildlife near
tank
– Salmonella contamination
was found throughout the
system
– Only the Reservoir supplied
the entire system (~75% of
distributed water was from
the Reservoir)
Why Optimize in the
Distribution System?
• Lessons Learned from Alamosa,
CO
– It didn’t take much to infect the
system (1 bird?)
– In the Alamosa, CO; Gideon,
MO; and Cabool, MO
waterborne disease outbreaks
routine coliform monitoring did
not indicate a problem.
– A significant team (from all over
CO) had to be put together to
provide an alternate water
supply, collect and measure WQ
samples, make repairs, clean
tanks, disinfect and flush the
system, and notify citizens.
– The citizens and businesses
were without safe drinking water
for nearly 3 weeks.
Why Optimize in the
Distribution System?
• (Some) Costs of Alamosa
Outbreak:
– City of Alamosa - $185,256
– City of Alamosa (lawsuit) - $360,000
– County - total??
• Road & Bridge Dept - $45,000
• County Nursing Service - $34,000
– State Health Dept - ~$300,000+
– Div of Emerg Mgmnt - $215,000
– Grant money:
• $100,000 from CO Health Foundation
• $300,000 from CO Emergency
Declaration
• Community Impact
–
–
–
–
4 of 27 restaurants closed
All 6 schools closed
4 of 6 daycares closed
No businesses closed
Community Impact as of March 25th, 2008
120
100
80
60
40
20
0
closed
total
Businesses
Restaurants
Day Care
Schools
Govt.
Facilities
Lodging
Medical
Facilities
Vet
0
4
4
6
0
0
0
0
112
27
6
6
5
18
15
2
Why Optimize in the Distribution
System? (cont’d)
• The Statistics…
– On average, from 1971 to 2002, a distribution-related
outbreak caused 152 illnesses, with the largest causing
as many as 5000 illnesses (Craun et al., 2006)
– From 1971 to 2000:
• Excluding the Milwaukee outbreak, distribution system
deficiencies were associated with 75% of the total deaths
related to waterborne disease outbreaks (12 of 16)
• Salmonella and E. coli accounted for most deaths (EPA,
2007)
– The main distribution system-related deficiencies were
(Craun and Calderon, 2001):
• Cross connections and backsiphonage (53%); storage
facilities (13%); corrosion (12%); broken or leaking water
mains (9%); contamination of service lines or household
plumbing (7%); main construction, repair, or flushing (5%);
and inadequate water main and sewer separation (1%)
Why Optimize in the Distribution
System? (cont’d)
• The distribution system is the last barrier
to public health protection.
– Protecting the physical barrier/ infrastructure
from contamination (e.g., maintaining
pressure, preventing backflow, protecting
storage tanks, etc) and
– Providing a disinfection barrier against
contamination and water quality deterioration
Why Optimize in the Distribution
System? (cont’d)
• “This couldn’t happen to us, we provide a chlorine
residual in the DS”
– Adequate Barrier is Needed:
• Studies indicate that a free chlorine residual of 0.2 to 0.5 mg/L is
needed to provide adequate protection against microbial
contamination (Baribeau, 2005).
• Systems that maintained free chlorine residual of greater than 0.20
mg/L had at least 50% lower rate of coliform occurrence
(LeChevallier, 1996)
– DS Impacts are Real:
• Pipe material (e.g., cast iron) and water age decrease free chlorine
residual and increase heterotrophic bacteria (HPC) (Baribeau,
2005).
– Maintenance is Critical:
• Episodes of chlorine depletion could increase bacterial resistance to
disinfection (Codony, 2003).
Important to maintain (and monitor!) residual
Why Optimize in the Distribution
System? (cont’d)
• Balance between DBP formation and Microbial
Contamination
– DBPs are formed when chlorine (or other disinfectant)
reacts with organics (total organic carbon) in the
water.
Increasing chlorine = increased DBPs!
– Potential DBP-related health concerns include
suspected carcinogens (bladder cancer) and
reproductive and developmental disorders.
– Actions taken to lower water system DBP levels by
reducing disinfectant residual levels could
compromise microbiological water quality.
Decreasing chlorine = increased microbial risk!
Purpose of Field Event
• For the field event team, collect information and
gain experience on:
– Key technical challenges including:
• Finished water quality (assessing the impact on distributed
water quality)
• Distribution system monitoring (identifying areas with poorer
water quality and capturing water quality with grab samples
and continuous chlorine monitors),
• Tank hydraulics and operations (assessing the impact on
distributed water quality)
• Establishing the foundation for an evaluation approach for
distribution systems
Purpose of Field Event (cont’d)
– Key non-technical challenges including:
• Demonstrating the importance of the distribution
system on maintaining water quality and public
health
• Understanding who might be the distribution
system optimization “champion” at the water
system
• Identifying potential barriers to implementing
distribution system optimization at a water system
• Illustrate the importance of proper distribution
system sampling
References
Baribeau, H., Gagnon, G., Hofman, R., and Warn, E. (2005). Impact of Distribution System
Water Quality on Disinfection Efficacy. Awwa Research Foundation, Denver, CO.
Centers for Disease Control and Prevention. (1991-2006). Surveillance for Waterborne
Disease and Outbreaks Associated with Drinking Water and Water not Intended for
Drinking. Morbidity and Mortality Weekly Report. Reports dated 1991-2006. From
http://www.cdc.gov/mmWR
Codony, F., Morato, J., and Mas, J., Role of Discontinuous Chlorination on Microbial
Production by Drinking Water Biofilms., Water Research 39 (2005) 1896-1906.
Craun, M., Craun, G., Calderon, R., and Beach, M. (2006). Waterborne Disease Outbreaks in
the United States. Journal of Water and Health, 04.Suppl 2, 2006. Retrieved August 14,
2009 from
http://www.epa.gov/nheerl/articles/2006/waterborne_disease/waterborne_outbreaks.pdf
Craun, G. and Calderon, R. Waterborne disease outbreaks Caused by Distribution System
Deficiencies. Journal AWWA, September 2001.
U.S. EPA. 2007. Estimating the Burden of Disease Associated with Outbreaks Reported to the
U.S. Waterborne Disease Outbreak Surveillance System: Identifying Limitations and
Improvements. U.S. Environmental Protection Agency, National Center for Environmental
Assessment, Cincinnati, OH. EPA/600/R-06/069.
Falco, R. and Williams, S. (November 2009) Waterborne Salmonella Outbreak in Alamosa,
Colorado March and April 2008: Outbreak Identification, Response, and Investigation.
From http://www.cdphe.state.co.us/wq/drinkingwater/pdf/AlamosaInvestRpt.pdf
LeChevallier, M.W., Welch, N.J, and D.B. Smith, Full-Scale Studies of Factors Related to
Coliform Regrowth in Drinking Water, Applied and Environmental Microbiology, p. 22012211, July 1996.
National Research Council. (2006) Drinking Water Distribution Systems Assessing and
Reducing Risks. Washington, DC: National Academies Press.
City of Alamosa 2008 financial report
http://www.about-salmonella.com/salmonella_outbreaks/view/alamosa-colorado-municipalwater-system-salmonella-outbreak/)
Pueblo Chieftain article from May 2, 2008 “Cost figures for salmonella outbreak trickle in”