07-26-2010 Public HearingCity of Woodburn
Water Supply Disinfection Project
Public Hearing
July 26, 2010
th
Presented by
Melinda Friedman, P.E.
Confluence Engineering Group, LLC
Presentation Key Points
Summary of Existing Conditions
?
Biological Activity and Habitat
?
Recommended System Improvements and Rationale
?
Treatment
?
Operations and Maintenance
?
2
Maintaining Water Quality from
Source to Tap is Difficult!
Numerous chemical,
?
biological, and physical
reactions
Changing conditions as
?
systems expand and age
Conflicting and
?
competing regulatory
compliance requirements
Varying customer
?
expectations
Source: Darren Lytle, USEPA, Nov. 2008
3
Scale/Biofilm Accumulation in Pipes
Served by Groundwater Sources
Examples of Discolored Water
Source: Darren Lytle, USEPA, Nov. 2008
Source: Darren Lytle, USEPA, Nov. 2008
Source: R.V. Anderson Assoc.
Safe Drinking Water Act
Multiple Barrier Approach
6
The Disinfection Barrier
Acute Illness/Exposure:
Within the
?
Rapid health response to exposure
?
distribution system,
Severely ill at low levels (no safe level)
?
disinfection is
Susceptible populations at high risk
?
perceived by the
drinking water
Microbes
industry as a “risk
trade-off”
Chronic Illness/Exposure:
Provides protection
?
Long-term exposure (lifetime) for health response
?
from “acute”illness
Increased riskof certain illnesses
?
threat, at the
No adverse health effects expected if standards met
?
expense of potential
“chronic”illness
Disinfection Byproducts
threat
7
Disinfection is an Industry Best
Management Practice
US EPA and Centers for Disease Control
believe the benefits of drinking water
disinfection outweigh the potentialrisks
from disinfection byproducts
8
Woodburn Water Quality –
Summary of Issues
History of naturally-occurring iron, manganese,
?
arsenic, organic carbon, and ammonia in source water
Iron, manganese, and arsenic filtration installed in 2005
?
Ammonia and carbon still present
?
Three coliform events in 2005/2006
?
E. colipresent -Boil water notice in May, 2005
?
Approximately 2,000,000 gallons of water flushed during
?
August, 2006 event
On-going sporadic elevated heterotrophic bacteria
?
2006 midge fly larvae discovered in distribution system
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Nutrients in source water and accumulated scale/biofilm
in distribution system result in elevated levels of
biological activity
9
Distribution System Monitoring
Monitoring conducted 24-March and 31-March 2010
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Locations selected for broad system coverage
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Entry-point at each WTP
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Elevated reservoir (draining)
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Avg. and max. residence time
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Dead-ends
?
Results confirmed significant biological activity
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Heterotrophic bacteria (use carbon as food source)
?
Flushed solids from Woodburn
Nitrifying bacteria (use ammonia as food source)
?
distribution system
Habitat for biological growth (accumulated iron and
?
manganese scales, biofilm, and sediments)
10
Evidence of Nitrification
?
Complete conversion of NHNO
-
?
33
System colonized with ammonia and nitrite oxidizing bacteria
?
11
Bulk Water Microbial Conditions
Heterotrophic Plate Count (HPC) Bacteria
?
HPC indicate robust biofilm presence
?
12
Other Water Quality Conditions
Aesthetic Conditions
?
Generally good at the time of sampling
?
Iron and color were non-detectable in all samples
?
Odor was elevated at Parr 12
?
Presence of elevated microbes despite aesthetically
?
acceptable water at time of sampling
Total Organic Carbon
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Consistently high (~ 3 mg/L) in all samples
?
Disinfection Byproduct precursor
?
Contributes to disinfectant demand
?
Contributes to biofilm and HPC growth
?
13
Effectiveness of Chloramine for
Control of Biofilm
Chloramine and chlorine decay curves
?
Bench-scale HPC inactivation tests (R2A)
?
14
Disinfection Byproduct Formation
15
Conclusions
Source water quality contributes to microbial growth
?
in distribution system
Lack of disinfectant
?
Presence of naturally-occurring nutrients
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Ammonia
?
Organic carbon
?
Historical loading of iron and manganese
?
Significant habitat within distribution system to
?
support ongoing microbial growth
Cannot be removed through flushing alone
?
16
Assessing Flushing Effectiveness –
Manganese Scale on Plastic Pipe
After
Before
17
Photo of iron sludge : Pre-and Post-flushing
Source: Friedman and Hill et al., 2003.
Water Research Foundation
Soft, iron sludge layer easily removed, leaving a layer of
?
tuberculation underneath which was not amenable to
removal by flushing
Recommendations and Rationale
–Multifaceted Approach
19
Questions/Discussion
20
Supporting Materials, Photos,
Handouts
21
Overview of Disinfection
Issues
AdvantagesDisadvantages
Significantly improves New/Different tastes
??
microbial quality of and odors
distributed water
Formation of some
?
Increased public health disinfection byproducts
?
protection
Need to dechlorinate
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Enhances compliance for certain uses
?
with existing and future
Increased treatment
?
regulations
costs
Provides tool for
?
responding to water
quality upsets
22
Disinfection Options –
Chloramines
Chloramine AdvantagesChloramine Disadvantages
Utilizes existing May need supplemental
??
ammoniaammonia
Long-lasting, less Careful control of
??
reactivedosage needed
Better permeation of May have future
??
biofilmsnitrification events
Fewer chlorinous taste
?
and odors
Significantly lower
?
regulated Disinfection
Byproduct Formation
23
Disinfection Options –Free
Chlorine
Free Chlorine AdvantagesFree Chlorine Disadvantages
Stronger disinfectantIncreased regulated
??
Disinfection Byproducts
Potentially better dose
?
controlHigh dosage needed to
?
remove ammonia
Avoid/remediate
?
nitrificationLess stable residual
?
24
Woodburn Crew Setting Valve
Positions for Flushing
Water is a Perishable Product
Agenda Item #: 10A -Water Supply System Disinfection
PUBLIC TESTIMONY SIGN -IN SHEET
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Agenda Item #: 10A -Water Supply System Disinfection
PUBLIC TESTIMONY SIGN -IN SHEET
I N FAVO R
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