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Mahnomen Community Water System
Disinfection By-Products (DBPs)……..
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What, why, risks
Options
Questions????
Current Wells
& Treatment
Plant
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Population: ~236
Connection Types:
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52 residential
1 commercial
2016 Annual Water Production: 4,622,400
Avg. gallons per day (gpd): 12,664
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Per capita rate of ~53 gpd
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Source Water:
 Two (2) wells:
 6” casings
 Well 1- 166’ (cased to: 157’)
 Well 2- 158’ (cased to: 148.5)
Treatment:
 Three (3) softening units to remove
 Originally: Iron, Manganese, and Tannins (i.e. a type of organic)
 Currently: Hardness, Iron, Manganese & Ammonia
Storage:
 Two (2) Hydro-pneumatic tanks providing 1,584 gallons of capacity
 Post-chlorinate, fluoridate , and inject clearitas (after softening treatment)
Distribution:
 2,160 LF of 8” water main
 1,086 LF of 4” water main
 8,288 LF of 6” water main
The what??
 DBPs are by-products that are formed when
organic matter comes in contact with chlorine.
 Two (2) types are monitored in your drinking
water:
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Total trihalomethanes or TTHMs
Haloacetic Acids or HAA5
Not tested for because they are the most dangerous or
harmful, rather they are common and easy to test for.
The Why??
Where does the organic matter originate?
 Two (2) sources
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Anthropogenic:
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Naturally occurring:
 Man-made sources
 Water ……the ‘universal solvent’
 “leaches” various minerals and chemical from its
surroundings….i.e. woody debris, leafy matter, microbes,
soils, others……..
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Mahnomen source water is high in Total Organic
Carbon (TOC) or Natural Organic Matter (NOM)
Common scenarios that can cause DBP MCL
exceedances when chlorinating water:
High TOCs or NOM (terms are used interchangeably in
some online public literature)
Long contact time between TOCs and chlorine
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Example: slow turnover of water towers, or long residence
time in watermains
Higher chlorine dosing
Chlorinate for disinfection
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Protects against bacteria, viruses, and other pathogens
Why are they regulated by the EPA then?
 As a precautionary measure to protect public
health and safety.
 Suspected to be, but are not yet conclusively
proven to be a carcinogen.
What are my risks?
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USEPA uses a risk benchmark to help set drinking
water regulations (Maximum Contaminant Levels)
based on the lifetime probability of developing cancer
10-6 or a 1 in 1 ,000,000 (0.000001%)
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chronic
low level doses
Lifetime (70 years)
People with compromised immune systems, have an
infant, are pregnant, or are elderly, should seek advice
from your health care provider(s) about drinking this
water.
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The FDL Medical Director issued a letter and
identified one potential high risk group.
“There is a concern for risk for short term
exposure to these by-products during pregnancy.
The amount of risk is not certain. If pregnant
women are concerned, it is recommended they
drink bottled water during their pregnancies.”
How much is a microgram per liter (µg/L)?
 One part per billion or ppb
 1 ppb = 1 drop of water in an Olympic-size
swimming pool
Mahnomen Community Water System:
Contaminant
EPA MCL
TTHMs
Mahnomen WTP
RAA
129.6 µg/L
HAA5s
61.5 µg/L
60 µg/L
80 µg/L
Removing DBPs?
 There are two (2) proven removal options:
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Aeration
Activated carbon filters
These types of treatment would have to be
installed at each home.
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Not operationally optimal for maintenance
Becomes less optimal as community grows
Reducing DBPs in the interim……..
 Operational controls
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Increase water main flushing via hydrants
 Reduces contact time
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Decrease chlorine dosing at the water
treatment plants
 Reduces chlorine concentrations
 Required to maintain a minimum 0.2 µg/L free
residual----again, to maintain disinfection
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Other options considered:
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Stop Chlorinating (short-term or long-term solution)
 By doing this, DBP precursors (aka organic matter) will
not have a chance to combine with the chlorine and
form DBPs
 We would now lack disinfection and no longer be
protected from bacteria, virus contamination and other
pathogens.
Long-term solution:
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Finding a better source via new wells
Reevaluate water treatment options.
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All positive effects on our water treatment plant
Would allow us to chlorinate without exceeding the
DBP Maximum Contaminant Levels (MCLs).
Use less chlorine and other products to treat our
drinking water which makes your WTP more
efficient.
Short-term:
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Continued operational adjustments (i.e. flushing and chlorine concentrations)
-Increased quarterly monitoring per USEPA Safe Drinking Water Act
-Increased chlorine residual sampling at sample taps
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Researching Point-of-Use water solutions:
 Berkey Water filter/purification units
 Pur (FM-4500L)
 Culligan (Culligan FM-15A)
 Brita (42202)
 Bottled water
Long-Term:
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Commence with surveying of the area (April/May 2017)
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Ice pigging this spring/summer (contractor dependent)
 Awarded $41,000.00 from IHS
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Drilling of pilot wells (4) and source water testing (June 2017)
 Awarded $83,000.00 from USEPA
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Planning activities will follow well testing this (Fall 2017)
 Planning will depend on water quality results
Proposed
Pilot Well
Sites
Proposed
Pilot Well
Sites
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Contact
FDL Water & Wastewater Department
Jordan Vandal, FDL Water/Wastewater Mgr.
218-878-7595
Surveying of your neighborhood
 Ongoing
 IHS and FdL staff performing survey
 Provide accurate data for
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Ice pigging of the water mains
Planning activities, short-term and long-term
Ice pigging
 Uses an ice slurry to clean water mains
 IHS Special Project funding obtained for
$41,000.00.
 Work anticipated for spring or summer 2017
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Dependent on contractor’s schedule
We will notify residents of any water outages
in advance.
Exploratory Well Drilling
 IHS funded planning project for $83,000.00.
 Drill 4 wells to test for viability as a new water
source.
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capacity and water quality
Contractor bids received today 4/17/2017
Anticipate construction soon, spring 2017
Planning activities
 Results of planning project will be used to
determine possible solutions.
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Evaluates water quality and capacity tests
Evaluates community growth
Evaluates 20-50 year plan
Anticipated to occur this fall and winter.