Post on 15-Jan-2016
Gregory Korshin and Steve ReiberGregory Korshin and Steve Reiberkorshin@uw.edu, reiber@comcast.net
(partly based on materials prepared for the American Water Works Association, AWWA)
Drinking Water Treatment Drinking Water Treatment
in Small Utilities: a Review of Considerations in Small Utilities: a Review of Considerations
Typical for the United StatesTypical for the United States
Requirements for small water utilities in the United States
Water quality and treatment are under control of Water quality and treatment are under control of
the U.S. Environmental Protection Agencythe U.S. Environmental Protection Agency
The mission is to provide safe drinking water The mission is to provide safe drinking water
and protect public health.and protect public health.Small utilities must comply with the maximum contaminant Small utilities must comply with the maximum contaminant
level (MCL) established by the EPA for many contaminantslevel (MCL) established by the EPA for many contaminants
Regulations are same for large and small utilities, with some
exceptions
Water systems with < 15 connections (buildings) or serving < 25
people at least 60 days per year (campgrounds, schools,
summer houses) are not regulated under the National Primary
Drinking Water Regulations.
U.S EPA regions
10 EPA regions and 50 state
agencies
State regulations may be State regulations may be
much more stringent than much more stringent than
those the EPAthose the EPA
California is a typical
example
Very concerned with perchlorate,
Cr (VI), emerging contaminants
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Roles and Responsibilities under Safe Drinking Water Act (SDWA)
EPA sets health-based drinking water standards and oversees state programsEPA sets health-based drinking water
standards and oversees state programs
State environmental/public health agencies – Primary enforcement
responsibility/implement standards
State environmental/public health agencies – Primary enforcement
responsibility/implement standards
Public water systems are the regulated entity
Public water systems are the regulated entity
Consumers – Ultimate end-usersReceive benefits/pay costs
Consumers – Ultimate end-usersReceive benefits/pay costs
SDWA – Multiple Barrier Approach
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Source ProtectionSource ProtectionTreatmentTreatment
DistributionDistribution Consumer Consumer ProtectionProtection
Turb. Turb. Disinf
ectionDistribution
Small system definitions
US EPA defines small water systems as US EPA defines small water systems as
those serving less than 3,300 population. those serving less than 3,300 population. In 2011, small water systems (>60,000 in total) had
significant problems:
They contributed to 95% of all community water systems
with monitoring and reporting violations
93% of systems with an maximum contaminant and
treatment technique violations.
Violations of Total Coliform Rule ranked the highest (48%)
Chemical Contaminant Group (25%),
Disinfectants and Disinfection Byproduct Rule (16%).
Issues typical for small utilities
For small water systems several issues are For small water systems several issues are
challenging: challenging:
Complying with monitoring and reporting
requirements;
Compliance with several EPA rules such as:
Total Coliform Rule,
Lead and Copper Rule
Radionuclide Rule
and many new regulations.
Special Challenge for Small Utilities: Arsenic Rule
Arsenic Rule Introduced in 20010.01 mg/L (or 10 ppb)5 years given to comply (Feb 2006)Includes non-community/non-transient water systemsCosts to utilities exceeding $ 5.4 billionSampling requirements- Annual for surface waters- Every three years for groundwater
Occurrence of arsenic in the US (red dots correspond to As> 1ppb)
Arsenic occurrence mapPopulation density in the United States (>
317 million total)
Outline of the “New” Arsenic Rule
The standard applies to 20,000 non-community systems that
serve at least 25 of the same people more than six months of
the year.
Schools, churches, nursing homes, and factories.
The EPA estimates that 5%, of these water systems, serving 2 million
people, have taken measures to meet the new arsenic standard.
This EPA rule applies equally to small and large This EPA rule applies equally to small and large
systems. Of the affected systems, 97% are small systems. Of the affected systems, 97% are small
systems that serve < 10,000 peoplesystems that serve < 10,000 people.
The rule does not apply to individual household well The rule does not apply to individual household well
systems, of which there are at least 50 million in the US.systems, of which there are at least 50 million in the US.
Exemption table
Major arsenic removal technologies
Coagulation/filtrationCoagulation/filtration
Excellent for point-of-entry treatment
Requires more sophisticated equipment and
training
Ion exchangeIon exchange
Can be highly efficient
Good for point-of-entry and point-of-use
applications
Problems in costs, high sulfate, brine handling
Adsorption Processes
AdsorptionAdsorptionRelatively popular As treatment method
A variety of excellent materials are available
Needs equipment, trained personnel, disposal of
spent media, may be costly
Sorption Processes: Adsorptive Media
Iron based mediaIron based media Granular Ferric Hydroxide, GFH (Siemens)E-33 (Severn Trent), Chemiron
Regenerable Iron coated Regenerable Iron coated resin resin (Solmetex)Iron Modified Activated Iron Modified Activated Alumina Alumina (Alcan)Other activated alumina Other activated alumina productsproductsOther adsorbents
Realities of implementation of the arsenic rule
Many of the small utilities with As issues did the Many of the small utilities with As issues did the
followingfollowing:
The high arsenic wells are frequently abandoned.
Or to blend with water from lower arsenic wells to bring
the blend below the 10 ppb MCL.
Adsorption of ferric hydroxide based media is Adsorption of ferric hydroxide based media is
relatively popularrelatively popular
But the adsorbent is pricey, and used on critical wells.
Arsenic Treatment Experiences (EPA)
EPA Treatment Demonstration EPA Treatment Demonstration
StudiesStudies
50 selected water systems in the US
31 Adsorption (62%)
2 Ion Exchange (4%)
15 Oxidation/Coagulation/Filtration (30%)
2 Reverse Osmosis (4%)16
Arsenic Treatment in the Washington State
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Realities of implementation of the arsenic rule
Ion-exchange is relatively rare Ion-exchange is relatively rare
Costs, sulfate and other limitations
Very few small systems resorted to ROVery few small systems resorted to RO
Too expensive for most systems.
If they got federal funding to do so, they may
buy an RO system.
Typically, federal funding is available for Indian
tribal reservations.
Occurrence of fluoride in the US (red dots correspond to F> 0.4 ppm)
Maximum contaminant Maximum contaminant
level for fluoride is 4 ppmlevel for fluoride is 4 ppm
Many utilities add fluoride Many utilities add fluoride
for dental healthfor dental health
Some people do not like this
Added fluoride
concentration close to 0.8
ppm
May be reduced to 0.6 ppm
Removal of fluoride
If high fluoride is an issue, the well is If high fluoride is an issue, the well is
usually abandoned. usually abandoned.
If this is not an option, then one of the one of the
few solutions is activated alumina. few solutions is activated alumina.
Maintaining an activated alumina system Maintaining an activated alumina system
is a serious chore for a small system.is a serious chore for a small system.
Point-of-use devices (e.g., “under the
sink” cartridges or small reverse osmosis
system) are popular with some people
Activated alumina columns (also good performance for arsenic)
Removal of salinity
Secondary MCL of 1000 mg/LSecondary MCL of 1000 mg/L
High salinity is a huge problem in High salinity is a huge problem in
many countries but genetally less so in many countries but genetally less so in
the USthe US
Very few utilities use reverse osmosis
Typically high salinity sources are Typically high salinity sources are
abandoned or blendedabandoned or blended
Point-of-use devices are also popular
Small systems and US realities
Most areas of North America have Most areas of North America have
reasonably abundant water sources. reasonably abundant water sources.
If a source becomes insufficient, an If a source becomes insufficient, an
alternative source is typically developed.alternative source is typically developed.
This will change due to global climate effects
and population growth.
Over 95% of small systems take water
directly from the ground, chlorinate and
distribute.
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Drinking Water – Missions and Visions
America’s America’s drinking water drinking water is safe, is safe, affordable, and affordable, and secure secure everywhere, everywhere, every day and every day and Americans Americans know it.know it.