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Small System Treatment
Technology Selection
Does the System Really Want to Be in the
Water Treatment Business?
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Alternatives to Treatment
• Improve Source Water Protection
• Improve System Operation and
Maintenance (0 & M)
• Switch to Higher Quality Source
• Purchase Water
• Consolidate
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7
7
Go Forward with Treatment Selection if
No Practical and Economically Attractive
Alternatives to Treatment of a Current or
New Water Source Exist
-------
Factors Influencing Treatment Selection
• System Characteristics
• Impact of Upcoming Rules
• Characteristics of Proposed Treatment(s)
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Compliance Timeline
•00 '01 '02 '03 '04 '05 '06
lESWTR _.
•07
•08
•09
Stage 1 DBPR
Radon
t Filter Backwash Recycling Rulg
_ LT1ESWTR
Radionuclides
Arsenic
GWR
LT2ESWTR
Stage 2 DBPR
Period during which
systems achieve
compliance with rule
Additional period which
State may grant an
individual system to
achieve compliance
through capital
improvements
-------
Characteristics of Proposed Treatment(s)
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Ability to Reliably Achieve Compliance
Costs (Capital, O&M, Waste Disposal)
Complexity and Flexibility
Environmental Compatibility
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Case Study
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System Characteristics
- CWS, surface water,
serves 2,500
- Conventional filtration
with chlorine
disinfection
- Raw TOC averages 3.2
mg/l
- Alkalinity averages 95
mg/l
• Compliance Concerns
- TTHMS average 0.085
mg/l
- Treated TOC averages
2.3 mg/l
- Turbidity is not less than
0.3NTU95%ofthe
time
- Turbidity excursions on
individual filters
• Observations
- Must reduce finished
water TOC
- Address turbidity
-------
Treatment Options Analysis -
Case Study
Chlorine,
Coagulant Aid,
Poiymer
Water
Source(s)
Mixing, Flocculation
Sedimentation
PH
adjustment
Final
Disinfectant
Distribution
System
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Treatment Options Analysis -
Case Study
Chlorine,
Coagulant Aid,
Polymer
Water
Source(s)
Mixing,
Flocculation,
Sedimentation
PH
adjustment
Final
Disinfectant
Distribution
System
10
-------
Treatment Options Analysis -
Case Study
Water
Source(s)
Chlorine.
Coagulant Aid,
Polymer
Mixing,
Flocculation,
Sedimentation
Final
ph Disinfectant
adjustment
Distribution
System
11
Treatment Options Analysis -
Case Study
Water
Source(s)
Chlorine,
Coagulant Aid,
Polymer
Mixing,
Flocculation,
Sedimentation
adjustment
Filter
Rna!
Disinfectant
Distribution
System
12
-------
Treatment Options Analysis -
Case Study
Water
Source(s)
Chlorine,
Coagulant Aid,
Polymer
I
»
Mixing,
Flocculation,
Sedimentation
Final
p" Disinfectant
adjustment
Distribution
System
13
Treatment Options Analysis -
Case Study
Chlorine,
Coagulant Aid,
Polymer
Final
pM Disinfectant
adjustment
Distribution
System
ym
T
Mixing,
Flocculation.
Sedimentation
14
-------
Treatment Options Analysis -
Case Study
Chlorine,
Coagulant Aid,
Polymer
Final
Disinfectant
Distribution
System
I
Mixing,
Flocculation,
Sedimentation
15
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Conventional Treatment
• Pros:
- Removal
capabilities
-Ability to treat
source waters of
low or inconsistent
quality
• Cons:
- Advanced operator
- Adequate land
- High costs
- Sludge disposal
16
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Membrane Filtration
• RO, NF, UF, MF
• Pros:
- Removal capabilities
- Size and flexibility
- Intermediate operator
• Cons:
- Water rejection
(RO & NF)
- Pre-treatments
- Waste disposal
(RO & NF)
- High costs
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Pros:
- High removal rates
- Low cost
- Intermediate
operator
Cons:
- Co-contaminants
- Brine disposal
18
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Disinfection
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I. Type
- Chemical
• Chlorine
» Chloramines
• Chlorine Dioxide
• Ozone
- Non-chemical
• uv
• Membranes
II. Purpose
- Primary
- Secondary
19
Chemical Disinfection
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Pros:
- Compliance with GW and
TC rules
- Low cost (chlorine,
chloramines)
- Oxidation
Cons:
- DBF formation (especially
chlorine, chlorine dioxide)
- Additional disinfectant
(ozone, chioramines)
- Handling dangerous
chemicals
20
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10
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Ultraviolet Light Disinfection
• Pros:
- No THM precursors
- Easy & safe operation
- Generally low cost
• Cons:
- No residual disinfectant
- Not appropriate for
waters high in TSS or
turbidity
- High doses required for
cyst inactivation will
increase costs
21
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Granular Activated Carbon
Pros:
- Effective removal of SOCs, VOCs, Radon
- Improved aesthetic quality
- Relatively low cost
Cons:
- Co-contaminants may interfere with adsorption
of selected contaminants
- GAC must be replaced periodically
22
11
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Centrally Managed POU
• Pros:
- Generally more cost
effective for very
small systems
• Cons:
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- Significant
maintenance,
oversight, and
customer education
required
- Not approved for
microbial removal
23
Centrally Managed POE
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Pros:
- Generally more cost
effective for very
small systems
Cons:
- Significant
maintenance,
oversight, and
customer education
required
— Some states may
restrict disposal
options for certain
devices
24
-------
External Challenges:
Other Issues
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Source Water Supply
Achieving Competitive Efficiency
New Source Development
• Surface Sources
- Many environmental, regulatory, and social
barriers
• Ground water Sources
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- Aquifers are limited and may be overdrawn
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Source Conservation Is a Better Option!
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