Compliance Strategies for Stage I

1
Compliance Strategies for Stage I II DBPR4
Case Studies

• William Bellamy
• CH2M HILL

2
DBP Compliance Case Studies

• Aurora Colorado - Chlorine dioxide
• Casper Wyoming - Enhanced coagulation and inline
  ozone
• Henderson Nevada - UV
• Denver Colorado - Optimized chlorination /
  chloramination

3
Case StudyAurora Colorado

• Direct filtration plant
• Chlorine primary disinfection
• Chloramine residual disinfectant

Drivers

• THMs can be as high as 90 ug/L
• Disinfection with chlorine and chloramines is
  minimal

4
Disinfectant Evaluation - Chlorine

• Advantages
• Current practice no change in technology
  required
• Does not form chlorite
• Does not form bromate

• Disadvantages
• Relatively weak disinfectant- not capable of
  providing Crypto inactivation
• Forms TTHMs and HAAs Aurora may not be able to
  meet Stage 2 of D/DBPR
• Requires construction of post-filter disinfection
  contact basin
• Relatively no benefit for TO control
• Pre-chlorination can not be practiced. Loss of
  pre-oxidant will degrade performance of
  filtration process.

5
Disinfectant Evaluation - Chlorine Dioxide

• Advantages
• Lowest capital cost (0 to 250,000) Minimal
  investment nothing lost if ozone is implemented
  later.
• No construction of new contact basin (capital
  cost savings of 3,000,000)
• Does not form bromate
• Chlorite can be controlled to lt 1 mg/L (for 1-log
  Giardia disinfection goal).
• Does not form TTHMs and HAAs. would meet
  anticipated Stage 2 D/DBPR regs

• Disadvantages
• Requires change in technology/operations
• Will probably require that the existing contact
  basin be covered to mitigate UV degradation.
  (400,000)
• Requires handling of sodium chlorite, and higher
  attention to safety.
• Chlorite control might be required. Higher
  dosages (for possible future Cryptosporidium
  inactivation requirement) would produce chlorite
  concentrations above 1 mg/L.

6
Disinfectant Evaluation - Chlorine Dioxide
(contd)

• Advantages
• Can provide 0.5-log inactivation of
  Cryptosporidium
• Strong oxidant will help control Quincy TO
  problems, and could eliminate KMNO4 and PAC
  system.
• Will reduce manganese concentrations though
  oxidation/filtration
• Application to raw water will provide benefit to
  filtration performance (pre-oxidation)

• Disadvantages
• Could be more costly (operations) than ozone for
  Cryptosproidium inactivation.
• Some negative experience with taste and odor.
  Mainly with inefficient systems, that used free
  chlorine for residual disinfectant. Chlorine
  oxidized chlorite and formed ClO2 in the
  distribution system. (Not a problem if
  chloramine is used).

7
Master Plan Evaluation of Disinfectant Costs
8
Initial Demand and Decay Rate Determines ClO2
Dosage CT
1
Area Under Curve Represents CT Achieved
0.9
Initial Demand
0.8
0.7
(mg/L)
0.6
0.5
2
0.4
ClO
ClO
Concentration Decay
0.3
2
0.2
0.1
0
0
5
10
15
Time (min)
9
Existing Contact Flocculation Basin Can Be
Optimized for t10
10
Chlorine dioxide contactor modifications
11
Why Isnt ClO2 More Common?

• Until recently, minimal regulatory incentive to
  increase disinfection
• Poor efficiency and performance of older style
  generators
• Toxicology gaps for ClO2- and ClO3-
• mclg for CLO2- was increased from 0.08 to 0.8
  mg/L
• No mclg for CLO3-

12
Aurora Conclusions

• ClO2 can meet current disinfection requirements
  without construction of chlorine contact basin
  (saves 2.8 million)
• ClO2 provides some taste and odor control

13
Conclusions (contd)

• ClO2 can meet current disinfection requirements
  without chlorite control
• Implementation of ClO2 preserves capital and
  provides time to
• Evaluate alternatives
• Allow regulations to solidify

14
Casper Wyoming

• 52 mgd plant with conventional treatment for 27
  mgd and 25 mgd wells
• Inadequate disinfection and DBPs approaching
  Stage I

15
Driving Factors for Caspers Disinfection
Evaluation

• GWDUI
• Apply Disinfectant to Ground Water Surface
  Water
• Discontinue Chlorination
• Cost Estimates

16
Existing SurfaceWater Treatment System
FromNorthPlatteRiver
Chlorine
Alum
Storage
TransferPumping
Floc/Sed
Filters
Raw Water Pumping
Screens
HighServicePumping
WashwaterLagoons
Sludge Lagoons
To Distribution System
17
Upgraded Surface Water Treatment Process
FromNorthPlatteRiver
SO4 FeCl3
NaOCl NH4Ortho-PO4
Ozone
HighServicePumping
Actiflo Clarification
OzoneContactor
Filters
Raw Water Pumping
Settled Water Pumping
Screens
To Distribution System
Sludge Lagoons
WashwaterLagoons
18
Level of Disinfection
19
Surface Water Ozone Demand
20
Surface Water Ozone Decay
21
Ozone Contactor Alternatives

• High-Pressure In-Line Contacting
• Low-Pressure In-Line Contacting
• Conventional Over-Under Baffled Contactor

22
Recommended Low-Pressure In-Line Ozone Contactor
23
Casper Conclusions

• Ozone will provide up to 2 log Cryptosporidium
  inactivation
• THMs and HAAs will be reduced to below 10 ug/L
• Bromate is not an issue
• Inline ozone was the least cost alternative

24
Henderson NevadaUV Disinfection

• Direct filtration plant
• Chlorine disinfection for 1 log Giardia and 2 log
  virus inactivation

DBP and Disinfection Drivers

• Need to achieve 2 log Crypto inactivation
• Future need for chloramines for THM and HAA
  control

25
Disinfection Objectives

• Provide Cost-Effective Disinfection
• No Less Than 2-Log Cryptosporidium Inactivation
• No Less Than 2-Log Giardia Inactivation
• Provide Capability to Eliminate Use of Free
  Chlorine for Primary Disinfection

26
Disinfection Alternatives Evaluated

• Ozone
• Ultraviolet Disinfection
• Chlorine Dioxide
• Membranes

27
Disinfectant Comparison

• Ozone
• Strong oxidant ()
• Powerful disinfectant ()
• Microflocculation ()
• Controls taste and odor ()
• Increases concentration of D.O. (-)
• High cost (-)
• Disinfection mechanism not completely defined (-)
• Bromate formation (-)
• Increases concentration of AOC (-)
• Operationally complex (-)

• UV
• No byproduct formation ()
• Effective protozoan and viral disinfectant ()
• Generated onsite (does not require LOX delivery)
  ()
• Lower cost ()
• Disinfection mechanism not completely defined (-)
• Lamp cleaning/replacement (-)
• No measure of disinfectant residual (-)

28
Calculation of UV Ozone Disinfection Performance

• Ozone
• Relies on measurement of residual and hydraulic
  modeling to calculate CT
• Contactor design validated with tracer testing
  (t10)
• Monitoring disinfectant provides continuous
  measure of disinfection efficiency

• UV
• UV intensity sensors, flow signal, lamp age, UV
  transmittance and power measurement to calculate
  dose (I x t), and assess possible problems
• EPA expected to publish IT values in near future
  (2-3 years)

29
Why Hasnt UV Been More Prevalent for Potable
Water Treatment?
30
Previous Studies Used In Vitro Assays for
Protozoan Inactivation

• Cell Excystation (Viability Assay Using In Vitro
  Measure of Ability of Oocyst to Excystate Open
  Up Under Simulated Gut Environment)
• Vital Dyes (in Vitro Assay Using Fluorogenic
  Vital Dyes That Adhere to Viable Oocysts or
  Non-viable Depending on Dye)
• Study Showed UV Dose of 120 mJ/cm2 for
  2-log Cryptosporidium Inactivation (Ransome
  et al, 1993)

31
Infectivity Tests Provide New Understanding of
Protozoa Inactivation By UV

• Infectivity Assays Using Neonatal Mice (In Vivo)
• In Vitro Assays Unable to Correctly Predict
  Infectivity
• Infectivity Accurately Tests the Ability to Cause
  Disease Not Just Viability

32
Recent Research Indicates Capability of UV for
Cryptosporidium Inactivation
0
Excystation
-1
Infectivity
-2
After Clancy et al., 1998 Demonstration Scale
Testing Medium-Pressure UV Lamp
Log (N/No)
-3
-4
-5
0
50
100
150
200
UV Dose, mW-sec/cm2
33
Recent UV Inactivation Data for Cryptosporidium

• Clancy 2.8 to 4.8 Log Crypto Inactivation Using
  25 mJ/cm2
• Bolton 3-Log Crypto Inactivation at 20 mJ/cm2
• Finch 2.5 to 4.6 Log Crypto Inactivation Using
  28 mJ/cm2
• Sobsey Linden 4-Log Crypto Inactivation Using
  15 mJ/cm2

34
Giardia Inactivation Capability of UV

• Previous Studies (Hoff, Karanis) Showed Doses of
  100 to 180 mJ/cm2 Required for 2.0-Log Giardia
  Inactivation
• Sobsey Linden 4-log Giardia Inactivation Using
  15mJ/cm2
• Bolton 3-log Giardia Inactivation at 20 mJ/cm2

35
UV Regulatory Status in the U.S.

• Widely Used Since 1980s in WW Treatment and
  Reclamation (CA Title 22 Approval)
• SWTR Included UV Doses for 2 and 3 Log Virus
  Inactivation in 1989/1990
• EPA Proposes Groundwater Rule With UV As a Likely
  BAT in 1991
• 1998 - New Cryptosporidium Research Released
• 1999 - EPA Sponsors UV Workshop for FACA

36
Hendersons UV Implementation Strategy

• Bench-Scale Testing
• Conduct bench-scale collimated beam testing to
  establish dose-response relationship for MS-2
  and/or Bacillus subtilis for Hendersons water
• Design and Construction
• Evaluate/select the UV system vendor based on an
  evaluated bid
• Detailed design of UV system including controls
  and monitoring
• Installation
• Full-scale performance validation

37
Hendersons UV Implementation Strategy (contd)

• Validation
• Full-scale demonstration using MS2 phage/Bacillus
  spores
• Back-calculate full-scale system dosage
• Maintenance
• Routine cleaning/replacement of UV lamps
• Routine cleaning/calibration/replacement of UV
  sensors

38
Henderson NV Conclusion

• UV achieved disinfection and DBP goals
• Lowest cost option
• Regulatory approval can coincide with design and
  construction

39
Denver WaterChlorine Disinfection

• Conventional water treatment at 3 water treatment
  plants
• Disinfection with chlorine followed by chloramines

DBP and Disinfection Drivers

• Need to reduce THMs and HAAs
• Planning for future disinfection and DBP
  regulations

40
Current Disinfection Practice
Chlorine
Raw Water
Headworks
Rapid Mix
Flocculation/ Sedimentation
Ammonia
Chlorine
Filter
Clear Water Reservoirs
41
Project Goals

• Continue to meet current EPA disinfection
  requirements
• Improve safety / reliability
• Identify strategies for future compliance
• Develop implementation plan and costs

42
Disinfection Regulations

• Current 30 minutes contact
• SWTR 0.5-log Giardia inactivation
• ESWTR 0 to 3-log (0 to 99.9)
  Cryptosporidium inactivation

43
Disinfection Objectives

• Short Term
• - 0.5-log Giardia Inactivation
• - TTHMs lt 80 ppb, HAAs lt 60 ppb
• - Eliminate prechlorination
• Long Term
• - Cryptosporidium inactivation
• - Lower levels of DBPs

44
Short Term Planning
45
Long-Term Planning
Meets DBPR
Chlorine
Chlorine
Yes
Conduct Ozone / UV Studies
No
Crypto Inactivation
ImplementChlorination Strategy
Yes
Evaluate Performance of Chlorine Chloramine
gt 1.0 Log Crypto?
No
Ozone or UV
Yes
No
Meets Criteria
No
Chlorine Chloramine
Yes
Chlorine Chloramine
46
Long Term Disinfectants Costs (0.5-Log
Cryptosporidium)
47
Short-Term Implementation Elements

• Construct well-baffled chlorine contact basins
• Install emergency gas scrubbers
• Update chlorination equipment and controls
• Provide process monitoring and control for
  disinfection

48
Computational Fluid Dynamic Model T 25 min.
49
Implementation Schedule
1997 1998 1999 2000 2001 2002 2003
Design/Construct Chlorination System
Improvements Pilot Testing - Ozone Pilot Testing
- Chlorine/Chloramine ESWTR Requirements
Identified Design/Construct Long-Term
Disinfection Improvements
50
Denver Water Conclusions

• Post Filtration chlorine will meet disinfection
  and DBP requirements
• Study ozone and UV
• Wait for regulatory development
• Initiate revised disinfection based on regulatory
  requirements and study results

51
DBP Compliance Now and Into the Future

• Each case is site specific when balancing
  disinfection needs and DBP
• Chlorine, ozone, chlorine dioxide, and UV are all
  possibilities
• A thorough analysis and cost estimate is
  essential to a good decision