1. Disinfectant & Disinfection Byproducts Control and Optimization
D/DBP Control & Optimization--UAF Case Study
November 12, 2007
Disinfectant & Disinfection Byproducts Control and Optimization
Case Study of the University of Alaska Fairbanks Water System
By Johnny Mendez, P.E.,
Drinking Water Program
Alaska Department of Environmental Conservation
Prepared in Cooperation with Ben Stacy, WTP Supervisor,
University of Alaska Fairbanks.
Note: The D/DBP optimization and control concepts being presented here have been adapted from a ADEC training workshop in Fairbanks, AK Feb 26-Mar 1, The workshop was developed by Mr. Larry DeMers, PE of Process Applications Inc.

2. Disinfectant vs. DBP balance
Optimized disinfection at WTP and Distribution System improves barrier against microbial pathogens
BUT….
(Cl or O3)+ Organics  DBPs (TTHM, HAA5, Bromate)
The challenge is to balance these competing goals
November 12, 2007

3. DBP Health effects Suspected Carcinogens
Suspected to affect reproduction
Large population exposure to DBPs
Other potential DBPs health effects have not been fully researched
November 12, 2007

4. Optimization goals for Disinfection & DBP Control
Methodology developed from CPE concepts used at media filtration WTPs.
Optimization goals
Use of special studies (scientific method)
Process Applications Inc. and EPA effort.
Basis for Optimization Goals:
Public health protection
Safety factor for achieving compliance
Provide means to measure improvements
November 12, 2007

5. D/DBP Optimization Goals
TOC Performance Goals:
(% TOC removed/% removal required)=1.1 (10% safety factor)
Finished water TOC concentration= goal WTP specific
Disinfection Goals:
Maintain sufficient inactivation CT (safety factor is system specific)
Maintain minimum distribution system residual:
Free Chlorine ≥ 0.2 mg/l
Total Chlorine = system specific (suggest >0.5 mg/L)
DPB Goals:
Individual site LRAA: TTHM≤ 80 ppb; HAA5 ≤ 60 ppb
Long Term System Goal (based on 11 quarter average of Max LRAAs): TTHM≤ 60 ppb; HAA5 ≤ 40 ppb
November 12, 2007

6. D/DBP Optimization Tools
Historical Cl2 and CT Spreadsheet
WTP Cl dose, Cl residual, and CT assessment
Historical Chlorine Residual Performance Spreadsheet
assess historical Cl residual trends for WTP effluent and distribution system
Historical TOC performance Spreadsheet
assess WTP TOC removal performance
Historical DBP Performance
Assessment of historical DBP performance vs. new optimization goals
November 12, 2007

7. Develop a WQ Baseline and Monitoring Plan
Before changes in the water system are implemented a water quality baseline is needed to:
Understand historical system performance in light of optimization goals
Help fine tune/set optimization goals
Have a basis of comparison for measuring improvements in DPB control
Anticipate and prepare for potential secondary impacts
A monitoring plan will help in the systematic and efficient collection of data for the baseline.
November 12, 2007

8. Developing a Baseline
Select which relevant WQ parameters to monitor (i.e. TOC, Alkalinity, CT, TTHM).
Some parameters may already be available, but frequency may need to be modified.
Consider use of surrogate parameters for ease of data collection & cost savings (e.g. TOC and DBP surrogates)
November 12, 2007

9. Surrogates for DBP related data
Developing a DBP control strategy may require increased TOC and DBP data. This can increase cost and complexity of data collection
Tools exist to enhance TOC and DBP data quantity by using alternative field methods that are faster and less costly
November 12, 2007

10. Field TOC Methods UV absorbance at 254 nm: Field TOC method (HACH®):
Uses spectrophotometer
Samples need to be filtered
Requires development of relationship b/w UV254 and TOC
Best for water samples before Cl addition
Field TOC method (HACH®):
Uses reagents and spectrophotometer
Issues with accuracy & precision
Portable TOC analyzer (GE):
costly equipment (~ $15K)
Easy to use and calibrate
November 12, 2007

11. TOC and UV254 Relationship
7.0
6.0
5.0
R2=0.89
4.0
TOC (mg/L)
3.0
Y=34X+0.98
2.0
1.0
0.0
0.00
0.05
0.10
0.15
November 12, 2007
UV Absorbance at 254 nm (1/cm)

12. Field DBP Methods Cl residual Decay
Simple, can be done by all WTP operators
Cl residual is used as surrogate for DBP formation
Relationship may change through the year due to WQ and temp. changes
November 12, 2007

13. Field DBP Methods (cont.)
THM Plus™ ( HACH®)
Uses spectrophotometer and 4 reagents
Measures 4 THM species plus other trihalogenated DBPs:
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
Trichloroacetic acid, plus other HAAs, & Chloral Hydrate.
Results can be obtained in 1-2 hrs.
Paired sampling needed to develop relationship b/w field and analytical values.
Cost ~$5 to $10 per sample once equipment purchased
Spectrophotometer cost ~$3000 (DR2800) to $6000 (DR5000)
November 12, 2007

14. THM-Plus Method HACH® Method 10132
The method can be run on any Hach DR 5000, DR 2800, DR 4000, DR 3000, DR 2400, DR 2010, or DR 2000 Spectrophotometer
Results Measured at 515 nm
Results reported as ppb chloroform
Range ppb
Sensitivity ~10 ppb
Precision= 66 ppb (95% confidence range= 53 ppb-79 ppb)
November 12, 2007

15. Creating a Monitoring Plan
Develop objective for the monitoring
Answer sampling specifics (what, where, how, who, frequency)
Suggested min. monitoring:
TOC & DBPs (including surrogates)-> monthly
Disinfectant residuals at WTP->Daily
Disinfectant Residuals in Distribution->Weekly
November 12, 2007

16. What Next: what to do With All this Data?
Create Graphs to see trends
Make list of issues/sites to focus on
Develop relationships with surrogate parameters to help in process control
Develop DBP control strategies for testing
November 12, 2007

17. Developing a DBP Control Strategy
Operations-based change that will lower DBPs
Use “Special Studies” approach
Hypothesis, Methods/Resources, Experimental Design, Results/Conclusions, implementation
Take small steps
Pay attention to secondary impacts
Develop implementation strategy
Use data to sell idea to management
Think of scale (Seasonal/Year-round?, WTP/Distribution?)
November 12, 2007

18. DBP Control Strategies--Examples:
Lowering TOC
Optimize Chlorine Use (pre-chlorination, intermediate, & post chlorination)
Optimize Process pH
Higher pH (>8.5) higher TTHM formation Potential
Lower pH (<6.5) higher HAA formation potential
Reduce water age
November 12, 2007

19. University of Alaska Fairbanks (UAF)
Case Study

20. UAF Public Water System Aerial View
November 12, 2007

21. UAF Water System Facts Population: 3600 Non-Transient, 1400 Resident
2600 acre campus (230 acres developed)
Design Capacity= 1 MGD; Typically runs < 0.5 MGD (350 gpm)
Source: Ground water wells (3 wells)
High Iron 15 mg/l
High Mn 1.5 mg/l
High TOC~13 mg/l
Treatment:
Objective: Fe & Mn & Organics removal (Benzene)
Pre-Oxidation (Permanganate)
High Rate Aeration,
Coagulation: Nalco 7768 Anionic Polymer & 8185 PAC polymer,
Flocculation: 2-Stages, 20 min to 2 hrs detention time
-- Arsenic45ppb
-- pH 7 to 8
-- Alkalinity~ mg/L
November 12, 2007

22. UAF Water System Facts (cont.)
Treatment (cont.):
Sedimentation: 300 Tube Settlers, (settled water turbidity ~ NTU)
multi-media filtration: Anthracite, Sand, Gravel (turbidity ~ NTU)
GAC (10 filters, run 5 at time)
Corrosion inhibitor (zinc sulfate),
Storage (1.5 MGal),
Chlorination (MIOX Sal-80): Target entry point Cl residual ~1.5 ppm.
Distribution:
~ 6-miles of pipe
Parallel fire protection and domestic water mains
Mainly 8” and 10” diameter DI Pipes
Water pipes in utilidor shared by steam lines
~100 service connections
Highest Water Temp ~72oF
November 12, 2007

23. UAF
November 12, 2007

24. University of Alaska Fairbanks
O’ Neill
IARC
Elvey
Student Housing
Nat.
Science
Museum
Arctic
Health
Wood
Center
Library
Gruening
Brooks
Ag-Farm
Duckering
Eielson
Bunnell
Commons
University of Alaska Fairbanks
Distribution System
Physical
Plant
Notes:
Not to Scale,
Simplified Diagram; not all service connections or branches shown
Water mains are mostly 8-in. diameter. Some sections are 10-in.
Power Plant
WTP
November 12, 2007

25. UAF DBP Study Strategy Cl data TOC data Develop Cl Map in Distribution
Collect CL residual
Collect THM Plus data
Collect TTHM data and HAA5
November 12, 2007

26. Historical data
TOC CL
DBP
November 12, 2007

27. Latest Developments
THM-Plus data
November 12, 2007

28. What Next? Select Stage 2 sites IDSE Treatment changes:
Coagulation enhancement
Carbon Filter Special Study?
Membrane system?
November 12, 2007

29. Sources
ADEC D/DBP Training February 26, Larry DeMers, Process Applications Inc., Ft. Collins, CO.
UAF Water Distribution Condition Survey. PDC, Inc. Consulting Engineers; Project CWS, Final Report. November 2001.
ADEC SDWIS Database
November 12, 2007

30. Questions?
November 12, 2007