Disinfectant

1
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, 2007. 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

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

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

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 gt0.5
  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

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

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.

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)

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

10
Field TOC Methods

• UV absorbance at 254 nm
• 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

11
TOC and UV254 Relationship
7.0
6.0
5.0
R20.89
4.0
TOC (mg/L)
3.0
Y34X0.98
2.0
1.0
0.0
0.00
0.05
0.10
0.15
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

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)

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 0-600 ppb
• Sensitivity 10 ppb
• Precision 66 ppb (95 confidence range 53
  ppb-79 ppb)

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)-gt monthly
• Disinfectant residuals at WTP-gtDaily
• Disinfectant Residuals in Distribution-gtWeekly

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

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?)

18
DBP Control Strategies--Examples

• Lowering TOC
• Optimize Chlorine Use (pre-chlorination,
  intermediate, post chlorination)
• Optimize Process pH
• Higher pH (gt8.5) higher TTHM formation Potential
• Lower pH (lt6.5) higher HAA formation potential
• Reduce water age

19
University of Alaska Fairbanks (UAF)

• Case Study

20
UAF Public Water System Aerial View
21
UAF Water System Facts

• Population 3600 Non-Transient, 1400 Resident
• 2600 acre campus (230 acres developed)
• Design Capacity 1 MGD Typically runs lt 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?310-350 mg/L
22
UAF Water System Facts (cont.)

• Treatment (cont.)
• Sedimentation 300 Tube Settlers, (settled water
  turbidity 1.0-3.0NTU)
• multi-media filtration Anthracite, Sand, Gravel
  (turbidity .05-.07 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

23
UAF
24
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
Power 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.

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

26
Historical data

• TOC
• CL
• DBP

27
Latest Developments

• THM-Plus data

28
What Next?

• Select Stage 2 sites
• IDSE
• Treatment changes
• Coagulation enhancement
• Carbon Filter Special Study?
• Membrane system?

29
Sources

• ADEC D/DBP Training February 26, 2007. Larry
  DeMers, Process Applications Inc., Ft. Collins,
  CO.
• UAF Water Distribution Condition Survey. PDC,
  Inc. Consulting Engineers Project 2001110CWS,
  Final Report. November 2001.
• ADEC SDWIS Database

30
Questions?