Disinfectant & Disinfection Byproducts Control and Optimization Case Study of the University of...

Disinfectant & Disinfectant & Disinfection Byproducts Disinfection Byproducts Control and Control and OptimizationOptimization

Case Study of the University Case Study of the University of Alaska Fairbanks Water of Alaska Fairbanks Water SystemSystem

By Johnny Mendez, P.E., Drinking Water ProgramAlaska 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.

November 12, 2007November 12, 2007 22

Disinfectant vs. DBP Disinfectant vs. DBP balancebalance Optimized disinfection at WTP and Optimized disinfection at WTP and

Distribution System improves barrier against Distribution System improves barrier against microbial pathogensmicrobial pathogens

BUT….BUT….

(Cl or O3)+ Organics (Cl or O3)+ Organics DBPs (TTHM, HAA5, DBPs (TTHM, HAA5, Bromate)Bromate)

The challenge is to balance these competing The challenge is to balance these competing goalsgoals


DBP Health effectsDBP Health effects

Suspected CarcinogensSuspected Carcinogens Suspected to affect reproductionSuspected to affect reproduction Large population exposure to Large population exposure to

DBPsDBPs Other potential DBPs health Other potential DBPs health

effects have not been fully effects have not been fully researchedresearched


Optimization goals for Optimization goals for Disinfection & DBP Disinfection & DBP ControlControl Methodology developed from CPE Methodology developed from CPE

concepts used at media filtration WTPs.concepts used at media filtration WTPs.– Optimization goalsOptimization goals– Use of special studies (scientific method)Use of special studies (scientific method)

Process Applications Inc. and EPA effort.Process Applications Inc. and EPA effort. Basis for Optimization Goals:Basis for Optimization Goals:

– Public health protectionPublic health protection– Safety factor for achieving complianceSafety factor for achieving compliance– Provide means to measure improvementsProvide means to measure improvements


D/DBP Optimization D/DBP Optimization GoalsGoals TOC Performance Goals:TOC Performance Goals:

– (% TOC removed/% removal required)=1.1 (10% safety factor)(% TOC removed/% removal required)=1.1 (10% safety factor)– Finished water TOC concentration= goal WTP specificFinished water TOC concentration= goal WTP specific

Disinfection Goals:Disinfection Goals:– Maintain sufficient inactivation CT (safety factor is system Maintain sufficient inactivation CT (safety factor is system

specific)specific)– Maintain minimum distribution system residual:Maintain minimum distribution system residual:

Free Chlorine ≥ 0.2 mg/lFree Chlorine ≥ 0.2 mg/l Total Chlorine = system specific (suggest >0.5 mg/L)Total Chlorine = system specific (suggest >0.5 mg/L)

DPB Goals:DPB Goals:– Individual site LRAA: TTHM≤ 80 ppb; HAA5 ≤ 60 ppbIndividual site LRAA: TTHM≤ 80 ppb; HAA5 ≤ 60 ppb– Long Term System Goal (based on 11 quarter average of Max Long Term System Goal (based on 11 quarter average of Max

LRAAs): TTHM≤ 60 ppb; HAA5 ≤ 40 ppbLRAAs): TTHM≤ 60 ppb; HAA5 ≤ 40 ppb


D/DBP Optimization D/DBP Optimization ToolsTools Historical Cl2 and CT SpreadsheetHistorical Cl2 and CT Spreadsheet

– WTP Cl dose, Cl residual, and CT assessmentWTP Cl dose, Cl residual, and CT assessment

Historical Chlorine Residual Performance SpreadsheetHistorical Chlorine Residual Performance Spreadsheet– assess historical Cl residual trends for WTP effluent assess historical Cl residual trends for WTP effluent

and distribution systemand distribution system

Historical TOC performance SpreadsheetHistorical TOC performance Spreadsheet– assess WTP TOC removal performanceassess WTP TOC removal performance

Historical DBP PerformanceHistorical DBP Performance– Assessment of historical DBP performance vs. new Assessment of historical DBP performance vs. new

optimization goalsoptimization goals


Develop a WQ Baseline Develop a WQ Baseline and Monitoring Planand Monitoring Plan Before changes in the water system are Before changes in the water system are

implemented a water quality baseline is needed implemented a water quality baseline is needed to:to:– Understand historical system performance in Understand historical system performance in

light of optimization goalslight of optimization goals– Help fine tune/set optimization goalsHelp fine tune/set optimization goals– Have a basis of comparison for measuring Have a basis of comparison for measuring

improvements in DPB controlimprovements in DPB control– Anticipate and prepare for potential secondary Anticipate and prepare for potential secondary

impactsimpacts A monitoring plan will help in the systematic and A monitoring plan will help in the systematic and

efficient collection of data for the baseline.efficient collection of data for the baseline.


Developing a BaselineDeveloping a Baseline

Select which relevant WQ parameters to Select which relevant WQ parameters to monitor (i.e. TOC, Alkalinity, CT, TTHM).monitor (i.e. TOC, Alkalinity, CT, TTHM).

Some parameters may already be Some parameters may already be available, but frequency may need to be available, but frequency may need to be modified.modified.

Consider use of surrogate parameters Consider use of surrogate parameters for ease of data collection & cost for ease of data collection & cost savings (e.g. TOC and DBP surrogates)savings (e.g. TOC and DBP surrogates)


Surrogates for DBP Surrogates for DBP related datarelated data Developing a DBP control strategy Developing a DBP control strategy

may require increased TOC and may require increased TOC and DBP data. This can increase cost DBP data. This can increase cost and complexity of data collectionand complexity of data collection

Tools exist to enhance TOC and Tools exist to enhance TOC and DBP data quantity by using DBP data quantity by using alternative field methods that are alternative field methods that are faster and less costlyfaster and less costly


Field TOC MethodsField TOC Methods

UV absorbance at 254 nm:UV absorbance at 254 nm:– Uses spectrophotometer Uses spectrophotometer – Samples need to be filteredSamples need to be filtered– Requires development of relationship b/w UVRequires development of relationship b/w UV254254 and TOC and TOC– Best for water samples before Cl additionBest for water samples before Cl addition

Field TOC method (HACHField TOC method (HACH®®): ): – Uses reagents and spectrophotometerUses reagents and spectrophotometer– Issues with accuracy & precisionIssues with accuracy & precision

Portable TOC analyzer (GE): Portable TOC analyzer (GE): – costly equipment (~ $15K)costly equipment (~ $15K)– Easy to use and calibrateEasy to use and calibrate


TOC and UVTOC and UV254254 RelationshipRelationship

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

TO

C

(mg/L

)

UV Absorbance at 254 nm (1/cm)

0.00

0.05

0.10

0.15

R2=0.89

Y=34X+0.98


Field DBP MethodsField DBP Methods

Cl residual DecayCl residual Decay

– Simple, can be done by Simple, can be done by

all WTP operatorsall WTP operators

– Cl residual is used as Cl residual is used as

surrogate for DBP surrogate for DBP

formationformation

– Relationship may Relationship may

change through the change through the

year due to WQ and year due to WQ and

temp. changestemp. changes

Relationship Between Free Chlorine and TTHM

y = -52.119x + 110.15R2 = 0.9368

0

20

40

60

80

100

120

140

0 0.5 1 1.5 2 2.5

Free Chlorine Residual (ppb)

TT

HM

(p

pb

)


Field DBP Methods Field DBP Methods (cont.)(cont.) THM Plus™ ( HACHTHM Plus™ ( HACH®®))

– Uses spectrophotometer and 4 reagentsUses spectrophotometer and 4 reagents– Measures 4 THM species plus other trihalogenated DBPs:Measures 4 THM species plus other trihalogenated DBPs:

ChloroformChloroform BromodichloromethaneBromodichloromethane DibromochloromethaneDibromochloromethane BromoformBromoform Trichloroacetic acid, plus other HAAs, & Chloral Hydrate.Trichloroacetic acid, plus other HAAs, & Chloral Hydrate.

– Results can be obtained in 1-2 hrs.Results can be obtained in 1-2 hrs.– Paired sampling needed to develop relationship b/w field Paired sampling needed to develop relationship b/w field

and analytical values.and analytical values.– Cost ~$5 to $10 per sample once equipment purchasedCost ~$5 to $10 per sample once equipment purchased– Spectrophotometer cost ~$3000 (DR2800) to $6000 Spectrophotometer cost ~$3000 (DR2800) to $6000

(DR5000)(DR5000)


THM-Plus MethodTHM-Plus Method

Relationship Between THM-Plus and TTHM

y = 0.8864x - 1.1765

R2 = 0.8481

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

THM-Plus (ppb as CHCl3)

TT

HM

(p

pb

)• 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)

• 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


Creating a Monitoring Creating a Monitoring PlanPlan

Develop objective for the Develop objective for the monitoringmonitoring

Answer sampling specifics (what, Answer sampling specifics (what, where, how, who, frequency)where, how, who, frequency)

Suggested min. monitoring:Suggested min. monitoring:– TOC & DBPs (including surrogates)-> monthlyTOC & DBPs (including surrogates)-> monthly– Disinfectant residuals at WTP->DailyDisinfectant residuals at WTP->Daily– Disinfectant Residuals in Distribution->WeeklyDisinfectant Residuals in Distribution->Weekly


What Next: What Next: what to do what to do With All this Data?With All this Data?

Create Graphs to see trendsCreate Graphs to see trends Make list of issues/sites to focus Make list of issues/sites to focus

onon Develop relationships with Develop relationships with

surrogate parameters to help in surrogate parameters to help in process controlprocess control

Develop DBP control strategies for Develop DBP control strategies for testingtesting


Developing a DBP Developing a DBP Control StrategyControl Strategy Operations-based change that will Operations-based change that will

lower DBPslower DBPs Use “Special Studies” approachUse “Special Studies” approach

– Hypothesis, Methods/Resources, Experimental Design, Hypothesis, Methods/Resources, Experimental Design, Results/Conclusions, implementationResults/Conclusions, implementation

Take small stepsTake small steps Pay attention to secondary impactsPay attention to secondary impacts Develop implementation strategyDevelop implementation strategy

– Use data to sell idea to managementUse data to sell idea to management– Think of scale (Seasonal/Year-round?, Think of scale (Seasonal/Year-round?,

WTP/Distribution?)WTP/Distribution?)


DBP Control DBP Control Strategies--Examples:Strategies--Examples: Lowering TOCLowering TOC Optimize Chlorine Use (pre-chlorination, Optimize Chlorine Use (pre-chlorination,

intermediate, & post chlorination)intermediate, & post chlorination) Optimize Process pHOptimize Process pH

– Higher pH (>8.5) higher TTHM formation Higher pH (>8.5) higher TTHM formation PotentialPotential

– Lower pH (<6.5) higher HAA formation Lower pH (<6.5) higher HAA formation potentialpotential

Reduce water ageReduce water age

University of Alaska University of Alaska Fairbanks (UAF)Fairbanks (UAF)

Case StudyCase Study


UAF Public Water System Aerial View


UAF Water System UAF Water System FactsFacts Population: 3600 Non-Transient, 1400 ResidentPopulation: 3600 Non-Transient, 1400 Resident 2600 acre campus (230 acres developed)2600 acre campus (230 acres developed) Design Capacity= 1 MGD; Typically runs < 0.5 MGD Design Capacity= 1 MGD; Typically runs < 0.5 MGD (350 (350

gpm)gpm)

Source: Ground water wells (3 wells)Source: Ground water wells (3 wells)– High IronHigh Iron 15 mg/l 15 mg/l– High MnHigh Mn 1.5 mg/l 1.5 mg/l– High TOCHigh TOC~13 mg/l~13 mg/l

Treatment:Treatment:– Objective: Fe & Mn & Organics removal (Benzene)Objective: Fe & Mn & Organics removal (Benzene)– Pre-Oxidation (Permanganate) Pre-Oxidation (Permanganate) – High Rate Aeration, High Rate Aeration, – Coagulation: Nalco 7768 Anionic Polymer & 8185 PAC polymer, Coagulation: Nalco 7768 Anionic Polymer & 8185 PAC polymer, – Flocculation: 2-Stages, 20 min to 2 hrs detention timeFlocculation: 2-Stages, 20 min to 2 hrs detention time

-- Arsenic45ppb

-- pH 7 to 8

-- Alkalinity~310-350 mg/L


UAF Water System UAF Water System Facts (cont.)Facts (cont.) Treatment (cont.):Treatment (cont.):

– Sedimentation: 30Sedimentation: 3000 Tube Settlers, (settled water turbidity ~1.0- Tube Settlers, (settled water turbidity ~1.0-3.0NTU)3.0NTU)

– multi-media filtration: Anthracite, Sand, Gravel (turbidity ~.05-.07 multi-media filtration: Anthracite, Sand, Gravel (turbidity ~.05-.07 NTU)NTU)

– GAC (10 filters, run 5 at time)GAC (10 filters, run 5 at time)– Corrosion inhibitor (zinc sulfate),Corrosion inhibitor (zinc sulfate),– Storage (1.5 MGal),Storage (1.5 MGal),– Chlorination (MIOX Sal-80): Target entry point Cl residual ~1.5 Chlorination (MIOX Sal-80): Target entry point Cl residual ~1.5

ppm. ppm.

Distribution: Distribution: – ~ 6-miles of pipe~ 6-miles of pipe– Parallel fire protection and domestic water mainsParallel fire protection and domestic water mains– Mainly 8” and 10” diameter DI PipesMainly 8” and 10” diameter DI Pipes– Water pipes in utilidor shared by steam linesWater pipes in utilidor shared by steam lines– ~100 service connections~100 service connections– Highest Water Temp ~72Highest Water Temp ~72ooFF


UAF


Bunnell

IARC

Ag-Farm

Museum

Eielson

Physical Plant

WTP

Nat. Science

Wood Center

Duckering

Commons

Library

O’ Neill

Arctic Health

Gruening Brooks

Power Plant

Student Housing

Elvey

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.


UAF DBP Study UAF DBP Study StrategyStrategy Cl dataCl data TOC dataTOC data Develop Cl Map in DistributionDevelop Cl Map in Distribution Collect CL residualCollect CL residual Collect THM Plus dataCollect THM Plus data Collect TTHM data and HAA5Collect TTHM data and HAA5


Historical dataHistorical data

TOCTOC CLCL DBPDBP


Latest DevelopmentsLatest Developments

THM-Plus dataTHM-Plus data


What Next?What Next?

Select Stage 2 sitesSelect Stage 2 sites IDSEIDSE Treatment changes:Treatment changes: Coagulation enhancementCoagulation enhancement Carbon Filter Special Study?Carbon Filter Special Study? Membrane system?Membrane system?


SourcesSources

ADEC D/DBP Training February 26, 2007. Larry DeMers, ADEC D/DBP Training February 26, 2007. Larry DeMers, Process Applications Inc., Ft. Collins, CO.Process Applications Inc., Ft. Collins, CO.

UAF Water Distribution Condition Survey. PDC, Inc. UAF Water Distribution Condition Survey. PDC, Inc. Consulting Engineers; Project 2001110CWS, Final Report. Consulting Engineers; Project 2001110CWS, Final Report. November 2001.November 2001.

ADEC SDWIS DatabaseADEC SDWIS Database


Questions?Questions?

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