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Disinfectant & Disinfection Byproducts Control and Optimization Case Study of the University of Alaska Fairbanks Water System By Johnny Mendez, P.E., Drinking.

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Presentation on theme: "Disinfectant & Disinfection Byproducts Control and Optimization Case Study of the University of Alaska Fairbanks Water System By Johnny Mendez, P.E., Drinking."— Presentation transcript:

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, The workshop was developed by Mr. Larry DeMers, PE of Process Applications Inc.

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

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

4 November 12, Optimization goals for Disinfection & DBP Control Methodology developed from CPE concepts used at media filtration WTPs. Methodology developed from CPE concepts used at media filtration WTPs. –Optimization goals –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 protection –Safety factor for achieving compliance –Provide means to measure improvements

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

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

7 November 12, Develop a WQ Baseline and Monitoring Plan Before changes in the water system are implemented a water quality baseline is needed to: 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. A monitoring plan will help in the systematic and efficient collection of data for the baseline.

8 November 12, Developing a Baseline Select which relevant WQ parameters to monitor (i.e. TOC, Alkalinity, CT, TTHM). 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. 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) Consider use of surrogate parameters for ease of data collection & cost savings (e.g. TOC and DBP surrogates)

9 November 12, 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 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 Tools exist to enhance TOC and DBP data quantity by using alternative field methods that are faster and less costly

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

11 November 12, TOC and UV 254 Relationship TOC (mg/L) UV Absorbance at 254 nm (1/cm) R 2 =0.89 Y=34X+0.98

12 November 12, Field DBP Methods Cl residual Decay 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 November 12, Field DBP Methods (cont.) THM Plus™ ( HACH ® ) THM Plus™ ( HACH ® ) –Uses spectrophotometer and 4 reagents –Measures 4 THM species plus other trihalogenated DBPs: Chloroform Chloroform Bromodichloromethane Bromodichloromethane Dibromochloromethane Dibromochloromethane Bromoform Bromoform Trichloroacetic acid, plus other HAAs, & Chloral Hydrate. 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 November 12, THM-Plus Method 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) HACH® Method The method can be run on any Hach DR 5000, DR 2800, DR 4000, DR 3000, DR 2400, DR 2010, or DR 2000 Spectrophotometer

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

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

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

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

19 University of Alaska Fairbanks (UAF) Case Study

20 November 12, UAF Public Water System Aerial View

21 November 12, UAF Water System Facts Population: 3600 Non-Transient, 1400 Resident Population: 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 (350 gpm) Design Capacity= 1 MGD; Typically runs < 0.5 MGD (350 gpm) Source: Ground water wells (3 wells) Source: Ground water wells (3 wells) –High Iron  15 mg/l –High Mn  1.5 mg/l –High TOC  ~13 mg/l Treatment: 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

22 November 12, UAF Water System Facts (cont.) Treatment (cont.): Treatment (cont.): –Sedimentation: 30 0 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: 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 ~72 o F

23 November 12, UAF

24 November 12, 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.

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

26 November 12, Historical data TOC TOC CL CL DBP DBP

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

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

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

30 November 12, Questions?


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