1. Distribution System Optimization for Water Quality By Brian T. Bisson, P.E. This paper is based on a collaborative effort of the Ohio EPA and the Technology Committee and Distribution Committee of the Ohio Section of AWWA.

2. Paper Outline  Technology Committee Synopsis  Water Quality Monitoring  Biofilm Control and Assessment  Distribution System Piping and Storage  Flushing Programs  Hydraulics and Water Quality Monitoring

3. Technology Committee  Committee Make-up  Guidance Documents and White Papers  Committee’s work has informed and saved capital funds for water utilities (AWWAJ Article)  Ohio EPA and Water Utility Industry working together – Practical approach for all factions “Special purpose” samples collected for the purpose of distribution system optimization are not required to be reported.

4. Water Quality Monitoring  Baseline Monitoring Program Planning (goals, resources, end user) Design (parameters, frequency, equipment, sites) Implementation (fix quality issues as they are confirmed to be problems) Data collection (grab and on-line)  Common parameters: pH, chlorine residual, HPC, DBPs, pressure, temp, taste and odor, and also ammonia, nitrite, and nitrate for chloraminated systems

5. Water Quality Monitoring, continued Baseline Monitoring  Monitoring ParameterIndication  Disinfectant residualDecrease = main break, biofilm, cross-connection, etc Increase = chlorinator problems, change in valving  Turbiditymain break, cross connection, fire flow, flushing, flow reversal, O & M, security breach, post precip, pump trip  pH, Conductivity, AlkCorrosion control issues, cross connections, treatment issues, breach, new cement mortar lining  VOCspresence = probable cross connections  Trace MetalsCorrosion control problems, cross connection  TOCIncrease = biofilm sloughing off, cross connection Decrease = biofilm consumption, DBP formation  Water SourceConductivity, other parameters: DBPs, chlorine, fluoride, chloride, nitrate, sulfate, sodium, potassium, hardness, magnesium, and calcium

6. Water Quality Monitoring, continued Baseline Monitoring, continued  Monitoring ParameterIndication  Tracer StudiesFluoride can be used as an aid in determining water age  Leak investigationsChlorine, fluoride, hardness, alkalinity, pH, conductivity, DBPs can all be used to determine if a leak is drinking water of from groundwater intrusion.

7. Biofilm Control and Assessment  Definition: A diverse association of microorganisms and their byproducts existing together. Biofilms are typically very sparse. Typically, the levels and composition of biofilms are not known until the biofilm begins causing problems.

8. Biofilm Control and Assessment  Biofilm Problems The type of organisms in a biofilm are usually not a health concern, Not all biofilm organisms benign. Unclear the extent that pathogens can grow in biofilms, but clear that biofilms can shelter these organisms. Biofilm growth can produce taste and odor, e.g. fungi and musty t & o, iron reducing bacteria can release sulfur compounds, and decay of dead biomass. Biomass can produce acid and promote the formation of tubercules.

9. Biofilm Control and Assessment  Factors that influence the growth Seed – Good disinfection helps prevent introduction Food – High TOC has been shown to support growth Disinfectant – maintaining residual key Type of disinfectant – Chloramines Vs. free chlorine Hydraulics – Low flow tends to favor Temperature – High temp favors development/diversity Pipe condition and material – Corroded pipes favor

10. Biofilm Control and Assessment  Biofilm control Decrease nutrients: enhanced coagulation, activated carbon, source water protection Nitrogen may be the limiting factor. For systems using chloramines careful control of ammonia is important. Suggest a goal of < 0.1 mg/L leaving the plant. Corrosion control: Iron has chlorine demand. Adequate disinfectant concentration: Couple with corrosion control and flushing program. Chloramines more sustainable. Flushing: Remove debris and bring fresh water. Only temporary

11. Storage Facilities  In general poor mixing and turnover increases water age, reduces disinfection residual, increases microbial counts, increases DBPs, and nitrification (in chloraminated systems)  Volume turnover: OEPA recommends 25%/day  Using water quality data to evaluate tank mixing: residuals, DBPs, bacteria counts, temperature data

12.  Examples of poorly mixed tanks: Temperature Free Chlorine TTHM HAA5 Tank No.TopBottomTopBottomTopBottomTopBottom 180790.82.075544220 278780.21.878583541 381780.01.974561244 481800.01.766692551 581780.01.974502247

13. Storage Facilities  Inlet Momentum

14. Storage Facilities  Inlet Location

15. Storage Facilities  Poorly Mixed Tank

16. Storage Facilities  Well-Mixed Tank

17. Storage Facilities  Other Tank Mixing Comments Computational Fluid Modeling (CFD)  Qualitative visual image (AWWARF CFD package) Avoid Baffling  Increased water age, less residual, greater DBPs Excess Storage  Historically built for hydraulics  Oversized or hydraulically submerged  Distribution system analysis to ensure storage needs met

18. Distribution Piping  Pipe looping: dead zones; cul-de-sacs  Managing valves  Blow-offs  Photo courtesy of Hydro-Guard International.

19. Distribution Piping Pipe Material  Cast Iron  Ductile Iron (cement mortar-lined) Potential Water Quality Impacts  May exert higher disinfection demand  Loss of disinfection residual  Increased DBP’s from higher chlorine dose to overcome higher demand  Color (red water)  Taste and odor  Increased microbial activity  Nitrification for chloraminated systems  Lack of quality control may lead to increased metals concentration, e.g. barium, cadmium, chromium, or aluminum

20. Distribution Piping Pipe Material  Asbestos-Cement  Prestressed Concrete Cylinder  Lead  Copper  Galvanized  Plastic (HDPE) Potential Water Quality Impacts  Inc asbestos, barium, cadmium, chromium, or Aluminum  Leaching of calcium in non-stable waters  Lack of quality control may lead to increased metals  Increased tap lead under certain conditions  Increased tap copper under certain conditions  Microbial-influenced corrosion under certain conditions  Pitting corrosion may result in home plumbing failures  Increased zinc, iron, lead, copper, cadmium, and others  Possible leaching of VOC’s from surrounding soils

21. Distribution Piping  System Expansion Alternatives Smaller Planning Horizons – Build-out Vs. 5 to 10 yrs Dual storage tanks Smaller mains – Capital and O & M impacts

22. Flushing Program  Objectives: To remove impurities: Accumulated, new and repaired mains, complaints, hazardous To reduce: bacteria concentrations, chemical contamination, To increase chlorine residual To eliminate taste and odors To remove discolored water To reduce turbidity To remove accumulated sediment To respond to customer complaints To maintain the life of the mains

23. Flushing Program  Data Collection and Monitoring Complaint code Pressure in surrounding mains >20 psi Records of color, clarity, turbidity, DO, pH, and temp Chlorine residual at start, middle, and end of flushing Visual clarity and time to clear Lab results for samples collected Location and time of maintenance work

24. Flushing Program  Flushing Process Flushing plan: from source toward periphery Flush one short section at a time to maintain > 20 psi Consider flushing at night Flushing velocities: Min of 2.5 fps; Goal for 8-inch and smaller mains of 5 to 7 fps Do not try to flush large dia mains supplied by a small dia main Notify all customers (hospitals and laundries)

25. Flushing Program  Unidirectional Flushing Proper Planning - AWWARF Report: “Development of Distribution System Water Quality Optimization Plans” Identify Target area (within one pressure zone) Gather Data (water source, infrastructure, critical customers) Program layout: single clean water source; 4 fps; do not extend past: change in pipe size, large unclosed branch, intersection connecting unflushed segments; delineate and sequence additional segments

26. Hydraulics  Hydraulic “Surges” or “Water Hammer” or “Transients” Use of high speed pressure monitors to identify transients Disrupt pipe scales, biofilms, and sediments leading to taste and odor, color, or other customer complaints Negative pressures can create backflow Eliminating water hammer: pump soft starts, VFD’s, controlled closing of valves, pres-reducing valves, air- release valves, and other system controls

27. Water Quality Modeling  EPANET: http://www.epa.gov/nrmrl/wswrd/dw/epanet.html http://www.epa.gov/nrmrl/wswrd/dw/epanet.html  Modeling Basics:

28. Water Quality Modeling  Types of models Skeletonized Vs. All Pipe  Skeletonized: transmission and some distribution mains  Skeletonized for master planning and fire flow testing Steady-state Vs. Extended Period Simulation (EPS)  EPS essential for water quality analysis Hydraulic Vs. Water Quality  Need a calibrated hydraulic model for an accurate water quality model

29. Water Quality Modeling  Model Applications Master Planning – quantity and quality Regulations – Residuals and DBPs: predictions of non- conservative parameters requires extensive model calibration and validation Security – sensor location, contaminant tracing, contaminant containment Customer complaints – flushing plans

30. Conclusions  Distribution system impacts water quality  Distribution system regulations increasing  Evaluate impacts and make physical or operational improvements to minimize degradation. Get to know your system Baseline data to determine if conditions are unusual Be proactive – don’t wait for an “event” to investigate water quality issues.

31. Questions ?