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Water Supply Reservoirs Pre-settling Reservoirs: Required where there are wide & rapid variations in raw wate

SUSTAINABLE SANDHILLS WATER RESOURCES CONFERENCE -2007 DRINKING WATER DISTRIBUTION / TREATMENT Siraj Chohan, P.E. DENR-DEH Public Water Supply Section November 8, 2007.

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Water Supply Reservoirs Pre-settling Reservoirs: Required where there are wide & rapid variations in raw wate

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  1. SUSTAINABLE SANDHILLSWATER RESOURCES CONFERENCE -2007DRINKING WATER DISTRIBUTION / TREATMENTSiraj Chohan, P.E. DENR-DEH Public Water Supply SectionNovember 8, 2007

  2. Water Supply ReservoirsPre-settling Reservoirs: Required where there are wide & rapid variations in raw water quality • Impoundments: Sufficient to meet designed water supply demand during periods of drought

  3. Water Supply Reservoirs • Existing Impoundments: • May be approved as raw water sources. An extensive study is required including: • Plans & specs of the impounding structure • Sources of pollution • Water quality fluctuations & sediments • Other information, environmental documentations & regulatory requirements.

  4. Water Pipe for Potable Water Systems • AWWA Standards, Section “C”, or • NSF Standards No. 14 & No 15, or • Approved Equal Standards • Large Diameter Steel Pipe or PCCP Public Water Supply Section

  5. Water System Pressure Sources Booster Pump to an Elevated Tank Hydropneumatic System Advantages 1. Avoids water hammer shock and infiltration of non-potable substances 2. Less Pressure Spikes 3. Least Fatigue Failure in pipe fittings 4. No total & immediate loss of pressure in power outage 5. Avoids frequent pump cycling (shut down & restart) 6. Reliable (water storage) 7. Less operating cost (continuous-run feature) 8. Can provide fire protection 9. Less maintenance frequency 10. Minor leakage does not fail the system 11. Provides a cushion to exert & absorb pressure Public Water Supply Section

  6. Water System Pressure Sources Variable Demand Pressure Pump Disadvantages • Water hammer shock and infiltration of non-potable substances • Pressure Spikes • Fatigue Failure in pipe fittings • Total & immediate loss of pressure in power outage • Frequent pump cycling (shut down & restart) • Least reliable (no water storage) • High operating cost (continuous-run feature) • High maintenance frequency • Minor leakage fails the system • Doesn’t provide a cushion to exert and adsorb pressure and cannot provide fire protection Public Water Supply Section

  7. Basics of Fire Protection Water Supply • ANY LOCATION WITHIN A WATER DISTRIBUTION SYTEM THAT IS PROPOSED FOR A FIRE HYDRANT MUST BE CAPABLE OF DELIVERING A MIINIMUM OF 500 GPM FOR 60 MINUTES, OR 250 GPM FOR 120 MINUTES, WHILE MAINTAINING 20 PSI MINIMUM PRESSURE ANYWHERE IN THE SYSTEM DURING THE PERIOD OF THESE FIRE FLOW RATES. • A fire hydrant is considered to be any normally recognized device consisting of one ~4.5” opening port (steamer nozzle) and two ~2.5” opening ports (hose nozzles).

  8. Basics of Fire Protection Water Supply 2. No locking collars or other devices are allowed to secure the steamer nozzle, nor are these hydrant assemblies to be installed (for future use) with the lateral valve closed to render the hydrant out of service.

  9. Basics of Fire Protection Water Supply • All systems are required to maintain at least 30 psi throughout the distribution system during normal flows, with the allowance that systems designed & rated for fire protection must maintain at least 20 psi throughout during the period of peak demand resulting from fire flow. • 4. Fire hydrants shall not be installed on water mains of less than six inch diameter.

  10. Water Treatment Chlorination, pH adjustment and others • When and Why Public Water Supply Section

  11. Why we treat well water • Water is the universal solvent • Carries • Dissolved minerals • Biological life forms • Water borne bacteria • Protected by • Well site requirements • Well construction requirements • Chemical & physical treatment • Routine testing & sampling

  12. Chlorination • Potable water must be free of disease causing microorganisms • 18C. .0402(j) • Continuous disinfection (chlorination) post January 1, 1972 or Bacteriological problems pre 1972 • Chlorine residual of greater than 0.2 mg/l readily kills bacteria

  13. Chlorination • Why? • Total Coliform • Fecal Coliform • Other disease causing microorganisms

  14. Influencing factors • Concentration of chlorine • Time of chlorine contact • Degree of mixing • Chlorine demand

  15. Other Chlorination • Disinfection of wells • minimum chlorine residual of 100 mg/l (or ppm) in the entire water column for 24 hours. • Disinfection of storage tanks and distribution • 50 mg/l or (ppm) for 24 hours • Disinfection of filters • 50 mg/l for 24 hours

  16. Treatment MethodOxidation / Chemical • Define: A chemical reaction that changes the makeup of the contaminant • Purpose: To change the physical characteristic of the contaminant so that it is potable or more treatable • Method: • Chlorine • Potassium Permanganate (KMnO4; more effective than chlorine: faster, not pH dependent) • Ozone; Chlorine Dioxide

  17. Treatment MethodFiltration • Define: To strain or trap particles in a specially designed media or membrane. • Purpose: To remove the contaminant and render the water potable. Backwashing, regenerating and rewashing a filter may be needed to clean / restore the media for continue use. • Method: • Gravity (sand); Pretreatment may be required. • Pressure Filter; Greensand, birm, and other man made media; specially designed depending on needs. • Membrane / Fiber; Reverse Osmosis (RO) • Notes: Control valves, wastewater concerns, filtration rate, routine water quality checks, pressure drops

  18. Treatment MethodFiltration • Method: Pressure Filter; Greensand, carbon and other man made media; specially designed depending on needs

  19. Treatment MethodFiltration • Method: Membrane / Fiber; Reverse Osmosis (RO)

  20. Why should this matter? • The water provider is responsible for the water quality and quantity to the user’s tap. The design, operation and maintenance of the system treatment facility is an important part in providing a safe and reliable drinking water supply.

  21. pH Adjustment • Why - to buffer the water and provide corrosion control • Water quality in North Carolina • low pH • soft • aggressive • Lead and Copper Rule • Systems which exceeded action level for lead or copper must perform corrosion control study and implement corrosion control

  22. Type of Contaminant Degree of Risk Quality Desired Type Treatment Required Level of Operation Interfering Agents Cost

  23. Significant Current Issue When the Rivers Run Dry Conservation

  24. Unprecedented Period of Dry Weather • Resulted in extremely low levels for many rivers, lakes and reservoirs • Has also affected groundwater levels • Surficial aquifers, especially

  25. Within the Water Distribution System • Un-accounted for water loss should be less than 10%, as determined through records review and on-site evaluation • Increase scrutiny for un-accounted for water • Identify and repair waterline leaks promptly • Remind customers that leaks are expensive

  26. Where to find further information

  27. PWS Regional Offices

  28. PWSS Website

  29. CONTACT INFORMATIONPublic Water Supply Sectionhttp://ncdrinkingwater.state.nc.us/ - or - http://www.deh.enr.state.nc.us/pws/index.htm

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