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Wastewater Management

Wastewater Management. Obj 6.3: Sewage Generation. Water Supply Usage. for most municipalities the amount of sewage will be about 60-75% of the water supply used. demand for fresh water peaks around 6:00 pm this is typically when PEAK SEWAGE FLOW RATE occurs. Peak Sewage Flow Rate.

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Wastewater Management

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  1. Wastewater Management Obj 6.3: Sewage Generation

  2. Water Supply Usage • for most municipalities the amount of sewage will be about 60-75% of the water supply used. • demand for fresh water peaks around 6:00 pm • this is typically when PEAK SEWAGE FLOW RATEoccurs.

  3. Peak Sewage Flow Rate Is the total flow from all generators of sewage and includes: domestic commercial institutional infiltration

  4. Domestic Sewage Qdomestic = A x PD x SGR x PF A = residential area (ha) PD = population density (persons/ha) SGR = sewage generation rate (m3/person/day) PF = peaking factor

  5. Peaking Factor

  6. Peaking Factor If sewage flow monitored from a subdivision was measured at 8,640,000 L for a 24 hour period and the measured flow rate at the time of peak usage was 0.22 m3/s: Average flow rate = Peaking Factor =

  7. Peaking Factors (PF) • small towns have higher peaking of water use (high peaking factor) 200% to 500% of average flow rate • large towns have lower peaking of water use (low peaking factor) 150% to 250% of average flow rate

  8. Commercial and Institutional Sewage • wide variety of land use types and densities • great variation in sewage generation • Domestic Equivalent Estimation Method • Sewage Generation Rate Method

  9. Commercial & Institutional Sewage Qcom/inst= AC x SGR x PF AC = area characteristic SGR = sewage generation rate (m3/characteristic/day) PF = peaking factor

  10. Infiltration • groundwater seeps into sanitary sewers through cracks and joints • surface runoff finds its way into manholes • infiltration amounts depend on quality of construction and age of system

  11. defective joints cracked pipes water table level manhole integrity construction and inspection maintenance and repair Factors that affect infiltration rates Infiltration

  12. Infiltration Flow Rates Qinfiltration = A x IF A = surface area (ha) IF = infiltration rate (m3/ha/day)

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