SANITARY ENGINEERING DEPARTMENT CIVIL ENGINEERING WASTEWATER ENGINEERING

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Wastewater Collection Works(Sewerage system) (Combined sewerage system) .

(Separate system)

(Semi Combined system) .

Primary Studies for Sewerage System . . . .......... . . ( ) () . .

(Qd) for gravity pipes. 600 . (67- 75) % 600. Qave = :Qave) Qmin = (Qmax = (2) Qave Qmax Qave Qmin = Qfull

Qfull (Qfull = A.V) A =D V Qfull (4) V/Vfull ((q/ Qfull (d/D) . Qfull 0.8 1.20 / (5) Qfull Vfull D)) () (slop) .

QfullQfullVfullfullVfullVfullQfull

Example:For population = 50000 persons and Rate of consumption = 160 L / c /dDesign a sewer pipe when dmax /D = 0.67 .------------------------------------------------------------------------------------Qave = 160 * 50 000 = 8000 000 L/d = 0.093 m3 / sec .- Qmax = 2 * 0.093 = 0.186 m3 / sec .- Qmin = 0.4 * Q ave = 0.4 * 0.093 = 0.037 m3 / sec .d max / D= 0.67 from chart Qmax / Qfull = 0.78 & Vmax / vfull= 1.11- Q full = Qmax / o.78 = 0.186 / 0.78 = 0.238 m3/ sec .- S = 0.004D = 480 mm = 500 mmV full = 120 cm / sec . V max = V full *1.11 = 133 cm / sec .For Vmin minimum : - Qmin / Qfull = 0.037 / 0.238 = 0.155 - From chart d min / D = 0.028 and Vmin / Vfull = 0.71 V min = 0.71 * 120 = 85 cm / sec . 45 cm / sec. , ok

( )(Wastewater Pump Station)

Example:For flow rate 18000 m3 /d , design wastewater pump station, consider the dry part = 40% and wet part = 60%.-------------------------------------------------------------------------------------------Qave = 18000 m3 / dQmax = 2 Qave = 36000 m3 / dD.T. = 15 minVol = Q * D.T. = {3600 / (24 * 60)}* 15 = 375 m3. Depth = 4.00 mArea of wet well = Vol / depth = 94 m2 Dry well = 40%Wet well = 60% wet area / Total aerea = 60 / 100Total area = Wet area *100 / 60 = 94 / 0.6 = 157 m2 D = 14.15 m .

Design of rising pipe :Q = 375 / 15 * 60 = 0.417 m3 / secNo . of units = 2 q = Q / 2 = 0.209 m3 / sec .Velocity = 1.1 m / sec .Diameter = 50 m = 20 inch .

: 180 / / 10 25 1500 :- . . . : = 100.000 180 = 18000.000 / = 18000 3 / = 2 18000 = 36000 3 / = 15 = = 36000 ( 15 60 24) = 375

= 4 = 93.75 40 % . 60 % . ()/ = 60 / 100 = ( ) * 100 / 60 = 93.75 0.60 = 156.25 = 14

: 15 . = 375 15 = 25 3 / = 0.417 3 / = 0.417 2 = 0.209 3 / 0.209 3 / = 1.10 / = 49 50 = 20 . ( ) = 0.417 3 / 1.1 / = 70 = 28 .

Maintenance of Sewerage System . .

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