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# المحاضرة 4-6

الكلية كلية الهندسة     القسم  الهندسة البيئية     المرحلة 4
أستاذ المادة محمد عبد مسلم عبد الله الطفيلي       04/07/2018 08:50:46

Total fraction removed= (?_(i=1)^n??v_ni/v_c (n_i ) ?)/(?_(i=1)^n?? n_i ?)

Where:
v_n=average velocity of particles in the ith velocity range
n_i=number of particles in the ith velocity range

Also:
fraction removed=(1-X_c )+ ?_0^(X_c)?? v?_(p )/? v?_(c ) dx= (1-X_c )+ 1/? v?_(c ) ?_0^(X_c)?? v?_(p ) dx
Hence:
fraction removed= (1-X_c )+1/? v?_(c ) ???? v?_(p ) ?X?

EXAMPLE
Determine the removal efficiency for a sedimentation basin with a critical overflow velocity of 2 m3/m2.h in treating a wastewater containing particles whose settling velocities are distributed as given in the table below. Plot the particle histogram for the influent and effluent wastewater.

Solution :
1. Create a table for calculating the percentage removal for each particle size. Enter the particle settling velocity ranges in column (1).

Calculate the average particle settling velocity for each velocity range by taking the average of the range limits, and enter the values in column 2. For the first velocity range, the average settling velocity is (0.0 + 0.5)/2 = 0.25 m/h.
Enter the number of influent particles for each velocity range in column 3.
Calculate the removal fraction for each velocity range by dividing the average settling velocity by the critical overflow velocity (2 m/h), and enter the result in column 4.Where the result is greater than 1.0, enter a value of 1.0 , because all of the particles are removed.
Fraction removed= v_ni/v_c = 0.25/2.0=0.125
Determine the number of particles removed by multiplying the number of influent particles by the percent removal (col. 3 x col. 4). Enter the values in column 5.
Calculate the particles remaining by subtracting the particles removal from the number of influent particles (col. 3 – col. 5). Enter the results in column 6.
Compute the removal efficiency by calculating the sum of particles removed and dividing the sum by the total number of particles in the influent.

Total fraction removed= (?_(i=1)^n??v_ni/v_c (n_i ) ?)/(?_(i=1)^n?? n_i ?) x 100

Total fraction removed= (394.75 x ?10?^5)/(500 x? 10?^5 ) x 100= 78.95 %

8. Plot the particle histogram for the influent and effluent wastewater.

المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .