Question

QUESTION 5 5.1 Determine the 4-day BOD and the Ultimate BOD (1st stage) for a wastewater whose BODs at 20 °C is 250 mg/l. The reaction constant is k=0.23d" (base e). Determine the BODs if the test had been done at 25 °C. (10) 5.2. The chlorination unit in a WWTP uses 10 containers of chlorine on a monthly basis. A chlorine dosage is 4 mg/l is used to treat an average monthly wastewater effluent of 500 000 mDetermine the mass of one chlorine container. (10)

Answer 1

at 20°C At temperature 20°C 5 days BOD at 20°C , BOD5 = 250mgle. Reaction constant, K=0.23/day (base e) BODO = BODu [2 - ekt] → 250 = BODY [ 1-2 - 0-2345 ] BODu = - 250 [1-40-23X5) ] => BODA = 365.8377 mgle Ultimate BOD where, BODS → 5 days BOD at 20°C BODu - Ultimate BOD K-deoxyination constant at base e. (at 20°C) t Number of days. 4- Day BOD at 20°C, BODu = BODu (1-e kt) - 365-8377 (1– e-C0-23 *4)) BODudy = 220.04 mgle . 4 days BOD at 20°C

At temperature 25°C Kroc = Kroc [1.047] T6 - 2006 Kzse = 0.23 [1047] 25-20 = 0·2894 day 5 day BOD at asoc, BODG = BODU [ 1- e-kt] where, BODO → 5days BOD at 25°C BODU > Ultimate BOD K- deoxygination constante at base e (at 25°c) t Number of days. BODE = 365-8377 [ 7-e-0-2894 x5 ] = 2:13-1552 mg | = 279 BOD5 = 279-7652 mg/L 5 days Bod at 25°C.