Water and Wastewater Treatment - Exam 1 Answer Key | ENV 4514C, Exams of Engineering

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Exam #1 ENV 4514C Fall 2009 J I Name: __/ ‘NS wer a Formulas: t=Vv/Q Q=VoA 1 m3 = 264 gal 1 ft? = 7.48 gal P=G2uV Q=VbA 1N= 1kg*m/s? 1gal=3.8L 1lb=454g 1W=N‘*m/s 1. Chemical addition in a 15-MGD water treatment plant will be performed in two parallel mixing basins with mechanical mixers. The mixing intensity as measured by the root mean velocity gradient should be a minimum of 850 s"', and the mean residence time should be 5 s at the design flow. Find the volume of the tanks and the power required for the mixers. The dynamic viscosity is 1.139x10-3 kg/m-s. Assume the mechanical mixer is 85% efficient. ' nee) I dey LAG. oy e Fe | - £ lo wr S35 = i 4 y Q ¢ Is 4, ain Ta 3 . 3 v= &5 g] in > 27% miu 2m @ 164m pr besin 2L4 J# é IL, te at eis BP» (6s04)- tare? Wy, bee» VIS «ph - Wash 2) $4 bh ger bam Oby 2, Four rectangular clarifiers in parallel, each 200 ft. long and 40 ft. wide with a water depth of 12 ft, are used to settle a total flow of 20 MGD after a flocculation process. Calculate the overflow rate, detention time, and horizontal velocity. Also determine the length of effluent weir required to meet a specification of 20,000 gpd/ft. & Mo per basin 8 §- Jo! # s V, vee Ie Sig 2) As gel 2oo - uo a so ey Gee. ane eke. 2.46 4 @ Sh ey, pb iy — Vn = & . 5:0 Sy tee og ag HH 7 7, = 0,403 a WL fe -nyd Tp! Jonenin Jn pee an ee 2 eH a 7 vty lela Zi. aw Sr'/]t ——