A primary clarifier is to be designed to treat a municipal wastewater. The influen to the clarifier has a flow rate of 7570 m³/d and a total suspended solids concentration of 320 mg/L. A laboratory settling test was performed with the following results: Suspended Solids Concentration (mg/L) at Given Depths Sampling Depth (m) 1.83 262 Time (min) 3.05 282 253 230 0.61 1.22 246 2.44 272 10 230 20 157 195 230 243 30 115 160 211 221 45 90 48 134 163 179 154 195 60 102 131 86 170 90 29 58 115 141 (a) Determine the design overflow rate and detention time assuming 65% of the suspended solids are to be removed. Use typical scaling/safety factors as appropriate. (b) Determine the required diameter (to the nearest 0.1 m) and the required depth (to the nearest 0.01 m) for the clarifier.

In a constant head permeability test, if the discharge coming out of the sample is 0.35 cm³/s find the coefficient of permeability if the length and area of cross section of the sample is 30 cm and 250 cm² respectively. The head loss per unit length of the sample can be assumed as 0.25.

Darcy concept.

Q1) The data in the table below used to design a sedimentation tank with depth=4m and detention time=2hr, the influent flow is 2000L for each minute. 0.004 0.01 0.02 0.03 0.04 0.05 0.063 0.085 0.12 Settling Velocity(cm/sec) Weight fraction 98 95 Greater than size % 8 6 4 3 2 1 0.5 Determine the overall removal efficiency for this tank, s.g. of particle=1.2 u=0.89x10-³N.s/m². Use Ax=0.1. Q2) For the above question find the depth of sludge for each day if the influent solid concentration is 3000mg/L and percentage of solid=8% and sludge density =1.2 ton/m³.