Problem 3. Rework Problem 1 above (using an MLVSS concentration of 3,000 mg/L), but for a PFR with a recycle ratio = 0.50. Also use the same Q == 12,960 m³/d, So = 84 mg BOD5/L, same S corresponding to the effluent standard of 30 mg BOD5/L and 30 mg/L suspended solids (with BOD5 of effluent solids = 63% of suspended solids concentration), Ks = 100 mg BOD5/L, ka = 0.05 d¨¹, μm= 2.5 d¹, Y 0.5 mg VSS/mg BOD5. = µm=

Refer to Problem 2.C.1. Results of the sieve analysis for Soils A, B, and C are given below. To obtain a more representative sample for further geotechnical testing, a ternary blend is created by uniformly mixing 8000 kg of each soil. Answer the following questions. a. If a sieve analysis is conducted on the mixture using the same set of sieves as shown above, compute the mass retained (as a percentage) and cumulative percent passing in each sieve. b. What would be the uniformity coefficient (Cu) and the coefficient of gradation (Cc) of the mixture?

Repeat Problem 2.14 with the following values: Gs = 2.75, temperature of water = 21C, t = 88 min, and L = 11.7 cm. 2.14 A hydrometer test has the following result: Gs = 2.65, temperature of water = 26 C, and L = 10.4 cm at 45 minutes after the start of sedimentation (see Figure 2.25). What is the diameter D of the smallest-size particles that have settled beyond the zone of measurement at that time (that is, t = 45 min)? Figure 2.25 ASTM 152H type of hydrometer placed inside the sedimentation cylinder (Courtesy of Khaled Sobhan, Florida Atlantic University, Boca Raton, Florida)