CIVE 450 Problems Page 4, Spring 2014

(Weateutat the initial head loss t ayer of uniform anthracite wit! uniform sand with a porosity of both med shape factor for the s hrough a dual media filter consisting of a 0.4-m “Ite V h a grain diameter of 1.2 mm and a 0.30 m layer of grain diameter of 0.60 mm at a filtration rate 2.9 L/m?.sec.the ia is 0.42, the shape factor for the anthracite is 7.5 and the and is 6.0. Assume the water temperature is 10°C. ese the backwash velocity of water at 20°C the will expand the bed and maximum abrasion with sand with an effective size of 0.6 mm, a uniformity coefficient of 1.4 and a specific gravity of 2.65. What would be the backwash velocity at 15 °C. A filter unit has a surface area of 4.88 m wide and 9.144 m long. After filtering 10,900 m3 for 50 hours, the filter is backwashed at a rate of 0.65 m/min for 15 min. Find (a) the average filtration rate, (b) the quantity of washwater, (c) percent of washwater to treated water, and (d) the flow rate to each of the four troughs. . A filter plant is to be constructed to process 75,700 m°/d. Pilot-plant analysis on mixed media indicated that a maximum filtration rate of 15 m/h will be acceptable. Assuming a surface configuration of approximately 5 x 8 m, how many filter units will be required? Allow one unit out of service for backwashing. The backwash velocity required to expand the filter is 36 m/h. Each backwash period requires 30 min during which the back wash flow is for 10 min, and the water is wasted for the first 10 min of each filter run. Determine the net uction of each filter if it is backwashed once per day. sults of a chlorine demand test on aw water at 20°C are given in the table. ple Chlorine Dosage Residual Chlorine (mg/L) (mg/L) \ =\¢ x 0.20 0.18 0.40 0.33 0.60 0.40 0.80 0.25 igs 1.00 0.43 \O 400 1.20 0.62 ; 1.40 0.82 1.60 1.02 d curve ie dosage