Lecture 5: Sedimentation and Flocculation

COEFFICIENTS VERSUS NRe 1 Laminar III Turbulent II Transition 105 104 SPHERES DISKS 103 CD CYLINDERS 102 10 1.0 0.1 10-4 10-3 10-2 10-1 1 10 NRe 102 103 104 105 106 Figure by MIT OCW. Adapted from: Reynolds, T. D., and P. A. Richards. Unit Operations and Processes in Environmental Engineering. 2nd ed. Boston, MA: PWS Publishing Company, 1996. SETTLING ZONE V INLET v V vo H OUTLET ZONE ZONE e SLUDGE ZONE Zones of a rectangular, horizontal, continuous-flow sedimentation basin. 2V 1/2 H 2V v vo Reduced tank depth does not increase removal ratio. V 1/2 H V v 1/2 v0 Intermediate Tray 1/2 H Tray in tank provides added floor area & increases solids removal Figure by MIT OCW. Adapted from: Camp, T. R. "Studies of Sedimentation Basin Design." Sewage and Industrial Wastes 25, no. 1 (1953): 1-12. EFFECT OF PARTICLE AGGLOMERATION ON SETTLING Settling Zone A H B Figure by MIT OCW. Adapted from: Camp, T. R. "Studies of Sedimentation Basin Design." Sewage and Industrial Wastes 25, no. 1 (1953): 1-12. EFFECT OF TURBULENT DIFFUSION ON SETTLING Figure by MIT OCW. Adapted from: Camp, T. R. "Studies of Sedimentation Basin Design." Sewage and Industrial Wastes 25, no. 1 (1953): 1-12. Apparatus For Quiescent Settling Analyses Siphon 1 h2 Cock Constant Temperature water bath h5 3 Sample of Suspension 2 Portion for concentration test 4 Sample of suspension 5 Sludge Figure by MIT OCW. Adapted from Camp, T. R., 1946. Sedimentation and the design of settling tanks. Transactions ASCE. Vol. 111, Pg. 895-936. R1 �h1 Sampling Ports h1 �h2 Isopercent Removal Curves �h3 DEPTH h2 40% 50% 60% 70% 80% h3 �h4 R5 R4 h4 R2 R3 0.5 m 150 mm h5 t1 t2 t3 t4 t5 TIME Figure by MIT OCW. Adapted from: G. Tchobanoglous, F. L. Burton, and H. D. Stensel. Wastewater Engineering: Treatment and Reuse. 4th ed. Metcalf & Eddy Inc., New York, NY: McGraw-Hill, 2003, p. 369. Figure by MIT OCW. Adapted from: MWH, J. C. Crittenden, R. R. Trussell, D. W. Hand, K. J. Howe, and G. Tchobanoglous. Water Treatment: Principles and Design. 2nd ed. Hoboken, NJ: John Wiley & Sons, 2005, p. 781. RECTANGULAR SETTLING TANK Sludge hoppers Influent Sludge Drawoff Drive motor Skimmer Chains Scraper board Scum Scum A Effluent troughs Effluent Scum box Plan Drive Skimmer WS Influent Effluent Sprockets Chains Scraper board Sludge Drawoff Sludge hoppers B Longitudinal Section Figure by MIT OCW. Adapted from: Reynolds, T. D., and P. A. Richards. Unit Operations and Processes in Environmental Engineering. 2nd ed. Boston, MA: PWS Publishing Company, 1996, p. 249. ISBN: 0534948847. Flocculator Clarifier Corner blade Baffle Walk way Influent channel Blades Effluent pipe Weir Rake arm Cage Blade Influent pipe Sludge pocket Drive Unit Chain Effluent channel Guide plate Flash mixer Chamber Counter weight Paddle Sheaves Corner blade Stuffing box Sprocket Chain Dry well Gear motor PLAN Handrail Diffuser Water level Concrete pier Turntable Cage Top of tank Rake arm Flow Baffle Sludge discharge pipe Flocculator & square sedimentation tank for water clarification, illustrating ceoss-flowoperation. Figure by MIT OCW. Adapted from: Droste, R. L. Theory and Practice of Water and Wastewater Treatment. Hoboken, NJ: John Wiley & Sons, 1997. Influent pipe Effluent Flume Collection Trough Bridg e Scraper Arm Rotation Flocculation Skirt Mixer Water level Collection trough with submerged orifaces Effluent flume Flocculation zone Settling zone Settling zone Inlet port Flocculator-clarifier provides mixing, flocculation, & sedimentation in a compartmented concentric circular tank. Figure by MIT OCW. Adapted from: Droste, R. L. Theory and Practice of Water and Wastewater Treatment. Hoboken, NJ: John Wiley & Sons, 1997. Figure by MIT OCW. Adapted from: Droste, R. L. Theory and Practice of Water and Wastewater Treatment. Hoboken, NJ: John Wiley & Sons, 1997. Figure by MIT OCW. Adapted from: Binnie, C., M. Kimber, and G. Smethurst. Basic Water Treatment. 3rd ed. Cambridge, UK: Royal Society of Chemistry, 2002.