A short cut procedure for the design and monitoring of continuous flow sedimentation or thickening tanks

A Short cut graphical procedure has been developed analogous to stepwise for the design of continuous flow sedimentation or thickening tanks.In this technique, several computer programs have been set up in order to reduce the data input, necessary for performing all intermediate calculations by computer. The data describing the settling of particles and movement of the particle-liquid interface as a function of time and operating conditions are the only data required. The method predicts the time required to attain the prescribed underflow concentration, the rate of hindered settling subsidence, the area required for clarification, the thickener area and dimensions. The proposed method has been applied to illustrate the effect of different chemical treatment doses on a typical industrial effluent from the manufacture of starch and byproducts from American yellow corn.List of Symbols A1 cm First falling zone line intercept - A2 cm Settling zone curve intercept - A3 cm Compression zone line intercept - A4 cm Angle bisector intercept - A5 cm Tangent interception at the compression point - ACL m² Minimum clarification area - ALPHA() Angle between line 1 and line 2, radians - ATH m² Minimum thickening area - ATH1 m² Area of each individual tank - B1 cm · min^–1 First falling zone line slope - B2 Settling zone curve power - B3 cm · min^–1 Compression zone line slope - B4 cm · min^–1 Angle bisector slope - B5 cm · min^–1 Tangent slope at the compression point - BT m Approximate width of the tank - BT1 m Actual width of the tank - CC Conversion criteria - CO mg/dm³ Initial solid concentration - CU mg/dm³ Underflow solid concentration - D m Basin depth - DIAM m Diameter of circular tank - DMIN m Minimum allowable liquid depth - DT h Minimum allowable detention time - DT1 h Calculated detention time - HT cm Subsiding particle-liquid interface height - HT1 min Subsiding particle-liquid interface coordinate for line 1 and line 2 intersection - HTR cm Subsiding particle-liquid interface coordinate for compression point - L m Approximate length of the tank - L1 m Actual length of the tank - LMAX m Maximum allowable tank length - LMIN m Minimum allowable tank length - NI Number of iterations - NO Number of tanks - PI Const. - Q m³/h Wastewater flowrate - SL m³/(m² · d) Surface loading - T1 Tan() - T3 Tan (/2) - TM min Time of measuring subsiding particle-liquid interface - TM1 min Time coordinate for line 1 and line 2 intersection - TML min Lower limit of the root - TMR min Time coordinate for compression point - TMU min Upper limit of the root - TU min Time required to attain underflow concentration - ZO cm Initial height of sludge - ZU cm Settled height of sludge interface - FI m Inert depth (typically taken as 1 m)