The Effect of Inlet Tube Size on a Cone Shaped Flocculater Shubha Bhar Taylor Britton

Purpose and Goals Purpose: To study the effects of influent tube size on the growth and stability of the sludge blanket in a cone flocculator. Goals: Build up sludge blanket Take turbidity values above blanket Conduct Dimensional Analysis Determine ideal tube size

Velocity, Momentum, & Shear  Velocity: too slow and the flocs settle, too fast and they all wash out  Momentum: causes the interface between the sludge blanket and the overlying water to be unstable  Shear: Breaks up floc

Hypothesis We expected that the largest tube size will be most effective in producing the most stable sludge blanket for a given flow rate. Expected points of failure: velocity = 0.2 m/s shear = 0.1 Pa

Set Up

Flow Rates and Dosage Dose Rate and Concentrations Alum Dose50mg/L Clay100NTU Flow 1: Alum Concentration12.5g/L Clay Concentration12.2g/L Flow 2: Alum Concentration25g/L Clay Concentration24.4g/L Flow Rates Sludge Blanket Pump20mL/min Flow 1: Water Flow100mL/min Alum Pump0.46mL/min Clay Pump1.65mL/min Flow 2: Water Flow200mL/min Alum Pump0.46mL/min Clay Pump1.65mL/min

Trials: Q = 100 mL/min  Trial 1: Pipe diameter = cm (0.25 inch) Q = 100 mL/min  Trial 2: Pipe diameter = cm (3/8 inch) Q = 100 mL/min No sludge blanket formed!

Trials: Q = 200 mL/min  Trial 3: Pipe diameter = cm (3/8 inch) Sludge Blanket: 27 cm  Trial 4: Pipe diameter = cm (0.25 inch) Sludge Blanket failure  Trial 5: Pipe diameter = cm (3/8 inch) Sludge Blanket: 15 cm  Trial 6: Trial 4: Pipe diameter = cm (0.25 inch) Sludge Blanket failure

Turbidity Measurements: Trial 4 Q = 200 mL/min, sludge blanket height = 27 cm, pipe diameter = cm

Turbidity: Trial 5 Q = 200 mL/min, sludge blanket height = 15 cm, pipe diameter = cm

Velocity Calculations Inner Tube Diameter (cm)Q (mL/min) Velocity out of pipe (m/s) Velocity in Tank (m/s) Mass balance used to determine velocity out of pipe and upward velocity in tank through the sludge blanket.

Shear Shear Values Q (mL/min)Pipe DiameterShear (Pa)

Froude Number  Sludge Blanket Density = g/mL  Fr = 0.33 Froude number proportional to (inertial force) / (gravitational force) Froude number is generally used to characterize flow, Fr numbers of less than 1 equal tranquil flow Fr numbers = 1 indicate critical flow Fr numbers greater than 1 indicate rapid flow.

Reynolds Number Flow is non turbulent! Q = 200 mL/min Pipe Diameter = cm Re = 56.6 Pipe Diameter = cm Re = 40

Conclusions  Our flow rates may have been too low  Success may have been influenced by alum spikes  Building sludge blankets can be unpredictable!