...
The complete experimental assembly consists of synthetic raw water (SRW) and coagulant metering system, rapid mix and tube flocculator, and flocculation residual turbidity analyzer (FReTA). (Figure 1) The turbidimeter with a feedback loop is used to measure the influent turbidity and the turbidimeter of FReTA measures the effluent turbidity.
Figure 1 Schematic of the complete experimental assembly. (Updated from Ian Tse's MS thesis, Aug. 2009)3.1
SRW and coagulant metering system
The SRW and coagulant metering system includes a reservoir of clay suspension (10g/L), a reservoir of tap water and three pumps (Figure 3). The clay suspension is added to the tap water periodically by the regulation of a solenoid pinch valve. Both alum stock and raw water (with added clay suspension) are drawn by the pumps to mix together. A portion of raw water is pumped into a turbidimeter for the measurement of influent turbidity and then flows back into the raw water feedstock to maintain a constant volume. A flow accumulator connected to the pump dampens the periodic pulses caused by the pump rollers.
SRW and coagulant metering system
The SRW and coagulant metering system includes a reservoir of clay suspension (10g/L), a reservoir of tap water and three pumps (Figure 2). The clay suspension is added to the tap water periodically by the regulation of a solenoid pinch valve. Both alum stock and raw water (with added clay suspension) are drawn by the pumps to mix together. A portion of raw water is pumped into a turbidimeter for the measurement of influent turbidity and then flows back into the raw water feedstock to maintain a constant volume. A flow accumulator connected to the pump dampens the periodic pulses caused by the pump rollers. 
Figure 2 Synthetic Raw Water (SRW) and coagulant metering system. (Updated from Ian Tse's MS thesis, Aug. 2009)
...
After the flow of the raw water and alum is merged, they enter into a spiral "rapid “rapid mix coil " ” to accelerate their blending. The mixture then flows through the laminar tubular flocculator. The tube flocculator is comprised of three spiral tubing units (3/8" 8” ) wrapped in a figure eight around six parallel support cylinders (two cylinders per unit, see figure 3). The tubes are arranged in a helical coil because the flocs would stay at the bottom in a straight tubing system, restricting the growth of the flocs. A calibrated in-line pH probe is inserted at the beginning of the flocculator tube and provides a readout of the mixed suspension's hydrogen ion activity. A pressure sensor is also connected to the tubing to protect the system. Velocity gradients in the tubular flocculator cause particles to collide and form flocs. For coiled tube flocculators, velocity gradient is a function of the flow rate and the inner diameter of the tube. 
Figure 3 Tube flocculator. (Updated from Ian Tse's MS thesis, Aug. 2009)
...