Experimental Methods
Here the experimental methods consist of 4 stages programmed in the Process Controller.
In the "Raw Water Turbidity" stage, a concentrated kaolin clay suspension was added to aerated tap water (we used the university-supplied tap water for all experiments) to produce a raw water source for treatment. The raw water turbidity was continuously sampled by means of a turbiditymeter coupled with a feed-back control loop. The raw water turbidity values were 100 NTU with a coefficient of variation of ±5%.
In the "Floc Blanket formation" stage, the raw water turbidity is combined with the alum solution - dosage of 45 mg/L (4.23 mg/L Al) was utilized. Here we used the flow rate of 712.6 mL/min throughout all experiments. The solution of raw water and alum were rapidly mixed by flowing through a tube 4.8 mm ID (inner diameter), 1 m in length with an energy dissipation rate of 0.1 W/kg.
To mimick the conditions in water treatment plants, we used the tubular flocculator to facilitate particle aggregation. The flocculator had a length of 26 m, a coil diameter of 13.5 cm, an inner diameter of 0.95 cm. This resulted in a head loss of 0.159 m and a hydraulic residence time of 156 sec. In the laboratory, we had the Reynolds number of 1590 - well in the laminar flow regime.
