Water quality problems

A rule of thumb suggests that 1 mg/L of alum destroys 0.5 mg/L of alkalinity as CaCO3.

1.Use your knowledge of coagulation chemistry to prove that this is approximately true

2.Using this rule of thumb, would the natural alkalinity of the water shown below be sufficient to add 80 mg/L alum, or would we need to add NaOH to prevent the pH from dropping?

A square rapid-mixing basin, with a depth of water equal to 1.25 times the width is to be designed for a flow of 2.0 million gallons per day. The RMS velocity gradient (G) is to be 790 s-1, the detention time is 40 sec, the operating temperature is 50oF, and the turbine shaft speed (i.e. the impeller rotation speed) is 100 rpm. Calculate:

Sample Solution