A35 mgd surface water treatement plant proposes to to use alum coagulation for turbidity reduction using 44 mg/ l alum. the raw water has an alkalinity of 80 mg / l as caco3. commercial alum has the formula al2(so4)3 x 18h2o (mw= 666).

a) determine the daily alum dosage required in kg/ day?

b) using the equivalent concept , how much alkalinity is used up by the alum added?

c) is the water alkalinity adequate. i. e , is it grater than the alkalinity consumed by alum?

answer : (a) volume of the gas = 8.67 ×   l

                (b) second virial coefficient b = -1.21226 l/mole

solution :   given,     t = 300k

                                p = 20atm

                                z = 0.86

                                n = 8.2 mmoles = 8.2 × moles

                                r =   0.082 l atm/k/mol

        find,     (a) volume of gas   and (b) second virial coefficient b at 300k.

formula used :            

                          and            

(a)            

                    = \times 0.082\times 300}{20}[/tex]

                    = 8.67 ×   l

(b)      

                    = (0.00867-1) × 8.659

                    = - 8.5839 l/mole