List of practice Questions

Fecal Coliform (FC) concentration in river water was measured as 10708 cfu/100 ml. The FC concentration after the conventional water treatment, but before chlorination, was measured as 23 cfu/100 ml. The 'Log Kill' (inactivation) of FC due to the conventional water treatment is closest to:

MgCl$_2$ and CaSO$_4$ salts are added to 1 litre of distilled deionized water and mixed until completely dissolved. Total Dissolved Solids (TDS) concentration is 500 mg/l, and Total Hardness (TH) is 400 mg/l (as CaCO$_3$). The amounts of MgCl$_2$ and CaSO$_4$ added are calculated (rounded off to the nearest integer). Which of the following options is/are true: