## Problems

12.1 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The optimum pH was determined to be equal to 5.32 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the hydrogen ion activity coefficient. Calculate the hydrogen ion activity coefficient.

12.2 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The hydrogen ion activity corresponding to the optimum pH was calculated to be equal to 4.81(10 ) gmols/L at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient of the aluminum ion. Calculate the activity coefficient of the aluminum ion.

12.3 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The optimum pH was determined to be equal to 5.32 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of Al(OH)2+. Calculate the equilibrium constant of Al(OH)2+.

12.4 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The optimum pH was determined to be equal to 5.32 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient Al(OH)2+. Calculate the activity coefficient of Al(OH)2+.

12.5 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The optimum pH was determined to be equal to 5.32 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of Al7(OH)^+. Calculate the equilibrium constant of Al7(OH)17.

12.6 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using alum. The optimum pH was determined to be equal to 5.32 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient of Al7(OH)17. Calculate the activity coefficient of Al7(OH)17.

12.7 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The optimum pH was determined to be equal to 11.95 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the hydrogen ion activity coefficient. Calculate the hydrogen ion activity coefficient.

12.8 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The hydrogen ion activity corresponding

to the optimum pH was calculated to be equal to 1.11(10 ) gmols/L at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient of the ferrous ion. Calculate the activity coefficient of the ferrous ion.

12.9 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The optimum pH was determined to be equal to 11.95 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of FeOH+. Calculate the equilibrium constant of FeOH+.

12.10 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The optimum pH was determined to be equal to 11.95 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient FeOH+. Calculate the activity coefficient of FeOH+.

12.11 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The optimum pH was determined to be equal to 11.95 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of Fe(OH)—. Calculate the equilibrium constant of Fe(OH)—.

12.12 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The optimum pH was determined to be equal to 11.95 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient Fe(OH)—. Calculate the activity coefficient of Fe(OH)—.

12.13 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric chloride. The optimum pH was determined to be equal to 8.2 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the hydrogen ion activity coefficient. If the activity coefficient of the hydrogen ion can be determined, calculate the activity coefficient of the hydroxyl ion.

12.14 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric sulfate. The hydrogen ion activity corresponding to the optimum pH was calculated to be equal to 6.3(10-9) gmols/L at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient of the ferric ion. Calculate the activity coefficient of the ferric ion.

12.15 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric chloride. The optimum pH was determined to be equal to 8.2 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of FeOH2+. Calculate the equilibrium constant of FeOH2+.

12.16 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric sulfate. The optimum pH was determined to be equal to 8.2 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient FeOH2+. Calculate the activity coefficient of FeOH2+.

12.17 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric sulfate. The optimum pH was determined to be equal to 8.2 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the equilibrium constant of Fe2(OH)^+. Calculate the equilibrium constant of Fe2(OH)2+.

12.18 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using ferric chloride. The optimum pH was determined to be equal to 8.2 at a temperature of 25°C. Assume that all parameters to solve the problem can be obtained from the given conditions except the activity coefficient Fe2(OH)2+. Calculate the activity coefficient of Fe2(OH)2+.

12.19 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using alum. The calcium bicarbonate requirement is 20.2 mg/L as CaCO3. Calculate the optimum alum dose. Make appropriate assumptions.

12.20 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using alum. The calcium bicarbonate requirement is 20.2 mg/L as CaCO3 and the optimum alum dose is 44.86 mg/L. Calculate the fraction of the optimum alum dose neutralized by calcium bicarbonate. Make appropriate assumptions, except the fraction neutralized by calcium bicarbonate.

12.21 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using alum. The calcium bicarbonate requirement is 20.2 mg/L as CaCO3 and the optimum alum dose is 44.86 mg/L. Calculate the cubic meters of water treated. Make appropriate assumptions, except the cubic meters of water treated.

12.22 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using alum. The calcium bicarbonate requirement is 20.2 mg/L as CaCO3 and the optimum alum dose is 44.86 mg/L. Calculate the water of hydration of the alum used. Make appropriate assumptions, except the water of hydration.

12.23 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using alum. If the optimum alum dose as determined by a jar test is 44.86 mg/L, calculate the kilograms of calcium bicarbonate required.

12.24 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The alkalinity requirement is 18 mg/L as CaCO3 and the natural alkalinity of the raw water is 100 mg/L as CaCO. Calculate the optimum dose of the coagulant.

12.25 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The alkalinity requirement is 18 mg/L as CaCO3 and the natural alkalinity of the raw water is 100 mg/L as CaCO. Calculate the cubic meters of water coagulated, if the optimum dose of the coagulant is 50 mg/L.

12.26 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The alkalinity requirement is 18 mg/L as CaCO3 and the natural alkalinity of the raw water is 100 mg/L as CaCO. The optimum dose of the coagulant is 50 mg/L. Calculate the fraction of the coagulant dose neutralized in the presence of calcium bicarbonate.

12.27 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The lime used is 22.4 mg/L at a purity of 90%. Making appropriate assumptions and calculate the optimum coagulant dose.

12.28 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The lime used is 22.4 mg/L at a purity of 90%. The optimum coagulant dose is 50 mg/L. If the fraction of the coagulant dose neutralized by calcium bicarbonate is 0.90, calculate the volume of water treated.

12.29 A raw water containing 140 mg/L of dissolved solids is subjected to coagulation treatment using copperas. The lime used is 22.4 mg/L. The optimum coagulant dose is 50 mg/L. If the fraction of the coagulant dose neutralized by calcium bicarbonate is 0.90 and the volume of water treated is 1 m3, calculate the fractional purity of the lime.

12.30 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The calcium bicarbonate alkalinity required is 30 mg/L as CaCO3. The natural alkalinity of the raw water is 100 mg/L as CaCO3. Calculate the optimum coagulant dose.

12.31 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The calcium bicarbonate alkalinity required is 30 mg/L as CaCO3 and the optimum coagulant dose is 40 mg/L. The natural alkalinity of the raw water is 100 mg/L as CaCO3. Calculate the cubic meters of water treated.

12.32 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The calcium bicarbonate alkalinity required is 30 mg/L as CaCO3 and the optimum coagulant dose is 40 mg/L. Per cubic meter of water treated, calculate the fraction of the coagulant dose neutralized by calcium bicarbonate.

12.33 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The optimum coagulant dose as determined by a jar test is 40 mg/L. The natural alkalinity is 5 mg/L as CaCO3. The fraction of the coagulant dose neutralized by lime of 90% purity is 0.6. Per cubic meter of water coagulated, calculate the kilogram of lime used.

12.34 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The kilogram of lime used is 800 at a percentage purity of 90. The optimum coagulant dose as determined by a jar test is 40 mg/L. The natural alkalinity is 5 mg/L as CaCO3. If the fraction of the coagulant dose neutralized by lime is 0.6, calculate cubic meters of water coagulated.

12.35 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The current acidity and pH are, respectively, 30 mg/L as CaCO3 and 5.9. The amount of pure lime used per cubic meter of water coagulated is 0.016865135 kg. Calculate the value of the pH that the coagulation was adjusted to.

12.36 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4). The current acidity is 30 mg/L as CaCO3. The amount of pure lime used per cubic meter of water coagulated is 0.016865135 kg. The pH of coagulation was adjusted to 8.15. Calculate the value of the current pH of the water.

12.37 A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. The amount of pure lime used per cubic meter of water coagulated is 0.0169 kg. The current pH of the raw water is 5.9 and is adjusted to 8.15. Calculate the current acidity.

12.38 A raw water containing 100 mg/L of suspended solids is subjected to a coagulation treatment using FeCl3. The current acidity and pH are, respectively, 30 mg/L as CaCO3 and 5.9. Calculate the amount of sludge produced if the optimum dose is 40 mg/L of FeCl3.

12.39 A raw water is subjected to a coagulation treatment using FeCl3. The current acidity and pH are, respectively, 30 mg/L as CaCO3 and 5.9. The solids produced amount to 0.132 kg/m of water treated. What was the suspended solids content of the raw water, if the optimum coagulant dose is 40 mg/L?

12.40 A raw water is subjected to a coagulation treatment using FeCl3. The current acidity and pH are, respectively, 30 mg/L as CaCO3 and 5.9. The solids produced is 132 kg and the suspended solids of the water is 100 m/L. Calculate the cubic meters of water treated, if the optimum coagulant dose is 40 mg/L.

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