Question

30 A groundwater supply has the following analysis: calcium = 94 mg/l magnesium = 24 mg/l sodium = 14 mg/l bicarbonate = 317 mg/l sulfate = 67 mg/l chloride = 24 mg/l (a) Calculate the quantities of lime and soda ash for excess-lime softening, and the carbon dioxide reacted for neutralization by two-stage recarbonation. Assume that the practical limits of hardness removal for calcium are 30 mg/l as $CaCO_3$ and for magnesium are 10 mg/l as $CaCO_3$, and that three-quarters of the final alkalinity is converted to bicarbonate. Calcu- late the finished hardness and sketch the bar graphs for the raw and finished waters. (b) Calculate the chemical dosages for split-treatment softening, assuming a permissible magnesium hardness in the finished water of 40 mg/l. Follow the methods of solution in Example 8. Draw the bar graphs, after first-stage lime treatment, of the unreacted combined first-stage effluent and bypassed flow, and the finished water after reaction of soda ash. Cal- culate the finished water hardness.

          30 A groundwater supply has the following analysis:
calcium = 94 mg/l
magnesium = 24 mg/l
sodium = 14 mg/l
bicarbonate = 317 mg/l
sulfate = 67 mg/l
chloride = 24 mg/l
(a) Calculate the quantities of lime and soda ash for excess-lime softening, and the carbon
dioxide reacted for neutralization by two-stage recarbonation. Assume that the practical
limits of hardness removal for calcium are 30 mg/l as $CaCO_3$ and for magnesium are 10 mg/l
as $CaCO_3$, and that three-quarters of the final alkalinity is converted to bicarbonate. Calcu-
late the finished hardness and sketch the bar graphs for the raw and finished waters.
(b) Calculate the chemical dosages for split-treatment softening, assuming a permissible
magnesium hardness in the finished water of 40 mg/l. Follow the methods of solution in
Example 8. Draw the bar graphs, after first-stage lime treatment, of the unreacted combined
first-stage effluent and bypassed flow, and the finished water after reaction of soda ash. Cal-
culate the finished water hardness.

30 A groundwater supply has the following analysis:
calcium = 94 mg/l
magnesium = 24 mg/l
sodium = 14 mg/l
bicarbonate = 317 mg/l
sulfate = 67 mg/l
chloride = 24 mg/l
(a) Calculate the quantities of lime and soda ash for excess-lime softening, and the carbon
dioxide reacted for neutralization by two-stage recarbonation. Assume that the practical
limits of hardness removal for calcium are 30 mg/l as CaCO3 and for magnesium are 10 mg/l
as CaCO3, and that three-quarters of the final alkalinity is converted to bicarbonate. Calcu-
late the finished hardness and sketch the bar graphs for the raw and finished waters.
(b) Calculate the chemical dosages for split-treatment softening, assuming a permissible
magnesium hardness in the finished water of 40 mg/l. Follow the methods of solution in
Example 8. Draw the bar graphs, after first-stage lime treatment, of the unreacted combined
first-stage effluent and bypassed flow, and the finished water after reaction of soda ash. Cal-
culate the finished water hardness.

Added by Alejandro S.

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