A water-treatment plan processes 24, 500 m^2/d of water with the following ionic

Question

A water-treatment plan processes 24, 500 m^2/d of water with the following ionic concentration in meq/L CO_2 0.5 Ca^2- 4.5 Mg^2+ 3 Na^+ 2 HCO_3^- 3 SO_4^3- 3.5 Cl 3.3 Determine the quantities of chemicals (kilograms per day) required to soften this water to the minimum possible hardness by lime soda ash softening. Draw a bar diagram for the finished water. Calculate the dry mass of the solids in the sludge. Repeat question #1 for calcium only softening. What pH is attained by adding 0.7 meq/L of lime to pure water? What is the resulting pH from the 1.25 meq/L excess lime? (Information available on Blackboard) Calculate the lime dosage needed for softening by selective calcium removal for the following water analysis. What is the finished water hardness? Ca^+2 - 63mg/l CO_3^-2 - 16 mg/l Mg^+2 - 15 mg/l HCO_3^- - 189 mg/l Na^+ - 20 mg/l SO_4^-2 - 80 mg/l K^+ - 10 mg/l Cl - 10 mg/l A water treatment plant is to process 30,000 m^3/d. The rapid mixing tank will blend 35 mg/L of alum with the flow and is to have a detention time of 2 min. The tank is to have a square cross section with vertical baffles and a flat blade impeller. Determine the following: Quantity (kilograms per day) of alum added Dimensions of the tank Power input (kilowatts) necessary for a G value of 900 s^-1. The water temperature is 22 degree C. The flow described in Prob. 1 is to be flocculated in a basin having four flocculators with transverse paddle units. The basin may be a maximum of 10 m wide and 4 m deep to connect to the settling basin. Determine: Basin dimensions Power requirements Paddle configuration and rotational speed The best Gt value for this system has been found to be 3.5 times 10^4.

Explanation / Answer

Q.1: (a): Given the volume of water processed per day = 24500 m3/day

Here we are using lime [Ca(OH)2]- soda ash [Na2CO3] softening method.

The mass of chemicals required is shown in the figure below:

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