Your firm has been contracted to perform a feasibility study for a centralized water treatment plant in the Town of Alden. The treatment plant will have 2 processes in parallel, and Q design = 325,000 gpd for each of the parallel processes. Town of Alden Raw Water Data
Parameter concentration, mg/L
Calcium 130
Magnesium 10.1
Sodium 46.7
Alkalinity 257
CO2 10
Chloride 75
Sulfate 39
Nitrate 2.3
pH 7.9
Complete the following:
a) Draw the raw water bar chart.
b) Using 10SS, design a well ventilated, multiple tray aerator for dissolved gas treatment. [CO2] initial = 10 mg/L; [CO2] effluent = 2 mg/L.
i. Calculate the number of trays needed, assuming 6-inch intervals.
ii. Calculate the total tray area per aerator, sf
iii. Calculate the single tray dimensions, ft x ft, using 6" intervals between trays
iv. List the contaminants that can be removed using multiple tray aerators.
v. Calculate the HLR and compare it to 10SS.
c) Hardness treatment (based on 10SS)
i. Determine the maximum volume for a rapid mix chamber, in ft3
ii. Determine the minimum volume for the flocculation basins and the dimensions of the basin, L x W x D, all in ft. Assume W:D = 1:1 for each basin.
iii. Design a circular clarifier with peripheral weirs. Determine:
a. The minimum volume based on detention time, tD, ft3
b. The surface area, ft2
c. The diameter, ft
d. The side water depth, ft
e. The weir loading rate and compare it to 10SS
d) Granular filters (based on 10SS)
i. Calculate the total surface area needed to meet 10SS, ft2
e) Sketch your design of the Alden WTP in plan view
f) Material handling: Calculate the following based on removing all the hardness (based on the Calcium and Magnesium concentrations above).
i. Amount of CaO used, in lbs/day, if the purity is 90%
ii. Amount of Na2 CO3 used, in lbs/day, if the purity is 90%
iii. Amount of CaCO3 produced, in lbs/day, if the sludge cake is 25% solids
iv. Amount of Mg(OH)2 produced, in lbs/day, if the sludge cake is 25% solids
v. Amount of CO2 required, in mg/L, if the HCO3- /CO3-2 ratio is 75/25.
g) Draw the final bar chart for the treated water.