Question

Problem 1. (29 pts) Jar testing for the water treatment system with a design flow of 37,843 m/d indicates a ferric chloride dosage of 50 mg/L is optimal. The raw water suspended solids concentration is 35 mg/L and the alkalinity is 65 mg/L as Cacos. Pilot studies indicate that the sludge from the settling tanks will consist of 1.5% solids and have a wet sludge specific gravity of 1.15. (a) Determine if it is necessary to adjust the alkalinity of the water in order to maintain at least a level of 30 mg/L as CaCO3 . (b) Estimate the daily volumetric rate of sludge handling required.

Answer 1

Recity+ 3.1603 ---> Fe(OH)3+42073610 no. of males os reciz= 16x103 I mole of recl react with 3 moles of Hoog mole of HCO3 = 2 x 20 weight of Alkalinity = 150x50x103 t as calz B = 46.24 mal as calo₂ available alkalinity servis =65-30 = 35 mgle as cacoz can Required alkalinity = 4624-35 = 11:24 mg/L as Caloz As available alkalimine is more than min, alkalinity nde necessary to adjust alkalinity. (b) mole of Tecol);= 1522 = 0,3092 weight of the Col) y = 0.3082 x 106.87 Precipitation reloH= 22 qu ingle raw water solid concentration - 35 ng/L FeColt), sludge = 32.94x37843x153x106 kg/4 =12467 Eglu Raw water solids - 3.5 ingle in 1.5 % solid > 98.5% water let & mg/L slude = xx 15 = 35 =)x= 2333.33 mg/ Sludge in row wates = 2333,33 x 37.843 = 88300.2 19 14 Total sludge -88300 2 +12467 - 89545.9 kg lu Volumetric rate of Total sludge wohl 89546-9 sludge handling = 1954 1000 kJ/m3 g/d = rsxooo .- 71.86 mild