Question

A surface water treatment plant treats a 6,000 L/day flow with alum coagulation, identified by the following stoichiometric reaction:

Al₂(SO₄)₃ ∙ 14 H₂O + 6HCO₃^- ↔ 2Al(OH)₃ (s) + 6 CO₂ + 14 H₂O + 3 SO₄^2-

Molecular weights (g/mol):

Al₂(SO₄)₃ ∙ 14 H₂O  =   594.5

HCO₃^-  =  61

Al(OH)₃  =  78

SO_4^2-  =  96.1

Jar tests indicate that 55 mg/L of alum are required to optimally treat the surface water. Removal of approximately 20.2 mg/L of suspended solids also occurs in this sytem. Estimate the mass of sludge disposed of daily (g/day).

Answer 1

Ans. 86.59 g/L ( total sludge generated per day)