Home Courses Treatment of Urban Sewage Course materials Lectures 5. Elaboration Question 8

5. Elaboration Question 8

Course subject(s) 5. Nitrogen and phosphorus removal

Question 8: Chemical phosphorus removal with lime

Estimate the mass and volume of sludge produced in a primary sedimentation tank from the precipitation of phosphorus with lime. Assume that 60% of the TSS is removed without the addition of lime, and that the addition of 400 mg/l of Ca(OH)2 results in an increased removal of TSS to 85%. Assume the following data apply:

  1. Wastewater flowrate = 1000 m3/d
  2. Wastewater Total Suspended Solids (TSS) = 220 mg/l
  3. Wasteater Volatile Suspended Solids (VSS) = 150 mg/l
  4. Wastewater PO43- as P, mg/l = 10 mg/l
  5. Wastewater total hardness as CaCO3 = 241.3 mg/l
  6. Wastewater Ca2+ = 80 mg/l
  7. Wastewater Mg2+ = 10 mg/l
  8. Effluent PO43- as P, mg/l = 0.5 mg/l
  9. Effluent Ca2+ = 60 mg/l
  10. Effluent Mg 2+ = 0 mg/l
  11. Chemical sludge properties
    • Specific gravity = 1.07
    • Moisture content= 92.5%

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