One method of removing phosphate from wastewater effluents is to precipitate it with aluminum sulfate. A plausible stoichiometry (but not exact because aluminum and phosphate can form many different chemical materials) is:
2 PO43- + Al2(SO4)3 2 AlPO4 + 3 SO42-
If the concentration of phosphate (PO43-) is 30 mg/L, how many kg of aluminum sulfate must be purchased annually to treat 40 L/sec of wastewater? How many kg of precipitate will be formed as sludge if all of the phosphate is precipitated as AlPO4?