THE WASTEWATER TREATMENT B
TEST EXAM WITH COMPLETE
SOLUTIONS 2026
A poly solution for a jar test needs a concentration of 10,000 mg/L. The undiluted
polymer that will be used in the process contains 40% poly by weight and has a specific
gravity of 1.04. How much undiluted poly is needed to make the poly solution? Assume
the stock solution will be made in a 1 L flask. - ANSWERS10,000 mg/L poly solution =
1% poly solution
C₁V₁ = C₂V₂
(40%)V₁ = (1%)(1L)
V₁ = 0.025L = 25 mL
Determine the poly feed rate in lbs/d if a poly dose of 150 mg/L yields best results, the
sludge contains 4.6% solids, and the sludge flow rate is 111 gpm - ANSWERS111
gal/min * 3.785 L/gal * 1 min/s = 7 L/s
Poly feed rate = Poly dose x Sludge feed rate
Poly feed rate = 150 mg/L * 7 L/s = 1,050 mg/s
Poly feed rate = 1050 mg/s * 1 kg/10⁶ mg * 2.204 lb/kg * 60 s/min * 60 min/hr * 24 hr/d
Poly feed rate = 200 lb/d
What is the typical residential water use?
What is the typical residential BOD loading? - ANSWERSWater use: 100
gal/day/person
Loading: 0.20 lbs BOD/day/person
Describe the BOD test procedure - ANSWERS1. Collect a wastewater sample. Add a
few mL's of nutrient rich, pH buffered water to 300 mL BOD bottle. Fill rest of bottle with
wastewater.
Poly feed rate equation - ANSWERSPoly feed rate = Poly Dosage x Sludge Feed Rate
x 8.34
TEST EXAM WITH COMPLETE
SOLUTIONS 2026
A poly solution for a jar test needs a concentration of 10,000 mg/L. The undiluted
polymer that will be used in the process contains 40% poly by weight and has a specific
gravity of 1.04. How much undiluted poly is needed to make the poly solution? Assume
the stock solution will be made in a 1 L flask. - ANSWERS10,000 mg/L poly solution =
1% poly solution
C₁V₁ = C₂V₂
(40%)V₁ = (1%)(1L)
V₁ = 0.025L = 25 mL
Determine the poly feed rate in lbs/d if a poly dose of 150 mg/L yields best results, the
sludge contains 4.6% solids, and the sludge flow rate is 111 gpm - ANSWERS111
gal/min * 3.785 L/gal * 1 min/s = 7 L/s
Poly feed rate = Poly dose x Sludge feed rate
Poly feed rate = 150 mg/L * 7 L/s = 1,050 mg/s
Poly feed rate = 1050 mg/s * 1 kg/10⁶ mg * 2.204 lb/kg * 60 s/min * 60 min/hr * 24 hr/d
Poly feed rate = 200 lb/d
What is the typical residential water use?
What is the typical residential BOD loading? - ANSWERSWater use: 100
gal/day/person
Loading: 0.20 lbs BOD/day/person
Describe the BOD test procedure - ANSWERS1. Collect a wastewater sample. Add a
few mL's of nutrient rich, pH buffered water to 300 mL BOD bottle. Fill rest of bottle with
wastewater.
Poly feed rate equation - ANSWERSPoly feed rate = Poly Dosage x Sludge Feed Rate
x 8.34
