WASTEWATER COLLECTIONS 2 STUDY
GUIDE QUESTIONS AND ANSWERS
WITH SOLUTIONS 2024
Why should the pumps in a lift station not start and stop frequently? - ANSWER Pump in a lift station
should not start and stop frequently because frequent motor starts cause excessive wear on equipment
and may cause surges in the Wastewater flow. Also, frequent starting will increase power cost.
What problems develop in a wet well that is too large? - ANSWER If a wet well is too large, solids will
tend to accumulate on the bottom because the wet well will be acting as a settling tank, accumulated
solids could block the pump suction pipes and over a period of time, can generate dangerous gases and
odors.
3. What is the main advantage of variable-speed pumping equipment? - ANSWER The main advantage of
variable speed pumping equipment is that the pumping speed can be adjusted to match the capacity or
the flow rate into the wet well.
4. In collection systems, why have bar racks or screens at the list stations been eliminated by some
agencies? - ANSWER They have been removed because most pumping units are equipped with open
impellers or closed two-port impellers sized to pass solids up to the size of a 2.5 inch diameter sphere
and it also eliminates the necessity to visit the lift station more than once a day.
5. What is the purpose of a sump pump in a dry well? - ANSWER They are used to remove excess water
such as seal water leakage and clean up water.
6. What happens when a seal fails on a submersible pump? - ANSWER When the seal fails, the waste
water can leak into the motor compartment and the unit will short or burn out the motor.
7. What are some advantages of solid-state motor starters compared to Conventional electromechanical
starters? - ANSWER Solid State motor starters incorporate current sensing devices in each phase of the
power being supplied to the motor this allows much more precise overload protection for the motor. It
can also detect nuisance type control inputs from floats, pressure switches, or other input devices. Other
features include phase unbalanced and phase loss protection.
GUIDE QUESTIONS AND ANSWERS
WITH SOLUTIONS 2024
Why should the pumps in a lift station not start and stop frequently? - ANSWER Pump in a lift station
should not start and stop frequently because frequent motor starts cause excessive wear on equipment
and may cause surges in the Wastewater flow. Also, frequent starting will increase power cost.
What problems develop in a wet well that is too large? - ANSWER If a wet well is too large, solids will
tend to accumulate on the bottom because the wet well will be acting as a settling tank, accumulated
solids could block the pump suction pipes and over a period of time, can generate dangerous gases and
odors.
3. What is the main advantage of variable-speed pumping equipment? - ANSWER The main advantage of
variable speed pumping equipment is that the pumping speed can be adjusted to match the capacity or
the flow rate into the wet well.
4. In collection systems, why have bar racks or screens at the list stations been eliminated by some
agencies? - ANSWER They have been removed because most pumping units are equipped with open
impellers or closed two-port impellers sized to pass solids up to the size of a 2.5 inch diameter sphere
and it also eliminates the necessity to visit the lift station more than once a day.
5. What is the purpose of a sump pump in a dry well? - ANSWER They are used to remove excess water
such as seal water leakage and clean up water.
6. What happens when a seal fails on a submersible pump? - ANSWER When the seal fails, the waste
water can leak into the motor compartment and the unit will short or burn out the motor.
7. What are some advantages of solid-state motor starters compared to Conventional electromechanical
starters? - ANSWER Solid State motor starters incorporate current sensing devices in each phase of the
power being supplied to the motor this allows much more precise overload protection for the motor. It
can also detect nuisance type control inputs from floats, pressure switches, or other input devices. Other
features include phase unbalanced and phase loss protection.
