Wastewater Collection System Operator

What is the primary purpose of a wastewater collection system?

• ATo treat wastewater before discharge
• BTo convey wastewater from its source to a treatment facility
• CTo store stormwater for later irrigation use
• DTo disinfect sewage in transit through the pipes

Which pipe material is most commonly used for modern gravity sewer installations in diameters from 8 to 15 inches?

• ACast iron
• BPVC (polyvinyl chloride)
• CCopper
• DLead-jointed clay

What is the minimum velocity typically required in a gravity sewer to achieve self-cleansing flow?

• A0.5 ft/s
• B2.0 ft/s
• C5.0 ft/s
• D10.0 ft/s

What is a manhole's primary function in a gravity sewer system?

• ATo increase the velocity of flow through the system
• BTo provide access for inspection, cleaning, and maintenance of sewer lines
• CTo chemically treat wastewater before it reaches the plant
• DTo store excess flow during peak periods

What is infiltration in a wastewater collection system?

• AWastewater leaking out of the collection system into the ground
• BGroundwater entering the collection system through defects in pipes, joints, or manholes
• CStormwater entering the system through roof drains connected to the sewer
• DTreated effluent returning to the collection system

A collection system operator discovers that a gravity sewer line has a sag or belly where wastewater pools. What is this condition called?

• AAn inverted siphon
• BA sag or belly (negative grade)
• CA force main segment
• DA drop manhole connection

What atmospheric hazard is the greatest concern when entering a manhole or other confined space in a collection system?

• AExcessive nitrogen levels only
• BOxygen deficiency, toxic gases such as hydrogen sulfide, and explosive methane
• CUltraviolet radiation from sunlight reflecting off standing water
• DNoise exceeding 90 decibels from flowing wastewater

What is the purpose of a force main in a wastewater collection system?

• ATo convey flow by gravity at a steeper-than-normal slope
• BTo carry wastewater under pressure from a pump station to a point of discharge or gravity…
• CTo filter solids from wastewater before it enters the treatment plant
• DTo bypass flow around a pump station during emergencies

During CCTV inspection of a sewer line, the camera reveals multiple offset joints. What does this defect indicate?

• AThe pipe was manufactured with uneven wall thickness
• BAdjacent pipe sections have shifted, creating a step or misalignment at the joint
• CThe camera lens is distorted and needs recalibration
• DThe pipe interior coating has bubbled and delaminated

What type of pump is most commonly used in wastewater lift stations?

• APositive displacement gear pump
• BSubmersible centrifugal pump
• CReciprocating piston pump
• DPeristaltic pump

An operator notices that a lift station pump is cycling on and off rapidly (short cycling). What is the most likely cause?

• AThe wet well is oversized for the incoming flow
• BThe wet well effective volume is too small relative to the pump capacity
• CThe force main has a large air pocket that needs bleeding
• DThe pump impeller is severely worn

What is the Manning equation used for in collection system design and operation?

• ACalculating chlorine demand for disinfection
• BDetermining flow velocity and capacity in gravity sewers based on slope, roughness, and p…
• CSizing chemical feed pumps for odor control
• DCalculating the detention time in a wet well

What is the purpose of a drop manhole?

• ATo reduce the velocity of flow in a steep gravity sewer
• BTo allow an incoming sewer at a higher elevation to connect to a lower manhole without ca…
• CTo store grit and solids for periodic removal
• DTo provide an emergency overflow to a storm drain

What is the primary concern with hydrogen sulfide (H2S) in a wastewater collection system?

• AIt increases the biological oxygen demand of the wastewater
• BIt is toxic to humans at low concentrations and causes crown corrosion of concrete pipes…
• CIt raises the pH of wastewater above acceptable limits
• DIt dissolves PVC pipe material from the inside

A sewer line is being cleaned using high-velocity water jetting. What is the primary mechanism by which jetting removes debris?

• AChemical dissolution of grease and mineral deposits
• BThermal softening of pipe scale caused by heated water
• CHigh-pressure water impact that dislodges and flushes debris downstream or upstream to a…
• DSuction created by the nozzle pulling debris into the jet hose

What does CMOM stand for in wastewater collection system management?

• AChemical Management and Odor Mitigation
• BCapacity, Management, Operation, and Maintenance
• CCollection Main Overflow Monitoring
• DConfined-space Manhole Operations Manual