Wastewater Exam Flashcards
The slope of a sanitary sewer is measured by the difference in __________ elevations over a length of pipe.
Invert
What prevents cross connections?
Air gap
When potable water supply is connected to a non-potable water supply it’s considered what?
Cross connection
Wastewater carries into a collection system may come from where?
Inflow
When using a hydraulic sewer cleaning method care must be taken by the operator as to not cause ____________ in Gomes and businesses.
Flooding
Disease producing bacteria are called what?
Pathogenic
A manhole with a center grating is normally used for what?
Storm sewers
A “pig” is used as a _________ in a Force main.
A reamer
A minimum scouring velocity of 2 ft/sec in sewers is necessary so that _________ won’t build up in a sewer and reduce ________ capacity.
Solids
Flow
A potable water supply connected to a potential source of pollution is defined as?
Cross-connection
When dealing with collection systems, I & I refers to what?
Infiltration & inflow
Corrosion of sewer pipes may be caused by __________ in wastewater.
Acids
In a collection system, wastewater that contains not “free” or dissolved oxygen is referred to as what?
Anaerobic
The primary reason why it is important not to have cross-connections of sewers with water supply systems is possible ___________ water contamination.
Drinking
A “pig” would most likely be used in the cleaning of what type of sewer line?
Force main
Flow rates can be expressed in what unit of measurement?
MGD (Million Gallons per Day)
An opening in a sewer provided for the purpose of access is what?
Sewer manhole
What is considered the top of the sewer pipe?
Crown
The primary purpose of wastewater disinfection is to prevent water _________________.
Contamination
What is considered the scouring velocity of sanitary sewers?
2 ft/sec
The cylindrical section between the cone and the shelf is the manhole what?
Barrel
When computing or expressing flow what are the abbreviations?
ft/sec
gpm
MGD
Settlement, first action, and nearby activities can cause a sewer line to what after years of service?
Move
The end of a sewer pipe that is formed to fit into the bell of the next pipe is called what?
Spigot
Come, barrel, and shelf are all components of what?
Manhole
A scouring action will develop when the velocity of a collection systems flow is _____ ft/sec or more.
2
Direct discharge of storm water to a sewer is called what?
Inflow
Solids that settle to the bottom of a wet well are called what?
Settable solids
Odors encountered in manholes at the end of force-mains are usually cause by _____________ bacteria.
Anaerobic
What is a disease that can be cause by the ingestion of wastewater?
Typhoid
The gas most typically associated with septic wastewater is?
Hydrogen sulfide
The recommended maximum allowable velocity in sewers is what?
10 ft/sec
Hydrogen sulfide in a collection system can also cause _________ corrosion.
Crown
The flow of groundwater into a sewer through faulty joints is defined as?
Infiltration
A lift station O & M manual should include names and emergency numbers of collection system _____________, vendors, and _______________.
Operators
Contractors
To prevent any water of questionable quantity from contaminating potable water sources we use a what?
Air-gap
A collection system that serves mainly residential consumers has the lowest flow at what time of day?
Late night
A sewer intended to receive both wastewater, storm water and/or surface water is considered?
A combined sewer
The lowest point in a channel is considered a what?
Invert
Poor joints, cracked pipes, and root intrusion can all cause what?
Infiltration
Clean outs, barscreens, and lift stations are all apart of the what?
Collection system
MGD means?
Million Gallons per Day
The pH of a solution is based on the ____________ ______ concentration.
Hydrogen ion
When there is a collection system failure, what may be compromised?
Public safety
During a rainstorm, what collection characteristics may increase the most?
Inflow
The flow of wastewater entering the collection system is defined as?
Influent
BOD is defined how?
Biochemical Oxygen Demand
Heavier materials and settleable solids are removed from wastewater by what?
Primary treatment
When you have defective pipe joints water ___________ into sanitary sewers.
Infiltrates
Building sewers and lateral sewers are used to convey _____________ from homes or businesses.
Wastewater
High concentrations of heavy metals must be precluded by industrial _________________ so they don’t affect the treatment process.
Pretreatment
A medium strength wastewater contains how much BOD & TSS?
150-300 mg/L
The best determinant when a sewer line needs to be cleaned is what?
Experience and records
One cubic yard of concrete contains _____ cubic feet.
27
The purpose of a standard manhole is to provide access for ___________ and ____________.
Cleaning
Inspections
Storm drains are intended to carry ___________ and ________ water.
Surface
Storm
The highest flow during a certain period of time is considered the what?
Peak flow
At a junction of two sewers of different levels you’d expect to find a “_________” manhole.
Drop
The bottom where the wastewater flows is considered the what?
Invert
The elevation of a sewer refers to the elevation of the center of the ___________ of the onside of the pipe.
Bottom
If the inside diameter of the pipe is 20 inches, and the pipe wall is 1.5 inches thick, what is the outside diameter of the pipe?
23 inches
Odors from wastewater collection systems usually result from the _______________ conditions developing in solids accumulated in the pipe.
Anaerobic
Exfiltration is a possible danger to public health because _____________ of well water is possible.
Pollution
The size and the slope generally determine the what of a sanitary sewer?
Capacity
The average person contributes how many pounds of suspended solids (SS) to the sewer system daily?
0.20 pounds
What are the three types of sewers?
Storm
Sanitary
Combined
Weir, Venturi meter, and parshall flume are all used when measuring what?
Flow
Excessive flows encountered during a storm are an indication of high rates of what?
Inflow
The maximum natural slope is considered the ___________ of ___________.
Angel of repose
A main sewer line that serves a large territory is considered a what?
Trunk sewer
Exfiltration in wastewater collection systems is a problem because it may contaminate a what?
Aquifer
Time of travel using dye, time of travel using a float and time of travel using a radioactive tracer are all ways of measuring actual ____________ in sanitary sewers.
Velocities
A manhole where the outgoing pipe invert is significantly lower than the influent pipe invert is considered what?
Drop manhole
The gauge pressure that is equivalent to the static head from a 75ft column of water is approximately what?
32.5 psig
Wastewater is normally _______% water.
99.9%
What type of pipe material is most commonly used when crossing under a river or stream?
Ductile iron
One cubic foot of water weighs how much?
62.4 lbs
What is the equation to convert degrees F into degrees C?
5/9 (degrees F - 32)
What is the equation to convert degrees C into degrees F?
9/5 (degrees C) + 32
The minimum velocity allowed to prevent solids deposition in a sanitary sewer line is?
2 ft/sec
Which equation describes the gravity flow of wastewater in sanitary sewer pipes?
The manning equation
The hydraulic radius of a sewer refers to the ________ perimeter divided by the _____________.
Wetted
Diameter
An operator can determine when a large quantity of acids have entered the wastewater plant when the pH of the wastewater ________.
Falls
The surface curve at a free flowing outlet of a pipe would be considered the hydraulic term “______________”
Drawdown
A hydraulic jump is likely to occur when wastewater moving at a high velocity at a shallow depth strikes wastewater have a ________________ depth.
Substantial
Inverted siphons are used for the ________ _____________ of small water courses.
Cross depressions
What are the hydraulic head losses associated with transitions?
Friction and conversion losses
Hydrogen sulfide in the presence of moisture forms an acid that causes what corrosion?
Crown corrosion
What may cause odors in the collection system?
Anaerobic bacteria
The working areas on either side of the invert is considered the what?
Manhole shelf
All sewers should be designed and constructed with hydraulic slopes sufficient to give mean velocities when flowing full or half full of not less than what?
2 ft/sec
A check valve is a valve that prevents what?
Backflow
The purpose of a drop manhole is to accommodate lines at various ___________.
Grades
The decomposition and decay of organic material in a sanitary sewer system containing no free or dissolved oxygen is called what?
Anaerobic
The ideal pipe bedding material is what?
Gravel
Our atmosphere contains ____% oxygen.
21%
Humans can tolerate atmospheres containing a minimum of ______% oxygen.
13%
Anything under _____% oxygen could be fatal.
13%
In order to enter a manhole the oxygen must be between ______% and ______%
19.5%
21%
What is the ideal pipe bedding?
Gravel
Collection systems should be inspected during construction to determine if the contractor is ____________ with the plans and specifications.
Complying
How are sewer pipe joints normally sealed?
O-rings
Vitirfied clay, PVC, and reinforced concrete are commonly used for _____________ sewers.
Sanitary
The maximum natural slope of a spool is considered what?
Angle of repose
A trench that is more than ____ feet deep must be shored.
5 feet
A sewer 89.0 ft MLS means that the bottom of the interior diameter is 89.0 feet above mean _______ __________.
Sea level
The process by which water seeps or passes through soil is called what?
Percolation
In good engineering practice, sanitary sewer lines should be laid at a grade that __________ with the quantity of _______________ to be carried and pipe diameter.
Varies
Wastewater
Vitrified clay, cast iron and steel, and precast and monolithic concrete are common materials used in the construction of what?
Sewer lines
The velocity of flow in a force main during “pump-on” condition should be approximately what?
3-6 ft/sec
Clear water from foundation drains, cistern overflows, roof drains and similar sources should not be connected to sanitary sewers because it tends to hydraulically ______________ the collection system and wastewater treatment plant.
Overload
Newly constructed collection systems must be inspected to ensure there’s no ______________, and to ensure the contractor has complied with _________ and _________________.
Infiltration
Plans
Specification
The minimum designed velocity for wastewater in a sanitary sewer is what?
2 ft/sec
Laying sewer lines on proper grades is essential so the wastewater flows fast enough to prevent solids from ______________. When grades are too flat, the wastewater usually becomes ___________.
Settling
Septic
Clamshell, draglines, and front end loaders are all equipment used in the installation of what?
Sewer
The design of a sanitary collection system should consider the ____________ of people using the system.
Number
What velocity are sewers designed for?
2-10 ft/sec
At a minimum, how far from the edge of a trench should excavated material be placed?
2 ft
The slope of the sewer is defined by the ________ over the _______.
Rise
Run
The free surface slope of a liquid in a pipeline is considered?
Hydraulic gradient
When the trench bottom is so soft and can not safely support the pipe it would be best to ____________ further and _________ with approved material.
Excavate
Refill
What is the best used to control large quantities of water when excavating sewer trenches in sand?
Well points
When reviewing the design of a pump station wet well, you should consider the __________ of the floor.
Slope
The velocity head plus the static head plus the miscellaneous head during pumping equal the total ___________ _______ of flowing liquids.
Dynamic head
The essential requirement of most provisions and specifications for backfilling sewer and storm trenches is to prevent ________________ damage to the newly laid pipe.
Displacement
What is the change in elevation between the upstream invert and the downstream invert in a 400 ft section of 8 inch sewer pipe with a 4.5% slope?
18 ft
When excavating a trench in an existing roadway, it is a good idea to segregate the asphalt from the rest of the material to prevent using the __________ as ____________.
Asphalt
Backfill
Barricades and lanterns should be far enough away from excavation site to be seen and allow fast moving traffic time to _________ _________.
Slow down
Material excavated from the trench should always be piled back at least ____ feet from the trench.
2 feet
What is the term applied to tracing of a trench wall during excavation?
Shoring or sheeting
To bond freshly poured concrete to concrete that has already set up we use something called a what?
Keyway
A grade that has a rise of 6 feet in 600 feet has a grade of what?
1%
A cone that tapers non-uniformly from barrel to manhole cover with one side usually vertical is called an _____________ ____________ cone.
Eccentric Manhole
Joining two pieces of pipe, one of which has a bell or spigot, by means of packed oakum or lead is considered?
Caulking
What material would older collection system sewer pipes, 36 inches in diameter or less, likely be made of?
Asbestos cement
A distance of 10.75 feet is the same as what?
10 ft 9 inches
The reason for digging bell holes for pipe is to give the pipe ________ ___________ between the joints.
Even
Bearing
When laying a 12 inch diameter pipe, the trench should be as ___________ as possible as long as it does not ___________ with the laying of the pipe.
Narrow
Interfere
The method of laying pipe has much to do with the strength developed by the pipe. What method has the highest load factor?
Crushed stone embedment with shaped bottom
The gradient or slope of small sewers should be ___________ than the slope for a larger sewer.
Greater
When backfilling a sewer trench with soil, you should backfill in _____ inch layers and tamp down until the pipe is covered with _____ inches of backfill.
4 inch
12 inches
Compaction, existing landscaping, and vehicle access are all factors when obtaining an easement for _______________ and _______________ of a collection system.
Construction
Maintenance
What is used to measure pressurized wastewater flow?
Magnetic flow meter
How much air pressure will be required to overcome the water pressure in a pressure sensing controller for every foot of water rise in a wet well?
0.433 psi
A wastewater pump station is designed to _______ wastewater.
Lift
Preventing vandalism, public safety, and supporting vehicular traffic are all reasons that manholes are what?
Heavy
The difference between the elevations of the water surfaces in a wet well and the pump discharge is referred to as what?
Static head
A bubbler tube would most likely be found in a pump station ______ _________.
Wet well
By using _____________ __________ corrosion of a metal lift station can be controlled.
Sacrificial metals
Each change in sewer direction, each change in sewer grade, and each each in sewer pipe sizes is where what should be located?
Manhole
The communication in an alarm system is considered?
Telemetry
What are grit chambers designed to remove from wastewater?
Inorganic material
What is a wet well?
Holding tank
Float and electrode switches should be checked at least once a week to see that controls respond to changing ___________ __________.
Water levels
Venturi, magnetic, and parshall flume are common types of what found in pump stations?
Flow meters
What is the indicator organism normally used for determination of pollution in water?
Coliforms
Lift stations are required in wastewater collection systems when topography is poor for ____________ flow.
Gravity
The rate of flow through a parshall flume is determined by wastewater _________.
Depth
At a high elevation on a force main line you would most likely find a what?
Air release valve
Solids deposition, grease build up, and septic conditions and odors are problems that may develop in a wet well if it is too __________.
Large
Flow measurement charts are useful for comparison to detect what?
Inflow
You want to blow fresh air into the _______ well and suck air out of the _______ well.
Wet
Dry
Accumulating grease must be prevented is possible because accumulations often break loose and ________ the pump suction or _______ the pump floats.
Clog
Jam
Rate of flow in a force main leaving a wastewater pump station is measure with what?
Venturi meter
The body of a 6 inch gate valve has “200 WOG” inscribed on it, this means the valve is rated for service at 200 _____ for oil, gas, or cold water.
psi
What is a compound that can be purchased in liquid solution and can be used for disinfection?
Sodium hypochlorite
To reduce the number of mysterious changes in pump station operation, pump stations should have a _______-_____ log established SOP.
Sign-in
A cause of pump cavitation would be improper ___________ and or ________ conditions.
Design
Head
Excessive quantities of heavy metals must be excluded from the collection system because they may affect the what?
Treatment process
When operating a small wastewater pump station with two identical pumps, adjust the controls so that the pumps ____________ in operation.
Alternate
The maintenance of couplings between the driving and driven components include maintaining proper _____________, even with flexible couplings.
Alignment
Compressed air pressurizing a vessel that forces wastewater out through check valves is considered what type of pump?
pneumatic ejector
The depth of lateral and main sewers should generally be approximately ___ feet deep.
6
The width of a sewer trench should be kept to a what?
minimum
The rigid pipe ACP stands for?
Asbestos Cement Pipe
The rigid pipe CIP stands for?
Cast Iron Pipe
The rigid pipe RCP stands for?
Reinforced Concrete Pipe
The rigid pipe PCPP stands for?
Pre-stressed Concrete Pressure Pipe
The rigid pipe VCP stands for?
Vitrified Clay Pipe
The flexible pipe DIP stands for?
Ductile Iron Pipe
The flexible pipe ABS stands for?
Acrylonitrile Butadiene Styrene
The flexible pipe PE stands for?
Poly Ethylene
The flexible pipe PVC stands for?
Poly Vinyl Chloride
A wastewater facility with a relatively short discharge line up to a downstream gravity sewer is?
Lift Station
A wastewater facility that is discharging into a long force main is?
Pump Station
In a manhole used as a wet well station, guide bars are used for the ________ of the pump.
Removal
In a large wet well station, an above ground pump size is ___ to ___ inches. While the submersible pump can be as large as ___ inches.
6 to 8
24
What are normally installed at high points in a force main to blow off air?
Air release valve
A lift station that uses air pressure to eject the wastewater is?
Pneumatic Ejector
The average daily dry weather flow is classified as what flow?
Q1
Seasonal dry weather flow to handle industrial flow is classified as what flow?
Q2
Peak wet weather flow based on highest inflow and infiltration is classified as what flow?
Q3
Pressure head (psi) or elevation head (ft) is the difference in _________ between 2 points.
elevation
Difference in elevation when the pump is off between the surface of the water on the suction side of the pump, and surface of water on the discharge side of the pump is?
Static head
Dynamic heads include static head plus _________ losses.
friction
The wet well in a lift station acts as a _________ basin.
storage
Excessive starting and stopping will occur in pumps if the wet well is too what?
small
Solids will accumulate on the bottom of the wet well and act as a settling tank when it is too what?
large
High water in a lift station is limited to the influent pipe, low water level in a lift station should not fall below the center line on the pump ____________.
impeller
Alternation of pumps during a pump on/pump off cycle will minimize what?
short cycling
Aluminum is corrosion resistant except when it comes in contact with what?
Concrete
Bar racks have been eliminated from wet wells because impellers are sized to pass up solids up to _____ inch diameter sphere.
2.5
Some agencies are installing what to shred rags and debris ahead of wet wells and pumps?
Comminutors
Electrical power in lift stations is a _____-_______ utility power.
three-phase
Frequent motor starts are not good because it creates ______ that breaks down the insulation and can cause a shortage in motor windings.
Heat
The most common type of motor used in lift stations is what? Hint: SCIM
Squirrel Cage Induction Motor
Motor operating temperature will increase one percent for each _____ feet increase in altitude over 3300 feet.
330
Unless specially designed, the motor ambient operating temperature should not exceed _______ degrees Celsius (______ degrees Fahrenheit).
40 degrees Celsius
104 degrees Fahrenheit
_________ controls measure the level of water in the wet well, and __________ controls convert that measurement into a signal to start, stop, or speed up the pump.
Primary
Secondary
In float switches, what metal is used as a conducting metal to turn off and on pumps?
Mercury
1 psi is equal to a column of water _____ feet high.
2.3 feet
Bubbler controls senses the __________ it take to force air out of the bubbler tube.
Pressure
Bubbler tube systems maintain a constant low volume of air of ____ to ____ cubic foot per hour.
1/2
1
Raw wastewater pumps are subject to wear between the bottom of the impeller and volute. Clearance must be maintained to a few ____________ of an inch.
thousandths
The ring that provides a seal between the atmosphere and the liquid end of the pump to prevent air being sucked is?
Lantern ring
Conventional packing for pumps requires slow, continuous leakage of water for the purpose of what?
Lubrication
Jack screws are used in the adjustment of what?
Pump impeller
The volute of the pump houses the what?
Impeller
What is the maximum limit of deflection at the stuffing box for long packing and mechanical seal life?
0.002 inches
If a pump is 12 x 14 x 22 inches on a pump curve, 12 is the size of the __________, 14 is the size of the __________, and 22 is the size of the _________.
Discharge
Suction
Volute
The horsepower required at a given point in order to pump the flow at a given head is?
Brake Horsepower (BHP)
What is the Water Horsepower (WHP) formula?
(Flow GPM)(TDH, ft)/3960
What is the pump efficiency (%) formula?
(WHP)(100%)/BHP
To collect seal water and water used to hose down the dry well facility, the floor of the dry well should be provided with a what?
Sump pump
Gate valves are used for water flow, while plug valves are used for high ______ content like sludge pumping systems.
Solids
