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