Chapter 2 Wastewater Collections Volume1

Question 1

What is a stormwater collection system?

Answer 1

Star War collection system conveys water resulting from runoff of rainfall and snow melt from buildings and surrounding unpaved and paved areas to a natural water course or body water usually without treatment. This system also conveys excess water supply to urban areas for irrigation and surface cleaning.

Question 2

What is a combined Wastewater and stormwater collection system?

Answer 2

Conveys a combination of Wastewater and stormwater to a treatment plant.
Occasional Heavy Rain or cloudburst may produce flows that exceed the wastewater treatment plants capacity the store water is then returned to the plant for proper treatment. In a few older communities with combined Wastewater collection systems Provisions are usually made to relieve the collection system and treatment plant by diverting the excess flow and providing partial treatment + disinfection before discharging the flow to water or onto land.

Question 3

What should a collection system operator understand how the system was designed and constructed?

Answer 3

Collection system operators should understand how the system they are responsible for operating and maintaining were design and constructed so that they can determine the correct action to take when the system fails to operate properly.
Also they will be they will be able to discuss design construction and inspection with engineers

Question 4

What is the purpose of a Wastewater collection system?

Answer 4

The purpose of a Wastewater collection system is it collect the Wastewater from a communities homes and businesses and conveying that to an appropriate velocity to a wastewater treatment plant.

Question 5

In the areas where the Topography is unfavorable for Gravity Wastewater collection system what types of collection systems may be used?

Answer 5

The areas where the Topography is unfavorable for a Gravity Wastewater collection system a pressure or vacuum collection system may be used.
Pressure sewers maybe installed instead of gravity sewers in an area because
1) pipe slope is Not Practical
2) smaller pipe size can be used due to pressurization
3) reduced pipes size can be installed due to lack of infiltration and inflow

Question 6

List the sources or types of Wastewater conveyed by Wastewater collection systems?

Answer 6

Sources or types of Wastewater can vary by Wastewater collection systems include:
Wastewater from homes and businesses
as well as
Ground water infiltration
Surface water inflow produced in the service area.

Question 7

What factors are considered in estimating Peak flow from a service area?

Answer 7

The peak flow from a service area is estimated on the basis of Maximum population and full commercial and Industrial Development of an area with additional allowances for infiltration and inflow.

Question 8

What measurement aids are commonly used to measure actual flow velocity in sewer mains?

Answer 8

The flow velocity in a sewer main can be measured using either dies or floats.

Question 9

List the parts or components of a gravity Wastewater collection system

Answer 9

Gravity Wastewater collection system includes:

• Building sewers
• .Lateral and Branch sewers. * * Main sewers.
• Trunk sewers.
• Intercepting sewers.
• Lift stations.

Question 10

List of principal components of a low-pressure Collection system?

Answer 10

Components of a low-pressure collection system include:

• Gravity sewers
• holding tanks
• grinder pumps
• force mains

Question 11

What’s the principal components of a vacuum collection system.?

Answer 11

Components of a vacuum collection system include:

• Gravity sewers
• interface units
• holding tanks
• vacuum valves
• vacuum Mains and
• vacuum pumps

Question 12

Operator and maintenance considerations when comparing pressure sewers with gravity systems include the following.

Answer 12

Pressure systems have

1) higher energy cost for pumping
2) Greater cost for pumping facilities
3) fewer stoppages
4) no root intrusions
5) no extra capacity for infiltration and inflow
6) no deep trenches or deeply buried pipe
7) no inverted siphons for crossing roads or rivers

The principal components of a low-pressure collection system include gravity sewers holding tanks grinding pumps and force meds

Question 13

What is the purpose of a backflow preventer?

Answer 13

Backflow preventers are used to stop the accidental backflow or reverse flow of Wastewater into buildings from the sewer

Question 14

List the three main types of Wastewater backflow preventers.

Answer 14

The three main types of Wastewater backflow preventers are

• the Overflow type
• the check fail type and an *automated systems which uses a flexible diaphragm and level sensing device.

Question 15

What are inverted siphons?

Answer 15

Inverted siphons are sewer lines installed lower than the normal gradient of the sewer line to pass under obstructions such as watercourses and depressed roadways.

Question 16

What is the purpose of flow Regulators in Wastewater collection systems?

Answer 16

Flow Regulators in Wastewater collection systems are used to divert the flow of Wastewater from one sewer line to another for the efficient use of the system and to prevent overloading one portion of the system.

Question 17

Why are field surveys conducted

Answer 17

Field surveys are conducted by Engineers to record the location of the physical features and the elevation of ground surface along the planned route of the sewer lines in the collection system. Full service include both walk surveys and level surveys

Question 18

What is the difference between a route survey at a level survey?

Answer 18

Route surveys determine the location of physical features that will influence of horizontal elevation of a sewer line.
Level surveys determine elevations of the ground surface along the route of the sewer the buildings to be served and the elevation of underground and obstructions and Pipelines.

Question 19

Why should the Wastewater in a sewer main move at Scouring velocity during the average day flow or at the least during the maximum daily flow?

Answer 19

The Wastewater in a sewer line should move at Scouring velocity during the average daily flow or at the very least during the maximum daily flow to prevent the deposition and billing of solids in the sewer

Question 20

What tends to happen at collection systems in flat regions with low flow velocities

Answer 20

In collection systems in flat regions with low flow velocities the solids tend to settle out of the Wastewater thus causing sewer stoppages and the generation of toxic hydrogen sulfate gas

Question 21

If a 10 inch diameter sewer on a .005 foot slope will not carry the wet weather design flow what can be done to provide adequate capacity?

Answer 21

If a 10 inch diameter sewer on a .005 ft pre slope will not carry the peak wet weather design flow either design slope or pipe diameter of both could be increased until the appropriate combination of sewer line slope and diameter would meet the desired capacity and velocity.

Question 22

Why are sewers usually not placed in easements?

Answer 22

Sores are usually not place in easements because they are more difficult to gain access to and to maintain then sewers in streets.

Question 23

What factors control the width of a sewer Trench?

Answer 23

The width of a sewer trench is controlled by the diameter of the sewer pipe clearance for pipe laying soil stability for safety during excavation and the excavation procedures.

Question 24

What is the difference between flexible and rigid pipe?

Answer 24

A flexible pipe will bend or bulge from its usual shape when subjected to a load without being adequately supported however it will not crack under the loads and will return the other to its original shape when they load is removed.
And rigid pipe will require less support however it will crack when the combination of the load and the pipe and its support causes stress the exceeds the strength of the pipe it will not return to its original shape when the load is removed.

Question 25

List as many of the most commonly used sanitary sewer pipe materials as you can recall.

Answer 25

ACP, 
CIP, 
RCP, 
NRCP 
PCPP 
VIP 
DIP 
ABS, 
ABS composite 
PE
PVC
RTR
RPM

Question 26

What makes pipe joints one of the most critical components of the piping system in sanitary sewer systems

Answer 26

Pipe joints are one of the most critical components of the piping system because of the need to control
ground water infiltration Wastewater exfiltration and root intrusion in sanitary sewer systems

Question 27

Why are some manhole barrels made with fiberglass?

Answer 27

Some manhole barrels are made with fiberglass for use in areas with high groundwater and corrosive materials in the Wastewater conveyed

Question 28

What is meant by the plan View and profile view of a sewer?

Answer 28

The plan view is a top view of a sewer and shows the pipe manholes and the street the profile view is a side view of a sewer and shows the pipe manholes invert elevations Street surface and underground pipes such as storm sewers, gas Mains, water meters and electrical cables

Question 29

When reviewing plans for a new sewer where would traffic be a problem?

Answer 29

When reviewing plans for a new sewer traffic could be a problem wherever crews must work such as around manholes. Also consider where Vehicles can be parked when operators and Equipment require access to a manhole

Question 30

Why is the slope of the Shelf in a manhole important?

Answer 30

The slope of the shelf of a man who is important because if the shelf is too flat it will get dirty and if the Shelf is too steep it can be a slippery hazard to operators.