Collections Systems Flashcards
chapters 2 and 3
What are the 11 collection system problems?
- Gravity Flow- inadequate
- Poor Construction, design, shortcuts
- No flexible pipes or joint tightness
- Corrosion of sewer pipes_hydrogen sulfide gas
- Roots from plants
- Lack of money for maintenance
- Given to street department
- Groundwater infiltration
- Not reducing infiltration/flow correctly
- Negligence, vandalism
- Poor records.
What are 3 reasons for collection systems?
- Sanitation
2.Innoculation
(vaccination)
3.Isolation
What is operation and maintenance?
Not allowing wastewater to overflow into the street or into homes.
Name 4 factors operators are responsible
for
- Preserving the community’s capital investment
- Protecting public health and safety.
- Protecting the environment
- Controlling O and M expenses
What is the purpose of a wastewater collection system?
To collect and convey the wastewater from community’s homes and industries.
The water carries the wastes in the form of
dissolved or suspended solids
Wastewater collection systems must be properly designed and constructed to provide a water velocity of greater than
2 feet per second
What strongly influences the collection system?
Topography-
which means
Surface contour
Why would a storm water and wastewater system be combined?
To divert excess water until treated
How is the amount of wastewater conveyed determined?
Analysis of present and future quantities of domestic, commercial and industrial wastewater-anticipated groundwater infiltration and surface water inflow.
Ideally, a wastewater collection system should be designed to
Convey the estimated peak flow for maximum population after fully developed. (10-30 years)
Domestic wastewater flow is calculated by
Multiplying estimated population times per capita flow factors-
Ranges from 70-100 gallons per person, per day.
Wastewater flows from commercial/industrial areas are estimated how?
in terms of gallons per day per acre
Inflow can be reduced by
sealing manhole covers that flood
The flow of wastewater in a collection system will vary in a 24 hour period.
______ flow early am,______ flow around noon
minimum flow early morning
maximum flow around noon time.
Flow measurement in a sewer pipe is based on
Flow rate equals velocity of flow multiplied by the cross sectional area of the flow.
Q, cubic feet/second=(Area, Sq Ft)x(Velocity, Ft/Second)
Pg 41, example 2
Velocities in sewers should be measured:
In the field to be sure actual velocities are high enough to prevent the deposit of solids.
Velocities can be measured using ____ and
_____
dyes or floats
Total travel time from insertion of dye until the dye is no longer visible at the downstream manhole is noted as (_)
(t)
Floats can be any objects that_____
can easily be seen
The problem with using floats is ____^^
They get caught up
What is the formula for velocity?
Velocity is feet per second
distance (ft)
_______
time (sec)
distance in feet divided by time in seconds
Knowledge of daily and annual flow rates in a system are useful for _____
Planning programs for systems
Why is a diurinal graph useful?
Shows condition of system and amt of inflow and infiltration.
Chart on pg 43
A building sewer can begin outside the building or _____
2-10 feet from the foundation
study diagram3.2 on page 44
Lateral and branch sewers are ____^
The upper ends of the street sewer components of a collection system.
Study pg. 48
Main sewers collect wastewater of _____
Several lateral and branch sewers-
area of several 100 acres.
Trunk sewers are the main ____
Arteries of the wastewater system
Intercepting sewers receive
The wastewater from trunk sewers and convey to treatment.
Lift stations are used in____^
gravity collection systems to pump wastewater to a higher elevation
