1. Sewage flow rates vary by source and with a time of the day, the season of the year and weather conditions.
a) True
b) False
Explanation: The rate of usage of water depends on the population of a city of a country. Sewage generation in terms depends on water usage. Different cities use the quantity of water based on their needs. Hence the sewage flow rates vary by source and with a time of the day, season of the year and so on.
2. A proper assessment should be made before sewers are sized or treatment plant capacities are set.
a) True
b) False
Explanation: Different treatment plants produce different quantities of wastewater depending upon the water needs and usage within the industry. The quantity of wastewater in sewer depends upon the population in that area and water usage. Hence proper assessment should be made considering both peak and normal conditions.
3. What is the lowest wastewater flow in hospitals?
a) 50 gpcd
b) 700 lpcd
c) 900 lpcd
d) 40 lpcd
Explanation: The unit lpcd stands for litres per capita per day and gpcd stands for gallons per capita per day. 40 lpcd indicates the minimum water usage for places like kids play home and schools. 700 lpcd is for hospitals.
4. __________ in residential areas resemble water usage patterns in those areas.
a) Hydrographs
b) Sewage flow patterns
c) Dry period patterns
d) Daily flow
Explanation: The water usage depends upon the population, number oh houses and the type of water usage in that area. Sewage flow in turn depends upon these activities. Hence sewage flow patterns in residential areas resemble water usage patterns in those areas.
5. A graph showing discharge versus time past a specific point in a conduit carrying flow is called?
a) Water flow graph
b) Precipitation graph
c) Hydrograph
d) Variation graph
Explanation: A graph showing discharge versus time at a specific point in a conduit carrying flow or river is called ‘hydrograph’. Hydrograph helps in understanding the flow characteristics of water at different time intervals.
6. The maximum velocity in a channel section often occurs _______ the water surface.
a) Above
b) Below
c) Between
d) Top
Explanation: A closed or an open conduit always has different velocities of flow within the section. The bottom of the channel is provided with the certain slope for the water carrying foreign particles to flow easily. Hence the velocity is maximum at the bottom of the water surface.
7. What is the maximum velocity of tap water such that the flow causes low noise?
a) 0.2-0.3 m/s
b) 0.5-0.7 m/s
c) 1.0-2.5 m/s
d) 1.5-2.5 m/s
Explanation: The high rate of flow of water can lead to increasing sound levels of flow which leads to noise. Hence minimum flow of water should be considered. 0.5-0.7 m/s is the maximum velocity of tap water that produces less noise levels. 1.0-2.5 m/s of water flow leads to high noise levels.
8. Which of these equations is used to calculate the water velocity inside of a pipe?
a) A=Q/I
b) V=0.408 Q/ D2
c) L=C*Q
d) Q=A*V
Explanation: The first formula is used to calculate the infiltration area. The third formula is used to calculate the load of wastewater. The fourth formula is used to calculate the rate of flow. The second formula is used to calculate the velocity of flow inside of a pipe (V) where Q stands for flow rate of water inside pipe and D stands for pipe diameter (inside).
9. What is the minimum velocity required in sewers to keep the foreign particles from settling?
a) 3 ft/sec
b) 5 ft/sec
c) 10 ft/sec
d) 12 ft/sec
Explanation: If the velocity is too less then the solid or foreign particles which are very minute in size may settle down. Hence a minimum velocity is required to keep these particles moving along the flow is likely to be 3 ft/sec.
10. Exceeding 10 ft/sec may increase the likelihood of hydraulic surges
a) True
b) False
Explanation: 8 ft/sec is the maximum allowable velocity in public water mains. Increasing velocities beyond this limit may lead to hydraulic surges which lead to the excessive pressure in the water systems.