Two Marks Questions with Answers

TWO MARK QUESTION AND ANSWERS

 

1. What is sewage?

Wastes are mixed with sufficient quantity of water & carried through closed conduits under the conditions of gravity flow. This mixture of water and waste products popularly called sewage

 

2. What are the sources of sewage?

Domestic sewage: Originates from urinals, latrines, bathrooms, kitchen sinks, wash basins of residential, commercial or institutional buildings

Industrial sewage: Originates from industrial processes such as dyeing, paper making, brewing etc

Strom sewage (or) storm drainage: Originates from rain storm

 

3. What are the two types of sewage system?

The two types of sewage system are,

(a) Combined system: When the drainage is taken with the sewage then it is called as combined system

(b) Separate system: When the drainage and sewage are taken independently of each through two different sets of sewage is called as separate system.

 

4. Define time of concentration?

The period after which the entire area will start contributing to the runoff is called time of concentration.

 

5. List the components of sewerage system?

The components of sewerage system are

(a) House sewers

(b) Lateral sewers

(c) Branch sewers

(d) Main sewers

(e) Outfall sewers

(f) Man holes.

 

6. What is peak drainage discharge?

The method estimating the maximum rate of storm runoff is called as peak drainage discharge.

 

7. What is meant by biodegradable organic matter? 

The organic matters is decomposed by bacteria under biological action is called biodegradable organic matter

 

8. What are the various tests for finding the quality of sewage?

• Turbidity test

• Colour test

• Tuohoq test

• Odour test

 

9. What is meant by relative stability of a sewage effluent?

The relative stability of a sewage effluent is the ratio of oxygen available in the effluent to the total oxygen required to satisfy its first stage BOD demand

 

10. Differentiate B.O.D & C.O.D

B.O.D (Bio-chemical Oxygen Demand) directly gives the amount of biologically active organic matter (Biodegradable) present in sewage

C.O.D (Chemical Oxygen Demand) is a measure of total organic matter (Biodegradable as well as non- Biodegradable)

 

11. The average sewage flow from a city is 80 × 10° l/d. If the average 5 day B.O.D is 285 mg/l, compute the total daily 5 day oxygen demand in Kg, and the population equivalent of the sewage. Assume per capita B.O.D of sewage per day = 75g.

Quantity of sewage flowing per day : 80 × 10⁶ litres

Average 5 day B.O.D = 285mg 

Total daily 5 day oxygen demand = 285 × (80 × 10⁶) mg = 22,800 Kg

 

12. What are the methods of population forecasting?

(a) Arithmetic increase method

(b) Geometric increase method

(c) Method of varying increment (or) Incremental increase method

(d) Decreasing rate of growth method

(e) Simple graphical method

(f) Comparative graphical method

(g) Master plan method (or) zoning method

(h) The logistic curve method

 

13. Define design period?

The future period for which a provision is mode in the water supply scheme is known as design period.

 

14. What are the factors governing the design period?

The factors governing design period are,

(a) Design period should not exceed the life period of the structure.

(b) If the funds are not in a sufficient, the design period as to be decreased. 

(c) The rate of interest on borrowing and the additional money invested.

 

15. What is critical rainfall duration?

Maximum runoff will be obtained from the rain having duration equal to the time of concentration. This is called critical rainfall duration

 

16. What is intensity of rainfall?

The intensity of a rain is the rate at which it is falling, which it is falling, and it is ex is expressed in cm/hr

 

17. What are the Physical Characteristics of wastewater?

• Carbonaceous substrates

• Nitrogen

• Phosphorous

• Chlorides

• Total and volatile suspended solids (TSS and VSS)

• Toxic metals and compounds

 

19. What is BOD (Biochemical oxygen demand?)

Biochemical oxygen demand or BOD is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period

 

20. What is COD (Chemical oxygen demand?)

Chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water. It is expressed in milligrams per liter (mg/L).

 

21. Mention some shapes of sewer pipes

• Circular shape

• Egg shape

• Horse shoe shape

• Elliptical shape

• Parabolic shape

• Rectangular shape

 

22. What are the forces acting on sewer pipes?

• Internal pressure of sewage.

• Temperature stress

• Pressure due to external loads

• Flexural stress

 

23. What are the materials used for constructing sewer pipes?

• Vitrified clay

• Asbestos cement

• Cement concrete

• Cast iron

 

24. Give some qualities of the good sewer pipes.

• Resistance to corrosion

• Resistance to abrasion

•  Strength and durability.

•  Light weight

•  Economy and cost

 

25. What are the tests conducted in sewer pipes after laying?

•  Test for leakage (water test)

•  Test for straightness of alignment and obstruction

 

26. Define sewer appurtenances.

Sewer appurtenances are those structures which are constructed at suitable interval along a sewerage system and help in its efficient operation and maintenance.

 

27. Mention the classification of manholes.

• Shallow manholes

• Normal manholes

• Deep manholes

 

28. What is meant by catch basins?

Catch basins are nothing but street inlets provided with additional small setting basins for avoiding the entry of the particles like grit, sand, debris in to the sewer pipes

 

29. Define inverted siphons

Inverted siphon is defined as the sewer section constructed lower than the adjacent sewer section and it runs full under gravity with pressure greater than the atmosphere

 

30. What are are the various methods of ventilation for sewers?

• Use of ventilating columns

• Use of ventilating manhole covers

• Proper design of sewers

• Use of mechanical devices

 

31. What are the different types of pumps used commonly for pumping the sewage?

• Centrifugal pump

• Reciprocating pump

• Pneumatic ejectors (or) Air pressure pumps

 

32. What is Small Bore Sewer?

The Small Bore Sewer is a watertight small diameter wastewater collection system that provides servicing with superior operational and environmental performance at a significantly lower cost as compared to historic gravity sewers

 

33. Write some Construction Benefits of Small Bore Sewer.

• Overall system is flexible, modular and adaptable.

• Shallow gradient piping installations eliminate need for heavy equipment - local manpower and hand tools can be used for trenching.

• Piping is not sensitive to curvilinear alignment, inflective gradients or sharp slope changes

 

34. Write some Environmental Benefits of Small Bore Sewer.

• 2 x reduction of greenhouse gases through methane capture when compared to equivalent carbon dioxide gas impact

• Conveyance of methane for reuse in electricity generation

• Sealed system means zero groundwater infiltration and zero sewage seepage

 

35. How to Test leakage in sewer pipes?

The ends of the sewer is plugged, the water is now filled in the manhole at the upper end and is allowed to flow through the sewer line. The depth of the water in the man hole is maintained to the testing head of about 1.5m. The sewer line is watched by moving along the trench.

 

36. How to Test straightness of alignment in sewer pipes?

The straightness of alignment in sewer pipes can be tested by placing a mirror at one end of the sewer line and lamp at the other end. If the pipe line is straight, the full circle of the light will be observed.

 

37. Explain One pipe system in sewerage?

The pipe of waste water from sinks, baths and wash basins and branches of soil pipes is connected to one main pipe. This main pipe is directly connected to sewerage system. Gulley (gutter) traps and waste pipes are completely distributed but all traps of water closets, basins, etc. are completely ventilated to preserve water seal.

 

38. Explain Two pipe systems in sewerage?

Soil and waste pipes are distinct and separate. The soil pipes are connected to sewer directly whereas waste pipes are connected through a trapped gulley (gutter). All traps of all appliances are completely ventilated.

 

39. What are the classifications of manhole?

• Shallow manhole

• Normal manhole

• Deep manhole

 

40. What are the component parts of Manhole?

• Access Shaft

• Working chamber

• The Benching (i.e) the bottom or invert portion of manhole

• The sidewalls

• Steps or ladders

• Cover and Frame