sewage ,Environmental engineering 2 ,unit 1

1. ENVIRONMENTAL
ENGINEERING II
UNIT I
SEWAGE QUALITY

2.  NECESSITY OF SANITATION
-Creates harmful bacteria
-Increase BOD
-Creates environmental hazard

3. IMPORTANT TERMS
 Sewer- pipes carrying waste water.
 Sewage- liquid waste originate from a community &
generally conveyed by sewer is called sewage.
 Sullage- waste water from kitchen, wash basin,
bathrooms etc.
 Effluent- an out flowing of water from natural water
body or from manmade structure.

4. TYPES OF SEWAGE
-Domestic sewage
-Industrial sewage
-Sanitary sewage (Domestic & Industrial sewage)
-Storm sewage
-Night soil

5.  COLLECTION OF SEWAGE
- Dry or conservancy system of collection
- Water carriage system of collection
- Dry or conservancy system of collection:-
- In this method, night soil in latrines removed manually &
transported in vehicles to point of disposal.

6.  Advantages
- Initial cost is low
- Total quantity of sewage carried to treatment unit is small.
 Disadvantages
- More unhygienic.
- Labour dependant.
- Difficult to provide side gutters in crowded lanes.

7.  Water carriage system
-night soil gets mixed with sufficient quantity of waste water
in this methods.
 Advantages
- Removal of sewage in covered conduits
- It ensure hygienic conditions.
- No labours are needed to carry out this type of unhealthy
works.

8.  Disadvantages
- High initial cost
- Need regular maintenance
- During monsoon, there is load on treatment and
during summer more water is required.

9.  SEWERAGE SYSTEM
1. The combined system
2. The separate system
3. The partially separate system
 SOURCES OF SEWAGE
-Industrial sources
-Domestic sources
-Public sources
-Ground water infiltration sources
- Storm water sources

10.  FLOW QUANTITY ESTIMATION
- It is essential to find out accurate estimate of the sewage
discharge for the hydraulic design of the sewers.
 VARIATION IN SEWAGE FLOW
POPULATION PEAK FACTOR
UPTO 20,000 3.5
20,000-50,000 2.5
50,000-75,000 2.3
GREATER THAN 75,000 2.0

11.  TYPES OF SEWER BASED ON MATERIAL
- Steel Sewer
- Cast- Iron Sewer
- Concrete Sewer
- Brick Sewer
- Stone Ware Sewer
- Plastic Sewer
- Asbestos cement Sewer

12.  TYPES OF SEWERS BASED ON SHAPE
- Circular Sewer
- Rectangular Sewer
- Semi elliptical Sewer
- Egg shaped Sewer
- Horse shoe Sewer
- U- shaped Sewer
- Parabolic Sewer

13.  DESIGN OF CIRCULAR SANITARY SEWERS
1. Chezy’s Formula
V = C√mi
2. Bazin’s formula
C = 157.6
1.81+ k
√m