Environmental Engineering (Part-5) (General Engineering) (SSC JE)

The minimum level of dissolved oxygen required for survival of aquatic life is 4.0 PPM (mg/L). Dissolved oxygen is measured by Wrinkler method.

Trickling filter–An aerobic attached growth system consists of 2-3 m depth packed with granular stone or gravel on circular bed. It is also called as biofilter.
Types of Trickling filter–

1. Standard rate trickling filter
OLR – (0.08 – 0.32) kg/m³/day

2. High rate trickling filter
OLR – (0.32 – 1) kg/m³/day
Where, OLR = Organic loading

The level of residual chlor water should be (0.2–0.5) ppm so that will be 0.2 PPM.
• The amount of residual chlorine left in provides safety against pathogenic bacteria.

The length of 1st compar compartment septic tank should be ½ of t septic tank.

Septic tank–A primary sedimentation tank or sludge digestion tank base on anaerobic decomposition.
Design parameters-
• Length/Width = 2-4
• Depth = (1-1.3) m without freeboard.
• Detention period = 24 hours

Imhoff cone–A conical glass vessal having capacity of 1 liter is used to determine the quantity of settleable solid present in sewages.

Incremental increase method (or method of varying increment). It is considered to best method for any city whether old or new.
• Incremental increase method is the combination of arithmetic average method and geometrical average method.

As stated earlier an open well is essentially of a bigger diameter than that of tube well and derives its water only from one previous stratum.
• Tube well is general may derive water from more than one depth than an open well.
• The economically feasible depth of an open well is limited to 30 meters below the ground surface. In a lined open well the entry of water is from the bottom and not from the sides.

An open well is classified as–
1. Shallow well, 2. Deep well.

In India it is essential to have adequate water supply for five fighting to avoid loss of life and property. As per the national building code of India a provision of 1.0 litres per head per day is considered sufficient for firefighting in Indian condition.
• Rate of fire demand is sometime treated as function of population and is worked out on the basis of empirical formulas.

Water impurities are classified as physical, chemical and biological impurities physical water quality parameter are–
1. Suspended solids
2. Turbidity
3. Colour
4. Taste and odour
5. Temperature
Chemical water quality parameter are–
1. Total dissolved solids (TDS)
2. Alkalinity
3. pH
4. Hardness
5. Chloride content
6. Nitrogen content
7. Flourides 8. Metals
9. Dissolved gas
Biological water quality parameters– Bacteria colli (B-coli) or Escherichia coli (E–coli) test.
The tests for coliforms are–
(a) membrance filter technique
(b) MPN test (most probable number)
(c) Coliform index.