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

• Large amount of fine suspended matters make the water to appear cloudy or turbid in appearance. Turbidity depends upon the fineness an concentration of particles present in water.
• Turbidity is measured on standard silica scale.
• Turbidity is the measure of extent to which light is either absorbed or scattered by suspended material in water.
• Turbidity of water for domestic use should not exceed 10 ppm on a silica scale.

Oxidation ditch– It is a modified form of extended aeration of activated sludge process. Oval in shape with two surface rotors placed across the channel. It has maximum efficiency of BOD removal is achieved in oxidation ditch.

Pyrolysis method can be employed for plastic and rubber waste disposal. Pyrolysis–
Upon heating in an oxygen free atmosphere, most of the organic substances can be split through a combination of thermal cracking and condensation reactions into gaseous, liquid and solid fractions. This process is known as pyrolysis or thermal pyrolysis.
• This process is also known as destructive distillation.

A trickling filter is a fixed bed biological filter that operates under (mostly) aerobic conditions. It removes dissolved organic matter.
• This filter consists of 2 m to 3 m deep circular bed of packed granular stone or gravel about 50 to 70 mm in size.
• A trickling filter is designed to remove dissolved organic matter from wastewater.

Given,
BOD of town = 25000 kg/day
Per capita BOD = 50 kg/day

The entry of foul-smelling gases into the house coming from the sewers can be prevented by providing water seals for all the fixtures and vent pipe in the plumbing system. Vent pipe is fitted into the soil pipe to protect water scale against siphonage and backflow.

P-trap–The trap used for a water closet. It is used in toilets and underneath sinks.

Gully grap–It is basin in the ground that receives piped wastewater from your house before it enters the underground water.

Imhoff tank– The two chambers are otherwise unconnected, with sewage flowing only through the upper sedimentation chamber and no flow of sewage in the lower digestion chamber.

• It is a robust and effective settler that causes a suspended solids reduction of 50 to 70%, COD reduction of 25 to 50% and leads of potentially good sludge stabilization.

• In imhoff tank, both sedimentation and digestion processes of sludge take place simultaneously.

High COD to BOD ratio of an organic pollutant represents low biodegradability of the pollutant.

• A high BOD/COD ratio should be considered sufficient condition to ensure biodegradation.

• This ratio is commonly used as indicator the degree of biodegradation of the waste water.

In contrast to alkaline water, which has pH greater than 7, acidic water has a pH of 6.5 or less.
• Water has a neutral pH of 7.