Environmental Engineering (Part-4) (General Engineering) (SSC JE)

In plumbing a trap is a device shaped with a bending pipe oath to the retain fluid to prevent sewer gases from entering building while allowing waste materials to pass through.
• The following types of trap used in plumbing system. Example–p-type, a-type, s-type, u-type, and j-type.

• Iron is found on earth mainly as insoluble ferric oxide.
• Iron can impart level taste to the water, causes discoloration in clothes and incrustations in water mains.
• It is responsible to hardness of water.
• It is responsible for red colour.
• Presence of iron oxide does not cause toxic effect in water.

Colour of water is expressed in number of a platinum cobalt scale.
Instrument   Tintometer
Acceptable limit   5 TCU
Cause for rejection   15 TCU
Where, TCU – True colour unit

Welded steel pipes–Most suitable for main laid on bridges.

Cement concrete pipe–Generally used to carry waste water.

Wrought iron pipe–Mostly used to carry water, gas or certain other liquid from one place to another.

For community water systems that add fluoride to their water, public health service recommends a fluoride concentration of 0.7 mg/l to 1 mg/l maintain carries prevention benefits and reduce the risk of dental fluorisis.
Acceptable limit – 1 mg/l
Cause for rejection – 1.5 mg/l

The most commonly used sewer under culvert is circular sewer.
• The perimeter of circular sewer is the least w.r.t. the sewer of other shape.
• The circular sewers are easy to construct.
• Cost of construction is low.
• The inner surface is smooth hence the flow of sewage is uniform and there is no chance of deposition of suspended particles.

The disinfection efficiency of chlorine in water treatment is influenced by the pH value of the water. The disinfection efficiency of chlorine is reduced by increased pH values. This is because the efficacy of chlorine is dependent on the formation of hypochlorones acid (HOCl) and hypochlorite ion (OCl⁻) in water.