Environmental Engineering (General Engineering) (SSC JE)

A condition of sudden permanent aural damage resulting from an intense short term exposure of noise is called acoustic trauma.

Permanent threshold shift–It is also known as permanent hearing loss. It usually progresses constantly as noise exposure continues month after month and year after year.

Nitrogen (NOx) and sulphur (SOx) oxides, the major gaseous pollutants emitted from fossil fuel combustion, have significant health and environmental, we observed reductions in emissions of SOx and NOx of 70-72% and 28-30% respectively.

The thickness of the ozone layer varies worldwide and it is generally lower near the equator and highest the poles. The highest amounts of ozone layer occur in the stratosphere.

In the upper stratosphere, it forms a protective shield against solar ultraviolet radiation, but near the ground, its a pollutant that can cause respiratory ailments in humans and animals.

Design period of unit–

According to noise pollution rules, 2000-

Normally, the pH of rain water is 5.6 because of the presence of H⁺ ions produced due to the dissolution of CO₂ in rain water from the atmosphere when the pH of rain water drops from 5.6, it is called acid rain and it is due to the presence of oxide of sulphur and nitrogen in the atmosphere.

Colour– It is caused by suspended and dissolved matter in water.
• Measurement of colour is done by colour matching technique (tintometer)
• Result is expressed in TCU or hazen unit where 1 TCU is equal to colour produced by 1 mg per litre of platinum in the form of chloroplatinate ion.
• The colour testing is done within 72 hours of collection as otherwise biological.
• Acceptable limit is 5 TCU and cause for rejection is 15 TCU (As per IS 10500-2012)

According to WHO 1984 and Indian standard drinking water specification 1991 the maximum permissible limit of fluoride in drinking water is 1.5 ppm and highest desirable limit is 1.0 ppm.

Fluoride concentrations above 1.5 ppm in drinking water cause dental fluorosis and much higher concentration skeletal fluorosis low concentration provides protection against dental cavities.

• If fluoride < 1 mg/litre, it causes dental cavities
• If fluoride > 1.5 mg/litre, it causes dental fluorosis or melting of teeth.

Filtration–Impurities remains in water after sedimentation, coagulation & flocculation are removed by passing it through filtration bed. It is a technique used to remove ultra fine particles by passing the water through the beds of granular materials known as filters is the filtration.