Environmental Engineering (Part-3) (General Engineering) (SSC JE)

The end product of anerobic decomposition are comparatively unstable and include acid alcohol and gases (mainly methane).

The self-purification process of water bodies or processes involving biological, chemical and physical processes working simultaneously on biological pollutants oxidicing them and increasing the amount of dissolved oxygen.

• When bleaching powder added to water its leads to forman of sludge hence it is not suitable treatment in plant but can be used for swimming pool.
• Bleaching powder also increase pH of water when it added in water.

Chlorine is a strong oxidizing disinfectant that has been used to treat polluted water, it is not responsible for water pollution.

Turbidity–Turbidity is the measure of relative clarity of a water.

Temperature–Water's temperature include odours, chemical, reactions, solubility and viscosity, biological oxygen demand, sedimentation and chlorination depends on the waters temperature.

Cloudy nights are warmer to clear cloudless nights, because clouds reflect back radiations to earth at night cloud cover has the opposite effect.

• If skies are clear, heat emitted from the earth's surface freely escapes into space, resulting in colder temperatures.

• If clouds are present, some of the heat emitted from the earth's surface is trapped by the clouds and remitted back towards the earth.

Sea breeze is occurred during day time by the phenomena of convection. The strength of sea breeze is directly proportional to the temperature difference between land and sea.

Convection–It is the process of heat transfer in fluids by the actual motion of matter.
Conduction–It is a process where heat flows from hotter end to colder end in solids.

Coagulation and sedimentation treatment unit was adopted for removal of turbidity, natural organic matter and color.

Following types of coagulant is used in turbidity removal–
(i) Aluminium sulphate or Alum
(ii) Sodium aluminate
(iii) Ferrous sulphate
(iv) Ferric sulphate
Note–Alum is the most commonly used coagulant.

Chlorination is a process used for water purification during water purification chlorine (Cl₂) solution is used for killing the bacteria or disinfection action. Disinfection action of chlorine is mainly due to the formation of hypochlorous acid when chlorine is added to water.
Forms of application of chlorine–
(i) Bleaching powder–Treatment of water with bleaching powder [Ca(Cl)₂] is known as hypochlorination.
(ii) Chloramines
(iii) Free chlorine gas
(iv) Chlorine dioxide

Biochemical oxygen demand (BOD) is a measure of organic pollution of water. BOD is higher in polluted sewage water and is connected with microbes and organic matter.
When the demand for oxygen will be high due to all bacteria, so the BOD level will be high.

Chemical Oxygen Demand (COD)–COD is used to measure the quantity pollution in water after waste water treatment. The higher value of COD indicates the higher organic pollution in the water sample, only chemically digestible matter can be determined by the COD test.

The national ambient air quality standards in India were first notified in 1994 under the Environment (Protection) Rules, 1986
• As per CPCB : Indian National Air Quality Standards permissible value for PMₗ₀ is 100 µg/m³ for average 24 h value.