A)Physical constituents:-

Turbidity:-sewage is normally turbid,resembling dirty dish water and waste water from baths having material like piece of paper , cigarette ends, match stick, soaps, fruit skins,etc

Colour:It can be detected with naked eye it indicates freshness. If colour is yellowish, grey or light brown it is fresh sewage if black or brown dark it indicates septic sewage.

Odour:Fresh sewage is odourless but in 3-4 hours it becomes slate will oxygen present being exhausted then starts odour especially that of hydrogen sulphide gas.

Temperature:It has an effect on biological activity of bacteria present in sewage and also effect solubility of gases in sewage. Also temperature affects viscosity which directly affects sedimentation process.

B)Chemical constituents:

Total solids: sewage normally affects smell amount of solids in relation to huge quality of water (99.99%) and solids (0.1%) it may be in four forms suspended solids which remain floating in sewage colloidal solids are finely divided solids in sewage

pH value:pH value of sewage indicates hydrogen ion concentration present in sewage. It indicates the alkalinity of sewage. If pH <7 it indicates Sewage is acidic if pH> 7 it indicates alkaline.

CHEMICAL OXYGEN DEMAND:-(COD)

If organic compounds and their concentration are known the theoretical oxygen demand of waste water can be accurately calculated but it is impossible to know their details in any raw material.

The COD of raw water is therefore determining by performing a laboratory test on the given water with solution and theoretical computation of COD are only performed on water solution prepared with known amount of specific organic compound.

Biochemical oxygen demand(BOD):

The organic matter which biologically oxidised and which cannot be oxidised biologically is known as biologically active and biologically inactive. While testing we are mainly interested in finding out amount of biologically active organic matter present in it. Hence further testing is carried out to determine the BOD of sewage.

C)Biological constituents:

Large size bacteria:- it is known as B Butschiii. It is about 60 mm in length with 5mm diameter.

Algae:they are unicellular plants having chlorophyll. On the basis of the types of pigment they have been classified. The pigments help to receive the radiant energy. The process is known as photosynthesis which allows the algae to absorb the carbon dioxide and to release oxygen.