Water quality differs geographically. Many types of chemicals are available.

Coagulants – Coagulants are generally positive ions with high valence which are used for charge neutralization of suspended solids. Aluminium salt and iron salts are generally used for this purpose. Aluminium sulphate (Al₂SO₄)^3-[Alum] and ferric chloride FeCl 3 are used as coagulants. Coagulation depends upon the dose, pH and colloid concentration.

Flocculants – Flocculants are used to form flocs in water that contains suspended solids. Generally, the charge on the suspended solids is weakened by the coagulants which are followed by formation of flocs by flocculants. Polymers are of cationic, anionic and polyampholytes (both charges) types.

Disinfectants – These are the chemicals used to disinfect the treated wastewater for any contamination. They have a residual concentration in the treated wastewater so as to check any further contamination. Chlorine is mostly used as disinfectants and it can be used in many forms viz. liquid, powder and gas. These are easily available in the market and are cheaper compared to other disinfectants. Other disinfectants used are ozone, chloramines, sodium hypochlorite.