- Waste water from industries is rarely pH neutral. It is therefore necessary to adjust the pH in the treatment process to make the wastewater pH neutral.
- This is particularly important if biological treatment is being used, as the microorganisms used in biological treatment require a pH in the range of 6-8 and will be killed by highly acidic or alkali wastewater.
Various chemicals used for pH control
- For acidic wastes (low pH) sodium hydroxide, sodium carbonate, calcium carbonate or calcium hydroxide, may be added among other things.
- For alkali wastes (high pH) sulphuric acid or hydrochloric acid may be added. Acids can cause corrosion of equipment and care must be taken in choosing which acid to use.
- Hydrocholoric acid is probably better from an environmental view point but can corrode stainless steel therefore plastic or appropriately coated pumps and pipes must be used.
CHEMICAL COAGULATION AND FLOCCULATION