There are three types of operations and processers
- Physical unit operation
- Chemical unit processes
- Biological unit processes
- Physical unit operations
The physical unit’s operations in which application of physical forces predominate consist of the following
- Screening
- Comminution
- Flow equalization
- Mixing
- Flocculation
- Sedimentation
- Floatation
- Elutriation
- Vacuum filtration
- Microscreening
- Air drying
Chemical unit processers
Chemical unit processer is those in which removal of contaminators is brought about by chemical activity. In the field of wastewater treatment, chemical unit operations are usually used in conjunction with physical unit operations and biological unit processer
The following chemical unit processer are commonly used for wastewater treatment
- Chemical precipitation
- Gas transfer
- Adsorption
- Disinfection
- Combustion
- Ion exchange
- Electrodialysis
It should be clearly noted that chemical unit processes are additive processes whereas physical unit operations and biological unit processes are subtractive processes.
Biological unit processes
Biological unit processes are there in which removal of contaminants is brought about by biological activity. In the biological treatment of wastewater, the objectives are to coagulate and remove the non-settleable colloidal solids and to stabilize the organic matter.
Biological unit processers may be classified in the following heads
Aerobic processes
Aerobic processes are biological treatment processes that occur in the presence of dissolved oxygen are known as obligate aerobes the aerobic. The aerobic processes include the following.
- Activated sludge process
- Tricking filters
- Aerobic stabilization ponds
- Aerated lagoons
- Anaerobic processes
Anaerobic waste treatment involves the decomposition of organic and \ or inorganic matter in absence of molecular oxygen. Anaerobic processes consist of the following.
- Anaerobic sludge digestion
- Anaerobic contact processer
- Anaerobic filters
- Anaerobic lagoons or ponds