Correct Answer - Option 4 : 1, 2 and 3
There are three distinct steps involved in traditional wastewater treatment methods.
Primary wastewater treatment:
- Primary treatment of wastewater involves sedimentation of solid waste within the water. This is done after filtering out larger contaminants within the water.
- Wastewater is passed through several tanks and filters that separate water from contaminants.
- The resulting sludge is then fed into a digester, in which further processing takes place.
- This primary batch of sludge contains nearly 50% of suspended solids within wastewater.
Secondary wastewater treatment:
Secondary treatment of wastewater makes use of oxidation to further purify wastewater. This can be done in one of three ways:
- Biofiltration
- Aeration
- Oxidation ponds
Tertiary wastewater treatment:
- It is mostly comprised of removing phosphates and nitrates from the water supply.
- Substances like activates carbon and sand are among the most commonly used materials that assist in this process.
- Several methods have been applied for final treatment, such as adsorption using activated carbon or other appropriate sorbents, post precipitation, ion-exchange, reverse osmosis, electrochemical treatment, and evaporation.