Question

Briefly describe the three stages of wastewater treatment.

Answer 1

Sewage treatment generally involves three stages, mainly are

PRIMARY 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 the wastewater.

SECONDARY TREATMENT:

Secondary treatment of wastewater makes use of oxidation to further purify wastewater. This can be done in one of three ways:

Biofiltration

This method of secondary treatment of wastewater employs sand filters, contact filters, or trickling filters to ensure that additional sediment is removed from wastewater. Of the three filters, trickling filters are typically the most effective for small-batch wastewater treatment.

Aeration

Aeration is a long, but effective process that entails mixing wastewater with a solution of microorganisms. The resulting mixture is then aerated for up to 30 hours at a time to ensure results.

Oxidation Ponds

Oxidation ponds are typically used in warmer places. In addition, this method utilizes natural bodies of water like lagoons. Wastewater is allowed to pass through this body for a period of time and is then retained for two to three weeks.

TERTIARY TREATMENT

This third and last step in the basic wastewater management system 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.

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