What Are the Three Stages of Wastewater Treatment?

There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment. In some applications, more advanced treatment is required, known as quaternary water treatment. This stage deals with part per million to part per billion levels of contamination and often involves oxidation or fine filtration processes. Each of these stages tackles different pollutants, with water becoming cleaner as it moves through the phases.

Different treatment stages or combinations are adopted dependent on the original quality of the water and its intended final use.

What is primary wastewater treatment?

During primary treatment, wastewater is temporarily held in a settling tank where heavier solids sink to the bottom while lighter solids float to the surface.

Once settled, these materials are held back while the remaining liquid is discharged or moved through to the more rigorous secondary phase of wastewater treatment.

These large tanks are also often equipped with mechanical scrapers that continually drive collected sludge in the base of the tank to a hopper which pumps it to sludge treatment facilities.

What is secondary wastewater treatment?

Secondary treatment of wastewater works on a deeper level than primary and is designed to substantially degrade the biological content of the waste through aerobic biological processes. It is done in one of three ways:

Biofiltration

Biofiltration uses sand filters, contact filters or trickling filters to ensure that any additional sediment is removed from the wastewater.

Aeration

Aeration is a lengthy process which increases oxygen saturation by introducing air to wastewater. Typically, the aeration process can last for up to 30 hours, but it is very effective.

Oxidation ponds

Typically used in warmer climates, this method utilises natural bodies of water such as lagoons, allowing wastewater to pass through for a set period before being retained for two to three weeks.

Completing secondary wastewater treatment allows for safer release into the local environment, reducing common biodegradable contaminants down to safe levels.

What is tertiary wastewater treatment?

The aim of tertiary wastewater treatment is to raise the quality of the water to domestic and industrial standards, or to meet specific requirements around the safe discharge of water. In the case of water treated by municipalities, tertiary treatment also involves the removal of pathogens, which ensures that water is safe for drinking purposes.

At Arvia Technology, we specialise in industrial tertiary and quaternary wastewater treatment, with our specialist solution targeting the hardest-to-treat contaminants to ensure regulations are met for safe discharge or reuse of water.

We work across a range of industries, including: pharmaceuticalchemicaloil and gasfood and beverage, and utilities. The Nyex™ systems can be used as a standalone treatment or be bolted on to an existing treatment train to provide more advanced, targeted treatment where required.

To discuss your company’s treatment challenges and arrange a treatability trial on your wastewater, contact our team today.

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What’s in your wastewater?
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