Phosphorus Removal: What are the options?

Melissa Vanegas

Phosphorus is a key issue in the treatment of wastewater. While it has a crucial role, particularly in agriculture, the harmful effects of Phosphorus on the natural environment are well documented and understood. If excess quantities are discharged into rivers and water courses it can result in serious damage to the ecosystem.

 

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While the challenge of managing Phosphorus has increased as farming has intensified over recent decades, government estimates suggest that discharge from sewage treatment plants accounts for between 60 and 80% of the Phosphorus found in rivers. This is because unlike farming, which is seasonal, discharge from sewage treatment contributes to the Phosphorus levels all year round.For water companies, Phosphorus is a central focus for the next Asset Management Period (AMP7) up to 2025. While for many industrial applications, including dairy production, the Phosphorus levels in wastewater also need to be managed closely.

There are several approaches that can be taken to remove Phosphorus from wastewater, with the most common techniques being biological, chemical and filtration. For sites with large volumes, Phosphorus recovery and recycling can also be a financially viable option.


Biological

This approach grows microorganisms in the water, which can absorb and store Phosphorus as polyphosphate. The Phosphorus is incorporated into the biomass which is then separated from the treated water at the end of the process.


Chemical

This treatment uses a metal salt, most commonly iron, to precipitate ortho-phosphate. The precipitate forms as a solid and is removed in either a settlement tank or a tertiary solid capture process such as a disc or sand filter. Our Actiflo clarifier solution utilises microsand to ballast the chemical flocs, significantly increasing the settling velocity of the particles. This delivers very short retention times and a more compact design. In fact, the footprint of an Actiflo system is as much as 40 times smaller than conventional clarifier systems.


Filtration

The most common filtration technologies are disc, drum and sand filters. For many applications, disc filters, which utilise a fine media mesh mounted on a number of rotating discs, have several advantages. These units offer a space saving solution as they typically have a smaller footprint compared with other options as they allow the surface area of the filters to be maximised. This technology also offers a flexible and modular solution with a comparatively low TOTEX – the total expenditure combining CAPEX and OPEX.
Our Hydrotech DiscFilters provide a higher level of filtration for a smaller footprint than many standard drum or disc filters.


Recovery

In addition to simply removing the Phosphorus from wastewater it is possible to extract and recycle it. Phosphorus is a finite resource with no artificial substitute and many vital applications as an agricultural fertiliser and animal feed. Phosphorus recovery technology involves the production of struvite crystals (magnesium ammonium phosphate) by adding magnesium salts to wastewater. The struvite is then separated from the water ready to be reused – often in fertiliser production. This helps turn the cost of sludge disposal into revenue generated from the sale of the struvite. For sites with commercially viable volumes, our Struvia technology can significantly improve the return on investment while creating a circular economy in Phosphorus use.


 

To help you find the technologies and solutions that are most suitable
based on the specifics of your site and requirements
we have created a Phosphorus Removal Calculator.

Simply enter the flowrate and Phosphorus consent level to start and then add the approximate Influent Solids, the Influent Total P and available space to narrow down your options.

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Our expert team can help you find the water treatment solution that meets the needs of your site.

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