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Taking Phosphorus Removal to the Next Level

The importance of protecting our environment has never been more widely acknowledged and has further been thrust into the spotlight during COP26. Here, Simon Radford, UK Sales Manager, Evoqua Water Technologies, looks at the innovative way wastewater treatment plants can improve their sustainability and support the circular economy through nutrient recovery.

For wastewater treatment plants, sustainability can be crucial in meeting regulatory requirements, managing operating costs and, in some cases, meeting corporate social responsibility goals. For water companies looking for new or enhanced ways to support the circular economy, phosphorus may just hold the answer.

Phosphorus removal is essential to meet effluent limits and protect the environment – the agreed technically achievable phosphorus limits (TAL) for the UK are set at 0.25mgP/l for AMP7[1]. Now there’s an innovative way to help meet strict phosphorus limits and turn the nutrient into a valuable fertiliser which helps lower a plant’s environmental footprint, support the circular economy, improve water quality and provide a steady revenue stream.

How it Works

Phosphorus is recovered from municipal or industrial waste streams with Ostara’s Pearl® system by Evoqua Water Technologies and transformed into eco-friendly granules, which are harvested, dried and then distributed and sold by Ostara Nutrient Recover Solutions as Crystal Green® Fertiliser. This cost-effective nutrient recovery solution converts wastewater treatment plants into true resource recovery facilities.

Crystal Green® Fertiliser targets the root of  crops and relies on acidity from the root to dissolve, thus maximising its impact as a fertiliser and the absorption of phosphorus,while also preventing run-off or leaching from agricultural operations. This sustainable solution is made up of Ostara’s Pearl® system and WASSTRIP® system, offered by Evoqua Water Technologies.   

The technology works for plants with biological nutrient removal (BNR). The Pearl® system, a fluidised bed reactor sits at the heart of the solution and recovers up to 50% of total plant influent phosphorus, before it accumulates as struvite. Through adding magnesium in a controlled pH setting, nutrients crystallise into highly pure fertiliser granules. Once they reach the size required for standard fertiliser blends, they are harvested, dried and then distributed and sold by Ostara as Crystal Green® fertilizer.  

Ostara’s WASSTRIP® system complements the Pearl system by releasing phosphorus before it reaches the anaerobic digester, sending it directly to the Pearl system. By diverting phosphorus from the sludge stream, the WASSTRIP system reduces digester struvite and maximises phosphorus available for recovery. within the Pearl reactor.

Reaping the Benefits

The environmental benefits of nutrient recovery are clear. Removing phosphorus helps water companies meet regulatory requirements, protects local waterways from nutrient pollution, and supports the circular economy.

While sustainability is the key benefit here, it isn’t the only one and that’s what makes nutrient recovery a popular choice. Removing phosphorus from the water prevents struvite formation in pipes, pumps, and digesters, which mitigates the need to use expensive chemicals to treat it and therefore decreases sludge production. Furthermore, producing a high value fertiliser provides a steady revenue stream through its sale.

Evoqua has entered into an exclusive agreement with Ostara Nutrient Recovery Technologies Inc. to lead sales of the unique nutrient recovery solution in North America and Western Europe. It’s the perfect fit for our business, as now we can go one step further beyond supporting wastewater plants with removing nutrients and now help them recycle them too.

Working closely with our customers to help them create more sustainable futures for their business and our planet is key and it’s vital that we do this while improving operational and cost efficiencies.


[1] Environment Agency, Phosphorus and Freshwater Eutrophication Pressure Narrative. UK, October 2019

Pearl, Crystal Green and WASSTRIP are trademarks of Ostara Nutrient Recovery Technologies Inc. used under license. 

Connect with Simon Radford on LinkedIn.