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Implementing Circular Economy for Nutrient Recovery in Urban Wastewater Treatment Plants

Murcia’s LIFE ENRICH project implements a circular economy approach in wastewater treatment. It serves as a bridge between plant operators and the fertilizer industry, by transforming nutrients present in wastewater into fertilizers. The project addresses environmental challenges and validates the efficacy of these alternative fertilizers through crop trials.


LIFE ENRICH is a European project funded under the Life programme. The goal of the LIFE ENRICH project is to implement the concept of circular economy, by demonstrating the complete value chain for nutrient recovery in urban wastewater treatment plants (WWTPs). This includes the re-use of these nutrients to produce valuable fertilizers. The project lasted from September 2017 until November 2021.

In modern society, the wastewater treatment and agricultural sectors operate independently of one another. WWTPdischarge nutrients into the environment through rivers, dewatered sludge, and the atmosphere – whilst the fertilizer industry consumes significant amounts of nutrients from natural reserves or complex manufacturing processes. These disconnected processes need to change and LIFE ENRICH has successfully demonstrated the possibility of establishing beneficial synergies between these sectors for the industry, environment, and society.

Description of plan

LIFE ENRICH focuses on the whole value chain, including the recovery of nutrients from WWTPs, the characterisation and optimal blending of these nutrients to create high-value fertilizers, and the validation of their performance in a real-life case study with end-users.

The project primarily concentrates on the recovery of nitrogen (N) and phosphorus (P) from WWTPs. These recovered nutrients are then transformed into alternative fertilizers, struvite and ammonium salts. These fertilizers were utilized in crop trials to assess their effectiveness. To carry out the project, the Murcia Este WWTP was selected as the facility to operate the technological prototypes.

The performance and efficiency of the nutrient recovery process were evaluated in a real-world setting, as horticultural and extensive crops were cultivated in Spanish territories, specifically in Cabrils, Agramunt, and Castelldans soils. These locations served as test sites to validate the effectiveness of the alternative fertilizers and sewage sludge in supporting crop growth.

The LIFE ENRICH project aims to demonstrate the feasibility and efficacy of nutrient recovery from WWTP, the production of high-value fertilizers, and their successful utilisation in crop cultivation.


An overarching challenge is the increasing scarcity of phosphorus as a resource globally. Phosphorus is primarily used in the food supply, with more than 80% of the mined product serving the food industry. As living standards rise and the global population continues to grow, the demand for phosphorus is expected to increase.  At the same time, the reserves of phosphorus are depleting. Initiatives such as the LIFE Enrich project are now underway to alleviate its scarcity, by focusing on reuse and recovery within the phosphorus cycle.

During the LIFE Enrich project some difficulties were encountered in the production processes. For example, producing ammonia salts (an alternative fertilizer)  was difficult, because the WWTP  could only be utilised for limited periods due to high energy costs. Additionally, to achieve the required level of purity (a clean product) an extra component had to be added in the production process. This led to higher costs, reducing overall returns. Consequently, establishing the feasibility of the business model was sometimes challenging.


The project consortium was formed by 7 partners:

  • Cetaqua, Water Technology Centre (project coordinator),
  • Suez Advanced Solutions,
  • Aigües del Segarra Garrigues,
  • Aguas de Murcia (EMUASA),
  • Instituto de Investigación y Tecnología Agroalimentaria (IRTA),
  • Universitat Politècnica de Catalunya (UPC),
  • Universitat Politècnica de València (UPV).

Each of the partners contributed to the project by sharing their knowledge and expertise and applying this to the circular model.

Achievements and benefits

Operational:  The process implemented by the Murcia Este WWTP is to recover nitrogen and phosphorus from wastewater, transforming them into valuable fertilizer offers several benefits for the WWTP:

  1. The WWTP’s adaptation enhances the efficiency of water removal from the sludge, resulting in reduced chemical and energy consumption during the dewatering stage.
  2. The recovery of nitrogen, along with struvite, reduces the nitrogen load in the biological treatment, leading to a lower energy demand.
  3. The recovery of phosphorus leads to an 85% reduction in the need for antiscaling agents (detergents) to clean the installation.

Additionally, a technical replicability study conducted on three other WWTPs demonstrated that the LIFE ENRICH process is flexible and can be adapted to different WWTP configurations.

Economic and social: The implementation of the LIFE ENRICH value chain reduces the operating expenditures and could create additional jobs. This initiative promotes broader knowledge and the adoption of circular and environmentally friendly strategies. Moreover, nutrient recovery could boost the European agriculture industry by reducing its reliance on mineral fertilizers and their price fluctuations.

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