CASPAR

Circular use of eco-friendly Adsorbents for Surface Water Purification and Agricultural P management

We face the increasingly urgent challenge of sustainable, environmentally friendly, and economically viable phosphorus (P) management—the most important nutrient for crop production. On the one hand, mineral phosphorus reserves are projected to be depleted within the next 50 to 200 years, making it necessary to use and recycle phosphorus more efficiently in agriculture. On the other hand, many water bodies worldwide are heavily polluted by excessive P inputs from surrounding croplands, leading to eutrophication and the degradation of aquatic ecosystems.

Although nature-based solutions for reducing diffuse phosphorus inputs are widespread (e.g., buffer strips), many of them are inefficient or are not well adopted in agricultural practice and are therefore often sparsely distributed and/or located in unfavorable sites (e.g., outside preferential runoff pathways). This necessitates additional technical measures for phosphorus reduction that

(1) can be applied before phosphorus-laden runoff enters water bodies or that can be introduced into water bodies already contaminated with phosphorus, and

(2) can be recycled and reused as phosphorus fertilizer.

P adsorption is the most efficient method for removing phosphorus from aqueous solutions. However, little is known about the potential for recovering and reusing adsorbents within a circular economy in agriculture, or about possible negative impacts on surrounding ecosystems, particularly under real-world conditions.

The application-oriented basic research project CASPAR aims to analyze the hydro-ecological requirements for the use and recycling of cost-effective, environmentally friendly P-adsorption materials in order to reduce P pollution in surface waters and replenish the P content of soils in the surrounding agricultural areas in Lower Austria.

The CASPAR project is funded by the State of Lower Austria as part of the Lower Austria RTI Strategy 2027 – RTI Projects: Basic Research 2025. Project partners are BAW Research (Lead), the Federal Office for Water Management, and the WasserCluster Lunz.