Bio-inspired Multilayer Drainage System for Agricultural Runoff Treatment

A bio-inspired multi-layer filter system using biochar and other substrates to treat agricultural runoff and subsurface drainage, developed by Alchemia-nova GmbH and BOKU within the EU-funded WaterAgri project (Horizon 2020, Grant Agreement No 858735). The system includes two configurations: the Drainagarden Filter with a 20 cm layer of Drainingarden® substrate (10% coarse zeolite), followed by 5 cm and 15 cm gravel layers; and the Soil Filter with a 40 cm layer of site-specific soil. Runoff is collected via a 30 m PVC pipe with a three-way distributor, and a south-facing PV island powers monitoring equipment. The system is designed for stable ground with concrete slabs and rammed feet spaced at 3 m intervals. Maintenance includes biweekly weeding and monthly inspection of wooden feet. Automated, gravity-driven operation minimises clogging risks. Monitoring tracks water outflow, soil moisture, temperature (2–30 cm depth), and effluent nutrients (PO4-P, NO3-N, NH3-N, pH, EC), with activation via a hydro switch during rainfall and deactivation after 12 hours of inactivity. Biochar with Mg(OH)₂ coating improves nitrogen and phosphorus retention, though initial phosphorus leaching may occur. Tracer tests show non-homogeneous flow. Fixed costs range from €686 to €764 per system, with operational costs for remote site visits and lab analyses. Benefits include nutrient recovery through biochar reuse as fertilizer, improved water retention, and climate resilience. Challenges include performance on slopes of 1–5%, where steeper gradients need further testing, and risk of storage overload during prolonged rainfall. Small-scale above-ground filters have low environmental impact, but larger installations may require environmental assessments. The project is funded by the European Union’s Horizon 2020 programme. Contact: eriona.canga@alchemia-nova.net, alchemia-nova GmbH, Vienna, Austria. Website: https://www.alchemia-nova.net/. The system supports sustainable agriculture by enhancing soil fertility and water management while reducing environmental impact.