Being one of Sweden’s largest wetlands used for wastewater treatment, the Alhagen Wetland is an excellent place to study nature and biological processes. In grade six, pupils get to review the plant and animal life of the wetland. This instructor’s guide shows how to build on this experience and expand the understanding of the wetland for grade 9 pupils. The central topic of the field study is how nitrogen is transported through air, soil and water. This is to spur to a discussion on recycling, nitrification, denitrification and bio-indicators. The field study should also contribute to reaching the goals stated in the national curriculum (Lpo 94) for biology for grade nine pupils.