Citizen science to promote a nature-based solution: barriers and lessons learned from a vegetated vermifilter...

Nature-based solutions (NBSs) offer environmentally rational, socially acceptable, and economically viable alternatives for solving diverse water issues. Therefore, the involvement of local communities is crucial, as their participation in developing shared knowledgewithin their territories is essential for building and sustaining resilient ecosystems. This study highlights a co-created, nature-based initiative that led to the construction of a vegetated vermifilter for greywater reuse and monitoring in a small community at the Nonguén School Community, located in the Biobío region, central Chile. The project was initiated in 2019, but not completed until 2022 due to the COVID-19 pandemic. The vermifilter was based on green filters and was used to recover white greywater (dishwater and handwash water) for irrigation use. The circular biofilter, built by the community and directly connected to the kitchen, consisted of four distinct layers: rock, sand, topsoil, and sawdust. It also included populations of earthworms and wetland plants, all primarily collected by the community. Water analysis (i.e., pH, temperature, BOD₅, TSS, nitrate, phosphate, turbidity, dissolved oxygen, and total and fecal coliforms) demonstrated a moderate effectiveness during a measured period in 2022. We highlight and discuss the fundamental role of the participation of the local community in the whole co-work process and key lessons and barriers to further optimize a vermifilter design.