• High-strength anaerobic digester effluent was treated in three-stage filters. • Full-scale filters were constructed in Madagascar using all local materials. • Crushed charcoal trickling filters achieved nitrification rates up to 0.13 kgN m−3 d−1. • Bamboo woodchip filters achieved denitrification rates up to 0.03 kgN m−3 d−1. • Scrap iron filter removed 126 gP m−3 d−1 with 23.2 gP kg−1Fe capacity.