Nutrient removal from human fecal sludge digestate in full-scale biological filters

• Published in: Chemosphere (Oxford) Vol. 257; p. 127219
• Main Authors: Forbis-Stokes, Aaron A., Miller, Graham H., Segretain, Armel, Rabarison, Felahasina, Andriambololona, Tojoniaina, Deshusses, Marc A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2020; Elsevier Science Ltd
• Subjects: Anaerobic filter; Denitrification; Effluent polishing; Field study; Nitrification; Trickling filter; Denitrification; Effluent polishing; Trickling filter; Anaerobic filter; Nitrification; Field study
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.127219

There is a great need for simple methods for digestate management for potential household sanitation systems based on anaerobic digestion of minimally diluted fecal waste in countries that lack safe sanitation. Herein, a full-scale three-stage filter for nitrogen and phosphorus removal from anaerobic digester effluent was implemented in Madagascar. It included a trickling filter with crushed charcoal (for aerobic nitrification), a submerged anaerobic filter with bamboo chips (for denitrification), and a submerged filter with scrap iron (for phosphorus removal). All filter materials were sourced locally. Three parallel replicate systems were operated in two sequential 8-week phases for a total of 16 continuous weeks. Though the influent feed was not as expected, with much of nitrogen in the feed coming in as organic N and not as NH3–N, the filters still removed 38–49% of total incoming nitrogen. The filters achieved high rates of nitrogen transformation along with removing solids (73–82% turbidity removal), chemical oxygen demand (67–75% removal), and phosphorus (31–50% removal). Overall, the reaction rates from this full-scale study were in line with previous lab-scale investigations with scaled-down systems, supporting their application in real-world scenarios. Based on this study, simple effluent filters can support nutrient removal for small-scale and onsite fecal sludge treatment systems. [Display omitted] •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.