title: Locally produced natural conditioners for dewatering of faecal sludge.
abstract: In urban areas of low-income countries, treatment of faecal sludge (FS) is insufficient or non-existent. This results in large amounts of FS being dumped into the environment. Existing treatment technologies for FS, such as settling-thickening tanks and drying beds, are land intensive which is limiting in urban areas. Enhanced settling and dewatering by conditioning was evaluated in order to reduce the treatment footprint (or increase treatment capacity). Conventional wastewater conditioners, such as commercially available lime and polymers, are expensive, and commonly rely on complex supply chains for use in low-income countries. Therefore, the treatment performance of five conditioners which could be produced locally was evaluated: Moringa oleifera seeds and press cake, Jatropha curcas seeds, Jatropha Calotropis leaves and chitosan. M. oleifera seeds and press cake, and chitosan improved settling and dewatering and had a similar performance compared to lime and polymers. Optimal dosages were 400-500 kg M. oleifera/t TS, 300-800 kg lime/t TS and 25-50 kg polymer solution/t TS. In comparison, chitosan required 1.5-3.75 kg/t TS. These dosages are comparable to those recommended for wastewater (sludge). The results indicate that conditioning of FS can reduce total suspended solids (TSS) in the effluent of settling-thickening tanks by 22-81% and reduce dewatering time with drying beds by 59-97%. This means that the area of drying beds could be reduced by 59-97% with end-use as soil conditioner, or 9-26% as solid fuel. Least expensive options and availability will depend on the local context. In Dakar, Senegal, chitosan produced from shrimp waste appears to be most promising.
authors.affiliation: a Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland.
authors.forename: Moritz
authors.initials: M
authors.lastname: Gold
authors.affiliation: b ETH Zürich, Institute of Environmental Engineering , Zürich , Switzerland.
authors.forename: Pauline
authors.initials: P
authors.lastname: Dayer
authors.affiliation: c Faculty of Medicine, Pharmacy and Odontology, Department of Pharmacy , Cheikh Anta Diop University of Dakar , Dakar-Fann , Senegal.
authors.forename: Marie Christine Amie Sene
authors.initials: MC
authors.lastname: Faye
authors.affiliation: d Department of Water Engineering , Polytech Nice-Sophia , Sophia Antipolis , France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Clair
authors.affiliation: e Faculty of Sciences and Technics , Institute of Environmental Sciences (ISE), Cheikh Anta Diop University of Dakar , Dakar-Fann , Senegal.
authors.forename: Alsane
authors.initials: A
authors.lastname: Seck
authors.affiliation: f Laboratory of Wastewater Treatment , Fundamental Institute of Black Africa (IFAN), Cheikh Anta Diop University of Dakar , Dakar-Fann , Senegal.
authors.forename: Seydou
authors.initials: S
authors.lastname: Niang
authors.affiliation: a Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland.|b ETH Zürich, Institute of Environmental Engineering , Zürich , Switzerland.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Morgenroth
authors.affiliation: a Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland.
authors.forename: Linda
authors.initials: L
authors.lastname: Strande
mesh_terms: D003906:Developing Countries; D005427:Flocculation; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Sanitation; chitosan; coagulation; developing country; dewatering