Drying characteristics of faecal sludge from different on-site sanitation facilities. (1st May 2020)

• Record Type: Journal Article
• Authors: Getahun, Samuel; Septien, Santiago; Mata, Jaime; Somorin, Tosin; Mabbett, Ian; Buckley, Christopher
• Is Part Of: Journal of environmental management. Volume 261(2020)
• Publication Date: 2020-05-01
• Subjects: Drying -- Faecal sludge -- Valorisation -- Temperature -- Heat of drying -- Calorific value; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2020.110267
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Drying is one of the treatment techniques used for the dual purpose of safe disposal and energy recovery of faecal sludge (FS). Limited data are available regarding the FS drying process. In this paper the drying properties of FS were investigated using samples from ventilated improved pit (VIP) latrines and urine diversion dry toilets (UDDT) and an anaerobic baffle reactor (ABR) from a decentralized wastewater treatment systems. Moisture content, total solids content, volatile solids content, water activity, coupled thermogravimetry & differential thermal analysis (TGA-DTA) and calorific value tests were used to characterize FS drying. Drying kinetics and water activity measured at different moisture content during drying (100 °C) were similar for the samples from different on-site sanitation facilities. Experimental heat of drying results revealed that FS requires two to three times that of the latent heat of vaporization of water for drying. Drying temperature was more significant than the sludge source in determining the final volatile solids content of the dried samples. This was reinforced by the dynamic TGA that showed considerable thermal degradation (2–11% dry solid mass) near 200 °C. Below 200 C, the calorific value of the dried samples exhibited no significant difference. The average calorific values of VIP, UDDT and ABR samples at 100 °C were 14.78, 15.70, 17.26 MJ/kg dry solid, respectively. This suggests that the fuel value of FS from the aforementioned sanitation facilities will not be significantly affected by drying temperature below 200 °C. Based on this study, the most suitable temperature for drying of FS for a solid fuel application was found to be 150 °C. Highlights: Poorly managed faecal sludge has a direct impact on the environment and human health. Thermal drying characteristics of faecal sludge from different onsite sanitation facilities was studied. The source of the faecal sludge samples had little effect on drying kinetics. Temperature was the critical parameter that affected the volatile solids content and calorific value of the dried material. Suitable temperature to disinfect and dry faecal sludge for a solid fuel use was identified.