Critical analytical parameters for faecal sludge characterisation informing the application of thermal treatment processes

Title: Critical analytical parameters for faecal sludge characterisation informing the application of thermal treatment processes
Authors: Krueger, BC
Fowler, GD
Templeton, MR
Item Type: Journal Article
Abstract: Thermal processes for the treatment of faecal sludge such as pyrolysis or combustion offer complete destruction of pathogens, whilst allowing for energy and nutrient recovery. The development of such processes is currently constrained by a lack of knowledge on thermally relevant faecal sludge characteristics. This study investigated thirty faecal sludge samples from three sanitation technologies (ventilated improved pit latrines (VIP), urine diverting dry toilets (UD), septic tanks (ST)) and compared these by non-parametric statistical analysis. A focus was placed on parameters necessary for thermal process development and recoverable nutrient concentrations. The relevant characteristics ranged widely within technology groups. Calorific values and ash concentrations of 2.1–25.7 MJ/kg and 9.5–88.4% were observed for STs, of 9.2–13.9 MJ/kg and 40.9–61.5% for VIPs and of 3.9–18.1 MJ/kg and 18.8–81.3% for UDs. These two parameters show a strong linear inverse correlation and determine the minimum dewatering requirements from which a net energy recovery may be possible. Results suggest that more than 90% of samples can meet these requirements following commonly used dewatering technologies. A comparison across technologies provided strong evidence that the faecal sludge source significantly influences sludge composition, emphasized by higher median ratios of fixed carbon to volatile matter in VIPs (0.23) and UDs (0.23) compared to STs (0.15). The sanitation technology also influenced recoverable nutrient concentrations, with phosphorus and potassium concentrations generally ranging between 5.8–49.2 g/kg and 1.4–26.1 g/kg respectively. Compared to STs, median concentrations of phosphorus and potassium in VIPs were 3.4 and 3.8 times higher respectively, and 3.0 and 8.8 times higher in UDs. The findings highlight the importance of considering the faecal sludge source in the development of thermal treatment processes. This study provides critical knowledge to further develop such processes through modelling, experimental and scaled approaches.
Issue Date: 1-Feb-2021
Date of Acceptance: 9-Nov-2020
DOI: 10.1016/j.jenvman.2020.111658
ISSN: 0301-4797
Publisher: Elsevier
Journal / Book Title: Journal of Environmental Management
Volume: 280
Copyright Statement: © 2020 Elsevier Ltd. All rights reserved. . This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: 144356 (EP/N010124/1)
Keywords: Characterisation
Faecal sludge
Resource recovery
Thermal treatment
Environmental Sciences
Publication Status: Published
Article Number: ARTN 111658
Online Publication Date: 2020-11-24
Appears in Collections:Civil and Environmental Engineering

This item is licensed under a Creative Commons License Creative Commons