INVESTIGATING THE DEWATERING CHARACTERISTICS OF FAECAL SLUDGE IN THE CONTEXT OF FAECAL SLUDGE WATER BOUNDNESS

Abstract

Access to adequate sanitation is still elusive in many parts of the world, with approximately 2 billion people lacking sanitation globally. The impacts of poor or lacking sanitation service delivery systems include negatively impacting water quality and causing health risks to the populations involved. The preferred centralized sanitation systems have gaps and can barely help the situation, especially in developing countries, which points to the necessity of a paradigm shift in wastewater management to include interventions that would make proper sanitation accessible to all. Such interventions include onsite sanitation systems (OSSs) and subsequent faecal sludge management (FSM), which with appropriate treatment, have a lot of potential to produce environmentally acceptable effluents and are also pertinent in achieving decreased costs for sanitation systems sanitation more affordable to all. Faecal sludge (FS) dewatering is indispensable for adequate FSM. However, there is a shortage of knowledge on FS characterization and dewatering tendencies. This thesis work investigated the dewatering characteristics of faecal sludge in the context of faecal sludge water boundness. Six samples from ventilated improved latrines (VIP), Urine diversion dehydrating/drying toilets (UDDT), and septic tank (ST) in Ethekwini Municipality in Durban, South Africa, were analysed. Evaluation indices of dewatering and moisture release, settleability, filterability, and centrifugability; by sludge volume index (SVI), specific resistance to filtration (SRF), and centrifugation tests were determined. In addition, sludge physical properties – density, porosity, and particle size distribution (PSD) - effect on FS dewatering was analysed. Data was analysed in an Excel spreadsheet to compare the mean results of each sample category and correlation and multiple regression analysis to quantify the relative importance of FS physical characteristics on dewatering. Results showed that dewatering was different between FS from different OSSs. Correlation between sludge physical properties and settleability and filterability were also identified. The results identify potential characteristics that influence faecal sludge moisture release and predict dewatering rate.