Chemical process design of solid waste management for use in railway rolling stock

Proper management and disposal of highly wet hazardous sanitary solid wastes is of utmost importance for developing countries or parts of developed ones where sewage infrastructure is inaccessible. For instance, the sewage generated in on-board train toilets is being stored in a controlled emission tank (CET) fitted under the carriages that is further emptied in depot using extraction facilities. A method still requiring the final management of generated sludge while being costly with the train being pulled off the track. Implementation of advanced thermal processes in small scales within the context of a decentralized wastewater treatment system has recently been found promising for the on-site stabilisation of sanitary faecal sludge. This research has outlined the requirements, challenges and constraints associated with the utilisation of thermal conversion technologies to aid in the development of system for this application. The thermochemical properties of multiple batches of solid wastes stored in CETs has been characterized for the first time to aid in the design of an innovative pyrolysis system. A drying unit for the simultaneous pre- treatment and resource recovery from faecal sludge is developed. The drying efficiency of the unit is evaluated, and the extent of nutrients recovered through the unit are discussed while design implications for further improvements are provided. Following this, the obtained data on the chemical properties of partially dried products are used for the testing and evaluation of a pyrolysis reactor. The prototype was a novel twin auger pyrolysis reactor based on the application constraints and successfully commissioned. Effects of various process parameters on the conversion of faecal sludge is assessed through extensive chemical characterization of the process products (e.g., syngas, biooil and biochar). The outcomes of the research were discussed to provide insight into the by-products for further disposal or usage. Throughout this thesis, points for further research are highlighted based on the findings and observations.