The PhD Thesis covers a review of sanitation technology options for urban slums including existing technologies, their application status and the knowledge gaps. A novel method for selection of sustainable sanitation technologies in urban slums is presented as an alternative to software applications. This method promotes holder participation and ensures sustainability of the selected and implemented sanitation systems. Furthermore, this PhD research provided an insight into the genomic copy concentrations of selected waterborne viruses in a typical urban slum and the magnitude of microbial risks to human health caused by pathogens (bacteria and waterborne viruses through various exposure pathways. The results show that urban slum environments are polluted and the disease burden from each of the exposure routes. In addition, the grey water production in urban slums is more than 80% of the water consumption and the grey water pollutant loads pose potential public health and environmental impacts. The PhD thesis also covers aspects of optimisation of the filtration medium during grey water treatment by uPVC filter columns in series and parallel mode. In addition, the study demonstrated that grey water treatment using a two-step crushed lava rock filter unit at household level in an urban slum is feasible. The grey water pollutant loads reduced by 50% to 80% after grey water treatment. The main conclusions on sanitation in unsewered urban poor areas and recommendations for future research are included in this PhD thesis.