The potential of innovative dry source-separating urban sanitation technologies in Montero, Bolivia : A sustainability assessment

Abstract: Montero is one of the cities with the highest population growth inthe lowlands of Bolivia. According to Montero's municipal plan for water and sanitation, only 36 % of the population in the urban areas of Montero is connected to the sewage system. Since 2015, approximately 200 urine diverting dry toilets (UDDTs) have been built in Montero, providing safe sanitation to a thousand inhabitants lacking access to the sewage system. However, the treatment of the faeces and urine is inadequate, with loss of valuable nutrients and risk of polluting water bodies. The objective of this study is to assess nutrient recycling innovative dry source separating sanitation systems, in a context relevant for Montero, using a selection of sustainability criteria. Three innovative dry sanitation systems, collecting and treating the faeces and urine from the UDDTs, were assessed in relation to the existing system. The assessment was performed on the basis of multiple criteria within the following categories: Health, Resource Use, Environmental, Socio-Cultural, Technical-organizational and Financial. From literature research and calculations of nutrients and costs, the indicator for sustainability for each criterion was scored from 1 (worst) to 5 (best). The first alternative sanitation system, which collects and stores the liquid urine centrally and treats the faeces with vermicompost, was considered more sustainable from the health, resource use and environmental perspectives, but reported a lower value of the produced fertilizers than the other two innovative alternatives. Alternative 2, producing a solid fertilizer from the urine by ion exchange with peat and zeolite and adding urea treatment to the humus from the vermicompost, reported the largest amount and highest total value of the fertilizers and good resource use. However, the system was least sustainable from a technical-organizational point of view and had the highest annualized costs. Lastly, alternative 3, drying the urine on site and treating the humus with urea from the dried urine, reported the highest nutrient recovery rate while the energy consumption was much higher than for the other systems. Despite numerous assumptions for the calculations in this report, the result can indicate which sanitation system is most sustainable from each perspective. Future recommended studies are laboratory tests of the nutrient content from local pilot tests to evaluate the economic value of the produced fertilizers as well as further analyzing the farmers' social acceptance towards using fertilizers produced from UDDTs.