Development of a Technology to Ensure Sufficient Quantity and Quality of Rainwater for Rural Households

The availability of safe drinking water is an increasing major concern for the international community, especially in light of the changing climate. Climate change presents major uncertainties in future safe water access especially in rural communities that are already faced with water insecurity. For developing countries like Uganda, achieving the sustainable development goals (SDGs) will require a paradigm shift from centralized public water supply to decentralized water supply systems especially for rural areas where public water systems are non-existent. In Uganda, this is evidenced by the stagnation of water access figures over the past 5 years. In most rural areas in Uganda, households use shallow underground water sources such as springs, boreholes, open hand dug wells and rainwater harvesting. Only a small fraction of the urban population is connected to the national water grid, while the rest has to rely on untreated water sources. Rainwater harvesting has thus been fronted as a major contributing factor towards achieving SDG 6 of safe water access for all by 2030 especially for rural areas. Although Uganda adopted a rainwater harvesting strategy in 2005, several challenges have hindered its adoptions as a safe water source at household level. These contributed to the inability of the country to achieve the millennium development goal target of 80% safe water access by 2015. The main challenges to rainwater harvesting include: inadequate roof type and size, insufficient storage, changes in rainfall due to climate change and inadequate water quality. Although rainwater has been shown to often be within WHO limits for physio-chemical parameters, the microbiological quality is quite often below the WHO limits. Therefore any efforts geared towards making rainwater harvesting a conventional potable water source has to be combined with the promotion of low cost water treatment measures especially tailored for rural households. This has not been the case in Uganda which has undermined efforts to increase safe water access through rainwater harvesting. This PhD aimed at developing a technological strategy to ensure sufficient quantity and quality of water through rainwater harvesting for rural households. The specific objectives included an assessment of the current rainwater harvesting technologies among rural households; an assessment of the effect of climate change on rainwater harvesting potential of rural households; a comparison of water quality of rainwater harvesting systems with conventional water sources; an exploration of the potential of using artificial surfaces for runoff harvesting for domestic use and designing a low cost technology for treatment of potable water at household level. Kabarole district, in western Uganda, was used as a case study because it receives some of the highest rainfall amounts in Uganda hence having high rainwater harvesting potential. A household survey among randomly selected households was used to document existing rainwater harvesting technologies and community perceptions towards rainwater harvesting. In order to assess the effect of climate change on the rainwater harvesting potential, the 6 best performing Global circulation models (GCMs) were selected and used in developing a daily water balance model to generate rainwater projections for the 2025-2055 (2040s) and 2060-2090 (2070s) periods. The GCMs used to generate daily rainfall projections for 2025-2055 and 2060-2090 periods included ACCESS1-0, BCC-CSM-1-M, CNRM-CM5, HADGEM2-CC, HADGEM2-ES and MIROC5. The analysis was based on the Ugandan weather seasons, which included March, April, May (MAM) and September, October, November (SON) rain seasons in addition to December, January, February (DJF) and June, July, August (JJA) dry seasons. The comparison of water quality of rainwater harvesting systems with conventional water sources was achieved through using a sanitary risk score tool and laboratory analysis of 362 water samples from the different water sources. The tested parameters included pH, turbidity, dissolved oxygen and Escherichia coli (E. coli). In order to explore the potential of using artificial surface treatments for rainwater harvesting, a complete randomized block experimental design was setup in three replications based on a slope of 1%, 3% and 5%. The treatments included: wax on bare soil (W), wax on sand (WS), wax on gravel (WG), wax on rice husk ash (WA) and a bare surface with short grass (C). The treatments were evaluated for both runoff and water quality characteristics for a period of one year. For the development of a low cost household water treatment system, the potential of integrating Moringa Oleifera with the bucket filter by creating a hybrid system that would work as efficiently as the conventional biosand filter (CBSF) but lower in cost and lighter in weight was assessed at laboratory scale. Results indicate that informal rainwater harvesting is more widespread in Kabarole district than formal systems, mainly due to high initial capital investments. An analysis of microbial quality of rainwater harvesting systems shows that there are no significant differences between the microbial quality of rainwater (from both formal and informal systems) and other improved water sources like boreholes, tap stands, protected springs and gravity flow schemes. The study also revealed that water savings, water security and reliability of rainwater harvesting systems will be adversely affected by climate change especially for small roofed households with smaller storage facilities. Specifically although there are conflicting model predictions, generally, the models agree that water savings, water security and reliability will reduce in DJF and MAM seasons and increase in JJA and SON seasons. MAM rain season will be most affected with water savings and security projected to reduce by more than 50% in the 2070s period. Therefore, households should harness the increased water savings in JJA and SON to cater for the predicted reduction in water savings in MAM and DJF seasons especially for the 2070s period. The study recommends an optimum roof size of 50 m2 or more and a 5 m3 tank volume. Evaluation of paraffin wax as a suitable surface treatment for water harvesting shows that paraffin wax underlain with gravel has very high potential with runoff efficiency ranging from 56-93%. All physiochemical parameters were within WHO guidelines, while E. coli contamination was observed in some cases hence emphasizing the need for household treatment before consumption. The development of a bucket filter and Moringa oleifera hybrid system showed that although the system was efficient at reducing turbidity, organic matter and pH, the bacterial log10 reduction was not up to the WHO standards. The E.coli removal efficiency of the hybrid system ranged from 81-98% which although high is not sufficient for drinking. The advantage of the hybrid system is that it weighs between 15-20 kg compared to 230 kg for the CBSF. The initial cost of the CBSF was more than double the cost of the hybrid system. Although more work is needed to operationalize the filter, this study provides a baseline for future research. The study recommends that households adopt formal systems even if storage systems are low. This will provide protection of harvested water from contamination because of the less exposure to the outside environment. It is also advisable to incorporate first flush techniques in harvesting systems. This ensures that the first quantity of water harvested, which is usually more contaminated, is channeled out of the main collection tank. It is also recommended that households with formal rainwater harvesting systems, carry out routine maintenance to reduce the risk of contamination of the harvested rainwater. In order for rural households to optimize rain water harvesting especially with projected climate change, roof size needs to be at least 50 m2 and a tank size of 5 m3 would be sufficient. This will ensure that households are more water secure even in the dry spells. For households with inadequate roof size, there is potential for using alternative harvesting surfaces especially on hillslopes. There is thus a need to explore other harvesting surfaces besides paraffin wax that may be cheaper but effective in enhancing runoff from the hillslopes. While a hybrid system with sand filter and Moringa Oleifera is promising, there is need to conduct further experiments with smaller sand grains to improve the microbial efficiency of the hybrid system. It is also imperative that the hybrid system is compared to other existing treatment systems currently in use.status: publishe