Selection of sustainable sanitation technologies for urban slums — A case of Bwaise III in Kampala, Uganda
Introduction
The major contributors of the pollution load in urban slums into the environment are excreta, grey water and solid wastes (Eriksson et al., 2002, Eriksson et al., 2009, Howard et al., 2003, Kulabako et al., 2007, Paterson et al., 2007). Slums in developing countries lack basic sanitation services due to poor accessibility, lack of legal status and financial resources (Maksimović and Tejada-Guibert, 2001, Kulabako et al., 2007, Paterson et al., 2007) as well as lack of supportive infrastructure (von Münch and Mayumbelo, 2007). The main sanitation challenges for slums are the ways of enhancing demand for sanitation, the sustainability question and the institutional structures and arrangements for upscaling and replication by other practitioners (Franceys, 2008, Jenkins and Sugden, 2006).
One of the ways to deal with pollution streams in urban slums is through the provision of well functioning sanitation systems. Sanitation here refers to the management of human excreta, grey water, solid waste and storm water. The main polluting constituents are pathogens that endanger public health and nutrients that may cause eutrophication of surface waters and pollution of groundwater. Human excreta management is the key to public health in urban slums since most of the pathogens are of faecal origin. They form a major cause of disease transmission due to the presence of pathogens in excreta and when mixed with wastewater, the pathogens flow downstream and spread in the environment especially during flooding (Feachem et al., 1983, Prüss et al., 2002, Niwagaba et al., 2009).
Human excreta are predominantly disposed in slum areas by use of unlined pit latrines which are usually elevated in areas with a high water table. Other excreta disposal facilities and options include traditional pit latrines, flying toilets (use of polythene bags for excreta disposal that are dumped into the surrounding environment), open defecation and to a small extent ventilated improved pit latrines (VIP) and pour flush toilets by the few high income earners (Kulabako et al., 2007, Muwuluke, 2007). These excreta disposal systems in use are considered unimproved because they are shared by many households (WHO and UNICEF, 2010). Moreover, they pollute the groundwater through direct and indirect discharge of pollution loads into the environment.
The current need to increase sanitation coverage to meet the MDG sanitation target has triggered provision of sanitation systems also in slum areas. However, little thought is given to the treatment of the collected waste. The high population density in slums and the typical flood prone locations tend to enhance the problem of overflowing pit latrines and washout of flying toilets. Excreta disposal facilities are a component of the sanitation system, which can be sustainable if it is affordable, developed to ensure pathogen removal and efficient for the recovery and reuse of nutrients contained in the excreta (Otterpohl et al., 1999, Mara, 2003, Kvarnström and af Petersens, 2004, Langergraber and Muellegger, 2005, Bracken et al., 2007). Sustainability of sanitation systems in urban slums may be achieved if technology selection methods that take into account the local situation are adopted.
This study focused on Bwaise III (32° 34′E, and 0° 21′N), a slum area located in Kampala, Uganda (Fig. 1). Bwaise III has six Local Council (LC) 1 zones (the lowest administrative unit at the Local Government Level) namely: Kawaala, Katoogo, St. Francis, Bugalani, Bokasa, and Kalimali. In total, 15,015 people are estimated to live in an area of 57 ha making the population density 265 persons per hectare (UBOS, 2002, Kulabako et al., 2007). The population growth rate of the study area is currently estimated by the Kawempe Division to be 9%. This is above the national average value of 3.4%. The area was initially a wetland connected to the existing Lubigi wetland to which it drains.
The slum area evolved as a result of illegal encroachment on the wetland. Consequently, there is no legal status of ownership of the area which makes provision of basic water and sanitation services difficult. The high water table and vulnerability of the area to flooding in rainy seasons has also made it difficult to construct pit latrines that are largely used in this area for excreta disposal. This indicates that there is a strong need to take the location into account in providing appropriate sanitation. Recently, an extensive study was carried out to investigate the groundwater situation in Bwaise III (Kulabako et al., 2007, Kulabako et al., 2008). It was concluded that a large part of the pollution was sanitation-related. This study therefore focuses on the sanitation situation in Bwaise III by analysing the current situation and developing a method to select sustainable sanitation options for excreta management.
Section snippets
Materials and methods
This study was carried out in three phases. The first phase involved conducting a household survey to obtain baseline data. The second phase involved developing a database to enable comparison of different technology solutions based on established criteria to relate them to the baseline data. Finally, a multi-criteria analysis was carried out to incorporate the views of experts (technical and non-technical professionals) and stakeholders into the technology selection.
Human excreta management
The excreta disposal facilities in Bwaise III range from simple/traditional pit latrines to flush systems with septic tanks. The majority of the residents (> 50%) use elevated pit latrines for excreta disposal. Other excreta disposal technologies used include Ventilated Improved Pit (VIP) latrines and pour flush toilets (Fig. 4A).
Most of the sanitary facilities are shared and 75% of the slum dwellers use shared facilities. Community or public toilets are accessed by 15% of the people and 10% of
Human excreta management
Pit latrines are the dominant type of excreta disposal in Bwaise III due to their low cost as a result of the use of available raw materials for construction and the low level of water services and lack of affordability for water borne systems. The pit latrines are elevated due to the high water table. Very few people use VIPs and flush toilets connected to the septic tanks due to the high investment costs of these systems and lack of willingness by landlords to invest in sanitation facilities.
Conclusions
The existing sanitation systems in Bwaise III are unsustainable and are largely unimproved, which lead to ground water pollution and unhygienic conditions. In addition, most residents do not benefit from solid waste services provided by the local government or private sector due to limited access in the slum and low levels of affordability. Currently there are very few house water connections and an average water consumption of 18 L/cap day which makes water-based systems such as simplified
Acknowledgements
This research was funded by the Netherlands Ministry of Development Cooperation (DGIS) through the UNESCO-IHE Partnership Research Fund. It was carried out jointly by UNESCO-IHE, Makerere University, and the Kampala City Council in the framework of the Research Project ‘Addressing the Sanitation Crisis in Unsewered Slum Areas of African Mega-cities’ (SCUSA). It has not been subjected to peer and/or policy review by DGIS, and, therefore, does not necessarily reflect the view of DGIS.
References (51)
- et al.
The role of weights in multi-criteria decision aid, and the ranking of water projects in Jordan
Eur J Oper Res
(1997) - et al.
Micro-scale anaerobic digestion of point-source components of organic fraction of municipal solid waste
Waste Manage
(2009) - et al.
Characteristics of grey wastewater
Urban Water
(2002) - et al.
Grey water pollution variability and loadings
Ecol Eng
(2009) - et al.
The future of anaerobic digestion and biogas utilisation
Bioresour Technol
(2009) - et al.
Risk factors contributing to microbiological contamination of shallow groundwater in Kampala, Uganda
Water Res
(2003) - et al.
Recycling-an environmentally friendly and income generation activity towards sustainable solid waste management. Case study Dar es Salaam city
Resour Conserv Recycling
(1996) - et al.
Study of the impact of land use and hydrogeological settings on the shallow groundwater quality in a peri-urban area of Kampala, Uganda
Sci Total Environ
(2007) - et al.
Ecological sanitation — a way to solve global sanitation problems?
Environ Int
(2005) Water, sanitation and hygiene for the health of developing nations
Public Health
(2003)
Simplified sewerage: potential applicability in industrialized countries
Urban Water
Comparing microbial die-off in separately collected faeces with ash and sawdust additives
Waste Manage
Pollution of protected springs in relation to high and low density settlements in Kampala — Uganda
J Phys Chem Earth
Source control in urban sanitation and waste management: ten systems with reuse of resources
Water Sci Technol
Pro-poor sanitation technologies
Geoforum
Feasibility versus sustainability in urban water management
J Environ Manage
The road not taken: how traditional excreta and greywater management may point the way to a sustainable future
Water Sci Technol Water Supply
The design and analysis of research studies
Serving all urbanconsumers-A marketing approach to water services in low and middle-income countries. Book 3: PREPP-Utility consultation with the urban poor
Sampling techniques
Water supply design manual by MWLE
Sanitation and disease: health espects of excreta and wastewater management
Cited by (96)
Sustainability assessment of faecal sludge treatment technologies for resource recovery in Phnom Penh, Cambodia
2023, Environmental Technology and InnovationHydrothermal carbonization reaction severity as an indicator of human-excreta-derived hydrochar properties and it's combustion
2023, Science of the Total EnvironmentConstructing and selecting optimal sustainable sanitation system based on expanded structured decision-making for global sanitation and resources crisis
2021, Journal of Cleaner ProductionCitation Excerpt :It is now widely accepted that sanitation planning should consider the entire sanitation chain and rely on the principles of sustainability (Tilley et al., 2014b; Zakaria et al., 2015). Each technology of sanitation chain should be appropriate to the context-specific health (Katukiza et al., 2010), environmental, economic and financial, socio-demographic, and institutional conditions (Spuhler et al., 2018). Therefore, the design of sanitation system not only highlights the multi-criteria aspect but also the trade-offs and stakeholder or decision-maker (Willetts et al., 2013).
Plastic bag usage and the policies: A case study of China
2021, Waste Management