Assessing sanitary mixtures in East African cities

Autor: Letema, S.C.
Přispěvatelé: Wageningen University, Jules van Lier, Bas van Vliet
Jazyk: angličtina
Rok vydání: 2012
Předmět:
Popis: The urbanisation of poverty and informality in East African cities poses a threat to environmental health, perpetuates social exclusion and inequalities, and creates service gaps (UN-Habitat, 2008). This makes conventional sanitation provision untenable citywide, giving rise to the emergence of sanitation mixtures. Sanitation mixtures have different scales, institutional arrangements, user groups, and rationalities for their establishment, location, and management. For assessing the performance of both the mixtures as a whole and the different sanitation approaches constituting these mixtures, novel approaches for analyses are required. This thesis, therefore, departs from the centralised-decentralised approaches to a modernised mixtures (MM) approach in seeking a more inclusive assessment of sanitary configurations taking into account public and environmental health, accessibility and flexibility of sanitation systems as sustainability criteria. To achieve this, the four objectives formulated for this thesis are to: 1. Make an inventory of sanitary systems in Kampala and Kisumu. 2. Assess and map sanitary systems along MM dimensions in Kampala and Kisumu. 3. Assess sustainability of sanitary systems on defined MM criteria in Kampala and Kisumu. 4. Enhance insights on the applicability of MM criteria as conceptual model, assessment and prescriptive tool for sanitary mixtures in East African cities. Case study cities were chosen from a typology of primary and secondary cities that have urban sewer systems since colonial times. The two cities were deemed to offer rich cases that would give a general outlook of other East Africa cities, thus can offer possibilities for generalization. The thesis utilised a multi-method and multi-level approach in data collection and analysis. A multicriteria analysis is used in sustainability performance assessment of sanitation systems based on defined MM criteria. Firstly, modernisation debates and resultant modernities in sanitation provision were reviewed in Chapter 2. The review shows that Western modernisation and resultant modernities and their structures of service provision have not resonated well in developing countries. Consequently, alternative theories that dispute a universal approach to modernity emerged to offer alternatives to modernisation. Alternative options are characterised by multiple rationalities, diversity and multiplicity. Modernities in terms of sanitation provision are further operationalized as competition between the proponents of centralised versus decentralised solutions. A third way of looking at sanitation modernisation that is more inclusive is advanced through the introduction of the MM approach. In Chapter 3, the presence of urban sewer systems in Kampala and Kisumu cities is assessed. The results show that urban systems are of medium scale and serve about 10% of the city population. They are publicly owned and managed by public enterprises under new public management. Besides, they are conventionally designed, constructed and operated without the involvement of end-users. Treatment plants are either overloaded, underutilised or treatment stages are mismatched. Consequently, about 30-70% of the treatment stages are not operational. Effluent discharge standards and bio-solids reuse requirements are not met, and the adopted treatment technologies are inappropriate for the investigated conditions. Sewer networks are supported by pumping stations and siphons that are only partially operational due to high operational costs and mechanical failures. Public sewerage is further plagued by urban informality and multiplicity of city spatial structures. Planned city core, and to a limited extent peri-urban areas, are served by public sewers, while sewer trunk lines pass through informal slum settlements without connections. In Chapter 4, satellite systems are analysed and configurations mapped. Satellite systems are intermediate semi-collective decentralised sewerage and treatment systems developed parallel to urban and onsite systems. They are provided by multiple actors, serve planned middle and high income residential, industrial complexes, endowed public and private universities, and government facilities. In terms of scale, they are community, neighbourhood and small-urban sanitation solutions. Besides, satellite systems are private sewerage systems that utilise gravity sewers and localised mechanised or non-mechanised treatment. The flows are based on land use or facility specific and are treated close to the point of generation. They are based on conventional designs and construction protocols without end-user involvement. Onsite systems in Kampala and Kisumu cities are examined in Chapter 5. Planning forecast indicates that onsite systems will dominate sewer (urban and satellite) systems beyond the next two decades. They are small-scale, highly decentralised and use simple technologies. Pit latrines dominate septic tanks in number, with eco-san on pilot scales and bio-latrine being a new sanitation option. Faecal sludge collection, treatment and safe disposal is dismal. The private sector dominates over local authorities in provision of faecal sludge services, but public sewerage agencies receive and co-treat faecal sludge with sewage although sewage works are not designed to receive faecal sludge. They are regulated by the Ministry of Health, enforced by the city councils and are provided by multiple actors solely or in partnership. Onsite sanitation can be a transient or permanent solution depending on mass flows and spatial requirements. However, for better sanitation provision, a permanent solution, with room for amendments to anticipate changes in space and mass flow is imperative. In Chapter 6, sustainability performance of sanitation systems are assessed following the defined three MM criteria. The performance shows that there is no sanitation system that is completely outcompeted in performance, neither are there systems with a very good performance. Sanitation system choices, consequently, are made among imperfect options, which call for balancing the various elements of sanitation provision to suit different policy and local contexts. Varying the assigned relative weight of the various criteria used in the overall MCA assessment indicates that generally, any slight increase in weight has an impact on systems that already have a high performance whereas in the case of systems with low performance the change is dismal or even negative. Therefore, programmes for improvement of sanitation systems might be directed to improvement options where systems already have a relatively high performance. However, those with a low performance may need comprehensive or even system reconfigurations for significant impacts to be realised. In conclusion, sanitation mixtures are theorised as the co-existence of different phases of modernity in tandem with local context variables. Thus, there is no one-fit-all paradigmatic way to sanitation provision if the local contexts are apparently different even within the same city. However, a shift of the centralised-decentralised dichotomy to modernised mixtures paradigm offers better impetus as it can utilise the advantages of both centralised and decentralised approaches without jeopardising existing provision pathways. The MM approach is helpful in assessing, mapping and describing sanitation systems in cities where sanitation mixtures are the norm rather than the exception. One way to modernise sanitation mixtures is by shifting the centralised-decentralised paradigm in order to modernise the mixed sanitation landscape. This is premised on the notion that such a shift will result in merging the strengths of centralised approach, e.g. economies of scale, efficiency, and convenience, with strengths of decentralised approach, e.g. accessibility, flexibility, participation, and reuse and recovery in development of intermediate systems configuration. This can be achieved through, among others, avoiding use of pumping stations, adoption of multiple service levels, involvement of private sector, servicing households at intermediate scale, and establishing sanitation suitability and management zones. The MM approach is also very helpful as a conceptual model for organising a research agenda which can be set along the four assessment dimensions of scale, management, flows and participation, as well as in searching for appropriate intervention measures along one or more of these dimensions. As an assessment and decision making tool, it is helpful in finding out which elements highlighted in the sustainability assessment need to be restructured and which need improvement in order to enhance their sustainability. However, translation of the proposed conceptual MM model into a mathematical model is a challenge yet to be explored. Considering its intrinsic dynamic character in dependence to varying spaces, flows, and scales along city development, a mathematical MM model would provide a regulatory design tool for city planners for adopting amendments to existing sanitation solutions. Obviously, up to date monitoring and inventory records are a pre-requisite for applying such a model, requiring institutional upgrading. Although the current results described in this thesis provide the basis for a more structured assessment and generalisation of sanitation mixtures, more research and contextualisation is needed in other regions, for further elaboration of MM model, and for the refinement of the assessment tool.
Databáze: OpenAIRE
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