Assainissement | EPFL Graph Search

L’assainissement est une démarche visant à améliorer la situation sanitaire globale de l'environnement dans ses différents composants. Il comprend la collecte, le traitement et l'évacuation des déchets liquides, des déchets solides et des excréments. L'objectif principal est la prévention du contact humain avec des substances dangereuses, spécialement les fèces en mettant en place des systèmes de traitement et d'évacuation des déchets. Les dangers issus d'un mauvais assainissement sont multi-factoriels, pouvant être à la fois physique, microbiologique, biologique ou encore chimique. Les déchets, ce qui inclut les excreta d'origine humaine et animale, les déchets résiduels ou encore les eaux usées, peuvent causer des ennuis de santé majeurs. Des systèmes d'assainissement plus hygiéniques peuvent s'appuyer sur des solutions technologiques telles que les égouts ou les stations de traitement des eaux usées. Ces systèmes peuvent aussi suivre une approche plus décentralisée et simple avec

Vers un assainissement urbain durable en Afrique subsaharienne

Halidou Koanda

Justification In Sub-Saharan Africa, excreta and wastewater disposal is characterised primarily by on-site sanitation systems. This sanitation option is more likely to increase as governments, municipalities, communities, private operators and donor agencies strive to reach the Millennium Development Goals aimed at reducing by half the proportion of people without access to basic sanitation facilities. Due to increased urban population growth in Sub-Saharan Africa, the faecal sludge volumes will increase to alarming quantities in the coming decades. An evaluation of faecal sludge management practices reveals that the main shortcomings relate to the widespread lack of involvement and foresight by the municipalities, the paucity of effective legal provisions and organization, and the absence of stakeholder coordination. Stakeholder involvement for planning and implementing faecal sludge management is virtually inexistent or excluded from urban sanitation planning processes. In the majority of situations, faecal sludge management is financially not viable. This is a major cause of the indiscriminate dumping of faecal sludge in urban areas or its untreated use in urban agriculture. These practices not only pose permanent and serious health risks but also contaminate both scarce ground and surface water. Objective and general approach On the basis of these facts, which present a real challenge to sector specialists, the overall objective of our research is to develop an innovative strategic planning approach for sustainable faecal sludge management in urban areas which allows minimising public health and environmental risks. Focus is placed on developing a reproducible methodology for stakeholder involvement, on enhancing population awareness for improved faecal sludge disposal and attributing a leading role to the dynamic private faecal sludge emptying and transport operators. These aspects form the three pillars of our search for a comprehensive methodological approach. The municipality of Ouahigouya in Burkina Faso with a population of about 65'000 inhabitants was used as pilot site to launch, implement and scientifically validate the approach. Analysis and stakeholder involvement The stakeholder-based planning approach developed in Ouahigouya relies on a combination of stakeholder identification and analysis, and participatory planning techniques (focus groups, workshops, informal meetings, all-stakeholder workshops). A quantitative survey among households allowed collecting stakeholders' proposals and evaluating suggestions for improvement of faecal sludge management and neighbourhood hygiene proposed by the population. The main steps in the stakeholder involvement approach include: Jointly clarifying the objectives of the planning process together with the stakeholders; Identifying stakeholders and their interests; Classifying stakeholders according to their importance and influence based on defined criteria and confirmed by the stakeholders themselves; Identifying the interactions between the stakeholders; Verifying the results of the stakeholder analysis by the stakeholders themselves; Choosing stakeholder involvement techniques; Implementing the chosen method of stakeholder involvement: development of faecal sludge management scenarios, acceptance of the scenarios by the stakeholders in focus groups, choice and acceptance of a basic scenario for development of the future strategy in an all-stakeholder workshop; Evaluating the chosen involvement process by the stakeholders. The experience gained with the planning methods developed and implemented in Ouahigouya reveals that the "Stakeholder analysis" method is efficient and provides answers to questions such as: Who are the important and influential stakeholders? Who should participate in the planning process and in which manner? This experience also revealed the need for capacity building of certain stakeholder categories (emptying operators, women's associations, etc.) to increase their degree of involvement in the planning process. Improvement in stakeholder involvement was achieved thanks to a combination of workshops, focus groups and other informal meetings allowing less influential stakeholders (associations of local women, horticulturists, emptiers) to share information and to freely express their opinions and concern and to defend their interests. Thus, providing an excellent example of local democracy appreciated by all stakeholders of Ouahigouya. The approach developed provides tools for policy-makers and planners to ensure an effective stakeholder involvement in the process of developing a common vision and implementation of improved urban sanitation measures. The conditions for replicating the approach developed and tested in Ouahigouya are due to participatory democracy, great commitment of the local authorities and the high motivation of the stakeholders involved. Levers for the willingness-to-improve faecal sludge management and neighbourhood hygiene The evaluation method of the willingness to improve faecal sludge management by the population was based on a combination of the planned behavior model of Ajzen and the contingent valuation method, financial analysis of the pit emptying and faecal sludge enterprise, and on focus groups of stakeholders. By focusing on local practices, perceptions and individual behavior, this method revealed that financial viability – often reduced to willingness-to-pay – is not the only factor to consider when planning improvement of sanitation practices. Willingness-to-improve is highly dependant on psycho-sociological factors such as attitude towards and beliefs in an improved neighbourhood environment, social pressure on the households by the neighbourhood as well as the subjective costs and benefits expected from improved faecal sludge management. These factors therefore present levers allowing planners and decision-makers to encourage, increase and develop the demand for improved latrine emptying services, e.g. though social marketing. Promoting private entrepreneurs According to market analysis of emptying services and stakeholders involved, small private and mainly informal enterprises play a leading role in faecal sludge management in most cities of Sub-Saharan Africa. These operators, dynamic but fragile, require an appropriate institutional, jurisdictional and economic environment based on a balanced partnership between the municipality (public) and the private sector. Our study reveals that for a company truck to be profitable, about 1'000 trips per year (at 6'000 FCFA per trip) are required or the equivalent of a city of 56'000 inhabitants. In the case of Ouahigouya, profitability is increased if the emptying operators apply the latest management and professional tools and techniques, and manage to provide emptying services in neighbouring towns. Decision support tools The research led to developing decision support tools for professionals and policy-makers. These tools facilitate the development of a tariff-oriented policy to avoid uncontrolled faecal sludge discharge into the environment, to render investments by private operators profitable, and still make emptying services accessible to low-income households. This involves: Analysis of the cost structure of 3 pit emptying companies has revealed that fuel, maintenance/repair and personnel costs make up 45%, 20% and 30%, respectively, of an enterprise's operating expenses. An Excel programme was developed to allow municipalities and private operators to determine the operating costs of emptying services. This allowed to establish a sustainable money flux between the different stakeholders involved and to define the tariffs. To prevent faecal sludge discharges in the immediate residential environment or on unauthorised sites, it might under specific circumstances prove necessary and feasible to reimburse rather than charge entrepreneurs for delivering faecal sludge to the treatment sites, hence, create a strong incentive for good emptying and haulage practice. Evaluation methods of the sludge quantities to be disposed of have been developed to allow faecal sludge planning by the municipal authorities, assessment of the potential market and return on investment by the private operators. Advantages of the approach for the population of Ouahigouya Based on the results of our study, it was possible to formulate practical recommendations for the organisation of the urban sanitation sector for the municipality of Ouahigouya – now in possession of a sustainable faecal sludge management strategy. Our study has also contributed to promoting local consultation and raising the awareness of the role and contribution of each stakeholder group, in particular the previously neglected manual emptiers in their daily efforts to improve the living conditions of the urban inhabitants. The "Strategic Excreta and Wastewater Sanitation Plan", that was developed and supported by the "Office National de l'Eau et de l'Assainissement - National Water and Sanitation Agency", provides an excellent framework for the implementation of the elaborated faecal sludge management model (as part of the this strategic plan).

EPFL2006

Water and sanitation hub in Mali. Reasons for an architecture seminar

Riccardo Vannucci

What is the goal of a five-day seminar for the (architectural) design of a ‘water and sanitation hub’ in Mali? What does one want to achieve, or rather, what is the seminar meant to ‘disseminate’? To begin with, what is a ‘water and sanitation hub’? It is a place where water, sanitation and other facilities are available (hub is the central part of a wheel that connects the axle to the wheel itself). Water is water, and sanitation refers to the provision of facilities and services for the safe management of human excreta from the toilet to containment, storage and treatment onsite, or, alternatively, conveyance, treatment and eventual safe end use or disposal). Water and sanitation is an eminently technical field, dealt with by specialists. Usually, relatively little is said about water and sanitation in schools of architecture.

EUNSA. Ediciones Universidad de Navarra, S.A.2020

Assessment of the impacts of local conditions and sampling methods on the characteristics of faecal sludge

Amédé Ferré

Since 1990, almost 1.9 billion people have gained access to an improved sanitation facility, while 2.6 billion people still live without access to improved sanitation. In urban areas of low- and middle-income countries, the majority of household rely on onsite sanitation systems, producing huge amounts of faecal sludge (FS) that end in the environment every day. FS has to be managed in a proper way, integrating onsite system, storage, transport, treatment, disposal and reuse. In the past years, several FS treatment technologies have been developed and implemented, however partly due to the lack of knowledge on the FS characteristics, many of them have encountered failures. Reliable assessment of FS characteristics is essential in order to design adequate FS treatment facilities. However, FS is a highly variable waste and no methodology has been established to better understand this variability and the characteristics so far. This Master project, which takes place in the framework of the PURR project (Partnership for Urban Resource Recovery) that is a collaboration between the Sandec (Department of Water and Sanitation in Developing Countries, Switzerland), EPFL (Swiss Institute of Technology of Lausanne, Switzerland) and IESE (Institute of Environmental Sciences and Engineering of Hanoi, Vietnam), aims to answer this important gap of knowledge. To assess the influence of the local conditions on the characteristics of FS, fifty nine samples of household septic tank have been collected in Hanoi, the capital city of Vietnam. Fourteen factors reflecting local conditions and twenty eight parameters have been measured. QA/QC procedure together with the analysis of the organic compounds helped to determine the reliability of the data. Therefore, only reliable data was discussed, including seven factors (number of inhabitant, septic tank age, FS age, bio-additive, water addition in the septic tank, septic tank volume and number of trucks to empty the septic tank) and twenty parameters (temperature, pH, TS, TSS, VS, VSS, COD, carbohydrate, lipid, protein, VFA, TN, NH4+, TP, PO43-, total fibres, Ni, Pb, Fe and Zn). A degradation of the solids (TS, TSS), organic fraction (VS, VSS, COD, carbohydrate, protein, VFA) and nitrogen compounds (TN, NH4+) is mainly observed during the ten first years of storage. Addition of bio-additive potentially contributes to this process. The size of the septic tank seems to influence also the emptying frequency and then the degradation of the matter. Six sampling methods (S, HG, HT, B, M and D methods) have been tested over six samplings of household septic tank in Hanoi. First method with direct sampling inside the septic tank (S). Two methods collecting sludge from the manhole with different heights of collection (HG=15.4cm, HT=4cm). Three methods from the discharge valve of the truck (B=at beginning; M=at middle; D=at beginning, middle and end of the discharge with a volume ratio of 1:2:1 respectively). Sampling methods seems to not have influence on pH and temperature and soluble compounds concentrations. However, solids, organic content and nutrients concentrations are influenced. HG tends to under-estimate the concentrations when B and D could over-estimate it. HT and M seems to be the more accurate and reliable sampling methods of FS tested. Such knowledge on the FS variability could allow reducing the number of samples needed to obtain representativeness of FS. Indeed, collecting information related to the factors previously mentioned at the household level could work as predictor together with the characterization study to evaluate FS characteristics of a specific area. This allows savings in terms of time and budget. Moreover, the influence of the three factors (FS age, bio-additive addition, septic tank volume) on the FS characteristics, could constitute a basis for the development of policies and regulation. In order to reduce pollutant concentration in FS, appropriate emptying frequency and adequate storage tank design could be determined. The sampling methods HT and M would constitute low cost sampling methods, which would be simple to handle, fast, efficient and reliable to collect FS, and easily reproducible in different context. This is a real step forward for the improvement of knowledge about FS characteristics.

2014