Urban agriculture | EPFL Graph Search

Urban agriculture refers to various practices of cultivating, processing, and distributing food in urban areas. The term also applies to the area activities of animal husbandry, aquaculture, beekeeping, and horticulture in an urban context. Urban agriculture is distinguished from peri-urban agriculture, which takes place in rural areas at the edge of suburbs. Urban agriculture can appear at varying levels of economic and social development. It can involve a movement of organic growers, "foodies" and "locavores," who seek to form social networks founded on a shared ethos of nature and community holism. These networks can develop by way of formal institutional support, becoming integrated into local town planning as a "transition town" movement for sustainable urban development. For others, food security, nutrition, and income generation are key motivations for the practice. In either case, the more direct access to fresh vegetable, fruit, and meat products that may be realised thr

Impact sanitaire de l'utilisation d'eaux polluées en agriculture urbaine. Cas du maraîchage à Ouagadougou (Burkina Faso)

Gueladio Cissé

In Ouagadougou and in many similar Sahelian cities, urban agriculture uses very often polluted water for irrigation of vegetables, including those that are likely to be eaten uncooked. As the pathogenic germs can survive long enough in water, soil and plants, this practice entails potential sanitary risks, particularly for farmers and their families. The potential of risks related to the use of sewage in agriculture is well known and sanitary instructions exist. However, there is no assessment of real risks within the context of sewage use on a small scale in small size plots, as it is the case in Ouagadougou, and common in Sahelian countries. The aim of the current thesis is to contribute to a better understanding of interactions between the environment and health. The specific objectives are: (i) - to assess incidence rates for diarrhoea In a period of two weeks and to assess prevalence rates for parasitic infections; (ii)- to assess relative risks and prevalence ratios among exposed groups and those of the population in general; (iii) - to assess levels of microbiological pollution of irrigation water, soils and vegetables; (iv) - to assess sociocultural factors and behavioural attitudes of the various actors; (v) - to assess environmental pollution at the level of residential areas; (vi)- to propose possible measures in order to reduce risks and to discuss their feasibility. The general approach that has been adopted is transdisciplinary, particularly with an epidemiological perspective associating microbiology, socio-anthropology, cartography and geomatics. The cartographical approach, with the assistance of geomatics made it possible (i) - to characterize residential areas in Ouagadougou according to pollution by refuse dumps and throwing out of sewage, (ii) - to locate market gardening sites in urban fabric, and (iii)- to assess the importance of exploited surfaces during the dry season, the cool season and the rainy season. Peripheral sectors are more polluted than central sectors. Variation in the total exploited surfaces between the cool season (December) and the dry season (April) is almost 85%. Six areas of market gardening represent in all seasons more than 55% of the total exploited surfaces. The majority of fanners in these 6 areas of market gardening live in 4 to 6 peripheral sectors (79% in 1992, 90% in 1995). The microbiological approach made it possible to monitor bacteriological (fecal coliforms) and parasitological (helminth and protozoan eggs) pollution in water, soils and plants. Water and soil samples have been taken in 4 market gardening areas which represent in all seasons between 49 and 56% of the exploited surfaces in the city; plant samples have been taken in the 4 areas of market gardening and in the central market of Ouagadougou. 668 samples of irrigation water, 247 samples of lettuce, 48 samples of carrots and 218 samples of soils have been analyzed between October 1993 and December 1995. The levels of bacteriological pollution for all types of water, most of the time, are above the thresholds recommended by WHO for the watering of vegetables that are likely to be consumed uncooked (1000 FC/100 ml). Water from canals or channels (Abattoir and Canal Central sites) prove to be more polluted, both bacteriologically and parasitologically, than the one from wells and dams (Boulmiougou and Tanghin sites). Lettuce from both market gardening sites and market has a bacteriological pollution that is beyond sanitary thresholds (100 FC/100 g), with higher levels in the market. A proportion of at least 10% of soil samples from paths are contaminated by parasites such as Ankylostomes, Ascaris and Anguillules. The market gardening sites which have the most polluted beds by parasites are those of Abattoir (79% of samples) and Canal Central (75%) which correspond to the sites with irrigation water that is also the most polluted. The socio-anthropological approach made it possible to gather ideas and beliefs of various actors in the chain of market gardening products (from producer to consumer) and to carry out direct observations about environmental factors as well as about practices in the various places in this chain. During the two years, 15 FGD (Focus Group Discussion) have been held with farmers, retailers, caterers and consumers. In 1995, 226 observations sessions have been held from 22 observation posts (5 market gardening sites, 3 markets, 3 caterers and 11 selected households). Whilst the environmental factors on market gardening sites are characterized by a high level of pollution, the behavioural attitudes of farmers during their activities, particularly walking barefoot, and expressed beliefs reveal a lack of awareness. The epidemiological approach made it possible to assess differences in incidence or prevalence rates between climatic seasons, between farmers and the general population, between market gardening sites, and between sexes, for diarrhoea, stomach aches and various parasitic infections. The data have been collected through households surveys and examinations in analysis laboratories of excreta and of households' drinking water. Three cross-sectional surveys with children as targets have been undertaken in 1994 (2 in the dry season and in the rainy season) and in 1995 (one at the end of the rainy season). Sample sizes were respectively 512, 599 and 3040 children aged between 0 and 4 full years and who have been weaned. During the third cross-sectional survey 208 adults, fathers or mothers of the surveyed children, have been also involved and water samples of 2996 households have been analyzed. A fourth cross-sectional survey dealt only with the group of market gardeners, with 191 adults, 97 children of farmers and 186 samples of households' drinking water. Differences are significant between the end of the rainy season and the two other seasons as far the diarrhoea and the main parasitic infections are concerned among the general population's children aged less than 5 years old. The incidence of two weeks' diarrhoea is very important in all seasons among the children of the general population (always > 30%) as well as among the children of market gardeners at the end of the rainy season (37.10 ± 9.61%). On the other hand, the incidence rate for two weeks' diarrhoea is low among adult farmers themselves at the end of the rainy season (6.30 ± 3.45%). The group of farmers, both children and adults, have in a very significant way higher prevalence rates than those of the general population as far as Ankylostoma are concerned (10.80 ± 6.68% against 1.40 ± 0.43% among children; 40.60 ± 7.38% against 14.90 ± 5.09% among adults). The difference between men and women is very significant for Ankylostoma among market gardeners (48.40% against 30.70%, PR= 1.58, p= 0.03). The epidemiological approach also made it possible to carry out a case-control analysis of diarrhoea among children of the general population aged less than 5 years old. The final logistic regression model draws a significant association (p < 0.05) between children's diarrhoea and 11 risk factors. These factors are related to either habitat conditions, or socio-economic conditions, or behavioural attitudes. The geomatic approach made it possible to disintegrate the main results of the epidemiological approach (as it has been done already for those of the cartographical approach) to present them at the sector level as thematic maps. The study leads to the formulation of recommendations in the area of (i)- actions and interventions; and (ii)- possibilities in research perspectives, regarding health and environment.

EPFL1997

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

Recyclage des eaux usées en irrigation

Yeli Mariam Sou

The present study takes place in Ouagadougou (Burkina Faso), a typical Sub-Saharan city where water shortage and food crisis necessitate wastewater reuse in urban agriculture. Different issues linked to this practice were studied in two components separated in two experimental sites. The first part treats about agronomic and sanitary aspects and take place in the 2iE (International Institute for Water and Environmental Engineering) experimental site of Ouagadougou. The second component was emphasised on industrial effluents impacts on irrigated soil quality and takes place in Kossodo, an industrial suburb of Ouagadougou. The 2iE site is supply with treated wastewater from domestic origin. The effluent was used to realise the following objectives: (1) managed wastewater fertilizers to fit the plant needs; (2) assess different crops sanitary quality and the effectiveness of methods used for this assessment. Three treatments were tested: (i) irrigation with the treated wastewater (ii) irrigation with the treated wastewater and fertilizers management, adjusted to plant needs and (iii) conventional treatment i.e. fresh water irrigation and total doses of commercial fertilizers. Each treatment was tested on three different crops: lettuce (Lactuca sativa), carrot (Daucus carota) and eggplant (Solanum melongena). The first objective was achieved by comparing crops yields (on basis of wet and dry matter) obtained with the different treatments. The three crops, irrigated with only wastewater, led to yield reduction between the first and the second year. At the contrary, the adjusted treatment showed higher yield for lettuce, with comparable values to conventional treatment yield. However, the effects on carrot and eggplant did not demonstrate better results; indicating that further investigations must be completed for crops with longer growing periods. Most likely, the fertilizers management should better correspond to the crop period demand. The sanitary assessment (second objective) was performed by measuring the heavy metals concentration (Cd, Cu, Pb, Ni, Cr) and the faecal levels (faecal coliform, Escherichia coli and four pathogens among which Salmonella typhimirium and Vibrio cholerae). Chromocult Coliform Agar medium was used for simultaneous detection of faecal coliform and Escherichia coli whereas pathogens were analysed by Polymerase Chain Reaction (PCR). From methodological point of view, faecal coliform were not sufficiently discriminatory in the case of this study since they were naturally present in the soil as well as in the fresh water. At the contrary, Escherichia coli were better linked to wastewater contamination. However, some "false positive" results were detected meaning that each presumptive colony of Escherichia coli must be confirmed. Nevertheless, microbial quality assessment indicated no Escherichia coli on edible parts of carrot or eggplant irrigated with wastewater. Carrots were expected to have the poorest microbiological quality. Therefore carrot root bacterial quality must be further examined. Results on eggplant are not surprising as these vegetables are somewhat far from the ground and they receive significant solar radiation which acts like a disinfectant. Lettuce from wastewater treatment plots, however, exhibited presence of Escherichia coli, meaning that lettuce is likely to be contaminated by pathogens. However, no pathogens were detected neither on crops irrigated with fresh water nor on those irrigated with wastewater. Heavy metals results demonstrated that the crop's consumption did not involve higher risk for consumers when the vegetables were irrigated with domestic wastewater, in comparison with fresh water irrigation. Kossodo treatment plant receives mainly industrial wastewater, which are characterized by high levels of sodium and bicarbonates. The treated wastewater supplies a market garden in which space has been defined for the study of this second component. The main objective was to assess the impact of treated wastewater on soil quality during two years of irrigation. Early in the second year, the presence of black spots, suspected to be black alkali (dissolved organic matter), appeared at the surface of plots irrigated with treated wastewater. These indications led to put forward the hypothesis of alkalinisation/sodisation on soil receiving wastewater. The methodological approach used was based on in situ measurement of infiltration at the end of the second year of irrigation, supplemented by shrinkage curve modelling and chemical analysis. The hypothesis of an alkalinization/sodisation and dissolved organic matter (black alkali) presence in plots irrigated with treated wastewater were validated by the chemical analysis. Shrinkage curve modelling showed a reduction of the structural porosity on wastewater irrigated plots. The reduction was more marked in the subsurface horizons than in surface, which is probably caused by dispersed clay leached in depth. These structural changes were confirmed in situ by an infiltration capacity greatly reduced on plots irrigated with treated wastewater, compared to control plots (irrigated with fresh water) where the infiltration capacity is higher and comparable to that of non-irrigated soil. The study confirmed the fertilizing value of domestic wastewater while emphasizing the need to concentrate future investigations on sustainable effluent/fertilizers management. The sanitary assessment with different crops regarding their respective distances to the soil was very useful since it showed the strong interaction of soil microbial community on the crop microbial quality. It also revealed the importance to determine a faecal indicator for the crop, specifically related to wastewater contamination. Soil quality assessment reiterated the necessity to verify wastewater quality before its reuse in agriculture. In the case of this study, the sodic and alkaline properties of the industrial effluents make them definitively unfit for irrigation.

EPFL2009