Document(s) 12 of 19

¹International Development Research Centre (IDRC), Ottawa, Canada
²Institut Fondamental de l’Afrique Noire (IFAN), Dakar, Senegal

Abstract

Urban vegetable production in Dakar plays a significant role in fighting poverty, as it provides both income to farmers, and a source of nutritious food for the poor. However, the irrigation of these crops is cause for concern, as many farmers prefer untreated wastewater to freshwater due to the higher profits stemming from its greater availability, reduced fertiliser costs, and higher yields and production. While using such water, few take precautions to protect their health, and 60% are infected with intestinal parasites. The practice also poses a risk to public health, as three of the main crops produced (lettuce, tomatoes, and onions) are often or exclusively eaten raw. Thus, while there is a growing willingness among policy-makers to encourage urban agriculture (UA), there is also the recognition that current irrigation practices are unsafe. Authorities looking to decentralise wastewater treatment need reassurance that community-level systems can be proven efficient and sustainable. It is recommended that action research be conducted that includes finding effective treatment systems, and that tests the feasibility of other management options such as increasing public awareness, using safer irrigation methods, and practising restricted irrigation. Additional research on the economic importance of UA is also necessary to encourage donors to fund research and development initiatives. Ultimately, action must be taken soon, or a repeat of the 1987 typhoid epidemic in Dakar could lead to backlash among consumers and policy-makers, with devastating consequences for both poor farmers and poor consumers.

Introduction

Senegal ranks 156^th out of 175 countries on the United Nations Human Development Index (UNDP, 2003), although its per capita gross domestic product (GDP) is US$1,500. Measures taken in 1994 to liberalise the economy, including currency devaluation and elimination of subsidies, have attracted investment and stimulated economic growth, but have also hit the poor hard. Real wages have declined, and a quarter of the population lives below the internationally recognised poverty line of US$1/day.

Furthermore, recent droughts have decreased the production of groundnuts, an important commodity that uses 40% of the cultivated land, employs 1.5 million farmers and makes up 10% of Senegal’s export earnings. The sector saw significant declines in the 1990s until 1999–2000, when it bounced back.

On average, Senegal receives 1400 mm annual rainfall but during the 1980s, rainfall declined significantly before stabilising in recent years (Gommes and Petrassi, 1996). The south receives more rainfall than the north, where only about 300 mm fall each year. The city of Dakar receives about 450 mm rainfall each year (RADI, 2002). However, 80% of this is concentrated in 4 months – July to October.

All of these factors – removal of subsidies on basic foodstuffs, unemployment arising from low commodity prices, and recent droughts – have threatened the food security of the poor. Poor rural migrants looking for work increasingly find themselves in Dakar, the largest city with a population of 1.9 million people, and the centre of economic power. With a growth rate of 4%, Dakar’s population is expected to reach 3.8 million by 2015. Although 80% of Senegal’s industry is located in Dakar (RADI, 2002), the city still has a 25% unemployment rate. Thus, to generate income and food, more and more people have set up market vegetable gardens, which provide income, and fresh, nutritious food for the urban poor. Because it is often more convenient, reliable, and profitable, many farmers use untreated wastewater for irrigation.

Since 1999, the International Development Research Centre (IDRC) has supported Environnement et Dévéloppement–Tiers Monde (ENDA) and the Institut Fondamental de l‘Afrique Noire (IFAN) to study wastewater use and urban agriculture in Dakar. IDRC first supported pilot research to identify which types of natural wastewater treatment systems would work best in Dakar. A second phase of the research project, upon which this case study is based, focused on developing two community-scale wastewater treatment plants, and a better understanding of the nature and impacts of urban gardening in Dakar. The team used GIS and aerial photos to outline the extent of UA in Dakar. For the entire production cycle, from on-site field plots to transport to the markets, the team gathered data using surveys including individual interviews and focus group discussions. Fifty farmers on three different sites were surveyed. Samples of UA produce, human waste (stool, urine) and blood of farmers were taken to assess health impacts. The study encompassed all three seasons in Dakar and analysed sites using groundwater (as a control) and untreated wastewater to make comparisons. The research results are presented in this chapter, which first describes the nature and extent of urban farming in Dakar and then outlines its health and environmental effects. This is followed by an analysis of the socio-economic factors involved, a description of the institutional and legal context, and a breakdown of other constraints to production. Finally, management and policy recommendations are outlined, and future research needs are identified.

Urban Agriculture in Dakar

Location, size, principal crops

Vegetable production in Senegal centres on the Niayes – shown in Fig. 10.1, a long, narrow fertile zone of land that stretches 250 km along the coast from Dakar to St. Louis. Its annual output is more than 100,000 t, worth US$18 million, and accounting for 80% of the country’s total vegetable production (Touré Fall and Salam Fall, 2001).

As shown in Fig. 10.2, within Dakar there are several major sites where urban gardening takes place. This study focused on the urban farmers in Pikine, which, with a total area around 650 ha, constitutes the largest urban agriculture site in or around Dakar. Known as les poumons de la ville (the lungs of the city), this large green space exists within the city as a result of policies first implemented by Leopold Sedar Senghor, the first president of Senegal. Despite its importance, the zone is threatened by both urban development and saline intrusion, and has shrunk by 56 ha (10%) over the last 30 years.

The primary crops grown are lettuce, tomatoes, onions and eggplant or aubergine. While some fruits are cultivated, vegetables are preferred because they grow faster and are more profitable. The total annual production is 39,000 t and constitutes 60% of the vegetables consumed in the city (ENDA–IFAN, 2002).

Of the vegetable plots in Dakar, 80% cover between 0.01 ha and 0.1 ha with an average of 0.05 ha, or 500 m². These smallholder plots are traditionally farmed using such hand tools as pitchforks, hoes and shovels (Touré Fall and Salam Fall, 2001).

Fig. 10.1. The Niayes of Senegal.

Fig. 10.2. Urban gardening in Dakar, enlarged from Fig.10.1.

Although Dakar has an Urban Plan and a 1964 Loi du Domaine National (LDN) [Republic of Senegal (National), 1964] land tenure is precarious, and many use land without title. Of the 380 farmers in Pikine, about 40% consider themselves owners with legal or customary title to the land, 6% lease it, and the remainder farm without any right to the land – a risky proposition. In 1999, municipal authorities expelled 50 farmers after discovering their plots near the airport. Also, without security of tenure, most farmers invest little in the land they cultivate.

Irrigation sources

Water supply, wastewater collection, and treatment are divided among three separate entities under the direction of the Ministère Hydraulique. Distribution has been privatised and devolved to Sénégalaise des Eaux (SDE). Operation and maintenance is controlled by Société National pour l‘Exploitation des Eaux (SONES), while the Office Nationale de l‘Assainissement (ONAS) operate sewerage services. SDE provides two main sources of water for Dakar – 20% comes from Lac de Guieres, where it is screened, clarified, and chlorinated, and 80% comes from groundwater at Thies, 80 km northeast of Dakar, where it is chlorinated before entering the distribution system.

A few farmers use water from the potable distribution network, but this is too expensive for most. The main sources of irrigation water are therefore céanes and untreated wastewater. Céanes are large, shallow hand-dug wells up to 3 m deep and 5 m in diameter, and are highly saline due to their close proximity to the coast. Untreated wastewater is often accessed by breaking into the mains that carry untreated wastewater, 180,000 m³ of which are generated daily in Dakar. Of this, about 66,000 m³, or 40%, is collected by the sewerage network. Only 4,000 m³, or a mere 6% of the collected wastewater is treated before discharge. The rest is discharged through cesspools and unlined septic tanks to the ground and eventually the sea, or directly into the sea through open drains.

The irrigation source varies at each site, depending on access. At Cambérène, farmers exclusively use céanes, but at Ouakam, untreated wastewater is the only source. In Pikine, some of the farmers have access to both céanes and untreated wastewater, and the wastewater actually helps to access the céane water. The deeper the céanes are dug, the more saline they become, eventually becoming so saline that their water is unfit for irrigation. Thus, some farmers dilute water from the céanes with wastewater, which is less saline, by channeling flow from the broken sewerage mains.

In most cases, farmers wade directly into the céanes, filling watering cans for irrigation. Wastewater either drains naturally from broken pipes, or is directed by a hose into a depression or a céane, from where it is collected. Using these manual techniques, irrigation takes up to 60% of the farmers’ time (Navez, cited in Niang, 1999). In a few cases, farmers use hoses to distribute wastewater – one rare farmer in the study had even installed an electric pump.

Analysis of the raw wastewater at each site showed expected results (Table 10.1) with some variance mainly due to the condition of the mains, i.e. how much storm water was in the system. Not surprisingly, the number of faecal coliform (FC), an indicator of pathogenic bacteria, far exceeded the 1000 FC/100 ml of water WHO standard required for unrestricted irrigation. Furthermore, the raw wastewater contained the larvae, eggs, or cysts of several protozoa or worms – above the WHO standard of 1/l. Some of the céanes also showed faecal contamination, suggesting that wastewater from the broken sewer mains is infiltrating into the groundwater. The most commonly found parasites are Ascaris lumbricoides (roundworm), Entamœba coli (which causes amoebic dysentery) and Strongyloides stercolaris (threadworm) (ENDA–IFAN, 2002).

Only trace amounts of most heavy metals were found, except for copper (Cu) and zinc, (Zn) which had levels only slightly higher than recommended (Rodier, 1996).

The characteristics of the wastewater vary markedly on separate days of the week. In Senegalese culture, certain days are preferred for laundry, and on these days, detergent levels are high. On Fridays, mosques discharge ablution water from Jumma (Friday Prayer), resulting in increased dilution and lower concentration levels for all parameters.

Table 10.1. Water quality^a from various sources in parts of Dakar, Senegal.

^a. TSS = total suspended solids; COD = chemical oxygen demand; K = potassium; NO₃ = nitrate; NO₂ = nitrite; P₂O₅ = phosphate; FC = faecal coliform.

Crop productivity using wastewater

Depending on the growth period of their crops, farmers on average needed only 10 mm/day of wastewater for irrigation, compared to 12 mm/ day for céane water (Gaye and Niang, 2002). Although the vigorous plant growth resulting from the nitrogen in wastewater would generally require even more water, this need is offset by the increase in soil organic matter that boosts its water-holding capacity.

The study found that, except for lettuce, most crops produced higher yields when watered with untreated wastewater without the addition of artificial fertilisers, than when farmers used piped potable water with added artificial fertilisers. For farmers using artificial fertilisers, these costs represent an average of 23% of their total farming costs (ENDA–IFAN, 2002). Possibly for this reason – higher yields from the same plot size – farmers who use raw wastewater have an average plot size of 0.02 ha, compared to 0.05 ha for those who use céanes water (ENDA–IFAN, 2002).

Table 10.2. Parasite prevalence at Ouakam and Pikine.

Moreover, the results also show that wastewater irrigation reduces the growth period for crops. For example, the typical period of maturity for lettuce is approximately 30 days, but drops to 20–25 days when using raw wastewater. Given that the usual growing season is November to April, this makes nine harvests possible instead of six – an increase of 50%. One drawback is that although wastewater-grown lettuce is larger, it is also less dense, yielding only 40 t/ha compared to 45 t/ha. Additionally, such lettuce spoils faster and must be sold within 24 hours of harvest (Faruqui, 2001). Similar results were found with aubergines.

About 75% of urban farmers farm year-round – the remainder work on their gardens 10 months of the year. However, 99% of farmers using wastewater practice their trade year-round. One reason for this is that wastewater-irrigated lettuce is more resistant to insects and the plant disease they cause – both of which are more prevalent during the wet season – and thus it can be grown successfully year-round. It is not yet known whether other crops exhibit this characteristic.

For all of the above reasons, the farmers interviewed have a definite preference for using raw wastewater, as it simply translates into higher annual profits. Those using wastewater reported earning very good profits during the dry season, when the price for lettuce is high due to limited supply. One farmer in Patte d’Oie said: “If I could have a permanent supply of raw wastewater for irrigation . . . without being bothered by the health authorities, I could feed (support) more than 30 people.”

Health and Environmental Effects

Health effects

Many farmers suffer from ill health because of their direct contact with wastewater – the lack of footwear or gloves makes them vulnerable to infection by parasites, transmitted either orally (placing unwashed hands in the mouth) or through the skin (parasites burrowing directly into the body).

At Ouakam, where only wastewater is available, 60% of farmers were infected with intestinal parasites. At Pikine, where water sources are mixed, the level of infection was lower – about 40%. The most common parasites found were Ascaris ascaris (roundworm), Trichuris trichiura (whipworm), and Strongyloides stercoraltis (threadworm). The eggs or larvae of all three worms, which live in the intestine, are passed through the faeces. In the case of roundworm and whipworm, reinfection is then oral, by ingesting food contaminated by the infective eggs. Threadworm, like hookworm infects by penetrating the skin of the feet or hands of farmers working in fields irrigated with wastewater.

A high density of Plasmodium falciparum, a parasite that causes malaria, was found in four farmers who irrigated céanes at Pikine. Malaria is endemic to the area, with many Anopheles mosquitoes present. Farmers using raw wastewater for irrigation were not infected, probably because raw wastewater is usually too dirty for mosquito larvae to thrive.

Sanitary quality of products

Recently harvested wastewater-irrigated plants for sale were found to be contaminated with amongst other pathogens, Amoebae, Ancylostoma, and Ascaris which cause amoebic dysentery, hookworm, and ascriasis (roundworm), respectively (Niang, 1999). Given that some of the farmers are also infected with whipworm (see above), eggs of this pathogen are also present in produce irrigated by wastewater. In the past, even more serious pathogens have been found on produce for sale in Dakar. The 1987 epidemic of typhoid caused by Salmonella typhi made 400 people in Dakar seriously ill. The disease originated from the consumption of vegetables contaminated with untreated wastewater, and mostly affected urban farmers who had used insufficiently treated wastewater for irrigation.

Almost half of the farmers indicated they were aware of the health risk posed by working with wastewater. However, only a handful used precautions such as wearing boots and gloves, or avoided direct contact. Furthermore, less than 15% were aware that the 1987 outbreak was caused by untreated wastewater use – in fact, many argued it was caused by other factors. Some of those unaware of the health risks are also under the impression that when water is clear, it must be clean.

For consumers, the main concern is over lettuce, onions, and tomatoes, which are most often eaten raw. Without close examination, it is impossible to tell the difference between products irrigated with water from different sources that are sold side by side. Rinsing is insufficient protection – health risks must be mitigated either by disinfecting, using a solution of sodium hypochlorite (bleach) or potassium permanganate, or by cooking. According to the ENDA–IFAN survey, a surprisingly high percentage of consumers (about 70%) are aware of health risks, and either disinfect or eat only cooked vegetables, although other surveys have found only 44% disinfect their vegetables (ENDA–IFAN, 2002). Of course, these solutions also carry risks if too high a concentration of disinfectant is used. Moreover, even using the higher figures of the more recent study, a significant minority of consumers (30%) are unaware of the risks, or take no protective measures.

For people living near the pilot wastewater treatment plants in Castor and Rufisque, an equal concern is the potentially negative health impacts from the treatment plants. To assuage these concerns, the research team carried out epidemiological studies on people, including children, living near the sites. The results found no significant differences in their health from that of the general population. The main concern is diseases transmitted by mosquitoes, including malaria, yellow fever and elephantiasis. During the study period, mosquito species causing malaria (Anopheles gambiae) or yellow fever (Aedes aegypti) were not present in the ponds, although Culex mosquitoes, which transmit elephantiasis, were found. Mosquitoes tend to be associated with the last pond in the series of basins that make up the treatment system, where the water is cleaner. Possible solutions to reduce mosquitoes include placing fish to eat the larvae in the last basin, or adding an additional shallow pond with a gravel bed.

Environmental effects

Very little data exist on other environmental impacts of untreated wastewater irrigation, such as impact on soils or drinking water. Certainly, most of the shallow groundwater is contaminated with pathogens. However, this is because less than 40% of Dakar is connected to the sewerage network, and even the existing infrastructure is in disrepair. Wastewater is also unlikely to affect drinking water, since the céanes are too salty to serve as a drinking water source.

Somewhat surprisingly, the research team collected no data establishing reduced yields, and only minimal data on soil damage associated with a build-up of oil, grease and suspended solids arising from repeated, long-term wastewater irrigation. This is probably due to the nature of the sandy or peat soils, which have large interstices between their soil particles. Nevertheless, over time this could prove to be a problem – only 27% of farmers were aware that repeated wastewater irrigation can impede infiltration by blocking pores between soil particles, eventually modifying soil structure.

Given that the majority of the catchments showed very little industrial waste in wastewater, scarce evidence of heavy metals such as cadmium (Cd), mercury (Hg), chromium (Cr⁶⁺), nickel (Ni), or manganese (Mn), and only moderate levels of Cu and Zn, there is no evidence yet of other serious associated longterm health or environmental effects. The one known exception is in Rufisque (the location of the IDRC-supported treatment systems), where discharges from the Marisel tannery have increased salinity in the wastewater to the point where it is unusable for irrigation. Levels of discharged Cr⁶⁺ may also be high, although this has yet to be detected.

Socio-economic Characteristics of Urban Farming

Socio-economic profiles of farmers

Almost 90% of the surveyed farmers are men, mostly under 45 years old, and the primary wage earners in their families. This is in contrast to other African cities where urban farmers are mostly women. However, Dakar female family members do help during the harvests and act as intermediaries, selling crops in the market.

Of the urban gardeners 58% are former farmers who migrated to Dakar from rural areas, and they farm because it is familiar and profitable. For 75%, it is their main occupation. All ethnic groups are represented and the practice is not restricted to the poorest groups.

The farming systems differ widely, showing wide variability in plot size, intensity, and profit, and depend on various factors, including access to water or wastewater, socio-economic level, proximity to markets, land tenure, soil quality, and whether or not farming is the principal occupation.

Urban farmers in Dakar are partially organised, as some are associated with or part of the Groupes d’intérêt economique (GIE). GIEs are community-based economic associations that work to develop small-scale enterprises. GIEs help collect funds to operate the sewerage system in Castor and Rufisque, and help organise some of the UA farmers in Pikine.

Benefits

Crops are largely intended for the market, but a significant amount is for home consumption. The researchers were challenged in trying to make estimates of the economic value of this production, because while the farmers interviewed stated they earn reasonable profits, they were either unable or unwilling to give precise figures. Based on the average response (through oral surveys), the farmers earn net revenues (profit) of about FCFA 43,000 (US$73)¹ per harvest. Given that each farmer’s plot is on average 0.05 ha, the profit per harvest is about US$1460/ha.

¹ Based on 17 July 2003 exchange rate of US$1 = CFA Francs 587.76.

Using the four most common crops, the study found that on average farmers harvest five crops per year. The net average annual profit for each farmer is then FCFA 215,000 (US$365), or FCFA 589 (US$1)/day – equal to the international poverty line. While this figure may seem low, the profit generated may be less important if urban farmers become completely self-sufficient in vegetables. Considering that food purchases by the poor in the urban areas of developing countries can be as much as 80% of their income, this is a considerable improvement in family wealth (Egziabher et al., 1994). Furthermore, if the farmers are among that quarter of the population already at the international poverty line, the profit earned essentially doubles their income. However, these figures probably underestimate their income. Some of the urban farmers indicated they earned profits of up to FCFA 300,000 (US$510) per harvest, or FCFA 1.5 million (US$2,552) annually, and it is likely that their annual net revenues are closer to this figure. In addition, it is unlikely that farming provides the sole contribution to household income, as some farmers may undertake other activities, and other family members may also be working.

In addition to direct income benefits from UA, there are also indirect economic spin-offs. Although not yet directly estimated, anecdotal evidence indicates that urban gardening generates a variety of other economic activities related to food production, marketing, and the sale cycle. This helps create demand in sectors that produce such goods as tools and seeds, and such service sectors as transport.

Costs

As with benefits, it was difficult to assess input costs due to the informal nature of urban gardening and the reticence of some farmers to respond to surveys. A preliminary estimate of cost per farmer per plot per harvest (both for those using raw wastewater and water from céanes) is:

• Soil preparation – FCFA 8,682 (US$15)
• Equipment – FCFA 10,300 (US$17)
• Fertiliser and pesticides – FCFA 4,021 (US$7)
• Seeds – FCFA 7,140 (US$12)

A total cost per farmer per plot per harvest is thus about FCFA 30,000 (US$51), or, using an average estimate of five harvests/year, US$255/year. As noted earlier, farmers who do not use wastewater pay up to 23% of their total input costs for pesticides and fertilisers. In this example, it would amount to about FCFA 9,200 (US$16) – or twice what farmers using wastewater pay for fertiliser.

Furthermore, labour, except for that involved with soil preparation, is not fully accounted for above. Working backwards from the profit figures presented earlier, the estimated average gross revenue based on farmer’s responses may be in the order of US$255 (costs) + US$365 (net income), or US$620 annual gross income.

Institutional and Legal Framework

Notwithstanding problems of land tenure, the practice of UA is generally encouraged in Senegal. In 1984, the State began incorporating horticulture into national economic plans and development strategies, and this culminated in 1994 in the creation of the Department of Horticulture. Its aim is to support small-scale agriculture through credit programmes, training, and access to tools, fertilisers, and pesticides; but actual financial support has been negligible and the activity remains firmly in the informal sector. At the municipal level, seven mayors (including Pikine’s) and city councillors from West Africa signed the Dakar Declaration in March 2002 (IDRC, 2002), which stated their explicit support of UA. Although the Declaration specifically noted the widespread practice of wastewater use and its health risks, the municipalities are not yet able to regulate UA, or to provide management options for mitigating risks.

While UA is theoretically encouraged, unrestricted wastewater use is not, and is banned by the National Health Act (1983) and the Environment Act (2001). The Health Act (Article L–41) stipulates that the ‘deposit of waste, septic tanks discharge, garbage, sludge, faeces are prohibited on all lands where fruit and vegetables consumed fresh and cultivated and where edible parts come into contact with this waste’. Moreover, organic fertilisers like manure and compost can only be placed on crops up to one month prior to harvest. Previously, both national and municipal officials had attempted to enforce the law, but efforts proved futile and not much is done now. For example, at the behest of health officials, ONAS repaired pipes, but farmers simply broke them again.

However, there is evidence that both state and municipal authorities are willing to confront the reality of wastewater use. For instance, the Ministère Hydraulique‘s Projet Eau Long Terme (PLT) 5-year plan for 2002–2007 recognises the potential of wastewater use as an effective instrument for managing water demand. Notably, ONAS has also recognised its value, and is prepared to support decentralised wastewater use systems, so long as health risks are minimised. ONAS has envisioned creating 160 small-scale, community-operated wastewater treatment systems, and 60,000 on-site treatment systems in the country – with the caveat that it first needs to be convinced of the efficiency and sustainability of such systems. Similarly, the Dakar Declaration explicitly recognises both the benefits and risks of widespread wastewater use. All of these developments contribute to a policy climate from which viable approaches to protect farmers and the public health could emerge.

Constraints to Sustainable Urban Agriculture Production

Environmental and public health issues

Environmental effects may become a growing problem, but significant restrictions would also arise from a serious health crisis such as the 1987 typhoid epidemic – global public awareness of health impacts will spread faster and reach more people than in 1984, due to the advances in information and communication technologies made in the last 20 years. In effect, such an episode would quickly generate worldwide publicity through the Internet, and magnify local knowledge of the issue (witness the 2003 SARS outbreak) – making a backlash more likely to occur.

This blowback could result in a possible crackdown on producers by health inspectors, and a temporary repair of broken sewers by ONAS which could have devastating impacts on urban farmers and the urban poor.

Insecurity of land tenure

Short of a major health epidemic, a far greater obstacle to UA is insecurity of land tenure. Large, green, city spaces within developing countries are rare, and Dakar’s situation is threatened by the development of a new golf course and private homes adjoining the site of Technopole, a business park already built on the aquifer recharge zone of the Niayes. Furthermore, another part of the Niayes, east of National Highway 1 and west of the Dalifort neighbourhood is being developed by two urban development agencies – Société Nationale des Habitats à Loyer Modéré (SNHLM) and Société Centrale d’Aménagement des Terrains Urbains (SCAT–URBAM).

As urban planning and programming of the city does not include UA, small-scale producers are aware their land may be expropriated at any time by the state for projects in the ‘public interest’, and thus do not invest heavily in their land. Although La Loi sur le Domaine National (LDN) suggests that ‘la terre appartient en premier lieu à celui qui la cultive’ (those that cultivate the land have first rights to it), economic interests sometimes override the law (ENDA–IFAN, 2002). Also, development sometimes provides low-income housing – an acute need in Dakar. This limits the possibilities for maintaining UA plots in the Niayes, and means planners face the challenge of moderating competing interests over the productive green areas of Dakar.

Recommendations

Dakar is now at a crossroads, as authorities search for feasible and effective ways to regulate existing irrigation practices and to reduce their harmful effects. The opportunity to implement guidelines from the World Health Organization (WHO) for the treatment and safe use of wastewater for agriculture (Mara and Cairncross, 1989) should now be explored together with other management options.

Treat wastewater

The main recommendation is to treat domestic wastewater to meet WHO guidelines for unrestricted use. Non-functioning treatment plants, abandoned due to a lack of capacity and funds, already exist at Pikine and Patte d‘Oie. Parts of these plants could be reused in a simple, low-cost system. Furthermore, at Pikine there are large mares or ponds that could be used as reservoirs to allow pathogens to die off, thus rendering the wastewater suitable for unrestricted irrigation (Redwood and Faruqui, 2002).

Over the last 3 years, IFAN has been pilot testing two aquatic treatment systems: one using water lettuce (Pistia stratiotes) in Castor, and the other using bulrushes (Typha spp.) along with tilapia in Diokoul. Research progress has been slow due to external conditions, but results so far have been encouraging – the natural treatment plants are clearly more robust than mechanical systems. First built in 1994, they survived for 5 years without maintenance or harvesting of the aquatic plants, and they continue to operate, albeit at less than optimal efficiency. In contrast, a mechanical treatment plant would probably have experienced complete failure over such a long period.

Results are also promising in terms of both biochemical oxygen demand (BOD) and total suspended solids (TSS) removal, since heavy metal levels in the influent of both plants are safe. The main problem is pathogen levels, which pose the greatest threat to public health. In both Castor and Diokoul, faecal coliform levels in the effluent exceeds 1000 FC/100 ml, and intestinal pathogens are present, meaning the wastewater should not be used for unrestricted irrigation, although it could be used for restricted irrigation. This stems from inadequate residence time for pathogen die-off, and a second phase of the research project will focus on bringing the existing treatment systems in line with the WHO guidelines. These include a different orientation to increase hydraulic retention time. One important aspect of this study will be to map potential industrial contamination that may be preventing the re-growth of aquatic plants.

While initial results are encouraging, and capital and operations and maintenance costs to date have been low, this is no guarantee that the proposed treatment systems will be cost-effective and sustainable in achieving a water quality suitable for unrestricted irrigation. That possibility notwithstanding, it is still recommended that some level of treatment be provided to reduce health risks, and remove oil, grease, and suspended solids that could harm plants and ultimately modify soil structure. However, this does necessitate an investigation of other means to lower risks.

Other management options

The benefits and costs of the following proposed non-treatment management options will be studied in the next phase of the research project.

Increase public knowledge and awareness

Education programmes for farmers, the public, and municipal officials are essential complements to other risk-reduction tools. The findings in this paper could form the basis for awareness-raising strategies that focus on benefits, risks, and mitigation strategies, designed in line with WHO guidelines. In order to ensure that wastewater management is relevant and has a lasting effect, awareness strategies need to be comprehensive and broad-based, i.e. using such tools as schools and media campaigns, along with non-secular tools.

Culture, including religion, clearly influences how people perceive and manage a resource, and this is increasingly recognised by such organisations as the United Nations Environment Programme (UNEP), the Food and Agriculture Organization of the United Nations (FAO) and the WHO, which have drawn on this connection for programmes in Afghanistan and Jordan. The degree to which people are influenced by religion varies among and within countries, but given that Senegal’s population is predominately Muslim, there is an opportunity to use Islamic teachings to encourage safe irrigation practices. In Dakar, one of the main zones of wastewater use, Ouakam, is close to La Mosquée de la Divinité, and more than 40% of the children in the area attend Islamic school. As indicated in Water Management in Islam (Faruqui et al., 2001), explicit support for water conservation is found in Islamic religious texts that place a great premium on cleanliness; wastewater use is allowable, but only when it has been treated sufficiently to protect public health.

Socio-cultural beliefs may also provide indirect opportunities, as farmers could be asked not to irrigate on laundry day (or the day after) because of the high levels of detergent in the water. Instead, they could try to irrigate on Fridays (after Jumma) when the water is more diluted following ablutions at the mosques. In Jordan, an IDRC-supported project on greywater use is reusing the wudu wastewater to irrigate olive trees in the mosque’s courtyard. There is no reason why wudu water cannot be used from every single mosque in the world with a patch of land, including those in Dakar.

Use safer irrigation methods

Irrigation methods can affect both the degree of plant contamination and the types of precautions farmers can take to protect their own health. The current method of irrigating with watering cans intensifies the risk of contamination because droplets touch the plant leaves. The research project confirmed that lettuce watered this way is more contaminated by faecal coliforms and Streptococcus than lettuce irrigated by furrow (ENDA–IFAN, 2002). However, hose use depends on topography unless farmers install pumps. Where feasible, distribution lines could be fitted with drip irrigators so the wastewater wets the root zone directly without contacting the plant leaves. As an added benefit, this also reduces water consumption per unit area, but probably not in aggregate terms if the irrigated area expands.

In terms of implementation, micro-credit schemes exist in Dakar that could help make such basic tools as trickle irrigation systems, small pumps, and protective gear available to urban farmers. The Department of Horticulture could become more active in propagating these low-tech preventative methods. However, insecure land tenure means that farmers are reluctant to make greater investments in their enterprises, even though improved irrigation methods would improve their personal health.

The timing of wastewater use can also reduce impacts on health. WHO guidelines recommend that wastewater irrigation should be stopped 2 weeks before harvest (Mara and Cairncross, 1989). For those without an alternative water source, irrigation should be stopped at least 2 or 3 days before harvest, because this reduces pathogens on the leaves of produce. The use of setbacks (up to 300 feet) should also be considered for larger plots within urban areas (OAS, 1997).

To protect farmers, health authorities could make wearing boots and gloves when irrigating mandatory – the problem however is that farmers do not like wearing gloves in hot weather, and most céanes are deeper than boot length. Under the current passive method of collection and distribution, i.e. allowing wastewater to drain into the céanes and watering with cans, wearing gloves and boots is unlikely to be feasible, although even now, farmers could at least wear shoes when walking in their fields. As an alternative, wastewater could be pumped up to raised treatment and storage tanks, from where it could flow into the fields via hoses or furrows or be collected in watering cans from standpipes. However, until the feasibility of decentralised treatment is proven, this approach will be limited to the IDRC pilot test during the next phase of research. This example however, illustrates the point that treatment options and other management options are not mutually exclusive – in fact they depend on each other.

Crop restrictions

Given that many of the crops watered with wastewater are some of the most profitable, it may be difficult to enforce crop restrictions. Nevertheless, until viable treatment systems are in place, this practice should be discouraged, even if focusing on vegetables, such as aubergine that are eaten cooked, lowers profits. However crop restrictions alone have proven impractical in other jurisdictions, so such measures must be combined with a methodical public awareness and farmer education programme. Additionally where regulation fails, markets may succeed, as there may be reduced consumer demand to purchase wastewater-irrigated raw vegetables, if consumers realise the hazards.

Improve institutional coordination

The current research has identified a lack of collaboration between such non-governmental institutions as the farmers themselves, groups representing them, e.g. Groupes d‘Intérêt Economique (GIE), and governmental organisations such as municipalities (the Commune of Dakar), and national departments such as the Ministries of Agriculture, Health, Urban Planning, and SONES. An important part of the next phase of the project will be regular meetings bringing all stakeholders together to brainstorm for mutually satisfactory solutions.

Treat infections

Another potential solution is medical treatment for farmers to assuage chronic health problems such as bacterial and worm infections (RUAF, 2002). Granted, such an approach is reactive rather than preventive, but until other solutions are better advanced, it may be the only way to protect farmers’ health. The benefits and costs of this approach will also be assessed during the next phase of IDRC research.

Conduct research

The informal and quasi-illegal nature of UA activity, and the cost and time required to do methodical research, means many findings only probe the surface. Although they provide qualitative data or trend directions, they do not fully answer questions, and indeed, raise new ones. Because of this, some of the above recommendations are tentative. As already noted, key research gaps must be addressed by meaningful research before such recommendations can be significantly implemented. These gaps include:

• Designing efficient and sustainable natural wastewater treatment systems
• Finding the best institutional policies and framework to help municipal and national institutions work together in support of urban farmers and to protect public health
• Testing the feasibility of non-treatment management options.

In addition, in order to attract increased donor and state funding (see below), the following information is required:

• Better economic estimates of the value of UA to emphasise its importance for poverty alleviation to donors and policy-makers
• More accurate estimates of the economic value-addition of wastewater use in urban agriculture.

Increased donor/state funding

Finally, donor and state funding is essential to help policy-makers strike a balance between protecting the public interest, the farmers, and the urban poor. ONAS in partnership with UN Habitat and the World Bank suggest that decentralised treatment and use is a serious option for wastewater management in Senegal. However, without additional funding, neither the treatment, nor other management options can be implemented. A real opportunity exists to seriously mitigate risks, provided funds are forthcoming.

Conclusions

Farmers prefer using wastewater to freshwater for irrigation, as they immediately see higher profits. However, few take precautions to protect themselves, and as a result, 60% of them are plagued with intestinal parasites. Additionally, the practice poses a significant public health risk, as three of the main crops are most often eaten raw. Urban agriculture itself is constrained by the insecurity of land tenure, as the constant threat of losing their land makes farmers unwilling to commit to major investments. Thus the potential for safer and more convenient irrigation methods, such as hoses fitted with drip irrigators, is limited.

While policy-makers have largely ignored UA in the past, they are increasingly encouraging its practice, while simultaneously attempting to discourage its dangerous use of raw wastewater. Policy-makers such as ONAS are emphasising treatment and are prepared to decentralise wastewater treatment to the community level, so long as efficient and sustainable systems can be identified. It is recommended that action research be conducted that balances both private and public needs, including testing for effective treatment systems. At the same time, the feasibility of such other management options as increasing public awareness, using safer irrigation methods, and practising restricted irrigation should also be explored. These treatment and non-treatment options are complementary, and unless action is taken soon, a repeat of the 1987 typhoid epidemic could lead to a backlash among consumers and policy-makers, with devastating consequences for both poor farmers and poor consumers.

References

Egziabher, A., Lee-Smith, D., Maxwell, D., Memon, P.A., Mougeot, L. and Sawio, C.J. (1994) Cities Feeding People. IDRC Books, Ottawa, Canada, 115 pp.

ENDA–IFAN. (2002) Valorisation des eaux usées domestiques dans l‘agriculture urbaine à Dakar Scientific Report 2. Cities Feeding People, International Development Research Centre (IDRC), Ottawa, Canada, 75 pp.

Faruqui, N. (2001) Trip report (December 2001), Senegal. Cities Feeding People, International Development Research Centre (IDRC), Ottawa, Canada, 10 pp.

Faruqui, N., Biswas, A. and Bino, M. (2001) Water Management in Islam. IDRC Books, Ottawa, Canada 135 pp.

Gaye, M. and Niang, S. (2002) Epuration des eaux usées et l‘agriculture urbaine. Enda-Tiers Monde, Dakar, 354 pp.

Gommes, R. and Petrassi, F. (1996) Rainfall Variability and Drought in sub-Saharan Africa. Food and Agriculture Organization of the United Nations (FAO), Rome, Italy. http://www.fao.org/waicent/ faoinfo/sustdev/EIdirect/EIan0004.htm [accessed October 2002]

IDRC (International Development Research Centre). (2002) The Dakar Declaration. http://network.idrc.ca/ ev.php?ID=24953_201&ID2=DO_TOPIC

Mara, D. and Cairncross, S. (1989) Guidelines for the Safe Use of Wastewater and Excreta in Agriculture and Aquaculture: Measures for Public Health Protection. World Health Organization (WHO), Geneva, Switzerland, 187 pp.

Niang, S. (1999) Utilisation des eaux usées brutes dans l‘agriculture urbaine au Sénégal: Bilan et perspectives. In: Smith, O. (ed.) Agriculture urbaine en Afrique de l’Ouest. IDRC Books, Ottawa, Canada, pp. 101–115.

OAS (Organization of American States). (1997) Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean. OAS, Washington DC, 323 pp.

RADI (Réseau Africain pour le Développement Intégré). (2002). Utilisation des eaux usées dans l‘agriculture urbaine en Afrique de l‘ouest, RADI, Dakar, Senegal, 58 pp.

Redwood, M. and Faruqui, N. (2002) Trip report (May 2002), Senegal. Cities Feeding People, IDRC, Ottawa, Canada, 30 pp.

Republic of Senegal (National). (1964) Loi du Domaine National no. 64–46. Government Printer [Laws], Dakar, Senegal.

Rodier, J. (1996) L’analyse de l’eau : eaux naturelles, eaux résiduaires, eau de mer. Dunois, Paris, France, 1383 pp.

RUAF (Resource Centre on Urban Agriculture). (2002). Agricultural Use of Untreated Urban Wastewater in Low Income Countries. E-conference, http://www.ruaf.org/ [accessed November 2002]

Touré Fall, S. and Salam Fall, A. (2001) Cités horticoles en sursis?: l‘Agriculture urbaine dans les grandes Niayes au Sénégal. IDRC Books, Ottawa, Canada, 126 pp.

UNDP (United Nations Development Programme). (2003) Human Development Index, http://www.undp.org/hdr2003/ [accessed July 2003]

Document(s) 12 of 19