Document(s) 11 of 19

Abstract

In Ghana, urban sanitation infrastructure is poor and only a small portion of the (primarily domestic) wastewater is collected for treatment. The bulk ends up in drains and nearby water bodies and is used by urban and peri-urban vegetable farmers for irrigation. Open-space urban and peri-urban vegetable farming is market-oriented and depends on water availability. It not only supports the livelihoods of many farmers and traders but also contributes significantly to the supply of perishable vegetables to cities. However, high contamination levels, especially pathogens, have been recorded in most irrigation water sources as well as on irrigated vegetables. Because wastewater irrigation is illegal, farmers are periodically expelled from their plots. As any significant improvement of the urban sanitation infrastructure is financially constrained, research into strategies for safe wastewater use that considers both health risks and farmers’ livelihoods is in progress. The aim is to contribute to the sustainability of urban vegetable production systems and their benefits in West Africa.

Background

Ghana lies at the shores of the Gulf of Guinea in West Africa. To the north, it borders Burkina Faso, Togo to the east and Côte d’Ivoire to the west (Fig. 9.1). It has a population of about 19 million, growing annually at the rate of 2.7%. About 44% of Ghana’s total population lives in urban areas. Some urban centres have annual growth rates as high as 6%, more than twice the country’s average rate (Ghana Statistical Services, 2002). This includes ‘Mega Accra’ that encompasses Accra, Tema and Ga districts with 2.7 million inhabitants and Kumasi with 1.0 million inhabitants. The overall national population density is 79 persons/km² (Ghana Statistics Services, 2002). Agriculture is the mainstay of the Ghanaian economy, contributing 36% of the gross domestic product (GDP) and employing 60% of Ghana’s labour force. The average annual per capita income of those employed in agriculture is estimated at US$390.

Annual rainfall ranges from 800 mm in the coastal areas to 2,030 mm in the southwestern rainforests. Table 9.1 summarises climatic conditions in the synoptic stations of Accra (southern belt), Kumasi (middle belt) and Tamale (northern belt) (Agodzo, 1998). The country’s surface hydrology comprises three main river basins: the Volta basin that covers about three-quarters of the country’s surface, the southwestern and the coastal basin systems.

Fig. 9.1. Map of Ghana and its administrative regions.

Status of Urban Wastewater Disposal and Treatment in Ghana

Sanitation and wastewater generation

About 63% of Ghana’s population has sanitation coverage, which is more than the West Africa average of 48% (Fig. 9.2) and similar to the average of eastern (62%) and southern Africa (63%) (WHO et al., 2000). While most countries in West Africa (like Senegal) show a very high disparity in provision of sanitation services between rural and urban areas, Ghana has a good balance with 62% coverage in urban areas and 64% in rural areas. According to Agodzo et al. (2003) the total amount of grey and black wastewater currently produced annually in urban Ghana has been estimated as 280 million m³. This wastewater is derived mainly from domestic sources as Ghana’s industrial development is concentrated along the coastline where wastewater, treated or untreated, is disposed of into the ocean. In Ghana, collection and disposal of domestic wastewater is done using:

• Underground tanks such as septic tanks and aqua-privies, either at industrial facilities or at the community level and then transported by desludging tankers to treatment works or dumping sites
• Sewerage systems
• Public toilets
• Pit and improved latrines.

Table 9.1. Mean annual climate data of Accra, Kumasi, Tamale.

Source: Agodzo, 1998.

Less than 5% of the households in Accra and Kumasi are connected to piped sewerage systems, while 21% use floodwater drains (gutters) as open sewerage that ends up in nearby water bodies. Some of the urban dwellers discharge their faecal waste into septic tanks while kitchen and other wastes from the home are usually directed into the nearest open drain. As the majority of the urban drains are open, they often serve as defecating areas for households that do not have adequate sanitation facilities. According to the national population and housing census carried out in 2000, one third of all households in Ghana use public toilets, reflecting the absence of toilet facilities in many dwelling places. Pit latrines continue to be used in 22% of all households but an improved version, the Kumasi Ventilated Improved Pit (KVIP), is being promoted and its use is expected to rise from the current 7%. Bucket latrines (4%) are being phased out because they are not hygienic. It is quite striking that more than 25% of all households in Ghana have no toilet facilities, with numbers increasing to about 70% in the three northern regions. Water closets (WCs), considered to be modern toilet facilities, are used by only 9% of the households, most of them located in Accra and Kumasi.

Fig. 9.2. Regional sanitation coverage in five West African countries. Source: Adapted from WHO et al., 2000.

Thus, the majority of the population in urban Ghana does not have appropriate means to manage wastewater and the costs of putting in place the required infrastructure to effectively collect and dispose of all urban wastewater are excessive.

Wastewater Treatment

More than half of all wastewater treatment plants in Ghana are in and around Accra (EPA, 2001). Two administrative regions (Brong Ahafo and Upper West, Fig. 9.1) have no treatment plant, despite having several important cities and towns. But even where treatment plants are available, less than 25% (primarily in the Greater Accra, Ashanti and Eastern regions, and mostly small-capacity and/or privately owned plants) are functional (Fig. 9.3).

A few years ago, a large modern biological treatment plant started operation at Accra’s Korle Lagoon; but, it handles only about 8% of Accra’s inner-city wastewater from domestic and industrial sources. The system has a capacity three times greater than that it currently uses, but is constrained by the small urban sewerage network. Only about 10% of the Accra’s wastewater is collected for some kind of treatment.

Fig. 9.3. Status of wastewater treatment plants in Ghana. Source: Adapted from EPA, 2001.

Equally disastrous is the situation of septage and night soil treatment. There are only a few low-capacity treatment facilities (usually stabilisation ponds) functioning in most cities. To cite just a few examples: Over the last few years, Kumasi’s main faecal sludge treatment plant was receiving an average of 180–500 m³/ day, which is less than 5% of the total faecal sludge produced in the city. The Waste Management Department attributes this low percentage mainly to vehicle breakdowns. However, the treatment ponds have been filled beyond capacity for years, often without desludging for many months and with faecal sludge overflowing to nearby rivers without treatment. The situation is similar in Accra with two sites loaded beyond capacity. The ocean is the third semi-official site, receiving about 40% of the excreta produced in the city. In Tamale, the first plant is still under construction while faecal sludge continues to be dumped in natural depressions.

In Kumasi, a new plant has been built at Buobai, but it can only handle 200 m³/day and is already reaching its limit. Another pond facility is in preparation near a new landfill site. It is apparent that city sanitation services cannot keep pace with the high urbanisation rates (Keraita et al., 2003b). The general situation causes the authorities concern as shown in Kumasi’s 1996–2005 Sanitation Strategic Plan (Box 9.1).

Quality of Irrigation Water Used in Farming

Wherever space allows, urban and peri-urban agriculture take advantage of any water source, be it polluted or not, for dry-season or annual irrigated farming. As most of the wastewater is of domestic origin, faecal coliforms are the contaminants of primary concern. Heavy metal levels in water bodies in and around Ghana’s urban centres are not elevated (McGregor et al., 2001; Mensah et al., 2001; Cornish et al., 1999). These studies also showed that inter-seasonal variations of water quality especially after the first heavy rains can be high, hence the need for long-term monitoring.

The main focus of the on-going water quality monitoring by the International Water Management Institute (IWMI) has therefore been on nutrients and microbiological contaminants in irrigation water sources, which in most cases exceed the WHO guidelines significantly (Keraita et al., 2003b). In Kumasi, faecal coliforms typically reach values of 10⁶–10⁸/100 ml while total coliform levels often range from 10⁸–10¹⁰/100 ml. Lower faecal coliform counts of 10⁴–10⁶/100 ml were measured at some urban farming sites in Accra and Tamale. At one site in Accra piped water is available for irrigation; at another, water from a small treatment pond¹ is used. In Tamale water from a broken sewage treatment plant is used for irrigation.

¹ This is the only site in the country where ‘treated’ wastewater is used by six farmers. The quality of the water, however, is not much different from other (polluted) sources.

Box 9.1.

‘The current system of human waste management in Kumasi is inadequate; waste removed from the public and bucket latrines ends up in nearby streams and in vacant lots within the city limits creating an unhealthy environment. Many government offices, schools and private institutions require improved sanitation facilities. Industrial effluent from the breweries, leachate from sawmills and waste oil spillage from the vehicle repair complex at Suame are also discharged into receiving waters without treatment. The stormwater drainage system is essentially an open sewer, which discharges into the Subin, Aboabo and Sissai rivers, and as a result the beneficial uses of these rivers (domestic water supply, irrigation, livestock watering and recreational activities) are adversely affected for a number of miles downstream.’

Source: Waste Management Department, 1996–2005 Sanitation Strategic Plan, Kumasi, Ghana.

The use of polluted irrigation water threatens public health. Market surveys by IWMI in Kumasi, Accra and Tamale showed that it is very difficult to find any irrigated vegetables (e.g. lettuce, spring onions, cabbage) that are not contaminated with faecal coliforms. Helminth eggs are also commonly found on such vegetables. Coliform contamination levels of vegetables are often almost the equivalent of a similar amount of fresh faeces (Keraita et al., 2003b). The nutrient concentration in the water is comparatively less excessive due to wastewater dilution. In and around Kumasi, for example, the total nitrogen applied via 1,000 mm of annual irrigation ranges between between 10 and 15 kg/ha upstream of the city and up to ten times that value downstream. Phosphorus values range between 7–11 kg P₂O₅ /ha. Potassium ranges between 50 and 80 kg K₂O/ha. Salinity is low (EC <1 dS/m) and pH ranges from 6.8–7.2, which is in the normal range for irrigation (IWMI, unpublished).

Use of Polluted Water in Urban Agriculture

It was estimated that if only 10% of the 280 million m³ of wastewater from urban Ghana could be (treated and) used for irrigation, the total area that could be irrigated with wastewater alone could be up to 4,600 ha. At an average dry-season farm size of 0.5 ha, this could provide livelihood support for about 9,200 farmers in the peri-urban areas of Ghana (Agodzo et al., 2003). However, as described in the previous sections, there is inadequate sewage conveyance capacity. In Accra, as in the other cities directly located on the coast, most wastewater flows into the ocean for lack of any land physically available for agriculture. In other cities and towns, such as Kumasi, wastewater flows from drains into streams, which are usually used for irrigation. Thus wastewater is mostly used in a diluted form mixed with surface runoff and/or stream water (Cornish et al., 2001).

However, there are also cases where farmers use wastewater directly from drains and broken sewers without further dilution, especially in the dry season. For simplification, all these water sources are referred to as ‘wastewater’ in the following sections, unless a differentiation is required.

Open-space Vegetable Farming

A common picture in both urban and peri-urban areas of Ghana is the cultivation of such cereals as maize in the rainy seasons and of irrigated vegetables in the dry seasons. More than 15 kinds of vegetables are cultivated, all of which are sold. The most perishable (often non-traditional) vegetables, such as lettuce, are usually grown in the city and often harvested 11 times during the year (with only supplementary irrigation during the rainy season) (Table 9.2). Less-perishable vegetables, such as aubergines (locally known as garden eggs) are typical of dry-season irrigation in peri-urban areas. Here, staples like maize and cassava for subsistence are preferred in the rainy season.

Due to the high food prices in the dry season, the highest-value land sites have access to water. They are located on river banks, next to drains, in valley bottomlands, and if possible close to the city to reduce transport costs.

The use of polluted water for vegetable farming is more widespread in the more populated cities where safe water is scare and is used for domestic purposes. From a general survey among open-space farmers carried out in 2002, it was found that about 84% of nearly 800 farmers farming in and close to Accra and almost all 700 farmers in Tamale used polluted water for irrigation, at least during the dry seasons.

Typical urban farm sizes range from 0.1–0.2 ha and they increase in size along the urban–rural gradient. As production is market-oriented, farming is input- and output-intensive, particularly in terms of the use of water and such other farm inputs as poultry manure, pesticides and fertilisers. In Ghana, most farmers use watering cans to irrigate, while motor pumps are more common in Togo (Keraita et al., 2003a). Only a few farmers with larger holdings in peri-urban areas use motor pumps. The promotion of treadle pumps started only very recently. Farmers fall into different age groups, but the majority are between 20 and 40 years old. Most of those engaged in urban agriculture are migrants from rural areas, often from the Islamic northern regions, and have experience in farming. For many urban or peri-urban farmers agriculture is the main source of household income, although not the only one.

Table 9.2. Features of selected open-space urban agriculture sites in Accra.

In contrast to vegetable farmers, almost all crop and vegetable sellers are women. Many of them buy vegetables on-farm from field beds and often order in advance (Danso and Drechsel, 2003). Otherwise, open-space vegetable farming is more than 90% male-dominated especially in urban areas, usually with a large distance between the home and the actual farm plot. The reasons mentioned by farmers of both genders for the dominance of men in vegetable production, are the arduous tasks including irrigation with two heavy 15-l watering cans and traditional work sharing with women responsible for food preparation, small businesses and/or hawking. As one moves to the rural areas, however, the number of women assisting in vegetable farming increases slightly. Most undertake such activities as carrying irrigation water in buckets as ‘head-loads’ to

the fields, weeding, and harvesting delicate vegetables. While almost all men do vegetable farming purely to generate income, women also use the produce (except for non-traditional crops) to feed their families.

Irrigation Water Requirements and Application Rates

The amount of irrigation water required depends on the effectiveness of rainfall in any given location. For the vegetables grown, the crop water requirements range between 300 and 700 mm depending on the climatic conditions and the season of the crop at the location (Table 9.3). For some farming activities that coincide with the major rainy season, irrigation water requirements are minimal. On the other hand, in the drier months in urban areas located in the dry savannah areas, irrigation water requirements per growing season could be as high as 600 mm as shown in Table 9.3. For farmers in the urban centres that depend on water from the drains, there may be insufficient water to meet their crop requirements (Agodzo et al., 2003), especially if crops are grown all year round. Tap water is only available on one openspace site in Accra (Table 9.2). With up to 11 lettuce harvests per year (manual) application rates between 600 and 1,600 mm are common.

Socio-economic Benefits of Wastewater Irrigation

Individual benefits

Preliminary cost/benefit analyses have been carried out for urban and peri-urban vegetable farmers in and around Kumasi (Danso et al., 2002a; Cornish and Aidoo, 2000). Year-round, open-space urban farmers can achieve annual income levels of US$400–800/ha (Table 9.4). These levels are achieved due to the intensive nature of farming made possible partly by the free and reliable supply of water. However, being successful in this way requires careful observations of market demand in the lean season in order to properly plan for the required inputs, particularly seed (Danso and Drechsel, 2003). Also, dry season peri-urban vegetable farming is seen as a significant source for income generation, since during the wet season staple crops are also grown for household consumption.

Table 9.3. Crop water requirements for seasonal vegetable production in and around Accra, Kumasi and Tamale.

Source: Agodzo et al. (2003). The data presented are for irrigation projects near each city.

Table 9.4. Revenue generated in different farming systems.

Source: Danso et al. (2002a).

A detailed survey carried out by Cornish and Aidoo (2000) in peri-urban Kumasi showed the profitability of different crops (Table 9.5). Based on actual farm size, average profits ranged in villages between US$140–170 per farmer. Irrigation practised here is either manual (watering can) or by motorised pumping. Farmers with motor pumps have higher production costs, but revenues were not commensurately higher (Cornish et al., 2001). If the daily per capita income is calculated, only households engaged in urban agriculture (see Table 9.4) could move above the poverty line of US$1 per day (Danso et al., 2002a).

On average, farm income from all vegetables amounts to about US$1,440/ha but a more conservative estimate considering actual crop mix could be US$500/ha (Cornish et al., 2001). Most of the vegetable crops are grown in the dry months of November to February. The authors estimate the actual peri-urban area under informal irrigation within a 40-km radius of Kumasi as 11,500 ha. This is more than the total area reported under formal irrigation in the whole country. The annual value of this production has been estimated as US$5.7 million. A significant part of this (downstream of Kumasi) is produced with wastewater.

As mentioned above, vegetable marketing is the exclusive domain of women, be it in big markets or kiosks in residential areas. Inner urban area production means not only fresh produce but also lower transportation costs and higher profits.

Table 9.5. Income per commodity in peri-urban Kumasi.

Source: Cornish and Aidoo (2000).

Aggregate Benefit to the City

The value of wastewater irrigation should not only be seen from the perspective of livelihood support, employment, and income generation given that the actual (sometimes small) numbers of open-space farmers might not attract the attention of municipal authorities. The overall (aggregate) benefit to the city should also be highlighted. An example is the dependence of the city on irrigated urban vegetable production. Due to the lack of refrigerated transport and storage, the supply of perishable vegetables to urban dwellers depends significantly on this kind of agriculture (Nugent, 2000; Smith, 2002). In Senegal, for example, about 60% of the vegetables consumed in Dakar are produced within or close to the city (Niang et al., 2002), mostly with wastewater. The specific contribution of urban agriculture to aggregate city supply and its complementarity to peri-urban and rural production has also been quantified for selected cities of Ghana and Burkina Faso (Cofie and Drechsel, 2004). The analysis, that excludes backyard subsistence production, revealed that urban agriculture is a crucial supplier of the most perishable vegetables to the cities’ markets. Peri-urban production appears to be an important supplier of tomatoes and aubergines, while the majority of common staple crops like cassava, plantain, maize and rice in the city markets derive from rural areas or are imported (Fig. 9.4).

There is high demand for urban produce especially from low-income households and the large number of small (street) eating places (locally known as ‘chop-bars’) because it is fresh and they have limited possibilities for storage. Thus, most of the chop-bars benefit from wastewater irrigation.

Fig. 9.4. Contribution of urban (UA), peri-urban (PUA) and rural (RA) agriculture to urban vegetable supply in three West African cities.

Source: Cofie and Drechsel, 2004.

Institutional and Perceptional Issues on Wastewater Use in Urban Agriculture

According to one of its bylaws the Accra Municipality allows the production of crops in the city. In contrast to backyard farming, open-space production (or livestock keeping) requires registration with the Medical Officer of Health. Also the Land Title Registration Law accommodates the notion of multiple rights and interests on a single plot, which provides a legal framework for urban agriculture although a distinct corresponding land-use policy does not yet exist (Flynn-Dapaah, 2002). However, as a result of Ghana’s decentralisation efforts, there is a Directorate of Food and Agriculture within all metropolitan assemblies. The corresponding Metropolitan Directors of Agriculture work at the interface between the Municipality and the Ministry of Food and Agriculture with their own extension service. During Ghana’s annual ‘Farmers Day’ celebrations they honour – like their rural colleagues – the best farmers from all administrative districts and regions, including the best Metropolitan and peri-urban farmers. All this supports the status of urban agriculture in Ghana. Despite these positive signs the problem of crop contamination raises significant concerns, not only among the health directorates of the same assemblies, but also in the media. This is supported by a municipal bylaw stating, ‘No crops shall be watered by the effluent from a drain from any premises or any surface water from a drain which is fed by water from a street drainage’. This bylaw targets those vegetables and fruits likely to be eaten raw (Local Government, 1995). Although authorities expel farmers from time to time, water analysis is expensive and bylaw enforcement weak. Thus irrigated urban agriculture remains informal without any cross-sectoral support by authorities. And as farmers at most locations have no alternative to polluted water, they continue to use it. The interviews also showed that farmers in general place lower priority on the possible nutrient value of the wastewater than on its value simply as a reliable water source, especially in the dry season.² Thus the amounts of manure and fertiliser applied to crops are not reduced, even where water is highly polluted. A similar picture has been found with respect to farmers’ awareness of pathogen contamination. Cornish and Aidoo (2000) found that only one in four peri-urban farmers would not drink the water he/she used for irrigation. Urban farmers are more often confronted by authorities (and researchers) with the water–health problem and are decreasingly willing to discuss the issue. In general, however, they do not perceive it as a major problem. Those who speak freely usually say that they see no harm in the practice. As one put it, “Ever since I was born, my father has been doing this work and it is the same drain water we have been using with no health problem” (Obuobie, 2003). In fact, the source of the water or its quality is of little concern. More important to the farmers is its uninterrupted availability and that they do not have to pay for it (Obuobie, 2003). A similar low level of concern is found for the use of pesticides, which are usually considered as ‘plant medicine’. The most acutely perceived problems are access to credit, markets and water supply in peri-urban areas (Cornish and Lawrence, 2001), as well as land and water access, seed availability and low farm-gate prices in urban agriculture.

As consumers do not ask for ‘safe’ but ‘fresh’ and ‘clean’ products, neat appearance of the crops is most important for sellers. Refreshing and cleaning vegetables with water often of as bad quality as irrigation water is thus normal practice in markets (Drechsel et al., 2000). As mentioned above, many vegetable sellers in the city buy their crops on urban farms and are often aware of the water source, but also prefer not to discuss it, particularly not with customers. The general awareness level for environmental and health issues is low (Danso et al., 2002b) or of less importance than other concerns affecting consumers’ livelihood and health (food security, malaria, etc.). When complaints about vegetable appearance were raised by expatriates, however, sellers tried to satisfy customer demand by extra cleaning efforts (Drechsel et al., 2000).

² In other places, e.g. Nairobi, farmers showed more awareness of the nutrient value of wastewater (authors’ observations).

Conclusions

As in other principal urban centres in developing countries, the sanitation infrastructure in Ghana’s main cities has been outpaced by population increases, making the management of urban wastewater ineffective. Large volumes of partially or untreated wastewater adversely affect both water bodies and the urban and peri-urban farmers using these water bodies as sources of irrigation. High levels of pollution, specifically microbiological contamination, have been measured in irrigation water and on crops. This has raised concerns, especially on the part of local authorities as they pose heath risks to farmers and the general public. In order to protect consumers from contaminated vegetables, authorities in Accra have banned the agricultural use of polluted irrigation water. Enforcement, however, would not only affect the livelihoods of urban farmers and vegetables traders but would also reduce the continuous supply of traditional and non-traditional vegetables in the city. In this context, the implementation of the WHO irrigation guidelines appears impossible, as improved water treatment appears unviable. Similarly, there are few (tenure) possibilities or market incentives for farmers to grow crops that are not easily contaminated (like tree crops) or to use, for example, drip irrigation. In view of this, other approaches which take into account both public health risks and farmers’ livelihoods need to be devised (Drechsel et al., 2002). These should focus on low-cost options for risk reduction not only on farms (mini-sedimentation ponds, water filters), but also in markets and especially in households. Unless wastewater collection and treatment are generally improved, stakeholder education through awareness campaigns, e.g. on the importance of washing vegetables carefully before consumption will remain crucial to addressing the problem.³

³ Ghana’s Metro-TV has broadcast several times a related interview with IWMI Ghana staff on appropriate risk-reducing measures (November 2003). This gives an example for further activities.

References

Agodzo, S.K. (1998) Water Management Study of Six Selected Irrigation Projects in Ghana. FAO–GIDA Project Report No. TCP/GHA/6613 (T). Kumasi, Ghana, 109 pp.

Agodzo, S.K., Huibers, F.P., Chenini, F., van Lier, J.B. and Duran, A. (2003) Use of wastewater in irrigated agriculture. Country studies from Bolivia, Ghana and Tunisia, Vol. 2 (Ghana). WUR, Wageningen, The Netherlands. www.dow.wau.nl/iwe (access date 2002)

Cofie, O.O. and Drechsel, P. (2004) Water for food in the cities: the growing paradigm of irrigated (peri)-urban agriculture and its struggle in sub-Saharan Africa. African Water Journal 1(1) (in press).

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Document(s) 11 of 19