Bernard Keraita

Influence of urban wastewater on stream water quality and agriculture in and around Kumasi, Ghana

This paper presents some findings from an ongoing International Water Management Institute research project in Ghana on urban wastewater use in agriculture. The paper focuses on the influence of urban wastewater on stream water quality and peri urban agriculture in Kumasi, and aims to develop strategies to reduce environmental pollution and risks from agricultural use of wastewater. It drew on interviews with local authorities, sanitation services providers, vegetable producers, traders and consumers, and on an assessment of the existing sanitation infrastructure and water quality. With few industries in Kumasi, urban wastewater is generated mostly from domestic sources. Population increase and lack of investment have overstretched the few available sanitation facilities, and large volumes of untreated or partially treated wastewater end up in nearby streams. High levels of faecal coliform were recorded in the city and downstream, as well as on vegetables in Kumasi’s markets, as contaminated wastewater streams are used for irrigation. Although urban and peri urban agriculture has a positive impact on food supply and livelihoods, it poses health risks for farmers and consumers. The paper discusses the constraints on addressing these problems and makes some recommendations regarding low-cost strategies for safer use of available water, better urban decentralized wastewater management and increased public awareness.

Reducing microbial contamination on wastewater-irrigated lettuce by cessation of irrigation before harvesting

Objective  To assess the effectiveness of cessation of irrigation before harvesting in reducing microbial contamination of lettuce irrigated with wastewater in urban vegetable farming in Ghana.

Reducing health risks from wastewater use in urban and peri-urban Sub-Saharan Africa: applying the 2006 WHO guidelines

Where rapid urbanization is outpacing urban capacities to provide sound sanitation and wastewater treatment, most water sources in city vicinity are heavily polluted. This is of great concern as many of the leafy vegetables eaten raw in the cities are produced in these areas. Following the new WHO guidelines, different non-treatment options at farm, market, and kitchen level were field tested for health risk reduction with special consideration to efficiency and adoption potential. As most households are used to vegetable washing (although ineffectively), an important entry point for risk reduction is the increased emphasis of the new guidelines on food preparation measures. A combination of safer irrigation practices (water fetching, on-farm treatment, and application), the allocation of farmland with better water sources, and improved vegetable washing in kitchens appear to be able to reduce the potential risk of infections significantly, although it might not be possible to reach the ideal threshold without some kind of wastewater treatment. The on-farm trials carried out in Ghana also explored the limitation of other risk reduction measures, such as drip irrigation, crop restrictions and cessation of irrigation under local circumstances considering possible incentives for behaviour change.

Effect of low-cost irrigation methods on microbial contamination of lettuce irrigated with untreated wastewater

Objective  To assess the effectiveness of simple irrigation methods such as drip irrigation kits, furrow irrigation and use of watering cans in reducing contamination of lettuce irrigated with polluted water in urban farming in Ghana.

Irrigated urban vegetable production in Ghana: characteristics, benefits and risk mitigation

This chapter serves as an introduction to the book and provides brief information about urbanization in West Africa, and in Ghana in particular, the general role of urban agriculture and the common use of polluted irrigation water. It describes our focus on irrigated smallholder vegetable production and our understanding of the terms ‘urban‘, ‘peri-urban’ and ‘wastewater’. The chapter reflects on some of the key challenges of the farming system, its dynamic and resilience. It also gives an overview on the structure of the book, the origins of the data and the main objective of this publication.This chapter examines key institutional issues that are important to the recognition and sustainability of irrigated vegetable farming in Ghanaian cities. It assesses the informal nature of the business and examines current roles being played by relevant agencies directly or indirectly linked to urban vegetable farming and urban wastewater management. The chapter also looks at relevant bylaws, strategies and policies that have implications for the recognition of informal irrigation and/or the adoption of safety measures for risk reduction in irrigated vegetable farming. It also suggests options to facilitate the institutionalization of irrigated urban agriculture.This chapter examines key institutional issues that are important to the recognition and sustainability of irrigated vegetable farming in Ghanaian cities. It assesses the informal nature of the business and examines current roles being played by relevant agencies directly or indirectly linked to urban vegetable farming and urban wastewater management. The chapter also looks at relevant bylaws, strategies and policies that have implications for the recognition of informal irrigation and/or the adoption of safety measures for risk reduction in irrigated vegetable farming. It also suggests options to facilitate the institutionalization of irrigated urban agriculture.

Potential of simple filters to improve microbial quality of irrigation water used in urban vegetable farming in Ghana

Irrigation water used for growing vegetables in urban areas in many low-income countries is contaminated with untreated wastewater. Many wastewater treatment methods are economically prohibitive and continued use of such irrigation water pose health risks for vegetable consumers and farmers. As part of a larger study on possible interventions for health risk reduction, the potential of simple interventions was explored. Column slow sand filters with three levels of sand depths (0.5 m, 0.75 m and 1 m) and fabric filters made of nylon, cotton and netting were assessed. More than 600 water samples were analyzed for helminth eggs and thermotolerant coliforms. Flow rates were also measured. From slow sand filters, 71–96% of helminths and 2 log units (from 7 to 5 log units) of thermotolerant coliforms were removed. Sand depths had no significant influence in the removal. Lower removal rates were achieved by fabric filters, with an average removal of 12–62% for helminth eggs and 1 log unit for thermotolerant coliforms. Nylon filters had higher removal rates especially for helminth eggs (58%). Average flow rates for sand filters were 3 m per day and fabric filters had steady flows of about 1.5 liters per second, but flow reduced with time in cotton filters. The simple filters tested improved the microbial quality of irrigation water and could easily be used in combination with other interventions to further reduce health risks. The unit cost of the filters tested also appear acceptable to farmers and some incentives like better prices will motivate many farmers to invest in such simple interventions.

Soil and Crop Contamination Through Wastewater Irrigation and Options for Risk Reduction in Developing Countries

Wastewater irrigation is becoming a global phenomenon, as a result of global water scarcity and increased pollution of water sources. While this practice offers many opportunities, human health risks from contaminated soils and crops irrigated with wastewater pose the greatest challenges to this practice. In this chapter, contaminants in wastewater of most relevance to soil and crop, such as pathogens, heavy metals, and other organic contaminants as well as the related human health and environmental risks are discussed. There is a general consensus that untreated wastewater contaminates soils and crops and poses health risks, however the threats vary widely. While wastewater treatment is the best choice to address this problem, a number of low-cost technological options and health protection measures exist to address the contamination challenges, especially in developing countries. These include irrigation methods, farm-based measures for improving water quality, choice of crop, water application techniques, soil phytoremediation, zoning, and postharvest measures. For comprehensive risk reduction, a combination of these measures is recommended, especially where comprehensive wastewater treatment is not feasible.

Microbiological quality of urban-vended salad and its association with gastrointestinal diseases in Kumasi, Ghana

The influence of consumption of salads on exposure to gastrointestinal diseases was assessed in urban environments in Kumasi, Ghana. Data was collected using a cross-sectional survey involving 15 salad sellers and 213 consumers and microbiological laboratory analysis of 96 samples of ready-to-eat salad. Findings showed higher contamination in street-vended salads than those in cafeterias with thermotelerant coliforms levels of 4.00–5.43 log units per 100 g salad, 32% of samples had Salmonella sp ., and 17% had helminth eggs. Overall, there was an insignificant inverse relationship between salad consumption and gastrointestinal diseases among street salad consumers (RR = 0.81) and a strong positive relationship with cafeteria consumers (RR = 5.51). However, stratified analysis on relative risk showed a likelihood of strong influence from other risk factors embedded in socio-economic status such as poor sanitation. We recommend more integrated studies on risk factors for gastrointestinal diseases in poor urban areas.

Redefining shared sanitation.

PerspectivesAs the Millennium Development Goals reach their deadline, it is clear that the world is not on track to achieve global sanitation targets. With sanitation trends, global developments and local contexts in mind, it is time to adopt a more flexible approach to achieving universal functional sanitation. By functional sanitation, we mean toilet facilities that protect human health by preventing contamination of the envi-ronment with human faecal waste.According to the latest estimates from the World Health Organization/United Nations Children’s Fund Joint Monitoring Programme for water and sanitation (JMP), 2.5billion people worldwide do not have access to any type of improved sanitation. To meet the JMP definition of improved sanita-tion, toilets must be used by only one household, as well as meeting certain design standards that prevent human contact with faeces. Of this 2.5billion, 732million use a facility that does not meet minimum hygiene standards and one billion people practise open def-ecation (i.e. defecation without using a toilet facility).

Smell: an overlooked factor in sanitation promotion

Bad smell from human waste carries so many social, moral, aesthetic, and disease-related concerns that it represents a major barrier to successful sanitation adaptation for people all over the world. This paper summarizes the authors experiences from sanitation research in low- and middle-income settings from several continents and research disciplines, and addresses the often-overlooked issue of reduction of smell for effective sanitation promotion. The paper argues that people therefore have developed strategies to avoid smell, some of these being of concern to public health specialists. It is recommended that smell and smellavoiding strategies are integrated into all phases of sanitation promotion programmes, from investigatory, to design, and maintenance planning.