Liqa Raschid-Sally

Wastewater use in irrigated agriculture : confronting the livelihood and environmental realities

With the increasing scarcity of fresh water resources in many arid and semi-arid regions of the world, the use of urban wastewater in agriculture is receiving renewed attention. Wastewater is a low-cost alternative to conventional Irrigation water, although it may carry health and environmental risks. This book critically reviews worldwide experiences of these issues.

Application of Quantitative Microbial Risk Assessment to analyze the public health risk from poor drinking water quality in a low income area in Accra, Ghana.

In Accra, Ghana, a majority of inhabitants lives in over-crowded areas with limited access to piped water supply, which is often also intermittent. This study assessed in a densely populated area the risk from microbial contamination of various sources of drinking water, by conducting a Quantitative Microbiological Risk Assessment (QMRA) to estimate the risk to human health from microorganism exposure and dose-response relationships. Furthermore the cost-effectiveness in reducing the disease burden through targeted interventions was evaluated. Five risk pathways for drinking water were identified through a survey (110 families), namely household storage, private yard taps, communal taps, communal wells and water sachets. Samples from each source were analyzed for Escherichia coli and Ascaris contamination. Published ratios between E. coli and other pathogens were used for the QMRA and disease burden calculations. The major part of the burden of disease originated from E. coli O157:H7 (78%) and the least important contributor was Cryptosporidium (0.01%). Other pathogens contributed 16% (Campylobacter), 5% (Rotavirus) and 0.3% (Ascaris). The sum of the disease burden of these pathogens was 0.5 DALYs per person per year, which is much higher than the WHO reference level. The major contamination pathway was found to be household storage. Disinfection of water at household level was the most cost-effective intervention (<5 USD/DALY-averted) together with hygiene education. Water supply network improvements were significantly less cost-effective.

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.

Global Wastewater and Sludge Production, Treatment and Use

Cities produce large amounts and very diverse types of waste including wastewater. The quality of these wastes depends on their source, the way in which they are collected and the treatment they receive. The final fate of these wastes is also very diverse. To better understand these systems this chapter provides definitions and reuse typologies and describes common reuse patterns and their driving factors. The chapter also shows that, while the prospects for resource recovery from wastewater and sludge are promising the potential is still largely untapped, except in the informal sector. The resources embedded in the approximately 330 km3/year of municipal wastewater that are globally generated would be theoretically enough to irrigate and fertilize millions of hectares of crops and to produce biogas to supply energy for millions of households. However, only a tiny proportion of these wastes is currently treated, and the portion which is safely reused is significantly smaller than the existing direct and especially indirect use of untreated wastewater, which are posing significant potential health risks. The chapter ends with a call for standardized data collection and reporting efforts across the formal and informal reuse sectors to provide more reliable and updated information on the wastewater and sludge cycles, essential to develop proper diagnosis and effective policies for the safe and productive use of these resources.

Wastewater irrigation and health: challenges and outlook for mitigating risks in low-income countries

In Drechsel, Pay; Scott, C. A.; Raschid-Sally, Liqa; Redwood, M.; Bahri, Akissa (Eds.). Wastewater irrigation and health: assessing and mitigating risk in low-income countries. London, UK: Earthscan; Ottawa, Canada: International Development Research Centre (IDRC); Colombo, Sri Lanka: International Water Management Institute (IWMI).In most developing countries wastewater treatment systems have very low coverage or function poorly, resulting in large-scale water pollution and the use of poor-quality water for crop irrigation, especially in the vicinity of urban centres. This can pose significant risks to public health, particularly where crops are eaten raw. Wastewater Irrigation and Health approaches this serious problem from a practical and realistic perspective, addressing the issues of health risk assessment and reduction in developing country settings. The book therefore complements other books on the topic of wastewater which focus on high-end treatment options and the use of treated wastewater. This book moves the debate forward by covering also the common reality of untreated wastewater, greywater and excreta use. It presents the state-of-the-art on quantitative risk assessment and low-cost options for health risk reduction, from treatment to on-farm and off-farm measures, in support of the multiple barrier approach of the 2006 guidelines for safe wastewater irrigation published by the World Health Organization. The 38 authors and co-authors are international key experts in the field of wastewater irrigation representing a mix of agronomists, engineers, social scientists and public health experts from Africa, Asia, Europe, North America and Australia. The chapters highlight experiences across the developing world with reference to various case studies from sub-Saharan Africa, Asia, Mexico and the Middle East. The book also addresses options for resource recovery and wastewater governance, thus clearly establishes a connection between agriculture, health and sanitation, which is often the missing link in the current discussion on حaking wastewater an assetٮ

Confronting the realities of wastewater use in irrigated agriculture: lessons learned and recommendations.

This concluding chapter synthesises results and lessons learned throughout this volume, which deals with the reality of wastewater use in agriculture in developing countries. It then extrapolates from these lessons, to make pragmatic recommendations aimed at protecting both the public health and farmers’ livelihoods. Addressing these lessons in a significant fashion is becoming ever more necessary, as it is likely that wastewater use will increase in many less-developed countries, due to growing urban and peri-urban populations and their matching demands for produce. The practice also deserves recognition for its potential socio-economic benefits, since some farmers would be unable to earn a living without using wastewater, and for others, its use increases the income they would normally make, lifting them out of poverty. However, unregulated wastewater use also raises serious concerns about the health of both consumers and farmers, creating the competing need to balance health impacts against livelihood needs. This chapter elucidates lessons learned, and makes four recommendations to policy-makers and practitioners: 1. to develop and apply appropriate guidelines for wastewater use, 2. to treat wastewater and control pollution at source, 3. to apply a range of non-treatment management options, and 4. to conduct research to both improve understanding of the practice, and to identify opportunities and constraints to the adoption of these recommendations. 174 N.I. Faruqui et al. common obstacles to improving the practice, and from these it has been possible to identify key issues that must be addressed in order to maximise the potential benefits, while minimising the potential costs that wastewater use offers. This concluding chapter now summarises these lessons learned, makes recommendations, and points to future research needs, that could contribute to safe and sustainable wastewater use under the diverse conditions that we have seen. Extent The first lesson forms the fundamental basis from which we must proceed, and it is that the general lack of knowledge of the importance of wastewater use impedes its inclusion as a priority issue to be considered in policy-making. Case studies from this volume illustrate this aspect and it is estimated that up to one-tenth of the world’s population eats food produced using wastewater (Lunven, 1992). As popula-

The global commodification of wastewater

With growing scarcity and competition for water, urban wastewater is increasingly marketable because of its water and nutrient values. Commodification has implications for the current “residual” uses of wastewater (particularly by poor farmers in developing countries), for the risk of disease transmission, and for wastewater-dependent agro-ecosystems. Using examples from Pakistan, India, Ethiopia, Ghana, Mexico, and the United States, this paper contrasts commodification as it occurs in the developed and developing worlds and demonstrates the need for public information and coherent institutional frameworks, including private- and public-sector participation.

Treatment plant effects on wastewater irrigation benefits: revisiting a case study in the Guanajuato River basin, Mexico.

In 1999 field research was carried out to explore the advantages and risks of urban wastewater use for 140 ha of crop production in the Guanajuato River basin. It was found that wastewater which was freely available to the farmers represented an important additional source of irrigation water, with secondary benefits including nutrients and the foregone cost of wastewater treatment. In 2002, the urban water supply and sanitation utility, a financially autonomous public utility, began to operate an activated sludge wastewater treatment plant in response to the imposition of legally mandated fines for the release of untreated wastewater to open water bodies. As follow-up to the 1999 study, this chapter is based on field visits and interviews and sets out to qualitatively answer the following research question: Does the introduction of wastewater treatment influence the crop production benefits of wastewater irrigation? The study found that because wastewater treatment was oriented to comply with environmental regulations, little attention was paid to the links with the land irrigated by wastewater. The presence of the treatment plant provides the utility with the option of selling treated wastewater, thus increasing its own economic benefits. Industrial users appear to be the most suitable potential customers; the utility would stand to receive US

Wastewater reuse for agriculture and aquaculture – current and future perspectives for low-income countries

0.43/m3 in estimated sale price plus saving the US

Perceptions, attitudes and behaviours toward urban surface water quality in Accra, Ghana

0.25/m3 fine. This transfer of water would introduce competition among water-use sectors, a process that is already leading to wastewater farmers’ uncertainty about their future share of irrigation water. However, to date no commercial transaction to transfer treated wastewater to non-agricultural users has taken place. For this reason the expected changes in impacts on wastewater farmers have been minimal. If this happens, however, the wastewater farmers stand to lose because only about 30% of the wastewater-irrigated land has a water concession title (linked to the land) issued by federal authorities.