Scholarly article on topic 'City Waste for Agriculture: Emerging Priorities which Influence Agenda Setting'

City Waste for Agriculture: Emerging Priorities which Influence Agenda Setting Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — L. Raschid-Sally

Abstract Using city wastewater in agriculture for its water and nutrient values is a widespread practice that entails varying degrees of risk depending on the context of use. This paper presents the ‘multiple realities’ of wastewater use, describing the complex set of drivers that impels prevalent practices. These drivers in turn define a set of emerging issues and priorities. The paper emphasizes that recent thinking on the use of city water in agriculture has evolved rapidly, leading to gaps between the existing knowledge base and the knowledge needed to respond effectively and maximize benefits. In this paper we attempt to address these gaps by presenting a cross section of concepts, approaches and tools that are relevant to policy and can be utilized for agenda setting and good governance.

Academic research paper on topic "City Waste for Agriculture: Emerging Priorities which Influence Agenda Setting"

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Procedía

Aquatic

ELSEVIER

Aquatic Procedía 1 (2013) 88 - 99

www.elsevier.com/locate/procedia

World Water Week, 26-31 August 2012, Stockholm, Sweden

City waste for agriculture: Emerging priorities which influence

agenda setting

L. Raschid-Sally*

Using city wastewater in agriculture for its water and nutrient values is a widespread practice that entails varying degrees of risk depending on the context of use. This paper presents the 'multiple realities' of wastewater use, describing the complex set of drivers that impels prevalent practices. These drivers in turn define a set of emerging issues and priorities. The paper emphasizes that recent thinking on the use of city water in agriculture has evolved rapidly, leading to gaps between the existing knowledge base and the knowledge needed to respond effectively and maximize benefits. In this paper we attempt to address these gaps by presenting a cross section of concepts, approaches and tools that are relevant to policy and can be utilized for agenda setting and good governance.

© 2013The Authors.Published byElsevier B.V.

Selectionand peer-review underresponsibilityofthe Stockholm InternationalWaterInstitute Keywords: wastewater agriculture, risk management, policy, governance

1. Introduction

In addressing wastewater use in irrigated agriculture, the one-size-fits-all concept has been applied consistently to date, with preconceived good practices for risk reduction from the developed world being applied inappropriately in developing countries. However, we are dealing with a diverse set of circumstances that are often location and context specific. Practitioners dealing with wastewater irrigation can no longer rely on conventional responses to resolve the problem of risk reduction. Rather, a multiple set of realities has to be understood and a very varied set of drivers and practices has to be assimilated, whether it is for setting a global agenda for reuse, or

* Corresponding author. E-mail address: l.raschid@cgiar.org

Senior Consultant Researcher, International Water Management Institute, Colombo, Sri Lanka

Abstract

2214-241X © 2013 The Authors. Published by Elsevier B.V.

Selection and peer-review under responsibility of the Stockholm International Water Institute doi: 10.1016/j.aqpro.2013.07.008

for developing risk-management guidelines. To address this diversity, various concepts, approaches and tools have surfaced whose value and potential have not always been understood by practitioners.

In this paper, after describing a simplified typology of use and the extent of the practice, we characterize the multiple realities of wastewater use and identify the emerging issues, priori-ties and research gaps. The key concepts, approaches and tools are discussed in order to understand how they can be used to address the reality. The underlying governance issues around their application have also to be understood for the successful implementation of wastewater reuse and recycling programmes.

2. Wastewater use - extents and practices

2.1. Typology of wastewater use

A typology of wastewater use characterizes the various ways in which wastewater is used for irrigation, in order to prepare a benchmark and to provide a basis for regulation. A comprehensive set of definitions, terminology and typology related to wastewater is to be found in Jiménez and Asano (2008), but attempts to normalize these have remained ineffective. Raschid-Sally (2010) even presents arguments to suggest that its usefulness is purely contextual, and should be aligned to the objectives that one hopes to achieve by preparing a typology. From this perspective, it is useful to distinguish between two principal types of wastewater use.

Unplanned use, which is synonymous with use of untreated wastewater, is geographically situated mostly downstream of urban areas and is often associated with inadequate wastewater collection, treatment and disposal infrastructure. Planned use of (treated) wastewater, on the other hand, requires high real water consumption by households (at least 100-150 L/person/d) to generate sufficient wastewater to make the whole reuse system viable; good sewer coverage (at least 87%) and, in particular, a good collection network are necessary elements. The collected wastewater is treated and then used for agricultural and other purposes. The degree of treatment depends on the degree of functionality of the plant: 56% of cities in low- to middle-income countries reported that treatment plants in their countries were non-functional or only partly functional (Raschid-Sally and Jayakody, 2008).

The degree of dilution prior to use defines whether it is a direct or an indirect use. Treated wastewater benefits from dilution or mixing with fresh water when salinity is high, as does untreated wastewater. Tables 1 and 2 summarize some key characteristics of wastewater use systems.

Table 1. Gross domestic product (GDP) and sanitation coverage in countries with planned and unplanned use of wastewater

Type of use GDP/capita (US$) in at least Sanitation coverage (%) in at least

half the sample half the sample

Planned (mainly treated) 4313-19,800 87-100

Unplanned (mainly untreated) 880-4800 15-65

Source: Adapted from Jimenez and Asano (2008)

Table 2. Characteristics of the two principal wastewater irrigation systems

Management status Climate

Physical location

Official recognition Water quality

Health-risk mitigation focus Existing in-country institutional

capacity

Main policy challenge

Risk mitigation challenge

Position on sanitation ladder

Source: Adapted from Scott et al. (2010)

Unplanned use

Unplanned activities close to waterways in/near urban centres All climates, mostly driven by poor sanitation Geographically distributed

Often informal sector Varies largely from untreated to partially treated or generally diluted wastewater where quality can vary seasonally Safer irrigation and post-harvest measures mostly for unrestricted irrigation

Low to moderate

Balancing benefits against risks; moving towards pollution control and wastewater management plans and programmes

Incentives to support adoption of risk mitigation measures

Planned use

Planned use at a particular location

Mostly arid, but also driven by economic water scarcity Specific sites near actual or potential treatment plants, or channelled to agricultural sites Formal sector Treated, partially treated

Treatment for reuse; crop restrictions possible

Moderate to high

Wastewater governance for safe and productive reuse

Maintenance of treatment plants and control of post-treatment measures

E Higher

2.2. Extent of the practice

It is not possible to quantify use of wastewater in agriculture precisely with current datasets (Jiménez and Asano, 2008). Looking at information from a variety of sources, Raschid-Sally (2010) concludes that:

• various units are used to express the extent of the practice, and we are still far from agreement on the actual extents

• however, looking at the data, it is clear that wastewater is widely used in agriculture, with use of untreated wastewater dominating the picture

• broadly speaking, from known data, which in themselves are unreliable, unplanned use largely exceeds planned use by a factor of six to nine. In China alone estimates of the area irrigated with wastewater vary between 1,300,000 ha and 4,000,000 ha.

Precise quantification is complicated but may be necessary for some purposes. For the most part, however, orders of magnitude are sufficient, particularly if the purpose is to inform poli-cymakers and get the issue onto a national agenda. In such cases, simplified assessment methodologies may be sufficient.

3. Characterizing the multiple realities

By multiple realities, we mean that use is context specific and influenced by multiple sets of drivers. Consequently, this will shape policy formulation for risk management. While the significant factor is individual poverty, or low GDP at a national level, examples below from various countries describe the combinations of conditions that prevail.

3.1. In response to physical water scarcity

The Middle East and North Africa is a good example of a region suffering from physical water scarcity. In a sample of 14 countries analysed by the author, annual rainfall was less than 350 mm. Average per capita freshwater availability was 1062 m3/yr. Per capita annual income varied between USD 1170 and USD28270 (figures not later than 2003). Seventy percent of the sample of countries reviewed treated between 30% and 90% of their wastewater, and recycled between 20% and 100%, with half of these countries recycling 100%. Other examples of countries or regions where treated wastewater is being recycled in response to physical water scarcity include some Mediterranean states, arid areas of the USA and Australia.

Pakistan is an interesting example. With an annual rainfall of between 250 and 500 mm, Paki-stan is home to the largest irrigated area in the Eastern Mediterranean region (WHO, 2005), accounting for almost half of the region's total irrigated area. However, much of Pakistan's water resources originate from outside its borders, as indicated by its dependency ratio of 41%. The high dependency ratio coupled with the need for extensive irrigation partly explains why Pakistan uses 2.4 million m3 of wastewater daily in agriculture. An additional 400,000 m3 of wastewater was directly disposed of daily in irrigation canals. Only eight of the 388 cities in Pakistan had wastewater treatment facilities and even here the treatment capacity was limited; often less than 30% of the wastewater generated received treatment (Ensink et al., 2004). This presents a curious situation in which formal irrigation schemes are receptacles of wastewater, though such use would not be considered officially as wastewater use.

3.2. Pollution of traditional irrigation water sources

This is a very common situation in developing countries, driven by population growth in urban areas (which is accompanied by rapid growth in water demand), the poor state of sanitation infrastructure and the lack of human resources to manage these systems. Since 70% of domestic consumption returns as wastewater, a city of one million people would generate 70,000 m3 of wastewater each day, based on a domestic use of 100 L/person/d. Disposal of this untreated wastewater in water bodies traditionally used for irrigation leaves farmers with no alternatives. Achieving the Millennium Development Goal targets for water supply and sanitation and offering better services to the neglected peri-urban areas of sprawling cities may have unexpected consequences for irrigation water quality. The water bodies receiving this untreated wastewater rapidly exceed their assimilation capacities, as has been seen in the Odaw-Korle basin, where the city of Accra, Ghana, is located. A mere 12 km upstream of the city boundary the water is still suitable for various domestic uses, but downstream the river is practically an urban sewer that is being used to supply water for urban agriculture.

In spite of the populations of China's big cities moving towards high income status and recent massive investments in wastewater management infrastructure, pollution of water sources in China is widespread; more than 40% of rivers and lakes were rated as Class V-VI, with dissolved oxygen values of less than 2 mg/L (World Bank, 2001).

3.3. Urban food demand provides a livelihood option to farmers

In the wake of urbanization comes increased demand for food, often accompanied by a change in diet. In African cities, a move from traditional diets towards consumption of more exotic vegetables supports the growth of

spontaneous smallholder agricultural systems growing perishable produce in urban areas. The absence of cold transport systems is a further encouragement for development of peri-urban agriculture. Wastewater, which is freely available for much of the day, is a reliable source of water that allows for multiple cropping cycles. Where collection systems and sewers exist, farmers across the world break into these to access the water. Farmers willingly pay more for land with access to wastewater: in the Mezquital valley in Mexico, for example, farmers paid 2-5 times more for such land (Jiménez, 2005), and in Quetta, Pakistan, farmers paid 2.5 times more (Ensink et al., 2004).

The demand for dairy produce in the city of Hyderabad in India, located in the highly polluted Musi river basin, drives a flourishing trade in para grass used as dairy feed. The contribution of wastewater to urban food supply is exemplified by Pakistan, where 26% of the country's vegetable production originates from land irrigated with wastewater (Ensink et al., 2004). Even in Hanoi, Vietnam, in spite of higher rainfall, 80% of vegetable production is grown with wastewater (albeit diluted) (Lai, 2002). Fifty to 90% of vegetables consumed by urban dwellers across West Africa are produced within or close to the city, where the water sources are polluted.

The few studies addressing livelihoods and economic return to farmers indicate that annual incomes from wastewater agriculture ranged from USD420 to USD2800, allowing smallholder farmers to jump the poverty line (USD 1/d) in many cases. In Ghana, farmers' profits are due not to increased yields but to the ability to consistently produce crops that are in high demand.

3.4. Environmental protection and nutrient recycling

Wastewater treatment using intensive biological methods was first introduced in the 19th century in response to the increasing pollution of water systems that were receiving sewage flows from cities in what is now the developed world. The efficiencies of present day activated sludge systems, for instance, are about 80% for reduction of biological oxygen demand, chemical oxygen demand and total suspended solids, but only about 50% for removal of nutrients, i.e. nitrogen and phosphorus, and a mere 2% for the removal of microbiological contamination (faecal coliform indicator bacteria used) (Olivera and Von Sperling, 2008). In spite of improved removal efficiencies, there is concern that the remaining nutrients are harmful to aquatic ecosystems and could lead to eutrophication in some cases. One response has been to use treated wastewater to irrigate crops and trees, thus applying resource-recovery concepts. Tunisia, for example, recycles 30% to 43% of its treated wastewater through irrigation, a practice it adopted specifically to protect coastal areas, water resources in general and sensitive water bodies in particular (Bahri, 2009).

In this century, nutrient recycling is being marketed as a key component of natural resource management to address the shortfall of nutrients in depleted soils. It is estimated that if 1000 m3 of municipal wastewater is used to irrigate 1 ha, it can contribute 16-62 kg of total ni-trogen, 4-24 kg of phosphorus, 2-69 kg of potassium, and various amounts of other elements such as calcium, magnesium and sodium (Qadir et al., 2007). Given the global phosphorus cri-sis, excreta and wastewater can be critical sources of the nutrient (Rosemarin, 2004). Control-ling the application of wastewater to cater to the crop nutrient has yet to be mastered.

4. Emerging issues, priorities and research gaps

Stemming from these multiple realities, one can identify emerging issues, priorities and research gaps.

a. The current informal use of wastewater by smallholders in urban agriculture compels immediate responses to address the risks. These risks may be chemical or biological in nature. Chemical risks result from the discharge of wastewater contaminated with or-ganic and inorganic salts, heavy metals, oils and grease, etc. from industries and services located in urban areas. Household products and, more recently, endocrine disruptor chemicals found in wastes are also potential contributors to risk (Hamilton, 2007). Although these are a growing concern, the WHO (2006) guidelines for safe use of wastewater, excreta and greywater are clear about the very limited evidence of direct health impacts associated with chemicals, perhaps due to the nature of chemical toxicity.

Build-up of chemical contaminants in crops is low. When present, these substances can best be removed by treatment. The risk from pathogens in food crops is much more immediate and it is here that the WHO multiple-barrier approach described in WHO (2006) is particularly applicable, where treated wastewater is not available. However, this needs to be accompanied by studies quantifying risk and impact and research to identify risk-reducing options. Effective use of the WHO guidelines requires a better understanding of the principles behind it (see 'Approaches, concepts and tools,' below).

b. There is a need to understand the magnitude of the problem, the sources and degree of pollution and the extent of wastewater use in order to address irrigation water quality more specifically. Research on simpler methodologies for mapping extent of wastewater use and global risks is the first step towards helping both the agriculture sector and the irrigation sector to deal with it. New approaches and techniques being tested by the International Water Management Institute, Sri Lanka, use a combination of spatial analytical tools, such as remote sensing and geographic information systems, with hydrological and water-quality models to quantify extent of wastewater use and potential risks at a global scale.

c. Responding to the problem of wastewater treatment requires an incremental approach. Municipalities may have to develop incremental master plans with reuse of wastewater as an option. Affordable technologies for treating wastewater must be researched. Successful approaches to wastewater treatment, especially those that allow for productive use of wastes and recycling of nutrients, should be documented, tested and scaled out. Policymakers and practitioners may need to be convinced of the merits of recycling; this will require stakeholder engagement and social marketing, besides addressing issues of perception about the quality of products.

d. When planning for reuse to address water scarcity in particular, countries still tend to be drawn towards conventional risk-reduction techniques such as expensive treatments and disinfection. New knowledge must be generated on lower-cost risk-reduction technologies and these approaches utilized.

e. The natural assimilation capacity of water bodies should be used more effectively by treating wastewater only to the required degree before disposal. This would provide economies of scale and better-quality irrigation water, and would also enhance the ecosystem services that wastewater flows provide and the unique habitats they create, especially in non-perennial rivers.

5. Concepts, approaches and tools

Formerly, key concerns about use of wastewater for agricultural purposes related to water quality and nuisance value. Now, however, there is increasing recognition of the potential of wastewater as a resource and holistic systems thinking is being applied to its management. Recent understanding of the subject has evolved rapidly, leading to gaps between the existing knowledge base available to practitioners and the knowledge needed to address the multifaceted problem of wastewater irrigation. In this section, we present a cross section of concepts, approaches and tools useful to the practitioner.

5.1. Multiple-barrier approach to risk reduction

The multiple-barrier approach was first proposed in the 1989 WHO guidelines for the use of wastewater in agriculture and aquaculture (WHO, 1989). It was based on the premise that protection of public health can best be achieved by interrupting the flow of pathogens from the environment (soil, water, crops, etc.) to people. The 2006 guidelines (WHO, 2006) build on this by accepting that it is not the quality of the wastewater used but the quality of the crop consumed that influences the level of risk to the consumer. This implies that, irrespective of the quality of the irrigation water, the level of risk can be reduced by introducing 'barriers' that reduce contamination (Fig. 1). Thus, combining methods such as primary treatment, safer irrigation practices (e.g. drip irrigation), post-harvest processing (e.g. cleaner washing techniques for vegetables) and food hygiene can achieve the required level of consumer safety. The barriers are diverse, ranging from the application of on-farm treatment measures, to safer irrigation practices, to hygienic handling of produce, to safer food washing and preparation.

Figure 1. The multiple-barrier approach to reducing risks associated with using wastewater in production of food crops. SSource: Amoah et al.

(2011)

Fig. 2 presents various combinations of options that would achieve the same final health target. Several chapters in Drechsel et al. (2010) explain the approach and its applications further.

5.2. Health-based targets and quantitative microbial risk assessment

The WHO (1989) guidelines were based on the premise that the quality of irrigation water had to be maintained to ensure safety of produce. The WHO (2006) guidelines, however, shift the focus to a health-based target that defines a globally acceptable level of health protection. This can be achieved by applying a series of options for reducing the level of contamination reaching the consumer (Fig. 2). Thus, each barrier in Fig. 1 can reduce the pathogen load in the final produce by a given amount. Different barriers reduce pathogen load by different amounts, some being more effective than others. For example, drip irrigation (DI) of tall crops can achieve a four-log reduction in pathogen load (i.e. a 99.99% reduction), whereas DI of short crops achieves only a two-log reduction in pathogen load (i.e. a 90% reduction). Combining these various options results in the required level of health protection.

Figure 2. Examples of options to achieve the health-based target of ^ 10-6 disability-adjusted life years per person per year, equivalent to

drinking potable water.T Source: WHO (2004)

Quantitative microbial risk assessment (QMRA) is one of the tools used for risk assessments. It differs from the more commonly used tools, microbial analysis and epidemiological studies, in that it is a prospective assessment. Epidemiological studies, which have the advantage of measuring the actual occurrence of disease in an exposed population, are relatively expensive (Mara and Bos, 2010). QMRA can be used to estimate risk to human health by predicting infection or illness rates given densities of particular pathogens, measured or estimated rates of ingestion and appropriate dose-response models for the exposed population. The probability of infection over multiple exposures is then determined using simulation techniques. This accounts for the amount of uncertainty around the various parameters used, such as the uncertainty as to exactly how much wastewater is retained on 100 grams of leafy vegetable, which influences the risk of exposure.

5.3. Cost-effectiveness analysis of interventions to reduce risk

A cost-effectiveness analysis (CEA) provides a framework for the assessment of interventions to reduce health risk. The assessment is made in terms of the costs of the intervention per standardized health benefit achieved, measured in DALYs. This approach has been widely used in the water and sanitation sector but is only now being applied to wastewater irrigation. It can be used to rigorously evaluate the different combinations of interventions proposed in the multiple-barrier approach, and to assess their effectiveness in achieving a specific health benefit.

Costs of an intervention can be calculated through an economic-engineering analysis, where the costs are estimated for each individual procedure of the intervention and are then summed. Other costs include monitoring costs for risk mitigation, and other non-structural costs (Tiongco et al., 2010). A similar analysis can be undertaken for the benefits. With this in-formation, a CEA is conducted to understand the trade-offs available.

T Disability-adjusted life years (DALYs) is a measure of the time lost because of disability or death from a disease compared with a long life free of disability in the absence of the disease. The target of 10-6 DALYs/person/yr is the same level of health protection that was applied by the WHO 2004 guidelines for safe drinking water quality. A disease burden of 10-6 DALY/person/yr means that a city of one million people collectively suffers the loss of one DALY per year

5.4. 'Design for reuse' applying supply chain management theories and business modelling to capture downstream users' needs

Design for reuse or recovering resources for purposes of reusing them requires a paradigm shift from thinking of wastewater as a problem to considering it as a resource. Changes in the design philosophy (adopting a user-centred approach) and treatment systems are necessary, since the standards for safe disposal in agriculture are less stringent than for the aquatic environment, and this offers cost savings in many cases. The intended reuse informs technology choices, site selection and scale and is tailored to the needs of the end-users (Murray and Buckley, 2010).

This approach challenges top-down decision-making, and allows for the application of supply chain management theories, which suggest optimizing the management of a production chain by coordinating the actions of the independent sectors and actors in a unified whole to facilitate strategic decisions (Huibers et al., 2010).

Successful implementation at scale requires that principles of business modelling be applied. This implies moving away from subsidies in the wastewater and sanitation management sec-tor, and towards market-based mechanisms involving the private sector. Envisaging reuse as a business opportunity requires analysis of market needs, i.e. supply and demand for the raw material and final product, and an enabling environment (economic, socio-institutional and political) in which the business can function.

5.5. Multi-stakeholder processes and stakeholder buy-in

For the multiple realities described above, stakeholder processes can contribute positively; indeed, the absence of such processes may result in the failure of many of the potential solutions, such as recycling of treated wastewater to respond to water scarcity or getting stakeholder (farmer and consumer) buy-in for applying risk-reduction measures.

Multi-stakeholder processes are useful to get buy-in to a new idea, which may be unfamiliar or controversial or can generate multiple positions and perspectives. In its ideal form, such a process can bring together stakeholders with different views about managing a common resource, help them realise their interdependence for resolving it and lead to agreement on actions. Evans et al. (2010) analyse a few such processes that have been applied in situations involving untreated wastewater reuse. Their findings confirm those of Drechsel et al. (2008) and Dubbeling and de Zeeuw (2006), who found that multi-stakeholder processes improve the likelihood of success and sustainability of implementation through enhanced acceptance and ownership of policies formulated, improved coordination, and mobilizing and pooling of scarce human, technical and financial resources.

Community support through stakeholder consultation is thus an important element in the success of reuse schemes. In this case, multi-stakeholder processes are implemented to gain acceptance from users, build trust and reciprocity (Stenekes et al., 2006; Po et al., 2003) and provide the right climate for negotiation and conflict resolution.

With spontaneous untreated wastewater use, planning for sustainability should embrace in-volvement of government agencies addressing such areas as health, water, sanitation, agriculture and irrigation, as well as researchers, community groups and the private sector. In this case, multi-stakeholder processes have to work towards making incremental improvements on an existing situation, including both policy changes and application of simple innovative solutions to risk reduction.

5.6. Wastewater rights and swaps

Customary rights to water are widely recognized across the globe, and are not subject to quality considerations. Thus, the customary right to wastewater has to be recognized if there was prior use of this resource. Unfortunately, these rights can conflict with future planned wastewater use projects, especially if treated wastewater is expected to be sold at a higher price than that paid by the original user of the wastewater. A case in point is Mexico, where the authority issues water concession titles that guarantee a landowner access to water. However, only 30% of wastewater-irrigated land has a concession title linked to it; water currently used by landowners without concession title might be diverted to other users and uses, resulting in loss of livelihoods for those without concession title, even though they are traditional water users (Silva-Ochoa & Scott, 2004).

In Pakistan, a large number of court cases initiated by local water utilities or sanitation agen-cies have challenged the rights of local farmers to use wastewater resources. The outcome of these court cases was that farmers were forced either to pay for wastewater or to abandon its use. In Faisalabad, a group of wastewater farmers successfully appealed against one of these court orders because they had no access to a suitable alternative water source (Ensink et al., 2004). In Pakistan, farmers are also known to form associations and collectively negotiate wastewater use through purchase of the resource.

In a future scenario, farmers might be expected to swap freshwater for treated wastewater as an adaptive response to climate change. It is worth investigating whether such swaps can be an incentive for treating wastewater in less-developed countries, especially where water and sewerage are under the remit of the same utility.

5.7. Assimilation capacity, river recovery processes and ecosystem services through recycling

Aquatic ecosystems such as rivers have a natural assimilation capacity. This depends on various physico-chemical and biological processes inherent to ecosystems (e.g. meandering of the river, which slows water velocities and promotes sedimentation, and aquatic vegetation, which traps sediments and absorbs nutrients and other chemical substances, etc.) combined with the effects of human interventions, such as weirs, which promote aeration of water downstream and sedimentation upstream. All these contribute to river recovery processes that can be used optimally to treat wastewater. Recovery may be dramatic, as in the case of the Musi river in Hyderabad, India (Ensink et al., 2006), where 40 km downstream of the city the water quality has improved sufficiently to allow the return of fish and other freshwater species. The presence of wastewater has made it a perennial river, contributing to the creation of an ecosystem. In the Yamuna river in India, an ecosystem service is provided by wastewater, which, despite poor water quality, maintains the environmental flow in the river (Raschid-Sally and Jayakody, 2008).

6. Conclusions

Applying many of the new concepts, approaches and tools to the management of wastewater in agriculture would require a change in the governance of wastewater within countries, and development of adapted models. However, in many developing countries, development is driven in large part by the public sector, and institutional fragmentation in the public sector in relation to disposal, management and productive use of wastewater will impede the changes and developments needed to make better use of wastewater. Similarly, efforts to decentralize government agencies has resulted in overlap of, or lack of clarity about, responsibilities of different levels of government and the decentralized functions of ministries departments and agencies, and this adds to difficulties in trying to improve the use of wastewater in agriculture. The 'design for service' approach, for example, entails bottom-up decision-making processes that involve farmers and local authorities. Adopting this approach would require strengthening the decentralized government structures and mechanisms to engage with farmers and communities.

Moving from applying quality standards for irrigation water to a health-risk-based approach, as recommended by WHO (2006), is a major step, requiring not only a good understanding of the principles but also a review of existing institutions (both organizations and legislation). The WHO (2006) guidelines allow for greater flexibility in addressing concerns. To allay fears about the complex nature of the guidelines, WHO is preparing simple instructions for their application and building capacities of various stakeholders in the varied aspects related to their implementation.

Applying resource-recovery principles for nutrient recycling would need new financial and management models for wider uptake and accompanying governance requirements. For ex-ample, the availability of cheap fertilizers does not encourage resource recovery, so govern-ment policy must address this, e.g. by removing subsidies on fertilizer, if resource recycling is to be scaled out. Similarly, governance measures are needed that recognize the rights of farmers to wastewater, set up processes for stakeholder involvement and dialogue, and encourage adoption of a user-centred approach and application of bottom-up and participatory models required for successful implementation of wastewater reuse programmes.

With wastewater agriculture, water-borne health risks are transferred to the food chain, and this requires that the water, agriculture/food and health sectors work closely together. The urban planning and sanitation and wastewater management sectors also need to be involved. Improved governance also implies that better monitoring and evaluation mechanisms will be required at all levels.

Finally, planned recycling of wastewater for irrigation can be an adaptive response to climate change. Abstraction of water for other uses impacts on agriculture to a greater or lesser de-gree. Though return flows of wastewater (treated or untreated) do contribute to downstream uses, the amount of water abstracted is never replenished. Returning as much as possible of the water abstracted requires a greater degree of planning and more rigorous application of integrated water resources management at the basin level within and between countries than is currently practised.

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