Javier Mateo-Sagasta

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.

Environmental Risks and Cost-Effective Risk Management in Wastewater Use Systems

Wastewater use in agriculture has many potential benefits, yet it also poses environmental risks. In particular, the use of untreated or partially treated wastewater over the long run may result in negative impacts on irrigated crops, soils, and groundwater through the addition of excessive levels of metals and metalloids, nutrients, salts and specific ionic species, and micro- pollutants. The environmental risk reduction strategies for wastewater can be categorized into: (1) treatment of wastewater to a desired effluent quality; (2) on-farm wastewater treatment options; and (3) farm-based measures to reduce risks in areas irrigated by untreated or partially treated wastewater. However, the number of strategies that have been economically assessed and have proven to be cost-effective is rather limited, although all mention a positive impact. Despite limited examples, the economics of risk management reveal that cost-effective options for improving water quality by removing undesirable constituents are available at the treatment plant level and beyond.

Assessing the finance and economics of resource recovery and reuse solutions across scales

The recovery and reuse of wastewater can contribute to reducing poverty, improving food security, improving nutrition and health, and managing natural resources more sustainability to protect ecosystems and build climate resilient communities. Reusing wastewater generates both private and public benefits, yet care must be taken to minimize environmental harm and risks to human health. Assessing the costs and benefits of wastewater use is challenging for decision making. Financial analysis of wastewater and other reuse options can underpin decision making from a business standpoint, and economic analysis provides the information needed to support public policy decisions. In this chapter, we provide a framework for assessing the finance and economics of wastewater and other reuse options. We examine several components of resource recovery and reuse, including water reuse, energy recovery, and nutrient capture from wastewater as well as fecal sludge and biosolids. We describe the cost-savings and partial cost-recovery made possible by wastewater use and we discuss value propositions for possible business models. Many water reuse solutions do not achieve financial cost recovery but are viable from an economic perspective. However, public agencies can enhance revenue streams by supporting more than water recovery and/or by targeting high-end users.

Economics of water reuse for industrial, environmental, recreational and potable purposes

Water reuse offers considerable economic value through the provision of health and environmental benefits, water and energy cost-savings and opportunities for businesses. In addition, activities associated with water reuse can generate revenue through the sale of water, energy, carbon credits, and by-products. Data limitations restrict the degree to which we can conduct a fully informed economic analysis of all pertinent costs and benefits. Yet the available information suggests the net benefits of water reuse can be substantial. We examine selected empirical cases of water reuse, highlighting the costs and benefits, and also reflecting on the enabling environment, challenges and opportunities for selected reuse options. The country-level experiences we describe provide insight for countries whose water resources are stretched by increasing urbanization and a changing climate.

Health Risks and Cost-Effective Health Risk Management in Wastewater Use Systems

The increasing extent and diversity of wastewater use, even without appropriate treatment, present public health risks. We describe existing approaches and options to managing health risks in various wastewater uses. Traditionally, regulators have used water quality standards achieved through wastewater treatment for health protection. The chapter presents some of the treatment technologies, including membrane filtration, which is increasing popular and effective in removing pathogens and other pollutants. However, the high investment, operation and maintenance costs of these technologies limit their use in resource constrained settings. In these settings, the use of health-based targets achieved through placing multiple barriers along the food chain is recommended. In this approach, firms, farmers, and public agencies have flexibility to choose from a range of low-cost risk management options which in combination can achieve the health targets. Returns on Investment (ROI) of these interventions are high (US

Proceedings of the UN-Water Project on the Safe Use of Wastewater in Agriculture

4.9 per US

Economic Valuation of Wastewater: The cost of action and the cost of no action

invested), if incentive systems and institutional arrangements are in place to support the application and adoption of these risk management measures.