Urban Water Security: Managing Risks UNESCO-IHP

Understanding the impacts of urbanization on the urban water cycle and managing the associated health risks demand adequate strategies and measures. Health risks associated with urban water systems and services include the microbiological and chemical contamination of urban waters and outbreak of water-borne diseases, mainly due to poor water and sanitation in urban areas, and the discharge as well as the disposal of inadequately treated, or untreated, industrial and domestic wastewater. Climate change only exacerbates these problems, as alternative scenarios need to be taken into consideration in urban water risk management. Urban Water Security: Managing Risks – the result of a project by UNESCO’s International Hydrological Programme on the topic – addresses issues associated with urban water risks. The first section of the volume describes risks associated with urban water systems and services. The volume then discusses the concept of risk management for urban water systems and explores different approaches to managing and controlling urban water risks. A concluding section presents case studies on managing urban water risks. Urban Water Series - UNESCO-IHP, ISSN 1749-0790 Following from the Sixth Phase of UNESCO’s International Hydrological Programme (2002–2007), the Urban Water Series – UNESCO-IHP addresses fundamental issues related to the role of water in cities and the effects of urbanization on the hydrological cycle and water resources. Focusing on the development of integrated approaches to sustainable urban water management, the Series should inform the work of urban water management practitioners, policy-makers and educators throughout the world. Series Editors Cedo Maksimovic, Imperial College, London, United Kingdom J. Alberto Tejada-Guibert, International Hydrological Programme, UNESCO, Paris, France

1 Introduction * 2 Drinking water – Potential health effects caused by wastewater disposal * 2.1 Introduction * 2.2 Direct and indirect wastewater reuse * 2.3 Microbiological risks * 2.3.1 Viruses * 2.3.2 Bacteria * 2.3.3 Protozoa * 2.3.4 Helminths * 2.4 Risk reduction of pathogens in drinking water * 2.5 Chemical risks * 2.6 Treated wastewater in surface waters * 2.7 The occurrence of pharmaceuticals in drinking water * 2.8 Risk management of microbial and chemical hazards * 2.9 Implementation of Water Safety Plans * 2.10 HACCP * 2.11 Hazard analysis * 2.12 Conclusions * 2.13 References * 3 Microbial health risks and water quality * 3.1 Introduction * 3.2 The traditional icons of waterborne disease * 3.2.1 Cholera * 3.2.2 Typhoid * 3.2.3 Hepatitis * 3.2.4 Generic diarrhoea * 3.3 Emerging diseases and zoonotic pathogens * 3.3.1 Cryptosporidium * 3.3.2 Cyclospora * 3.3.3 E. coli O157:H7 * 3.3.4 Helicobacter * 3.4 Risk assessment and control of waterborne pathogens * 3.4.1 Use of quantitative microbial risk assessment * 3.4.2 Interventions to reduce enteric diseases * 3.4.3 Vaccinations * 3.5 Conclusions and recommendations * 3.6 References * 4 Chemical health risks * 4.1 Introduction * 4.2 Human health risks * 4.2.1 An overview on exposure factors * 4.2.2 Human exposure in urban water cycle * 4.3 Risk sources and risk compounds in urban water cycle * 4.3.1 Releases to water * 4.3.2 Chemical compounds * 4.4 Inorganic chemical risk agents: Sources and human health diseases of concern * 4.4.1 Nitrates and nitrites * 4.4.2 Fluoride * 4.4.3 Toxic metals * 4.4.3.1 Arsenic * 4.4.3.2 Mercury * 4.4.3.3 Lead * 4.5 Organic chemical risk agents: Sources and human health diseases of concern * 4.5.1 Hydrocarbons compounds * 4.5.2 Chlorinated organic compounds * 4.5.2.1 Volatile organic compounds (VOCs) * 4.5.2.2 Solvents * 4.5.2.3 Trihalomethanes (THMs) * 4.5.3 Pesticides * 4.5.4 Persistent organic pollutants (POPs) * 4.5.5 New chemicals * 4.6 Chemical risks in urban cities in developed countries * 4.6.1 Fluoride * 4.6.1.1 China * 4.6.1.2 Japan * 4.6.1.3 United States of America * 4.6.2 Arsenic (As) * 4.6.2.1 Canada * 4.6.2.2 China * 4.6.2.3 United States of America * 4.6.3 Mercury * 4.6.3.1 Canada Arctic * 4.6.3.2 China * 4.6.3.3 Japan * 4.6.3.4 United States of America * 4.6.4 Volatile organic compounds (VOCs) * 4.6.4.1 Netherlands * 4.6.4.2 United States of America * 4.6.5 Trihalomethanes (THMs) * 4.6.5.1 Alaska * 4.6.5.2 Canada * 4.6.5.3 United Kingdom * 4.6.5.4 United States of America * 4.6.6 New chemicals * 4.7 Chemical risks in urban cities in developing countries * 4.7.1 Fluoride * 4.7.1.1 Brazil * 4.7.1.2 Ethiopia * 4.7.1.3 India * 4.7.1.4 Kenya * 4.7.1.5 Mexico * 4.7.1.6 Saudi Arabia * 4.7.1.7 South Africa * 4.7.1.8 Turkey * 4.7.1.9 United Republic of Tanzania * 4.7.2 Arsenic (As) * 4.7.2.1 Argentina * 4.7.2.2 Bangladesh – West Bengal, India * 4.7.2.3 Chile * 4.7.2.4 Mexico * 4.7.2.5 Taiwan * 4.7.2.6 Thailand * 4.7.2.7 Vietnam * 4.7.3 Mercury (Hg) * 4.7.3.1 Brazil * 4.7.3.2 Philippines * 4.7.3.3 South Africa * 4.7.4 Trihalomethanes (THMs) * 4.7.4.1 Greece * 4.7.4.2 Malaysia * 4.7.4.3 Mexico * 4.7.4.4 Turkey * 4.7.5 Pesticides * 4.7.5.1 Brazil * 4.7.5.2 Egypt * 4.7.5.3 South Africa * 4.8 Chemical risk management in urban water cycle * 4.8.1 Chemical risks identification in urban water cycle * 4.8.1.1 Drinking water * 4.8.1.2 Other water-related chemical risks * 4.8.2 Vulnerability and variability * 4.8.3 Urban water policy * 4.9 References * 5 Risk Management on the urban water cycle. Climate change risks * 5.1 Introduction * 5.1.1 Global climate change * 5.1.2 Global climate change and hydrological cycle * 5.1.3 Mitigation of GHG emissions * 5.2 Water in an urbanized world * 5.2.1 Water scarcity * 5.3 Impacts and risks * 5.3.1 Water availability and glacial melt * 5.3.2 Sea level rise and extreme events * 5.3.3 Water quality * 5.3.4 Changes in the past decades related to global climate change * 5.3.5 Risks for urban settlements * 5.4 Adaptation and integration of climate change into urban water resource management * 5.4.1 Adaptation and sustainable development * 5.4.2 Planning under uncertainties * 5.4.3 Supply and demand options * 5.4.4 Urban water management * 5.4.5 Poverty and equity * 5.4.6 International aid * 5.5 Conclusions * 5.6 References * 6 Water source and drinking water risk management * 6.1 Introduction * 6.2 Security, reliability and risk * 6.3 Uncertainty, threats and effects * 6.4 Prevention, mitigation and resolution * 6.5 Scarcity and drought, an operational example * 6.6 Conclusions and recommendations * 6.6.1 Methodological considerations * 6.6.2 Operational considerations * 7 Wastewater risks in the urban water cycle * 7.1 Introduction * 7.2 Pollutant sources * 7.2.1 Point sources * 7.2.1.1 Municipal wastewater * 7.2.1.2 Industrial wastewater * 7.2.1.3 Stormwater * 7.2.2 Non-point pollutant sources * 7.2.2.1 Urban infrastructure * 7.2.2.2 Urban activities * 7.2.2.3 Disposal practices * 7.2.2.4 Other sources * 7.3 Pollutants involved * 7.3.1 Conventional parameters * 7.3.2 Biological pollutants * 7.3.3 Emerging pollutants * 7.3.3.1 Content in water * 7.3.3.2 Content in surface and groundwater * 7.4 Management * 7.4.1 Changing the concept of pollution sources * 7.4.2 Gathering useful information * 7.4.3 Monitoring campaigns * 7.4.4 Water sources management * 7.4.4.1 Groundwater * 7.4.4.2 Surface water * 7.4.5 Pollutant management * 7.4.5.1 Biological pollutants * 7.4.5.2 Chemical compounds * 7.4.6 Urban infrastructure and urban activities * 7.4.7 Climate change * 7.4.8 Education and research * 7.5 Treatment * 7.5.1 Biological pollutants * 7.5.2 Emerging pollutants * 7.5.3 Criteria for selecting wastewater treatment processes * 7.6 Wastewater disposal * 7.6.1 Soil disposal * 7.6.1.1 Soil disposal and aquifer storage * 7.6.1.2 Soil disposal and agriculture * 7.6.2 Disposal in water bodies * 7.6.2.1 Eutrophication * 7.6.2.2 Coupling wastewater disposal with water reuse * 7.7 Conclusions * 7.8 References * 8 Risks associated with biosolids reuse in agriculture * 8.1 Introduction * 8.2 Nutrient and agronomic value * 8.3 Microbiological quality * 8.4 Potentially toxic elements * 8.5 Organic contaminants * 8.6 Conclusions * 8.7 References * 9 ‘Closing the Urban Water Cycle’ integrated approach towards water reuse in Windhoek, Namibia * 9.1 Introduction * 9.2 Water sources in Windhoek * 9.2.1 Conventional water sources * 9.3 Reuse options implemented in Windhoek * 9.4 Future water supply augmentation to Windhoek * 9.5 Various process modifications from 1968 to 1995 * 9.6 Process design for the new Goreangab water reclamation plant * 9.6.1 Summary * 9.6.2 Raw water quality profile * 9.6.3 Determination of treatment objectives * 9.6.4 The multiple-barrier concept * 9.6.5 Experiments and pilot studies to determine process design criteria * 9.7 Selection of final process train * 9.8 Operational experience to date * 9.9 Water quality and monitoring * 9.10 Quality concerns with the present process configuration * 9.11 Cost considerations * 9.12 Public acceptance of direct potable reuse * 9.13 New research and development options * 9.13.1 Process related refinements * 9.13.2 Quality control * 9.13.3 Health * 9.14 Conclusion * 9.15 References * 10 Reducing risk from wastewater use in urban farming – a case study of Accra, Ghana * 10.1 Introduction * 10.2 The case of Accra * 10.2.1 Urban water use and wastewater management * 10.2.2 Irrigated urban vegetable farming * 10.2.3 Irrigation water quality * 10.2.4 Quality of vegetables in urban markets in Accra * 10.2.5 Numbers of consumers at risk * 10.2.6 Risk assessment to farmers and consumers * 10.3 Risk reduction measures * 10.3.1 Explore alternative farmland, tenure security and safer water sources * 10.3.2 Promote safer irrigation methods * 10.3.3 Influence the choice of crops grown * 10.3.4 Avoid post-harvest contamination * 10.3.5 Assist post-harvest decontamination * 10.3.6 Improve institutional