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Water resources are under pressure from continuing population growth and urbanisation, rapid industralisation, and expanding and intensifying food production, particularly in developing countries and in urban areas. Urban populations may nearly double from current 3.4 billion to 6.4 billion by 2050. Numbers of people living in slums will rise even faster, with most of the rapid expansion in urbanization taking place not in megacities (21 of the world’s 33 megacities are on the coast), but in small and medium sized cities with populations of less than 500 000.
This represents a global threat to human health and wellbeing, with both immediate and long term consequences for efforts to reduce poverty whilst sustaining the integrity of some of our most productive ecosystems. At least 1.8 million children under five years-old die every year from water-related diseases. Diarrhoeal diseases make up over four per cent of the global disease burden, 90 percent of which is linked to environmental pollution, a lack of access to safe drinking water and sanitation. Over half of the world’s hospital beds are occupied by people suffering from water-related diseases.
The report reviews how the production and treatment cycle can be better understood and managed so that through better investment and management, major environmental, societal, and economic dividends can be achieved.
World’s water resource will not change but the amount of wastewater produced is increasing, and the infrastructure and management systems are not adequate for this increasing volume. Globally, two million tons of sewage, industrial and agricultural waste is discharged into the world’s waterways, and that is not counting the unregulated or illegal discharge of contaminated water. This wastewater contaminates freshwater and coastal ecosystems, threatening food security, access to safe drinking and bathing water and being a major health and environmental management challenge.
In particular, the way food is produced uses 70–90 per cent of the available fresh water, and much of this water returns back to the system with additional nutrients and contaminants. Further downstream, agricultural pollution is joined by human and industrial waste. Up to 90 per cent of wastewater flows untreated into the densely populated coastal zone. This contributes to the growth of marine dead zones, which already cover an area of 245 000 km2, approximately the same area as all the world’s coral reefs. This will lead to further losses in biodiversity and ecosystem resilience, which in turn will undermine prosperity and efforts towards a more sustainable future.
Currently, most of the wastewater infrastructure in many of the fastest growing cities is lacking, under-dimensioned or outdated. Worldwide, almost 900 million people still do not have access to safe water and some 2.6 billion, almost half the population of the developing world, do not have access to adequate sanitation.
For the 1.2 billion people living in areas of water scarcity, projected to increase to 3 billion by 2025, there is no option but to consider the treatment of wastewater as part of the solution to water shortage. Without better infrastructure and management, many millions of people will continue to die each year.
The financial, environmental and social costs associated with water quality and availability, are projected to increase dramatically unless wastewater management receives urgent attention. There are many causes driving this crisis, but it is clear that freshwater and coastal ecosystems across the globe, upon which humanity has depended for millennia, are increasingly threatened. It is equally clear that future demand for water cannot be met unless wastewater management is revolutionized.
Comprehensive and sustained wastewater management in combination with sanitation and hygiene is central to improved human health, food security, economic development, jobs and consequently poverty reduction.
The unregulated discharge of wastewater has also far reaching implications for the health of aquatic ecosystems, which threatens the resilience of biodiversity and the ecosystem services on which human wellbeing depends. One such impact, eutrophication, is a major global concern affecting the functioning of marine and freshwater ecosystems.
Agriculture is the single largest user of water, it uses an estimated 70 per cent of total global fresh water, returning the majority of this water back to the system. The daily drinking water requirement per person is 2–4 litres, but it takes 2 000 to 5 000 litres of water to produce one person’s daily food. Optimizing agricultural practices including irrigation techniques, fertilization practices, and reducing water evaporation and crop selection, can save significant amounts of water with a subsequent reduction in wastewater production.
The wastewater produced from rural agriculture and livestock production, as well as inland urban areas, represents indeed the first phase in wastewater production and pollution and constitutes a considerable challenge for downstream users. It is characterized by organic and inorganic contaminants; originating from dissolved contents of fertilizers, chemical runoff (such as pesticides), human waste, livestock manure and nutrients.
Where agriculture takes place in upper catchments, it may be the first cause of contamination in the water basin. However, agriculture also takes place downstream, where the water may already be polluted by other human activities that result in domestic and industrial waste. Hence there is a complex relationship between water quality, agriculture and food quality, which is in turn linked to human and ecological health. In particular, the excess nitrogen and phosphorus introduced in their natural cycles drive algal booms, including toxic red tides and devastating hypoxic events that impact fish stocks or human health.
Overall, some 5–20 per cent of total water usage goes to industry. Water is an important requirement in many industrial processes such as heating, cooling, production, cleaning and rinsing, and this generates a substantial proportion of total wastewater.
Mining has traditionally been a major source of unregulated wastewater discharge in developing countries where more than 70 per cent of industrial wastes are dumped untreated into waterways where they pollute the usable water supply. It also seeps into the ground, contaminating aquifers and wells. The vast array of complex organic compounds and heavy metals used in modern industrial processes, if released into the environment, can cause both human health and environmental disasters. The contaminants in mine waste may be carcinogenic or neurotoxic to people (e.g. lead and mercury) or extremely toxic to aquatic organisms (e.g. copper). There are many examples of persistent environmental damage caused by the discharge of toxic mine waste.
Cooling waters used in industrial processes, like steel manufacture and coke production, not only produce discharge with an elevated temperature which can have adverse effects on biota, but can also become contaminated with a wide range of toxic substances.
The food and agriculture processing industry can also be a major producer of wastewater particularly organic waste with high biochemical oxygen demand resulting in low oxygen levels or even anoxic conditions in natural waters. Slaughterhouses may also produce biological material such as blood containing pathogens, hormones and antibiotics.
The most cost-effective solutions usually focus on preventing contaminants from ever entering the wastewater stream or developing a closed system of water use.
Changes to global climate patterns may affect water availability, in the timing and intensity of rainfall or the period of time without rain, as well as affecting the quality of water in rivers and lakes through changes in the timing and volume of peak discharge and temperature. Changing climatic conditions affect water availability in both time and space thus influencing water usage practices. Changes in climate will also require adaptation in terms of how wastewater is managed. Finally, although still a relatively small contributor to global emissions, wastewater and its management results in the emission of greenhouse gases, particularly carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). It is worth noting that methane has an impact 21 times greater than the same mass of carbon dioxide, and nitrous oxide, 310 times greater.
Anticipation of more droughts and extreme rainfall events, has impacts for non-existent or old, inadequate wastewater treatment facilities highlighting the need for infrastructure that can cope with extreme surges of wastewater. In the low-lying floodexposed land, floods will also spread diseases and cause diarrhoea through the flooding of open sewage or inadequate sewage infrastructure. Increasing pressure on water resources through more unreliable rainfall has in some regions pushed the exploitation of groundwater resources as other sources decline.
The effects of climate change are exacerbated by the rapidly increasing physical expansion of cities, deforestation and grazing of uplands surrounding cities, and the heavy build-up of infrastructure and lack of green rain-absorbing vegetation and areas inside cities.
Managing wastewater is intrinsically linked to management of the entire water chain. It is essential that wastewater management is considered as part of integrated, ecosystem-based management that operates across sectors and borders, freshwater and marine.
How we use and reuse water is the key to successfully meeting the vast water requirements of an urban population twice its current size, expanding agriculture to feed another three billion people and satisfy rising demand for meat. Finding solutions needs to draw on a cocktail of existing and new policy approaches and funding mechanisms.
There are few, if any, areas where investments in integrated planning can sustainably provide greater returns across multiple sectors than the development of water infrastructure and the promotion of improved wastewater management. However, this will require not only investments, but careful and comprehensive integrated water and wastewater planning and management at national and municipal levels. This must transcend the entire water supply and disposal chain involving ecosystem management (including coastal waters), agricultural efficiency and production, treatment of wastewater, and a stronger focus on urban planning.
Wise and immediate targeted and sustained investments that are scaled up appropriately will generate social, economic and environmental dividends far exceeding original investments for years to come. These should thus take multiple forms :
A paradigm shift is required towards new, innovative approaches that include wiser management, wise investments and technological innovation, not one size fits all, but ensuring that investments are appropriate to the industries and communities they serve. Such investments can boost economies, increase labour productivity and reduce poverty. Innovation is needed at both ends of the pipe to reduce the volume and contamination of wastewater produced, how to treat or even reuse the waste, and how to do it in an affordable sustainable way.
Education is vital and must play a central role in reducing overall volumes and harmful content of wastewater produced, so that solutions are sustainable. Increased understanding of the links between wastewater and health, ecosystem functioning and the potential benefits of wastewater reuse in contributing to development and improved wellbeing, can increase uptake of initiatives. It is vital that education and engagement of stakeholders in all sectors include access to solutions and be culturally specific. Education, together with awareness, advocacy and stewardship should be addressed at multiple levels, including the development of professional skills for improved inter-sectorial collaboration and multi-year financial planning.
Centralized systems generate a greater benefit as population increases, but show a significant loss with small community size. Experiences have shown that appropriate investments done in the right manner can provide the required returns and generate multiple benefits.
In centralized systems, wastewater transport and treatment facilities must be engineered to cope with irregular extreme flows. Both the cost of building and maintaining these systems and the reliance on a regular supply of water means this may not be an appropriate economical or environmental solution, particularly for smaller or secondary urban centres.
Decentralized systems may also be an appropriate option for urban areas prone to natural hazards. These systems can be designed to use no water or very little water and can be managed by households or communities. An example is the closed loop “ecological” toilet that separates urine and faeces so that they can be easily treated and then used safely in agriculture. However, local governments usually do not have the resources to build collection and treatment facilities so that untreated water can be used in peri-urban agriculture.
Improving watershed management will be crucial and finding ways to reduce, optimize and recycle water, will become increasingly essential in the future.
Wastewater is already being used for irrigation and fertilization and can continue to expand this role, particularly for peri-urban or urban agriculture, and home gardens. But maximizing water efficiency in the entire water chain, including before water enters the cities, and reducing production of wastewater should be primary goals throughout the entire management scheme.
There are clear health advantages related to wastewater use in agriculture, stemming directly from the provision of food (mainly vegetables) to urban populations or to generate biogas, thus turning the nutrients contained therein into resources. Typical concentrations of nutrients in treated wastewater effluent from conventional sewage treatment processes would supply all of the nitrogen and much of the phosphorus and potassium normally required for agricultural crop production. Other valuable micro-nutrients and the organic matter contained in the effluent would also provide benefits.
It is estimated that 10 per cent of the worlds population relies on food grown with untreated, contaminated wastewater. Whilst providing affordable food, the use of wastewater for food production without proper management can pose a serious risk. Untreated wastewater is often used in the informal, unregulated sector, and directly benefits poor farmers who would otherwise have little or no access to water for irrigation.
Forests and wetlands, including salt marsh and mangrove forests, have also an important natural role to play in wastewater management, capturing water, filtering out nutrients and other contaminants, and releasing water into lakes, rivers and coastal seas.
Because these water services are often viewed as a key public service and human right, privatization is often met with heavy resistance. There are many cases where privatization has led to improved water services by generating cheaper loans and higher investments, while bringing in expertise. However, it is also clear that unless the process is guided and under the close supervision of government agencies, there is a risk that the wider public interest will not be served and only wealthy customers will receive services.
Whilst experience has shown that privatizing water management as a means to gain more investments rarely results in positive results, the private sector has demonstrated improvements in operational efficiency and service quality. Hence, rather than outsourcing management, integrated partnership models where the private sector is given responsibility, not for the full water management but mainly for certain operational segments, can work best.
Bottled water sales worldwide have increased rapidly with global consumption now at more than 200 000 million litres a year. But the cost of producing bottled water is a serious concern. In the United States it is estimated that the production of the bottles alone requires 17 million barrels of oil a year and it takes three litres of water to produce one litre of bottled water.
Desalination of sea water is often the only viable option for providing safe drinking water in many arid, coastal regions or isolated locations such as small islands. However, it is not without consequences, both in terms of high economic cost, energy requirements, and because the process requires the use of descaling and antifouling products, which can contain heavy metals and toxic chemicals, and results in the discharge of a concentrated brine into receiving waters. Changes in salinity but also temperature over sustained periods could lead to local ecological changes, resulting in shifts in species diversity, opening the potential for the colonization of exotic and potentially invasive species, and changing ecosystem function.
In terms of public spending on health issues, investing in improved wastewater management and supply of safe water provides particularly high returns. Successful and sustainable management of wastewater requires a cocktail of innovative approaches that engage the public and private sector at local, national and transboundary scales.
Finding a solution requires integrated national to municipal water and wastewater planning that addresses the entire water chain – drinking water supply, production and treatment of wastewater, ecosystem management, agricultural efficiency and urban planning. Communities should plan wastewater management against future scenarios, not only current situations. Solutions must be socially and culturally appropriate. The cross-cutting nature of wastewater management requires collaboration and dialogue between partners who may not usually talk, for example farmers, public health officials, municipal and waste managers, planners and developers.
Inappropriate financing that does not produce results can have serious knock-on effects, leading to diminished public and political confidence and a lost opportunity to simultaneously tackle a problem and generate capital. Regarding industrial sources of wastewater, industry has a corporate responsibility to take action to ensure discharged water is of an acceptable standard, and can also benefit from access to cleaner water resources. Many incentives are based on voluntary measures, but governments and the public sector must play a central role in monitoring, regulating and also implementing policy to reduce toxic waste. In many countries, including European countries, the responsibility for industrial wastewater treatment still falls on ordinary taxpayers. In the absence of a userpays system for pollution control, large volumes of contaminated industrial wastewater end up in municipal sewage treatment plants, which are expensive to construct, operate and maintain.
Shadow pricing when a broader range of ecosystem services was incorporated (e.g. social welfare, GHG and nitrogen mitigation, waterfowl, recreation, etc…) is a valuation methodology that can also be used to assess choices regarding activities discharging by-products.
Countries must thus adopt a multi-sectorial approach to wastewater management as a matter of urgency, incorporating principles of ecosystem-based management from the watersheds down into the sea, connecting sectors that will reap immediate benefits from better wastewater management.
To be successful and sustainable, wastewater management must be an integral part of rural and urban development planning, across all sectors, and where feasible transcending political, administrative and jurisdictional borders. The public sector, including national, provincial and local governments, must be more proactive in funding wastewater management. Waste management planners must also consider both solid waste and wastewater in order to appropriately allocate resources. Planning processes should also provide an enabling environment for innovation, including at the community level but require government oversight and public management.
In their efforts to monitor progress in achieving the Millemium Development Goal (MDG) water and sanitation target, WHO and UNICEF designed « the sanitation ladder » which provides a useful instrument to assess the local status of sanitation in a community, municipality or region, pointing to optimal wastewater management strategies. It reflects also incremental progress even in situations where it is not possible to achieve the full MDG target. Poverty is the overarching determinant, and the position of a community on the sanitation ladder therefore relates to that community’s capacity to deal with wastewater management as well.
The Guidelines on the Safe Use of Wastewater, Excreta and Greywater in Agriculture and Aquaculture (WHO/FAO, 2006) provide a comprehensive framework for risk assessment and management that can be applied at different levels and in a range of socio-economic circumstances. However, in many countries the capacity to apply these guidelines and best practice recommendations is insufficient and needs substantial strengthening.
The UNEP/WHO/UN-HABITAT/WSSCC Guidelines on Municipal Wastewater Management also propose sustainable wastewater management based on an approach that integrates water supply and sanitation, and wastewater treatment. These guidelines also reflect needs for capacity development in this field and in response to these needs, UNEP/GPA jointly with the UNESCO-IHE Institute for Water Education and in the framework of the United Nations/DOALOS Train-Sea-Coast Programme, offer training courses on wastewater management to municipal staff.
More globally, the adoption of international standards and cooperation is cost-effective in countries with limited financial and laboratory capacity. Some challenges remain, but as shows the example that while most of Sri Lanka’s pesticide control only started a little over two decades ago, the progress that has been made thanks to the institutional arrangements, legislation, and enforcement, has been remarkable.
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