Global Perspective of Wastewater Treatment
1.1 Global Wastewater Treatment Scenario
Natural water in contact with foreign matter during either industrial manufacturing processes or domestic use becomes polluted. Such polluted water is termed wastewater. The removal of excessively accumulated foreign matter from wastewater is known as treatment. As is well known, the rate at which we deplete and degrade our fresh aquatic resources poses a great threat to our future life-support system. The rise in human population exploits more natural resources and this is met through the growth of industries, urbanization, deforestation, and intensive agricultural practices. Industries and urban sprawl discharge waste into rivers, the deforestation process itself aggravates sedimentation transport into streams, and the use of chemicals contaminates groundwater through percolation and rivers and lakes through surface run-off.
All these sporadic degrading activities have led to gradual deterioration in the quality of surface and subsurface water. The loss of water quality is causing health hazards, death of human-beings, death of aquatic life, crop failures, and loss of esthetics. Keeping in mind these alarming global problems and the importance of environmental and nature protection, the 1972 Stockholm Conference on the Human Environment was the first of its kind and jolted the world into an awareness of environmental issues. A tangible result of that conference was the setting up of the United Nations Environment Program (UNEP) to serve as the conscience of the UN in matters concerning the environment. Twenty years later came the next landmark - the Earth Summit in Rio de Janeiro in 1992 - which exceeded everybody's expectations in terms of the number of attendees and scope of topics discussed. The Summit's message was broadcast to the world: "that nothing less than a transformation of our attitudes and behavior would bring about the necessary changes."
Figure 1.1 Global wastewater treatment scenarios.
Globally, the practice of wastewater treatment before discharge does not seem to be good. On average, high-income countries treat about 70% of the municipal and industrial wastewater they generate . That percentage drops to 38% in upper middle-income countries and to 28% in lower middle-income countries. In low-income countries, only 8% of wastewater undergoes treatment of any kind. These estimates support the often-cited approximation that, globally, over 80% of all wastewater is discharged without treatment. In high-income countries, the motivation for advanced wastewater treatment is either to maintain environmental quality or to provide an alternative water source when coping with water scarcity. However, the release of untreated wastewater remains common practice, especially in developing countries, due to lack of infrastructure, technical and institutional capacity, and financing (see Figure 1.1).
The discharge of untreated or inadequately treated wastewater into the environment results in the pollution of surface water, soil, and groundwater. The effects of releasing untreated or inadequately treated wastewater can be classified with regard to three issues:
- Adverse human health effects.
- Negative environmental effects due to the degradation of water bodies and ecosystems.
- Potential effects on economic activities: as the availability of freshwater is critical to sustain economic activities, poor water quality constitutes an additional obstacle to economic development.
According to the World Health Organization (WHO), water-related diseases kill around 2.2 million people globally each year - mostly children in developing countries.
1.2 The UN Sustainable Development Agenda for Wastewater
In September 2015, approximately 193 nation members of the United Nations General Assembly unanimously adopted "Agenda 2030" with a total of 17 Sustainable Development Goals (SDGs) to end poverty, protect the planet, and ensure prosperity for all (see Figure 1.2).
Figure 1.2 UN Sustainable Development Goals.
The establishment of SDG 6 (Clean Water and Sanitation) is aimed at ensuring availability and sustainable management of water and sanitation for all, reflecting the increased attention on water and wastewater treatment issues in the global political agenda. Agenda 2030 lists rising inequalities, natural resource depletion, environmental degradation, and climate change as among the greatest challenges of our time. It recognizes that social development and economic prosperity depend on the sustainable management of freshwater resources and ecosystems and it highlights the integrated nature of SDGs.
SDG 6 includes eight global targets that are universally applicable and aspirational. SDG 6 covers the entire water cycle, including: provision of drinking water (target 6.1) and sanitation and hygiene services (6.2); improved water quality, wastewater treatment, and safe reuse (6.3); water-use efficiency and scarcity (6.4); integrated water resources management (IWRM) including through transboundary cooperation (6.5); protecting and restoring water-related ecosystems (6.6); international cooperation and capacity-building (6.a); and participation in water and sanitation management (6.b).
SDG target 6.3 (to improve water quality, wastewater treatment, and safe reuse) focuses mainly on collecting, treating, and reusing wastewater from households and industry, reducing diffuse pollution and improving water quality. As per SDG 6 Synthesis Report 2018 on Water and Sanitation , ambient freshwater quality is at risk globally. Freshwater pollution is prevalent and increasing in many regions worldwide. Preliminary estimates of household wastewater flows from 79 mostly high- and high-middle-income countries show that 59% is safely treated. For these countries, it is further estimated that safe treatment levels of household wastewater flows with sewer connections and on-site facilities are 76 and 18%, respectively.
The degree of industrial pollution is not known, as discharges are ineffectively observed and only from time to time calculated and aggregated at national level. Although some local and modern wastewater is treated nearby, hardly any information is accessible and amassed for national and territorial evaluations. Numerous nations come up short on the ability to gather and analyse the information required for a full appraisal. Reliable water quality monitoring is fundamental to the direct needs for ventures. It is also important for assessing the status of aquatic ecosystems and the need for protection and restoration.
Increasing political will to tackle pollution at its source and to treat wastewater will protect public health and the environment, mitigate the costly impact of pollution, and increase the availability of water resources. Wastewater is an undervalued source of water, energy, nutrients, and other recoverable by-products. Recycling, reusing, and recovering what is normally seen as waste can alleviate water stress and provide many social, economic, and environmental benefits.
Managing wastewater by implementing global best practices of wastewater collection and treatment can support achievement of SGD target 6.3. Wastewater should be seen as a sustainable source of water, energy, nutrients, and other recoverable by-products, rather than as a burden. Choosing the most appropriate type of wastewater treatment system that can provide the most co-benefits is site specific, and countries need to build capacity to assess this. Reuse of water needs to take into account the whole river basin, as wastewater from one part of a basin may well be the source of supply for others downstream.
Managing wastewater and water quality also needs to include better knowledge of pollution sources. SDG reporting could support countries in aggregating wastewater subnational data and publicly reporting at the national level. This would include monitoring performance to ensure treatment plants are managed and maintained to deliver effluent suitable for safe disposal or use according to national standards, which may vary from country to country. Countries that do not have national standards and monitoring systems need to assess performance of on-site and off-site domestic wastewater treatment systems. Formalizing the informal sector through various policy instruments is needed to prevent excessive contamination. Incentives for the informal sector to be registered with the government could be accompanied by combined analysis of all wastewater sources and their relative contribution to health and environmental risks. This would enable countries to prioritize investments in pollution control that contribute most to achieving SDG target...