ENVIRONMENT and ENERGY
15 further endangering human health and ecosystems, contributing to water scarcity, and constraining sustainable economic development.
Global trends On average, high-income countries treat about 70 % of the municipal and industrial wastewater they generate. That ratio drops to 38 % in upper middle-income countries and to 28 % in lower middle-income countries.
In low-income countries, only 8 % 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 lacking infrastructure, technical and institutional capacity, and financing.
Wastewater, sanitation, and the sustainable development agenda Access to improved sanitation services can contribute significantly to the reduction of health risks. Further health gains may be realized through improved wastewater treatment. While 2.1 billion people gained access to improved sanitation facilities since 1990, 2.4 billion still do not have access to improved sanitation and nearly one billion people worldwide still practice open defecation.
However, improved sanitation coverage does not necessarily equate with improved wastewater management or public safety. Only 26 % of urban and 34 % of rural sanitation and wastewater services effectively prevent human contact with excreta along the entire sanitation chain and can therefore be considered safely managed.
The extremely low level of wastewater treatment reveals an urgent need for technological upgrades and safe water reuse options to support the achievement of targets. The efforts required to achieve Target 6.3 of the Sustainable Development Goals will place a higher financial burden on low-income and lower middle-income countries, putting them at an economic disadvantage compared to high income and upper middle-income countries.
Municipal and urban wastewater The composition of municipal wastewater can vary considerably, reflecting the range of contaminants released by various domestic, industrial, commercial, and institutional sources. Wastewater from domestic sources is usually relatively free of hazardous substances, but there are growing concerns about emerging pollutants, including commonly used medications, that, even at low concentrations, may have long-term impacts.
Accelerated urban growth poses several challenges, including dramatic increases in the generation of municipal wastewater. However, this growth also offers opportunities to break away from the past( inadequate) water management practices and adopt innovative approaches, which include the use of treated wastewater and by-products.
Wastewater generation is one of the biggest challenges associated to the growth of informal settlements( slums) in the developing world. There were more slum dwellers in 2012 than in 2000, a trend that will likely continue in the future. Slum dwellers frequently have to rely on unsewered communal toilets, use open spaces, or dispose of faeces in polythene bags( that is, flying toilets).
Communal toilets are not widely used, due to a lack of water, poor maintenance, and the cost to the user. Finding a suitable place to go to the toilet is especially problematic for women, causing risks related to personal security, embarrassment, and hygiene.
Industry The toxicity, mobility, and loading of industrial pollutants have potentially more significant impacts on water resources, human health, and the environment than actual volumes of wastewater. The first step is to keep the volumes and toxicity of pollution to a minimum at the point of origin, from concept to design and in operations and maintenance. This includes substitution with more environmentally friendly raw materials and biodegradable process chemicals, as well as staff education and training to address pollution-related issues.
The second step is to recycle as much water as possible within a plant, thus minimizing discharge. Small- and medium-sized enterprises( SMEs) and informal industries often discharge their wastewater into municipal systems or directly into the environment. Industries discharging into municipal systems or surface water have to meet discharge regulations to avoid fines, so in many cases end-of-pipe treatment is required at the plant before release.
In some situations, however, industries may find it more economical to pay fines than to invest in treatment to meet regulations. One notable opportunity for industrial wastewater use and recycling is the cooperation between plants through industrial symbiosis.
Agriculture Over the past half century, the area equipped for irrigation has more than doubled, total livestock has more than tripled, and inland aquaculture has grown more than twentyfold. Water pollution from agriculture occurs when fertilizers( nutrients) and other agrochemicals are applied more heavily than crops can absorb them or when they are washed away. Continued on page 17 >>
www. plumbingafrica. co. za September 2017 Volume 23 I Number 7