From the number and nature of water recycling projects throughout the world, it can be concluded that the principle of treating wastewater as a valuable source becomes increasingly accepted. The larger demand of water due to population growth and increased comfort is translated into better protection of sources and eventually, zero discharge or nearly zero discharge systems. A remarkable observation is that in none of these projects adverse health effects were obtained, even on a long timescale. This shows that the technologies for producing clean water from wastewater are available, but not everyone is convinced (as proven in San Diego, California, and in Toowoomba, Australia). A good direction for the future to stimulate water recycling is therefore not in technology but rather in education programs and information campaigns. The success of the NEWater project in
Singapore is a good example of how it should be done: by using the appropriate technologies, but also providing the right information. The project in Koksijde, Belgium, is another example of public acceptance for water reuse.
Another conclusion to be made is the difference between developed and developing countries. Water recycling requires (expensive) technology if the effluent is to be safe and reliable. Developing countries lack infrastructure and financial means to do this, so that water recycling, where applied, is unsafe due to remaining microbiological and chemical contaminations. When used for irrigation, pollutants are spread over a large area and may affect the crops. This is common practice in parts of Asia and Africa. Ethiopia is a typical example: waste and wastewater is discharged into rivers without any treatment; pollutants accumulate and cause problems downstream where the water is to be used as the only source. Drinking water production interferes with this approach, in some cases even through direct contact between river water and drinking water (shown in Fig. 5: the pipeline for drinking water supply is below the level in the river during the wet season, contaminating drinking water with diluted wastewater).
Another typical example is Hanoi, Vietnam, where there is hardly any wastewater treatment. The continuous massive discharge of unprocessed wastewater in the Nhue-Day River (from domestic, industrial and agriculture activities from the city of Hanoi, Ha Tay and peri-urban area) has resulted into surface water that is heavily polluted. This water is used as a source for drinking water for more than 60,000 people who live near the river bank. Again, this is a case of wastewater reuse without any treatment. Solving this problem is probably the most important challenge for water recycling in the next decades.
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