Recent studies reveal that untreated and poorly treated sewage elevates concentrations of nutrients, pathogens, endocrine disruptors, heavy metals, and pharmaceuticals in natural ecosystems. Given the global extent of sewage pollution in and near natural habitats, conservation biologists and managers must address this threat. However, because of its size, conservationists cannot solve this problem alone.
New sewage management solutions are emerging, such as waste-free toilets and resource recovery to generate fuel and drinking water; but more innovation is needed - a demand that will most effectively be reached through cross-sector collaboration.
The lack of adequate sanitation for humans is a staggering problem. At least 4.5 billion people live without or have inadequate sanitation (World Health Organization, 2015; Bill and Melinda Gates Foundation, 2020). In most of Sub-Saharan Africa, and on many tropical islands, more than 50% of the population lacks any form of sanitation (UNICEF/WHO, 2019. Even in countries with high coverage of modern sanitation facilities, poor design and lack of commitment to maintain infrastructure leads to massive pollution via discharge into surface and ground waters.
Annually, more than 4.54 109 m3 (1.2 trillion gallons) of untreated sewage, stormwater, and industrial waste flow into United States rivers because of overburdened treatment systems (Ahuja, 2014). Annually, almost 102 106 m3 (27 billion gallons) of untreated sewage flow into New York Harbor alone.
With such widespread and intense human waste entering waterways, it is not surprising that global sewage pollution models predict widespread contamination of surface water. This model predicts that almost every country likely suffers from severe contamination of surface water by sewage in at least one city, and many countries likely suffer this level of contamination over much larger areas. Waterways within the Los Angeles and San Francisco metropolitan areas, for instance, are predicted to have severe levels of contamination, on par with levels modeled for much more extensive geographical areas in China and India that completely lack sanitation. For high levels of surface water fecal contamination, the extent of contamination of surface waters is predicted to be massive in some countries.
With such widespread and intense human waste entering waterways, it is not surprising that global sewage pollution models predict widespread contamination of surface water (Kiulia et al., 2015; van Wijnen et al., 2018; Siegfried et al., 2017; Font et al., 2019; Acuña et al., 2020). For example, Kiulia et al. (2015) generated a global map of predicted fecal virus contamination values based on a model built with local population demographics and wastewater treatment type (Fig. 2A). This model predicts that almost every country likely suffers from severe contamination of surface water by sewage in at least one city, and many countries likely suffer this level of contamination over much larger areas.
Waterways within the Los Angeles and San Francisco metropolitan areas, for instance, are predicted to have severe levels of contamination, on par with levels modeled for much more extensive geographical areas in China and India that completely lack sanitation (Kiulia et al., 2015). For high levels of surface water fecal contamination, the extent of contamination of surface waters is predicted to be massive in some countries. All of India fits into this category, as does ~70% of the United Kingdom, and ~30% of the United States.
Contamination of surface waters by fecal viruses, however, is only one indicator and dimension of the pollution problem. Accompanying feces and fecal viruses in sewage discharge are a cocktail of pollutants, including endocrine disruptors, heavy metals, pharmaceuticals, and pathogens (Wear and Thurber, 2015). These chemicals, like fecal viruses, are good indicators of sewage contamination. In Puget Sound, Washington U.S.A., for instance, 25 of more than 80 contaminants found in effluent from sewage treatment plants were detected in nearby waters.
A Guest Editorial