The Global Water Crisis: Addressing an Urgent Security - Unu-inweh ...

1.1. Human-induced Pollutants
Domestic wastewater comprises dissolved and suspended impurities from households. Untreated or insufficiently
treated wastewater is typically contaminated with human excreta, which can cause traditional health risks. In recent
years, domestic wastewater has been observed to contain trace quantities of pharmaceutical and narcotics, which would
present health risks over prolonged exposure. However, in studies conducted in Australia, the United Kingdom and the
United States, scientists assure that such risks are highly unlikely as the level of contaminants do not approach significant
levels (WHO, 2011a).
Pollutants found in industrial wastewater can be broadly classified into three categories: chemicals and heavy metals,
organic matter, and fouling substances such as oil. The release of these pollutants into waterways varies by industry,
which runs the gamut from manufacturing to mining to power generation. In most countries, there exists standards
guiding the treatment of wastewater for release into waterways; however, these standards may not always be observed
or implemented. Thus, water sources that receive industrial effluents may become tainted, and present health risks when
used for drinking water or irrigation (see Box 2 on Contaminated Crops in India).
Box 2. Contaminated Crops in India
In Varanasi, a suburban middle-sized city in India, treated and untreated wastewater is used to irrigate crops. Over
the long term, heavy metal pollutants (cadmium, copper, lead, zinc, nickel and chromium) from the wastewater
have leached into the soil, and can be detected in significant amounts in the vegetables grown in these farms.
While concentrations vary depending on the type of vegetable grown and the part of the vegetable that was
sampled, some of the detected amounts greatly exceed allowable limits, rendering these vegetables unsafe for
consumption. Figure 1 below illustrates lead concentrations in spinach grown in Varanasi.
Source: Singh et al., 2010
concentration in microgramme per gramme
Indian standard
European Union standard
Figure 1. Concentration of lead in spinach grown in different seasons at different sites across Varanasi, India
(Source: Singh et al., 2010)
78 The Global Water Crisis: Addressing an Urgent Security Issue