In the developed world, human waste usually travels through a series of sewer pipes after it is flushed down the toilet. The waste then travels to a treatment facility where the water is cleaned before being pumped back into local water reservoirs. In the developing world, many areas lack such sanitation technology; therefore, the residents use latrines or isolated areas. In these cases, the waste decomposes slowly.
Although the process varies from one facility to the next, most waste treatment operations clean the water by first filtering the water, then using bacteria to decompose the solids. Finally, some combination of chlorine, oxygen and ultraviolet radiation is used to kill any microorganisms that are still present. The water is then discharged into local rivers or lakes. Sometimes, farmers use the solids that were filtered from the waste water as fertilizers for their crops.
Often, waste treatment facilities must also accommodate runoff water from the roads and the “gray water” from sinks and showers. Accordingly, heavy rains can overwhelm the system, causing untreated, bacteria-laden water to enter local waterways. This damages local ecosystems and often causes local residents to become sick.
In underdeveloped regions without proper sanitation technology, people are at great risk for illness. According to LiveScience, 1.4 million children die each year as a result of untreated human waste.