Rivers have great water purification capacity – the ability to make polluted water pure – through oxygenation that occurs in waterfalls and with the receipt of better quality water from its tributaries and subaffluents. Even with this provision for purification, surface waters are the most affected by pollutants produced by urban and industrial activities. From the spring areas, rivers are altered due to multiple applications, such as energy generation, navigation, contamination by solid waste and sewage.
In the mid-twentieth century, Brazil began its late industrialization, stimulating the rural exodus and urbanization. The use of water resources took advantage of the immense potential that the Brazilian territory has for the idealization of hydroelectric projects, use of water for agriculture and the supply of population. This potential is related to a natural characteristic: the presence of humid climates in most of Brazil, configuring perennial rivers with a large volume of water.
On the other hand, successive administrations seem to have not understood that water is a finite resource, despite being renewable and abundant in a country like Brazil. The expansion of cities and the nature of the occupation of urban centers has provoked something apparently improbable: the imminence of shortage of water in metropolitan areas that do not have a water deficit - a situation that occurs only where precipitation is less than the evaporation. Rains occur, and the years are naturally dry due to seasonal weather events, such as, for example, El Niño and La Niña oscillations do not represent the main factor responsible for the reduction in water supply drinking. What is happening is an imbalance between the consumption of drinking water and the capacity of reservoirs and rivers to be replenished and purified.
The term basic sanitation covers the services of sewage collection and treatment, drinking water supply, garbage collection and cleaning of public roads. According to a report presented by the Ministry of Cities, in 2010 only 46.2% of the Brazilian population had sewage collection. In the North region, where most of the Brazilian freshwater reserves are located, data show that only 6.2% of households are provided with sewage collection.
This information reflects the sub-housing conditions of millions of people in the country, submitting this population to a low quality of life and exposure to diseases caused by contaminated water and accumulation of trash. The same report indicated that only 6 among the 100 largest Brazilian cities managed to reach a higher level 80% of sewage treatment: Curitiba-PR, Jundiaí-SP, Maringá-PR, Niterói-RJ, São José do Rio Preto-SP and Sorocaba-SP.
Society has had to get used to urban rivers that resemble open sewers, which daily receive tons of waste from artificial sources of pollution. The accumulation of organic matter in rivers, especially compounds formed by phosphorus and nitrogen, gives rise to the phenomenon of eutrophication, which prevents the passage of sunlight and hinders the oxygenation of waters. For this reason, the waters of heavily polluted urban rivers give off a very strong smell, the result of toxins eliminated by anaerobic bacteria that act as decomposing agents.
Julio César Lázaro da Silva
Brazil School Collaborator
Graduated in Geography from Universidade Estadual Paulista - UNESP
Master in Human Geography from Universidade Estadual Paulista - UNESP
Source: Brazil School - https://brasilescola.uol.com.br/geografia/saneamento-basico-poluicao-hidrica.htm