Comprehension Passage
Sewage treatment is a critical process for managing waste water generated in cities and towns, which primarily contains human excreta and organic matter, including harmful pathogenic microbes. Directly discharging untreated sewage into rivers and streams would cause severe environmental pollution. To prevent this, sewage is treated in sewage treatment plants (STPs) through a two-stage process.Despite the effectiveness of microbial treatment, the rapid urbanization has led to an increase in sewage, often outpacing the expansion of treatment facilities. As a result, untreated sewage is sometimes discharged into rivers, exacerbating pollution and waterborne diseases
During sewage treatment, biogases are produced which include
1
Hydrogen sulfide, nitrogen, methane
2
Methane, oxygen, hydrogen sulfide
3
Methane, hydrogen sulfide, carbon dioxide
4
Hydrogen sulfide, methane, sulfur dioxide