Nitrogen
Explanation
Sewage is a liquid waste containing a complex mixture of suspended solids, organic and inorganic impurities, nutrients, saprotrophs, and disease-causing bacteria. Environmental science classifies these components into specific categories based on their chemical nature and ecological impact.
Classification of Sewage Components
- Nutrients: Nitrogen and Phosphorus are classified as nutrients. An excess of these in water bodies leads to eutrophication (excessive growth of algae), which depletes dissolved oxygen.
- Organic Impurities: This category includes human faeces, animal waste, oil, urea (urine), pesticides, herbicides, and fruit or vegetable waste. Although urea is a nitrogenous compound, it is primarily categorized as an organic impurity in the context of raw sewage composition.
- Inorganic Impurities: This includes nitrates, phosphates, and metals such as Lead or arsenic.
- Bacteria and Microbes: This includes Coliform bacteria (indicators of contamination) and pathogens like Vibrio cholerae.
Key Takeaway: In the standard classification of sewage constituents, Nitrogen and Phosphorus are explicitly labeled as "nutrients," distinct from organic impurities like urea or biological contaminants like bacteria.