Learning Objectives
- Understand what wastewater is and how it is generated
- Learn about water treatment processes
- Know about sanitation and its importance
- Understand ways to minimise water pollution
Key Concepts
Wastewater
Wastewater (sewage): Used water from homes, industries, and agriculture that contains dissolved and suspended impurities.
Contaminants: Organic impurities (human waste, food waste, oil), inorganic impurities (nitrates, phosphates, metals), nutrients, bacteria, and other microorganisms.
Sewerage: The network of pipes that carries wastewater from homes to the treatment plant.
Wastewater Treatment (WWTP)
Step 1 - Bar screening: Large objects like rags, sticks, and plastic removed by passing through bar screens.
Step 2 - Grit and sand removal: Water flows slowly allowing grit and sand to settle down.
Step 3 - Primary treatment (Sedimentation): Solids settle as sludge. Floatable solids (oil, grease) are removed. Water is called clarified water.
Step 4 - Secondary treatment (Aeration): Air is pumped into clarified water. Aerobic bacteria consume organic waste. Sludge is removed again.
Step 5 - Disinfection: Water is treated with chlorine or ozone to kill remaining bacteria before releasing into water bodies.
Sludge treatment: Sludge is decomposed by anaerobic bacteria to produce biogas (used as fuel) and dried sludge is used as manure.
Sanitation
Importance: Proper sanitation prevents waterborne diseases like cholera, typhoid, dysentery, and polio.
Open drains and poor sanitation contaminate groundwater and spread diseases.
Vermi-processing toilet: Uses earthworms to decompose human waste.
What You Can Do
- Do not throw cooking oil, chemicals, or paint down the drain
- Do not throw solid waste in drains
- Use minimum water
- Ensure proper disposal of waste
Summary
Wastewater contains harmful contaminants. Treatment involves physical (screening, sedimentation) and biological (aeration, bacterial decomposition) processes. Treated water is disinfected before release. Proper sanitation prevents disease. Everyone must reduce water pollution by responsible disposal of waste.
Important Terms
- Sewage: Wastewater containing impurities
- Sewerage: Pipeline network for wastewater
- Sludge: Solid waste that settles during treatment
- Aeration: Pumping air to help bacteria decompose waste
- Biogas: Gas produced from sludge decomposition
Quick Revision
- Treatment: Screening → Grit removal → Sedimentation → Aeration → Disinfection
- Sludge → Anaerobic bacteria → Biogas + Manure
- Sewage ≠ Sewerage (water vs pipes)
- Don't throw oil, chemicals, solids in drains
- Poor sanitation → waterborne diseases