Chapter 13 – The Story of Wastewater

Chapter 13 – The Story of Wastewater

 

1. What is Wastewater? (What is Wastewater?)

•  Wastewater is water that becomes dirty after use, such as water from toilets, laundry water, kitchen water, water from factories.
• It is  also called sewage.
• Different types of impurities dissolved or suspended in wastewater   are called  contaminants.

 

2. What is Sewage? (What is Sewage?)

• Sewage is the wastewater that includes domestic waste, industrial waste, hospital waste, rainwater that flows on the road (stormwater), etc.
• It is  a complex mixture consisting of organic and inorganic impurities.
•  Impurities in Sewage:
  • Organic impurities: human feces, animal waste,  oils, urea, pesticides, herbicides, fruit and vegetable waste.
  • Inorganic impurities: nitrates, phosphates, metals.
  • Nutrients: phosphorus, nitrogen.
  • Bacteria:  Disease-causing bacteria such as cholera, typhoid, etc.
  • Other microorganisms: various pathogens .

 

3. Water Our Lifeline

• Water is very important for human existence.
• Clean and safe drinking water is a basic need.
• Unavailability of water and contaminated water can lead to serious health problems, such as water-borne diseases such as cholera, typhoid, jaundice, etc.

 

4. Sewage Disposal: A Challenge

• Releasing untreated sewage directly into rivers or the sea is very harmful to the environment and human health.
• It pollutes the water bodies and harms the aquatic life.

 

5. Wastewater Treatment Plant (WWTP)

• Wastewater treatment plants or sewage treatment plants (STPs) are places where wastewater is treated before it is released into the environment  to remove impurities from it.
• The process of treatment takes place in several stages:

1. Bar Screens:

• • • The wastewater is first passed through the screen for the first time.
    • These remove large items such as pieces of cloth, poles, plastic bags, cans, etc.

1. Grit and Sand Removal:

• • • The wastewater is sent to a tank where the movement of water slows down.
    • This causes sand, grit (gravel) and small stones to settle down.

 iii.  Solid Removal Sedimentation:

• • • The water is sent to a large, sloping tank.
    • In this, solid wastes such as faeces  settle down and form  sludge. This sludge is scraped and separated and sent to a separate tank where it is decomposed by  anaerobic bacteria (bacteria that survive without oxygen), producing biogas.
    • Light floating substances such as oil and grease float to the top and are removed by a  skimmer.
    • The water obtained in this phase is  called  clarified water.

1. Aeration Tank:

• • • The clarified water is sent to an airborne tank.
    • In this, air is pumped so that aerobic bacteria (bacteria that survive in the presence of oxygen)  grow in the water.
    • These bacteria digest human waste, food waste, soap, and other unwanted substances.
    • After several hours, bacterial flakes and other microorganisms settle at the bottom of the tank, called  activated sludge.

6. Better Sanitation Practices

• Sanitation means waste disposal, especially the safe disposal of human waste.
• Importance of Good Hygiene Practices:
  • Preventing the spread of diseases.
  • Keeping the environment clean.
  • Protecting drinking water sources from contamination.
• Steps for Hygiene:
  • Using public toilets.
  • Do not defecate in the open.
  • Do not discharge sewage directly into the drains.
  • Maintain personal and community hygiene.

 

 

7. Alternative Wastewater Disposal Arrangements

• Where there are no sewage systems, alternative arrangements for waste disposal are used:
  • Septic Tanks : These are suitable for single households or small communities where there is no underground sewage system.
  • Chemical toilets: These contain chemicals to break down human waste.
  •  Composting pits:  Used in some rural areas to convert human waste into compost.
  •  Bio-toilets:  These are developed by the Indian Railways that decompose human waste into biogas and water by bacteria.

 

8. Sanitation at Public Places

• Disposal of wastewater and solid waste at public places like railway stations, bus stands, hospitals is a major challenge.
• It is very important to ensure cleanliness and hygiene at these places.