Wastewater Story

• (a) Cleaning of water is a process of removing pollutants.
• (b) Wastewater released by houses is called sewage.
• (c) Dried sludge is used as manure.
• (d) Drains get blocked by cooking oil and fats.

Sewage is wastewater released by homes, industries, hospitals, etc. It contains suspended solids, organic and inorganic impurities, nutrients, saprophytes and disease-causing bacteria.

It is harmful because:

1. It pollutes the freshwater sources.
2. It causes water-borne diseases like cholera, typhoid, etc.
3. It harms aquatic life.

Oils and fats can harden and block the pipes. In open drains, they clog the soil pores reducing its effectiveness in filtering water. Hence, they should be thrown in the dustbin.

1. Screening: Wastewater is passed through bar screens to remove large objects like rags, sticks, cans, etc.
2. Grit Removal: Water goes to grit and sand removal tank. Speed is decreased so sand and grit settle down.
3. Sedimentation: Water is allowed to settle. Solids (sludge) settle at bottom. Floatable solids (oil/grease) are removed by skimmer.

The water so obtained is called clarified water.

Sludge is the solid waste (like human excreta) that settles at the bottom during wastewater treatment.

Treatment: It is removed using a scraper and transferred to a separate tank where it is decomposed by anaerobic bacteria. This produces biogas (can be used as fuel). Dried sludge is used as manure.

It causes water pollution and soil pollution. Both surface water and groundwater get contaminated. Drinking water sources get affected. This causes water-borne diseases like cholera, typhoid, polio, meningitis, hepatitis and dysentery.

Chlorine and Ozone.

Bar screens remove large objects like rags, sticks, cans, plastic packets and napkins from the wastewater. This prevents damage to pipes and pumps later in the plant.

Poor sanitation (lack of clean toilets, open drains, garbage heaps) leads to growth of disease-causing germs and vectors like flies/mosquitoes. This spreads diseases. Good sanitation prevents this spread and keeps us healthy.

1. Keep surroundings clean.
2. Do not litter.
3. Educate others about sanitation.
4. Report open drains to municipality.
5. Adopt good hygiene practices.

• (Across 3) Liquid waste products -> Sewage
• (Across 4) Solid waste extracted in sewage treatment -> Sludge
• (Across 6) A word related to hygiene -> Sanitation
• (Across 8) Waste water discharged from human body -> Excreta
• (Down 1) Used water -> Wastewater
• (Down 2) A pipe carrying sewage -> Sewer
• (Down 5) Micro-organisms which causes cholera -> Bacteria
• (Down 7) A chemical to disinfect water -> Ozone

(a) It is essential for breathing of living organisms. (False)
(b) It is used to disinfect water. (True)
(c) It absorbs ultraviolet rays. (True)
(d) Its proportion in air is about 3%. (False)

Correct option: (ii) (b) and (c)

• Physical Process: Screening (Bar screens), Grit/Sand removal, Sedimentation.
• Biological Process: Aeration (Aerobic bacteria consume organic waste), Sludge decomposition (Anaerobic bacteria).
• Chemical Process: Disinfection (Chlorine, Ozone).

• Don't throw oil/fats in drains (Blockage).
• Don't throw chemicals/paints (Kill helpful microbes).
• Don't throw solid waste like tea leaves, cotton, napkins (Clog drains).

• Septic Tanks: For places with no sewer system.
• Chemical Toilets.
• Composting Pits.
• Vermi-processing Toilets: Using red worms to treat human excreta (Converts to vermi-cakes/manure).

• Contaminants: Impurities in water (Organic, Inorganic, Bacteria, etc).
• Aerator: Device that pumps air into clarified water.
• Activated Sludge: Bacteria settled at bottom of aeration tank (97% water).

• World Toilet Day: 19 November.
• Eucalyptus trees can absorb surplus wastewater rapidly.
• Dried sludge is used as manure.
• Treated water is discharged into sea/river or used for irrigation.