Environment😍

Air Pollution

Types of Air Pollutants:

Air Quality Index (AQI)

• Measures the air pollution level

• Carried out by CPCB (Centre for Pollution Control Board)
• Under the Ministry of Forest, Environment & Climate Change

Parameters Measured:

1. Smoke

2. Particulate matter:
• < 2.5 µm
• & 10 µm

3. SO₂ (Sulphur Dioxide)

4. NO₂ (Nitrogen Dioxide)

5. CO (Carbon Monoxide)

6. Ozone

7. Ammonia

Most reliable

• Sulfur dioxide, smoke, and suspended particles

NOTE:

• Lead: Only metallic gas
• Not routinely measured

• CO2 not included

Air Comfort Parameters

Measuring Instrument	Parameter
Thermometer	Temperature
Psychrometer, Hygrometer Humidity ↑ → psycho avum	Humidity
Anemometer Anime → air velocity	Air velocity/movement
Kata thermometer Cheriya (low velocity) thanutha (cold air) kaattu (Kata)	Low air velocity Cooling power of air (Temperature and Humidity)
Globe thermometer Radiation to globe pic	Radiant heat

• Effective air temperature: 
• Include all except Globe thermometer
• Represents the perceived warmth or coldness of the air.

• Corrected effective air temperature (CET): 
• Include all
• Best measure for air comfort.

Greenhouse Gases

Impact

• Earth's temperature is rising due to greenhouse gases.

• These gases trap heat, causing global warming.

Important Greenhouse Gases

• Water vapor (most important)

• Carbon dioxide (CO₂)

• Methane (CH₄)

• Nitrous oxide (N₂O)

• Ground-level ozone (O₃)

Ozone Layer

• Stratospheric ozone: Protects against harmful UV radiation.
• Chlorofluorocarbons (CFCs):
• Deplete the stratosphere

Agreements to Control Greenhouse Gases

• Paris () gasgone () keto ()

1. Kyoto Protocol

• Initiative to control global warming

• Target: 90% reduction in greenhouse gas emissions

• Focus: Climate protection

2. Paris Agreement

• Global agreement to limit greenhouse gas emissions

• Aim: Keep global temperature rise <2°C

3. Glasgow Agreement (COP26, 2021)

• Continued efforts under UNFCCC

• Discussed progress on climate goals and net-zero targets

Instruments Visualized:

Kata thermometer:

• Low velocity wind speed & Cooling power of air

• Red bulb

• Cloth wrapped around the bulb (wet)

• Dry

Anemometer: 

• Used to measure wind speed.

Water Quality

• Purest water in Nature
• Rain water

Requirement:

• Rural: 40 – 55 L/person/day

• Urban: 150 – 160 L/person/day

Water Quality Parameters:

• Physical:
• Color: < 15 true color units (TCU/ 5 Hazen unit)
• Temperature: Room temperature
• Odor: Absent
• Turbidity: <5 Nephelometric turbidity units (NTU)

• Biological
• Coliforms (E. coli)
• Should be completely absent.
• Most reliable evidence for fecal contamination
• Fecal streptococci
• Recent (Nearby) contamination
• Clostridium perfringens
• Remote (Distant) contamination

• Chemical:
• Chlorination
• Hardness

Definitions

• Safe and Wholesome Water
• Colorless, odorless, tasteless
• Free from pathogenic organisms
• Suitable for cooking and other domestic purposes

• Potable Water
• 0 coliforms / 100 ml of water

Important Information

• The most undesirable metal in water is lead

• Nitrates in drinking water indicate: Remote contamination(<45mg/L)

• Nitrites in drinking water indicate: Recent contamination(<3mg/L)

• If both are present, the amount should be <1 mg/L

Langelier Saturation Index (SI)

• Tank water → Lang

• Water temperature

• Total dissolved solids

• Alkalinity / pH

• Calcium hardness

• - 0.3 to +0.3 → Stable (neither corrosive nor scale-forming)

• < - 0.3 → Corrosive

• > + 0.3 → Scale-forming

Safe Yield

• Quantity of water supply sufficient to serve 95% of the population expected at the end of the design period

• Design period: 10 to 50 years in the future

1. Step Well

• Banned

• Source of: Guinea worm disease

2. Sanitary Well

• Properly constructed

• Well-protected from contamination

• Within 60 m, not more than 100 m (to avoid contamination during transport)

• At least 15 m (50 ft) away from sources of contamination (e.g., drains)

Public Health Classification of Water and Diseases

Water Purification on a Small Scale

Boiling

• Best method of purification

• Kills everything (bacteria, viruses, ova, spores)

• Limitations:
• High cost
• No residual activity → requires re-boiling after 4–6 hours

Chlorination

• Second best method

• Residual activity present
• no need for re-treatment
• Due to free chlorine

• Details:
• To kill poliovirus or cyclops
• higher chlorine dose needed
• Alters taste and smell
• Most commonly used form: Bleaching powder
• 100 g bleaching powder → 33 g chlorine
• 2.5 g bleaching powder → treats 1000 L water
• Kills: Only pathogenic forms (mainly E. coli)
• Does not kill:
• Ova
• Cyclops
• Spores
• Best activity at pH 7

Other Methods

• Ozone

• UV rays

Water Chlorination

Mechanism of Chlorination:

• Breakpoint chlorination
• Point at which the chlorine demand of water is met

pH	Predominant form of chlorine	Germicidal activity
<7.0	Cl₂ (chlorine gas)	Very high
7.2–7.6	HOCl (hypochlorous acid) ↑↑	Maximum (most potent form)
7.8	HOCl ↓ + hypochlorite ion ↑	Activity starts dropping
≥8.0	Mostly OCl⁻	Markedly reduced

• At breakpoint chlorination, there is formation of:
1. Free radicals:
• Kills microorganisms.
• Hypochlorous acid >>
• Hypochlorite ions
2. Residual chlorine compounds:
• Free residual chlorine compounds (FRC)
• Combined residual chlorine compounds (CRC)
3. Free chlorine
• Responsible for residual activity
• keep the water disinfected.

• After breakpoint chlorination
• additional chlorine is added to the water in the form of free or residual chlorine

Water Disinfection: Chlorine Demand Estimation

Chlorine Demand:

• Measured by: Horrock's apparatus
• Determines amount of bleaching powder required to disinfect 455 L of water

Equipment

• 1 Black cup

• 6 White cups (same size, marked with increasing levels)

• Indicator: Starch iodide

Procedure

• Step 1: In the black cup,
• mix:
• Water to be disinfected
• Starch iodide indicator

• Step 2: Fill each white cup with increasing amounts of water

• Step 3: Add 2 drops of the solution from the black cup into each white cup

Observation

• Look for blue color change in the white cups

• The first white cup that turns blue = ‘n’ value

Interpretation

• Formula:
• (n × 2) grams of bleaching powder disinfects 455 L of water

Level of Chlorination:

Free or Residual Chlorine Estimation:

• Colour change identifies chlorine levels.

• Measures residual chlorine compounds.
• Combined chlorine & Free/Residual Chlorine.

• Tests:
1. Chloroscope
2. Orthotoluidine test: 
• OT test
• Detects FRC & CRC together.
3. Orthotoluidine-Arsenate test: 
• OTA test
• Detects FRC & CRC separately.

Chlorination Ineffective In:

• Sporing organisms

• Protozoal cysts

• Helminths

• Ova

• Mollusca

• Cyclops

• Cercariae

• Hepatitis A

• Poliovirus

Hardness of Water

Types:

• Note: Carbonate/phosphate hardness is rare.

• Ca and Mg salts
• Temporary: Bicarbonates
• (not carbonate)
• Permanent: Sulphates/nitrates/Phosphate

Level of Hardness:

• 1 meq = 50 mg Ca(CO₃)
• (carbonate, not bicarbonate)

• MAX HARDNESS = 150 ppm/mg/L

• Softening of water is done when > 3

Treatment:

1. Boiling

2. Addition of lime

3. Addition of sodium carbonate

4. Permutit process/Ion exchange method:
• Most sophisticated
• Best method

Water Sample Collection Protocol

From Regularly Used Taps

• Let water flow for at least 2 minutes before collection

• Hold the bottle at its base with one hand

• Collect water from a gentle stream (avoid splashing)

• Do not collect from leaky taps

From Non-Regularly Used Taps

• Sterilize the tap before collection
• Use a blow lamp
• Or use cotton soaked in methylated spirit

Sand Filter, Light & Housing

Sand Filter

Light

• Minimum amount of light required: > 100 lux

Housing

Housing Criteria:

• Cattle: >25 metres away.

• Water source: <50 metres.

• Ventilation: Mixed type
• Exhaust
• Plenum

• Door area: > 1/5th of floor area

• Window area: > 1/5th of floor area
• Together: >2/5th of floor area

Overcrowding:

Based on:

• Gender based:
• 2 persons
• age > 9 years
• of opposite gender
• sharing same room
• (Except: Husband & wife).

• Space based:
• 1 person: < 70 ft³
• 2 persons: < 110 ft³
• ≥3 persons: 70 + (40 x n)
• n = extra persons

Assessment of Overcrowding – Person per Room Criterion

• M/c and easy method to assess the degree of overcrowding

• Definition:
• Number of persons per room =
• Total persons in household ÷ Total number of rooms

Waste Disposal

Types of Waste:

• Solid:
• Garbage: Organic compostable waste (Kitchen waste)
• Rubbish: Non-compostable (Tissue, clothes, Rubber, plastic, paper, metal, glass tubes)
• Ash: Powdered waste

• Liquid:
• Sewage (Black water): Fecal matter
• Sullage (Grey water): Kitchen water

Solid Waste Disposal:

Dumping: 

• Non-sanitary

Sanitary Landfills / Controlled Tipping

• Machines used

• Types:
• Trench Method



• Most commonly used.
• Buried in dug ground.
• End product is manure, used in farming.
• Costly.
• Area Method:
• Requires 1 acre/10,000/year
• Disadvantage: Requires supplemental earth from an outside source.
• Ramp Method:
• Used in less available areas
• Suited for moderately sloping terrain.

Burning

• Incineration: 
• Burning at 1000°C
• Not preferred in India as manure is not generated.

• Inertization: 
• Mixing of chemical waste with cement.

• Pulverization:
• Mutilation/shredding
• Done for metallic waste

Composting:

• Example: 
• Bangalore method



• Layering method
• Municipal garbage is layered with night soil, dung, earth.
• Anaerobic hot fomentation process (Time consuming)
• Indore Method:
• Aerobic process

Manure Pits

• Solid waste → in rural areas.

• Two pits dug → back of the houses.

• Garbage, cattle dung, straw, and leaves are put in the pit daily and covered.

• Usually takes 6 months to convert to manure.

Burial Method

• In camping.

• A trench of 2-meter depth and 1.5-meter width dug.

• Get filled in at least one week

Sewage

• Sewage
• Liquid waste with excreta.
• (Sullage: Liquid waste without excreta).
• Composition 
• 99.9% water
• 0.1% solid

Strength of Sewage

• Expressed in three terms:
1. Biological oxygen demand (BOD)
• Amount of oxygen required for
• microbial metabolism at 20°C for 100gms of sewage in 5 days.

BOD	Sewage
< 100 mg/L	Weak
100 – 500 mg/L	Moderate
> 500 mg/L	Strong

2. Chemical oxygen demand (COD)
• Best estimated by potassium dichromate.
3. Suspended solids

Key Points

• Most important test for sewage:
• BOD

• Most practical test for organic load in presence of toxic substances:
• COD

• Most efficient for reducing organic matter:
• Aerobic process

• For highly concentrated sewage with plenty of solids:
• Anaerobic process

Sewage Disposal

Primary Treatment:

• Screening

• Grit chamber

• Primary sedimentation

Secondary Treatment:

• Effluent from primary sedimentation tank subjected to aerobic oxidation
• Aerobic digestion
• Main mechanism of STP.
• Most important step
• Addition of O₂ to kill coliforms.
• Done by:
1. Activated sludge process
• Preferred
• Aeration tanks: Core component
• Retention period in aeration chamber: 6–8 hours

2. Trickling filters
• Secondary method of sewage disposal.
• Percolating filter with fixed bed of rocks, gravel, coke, and slag.
• Depth: 1-2 meters.
• Diameter: 2-30 meters.
• Disadvantage: Occupies a very large space.

• Secondary sedimentation

• Sludge digestion:
• Anaerobic digestion.

• Effluent disposal.

Important

• Activated Sludge Process
• Preferred as it occupies less space
• Requires skill
• Suited for: Larger cities
• Efficiency:
• 1 acre of activated sludge plant = 10 acres of percolating filters

• Trickling Filter Process
• Cheaper
• Easier
• Does not require skill
• Preferred in: Small towns

Other Methods:

Modern Sewage Treatment Plants

• Screen

• Grit chamber

• Primary sedimentation tank

• Biological treatment

• Final sedimentation tank

• Sludge digester

• Methane gas

• Sludge drying beds

Other Methods of Sewage Disposal

Oxidation Ponds

• Used for: Purifying sewage in small communities

• Population range: 5000–20000

Also known as:

• Waste stabilization ponds

• Sewage lagoons

• Redox ponds

Land Requirement:

• Oxidation ditch: 1 acre

• Oxidation pond: 22 acres

• Aerated lagoons: 2.5 acres

• Mechanism:
• Natural method using photosynthesis for sewage treatment
• Aerobic during day
• Anaerobic during night
• In deeper areas
• Localised anaerobic process

Septic Tank

• Process inside tank:
• Anaerobic digestion

• Process outside tank:
• Aerobic oxidation

• Used in: Smaller communities without access to a sewage treatment plant

• Capacity: Up to 500 gallons of sewage

• Retention time: 24 hours

• Separation:
• Solid sludge settles down
• Greasy material rises to top

• Cleaning:
• Done once every year
• Called sludging

• Sludge disposal:
• By trenching

Dry Weather Flow (DWF)

• Amount of sewage that flows through pipeline in a 24-hour period under normal (dry) conditions

Environment Sanitation Programs

• Kayakalp: 
• Sanitation and cleanliness in public hospitals.

• Swachh Bharat: 
• Cleanliness, sanitation, and solid waste management in the country.

• Nirmal Gram: 
• Cleanliness and sanitation with a safe water supply in villages.