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💧 WATER: Introduction - The Ultimate Exam Guide (K Park Style)

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PART 1: ACCEPTABILITY ASPECTS OF WATER

1. Physical - how it LOOKS, SMELLS, TASTES
2. Chemical/Inorganic - what CHEMICALS are in it
3. Microbiological - what BUGS are in it

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🔵 A) PHYSICAL PARAMETERS

• Bro, turbidity = cloudiness/murkiness of water
• Measured in NTU (Nephelometric Turbidity Unit)
• Standard: Up to 4 NTU (can be seen by naked eye)
• Permissible: up to 5 NTU
• Best: < 1 NTU
• 🔥 Trick: "4 NTU you can SEE, 5 NTU is allowed, but 1 NTU is BEST" - think 4-5-1

• Should be colorless
• Measured in TCU (True Color Unit) or Hazen unit
• Standard: up to 15 TCU or 5 Hazen unit

• Should be tasteless and odorless - simple

• Should be room temperature - simple

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🔵 B) INORGANIC CONSTITUENTS (Chemical stuff in water)

• 200 = Standard
• 250 = Taste altered
• 600 = Maximum permissible

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🔵 C) MICROBIOLOGICAL ASPECTS

• Think: R-R = Recent-Strep; Clostridium is a spoRe-foRming old/Remote bug

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PART 2: PRESUMPTIVE COLIFORM TEST

What is it?

• It's a screening test for E. coli
• It gives the probable number of coliform bacilli per 100 mL of water
• Uses McCrady's Table (statistical table) to estimate

Multiple Tube Method (MTM)

"This test is based on estimating the Most Probable Number (MPN) of coliform organisms in 100 mL of water. The test is carried out by inoculating measured quantities of the sample water (0.1, 1.0, 10, 50 mL) into tubes of McConkey's Lactose Bile Salt Broth with Bromcresol Purple as an indicator. The tubes are incubated for 48 hours."

• You take water sample
• Put it into test tubes containing Lactose broth (food for coliforms)
• 25 tubes are used (in sets of different volumes: 10mL, 1mL, 0.1mL)
• Incubate for 48 hours
• Look for: Change of color (turns YELLOW) + gas in Durham tube = Positive = Coliform present!
• Indicator used: Bromcresol Purple
• If media turns yellow + gas → Suggestive of E. coli (Presumptive positive)

Interpretation of Results (Disinfected Water):

• Think: "0 bugs - Excellent! 1-3 bugs - Ok satisfied. 4-10 - uh oh suspicious! 10+ - FAIL!"

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PART 3: CONFIRMATORY TEST

• Take each presumptive positive tube
• Subculture into 2 tubes of Brilliant Green Bile Broth
• Tube 1: Incubate at 37°C for 48 hours → Confirms coliform presence
• Tube 2: Incubate at 44°C, inspect after 6 and 24 hours → Confirms E. coli specifically

"E. coli is almost the only coliform organism which is capable of producing gas from lactose at 44°C." - K Park

• E = Eijkman test
• I = Indole production
• C = Citrate utilization

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PART 4: MEMBRANE FILTRATION TECHNIQUE

"A measured volume of water is filtered through a membrane made of cellulose ester. Bacteria present in water are retained on the surface of the membrane. By inoculating the membrane face upwards on suitable media and at an appropriate temperature, colonies are counted."

• Filter water through a membrane
• Bacteria get trapped on the membrane surface
• Place membrane on ENDO Agar
• Colonies appear as green sheen or pink mucoid with dark centers = E. coli

• Result in: 20 hours (faster than multiple tube method!)
• Media used: ENDO Agar

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PART 5: CHEMICAL CRITERIA (Toxic Metals in Water)

• Nitrates → indicate REMOTE contamination of water
• Nitrites → indicate RECENT contamination of water
• If BOTH are present: (Nitrate conc + Nitrite conc) should be ≤ 1

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PART 6: RADIOLOGICAL ASPECTS

• Gross α (alpha) activity allowed: 0.5 Bq/L
• Gross β (beta) activity allowed: 1 Bq/L

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PART 7: HARDNESS OF WATER

Definition (K Park - write this exact):

"Hardness of water is defined as the 'soap destroying power of water'."

Types of Hardness:

Levels of Hardness (expressed in meq/litre or mg/L as CaCO₃):

How to Remove Hardness:

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🎯 25 MCQs TO TEST YOURSELF

• a) Clostridium perfringens
• b) Streptococcus faecalis
• c) Coliform organisms (E. coli)
• d) Klebsiella

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• a) < 1 NTU
• b) Up to 4 NTU
• c) Up to 5 NTU
• d) Up to 10 NTU

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• a) Less than 3
• b) Less than 5
• c) Zero
• d) Less than 10

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• a) MacConkey agar
• b) Lactose broth with Bromcresol Purple
• c) Brilliant Green Bile Broth
• d) ENDO Agar

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• a) 24 hours
• b) 36 hours
• c) 48 hours
• d) 72 hours

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• a) 37°C
• b) 40°C
• c) 44°C
• d) 50°C

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• a) 12 hours
• b) 20 hours
• c) 48 hours
• d) 72-96 hours

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• a) MacConkey agar
• b) Lactose broth
• c) ENDO Agar
• d) Blood agar

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• a) E. coli
• b) Klebsiella
• c) Salmonella
• d) Proteus

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• a) Most desirable metal
• b) Maximum limit is 0.1 mg/L
• c) Most undesirable metal, limit 0.01 mg/L
• d) Causes cancer only

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• a) 100 mg/L
• b) 200 mg/L
• c) 300 mg/L
• d) 600 mg/L

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• a) 200 mg/L
• b) 250 mg/L
• c) 300 mg/L
• d) 600 mg/L

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• a) 5.5 - 7.5
• b) 6.5 - 8.5
• c) 7.0 - 9.0
• d) 6.0 - 8.0

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• a) Calcium content of water
• b) Soap destroying power of water
• c) Magnesium content of water
• d) TDS content of water

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• a) Calcium and Magnesium chlorides
• b) Calcium and Magnesium sulphates
• c) Calcium and Magnesium bicarbonates
• d) Sodium chloride

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• a) Boiling
• b) Addition of lime
• c) Permutit process
• d) Base exchange process

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• a) Dental caries
• b) Cardiovascular diseases (CVD)
• c) Malaria
• d) Typhoid

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• a) 1-2 meq/L
• b) 3-6 meq/L
• c) > 6 meq/L
• d) < 1 meq/L

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• a) Remote contamination
• b) Recent contamination
• c) No contamination
• d) Faecal contamination

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• a) 1 Bq/L
• b) 0.1 Bq/L
• c) 0.5 Bq/L
• d) 5 Bq/L

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• a) E. coli
• b) Streptococcus faecalis
• c) Klebsiella
• d) Clostridium perfringens

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• a) 0.1-0.3 mg/L
• b) 0.5-0.8 mg/L
• c) 1-1.5 mg/L
• d) 3 mg/L

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• a) 500 mg/L
• b) 600 mg/L
• c) 1000 mg/L
• d) 1500 mg/L

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• a) Lactose broth
• b) ENDO Agar
• c) Brilliant Green Bile Broth
• d) Blood agar

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• a) Excellent
• b) Satisfactory
• c) Suspicious
• d) Unsatisfactory

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🧠 MASTER MEMORY TRICKS SUMMARY

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💧 CHAPTER 48: WATER PURIFICATION METHODS

Your Ultimate Bestie Guide (K Park Style, Pages 323-330)

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THE BIG PICTURE FIRST (Overview)

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STEP 1: STORAGE OF WATER

• Water stored for 5-7 days → Impurities reduce by 90%!!
• Ideal time of storage: 10-15 days
• How does it work? Action of oxidizing bacteria (MOA = Mechanism of Action)
• Basically natural bacteria in water eat up the bad stuff when you let water sit

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STEP 2: FILTRATION

A) RAPID SAND FILTER

• Also called: Mechanical filter
• Used in: Bigger cities (because it's faster)
• More in use currently
• Source of water: Surface water (from rivers, lakes)

How Purification of Surface Water by Rapid Sand Filter Works:

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About the Filter Itself (Important Details - K Park):

• Water level in tube and filter should be the SAME
• If impurities clog the filter bed, water level in filter rises (↑), water in tube drops (↓)
• This is called Loss of Head and allowed loss of head = 6-8 feet

"Opening the air valves in the filter helps unclog impurities. This process is known as backwashing and it needs skilled operation."

Two Types of Rapid Sand Filter:

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B) SLOW SAND FILTER

• Has no technical process (simple!)
• Used in smaller towns
• Created in a big area with sand bed + gravel layer
• Effective size of sand: 0.2-0.3 mm (smaller sand than rapid!)

This layer:

• Responsible for purifying water
• Removes organic matter
• Holds back bacteria
• Oxidizes ammoniacal nitrogen into nitrates → More purification

• Done by scraping 2-5 cm of the Schmutzdecke layer off (you scrape the top layer and let it regrow)

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THE COMPARISON TABLE (This is GOLD for MCQs!!):

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STEP 3: DISINFECTION

A) CHLORINATION

"Chlorination is the most frequently used method of disinfection. Residual chlorine has to be 0.5 mg/L for a contact period of 1 hour. Used for large bodies."

• Chlorine gas is cheap, quicker, efficient, easy to apply - hence most preferred
• And Parterson chloronome is used to deliver chlorine gas
• Has RESIDUAL property - water, once treated, remains disinfected!

"Chlorine oxidizes iron, manganese, and hydrogen sulfide - Controls algae, slime organisms, and aids coagulation."

• Does NOT kill cysts, ova, or spores
• Increased chlorination can kill poliovirus/cyclops but MAY alter taste and smell

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CHLORINE ACTION:

• Chlorine is mostly used as Bleaching Powder
• 100g of Bleaching Powder releases 33g of free Cl₂
• 2.5g of Bleaching Powder disinfects 1000 L of water
• Chlorine acts best at pH 7

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MOA (Mechanism of Action) of Chlorine:

• Addition of Cl₂ to water → HOCl (Hypochlorous acid) + HCl (Hydrochloric acid)
• HCl is neutralized by water alkalinity
• HOCl dissociates into: H⁺ and OCl⁻ (Hypochlorite ion)

• 90% due to HOCl (Hypochlorous acid) - this is the MAIN disinfecting agent
• 10% due to OCl⁻ (Hypochlorite ion)

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CHLORINE DEMAND OF WATER:

"Chlorine demand is the amount of chlorine that is needed to destroy bacteria and to oxidize all the organic matter and ammoniacal substances present in water."

• Estimation of chlorine demand is done by Horrocks Apparatus

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HORROCKS APPARATUS ⭐⭐⭐

• Estimates chlorine demand of water
• Indicator: Starch Iodide
• Colour change turns BLUE (like iodine turning blue with starch!)

• 1 Black cup: For solution preparation (water + indicator)
• 6 White cups: Filled with increasing levels of water + 2 drops of solution added

• The first cup showing a colour change determines the amount of bleaching powder needed
• Formula: (n×2) grams of bleaching powder disinfects 455 liters of water
• Where n = first cup showing a colour change

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FREE / RESIDUAL CHLORINE:

"After the chlorine demand of water is estimated, some extra amount of Cl₂ is added to water so that water remains disinfected. This extra amount of Cl₂ added to water is called free or residual chlorine."

• Free Cl₂ is estimated by: Chloroscope or OT/OTA test

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TESTS FOR CHLORINATION:

• Measures free/residual chlorine
• Method: Add 0.1 mL of reagent to 1 mL of water
• Yellow colour is produced and matched against standards
• Takes reading within 10-15 seconds
• Can detect free Cl₂ separately
• Can detect combined Cl₂ but NOT separately
• Combined Cl₂ = Total Cl₂ - Free Cl₂

• OTA test is BETTER than OT test
• Detects BOTH free and combined chlorine SEPARATELY
• But is affected by interfering substances (nitrites, iron, manganese)

• Measures free/residual chlorine (simpler device)

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LEVELS OF RESIDUAL CHLORINE REQUIRED:

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SUPERCHLORINATION:

• Addition of large doses of chlorine to water AND removal of excess chlorine after disinfection
• Used for highly polluted water

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BREAK POINT CHLORINATION:

"Break point chlorination = Point at which chlorine demand is met."

• Disinfecting action of chlorine mainly due to HOCl
• Disinfecting property of Cl₂ due to HOCl and OCl⁻
• Minimum recommended concentration of free chlorine: 0.5 mg/L or 0.5 ppm for contact period of 1 hour
• Total Dose of Chlorine: Chlorine demand (combined Cl₂) + free residual chlorine of 0.5 mg/L
• Stabilized Bleach: Bleaching powder mixed with excess of lime; it retains its strength

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DIFFERENT FORMS OF CHLORINE (Chemical Disinfection):

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B) OZONATION:

• Supply ozone gas through tubes with water
• 2-2.5 mg/L of ozone gas supplied for contact time of 20 minutes
• Disadvantage: Expensive and NO residual property
• Contact time: 20 minutes

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C) ULTRAVIOLET (UV) RADIATION:

• 235 arc lamp is used
• Powerful oxidizing and strong virucidal agent
• Disadvantage: Expensive and has NO residual property
• Dose for potable water treatment: 0.2 to 1.5 mg/L

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D) MEMBRANE PROCESS:

• Semi-permeable membrane with holes through which raw water passes
• Once water permeates through this membrane, it gets purified
• Size of pores: 10⁻³ and below
• Processes: Nanofiltration / Ultra filtration / Reverse osmosis
• Disadvantage: Expensive and wastage of water

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BOILING:

"Boiling is the best method of disinfecting water but least used."

• Kills EVERYTHING → cysts, ova, spores (unlike chlorine!)

• Expensive
• No residual activity (requires re-boiling every 4-6 hours)
• Rolling boiling: Water is boiled for 10-15 mins

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PURIFICATION OF WATER ON SMALL SCALE

Disinfection of Wells:

1. Find volume of water in well:
   • Formula: πr²h (where π=3.14, r=radius, h=height)
2. Calculate amount of bleaching powder needed using Horrocks Apparatus
3. Check for disinfection by multipurpose worker (Male) in the subcentre
4. Residual level of chlorine in well should be 0.5 mg/L for contact period of 1 hour
5. Delivery of bleaching powder into well is done by DOUBLE POT METHOD

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DOUBLE POT METHOD:

• Bleaching powder + sand added to inner pot
• After superchlorination, chlorine is gradually released to outer pot via hole in inner pot
• From outer pot, gradually released to the well

• Suitable for 2-3 weeks
• Volume of well: 4500-6000 litres
• Daily water requirement: 300-450 L/day

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HOUSEHOLD WATER PURIFICATION METHODS:

1. Boiling
2. Chemical Disinfection → Most important is Chlorination
3. Household filters
4. UV radiation
5. Membrane Filtration Process (Reverse Osmosis filters)
6. Solar Disinfection (SODIS)

• Water collected in PET bottles placed in sunlight for >6 hours
• During cloudy days: PET bottles placed in sunlight for >24 hours

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HOUSEHOLD FILTERS:

1. Chamberland Filter

• It is a Porcelain filter

2. Berkefeld Filter

• Made up of Kieselguhr or infusorial earth

3. Katadyn Filter

• Portable
• Coated with silver ions and exerts its action by Oligodynamic action

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MEMBRANE FILTERS (Full Detail):

REVERSE OSMOSIS (RO) - Has FOUR cylinders:

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SWIMMING POOL SANITATION:

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WASH PROGRAMME:

• Stands for: Water, Sanitation, and Hygiene program
• Same guideline adopted in the National Water and Sanitation program
• Water source should be available to all within 30 minutes for at least 250 houses
• If not, it will lead to "problem habitation"

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SWAJALDHARA PROGRAM:

• Level I: For villages and communities
• Level II: For districts

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OZONE vs UV vs CHLORINE (QUICK COMPARISON):

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🎯 25 MCQs - TEST YOURSELF!

• a) 50% b) 70% c) 90% d) 100%

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• a) 1-3 days b) 5-7 days c) 10-15 days d) 20-25 days

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• a) Slow Sand Filter b) Rapid Sand Filter c) Berkefeld Filter d) Chamberland Filter

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• a) Sand bed b) Gravel layer c) Schmutzdecke layer d) Siphon tube

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• a) 0.1-0.2 mm b) 0.2-0.3 mm c) 0.4-0.7 mm d) 1-2 mm

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• a) Rapid Sand Filter (99%) b) Slow Sand Filter (99.9%) c) Both same d) Berkefeld filter

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• a) Slow Sand Filter b) Chamberland Filter c) Rapid Sand Filter d) Berkefeld Filter

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• a) 2-3 ft b) 4 ft c) 6-8 ft d) 10-12 ft

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• a) It kills cysts b) It has residual property c) It is most expensive d) It works only at pH 9

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• a) 10g b) 25g c) 33g d) 50g

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• a) OCl⁻ b) HOCl c) HCl d) NaOCl

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• a) Chloroscope b) OT test c) Horrocks apparatus d) OTA test

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• a) Phenolphthalein b) Starch Iodide c) Bromcresol Purple d) Methylene blue

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• a) 0.2 mg/L for 30 min b) 0.5 mg/L for 1 hour c) 1 mg/L for 1 hour d) 2 mg/L for 2 hours

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• a) 0.5 mg/L b) 0.7 mg/L c) 1 mg/L d) >2 mg/L

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• a) It is cheap b) It has residual property c) It kills cysts, ova, spores d) It improves taste

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• a) 2-3 min b) 5 min c) 10-15 min d) 30 min

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• a) 10% b) 25% c) 33% d) 60-70%

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• a) 5 L b) 10 L c) 20 L d) 50 L

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• a) Chamberland b) Katadyn c) Berkefeld d) Porcelain

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• a) UV action b) Oligodynamic action (silver ions) c) Chlorination d) Ozonation

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• a) 1-2 hrs b) 3-4 hrs c) >6 hrs d) >24 hrs

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• a) Sediment filter b) GAC filter c) Carbon block filter d) RO membrane

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• a) 15 min b) 20 min c) 30 min d) 60 min

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• a) Point at which chlorine is added b) Point at which chlorine demand is met c) Point at which water turns clear d) Point at which pH is 7

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🧠 MASTER TRICKS SUMMARY TABLE

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