Disinfection MCQ Quiz in मराठी - Objective Question with Answer for Disinfection - मोफत PDF डाउनलोड करा

Explanation:

Chlorination:

Chlorination is used for: Disinfection, control of microorganisms, removal of ammonia, control of taste and odour, destruction of organic matter, hydrogen sulphide oxidation.

Types of chlorination:

1. Plain chlorination:

This term is used to indicate that only the chlorine treatment and no other treatment has been given to the raw water

It is used for clean water, i.e turbidity between 20 - 30 mg/l

Dose is 0.5 mg/l

2. Pre-chlorination:

It is the process of applying chlorine to the water before filtration or rather before sedimentation and coagulation.

Normal dose is 5 to 10 mg/l and pre-chlorination is always followed by post chlorination

3. Post chlorination:

It is the normal standard process of applying chlorine in the end, when all other treatments have been completed.

4. Double chlorination:

It simply means that the water has been chlorinated twice

5. Break-point chlorination

It means an extent of chlorine is added to water.

It represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine.

6. Super chlorination

When excess chlorine is added to water during epidemic such that it gives a residual of 1 to 2 mg/l beyond break point is called as super chlorination.

7. Dechlorination

When chlorine residue is high, excess chlorine will be removed by dechlorinating agent.

The various dechlorinating agents are:

i) Sodium Thiosulphate (Na2S2O3H2O)

ii) Activated carbon

iii) Sulphur dioxide (SO2)

iv) Sodium bisulphate (NaHSO3)

v) Ammonia as NH4OH

vi) Sodium sulphate (Na2S2O3)

Concept:

Chlorine required = amount of water(in litre) × Chlorine demand (mg/l)

Calculation:

Amount of water to chlorinate = 20000 litre

Chlorine demand = 2 mg/l

Bleaching powder has available chlorine = 40%, which signifies that 1 gm of bleaching powder has 0.4 gm of available chlorine

So total chlorine required = 20000 × 2 = 40000 mg = 40 gm

Total Bleaching powder required = 40 × (1/0.4) = 40 × 2.5 = 100 gm

Concepts:

As per IS 2296: 1982, the surface water quality standards are classified into 5 categories which are specified below:

1. Class A – Drinking water without conventional treatment but after disinfection.

1. Class B – Water for outdoor bathing.
2. Class C – Drinking water with conventional treatment followed by disinfection.
3. Class D – Water for fish culture and wild life propagation.
4. Class E – Water for irrigation, industrial cooling and controlled waste disposal.

Explanation:

Chlorination:

Chlorination is used for: Disinfection, control of microorganisms, removal of ammonia, control of taste and odour, destruction of organic matter, hydrogen sulphide oxidation.

Types of chlorination:

1. Plain chlorination:

This term is used to indicate that only the chlorine treatment and no other treatment has been given to the raw water

It is used for clean water, i.e turbidity between 20 - 30 mg/l

Dose is 0.5 mg/l

2. Pre-chlorination:

It is the process of applying chlorine to the water before filtration or rather before sedimentation and coagulation.

Normal dose is 5 to 10 mg/l and pre-chlorination is always followed by post chlorination

3. Post chlorination:

It is the normal standard process of applying chlorine in the end, when all other treatments have been completed.

4. Double chlorination:

It simply means that the water has been chlorinated twice

5. Break-point chlorination

It means an extent of chlorine is added to water.

It represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine.

6. Super chlorination

When excess chlorine is added to water during epidemic such that it gives a residual of 1 to 2 mg/l beyond break point is called as super chlorination.

7. Dechlorination

When chlorine residue is high, excess chlorine will be removed by dechlorinating agent.

The various dechlorinating agents are:

i) Sodium Thiosulphate (Na2S2O3H2O)

ii) Activated carbon

iii) Sulphur dioxide (SO2)

iv) Sodium bisulphate (NaHSO3)

v) Ammonia as NH4OH

vi) Sodium sulphate (Na2S2O3)

Explanation:

The correct order of disinfection capacity of following compounds is HOCl > ClO2 > Cl2 > NH2Cl.

Different forms of Chlorine:

1) Bleaching powder (Hypochlorites) - 

Powdered chlorine may be chlorinated lime (bleaching powder) or its more stable variant.

OCl- and HOCl are disinfectants in this case.

They are the most effective disinfectants.

2) Free Chlorine

Either it may be in gaseous form or liquid form but liquid form is mostly used.

Free chlorine can be stored for a long time without deterioration.

3) Chloramines 

Chloramines are disinfectant compounds, which are formed by the reactions between ammonia and chlorine.

Chloramines are weaker disinfectants (25 times less than free chlorine).

4) Chlorine Dioxide (ClO₂)

It is a very effective and powerful disinfectant about 2.5 times stronger than free chlorine.

Explanation:

Super-chlorination:

• When excess chlorine (5 to 15 mg/l) is added during an epidemic such that it gives a residual of 1 to 2 mg/l beyond breakpoint is called super chlorination.
• If chlorine is applied beyond the stage of break-point, then the water is called super-chlorinated.
• It is most commonly added at the end of filtration.

Important Points

Types of chlorination:

1. Plain chlorination:

• This term is used to indicate that only the chlorine treatment and no other treatment has been given to the raw water
• It is used for clean water, i.e turbidity between 20 - 30 mg/l
• Dose is 0.5 mg/l

2. Pre-chlorination:

• It is the process of applying chlorine to the water before filtration or rather before sedimentation and coagulation.
• Normal dose is 5 to 10 mg/l and pre-chlorination is always followed by post chlorination

3. Post chlorination:

• It is the normal standard process of applying chlorine in the end, when all other treatments have been completed.

4. Double chlorination:

• It simply means that the water has been chlorinated twice

5. Break-point chlorination

• It means an extent of chlorine is added to water.
• It represents that much dose of chlorination, beyond which any further additional chlorine will appear as free residual chlorine.

6. Dechlorination

• When chlorine residue is high, excess chlorine will be removed by dechlorinating agent.

Explanation:

Disinfection with KMnO₄:

• KMnO₄ is the popular disinfectant used for the treatment of well water supply in villages that are contaminated to lesser extent.
• When KMnO4 is added in water, pink colour appears in the water.
• If the colour disappear indicates the presence of microorganism and organic matter in it.
• KMnO4 is added further up to an extent pink colour remains stable in water.
• The stand of pink colour in water indicates the removal of microorganism and organic matter from the water.
• It is advisable not to use water for 48 hours after the treatment with KMnO₄ as sufficient time is given for pink colour to subsidies (reduce).
• It's normal dose is 1-2 ppm and the contact period of 4-6 hour.
• It remove 98% of bacteria in general and 100% of cholera causing bacteria.

Explanation:

Treatment with Ozone:

• Ozone is a gas of O₃ which has a powerful oxidizing effect causing rapid and effective disinfection of clean water.
• Nascent oxygen is the powerful oxidizing agent and it removes organic matter as well as bacterias from water.
• 2-3 ppm ozone is required to maintain a residual of 0.1 ppm.
• Residual ozone is measured by orthotolidine test.
• ozone removes color, odor and taste also.
• It gives a pleasant taste to water.

Note:

• No residual can be maintained as it is highly unstable and it doesn't ensure against possible future recontamination.
• It is costlier than chlorination.

Concept:

Chlorine required = Dose × Discharge

Calculation:

Given,

Q = 25000 m³/day

Chlorine required

Chlorine required = Dose × Discharge

9 = Dosage × 25000 m³/day

Dosage per day = 9/25000 = 3.6 × 10^-4 kg/m³

1 kg/m³ = 1000 mg/l

Dosage per day = 3.6 × 10-4 × 1000 = 0.36 mg/l

Concept:

Bleaching powder or calcium hypochlorite:

• It is a chemical compound with formula CaOCl2.
•  It is widely used for water treatment and as a bleaching agent (bleaching powder).
• This is considered relatively stable and has greater available chlorine than sodium hypochlorite.
• In fresh Bleaching powder, the chlorine content is around 30 to 35%

The required amount of bleaching powder

= \(chlorine\: demand\over\: available\: chlorine \)