Water Treatment and Disinfection Methods

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Questions and Answers

What are the two main categories of source water mentioned for disinfection?

Surface water and groundwater (correct)

Treated water and untreated water

Industrial water and potable water

Sea water and rainwater

Which of the following is NOT a stage of water treatment?

Filtration

Coagulation

Distillation (correct)

Sedimentation

Which of the following methods is a physical disinfection method?

Chemical dosing

Ozone treatment

Chlorination

Boiling (correct)

What is formed when chlorine is added to water?

Hydrochloric and hypochlorous acids (A) Signup and view all the answers

What does residual chlorine refer to?

The rest of active chlorine after disinfection (D) Signup and view all the answers

What is referred to as chlorine demand in the context of water disinfection?

The amount of chlorine consumed by oxidation reactions (C) Signup and view all the answers

Which of the following is NOT a type of chemical disinfectant used in China?

Bromine (B) Signup and view all the answers

What is a key reason for adding chlorine to drinking water during disinfection?

To prevent bacteria regeneration and reproduction (A) Signup and view all the answers

What is the ideal concentration of residual chlorine in water after disinfection?

0.3 mg/L (C) Signup and view all the answers

Which reagent is used to react with residual chlorine for detection?

o-tolidine role biphenyl quinone solution (C) Signup and view all the answers

How long should the water sample be left to mix with bleach solution before adding the o-tolidine solution?

30 minutes (B) Signup and view all the answers

What is the purpose of the Residual Chlorine Comparator in the procedure?

To detect color depth indicating chlorine levels (A) Signup and view all the answers

What is the formula used to calculate the bleach disinfectant dose needed for achieving a residual chlorine concentration of 0.3 mg/L?

Bleach dose (mg/L) = 1000CV/100 (D) Signup and view all the answers

Which concentration of bleach solution is used in the procedure?

0.01% (D) Signup and view all the answers

What is a key precaution mentioned regarding the Residual Chlorine Comparator?

It is a rough measurement instrument (B) Signup and view all the answers

What is the total volume of o-tolidine solution added to the disinfected water sample during detection?

0.5 mL (D) Signup and view all the answers

Study Notes

Disinfection of Drinking Water

Surface water and groundwater require purification and disinfection; sometimes special treatments are needed.
Improving water sources is about easily acquiring good water quality, convenient use, and easy hygiene management.
Water treatment involves four stages: coagulation, sedimentation, filtration, and disinfection.
A diagram (Figure 2-11) shows the stages of water treatment at a water treatment plant, it shows the sequence.
Disinfection is a method of killing pathogenic microorganisms.
Methods of drinking water disinfection in China include physical (boiling, ultraviolet) and chemical (chlorine, chlorine dioxide, ozone) methods.
Common disinfectants in China include liquid chlorine, bleaching powder, and bleaching powder concentrate.
Chlorine reacts with water to form hydrochloric acid and hypochlorous acid. Hypochlorous acid then ionizes into hydrogen ions and hypochlorite ions.
Bleaching powder and bleaching powder detergent turn into hypochlorous acid in water.
Chlorination has a bactericidal effect. The chlorine compounds have the ability to kill bacteria.
Chlorine demand is the amount of available chlorine consumed by oxidizing organic and reduced inorganic matters in water.
Residual chlorine refers to the leftover active chlorine after disinfection. It prevents bacteria from regenerating and reproducing.
A method to determine the best disinfection concentration is to use different amounts of bleach solution in water samples, wait 30 minutes, then measure the residual chlorine (ideally 0.3mg/L).
Residual chlorine can react with o-tolidine to create a color change. The depth and color produced are used to quantify the chlorine level.
The residual chlorine comparator is used to measure color depth.
Materials needed include Erlenmeyer flasks (250 mL, 5), volumetric cylinders (100 mL, 1), measuring pipettes (5 mL, 1), residual chlorine comparators (1), graduated tubes (10 mL, 5).
Reagents include 0.01% bleach solution, dilute with water to 100 mL; 0.1% o-tolidine/role biphenyl quinone solution mixed with HCl (3:7).
Procedure includes adding bleach to water samples, mixing, waiting 30 minutes, adding o-tolidine solution, mixing, waiting 10 minutes, and measuring color depth using a residual chlorine comparator.
The best bleach solution concentration for disinfection is 0.3 mg/L.
The experimental report should include principle, procedure, and results.
To calculate needed bleach solution dose, the formula is: Disinfection(mg/L)=1000CV/100, C (concentration mg/ml) = 0.1 mg/ml, V (mL): Volume of bleach solution needed.
Residual Chlorine Comparators are rough measuring devices.

Precautions

Residual Chlorine Comparators are rough measurement instruments.
The optimal residual chlorine level in disinfected water is 0.3 mg/L.
Handle the residual chlorine comparators carefully.

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Description

Explore the essential processes involved in the disinfection of drinking water. This quiz covers the stages of water treatment, various disinfection methods utilized in China, and the chemical reactions involved in chlorine disinfection. Test your knowledge on how to ensure safe drinking water through proper purification.