Water Hardness Classification: Cations, Anions, and Compounds

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Which method is used to determine the hardness of water in a simple and inexpensive way?

Water softening
Series of titrations
EDTA Titration (correct)
Geological formation

What is the main purpose of a water softener?

To purify water for drinking
To increase the pH of water
To remove minerals that cause water hardness (correct)
To remove health-hazardous substances from water

Why is softening not usually part of the treatment process for surface waters?

Because it is not cost-effective
Because surface waters seldom have hardness levels above 200 mg/L as CaCO3 (correct)
Because it is not a required part of the water treatment process
Because hard water has no health consequences

What is the result of geological formations of the water source?

Water hardness (B) Signup and view all the answers

Why is softening more common for groundwater than surface water?

Because groundwater has higher hardness levels (B) Signup and view all the answers

What is the reason for not having a single criterion for maximum hardness in public water supplies?

Because hardness levels vary widely (C) Signup and view all the answers

What is the formula used to calculate the basin surface area of a circular clarifier?

Ab = (pi)*r2 (A) Signup and view all the answers

What is the average detention time of the primary clarifier in Example 3?

2.5 hours (B) Signup and view all the answers

What is the average overflow rate of the primary clarifier in Example 3?

20 m3/day per square meter (D) Signup and view all the answers

What is the primary function of filtration in water treatment?

To remove small particles from water (D) Signup and view all the answers

What is typically used to make granular filters in water treatment?

Sand, gravel, and crushed coal (C) Signup and view all the answers

What is the shape of the clarifier being designed in Example 3?

Circular (A) Signup and view all the answers

What is the purpose of adding chlorine to water in a treatment process?

To kill any disease-causing organisms (D) Signup and view all the answers

Which of the following disinfectants is used for physical disinfection of water?

Ultraviolet light (C) Signup and view all the answers

What is the unit of measurement used to express the concentration of ions or chemicals in solution?

Milligrams per liter (C) Signup and view all the answers

What is the meaning of the term 'parts per million' in the context of water treatment?

One part by weight to 1 million parts by volume (A) Signup and view all the answers

Which of the following is NOT a disinfectant used for chemical disinfection of water?

Ultraviolet light (B) Signup and view all the answers

What is the unit of measurement used to express the amount of chlorine added to water?

Milligrams per liter (A) Signup and view all the answers

What is the primary difference between carbonate hardness and non-carbonate hardness?

The ability to be removed by boiling (A) Signup and view all the answers

Which of the following compounds is an example of a non-carbonate hardness compound?

Calcium sulfate (A) Signup and view all the answers

What is the effect of dissolved salts on the boiling point of water?

It increases the boiling point (B) Signup and view all the answers

What is the characteristic of hard water in terms of soap usage?

It requires a large quantity of soap for washing (A) Signup and view all the answers

What is the term for the type of hardness that can be removed by boiling?

Temporary hardness (A) Signup and view all the answers

What is the conventional practice for calculating water hardness?

Using the concept of equivalents and equivalent weights (B) Signup and view all the answers

What is the primary purpose of aeration in groundwater treatment?

To remove dissolved gases, such as carbon dioxide and hydrogen sulfide (C) Signup and view all the answers

Which of the following processes is not used in individual home units for softening water?

Lime-soda ash process (C) Signup and view all the answers

What is the purpose of coagulation/flocculation in groundwater treatment?

To form large particles of floc that can be easily separated from the water (A) Signup and view all the answers

What is the purpose of sedimentation in groundwater treatment?

To allow the flocs to settle and be separated from the water (C) Signup and view all the answers

What is the primary cause of hardness in water?

Calcium and magnesium ions (D) Signup and view all the answers

What is the primary purpose of softening in groundwater treatment?

To remove hardness caused by calcium and magnesium ions (A) Signup and view all the answers