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Questions and Answers
What property of water makes it a good solvent capable of dissolving various salts?
Which method is NOT used to remove impurities from water?
What measurement unit is commonly used to express the concentration of dissolved impurities in water?
Which of the following impurities is indicated by a yellowish tinge in water?
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What is the recommended method for removing turbidity caused by finely divided insoluble impurities?
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What is the primary reason for the soapy taste in water?
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Which organic substance is likely to lead to an earthy odor in water?
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What is the main objective of the WHO's guidelines on drinking-water quality?
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Which of the following is an example of hardness in water?
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What causes brackish water?
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What is the primary purpose of reverse osmosis in water treatment?
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Which organization provides guidelines specifically concerning water quality incidents?
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Which of the following statements about the applied electric field and charge ions is true?
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What type of matter can lead to a bitter taste in water?
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What is emphasized in the WHO's Water Safety Planning?
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What are the advantages of the reverse osmosis process?
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What mechanism allows purified water to be separated from contaminants in reverse osmosis?
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Which materials are commonly used for membranes in reverse osmosis systems?
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What is soft water capable of doing when mixed with soap?
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What causes the hardness of water?
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Which type of hardness can be removed by boiling water?
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Which of the following water hardness classifications indicates very hard water?
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What type of salts cause permanent hardness in water?
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What is the chemical treatment method for removing permanent hardness?
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How is hardness in water expressed?
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What is produced when soap reacts with hard water?
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What is the ideal maximum hardness level for boiler feed water?
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Which of the following is a consequence of sludge formation in a boiler?
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Which of the following compounds commonly forms sludge within a boiler?
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What is one of the major troubles caused by the use of unsuitable water in boilers?
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Which of the following statements about scale is true?
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What is the consequence of having high alkalinity in boiler feed water?
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What problem can excessive sludge formation cause in a boiler?
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What is the typical alkalinity concentration that should be avoided in boiler feed water?
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Study Notes
Water Impurities and Their Effects
- Water can dissolve various substances, including organic compounds, inorganic salts, and minerals, due to its excellent solvent properties.
- Common water impurities can affect taste, odor, and clarity, leading to issues such as hardness and alkalinity.
- Impurities are measured in parts per million (ppm) or milligrams per liter (mg/L) by weighing the residue after water evaporation.
Impurities and Removal Methods
- Colour: Caused by organic matter, metals, or minerals; removal methods include coagulation, settling, and filtration.
- Turbidity: Results from finely divided insoluble impurities; sedimentation and filtration are common removal techniques.
- Taste: Can be influenced by dissolved minerals and gases; varying tastes can indicate specific contaminants (e.g., bitter from iron, soapy from sodium bicarbonate).
- Odour: Arises from decaying organic matter and microorganisms; removal often requires activated carbon and aeration.
- Hardness: Presence of dissolved minerals (e.g., Ca²⁺, Mg²⁺) leading to reduced soap efficacy and may require chemical treatment for softening.
Guidelines for Drinking Water Quality
- WHO’s Guidelines for Drinking-Water Quality outline acceptable levels of contaminants and management practices for safe water supply.
- The fourth edition (2017) offers updated standards for microbial and chemical safety in drinking water.
- WHO promotes Water Safety Planning and incident response for water quality incidents.
Desalination Techniques
- Reverse Osmosis (RO) uses pressure to move water through a semi-permeable membrane, effectively removing contaminants.
- Advantages include high reliability, low operating costs, and effectiveness in removing a range of particles and ions.
Water Hardness
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Types of Hardness:
- Temporary Hardness: Caused by bicarbonate salts; can be removed by boiling.
- Permanent Hardness: Resulting from chlorides and sulphates; does not decompose upon heating and requires chemical methods for removal.
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Classification of Water Hardness:
- Soft water: 0-70 mg/L
- Moderate hard water: 70-150 mg/L
- Hard water: 150-300 mg/L
- Very hard water: >300 mg/L
Boiler Water Requirements and Issues
- Boiler feed water should have hardness below 0-2 ppm and regulated alkalinity levels.
- Major problems in boilers include:
- Priming & Foaming: Carryover of water into steam.
- Sludge Formation: Soft deposits accumulating in cold areas of the boiler, easily removed.
- Scale Formation: Hard deposits that are difficult to remove, potentially impairing heat transfer.
- Caustic Embrittlement: Damage due to excessive alkalinity in water leading to structural weakness.
Comparative Water Quality Measures
- Groundwater typically has higher total hardness (300-400 ppm) compared to surface water (75-200 ppm).
- Alkalinity levels are significantly higher in groundwater, indicating different mineral compositions.
- Degree of dissolved oxygen is often near zero in groundwater but ranges from 2-14 ppm in surface water.
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Description
Explore the principles of water hardness and its impact on soap’s effectiveness in this quiz. Learn about the difference between soft and hard water, soap composition, and how lathering occurs with different water types.
