Water Quality and Treatment Methods

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Questions and Answers

Which treatment method involves a physical process to remove suspended solids from water?

  • Chlorination
  • Deionisation
  • Secondary treatment
  • Filtration (correct)

What is the role of aluminium sulphate in water treatment?

  • To remove heavy metals
  • As a flocculating agent (correct)
  • To kill bacteria
  • To adjust pH levels

Which of the following substances is not a heavy metal?

  • Cadmium
  • Sodium (correct)
  • Lead
  • Mercury

What is the primary objective of chlorination in water treatment?

<p>To kill bacteria (A)</p> Signup and view all the answers

Which process in sewage treatment is primarily biological?

<p>Secondary treatment (C)</p> Signup and view all the answers

What is the purpose of pH adjustment in water treatment?

<p>To neutralise water if too acidic or basic (C)</p> Signup and view all the answers

Which method is described as reducing levels of phosphates and nitrates in treated water?

<p>Tertiary treatment (C)</p> Signup and view all the answers

What is primarily used to detect heavy metals in environmental samples?

<p>Atomic absorption spectrometry (A)</p> Signup and view all the answers

Which of the following processes is part of the primary treatment of sewage?

<p>Screening and settling (B)</p> Signup and view all the answers

Which method is effective for removing permanent hardness in water?

<p>Deionisation and Distillation (A)</p> Signup and view all the answers

What is eutrophication primarily caused by?

<p>Over-enrichment of water with nutrients (B)</p> Signup and view all the answers

What distinguishes permanent hardness from temporary hardness in water?

<p>Temporary hardness can be eliminated by boiling (D)</p> Signup and view all the answers

What happens to calcium hydrogencarbonate when water with temporary hardness is boiled?

<p>It decomposes to form insoluble compounds (D)</p> Signup and view all the answers

What is the process of ion exchange primarily used for in water treatment?

<p>To remove permanent hardness by swapping certain ions (A)</p> Signup and view all the answers

What is the main purpose of sedimentation in water treatment?

<p>To remove suspended particles by allowing them to settle (D)</p> Signup and view all the answers

How does deionization differ from ion exchange in water treatment?

<p>Deionization removes all ions while ion exchange swaps specific ions (C)</p> Signup and view all the answers

What compounds are typically responsible for permanent hardness in water?

<p>CaSO₄, MgCl₂, and CaCl₂ (C)</p> Signup and view all the answers

What characterizes hard water in relation to soap?

<p>It forms scum instead of lather with soap (B)</p> Signup and view all the answers

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Study Notes

Eutrophication

  • Caused by over-enrichment of water with nutrients like nitrates and phosphates.
  • Can lead to harmful algal blooms, affecting aquatic ecosystems.

Hardness in Water

  • Temporary Hardness: Removable by boiling; primarily due to calcium hydrogencarbonate.
  • Permanent Hardness: Cannot be removed by boiling; requires methods like ion exchange or deionization.

Water Treatment Techniques

  • Fluoridation: Strengthens teeth and prevents decay by adding fluoride to drinking water.
  • Ion Exchange: Removes permanent hardness by swapping calcium (Ca²⁺) or magnesium (Mg²⁺) ions with sodium (Na⁺) ions.
  • Deionization: Removes all ions from water, producing demineralized water; differs from ion exchange which reduces hardness only.
  • Filtration: Removes suspended solids by passing water through beds of rock, sand, and gravel.
  • Chlorination: Addition of chlorine to water to eliminate bacteria.
  • pH Adjustment: Adjusts acidity or basicity of water through the addition of acids or bases.

Water Treatment Processes

  • Sedimentation: Removes suspended particles by allowing them to settle to the tank bottom.
  • Flocculation: Aggregates small suspended solids for easier removal, typically using agents like aluminium sulfate.

Calcium Hydroxide in Water Treatment

  • Added to raise the pH of water, used when water is too acidic to prevent pipe corrosion.

Heavy Metal Removal

  • Can be achieved through precipitation methods.
  • Examples of heavy metals include lead, mercury, and cadmium, which can be detected using atomic absorption spectrometry.
  • Includes CaCl₂, MgSO₄, CaSO₄, and MgCl₂.

Sewage Treatment Steps

  • Primary Treatment: Involves screening and settling; physical process.
  • Secondary Treatment: Biological process that oxidizes nutrients in effluent using microorganisms.
  • Tertiary Treatment: Reduces phosphates (PO₄³⁻) and nitrates (NO₃⁻) levels in wastewater.

Formation of Temporary Hardness

  • Related chemical reaction: H₂O + CO₂ + CaCO₃ → Ca(HCO₃)₂.

Processes to Remove Permanent Hardness

  • Techniques include deionization and distillation.

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