Chemistry • Year 12 • Module 8 • Lesson 6
Water Quality Parameters & Standards
Lock in the vocabulary, the classification of physical/chemical/biological parameters, and the key ADWG acceptable ranges before moving to data analysis.
1. Term–definition match
The twelve definitions below are shuffled. In the right-hand column write the matching term from this list: turbidity, dissolved oxygen (DO), biochemical oxygen demand (BOD), conductivity, total dissolved solids (TDS), pH, Australian Drinking Water Guidelines (ADWG), eutrophication, heavy metals, nephelometric turbidity unit (NTU), electrical conductivity (EC), coliform bacteria. 12 marks
| # | Definition (shuffled) | Matching term |
|---|---|---|
| 1.1 | The cloudiness of water caused by suspended particles; measured in NTU. | |
| 1.2 | The concentration of oxygen gas dissolved in water; critical for aquatic respiration (mg L−1 or % saturation). | |
| 1.3 | The amount of oxygen consumed by microorganisms decomposing organic matter over a set time period; a proxy for organic pollution load. | |
| 1.4 | A measure of the ability of a solution to carry an electric current; proportional to dissolved ion concentration (µS cm−1). | |
| 1.5 | The total mass of inorganic and organic substances dissolved in a unit volume of water (mg L−1). | |
| 1.6 | A logarithmic scale of hydrogen ion concentration; the ADWG safe drinking-water range is 6.5–8.5. | |
| 1.7 | Australia’s national framework setting maximum permissible levels for physical, chemical and microbiological water parameters. | |
| 1.8 | Excessive nutrient enrichment of a water body, promoting algal blooms and subsequent oxygen depletion. | |
| 1.9 | Dense metals (e.g. Pb, As, Hg, Cd) that are toxic even at low concentrations; strictly limited in the ADWG. | |
| 1.10 | The SI unit of turbidity measured by light scattered at 90° by suspended particles. | |
| 1.11 | Synonym for conductivity commonly used in agriculture and water-quality reporting in Australia. | |
| 1.12 | Indicator organisms found in faecal matter; their presence in drinking water signals a microbiological safety risk. |
2. True or false — with correction
For each statement, circle T or F. If the statement is false, write the correct version on the line provided. 10 marks (1 T/F + 1 correction each)
2.1 The ADWG recommends a drinking-water pH range of 5.0–9.0. T / F
2.2 Conductivity is a direct measure of which specific ions are present in water. T / F
2.3 A high BOD value indicates that a large amount of organic matter is being decomposed by microorganisms, reducing the oxygen available for aquatic life. T / F
2.4 As water temperature increases, dissolved oxygen solubility increases. T / F
2.5 Nitrate and phosphate levels are monitored as indicators of potential eutrophication. T / F
3. Classify the parameters
Complete the table by classifying each parameter as physical, chemical or biological and writing one sentence explaining what it indicates about water quality. 10 marks (1 per classification + 1 per explanation)
| Parameter | Classification (P / C / B) | What it indicates |
|---|---|---|
| Temperature | ||
| Turbidity | ||
| pH | ||
| Dissolved oxygen | ||
| Coliform bacteria |
4. Fill the blanks
Complete the paragraph using the word bank below. Each word is used once. 8 marks
Word bank: ADWG • conductivity • eutrophication • 6.5–8.5 • dissolved oxygen • BOD • TDS • NTU
Australia’s drinking-water quality is governed by the , which sets limits for physical, chemical and biological parameters. The acceptable pH range for drinking water is , outside which pipes may corrode or taste is affected. Cloudiness is reported in , and should remain below 5 units. The concentration of dissolved ions is estimated indirectly through , while the total mass of all dissolved substances is expressed as . Oxygen available for aquatic respiration is measured as . When organic matter decomposes, microbial activity consumes oxygen — this is captured by the test. Excess nutrient inputs (nitrates and phosphates) from agriculture promote algal blooms in a process called .
5. ADWG limits recall
Complete the table with the ADWG or standard guideline limit or acceptable range for each parameter. 6 marks
| Parameter | ADWG / guideline limit or range |
|---|---|
| pH | |
| Turbidity | |
| Dissolved oxygen (healthy ecosystem) | |
| Total dissolved solids (TDS) | |
| Nitrate (NO3−) | |
| Phosphate (PO43−) |
Q1 — Term–definition matches
1.1 turbidity • 1.2 dissolved oxygen (DO) • 1.3 biochemical oxygen demand (BOD) • 1.4 conductivity • 1.5 total dissolved solids (TDS) • 1.6 pH • 1.7 Australian Drinking Water Guidelines (ADWG) • 1.8 eutrophication • 1.9 heavy metals • 1.10 nephelometric turbidity unit (NTU) • 1.11 electrical conductivity (EC) • 1.12 coliform bacteria.
Q2 — True / false with correction
2.1 False. Correction: The ADWG recommends a pH range of 6.5–8.5 for drinking water.
2.2 False. Correction: Conductivity is an indirect indicator of dissolved ion concentration; it does not identify which specific ions are present.
2.3 True.
2.4 False. Correction: As water temperature increases, dissolved oxygen solubility decreases (gas solubility decreases with rising temperature).
2.5 True.
Q3 — Classify the parameters
Temperature — Physical. Indicates the thermal state of the water and affects dissolved oxygen solubility and organism survival.
Turbidity — Physical. Indicates the amount of suspended particles; high turbidity reduces light penetration and may signal runoff or contamination.
pH — Chemical. Indicates the acidity or alkalinity of the water; affects chemical equilibria, toxicity of metals and biological function.
Dissolved oxygen — Chemical. Indicates the amount of oxygen available for aerobic aquatic organisms; values below ~3 mg L−1 cause hypoxia.
Coliform bacteria — Biological. Indicates possible faecal contamination; their presence signals a microbiological safety risk for human or ecological use.
Q4 — Cloze paragraph
In order: ADWG • 6.5–8.5 • NTU • conductivity • TDS • dissolved oxygen • BOD • eutrophication.
Q5 — ADWG limits recall
pH: 6.5–8.5 (ADWG / NHMRC). Turbidity: <5 NTU. Dissolved oxygen (healthy ecosystem): >6 mg L−1. TDS: <600 mg L−1 recommended. Nitrate: <50 mg L−1 (WHO). Phosphate: <0.1 mg L−1.