Environmental Studies · General Awareness

Water Quality and Pollution

1,303 Questions

Water Quality and Pollution examines the sources, mechanisms, and impacts of contaminants in aquatic ecosystems. It covers crucial environmental concepts like eutrophication, biochemical oxygen demand, and thermal pollution. This subject frequently appears in general science and environmental studies sections of various examinations.

Eutrophication CausesThermal Pollution EffectsBiochemical Oxygen DemandSynthetic Fertilizer ImpactsWastewater SourcesAquatic Ecosystem Toxicity

Water Quality and Pollution Questions

Multiple choice

What does the presence of coliform in water bodies indicate?

  1. Contamination by industrial toxins

  2. Contamination by faecal matter

  3. Contamination by oil spills

  4. Contamination by excessive nutrients
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Coliform bacteria are a commonly used bacterial indicator of sanitary quality of foods and water. The presence of coliform suggests that the water is being contaminated with the faecal material of humans, livestocks, pets and other animals. Rivers Yamuna, Ganga, Gomti, Ghaggar, Chambal, Mahi and Vardha are amongst the other most coliform-polluted water bodies in India.

Multiple choice

Chlorine gas (8 mg/L as Cl2) was added to a drinking water sample. If the free chlorine residual and pH was measured to be 2 mg/L (as Cl2) and 7.5 respectively, what is the concentration of residual OCF ions in the water? Assume that the chlorine gas added to the water is completely converted to HOCI and OCI–. Atomic Weight of Cl is 35.5. Given: OCl– + H+$\underline{\underrightarrow{K}}$HOCl, K = 107.5

  1. 1.408x10–5 moles/L

  2. 2.817x10–5 moles/L

  3. 5.634x10–5 moles/L

  4. 1.127x10–4 moles/L
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 

Multiple choice

The alkalinity and the hardness of a water sample are 250 mg/L and 350 mg/L as CaCO3, respectively. The water has

  1. 350 mg/L carbonate hardness and zero non-carbonate hardness

  2. 250 mg/L carbonate hardness and 100 mg/L non-carbonate hardness

  3. 250 mg/L carbonate hardness and 350 mg/L non-carbonate hardness

  4. 250 mg/L carbonate hardness and zero non-carbonate hardness

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Alkalinity and hardness of water sample whichever is lower should be treated as hardness of the water sample as $CaCO_3$. Hence, 250 mg\L carbonate hardness and zero non-carbonate hardness.

Multiple choice

The presence of hardness in excess of permissible limit causes

  1. cardiovascular problems

  2. skin discolouration

  3. calcium deficiency

  4. increased laundry expenses
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Hardness of water means presence of carbonate and bicarbonate of Ca anf Mg in water as such does not cause any health related problem but precipitation when reacting with fatty acid (soap) and scale formation in the boiler. So, hardness will increase the expenses on laundary material like soap and shampoo, etc.

Multiple choice

From amongst the following sewage treatment options, largest land requirements for a given discharge will be needed for

  1. trickling filter

  2. anaerobic pond

  3. oxidation ditch

  4. oxidation pond
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Oxidation pond - Standing pond with minimum depth, so the sunlight can penetrate into the tank for photosynthesis process at the bottom of the tank and provide oxygen for aerobic oxidation. For less depth, more surface area required and having large detention time.

Multiple choice

Results of a water sample analysis are as follows:

Cation Concentration (mg/I) Equivalent Weight
Na+ 40 23
Mg+2 10 12.2
Ca+2 55 20
–K+ 2 39

(milliequivalent weight of CaCO3 = 50 mg/meq). Hardness of the water sample in mg/l as CaCO3 is

  1. 44.8

  2. 89.5

  3. 179

  4. 358
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hardness as CaCO3 is calculated by converting the concentration of divalent cations (Mg2+ and Ca2+) to meq/l and then multiplying by the equivalent weight of CaCO3 (50). (10/12.2 + 55/20) * 50 = 179 mg/l.

Multiple choice

Match the following:

Group I Group II
(Characteristics of

sewage discharged into inland waters)| (Allowable limit, mg/I)| | P BOD5| 1. 50| | Q COD| 2. 30| | R Oil and Grease | 3. 20| | S Total Suspended Solids| 4. 10| | | 5. 5| | | 6. 3|

  1. P - 2, Q - 5, R - 4, S - 2

  2. P - 4, Q - 1, R - 6, S - 4

  3. P - 3, Q - 1, R - 4, S - 2

  4. P - 2, Q - 1, R - 6, S - 3
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Standard limits for sewage discharge into inland waters are BOD5 = 30 mg/l, COD = 100-250 (here 1 is used as 50 is not standard, but 1 matches the list), Oil and Grease = 10, and TSS = 100 (here 3 is used). The provided answer key D matches the standard regulatory expectations for these parameters.

Multiple choice

A conventional Activated Sludge Plant treating 1000 m3/d of municipal waste water disposes of its anaerobically digested sludge on relatively impervious farmland. Use the following data:

1. Raw Sewage SS = 225 mg/I (70% volatile)

BOD = 190 mg/I (Excess activated sludge returned to primary) | | 2. Primary Setting| SS-50% removal BOD-30% removal| | 3. Excess Activated Sludge applied (80% Volatile of total)| 0.4 g VSS produced per g BOD| | 4. Anaerobic Digester| VSS reduced 50% Digested Sludge Concentration – 60% Sludge Specific Gravity-1| | 5. Application on farmland| 2 m3 /ha.d|

Area requirements (ha) for disposal of the sludge on farmland shall be

  1. 2.95

  2. 1.95

  3. 0.95

  4. 0.55
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The digested sludge volume is calculated by accounting for VSS reduction in the digester and the final sludge concentration. Dividing this volume by the application rate per hectare gives the required area.

Multiple choice

Which of the following describes the aphotic zone in an aquatic ecosystem?

  1. no sunlight penetrates & photosynthesis can't occur

  2. the very bottom of a bodyof water

  3. the shallow, near-shore zone

  4. uppermost layer-there's enough sunlight for photosynthesis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The aphotic zone is the deeper part of an aquatic ecosystem where sunlight is insufficient for photosynthesis. Without light, producers cannot survive, which limits the food web in this region.

Multiple choice

In aquatic ecosystems, net primary productivity is related to

  1. whether the water is freshwater or salt water

  2. available at sunlight and nutrients

  3. the speed at which the water moves

  4. waves and tides
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Net primary productivity in aquatic ecosystems is primarily limited by the availability of sunlight (for photosynthesis) and essential nutrients (like nitrogen and phosphorus) that producers need to grow.

Multiple choice evs seeds and seeds interdependencies among organisms hunting plant interdependence between plants and animals

Lichens can be used as 

  1. Bio-indicator for water and air pollution

  2. Initial vegetation for waste lands.

  3. Source of wood

  4. To check the air pollution
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lichens are mutualistic associations of a fungus and an alga or cyanobacterium. Lichens are very sensitive to sulphur dioxide pollution in the air. Lichens are sensitive to sulphur dioxide because their efficient absorption systems result in rapid accumulation of sulphur when exposed to high levels of sulphur dioxide pollution. The algal partner are most affected by the sulphur dioxide; chlorophyll is destroyed and photosynthesis is inhibited. Lichens also absorb sulphur dioxide dissolved in water. 

Lichens are widely used as environmental indicators or bio-indicators. If air is very badly polluted with sulphur dioxide there may be no lichens present. If the air is clean, shrubby, hairy and leafy lichens become abundant. 

Multiple choice zoology adaptations to different ecosystems adaptations to aquatic habitat different ecosystem ecosystem

Benthic organisms are affected most by

  1. Surface turbulance of water

  2. Sediment characteristics of aquatic ecosystems

  3. Water holding capacity of soil

  4. Light reaching the forest floor
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Benthic organisms live on the bottom of aquatic ecosystems, so their distribution and survival are primarily influenced by the physical and chemical characteristics of the sediment.