Past Year Questions: Quality Characteristics of Water

# Past Year Questions: Quality Characteristics of Water | Environmental Engineering - Civil Engineering (CE) PDF Download

Q. 1  Analysis of a water sample revealed that the sample contains the following species.

Concentrations of which of the species will be required to compute alkalinity?   [2019 : 1 Mark, Set-II]
(a)
(b)
(c)
(d)

Ans:  (a)
Alkalinity is defined as ability of water to neutralize the acid or hydronium ion
Alkalinity (AT) of water =   [organic anions]+ [OH-]+ [H+]
From given options of ions in problem answer is (a).

Q. 2  A water sample analysis data is given below

The carbonate hardness (expressed as mg/L of CaC03, up to one decimal place) for the water sample is ______  [2018 : 2 Marks, Set-I]

Ans: 273.4 mg/l

Carbonate hardness = min. (Total hardness, alkalinity)

Total hardness

Q. 3 As per IS 10500:2012, for drinking water in the absence of alternate source of water, the permissible limits for chloride and sulphate, in mg/L, respectively are   [2018 : 1 Mark, Set-II]
(a) 250 and 200
(b) 1000 and 400
(c) 200 and 250
(d) 500 and 1000

Ans: (b)
As per IS-10500 : 2012, Table 2
Permissible limit in absence of alternate source.

Q. 4 The analysis of a water sample produces the following results:

The total hardness (in mg/l as CaC03) of the water sample is _______.    [2017 : 2 Marks, Set-I]
Ans: 300mg/l

Milligrah per milli-equivalent of the ion
= equivalent weight
∴ Milliequivalent of Ca2+ = 60/20 = 3
and, milliequivalent of Mg+2 36.6/12.2 = 3

Total hardness (due to Mg2+ and Ca2+)
= Milliequivalent of Ca2+ and Mg2+
= 3 + 3 = 6 milliequivalent/l
= (6 x 50) mg/l as CaC03
= 300 mg/l as CaC03

Q. 5 Effluent from an industry ‘A’ has a pH of 4.2. The effluent from another industry 'B' has double the hydroxyl (OH-) ion concentration than the effluent from industry ‘A'. pH of effluent from the industry ‘B’ will be _________     [2016 : 2 Marks, Set-I]
Ans: 4.5

Q. 6  A sample of water has been analyzed for common ions and results are presented in the form of a bar diagram as shown

The non-carbonate hardness (expressed in mg/l as CaCO3) of the sample is      [2016 : 2 Marks, Set-Il]
(a) 40
(b) 165
(c) 195
(d) 205
Ans: (a)

Hardness is due to multivalent metallic cations,
i.e. Ca2+ and Mg2+

Total hardness (mg/l as CaC03)
= (Total meq/l) x (eq. weight of CaC03 in mg)
= (4.1) x 50 mg/l as CaC03
= 205 mg/l as CaC03

Alkalinity is due to the presence of  in this case
Alkalinity (mg/l as CaC03)
= 3.3 x 50 mg/l as CaC03
= 165 mg/l as CaC03 Now, non-carbonate hardness
= Total Hardness in excess of alkalinity
= 205 - 165

= 40 mg/l as CaC03

Q. 7  A groundwater sample was found to contain 500 mg/L total dissolved solids (TDS). TDS (in %) present in the sample i s _______ . [2015 : 1 Mark, Set-II]
Ans: 0.05%
1 kg = 1 litre
TDS (in %) in the sample

Q. 8  For a sample of water with the ionic composition shown in the figure below, the carbonate and noncarbonate hardness concentrations (in mg/I as CaCO3), respectively are:       [2014 : 2 Marks, Set-I]

(a) 200 and 50
(b) 175 and 75
(c) 75 and 175
(d) 50 and 200

Ans: (b)

Total hardness
= 5 meq/l (due to Ca2+ and Mg2+)
= (5 x 50) mg/l as CaC03
= 250 mg/l as CaC03

Alkalinity (due to HCO3-)

= 3.5 Meq/l
= (3.5x50) mg/l as CaC03
= 175 mg/l as CaC03

Carbonate hardness
= Min. (tota hardness, Alkalinity)
= Minimum (250,175)
= 175 mg/l as CaC03
Non-carbonate hardness
= Total hardness - Carbonate hardness
= 250-175

= 75 mg/l as CaC03

Q. 9  Some of the nontoxic metals normally found in natural water are
(a) arsenic, lead and mercury   [2014 : 1 Mark, Set-I]
(b) calcium, sodium and silver
(c) cadmium, chromium and copper
(d) iron, manganese and magnesium
Ans: (d)

Although manganese is toxic, but only in very high concentration. And it is also a necessary consituent is water.

Hence, according to the options available, best possible answer is (d)

Q. 10  Match the given water properties in Group-I to the given titrants shown in Group-ll.    [2013 : 1 Mark]

(a) P-1, Q-2, R-3, S-4
(b) P-2, Q-1, R-4, S-3
(c) P-3, Q-4, R-1, S-2
(d) P-4, Q-3, R-2, S-1

Ans: (c)

Q. 11 A water sample has a pH of 9.25. The concentration of hydroxyl ions in the water sample is    [2012 : 2 Marks]
(a) 10-9.25moles/L
(b) 10-4.75 moles/L
(c) 0.302 mg/L
(d) 3.020 mg/L
Ans:
(c)
pH = 9.25
∵ pH + pOH = 14
⇒ pOH = 1 4 - 9 . 2 5 = 4.75

= 30.226 x 10-5
= 30.226 x 10-6 gm/lit
∴ [OH-] = 302.6 x 10-3 mg/lit
= 0.302 mg/lit

Q. 12 Anaerobically treated effluent has MPN of total coliform as 106/100 mL. After chlorination, the MPN value declines to 102/100 mL. The percent removal (%R) and log removal (log R) of total coliform MPN is    [2011 : 1 Mark]
(a) %R = 99.90; log R = 4
(b) %R = 99.90; log R = 2
(c) % R = 99.99; log R = 4
(d) % R = 99.99; log R = 2

Ans: (c)

= 0.9999 x 100 = 99.99%
log R = log 106 - log 102
= 6 - 2 = 4

Q. 13 Ion concentrations obtained for a groundwater sample (having pH = 8.1) are given below

Carbonate hardness (mg/L as CaC03) present in the above water sample is
(a) 205
(b) 250
(c) 275
(d) 289    [2010 : 2 Marks]
Ans: (a)

Total alkalinity in water consists of alkalinity caused by  A little negative alkalinity is also caused by H+.
∴ Total Alkalinity

Carbonate hardness is equal to the total hardness or alkalinity, whichever is less. The carbonate hardness of the sample will be 205 mg/L Non-carbonate hardness
= Total hardness - carbonate hardness
= 275 - 205 = 70 mg/L

Q. 14 Ion concentrations obtained for a groundwater sample (having pH = 8.1) are given below

Total hardness (mg/L as CaC03) present in the above water sample is

(a) 205
(b) 250
(c) 275
(d) 308 [2010 : 2 Marks]
Ans: (c)

Total hardness

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## FAQs on Past Year Questions: Quality Characteristics of Water - Environmental Engineering - Civil Engineering (CE)

 1. What are the quality characteristics of water?
Ans. The quality characteristics of water refer to various parameters that determine the purity and suitability of water for different purposes. These characteristics include physical properties like color, odor, and taste, as well as chemical properties such as pH level, dissolved solids, and presence of contaminants like heavy metals or bacteria.
 2. How does water color indicate its quality?
Ans. Water color can provide valuable information about its quality. Clear and colorless water is generally considered safe and of good quality. However, the presence of unusual colors like brown, yellow, or green may indicate the presence of impurities, organic matter, or pollution, suggesting poor water quality.
 3. What is the significance of pH level in water quality?
Ans. pH level is a measure of the acidity or alkalinity of water. It is an important indicator of water quality as it affects the solubility of minerals and chemicals in water, as well as the biological processes that occur within it. The pH level of water should be within a specific range to ensure its suitability for various uses, such as drinking, irrigation, or industrial processes.
 4. How can the presence of dissolved solids impact water quality?
Ans. Dissolved solids in water can have both natural and man-made origins. While certain minerals and salts are beneficial and essential for human health, excessive levels of dissolved solids can affect the taste, odor, and overall quality of water. High levels of dissolved solids may also indicate the presence of pollutants or contaminants, making the water unsuitable for consumption or other purposes.
 5. What are the common contaminants that can affect water quality?
Ans. Water can be contaminated by various substances, including heavy metals (such as lead, mercury, or arsenic), pesticides, fertilizers, industrial chemicals, bacteria, viruses, and parasites. These contaminants can pose significant health risks and impact the quality of water for drinking, bathing, or other uses. Regular testing and treatment are necessary to ensure safe and high-quality water.

## Environmental Engineering

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