1
GATE CE 2025 Set 1
MCQ (More than One Correct Answer)
+1
-0
Aeration is employed as a treatment option for the removal of several pollutants from contaminated water. Identify the pollutant(s), where aeration is employed as a part of their removal:
A
Iron
B
Cadmium
C
Manganese
D
Zinc
2
GATE CE 2025 Set 1
MCQ (More than One Correct Answer)
+2
-0

$\mathrm{MgCl}_2$ and $\mathrm{CaSO}_4$ salts are added to 1 litre of distilled deionized water and mixed until completely dissolved. Total Dissolved Solids (TDS) concentration is $500 \mathrm{mg} / \mathrm{l}$, and Total Hardness (TH) is $400 \mathrm{mg} / \mathrm{l}$ (as $\mathrm{CaCO}_3$ ). The amounts of $\mathrm{MgCl}_2$ and $\mathrm{CaSO}_4$ added are calculated (rounded off to the nearest integer). Which of the following options is/are true:

Atomic weights: $\mathrm{Ca}(40), \mathrm{Mg}(24), \mathrm{S}(32), \mathrm{O}(16), \mathrm{Cl}(35.5), \mathrm{C}(12)$

A
Amount of $\mathrm{MgCl}_2$ added is 143 mg
B
Amount of $\mathrm{CaSO}_4$ added is 357 mg
C
Amount of $\mathrm{MgCl}_2$ added is 103 mg
D
Amount of $\mathrm{CaSO}_4$ added is 397 mg
3
GATE CE 2025 Set 1
MCQ (More than One Correct Answer)
+2
-0
A facultative pond system is employed for wastewater treatment. Which of the following statements is/are true:
A
The dissolved oxygen concentration will be high during daytime compared to nighttime
B
The pH will be high during daytime compared to night-time
C
The dissolved oxygen concentration will be low during daytime compared to nighttime
D
The pH will be low during daytime compared to night-time
4
GATE CE 2025 Set 1
MCQ (More than One Correct Answer)
+2
-0

Organic fraction of municipal solid waste (OFMSW) with bulk density of $315 \mathrm{~kg} / \mathrm{m}^3$ and water content of $30 \%$ is mixed with municipal sludge of bulk density $700 \mathrm{~kg} / \mathrm{m}^3$ and water content of $70 \%$, such that the water content of the mixture is $40 \%$. The amount (in kg ) of sludge to be mixed per kg of OFMSW (rounded off to 2 decimal places) and the density of the mixture (in $\mathrm{kg} / \mathrm{m}^3$ ) (rounded off to the nearest integer) are calculated. Which of the following options is/are true:

A
0.33 kg of sludge added per kg of OFMSW
B
Density of the mixture is $365 \mathrm{~kg} / \mathrm{m}^3$
C
0.66 kg of sludge added per kg of OFMSW
D
Density of the mixture is $450 \mathrm{~kg} / \mathrm{m}^3$
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