GATE ES Water treatment methods PYQs & Answers

Questions 1–10 of 14. Imported answers require independent review unless marked reviewed.

Which of the following options is/are TRUE about reverse osmosis process?

Your answerSelect all correct options. You can choose more than one.

Reverse osmosis is used as a pretreatment for microfiltration process.

Ultrafiltration is used as a pretreatment for reverse osmosis process.

Membrane fouling occurs in microfiltration and reverse osmosis processes.

Concentration polarization does not occur in reverse osmosis process.

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Which of the following options is/are TRUE about coagulation-flocculation process?

Your answerSelect all correct options. You can choose more than one.

Collision of colloidal particles due to their Brownian motion results in orthokinetic flocculation.

Collision of colloidal particles due to the external mixing of bulk medium results only in perikinetic flocculation.

In an electric double layer model of a colloidal particle, Stern layer is more compact than the diffuse layer.

The zeta potential is also called Stern potential.

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A thermal process, at a specific temperature, results in 2-log₁₀ removal of non-thermotolerant pathogenic microorganisms from a water sample in 20 min. The time needed to achieve 99.999% removal of these microorganisms under similar condition is ______ min (answer in integer).

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The process of removal of particles in a rapid sand filter with their description is given in the table.

Process	Description
(i) Straining	P: Removes only particles in the water large enough to get caught in the pores of the filter
(ii) Sedimentation	Q: Larger and heavier particles do not follow the fluid streamline around the sand grain and settle on the grain
(iii) Interception	R: Particles that do follow the streamline, but are too large and are caught because they brush up against the sand grains
(iv) Diffusion	S: Very small particles are experiencing Brownian motion and may collide with the sand grains by chance

Select the correct match.

Your answerChoose one option.

i-S; ii-P; iii-Q; iv-R

i-Q; ii-R; iii-S; iv-P

i-R; ii-S; iii-P; iv-Q

i-P; ii-Q; iii-R; iv-S

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With respect to particle settling in wastewater treatment systems; the correct statement(s) is/are

Your answerSelect all correct options. You can choose more than one.

Settling in grit chamber and primary sedimentation tanks are examples of Type-I settling

Settling in primary sedimentation tank and secondary sedimentation tank are examples of Type-II settling

Settling in grit chamber is an example of Type-I settling, whereas settling in primary sedimentation tank is an example of Type-II settling

Settling in secondary sedimentation tank is an example of Type-II settling, whereas settling in primary sedimentation tank is an example of Type-II settling

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River water containing two types of spherical suspended particles (clay particles, metal particles) is retained in a sedimentation tank. The clay particles having diameter of 75 μm and specific gravity of 2.65 is settling in the tank with a constant velocity. The velocity of clay particles is 2 times of that of metal particles having specific gravity of 8. Assume discrete settling and laminar flow conditions within the sedimentation tank. The estimated diameter of the metal particles is ________________ (in μm, rounded off to integer)

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A flask (100 ml volume) has wastewater, which has 0.12 mg/L geosmin. Activated carbon is added in this flask for absorbing geosmin as per the Freundlich isotherm model (

where Q is mg adsorbate/mg adsorbent and C is the equilibrium concentration in mg/L). Activated carbon to be added in this flask for getting final remaining geosmin concentration of 0.05 mg/L would be ________________ (in mg/L, rounded off to three decimal places).

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An aeration tank needs to be installed for the removal of VOC from water, where the required rate of flow of water through the aeration tank is 180,000 m³/d. Permissible limit of VOC in the water is 12 μg/L. The saturation concentration of VOC is 5 μg/L and gas transfer rate constant is 0.40 per second at 25 °C. The initial concentration of VOC in the water is 33 μg/L. The volume of the aeration tank to satisfy the permissible limit of VOC at 25 °C is ________________(in m³, rounded off to two decimal places).

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Carbon dioxide is used in recarbonation process. A solution has 1 mole/L supersaturated calcium carbonate. Estimated amount of carbon dioxide (in grams) needed to completely convert calcium carbonate to calcium ions in 1 litre solution is

Your answerChoose one option.

44.000 gram

0.044 gram

40.000 gram

0.040 gram

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A river water sample has pH of 4 and suspended solids concentration of 100 mg/L. If, alum is chosen as a coagulant, what will be the coagulation mechanism?

Your answerChoose one option.

Ionic layer compression only

Sweep coagulation and Polymer bridging

Polymer bridging only

Charge neutralization, surface adsorption, ionic layer compression

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GATE ES Water treatment methods PYQs

How to practice Water treatment methods

Question 44

Question 45

Question 54

Question 18

Question 28

Question 35

Question 56

Question 65

Question 21

Question 22