MCQ Bank

In dissolved air flotation, air is dissolved into water under pressure and then released by depressurization. This sudden pressure drop causes the dissolved air to form fine bubbles.

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Gamma radiations are used for_________.

A) Dewatering
B) Thickening
C) Conditioning
D) Disinfection

AI Explanation

Gamma radiation can be used to destroy microorganisms by damaging their DNA. Therefore, it is applied as a disinfection method in wastewater and sludge treatment.

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--------- process is an appropriate method for sludge stabilization in nurseries, horticulture and landscaping.

A) Thermal drying
B) Anerobic digestion
C) Lime stabilization
D) Composting

AI Explanation

Composting stabilizes organic sludge through controlled biological decomposition. The resulting material can be beneficially used in nurseries, horticulture, and landscaping.

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Principle mechanism of influence in the dewatering process is called -------.

A) Evaporation
B) Stabilization
C) Percolation
D) Drying beds

AI Explanation

Percolation is a key mechanism in sludge dewatering, where liquid moves through the sludge and drainage medium. This removes water and increases the solids concentration of the sludge.

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Which of the following sludge management stage include removal of organic matter?

A) Thickening
B) Conditioning
C) Dewatering
D) Stabilization

AI Explanation

Sludge stabilization is specifically intended to reduce or remove biodegradable organic matter and pathogens. It makes sludge less putrescible and safer to handle and dispose of.

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Lime stabilization is used to treat______ sludge.

A) Primary
B) Digested
C) Secondary
D) All

AI Explanation

Lime stabilization can be applied to primary, secondary, and digested sludge. Lime raises the pH and helps reduce pathogens and odours, improving sludge stability.

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In primary treatment system, primary sludge takes how much time for sludge removal from liquid phase?

A) Days
B) Years
C) Months
D) Weeks

AI Explanation

In primary treatment, primary sludge settles rapidly and is removed from the liquid phase within a relatively short period. Sludge removal is generally carried out within days rather than months or years.

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Normal temperature required in the thermophilic aerobic digestion process is --------------.

A) 35-45 0C
B) 50 -60 0C
C) 80-90 0C
D) 70-80 0C

AI Explanation

Thermophilic aerobic digestion operates at elevated temperatures compared with mesophilic digestion. The typical thermophilic range is approximately 50–60 °C.

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------following chemicals are added in the sludge preparation process.

A) Sulphur
B) Polyelectrolytes
C) Coagulants
D) Both a&c

AI Explanation

Sulphur and coagulants can be used as chemicals in sludge preparation processes. Therefore, the option combining both is the correct choice.

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Thickening in sludge management is removal of ________.

A) Water
B) Non-organic matter
C) Organic matter
D) Pathogenic organisms

AI Explanation

Sludge thickening primarily removes water from sludge to increase its solids concentration. It reduces sludge volume before subsequent treatment processes such as digestion or dewatering.

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Q10

…………..involves heating of the sludge to 70 0C for 30 minutes.

A) Maturation ponds
B) Sterilization
C) Pasteurisation
D) Chlorination

AI Explanation

Pasteurisation involves heating sludge to a specified temperature for a set period to reduce pathogenic organisms. A common sludge pasteurisation condition is about 70 °C for 30 minutes.

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Q11

Stages of sludge processing involve?

A) All
B) Digestion and dewatering
C) Final disposal
D) Thickening

AI Explanation

Sludge processing includes several stages such as thickening, digestion, dewatering, and final disposal. These stages collectively reduce sludge volume, stabilize organic matter, and prepare it for safe disposal or beneficial use.

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Q12

Which of the following sludge management stage accomplished through the removal of the biodegradable organic matter of the sludge?

A) Conditioning
B) Dewatering
C) Thickening
D) Stabilization

AI Explanation

Sludge stabilization is the stage designed to remove or biologically degrade biodegradable organic matter. This reduces putrescibility, odours, and potential health risks associated with untreated sludge.

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Q13

For sludge stabilization, chemical stabilization is accompanied by ……. of an organic matter. ororganic matter?

A) Reduction
B) Oxidation
C) Bacteria
D) Both B& C

AI Explanation

Chemical stabilization involves chemical reactions that help reduce the biodegradable nature of organic matter in sludge. Oxidation is a key mechanism by which organic matter can be stabilized.

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Q14

A process in sludge management for preparation for dewatering is known as_________.

A) Conditioning
B) Disinfection
C) Dewatering
D) Stabilization

AI Explanation

Sludge conditioning is performed before dewatering to improve the release of water from sludge. It commonly uses chemicals or other treatments to enhance the efficiency of dewatering.

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Q15

---------is the principle component to inactivate the pathogenic microorganisms in the composting.

A) Ozonisation
B) Pressure
C) Tempersture(55-650C)
D) UV radiation

AI Explanation

Temperature is the principal factor responsible for inactivating pathogenic microorganisms during composting. Maintaining temperatures around 55–65 °C for an adequate period promotes pathogen destruction.

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Q16

A sludge with a solids load of 120 kgSS/d and a solids concentration of 2.0 % (20,000 mg/L) will have a flow of?

A) 4.0 m3/d
B) 6.0 m3/d
C) 5.0 m3/d
D) 7.0 m3/d

AI Explanation

A 2.0% solids concentration is approximately 20 kg solids per m³ of sludge. With a solids load of 120 kg/d, the flow is 120 ÷ 20 = 6.0 m³/d, so the correct option is actually B.

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Q17

Which of the following sludge management stage include preparation for dewatering?

A) Stabilization
B) Thickening
C) Dewatering
D) Conditioning

AI Explanation

Sludge conditioning is the preparation step performed before dewatering. It alters sludge properties, often through chemical or physical treatment, to improve water release during dewatering.

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Q18

---------- metallic coagulants is/are used in conditioning of sludge.

A) Aluminium sulphate
B) Ferrous chloride
C) Ferric chloride
D) Both A& B

AI Explanation

Metallic coagulants such as aluminium sulphate and ferrous chloride can be used in sludge conditioning. They promote floc formation and improve the separation of water from solids.

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Q19

..........is the main natural water removal mechanism/s in the sludge dewatering.

A) Digestion
B) Percolation
C) Landfill
D) Incineration

AI Explanation

Percolation is a natural mechanism for removing water from sludge during dewatering, particularly in systems such as drying beds. Water moves through the sludge and drainage layer under gravity.