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# Test: Environmental Engineering & RCC- 2

## 15 Questions MCQ Test GATE Civil Engineering (CE) 2022 Mock Test Series | Test: Environmental Engineering & RCC- 2

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This mock test of Test: Environmental Engineering & RCC- 2 for GATE helps you for every GATE entrance exam. This contains 15 Multiple Choice Questions for GATE Test: Environmental Engineering & RCC- 2 (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Environmental Engineering & RCC- 2 quiz give you a good mix of easy questions and tough questions. GATE students definitely take this Test: Environmental Engineering & RCC- 2 exercise for a better result in the exam. You can find other Test: Environmental Engineering & RCC- 2 extra questions, long questions & short questions for GATE on EduRev as well by searching above.
QUESTION: 1

### Which one of the following methods gives the best estimate of population growth of a community with limited land area for future expansion?

Solution:

Since the area is limited and there is no time period specified for population estimation, therefore logistic curve method will be the best.

QUESTION: 2

### The standard turbidity produced by one mg of silicon dioxide (silica) in one litre of distilled water, is called

Solution:

1 JTU= The standard turbidity produced by one mg of silicon dioxide(silica) in one litre of distilled water.
1 FTU= The standard turbidity produced by one mg of formazine in one litre of distilled water.
Nephlometer measures turbidity in NTU and both NTU and FTU measures turbidity of instrument which uses scattering principle.

QUESTION: 3

### Water is considered ‘hard’, if its hardness is of the order of

Solution:

Water with hardness upto 75 ppm are considered soft while those with 200 ppm and above are considered hard. In between the waters are considered as moderately hard.

QUESTION: 4

The commonly used indicator for measuring iron concentration in water is

Solution:

Eriochrome black T is used to measure hardness. Phenolphthalein is used to measure alkalinity. Blue litmus is used to measure acidity of water.

QUESTION: 5

An industry has a sewage tre atment plant which produces sludge with a moisture content of 98% With the solid content remaining the sludge is thickened so that the moisture content now is 96%. It original quantity of sludge is P, what is the quantity of thickened sludge.

Solution:

QUESTION: 6

Consider the following pairs:

Q.

Which of these pairs are correct?

Solution:

QUESTION: 7

The threshold odour number (TON) for a water sample of 40 ml, diluted to standard 200 ml mixture, in which odour is just barely detectable to the sense of smell, is

Solution:

Threshold odour number represents the dilution ratio at which the odour is hardly detectable

QUESTION: 8

Which one of the following tests of water/ wastewater employs Erichrome Black T as an indicator ?

Solution:

Hardness is measured by the titration process. The titrant used is EDTA solution also known as versonate solution. Indicator used is EBT (Erichrome Black T Indicator) and the titration is assumed to complete when the colour changes from blue to red.

QUESTION: 9

The maximum permissible limit for fluoridein drinking water is

Solution:

A fluoride concentration of less than 0.81.0 ppm may be harmful and may cause dental caries (tooth decay) due to the formation of excessive cavities in the teeth of young children during calcination of their permanent teeth. Higher fluoride concentrations, greater than 1.5 ppm or so, may again be harmful, causing spotting and discolouration of teeth, (a disease called fluorosis), which with continued excessive consumption of fuorides, may even cause deformation of bones.

QUESTION: 10

MPN Index is a measure of which one of the following

Solution:

MPN (most Probable Number) is used to measure total coliform in water sample.

QUESTION: 11

A waste water sample diluted to 100 times with aeration water had an initial dissolved oxygen (DO) of 7.0 mg/L and after 5 days of incubation at 20°C, the DO was zero. The BOD of waste water is

Solution:

BOD5 = Loss of oxygen in mg/l x Dilution ratio
BOD5 = (7 - 0) x 100 = 700 mg/l

QUESTION: 12

Detention time for a sedimentation tank (continuous flow type), is given for a tank, passing a discharge = Q, and having length = L, width = B, and depth = H, as:

Solution:

The detention period (t) of a settling tank may be defined as the average theoretical time required for the water to flow through the tank length. It is that time which would be required by the flow of water to fill the tank, if there were no outflows. In other words, it is the average time for which the water is detained in the tank. Hence, it is the ratio of the volume of the basin to the rate of flow (or discharge) through the basin
∴ Detention time t for a Rectangular tank

QUESTION: 13

In lime-soda process of water softening

Solution:

Lime helps in removing the entire carbonate hardness (i.e. carbonate hardness caused by Ca as well as that caused by Mg), and it reacts with noncarbonate hardness of Mg to convert the same into non-carbonate hardness of Ca. The non-carbonate hardness of Ca is finally removed by Soda. Lime also helps in removing the free dissolved carbon dioxide, if and when it exists in the given
water

QUESTION: 14

Which of the following are the common problems associated with the operation of rapid sand-filter?
1. Air binding
2. Cracking of sand beds
3. Bumping of filter beds
4. Mud balls

Select the correct answer using the codes given below:

Solution:

Common problems associated with
filtration of waste water are:
(i) Air binding
(ii) Turbidity break through cracking of sand bed
(iii) Mudball formation
(iv) Buildup of emulsified grease
(v) Loss of filter medium due to backwashing
(vi) Gravel moulding or bumping of filter beds.

QUESTION: 15

Match List-I with List-II and select the correct answer using the codes given below the lists:
List-I
A. High turbidity low alkalinity
B. Low turbidity high alkalinity
C. High turbidity high alkalinity
D. Low turbidity low alkalinity
List-ll
1. Small number ot colloids makes coagulation difficult. Sweep coagulation is more effective
2. Prevents formation of AI(OH)3
3. Reduced pH makes small dosages of coagulant more effective
4. pH is relatively not affected when coagulant is added

Solution:

The turbidity denotes the concentration of colloids. Alkalinity is used for restoring pH after alum (coagulant) addition.
In the case of low turbidity small number of colloids make the coagulation difficult. If the alkalinity is high, moderate alum doses will result in the formation of AI(OH)3 which is amorphous and gelatinous. So sweep coagulation takes place.
High turbidity-low alkalinity: With relatively small doses of coagulant, water can be coagulated by adsorption and charge neutralization. Depression of pH makes this method more effective because aquometallic ions are more effective at low pH.
High turbidity-high alkalinity: The pH will be relatively unaffected by coagulant addition. Because of high alkalinity, adsorption and charge neutralization will be less effective than in waters of low alkalinity. Higher coagulant dosage should be used to ensure sweep coagulation.