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Complete Environment Marathon Quiz

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Question 1

A certain water needs alum treatment to the extent of 12 ppm. How much alum, in quintals per day, would be needed to treat 15 MLD of water?

Question 2

Consider the following statements:

a. Presence of nitrogen in a waste sample is due to the decomposition of proteins and carbohydrates.

b. When BOD/COD =0, waste water is toxic.

Which of the above statements are correct?

Question 3

A waste water sample has BOD₄ equal to 70 mg/L and the reaction rate constant k(base e) is 0.285 per day, the ultimate BOD of the given sample is _______mg/L.

Question 4

A water sample has concentration of OH ^— ion measured on 0.17 mg/L at 25°C. What is the pH of the water sample?

Question 5

For a sample of water, the ionic composition is shown below. The carbonate and non-carbonate hardness (in mg/l as CaCO₃) respectively are

Question 6

In a sewer, the maximum discharge is about _______% greater than the discharge of sewage running half full.

Question 7

A horizontal flow clarifier treats wastewater in which 15%, 60% and 25% of particles have settling velocities of 0.12 mm/sec, 0.22 mm/sec and 1.11 mm/sec respectively. The total percentage of particles removed, if clarifier operates at a surface overflow rate (SOR) of 55 m³/m² d will be

Question 8

A city has population of 2,00,000 and water demand is 225 lpcd. If the water contains 7 mg/l alkalinity as CaCO3, determine the quantity of quick lime required for the treatment if water is treated using coagulation with alum having a dosage of 22 mg/l. State your answer in kg per day correct upto two places after decimal.

Question 9

There are two samples with different pH. If 300 ml sample A with pH 4.2 is 400 ml sample B with pH 10.4.The pH value of the mix will be (Correct upto two places after decimal)

Question 10

A sedimentation tank is required to be designed for the treatment of raw water having suspended solids of specific gravity 2.3 and diameter 200

. The temperature conditions are 10°C. Determine the settling velocity of water in cm/sec. It is given that kinematic viscosity of water is 4.7

10-5 N-s/m2.

Question 11

A continuous flow sedimentation tank is 4 m deep and 56 m long. The flow velocity observed is 1.13 cm/s. If the kinematic viscosity is 0.01 cm²/s, then what size of particle of specific gravity 2.64 may be effectively removed?

Question 12

A waste water plant produces 950 kg of dry solids per day at a moisture content of 92%. The solids are 60% volatile with a specific gravity of 1.1 and the remaining are non-volatile with a specific gravity of 2.54. What is the volume (in m³) of sludge after digestion, which reduces volatile solids content by 40% and decreases the moisture to 90%?

Question 13

A stream with a flow rate of 5 m³/s is having an ultimate BOD of 30 mg/litre. A wastewater discharge of 0.20 m3/s having BOD₅ of 500 mg/litre joins the stream at a location and instantaneously gets mixed up completely. The cross-sectional area of the stream is 40 m² which remains constant. BOD exertion rate constant is 0.3 per day (logarithm base to e). The BOD (in mg/litre, round off to two decimal places) remaining at 3 km downstream from the mixing location, is .

Question 14

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 ____________

Question 15

What will be the future population of a satellite town (in thousands) using geometric increase method for the year 2051, from the flowing data.

Question 16

A rectangular sedimentation tank is designed for a surface overflow rate (surface overloading) of 400 litre/hour/m². The percentage of the suspended particles of diameter 0.01 mm that will be removed in the tank is ___________.
[Take kinematic viscosity of water = 1 mm²/sec and specific gravity of particle = 2.65]

Question 17

In the process of water softening, lime is used to remove calcium hardness by the reaction:
CaO + Ca(HCO₃)₂→ 2CaCO₃ + H₂O
The dose of lime with 82% purity of CaO required to combine with 72 mg/l of Calcium as Calcium carbonate in mg/l is
[Given atomic weight : H = 1; C = 12; O = 16; Ca = 40)

Question 18

A sewage disposed in a stream having flow velocity 0.15 m/sec results in the ultimate first stage BOD of the mix at the point of discharge ‘L’ as 100 mg/l and initial oxygen content of the mix at the mixing point ‘D₀’ is 4.2 mg/l and saturation D.O. is 9.2 mg/l. Also, the reoxygenation coefficient of the river ‘KR’ is 0.2/day and deoxygenation coefficient of waste water ‘K_D’ is 0.1/day. The critical oxygen deficit (in mg/l)
is ________.

Question 19

The present population of a community is 28000 with an average water consumption of 4200 m³/d. The existing water treatment plant has a design capacity of 6000 m³/d. It is expected that the population will increase to 44000 during the next 20 years. The number of years from now when the plant will reach its design capacity, assuming an arithmetic rate of population growth, will be

Question 20

Water samples (X and Y) from two different sources were brought to the laboratory for the measurement of dissolved oxygen (DO) using modified Winkler method. Samples were transferred to 300 ml BOD bottles. 2 ml of MnSO₄ solution and 2 ml of alkaliodule–azide reagent were added to the bottles and mixed. Sample X developed a brown precipitate, whereas sample Y developed a white precipitate.
In reference to these observations, the correct statement is

Question 21

A standard multiple-tube fermentation test was conducted on a sample of water from a surface stream. The results of the analysis for the confirmed test are given below.
$Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\Civil Engg\Civil Engineeing-04-Apr\Civil-Engineering-2004_files\image270.png$
MPN Index and 95% confidence limits for combination of positive result when five tubes used per dilutions (10 ml, 1.0 ml, 0.1 ml)

Using the above MPN Index table, the most probable number (MPN) of the sample is

Question 22

Chlorine gas used for disinfection combines with water to form hypochlorous acid (HOCl).

The HOCl ionizes to form hypochlorite (OCl^–) in a reversible reaction:
$Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\Civil Engg\Civil Engineeing-04-Apr\Civil-Engineering-2004_files\image277.png$ ,
the equilibrium of which is governed by pH. The sum of HOCl and OCl^– is known as free chlorine residual and HOl is the more effective disinfectant. The 90% fraction of HOCl in the free chlorine residual is available at a pH value

Question 23

An aerobic reactor receives wastewater at a flow rate of 500 m³/d having a COD of 2000 mg/L. The effluent COD is 400 mg/L. Assuming that wastewater contains 80% biodegradable waste, the daily volume of methane produced by the reactor is

Question 24

Column I
P. Grit chamber
Q. Secondary
R. Activated sludge
S. Trickling filter

Column II
1) Zone settling
2) Stoke’s law Settling tank
3) Aerobic Process
4) Contact stabilisation
The correct match of Column I with Column II

Question 25

The composition of a certain MSW sample and specific weights of its various components are given below.
$Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\Civil Engg\Civil Engineeing-01-Apr\Civil-Engineering-2006-01-Apr-1_files\image251.png$
Specific weight (kg/m3) of the MSW sample is

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ESE & GATE CE Environmental Engineering

Jan 11ESE & GATE CE