Recent questions and answers in Environmental Engineering

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1

GATE2017 CE-1: 55
The wastewater having an organic concentration of $54$ mg/l is flowing at a steady rate of $0.8 \: m^3/day$ through a detention tank of dimensions $2m \times 4 m \times 2 m$. If the contents of the tank are well mixed and the decay constant $0.1$ per day, the outlet concentration (in mg/l, up to one decimal place) is _________

answered Jun 28, 2020 in Water and Waste Water by Vipin6419 (140 points)

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2

GATE2020-CE-1-25
A river has a flow of $1000$ million litres per day (MLD), $BOD_5$ of $5\:mg/litre$ and Dissolved Oxygen (DO) level of $8\:mg/litre$ before receiving the wastewater discharge at a location. For the existing environmental conditions, the saturation ... complete mixing of wastewater and river water, the immediate DO deficit (in $mg/litre$ round off to two decimal places), is ______.

asked Feb 28, 2020 in Environmental Engineering by jothee (2.7k points)

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3

GATE2020-CE-1-54
A stream with a flow rate of $5\:m^3/s$ is having an ultimate BOD of $30\:mg/litre$. A wastewater discharge of $0.20\:m^3/s$ having $BOD_5\:\text{of}\:500\:mg/litre$ joins the stream at a location and instantaneously gets mixed up completely. The ... $e$). The BOD (in mg/litre, round off to two decimal places) remaining at $3\:km$ downstream from the mixing location, is __________

asked Feb 28, 2020 in Water and Waste Water by jothee (2.7k points)

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4

GATE2020 CE-2-16
The relationship between oxygen consumption and equivalent biodegradable organic removal (i.e.,BOD) in a closed container with respect to time is shown in the figure Assume that the rate of oxygen consumption is directly proportional to the amount of degradable organic matter and is expressed as ... is $BOD_5 = L_5$ $BOD_t = L_0-L_t$ $L_0 = L_te^{-kt}$ $L_t = L_0(1-e^{-kt})$

asked Feb 13, 2020 in Environmental Engineering by jothee (2.7k points)

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5

GATE2020 CE-2-17
A gas contains two types of suspended particles having average sizes of $2\: \mu m$ and $50\: \mu m$. Amongst the options given below, the most suitable pollution control strategy for removal of these ... bag filter electrostatic precipitator followed by venturi scrubber electrostatic precipitator followed by cyclonic separator bag filter followed by electrostatic precipitator

asked Feb 13, 2020 in Air Pollution by jothee (2.7k points)

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6

GATE2020 CE-2-53
A waste to energy plant burns dry solid waste of composition: Carbon $= 35\%$, Oxygen $= 26\%$ , Hydrogen $= 10\%$, Sulphur $= 6\%$, Nitrogen $= 3\%$ and Inerts $= 20\%.$ Burning rate is $1000\: $ tonnes/d. Oxygen in air ... The stoichiometric (theoretical) amount of air ( in tonnes/d, round off to the nearest integer) required for complete burning of this waste is ________.

asked Feb 13, 2020 in Environmental Engineering by jothee (2.7k points)

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7

GATE2020 CE-2-54
A sample of water contains an organic compound $C_8H_{16}O_8$ at a concentration of $10^{-3}\: \text{mol/litre}$. Given that the atomic weight of $C = 12\: \text{g/mol}, H = 1\: \text{g/mol}$, and $O = 16\: \text{g/mol}$, the theoretical oxygen demand of water (in $g$ of $O_2$ per litre, round off to two decimal places), is ________.

asked Feb 13, 2020 in Environmental Engineering by jothee (2.7k points)

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8

GATE2017 CE-2-8
As per Noise Pollution (Regulation and Control) Rules $2000$ of India, the day time noise limit for a residential zone, expressed in dB(A)L$_{eq}$, is $55$ $65$ $75$ $85$

asked Aug 7, 2019 in Noise Pollution by gatecse (3.9k points)

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9

GATE2017 CE-2-9
Following observations have ben made for the elevation and temperature to ascertain the stability of the atmosphere: $\begin{array}{|c|c|} \hline \text{Elevation (in m) } & \text{Temperature (in }^{\circ} \text{C)} \\ \hline 10 & 15.5 \\ \hline 60 & 15.0 \\ \hline 130 & 14.3 \\ \hline \end{array}$ The atmosphere is classified as Stable Unstable Neutral Inverse

asked Aug 7, 2019 in Environmental Engineering by gatecse (3.9k points)

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10

GATE2017 CE-2-10
The most important type of species involved in the degradation of organic matter in the case of activated sludge process is autotrophs heterotrophs prototrophs photo-autotrophs

asked Aug 7, 2019 in Water and Waste Water by gatecse (3.9k points)

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11

GATE2017 CE-2-50
The composition of a municipal solid waste sample is given below: ... The difference between the energy content of the waste sample calculated on dry basis and as-discarded basis (in kJ/kg) would be _______

asked Aug 7, 2019 in Environmental Engineering by gatecse (3.9k points)

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12

GATE2019 CE-1: 18
Which one of the following is a secondary pollutant? Ozone Carbon Monoxide Hydrocarbon Volatile Organic Carbon (VOC)

asked Feb 14, 2019 in Air Pollution by Arjun (2.8k points)

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13

GATE2019 CE-1: 34
Sedimentation basin in a water treatment plant is designed for a flow rate of $0.2 \: m^3/s$. The basin is rectangular with a length of $32 \: m$, width of $8 \:m $, and depth of $4 \: m$. Assume that the settling velocity of these particles is governed by ... diameter $25 \mu m$ (spherical and uniform), the removal efficiency of these particles is $51 \%$ $65 \%$ $78 \%$ $100 \%$

asked Feb 14, 2019 in Water and Waste Water by Arjun (2.8k points)

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14

GATE2019 CE-1: 38
A box measuring $50 \: cm \times 50 \: cm \times 50 \: cm$ is filled to the top with dry coarse aggregate of mass $187.5 \: kg$. The water absorption and specific gravity of the aggregate are $0.5 \%$ and $2.5,$ respectively. The maximum quantity of water (in kg, round off to $2$ decimal places) required to fill the box completely is __________

asked Feb 14, 2019 in Water and Waste Water by Arjun (2.8k points)

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15

GATE2019 CE-1: 39
A portal frame shown in figure (not drawn to scale) has a hinge support at joint P and a roller support at joint R. A point load of $50 \: kN$ is acting at joint in R in the horizontal direction. The flexural rigidity. EI, of each number is $10^6 \: kNm^2$. Under the applied load, the horizontal displacement (in mm, round off to $1$ decimal place) of joint R would be _________

asked Feb 14, 2019 in Environmental Engineering by Arjun (2.8k points)

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16

GATE2019 CE-1: 40
A sample of air analysed at $0^{\circ} C$ and $1 \: atm$ pressure is reported to contain $0.02 \: ppm$ (parts per million) of $NO_2$. Assume the gram molecular mass of $NO_2$ as $46$ and its volume at $0^{\circ} C$ and $1 \: atm$ pressure as $22.4$ litres per mole. The equivalent $NO_2$ concentration (in microgram per cubic meter, round off to $2$ decimal places) would be ________

asked Feb 14, 2019 in Environmental Engineering by Arjun (2.8k points)

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17

GATE2019 CE-1: 42
A wastewater is to be disinfected with $35 \: mg/L$ of chlorine to obtain $99 \%$ kill of micro-organisms. The number of micro-organisms remaining alive $(N_t)$ at time $t$, is modelled by $N_t=N_o e^{-kt}$, where $N_o$ is number of micro-microorganisms at $t=0$, ... $1.0 \: m$, respectively, the length of the tank (in $m$, round off to $2$ decimal places) is ________

asked Feb 14, 2019 in Water and Waste Water by Arjun (2.8k points)

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18

GATE2019 CE-2: 9
Which one of the following options contains ONLY primary air pollutants? Hydrocarbons and nitrogen oxides Hydrocarbons and ozone Ozone and peroxyacetyl nitrate Nitrogen oxides and peroxyacetyl nitrate

asked Feb 12, 2019 in Air Pollution by Arjun (2.8k points)

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19

GATE2019 CE-2: 10
Analysis of a water sample revealed that the sample contains the following species. $CO_3^{2-}, Na^+, H^+, PO_4^{3-}, Al^{3+}, H_2CO_3, Cl^-, Ca^{2+}, Mg^{2+}, HCO_3^-, Fe^{2+}, OH^-$ ... $CO_3^{2-}, H^+, H_2CO_3, HCO_3^-$ $CO_3^{2-}, H_2CO_3, HCO_3^-, OH^-$ $H^+, H_2CO_3, HCO_3^-, OH^-$

asked Feb 12, 2019 in Water and Waste Water by Arjun (2.8k points)

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20

GATE2019 CE-2: 32
Chlorine is used as the disinfectant in a municipal water treatment plant. It achieves $50$ percent of disinfection efficiency measured in terms of killing the indicator microorganisms (E-Coli) in $3$ minutes. The minimum time required to achieve $99$ percent disinfection efficiency would be $9.93$ minutes $11.93$ minutes $19.93$ minutes $21.93$ minutes

asked Feb 12, 2019 in Water and Waste Water by Arjun (2.8k points)

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21

GATE2019 CE-2: 40
A water treatment plant treats $6000 \: m^3$ of water per day. As a part of the treatment process, discrete particles are required to be settled in a clarifier. A column test indicates that an overflow rate of $1.5 \: m$ per hour would produce the desired removal of ... of $3.0 \:m$. The volume of the required clarifier, (in $m^3$, round off to $1$ decimal place) would be ______

asked Feb 12, 2019 in Water and Waste Water by Arjun (2.8k points)

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22

GATE2019 CE-2: 41
Raw municipal solid waste (MSW) collected from a city contains $70 \%$ decomposable material that can be converted to methane. The water content of the decomposable material is $35\%$. An elemental analysis of the decomposable material yields the following mass percent. ... The mass of methane produced (in grams, round off to $1$ decimal place) per kg of raw MSW will be _________

asked Feb 12, 2019 in Environmental Engineering by Arjun (2.8k points)

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23

GATE2019 CE-2: 42
Consider the reactor shown in the figure. The flow rate through the reactor is $Q \: m^3/h$. The concentrations (in $mg/L$) of a compound in the influent and effluent are $C_0$ and $C$, respectively. The compound is degraded in the reactor following the first order ... $L_{\text{CMFR}}/L_{\text{PFR}}$ (round off to $2$ decimal places) is ____________

asked Feb 12, 2019 in Environmental Engineering by Arjun (2.8k points)

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24

GATE2016-2-50
A sample of water has been analyzed for common ions and results are presented in the form of a bar diagram as shown. The non-carbonate hardness (expressed in mg/L as $CaCO_3$) of the sample is $40$ $165$ $195$ $205$

asked Mar 28, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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25

GATE2016-2-51
A noise meter located at a distance of $30 \: m$ from a point source recorded $74 \: dB$. The reading at a distance of $60 \: m$ from the point source would be __________

asked Mar 28, 2018 in Noise Pollution by Milicevic3306 (11.9k points)

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26

GATE2016-2-52
For a wastewater sample, the three-day biochemical oxygen demand at incubation temperature of $20^{\circ}C$ (BOD$_{\text{3day}, 20^{\circ}C}$) is estimated as $200 mg/L$ ... in mg/L) of the wastewater at incubation temperature of $20^{\circ}C$ (BOD$_{\text{5day}, 20^{\circ}C}$) would be ________

asked Mar 28, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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27

GATE2016-1-18
Crown corrosion in a reinforced concrete sewer is caused by: $H_2S$ $CO_2$ $CH_4$ $NH_3$

asked Mar 28, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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28

GATE2016-1-19
It was decided to construct a fabric filter, using bags of $0.45$ m diameter and $7.5$ m long, for removing industrial stack gas containing particulates. The expected rate of airflow into the filter is $10 \: m^3/s$. If the filtering velocity is $2.0$ m/min, the minimum number of bags (rounded to nearest higher integer) required for continuous cleaning operation is $27$ $29$ $31$ $32$

asked Mar 28, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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29

GATE2016-1-20
Match the items in Group - I with those in Group - II and choose the right combination. ... $P - 1; \: Q - 4; \: R - 2; \: S - 3$

asked Mar 28, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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30

GATE2016-1-50
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 ______

asked Mar 28, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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31

GATE2016-1-51
An electrostatic precipitator (ESP) with $5600\:m^2$ of collector plate area is $96$ percent efficient in treating $185\:m^3/s$ of flue gas from a $200$ MW thermal power plant. It was found that in order to achieve $97$ percent efficiency, the collector plate ... $99$ percent, the ESP collector plate area (expressed in $m^2$) would be ______

asked Mar 28, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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32

GATE2016-1-52
The $2$-day and $4$-day BOD values of a sewage sample are $100$ mg/L and $155$ mg/L, respectively. The value of BOD rate constant (expressed in per day) is __________

asked Mar 28, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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33

GATE2017 CE-1: 14
The wastewater from a city, containing a high concentration of biodegradable organics, is being steadily discharged into a flowing river at a location S. If the rate of aeration of the river water is lower than the rate of degradation of the organics, then the ... the location S. remains constant all along the length of the river. is lowest at a point downstream of the location S.

asked Mar 26, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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34

GATE2017 CE-1: 52
The equivalent sound power level (in dB) of the four sources with the noise levels of $60$ dB, $69$ dB, $70$ dB and $79$ dB is ______

asked Mar 26, 2018 in Noise Pollution by Milicevic3306 (11.9k points)

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35

GATE2017 CE-1: 54
Two wastewater streams A and B, having an identical ultimate BOD are getting mixed to form the stream C. The temperature of the stream A is $20^{\circ}C$ and the temperature of the stream C is $10^{\circ}C$. It is given that the $5$-day BOD of the stream A measured ... The $5-$day BOD (in mg\I, up to one decimal place ) of the stream C, calculated at $10^{\circ} C$, is _________

asked Mar 26, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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36

GATE2015-2-21
$SO_2$ and $CO$ adversely affect oxygen carrying capacity of blood and functioning of lungs respectively functioning of the respiratory system and brain respectively functioning of the respiratory system and oxygen carrying capacity of blood respectively functioning of air passages and chest respectively

asked Mar 26, 2018 in Air Pollution by Milicevic3306 (11.9k points)

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37

GATE2015-2-47
A landfill is to be designed to serve a population of $200000$ for a period of $25$ years. The solid waste (SW) generation is $2$ kg/person/day. The density of the un-compacted SW is $100 \: kg/m^3$ and a compaction ratio of $4$ is suggested. The ratio of compacted fill (i.e., SW+cover) to compacted SW is $1.5$. The landfill volume (in $million \: m^3$) required is _________.

asked Mar 26, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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38

GATE2015-2-48
A water treatment plant of capacity, $1 \: m^3/s$ has filter boxed of dimensions $6 \; m \times 10 \: m$. Loading rate to the filters is $120 \: m^3/day/m^2$. When two of the filters are out of service for back washing, the loading rate (in $m^3/day/m^2$) is _________.

asked Mar 26, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)

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39

GATE2015-2-49
Ultimate BOD of a river water sample is $20$ mg/L. BOD rate constant (natural log) is $0.15 \: day^{-1}$. The respective values of BOD (in $\%$) exerted and remaining after $7$ days are: $45$ and $55$ $55$ and $45$ $65$ and $35$ $75$ and $25$

asked Mar 26, 2018 in Environmental Engineering by Milicevic3306 (11.9k points)

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40

GATE2015-2-50
In a wastewater treatment plant, primary sedimentation tank (PST) designed at an overflow rate of $32.5 \: m^3/day/m^2$ is $32.5$ m long, $8.0$ m wide and liquid depth of $2.25$ m. If the length of the weir is $75$ m, the weir loading rate (in $m^3/day/m$) is ______.

asked Mar 26, 2018 in Water and Waste Water by Milicevic3306 (11.9k points)