List of top Environmental Engineering Questions asked in GATE CE

MgCl$_2$ and CaSO$_4$ salts are added to 1 litre of distilled deionized water and mixed until completely dissolved. Total Dissolved Solids (TDS) concentration is 500 mg/l, and Total Hardness (TH) is 400 mg/l (as CaCO$_3$). The amounts of MgCl$_2$ and CaSO$_4$ added are calculated (rounded off to the nearest integer). Which of the following options is/are true:
Aeration is employed as a treatment option for the removal of several pollutants from contaminated water. Identify the pollutant(s), where aeration is employed as part of their removal:
In the context of testing bitumen, which one of the following statements is FALSE:
Fecal Coliform (FC) concentration in river water was measured as 10708 cfu/100 ml. The FC concentration after the conventional water treatment, but before chlorination, was measured as 23 cfu/100 ml. The 'Log Kill' (inactivation) of FC due to the conventional water treatment is closest to:
A facultative pond system is employed for wastewater treatment. Which of the following statements is/are true:
The Surface Overflow Rate (SOR) in a rectangular sedimentation tank is 45 m\(^3\)/m\(^2\)·day. Minimum diameters of spherical inorganic and organic particles expected to be completely removed in this tank are calculated. Assume that Stoke’s law is applicable. Which of the following options is/are correct:
The analyses results of a water sample are given below. The non-carbonate hardness of the water (in mg/L) as CaCO\(_3\) is ......... (in integer).
Ca\(^{2+}\) = 150 mg/L as CaCO\(_3\)
Mg\(^{2+}\) = 40 mg/L as CaCO\(_3\)
Fe\(^{2+}\) = 10 mg/L as CaCO\(_3\)
Na\(^+\) = 50 mg/L as CaCO\(_3\)
K\(^+\) = 10 mg/L as CaCO\(_3\)
CO\(_3^{2-}\) = 120 mg/L as CaCO\(_3\)
HCO\(_3^{-}\) = 30 mg/L as CaCO\(_3\)
Cl\(^{-}\) = 50 mg/L as CaCO\(_3\); Other anions were not analysed.

The bank of a canal has the profile shown in the figure. The material is a homogeneous clay with a bulk unit weight of 20 kN/m\(^3\), undrained cohesion of 30 kPa and is fully saturated (\( \phi = 0 \)). For the trial slip circle shown, the area ABCDEA is 150 m\(^2\) and the centroid is at P. A tension crack (DE) of 2.5 m deep was also observed. Assume unit weight of water is 9.81 kN/m\(^3\) and consider 1 m run of the bank for the analysis. 
Considering the canal is empty and the tension crack is completely filled with water, the factor of safety against slope failure of the bank is ......... (round off to two decimal places). 

Identify the treatment technology/technologies NOT recommended for highly biodegradable organic solid wastes.
 

The point where the road alignment changes from a tangent to a curve is known as ___________.
 

A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is 250 m\(^3\), and the biomass concentration in the tank is 3000 mg/L. Analyses results showed that a biomass concentration of 10 mg/L is present in the treated effluent from the secondary sedimentation tank of the ASP. Sludge wastage from the system is at a rate of 5000 L/day with a biomass concentration of 10000 mg/L. The system is in steady state condition.
The biological sludge residence time (BSRT) of the system (in days) is ......... (round off to one decimal place).
A water treatment plant treats 25 MLD water with a natural alkalinity of 4.0 mg/L (as CaCO3). It is estimated that, during coagulation of this water, 450 kg/day of calcium bicarbonate (Ca(HCO3)2) is required based on the alum dosage.
Consider the atomic weights as: Ca-40, H-1, C-12, O-16.
The quantity of pure quick lime, CaO (in kg) required for this process per day is _____ (rounded off to 2 decimal places).
An organic waste is represented as C240O200H180N5S.
(Atomic weights: S-32, H-1, C-12, O-16, N-14).
Assume complete conversion of S to SO2 while burning.
SO2 generated (in grams) per kg of this waste is _______ (rounded off to 1 decimal place).
A circular settling tank is to be designed for primary treatment of sewage at a flow rate of 10 million liters/day. Assume a detention period of 2.0 hours and surface loading rate of 40000 liters/m2/day. The height (in meters) of the water column in the tank is __________ (rounded off to 2 decimal places).
Which one of the following products is NOT obtained in anaerobic decomposition of glucose ?
Activated carbon is used to remove a pollutant from wastewater in a mixed batch reactor, which follows first-order reaction kinetics.
At a reaction rate of 0.38 /day, the time (in days) required to remove the pollutant by 95% is ______ (rounded off to 1 decimal place).
The primary air pollutant(s) is/are
The following table gives various components of Municipal Solid Waste (MSW) and a list of treatment/separation techniques.
Component of MSWTreatment/separation technique
P - Ferrous metalsi - Incineration
Q - Aluminum and copperii - Rapid composting
R- Food wasteiii - Eddy current separator
S-Cardboardiv - Magnetic separator

The CORRECT match is 
The number of degrees of freedom for a natural open channel flow with a mobile bed is
A system of seven river segments is shown. Given: $Q_1=5$ m$^3$/s, $Q_2=15$ m$^3$/s, $Q_4=3$ m$^3$/s (outflow), $Q_6=8$ m$^3$/s; $C_1=8$ kg/m$^3$, $C_2=12$ kg/m$^3$, $C_6=10$ kg/m$^3$. Assume complete mixing at junctions, no gains/losses otherwise, steady state. Find the pollutant concentration in segment $R_7$ (in kg/m$^3$, rounded to two decimals). \includegraphics[width=0.5\linewidth]{image555.png}
The theoretical aerobic oxidation of biomass (C$_5$H$_7$O$_2$N) is:
\[ \mathrm{C_5H_7O_2N + 5\,O_2 \rightarrow 5\,CO_2 + NH_3 + 2\,H_2O} \] Given a first-order biochemical oxidation with $k=0.23\ \text{d^{-1}$ at $20^{\circ}$C (base $e$) and neglecting the second-stage oxygen demand, find the ratio BOD$_5$ at $20^{\circ}$C to TOC (round to two decimals).}
Atomic weights: C=12, H=1, O=16, N=14 g/mol
Which of the following statements is/are TRUE for the aerobic composting of sewage sludge?
In the context of water and wastewater treatments, the correct statements are:
Match the following air pollutants with the most appropriate adverse health effects: \includegraphics[width=0.75\linewidth]{image44.png}
For the elevation and temperature data given in the table, the existing lapse rate in the environment is \underline{\hspace{2cm} °C/100 m (round off to two decimal places).} \includegraphics[width=0.75\linewidth]{image35.png}