DFCCIL (Dedicated Freight Corridor Corporation of India Limited) Exam Date 2021 on September and October 2021 so boost your preparation by attempt this Civil Environmental Engineering quiz for DFCCIL recruitment 2021.
Quiz: Civil Engineering
Topic: Environmental Engineering
Each question carries 1 mark
Negative marking: 1/4 mark
Time: 8 Minutes
Q1. The plume behavior which occurs in the super adiabatic condition with light to moderate wind speed in the presence of large scale thermal eddies are known as………..
(a) coning plume
(b) neutral plume
(c) looping plume
(d) fanning plume
Q2. What is the threshold of audibility in decibel?
Q3. The volume (in milliliters) occupied by aerated mixed liquor containing one gram of dry solids after setting for 30 minutes is termed as:
(a) Allowable solids content
(b) Sludge volume index
(c) Liquor index
(d) Chlorination limit
Q4. A grit chamber of dimensions 12.0 m × 1.50 m × 0.80 m liquid depth has flow of 720 m³/hr. Its surface loading rate and detention time are respectively
(a) 4000 m³/hr and 1.2 minute
(b) 40000 Lph/m² and 40 minute
(c) 40 m³/hr/m² and 12 minute
(d) 40000 Lph/m² and 1.2 minute
Q5. The presence of which of the following is a reason for temporary hardness of water?
Q6. Consumption of higher concentration of fluorides exceeding 1.5 mg/L may cause:
(c) Blue baby disease
Sol. Looping plume occurs in super adiabatic condition in which Environmental lapse rate is greater than adiabatic lapse rate.
|Less than 20 Hz
20 HZ to 20,000 Hz
> 20,000 Hz
Sol. Sludge volume index → Sludge volume index is defined as volume occupied in ml. by 1 gm. Of solid in the mix liquor when allow to settle for 30 min.
▭(SVI=(Settled Sludge volume (ml))/(MLSS (gm) ))
Dimension of grit chamber = 12 ×1.5 × 0.8 m³
Rate of flow = 720 m²/hr
Surface loading rate =?
Detention time =?
Surface loading rate = (Discharge\/rate of flow)/(Surface area.)
= 40 m³/hr/m²
= 40000 l/hr/m²
Detention time = (Volume of tank)/(rate of flow)
= (12 ×1.5 ×0.8 ×60)/720 = 1.2 min.
Sol. Hardness of water is due to the presence of multivalent cation.
Major ion → Ca^(+2),Mg^(+2)
Minor ion → Al^(+3),Sr^(+2),Mn^(+2),Fe^(+2)
Sol. It concentration of fluorides in drinking water exceeding 1.5 mg/l, then it may cause fluorosis, decolorization and molting of teeth. It the concentration of fluorides is less than 1 mg/l then it may cause dental cavity.