Past Year Questions: Disposal of Sewage Effluents

Past Year Questions: Disposal of Sewage Effluents | Environmental Engineering - Civil Engineering (CE) PDF Download

Q. 1 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 dissolved oxygen of the river water.    [2017 : 1 Mark, Set-I]
(a) is lowest at the location S.
(b) is lowest at a point upstream of the location S.
(c) remains constant all along the length of the river.
(d) is lowest at a point downstream of the location S.

Ans: (d)

• Before point T, rate of aeration < rate of degradation, so DO continuously decrease from S till T.
• At point T, rate of aeration = Rate of degradation. Flence DO is minimum at T,
• After T, rate of aeration > Rate of degradation, so DO starts increasing.

Hence, DO is minimum at some point downstream of S.

Q. 2  A waste water stream (flow = 2 m3/s, ultimate BOD = 90 mg/l) is joining a small river (flow = 12m3/s, ultimate BOD = 5 mg/I). Both water streams get mixed up instantaneously. Cross- sectional area of the river is 50 m2. Assuming the de-oxygenation rate constant, K = 0.25/day, the BOD (in mg/l) of the river water, 10 km downstream of the mixing point is   [2014 : 2 Marks, Set-Il]
(a) 1.68
(b) 12.63
(c) 15.46
(d) 1.37
Ans:
(c)

Flow of waste water stream, Qw= 2 m3/sec
Ultimate BOD,
Yw = 90 mg/l = 90 gm/m3
Flow of river, Qr = 12 m3/sec
Ultimate BOD of river,
Yr = 0.5 mg/l = 5 gm/m3

BOD of mixture,

Area of river = 50 m2
Flow of river =12 m3/sec

The document Past Year Questions: Disposal of Sewage Effluents | Environmental Engineering - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Environmental Engineering.
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FAQs on Past Year Questions: Disposal of Sewage Effluents - Environmental Engineering - Civil Engineering (CE)

 1. What is sewage effluent?
Ans. Sewage effluent refers to the liquid waste that is discharged from domestic, commercial, or industrial sources into the sewage system.
 2. How is sewage effluent disposed of?
Ans. Sewage effluent is typically treated at wastewater treatment plants before being released into the environment. The treatment process involves removing solids, reducing organic matter and nutrients, and disinfecting the effluent to make it safe for disposal.
 3. What are the potential environmental impacts of improper disposal of sewage effluents?
Ans. Improper disposal of sewage effluents can lead to water pollution, contamination of aquatic ecosystems, and the spread of waterborne diseases. It can also harm marine life and degrade the quality of drinking water sources.
 4. What are the common methods of sewage effluent disposal?
Ans. Common methods of sewage effluent disposal include discharging the treated effluent into rivers, lakes, or the ocean, utilizing it for irrigation purposes, or reusing it for non-potable uses such as toilet flushing or industrial processes.
 5. Are there any regulations or guidelines in place for the disposal of sewage effluents?
Ans. Yes, most countries have regulations and guidelines that govern the disposal of sewage effluents. These regulations aim to protect the environment and public health by setting standards for the treatment and disposal of wastewater. Compliance with these regulations is typically enforced by environmental agencies or local authorities.

Environmental Engineering

14 videos|99 docs|98 tests

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