Past Year Questions: Quality & Characteristics of Waste Water

Past Year Questions: Quality & Characteristics of Waste Water | Environmental Engineering - Civil Engineering (CE) PDF Download

Q. 1 The ultimate BOD (L0) a wastewater sample is estimated as 87% of COD. The COD of this wastewater is 300 mg/L. Considering first order BOD reaction rate constant k (use natural log) = 0.23 per day and temperature coefficient θ = 1.047, the BOD value (in mg/L, up to one decimal place) after three days of incubation at 2 7 °C for the w astew ater will b e _______    [2018 : 2 Marks, Set-I]
Ans: 160.226 mg/l

Ultimate BOD = 0.87
COD = 0.87 x 300 = 261 mg/l

For municipal sewage, at standard temperature, value of k((base e) = 0.23 per day. Thus, value 0.23 per day given is w.r.t. the standard temperature of 20°C.

= 0.23 (1,047)27-20

= 0.317 days-1
BOD3 = 261 (1 - e-0.317 x 3)
= 160.226 mg/l

Q. 2 For a given water sample, the ratio between BOD5-day, 2o°c and the ultimate BOD is 0.68. The value of the reaction rate constant k (on base e) (in day-1, up to two decimal places ) is [2017 : 2 Marks, Set-II]
Ans: 0.23 day-1

Q. 3: Two wastewater streams A and B, having an indentical ultimate BOD are getting mixed to form the stream C. The temperature of the stream /A is 20°C and the temperature of the stream C is 10°C. It is given that

• the 5-day BOD of the stream A measured at 20°C = 50 mg/l
• BOD rate constant (base 10) at 20°C = 0.115 per day
• temperature coefficient = 1.135

The 5-day BOD (in mg/l, up to one decimal place) of the stream C, calculated at 10°C , is    [2017 : 2 Marks, Set-I]

Ans: 21.21mg/l

For stream A,

For stream C,

Q. 4 For a wastewater sample, the three-day biochemical oxygen demand at incubation temperature of  is estimated as 200 mg/l. Taking the value of the first order BOD reaction rate constant as 0.22 day-1, the five-day BOD (expressed in mg/l) of the wastewater at incubation temperature of  would be______ .     [2016 : 2 Marks, Set-Il]
Ans: 276.19 mg/l

From equation (i) and (ii), we get,

Q. 5 : 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________ .   [2016 : 2 Marks, Set-I]
Ans: 0.299

1.55 - 1,55x = 1 - x2
x2 - 1.55x + 0.55= 0

Q. 6: 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:    [2015 : 2 Marks, Set-II]
(a) 45 and 55
(b) 55 and 45
(c) 65 and 35
(d) 75 and 25
Ans: (c)

BOD remaining after 7 days

The document Past Year Questions: Quality & Characteristics of Waste Water | Environmental Engineering - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Environmental Engineering.
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Environmental Engineering

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FAQs on Past Year Questions: Quality & Characteristics of Waste Water - Environmental Engineering - Civil Engineering (CE)

 1. What is wastewater and why is it important to study its quality and characteristics?
Ans. Wastewater refers to the water that has been used and discarded as a result of various human activities. It includes water from households, industries, and commercial establishments. Studying the quality and characteristics of wastewater is crucial as it helps in understanding its potential environmental and health impacts. It also aids in designing effective treatment processes to ensure the safe disposal or reuse of wastewater.
 2. What are the main sources of wastewater?
Ans. Wastewater can originate from various sources such as households, industries, commercial establishments, and agricultural activities. Domestic wastewater, which is generated from households, is one of the primary sources. Industrial wastewater is produced by industrial processes and can contain various pollutants specific to the industry. Commercial establishments like restaurants and hotels also contribute to wastewater generation through their activities such as food preparation, washing, and cleaning.
 3. What are the key characteristics of wastewater?
Ans. Wastewater exhibits several characteristics that determine its quality and treatment requirements. Some of the key characteristics include physical parameters like color, turbidity, and temperature. Chemical parameters such as pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and nutrient content are also important. Additionally, biological characteristics like the presence of pathogens and toxicity levels are crucial in assessing the potential harm of wastewater to the environment and public health.
 4. How does the quality of wastewater impact the environment and human health?
Ans. The quality of wastewater can have significant impacts on the environment and human health. If wastewater is discharged without proper treatment, it can contaminate water bodies, leading to the depletion of oxygen levels and the death of aquatic organisms. The presence of harmful chemicals and pathogens in untreated wastewater can pose health risks to humans through direct contact or consumption of contaminated water and food. Therefore, understanding and managing the quality of wastewater is essential to prevent environmental degradation and protect public health.
 5. What are the methods used to treat wastewater and improve its quality?
Ans. There are various methods employed to treat wastewater and improve its quality before disposal or reuse. Common treatment processes include physical methods like sedimentation, filtration, and disinfection. Chemical methods such as coagulation, flocculation, and advanced oxidation processes are also used. Biological treatment methods like activated sludge process and constructed wetlands are effective in removing organic pollutants. Additionally, technologies like reverse osmosis and ultraviolet disinfection are utilized to further enhance the quality of treated wastewater.

Environmental Engineering

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