(SEM VI) THEORY EXAMINATION 2022-23 ENVIRONMENTAL ENGINEERING

ENVIRONMENTAL ENGINEERING (KCE-603)

Important Questions & Answers – Section-wise

SECTION A

(Attempt all questions – 2 × 10 = 20 marks)

(a) What is a spigot and socket joint?

A spigot and socket joint is a type of pipe joint commonly used in water supply and sewer pipes. One end of the pipe is called the spigot (plain end) and the other end is the socket (expanded end). The spigot fits into the socket and the joint is sealed using lead, rubber ring, or cement mortar to prevent leakage.

(b) Define reflux and relief valves

A reflux valve is a non-return valve used to prevent backward flow of water in pipelines. A relief valve is a safety valve used to release excess pressure from the pipeline to avoid damage or bursting.

(c) What is coincident draft?

Coincident draft is the condition when the maximum demand for water occurs simultaneously throughout the entire distribution system. It represents the worst demand condition for which the system must be designed.

(d) Write Hazen-Williams formula with usual notations

The Hazen-Williams formula is used to calculate head loss due to friction in water pipes:

hf=10.67×LQ1.852C1.852D4.87h_f = 10.67 \times \frac{L Q^{1.852}}{C^{1.852} D^{4.87}}hf​=10.67×C1.852D4.87LQ1.852​

Where
hfh_fhf​ = head loss (m)
LLL = length of pipe (m)
QQQ = discharge (m³/s)
CCC = Hazen-Williams coefficient
DDD = diameter of pipe (m)

(e) What is Theoretical Oxygen Demand (ThOD)?

Theoretical Oxygen Demand is the amount of oxygen required to completely oxidize the organic matter present in wastewater into carbon dioxide, water, and ammonia, assuming complete oxidation.

(f) How will you measure turbidity of river water?

Turbidity of river water is measured using a nephelometer. The instrument measures the intensity of light scattered by suspended particles in water and expresses turbidity in NTU (Nephelometric Turbidity Units).

(g) What are various forms of chlorine?

Chlorine is used in water treatment in different forms such as chlorine gas, bleaching powder, sodium hypochlorite, calcium hypochlorite, and chloramines.

(h) Forms of nitrogen present in sewage water

Nitrogen in sewage exists in organic nitrogen, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen forms.

(i) Role of algae in aerobic pond

Algae supply oxygen through photosynthesis, which supports aerobic bacteria in oxidizing organic matter. Thus, algae play an important role in maintaining oxygen balance in aerobic ponds.

(j) Difference between attached growth and suspended growth system

In attached growth systems, microorganisms grow attached to a solid medium, whereas in suspended growth systems, microorganisms remain freely suspended in wastewater.

SECTION B

(Attempt any THREE – 10 × 3 = 30 marks)

Q2(a) Factors affecting water demand

Water demand depends on factors such as population size, climate, habits of people, industrial and commercial activities, quality of water, pressure in supply system, and losses due to leakage and wastage.

Q2(b) Storage vs Service reservoirs and unit operations

Storage reservoirs store water for long durations and regulate seasonal variations, while service reservoirs store treated water for daily demand fluctuations. Unit operations include screening, sedimentation, filtration, and disinfection.

Q2(c) Numerical on BOD

(i) Using BOD reaction equation, the 20-day BOD at 20°C is calculated considering ultimate BOD and rate constant.

(ii) Temperature correction is applied using:

kT=k20(1.047)(T−20)k_T = k_{20} (1.047)^{(T-20)}kT​=k20​(1.047)(T−20)

Then BOD₈ is calculated accordingly.

(Step-wise calculation recommended in exam)

Q2(d) Soda lime vs Ion exchange process

Soda lime process is economical and suitable for large water quantities but produces sludge. Ion exchange gives high-quality soft water but is costly and requires regeneration.

Q2(e) Design of grit chamber

A grit chamber removes heavy inorganic particles. Design is based on sewage flow, detention time, velocity, and settling velocity. A schematic diagram is drawn showing inlet, outlet, and grit collection zone.

SECTION C

(Attempt ONE part from each question)

Q3(a) Logistic curve population forecasting

Using population data for two equal time intervals, saturation population is calculated using logistic equation. Coefficients are determined, and future population is predicted mathematically.

Q3(b) Gravity and pressure conduits

Gravity conduits carry water under gravity flow, while pressure conduits carry water under pressure. Pressure conduits are preferred for long-distance water conveyance due to flexibility in terrain.

Q4(a) Layouts of distribution system

Distribution systems include dead-end, grid iron, circular, and radial systems. Grid iron and radial systems are preferred due to better pressure and reliability.

Q4(b) Distribution reservoirs

Distribution reservoirs store treated water near consumption areas. Storage capacity is calculated using mass curve method considering 24-hour pumping.

Q5(a) Carbonaceous BOD

Carbonaceous BOD is oxygen demand due to oxidation of carbon compounds. Nitrogenous oxygen demand is inhibited by adding nitrification inhibitors during BOD test.

Q5(b) MPN of coliforms

Using standard MPN tables for 4-2-1 combination, MPN index = 32 per 100 ml.

Q6(a) Disinfection methods and break point chlorination

Disinfection methods include chlorination, ozonation, UV treatment, and boiling. Breakpoint chlorination is the point where chlorine demand is satisfied and free residual chlorine appears.

Q6(b) Design of sedimentation tank

Settling velocity is calculated using Stoke’s law. Tank dimensions are determined based on overflow rate and flow capacity.

Q7(a) Sludge digestion

Sludge digestion stabilizes organic matter using anaerobic bacteria. Types include anaerobic and aerobic digestion. Disposal methods include land application, incineration, and landfill.

Q7(b) Working of UASB reactor

UASB reactor treats wastewater using anaerobic bacteria in sludge blanket. Biogas is produced and collected, making the process energy-efficient.