Jawaharlal Nehru Technological University Hyderabad B.Tech III ENVIRONMENTAL ENGINEERING Previous Question Paper (February - 2022 - R16)

An infiltration gallery is a horizontal tunnel constructed through water-bearing strata to collect groundwater. They are typically used in areas with high water tables or near riverbanks to tap into sub-surface flow.

Types of infiltration galleries include:

• Horizontal galleries: These are tunnels constructed along the bank of a river or in an aquifer, often lined with masonry or concrete with open joints to allow water infiltration.
• Radial collectors: These consist of a central shaft from which perforated pipes are pushed radially into the surrounding water-bearing formation.

Advantages include:

• They provide a continuous supply of water even during dry seasons.
• The water collected undergoes natural filtration through the soil, resulting in lower turbidity and bacterial contamination compared to surface water.
• They have a long service life and require minimal maintenance compared to mechanical pumping systems.
• They are highly effective in alluvial deposits where the aquifer is shallow and extensive.

Fire demand is the volume of water required to be available in a distribution system to extinguish potential fires. It is critical for public safety, as failure to provide adequate pressure and volume during a fire can lead to catastrophic loss of life and property.

The importance of fire demand lies in its role as a safety buffer. It is not a daily consumption requirement but a peak demand capacity that must be maintained in addition to normal domestic, industrial, and commercial needs.

Calculation of fire demand is typically performed using empirical formulas based on the population of the city (P in thousands). Common formulas include:

• Kuichling's Formula: Q = 3182 * sqrt(P)
• Freeman's Formula: Q = 1136 * (P/5 + 10)
• National Board of Fire Underwriters Formula: Q = 4637 * sqrt(P) * (1 - 0.01 * sqrt(P))

In these formulas, Q represents the discharge in liters per minute. The design must ensure that the distribution system can provide this flow at a residual pressure of at least 7 to 10 meters of water head.