JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III ENVIRONMENTAL ENGINEERING Previous Question Paper (September - 2021 - R16)

The estimation of water demand is based on several key factors: domestic water consumption (based on population and living standards), industrial demand (based on the type and size of industries), commercial and institutional demand, public utility demand (for parks, street washing, and fire fighting), and compensation for losses and waste (leakage and theft). Population forecasting methods, such as the Arithmetic Increase, Geometric Increase, or Incremental Increase methods, are used to project future demand over the design period.

For fire fighting, the demand is calculated using empirical formulas such as the Kuichling's formula, Freeman's formula, or the National Board of Fire Underwriters formula, which relate the required discharge to the population. To ensure effective fire fighting, measures include: maintaining a residual pressure in the distribution system (typically 7 to 10 meters of head), providing dedicated fire hydrants at strategic intervals, ensuring the availability of independent fire storage tanks or reservoirs, and designing the distribution pipe network to handle the high-velocity, high-pressure flow required during emergencies.

When these substances exceed permissible limits, they cause the following health and aesthetic effects:

• Nitrates: Excess concentration (typically above 45 mg/L) causes methemoglobinemia, also known as 'blue baby syndrome,' in infants, where the blood's oxygen-carrying capacity is reduced.
• Chlorides: High levels impart a salty taste to water, cause corrosion of metallic pipes and structures, and may have a laxative effect on individuals unaccustomed to high mineral content.
• Sulphates: Concentrations exceeding 250 mg/L can cause a laxative effect on human systems and contribute to the formation of hard scale in boilers and pipes.
• Fluorides: Low concentrations (below 0.5 mg/L) lead to dental caries, while concentrations exceeding 1.5 mg/L cause dental fluorosis (mottling of teeth) and, at higher levels, skeletal fluorosis, which affects bone structure.
• Iron: Excess iron causes reddish-brown staining of laundry and plumbing fixtures, imparts a bitter or metallic taste, and promotes the growth of iron bacteria, which can clog distribution systems.