Jawaharlal Nehru Technological University Hyderabad B.Tech III ENVIRONMENTAL ENGINEERING Previous Question Paper (March - 2021 - R16)

To estimate the population for 2021 and 2025, we use the following four standard methods: Arithmetic Increase, Geometric Increase, Incremental Increase, and Simple Graphical Extension.

1. Arithmetic Increase Method

The average increase per decade (x̄) is calculated as: (90-76 + 115-90 + 150-115 + 187-150 + 225-187) / 5 = 149,000 / 5 = 29,800. Population in 2021 (n=1): 225,000 + 1(29,800) = 254,800. Population in 2025 (n=1.4): 225,000 + 1.4(29,800) = 266,720.

2. Geometric Increase Method

The average percentage growth rate (r) is calculated using the geometric mean of growth rates: r = [(18.42 * 27.78 * 30.43 * 24.67 * 20.32)^(1/5)] = 24.15%. Population in 2021 (n=1): 225,000 * (1 + 0.2415)^1 = 279,338. Population in 2025 (n=1.4): 225,000 * (1 + 0.2415)^1.4 = 292,865.

3. Incremental Increase Method

The average incremental increase (ȳ) is: (11+10+2+13) / 4 = 9,000. Population in 2021 (n=1): 225,000 + 1(29,800) + [1(2)/2]*9,000 = 263,700. Population in 2025 (n=1.4): 225,000 + 1.4(29,800) + [1.4(2.4)/2]*9,000 = 281,852.

4. Simple Graphical Extension Method

By plotting the population vs. year on a graph and extending the smooth curve formed by the data points to the years 2021 and 2025, the estimated populations are approximately 260,000 and 275,000 respectively.

Drinking water quality standards, such as those defined by the BIS (IS 10500:2012) or WHO, ensure water is safe for human consumption by setting permissible and rejection limits for various parameters.

Physical Characteristics: These relate to the aesthetic quality of water. Key parameters include:

• Turbidity: Measured in NTU, it indicates suspended matter. The desirable limit is 1 NTU, with a maximum permissible limit of 5 NTU.
• Color: Measured in Hazen units; it should ideally be 5, with 15 as the limit.
• Taste and Odor: Water should be unobjectionable to the consumer.
• Temperature: Ideally 10-15°C for palatability.

Chemical Characteristics: These determine the health effects and suitability for domestic use:

• pH: Should be between 6.5 and 8.5.
• Total Dissolved Solids (TDS): Desirable limit is 500 mg/L; up to 2000 mg/L is permitted if no alternative source exists.
• Hardness: Measured as CaCO3, the desirable limit is 200 mg/L, with 600 mg/L as the limit for rejection.
• Chlorides and Sulfates: Generally limited to 250 mg/L to prevent taste issues and laxative effects.
• Fluoride: Critical for dental health; the range is 1.0 to 1.5 mg/L. Excess causes fluorosis.
• Toxic Metals: Elements like Lead (0.01 mg/L), Arsenic (0.01 mg/L), and Mercury (0.001 mg/L) have stringent limits due to toxicity.

Bacteriological Characteristics: These are the most critical for public health. The standard requires that water be free from pathogenic microorganisms.

• Coliform Organisms: The primary indicator is the absence of E. coli or thermotolerant coliform bacteria in any 100 mL sample.
• MPN Test: The Most Probable Number (MPN) of coliforms should be zero per 100 mL of water entering the distribution system.

Radiological Characteristics: These ensure water does not contain harmful levels of radioactive substances.

• Alpha and Beta Activity: Limits are set based on Becquerels per liter (Bq/L). For gross alpha activity, the limit is typically 0.1 Bq/L, and for gross beta activity, it is 1.0 Bq/L. Exceeding these requires further screening for specific radionuclides like Radium or Uranium.