Question

QUESTION 2 Check whether the following statements are true or wrong. i. The geometric increase method predicts a greater population than the arithmetic increase method. ii. To transport water from a lower elevation to a higher elevation, gravity method can be used. iii. The self-cleansing velocity is to check the deposition in the sewer pipeline. iv. To transport water to a longer distance, pumps should be arranged in parallel. v. Diffusion is the main transport mode of pollutants in a stream. vi. Higher the number of bends in a pipe, the greater the energy supplied by a pump.

Answer 1

Answer (i) TRUE

Explanation:

Arithmetical increase method predicts a lower estimate than the actual population. Thus the Arithmetical increase method is suitable for older cities, whereas a geometrical increase method is suitable for new cities. Geometric increase method predicts a greater population than the aithmetic increase method.

Reference:

"Handbook of Engineering Hydrology: Environmental Hydrology and Water Management".

Answer (ii) WRONG

Explanation:

In gravity method, water flows under the influence of gravity only. Therefore this method can be used to transport water from higher to lower elevation only.

Reference:

"Gravity Flow Water Supply" by Santiago Arnalich

Answer (iii) TRUE

Explanation:

Self cleansing velocity is necessary to reduce the risk of accumulation of deposits.

Reference:

"Urban and Highway Stormwater Pollution: Concepts and Engineering" by Thorkild Hvitved-Jacobsen, Jes Vollertsen, Asbjorn Haaning Nielsen

Answer (iv) WRONG

Explanation:

Pumps can be arranged in parallel to achieve higher flow rate wheras the pumps in series has higher pumping head. Long distance transport of water requires higher pumping head. Thus the best arrangement is series arrangement. Thus the given statement is wrong.

Reference:

"Fluid Mechanics - Fundamentals and applications" by Yunus A Cengel and John M Cimbala