Effect of Fineness of Sand on Bacterial Efficiency

Introduction:
The fineness of sand refers to the particle size distribution of the sand particles. It is determined by the percentage of sand particles of different sizes present in a given sample. The fineness of sand is an important factor in various applications, including water filtration systems. In this context, the effect of the fineness of sand on bacterial efficiency and filtration rate is of particular interest.

Effect on Bacterial Efficiency:
The bacterial efficiency refers to the ability of sand to remove bacteria and other microorganisms from water during the filtration process. The finer the sand particles, the higher the bacterial efficiency. This can be attributed to the increased surface area of finer particles, which provides more opportunities for bacterial attachment and removal. Additionally, the smaller pore spaces between fine sand particles enhance the mechanical trapping of bacteria, preventing their passage through the filtration media.

Effect on Filtration Rate:
Contrary to what might be expected, the rate of filtration does not increase with an increase in the fineness of sand. In fact, the rate of filtration initially decreases and then stabilizes as the sand becomes finer. This is due to the fact that finer sand particles have smaller pore spaces, resulting in slower flow rates of water through the filter bed. The reduced porosity and increased tortuosity of the flow path within the finer sand particles lead to a decrease in the overall filtration rate.

Explanation:
The correct answer to the given question is option 'A' - The bacterial efficiency increases. As discussed earlier, the finer sand particles have a greater surface area and smaller pore spaces, which enhance the attachment and mechanical trapping of bacteria during filtration. Therefore, the bacterial efficiency increases with an increase in the fineness of sand.

Conclusion:
In summary, the fineness of sand has a significant impact on the bacterial efficiency and filtration rate. While the bacterial efficiency increases with finer sand particles, the filtration rate initially decreases and then stabilizes. It is important to consider these factors while designing and operating water filtration systems to ensure effective removal of bacteria and other microorganisms from water sources.