Answer to Question #248580 in Civil and Environmental Engineering for anmol

Question

Each filter is washed for 5 minutes every 24 hours at a wash rate of 10 mm/sec/m2 of filter area. The filter remains out of operation for a total interval of 30 minutes per day. Calculate the percentage of filter output used for washing. 

Answer 1

An empirical relationship has been developed to express bed expansion of graded media in terms of temperature (Tebbutt, 1984) which is the ratio of expansions at T °C and 20°C, this is 1.57 e^−0.02255T:1.

Applying this equation to the UK conditions it can be shown that if summer wash rates are used throughout the year, a 40% increase in the degree of expansion is shown in the winter. This would lead to wastage of water and could result in loss of sand. Therefore, in temperate climates, means for seasonal adjustment of wash rates is advisable.

So,

For the 30 minutes per day the percentage will be 37% for the wash rate$10mm/sec/m^2$