ABSTRACT

A filter backwash rate is a measurc of the gprn flowing upward through each sq ft of filter surface area The calculation of backwash rate is similar to filtration rate.

Backwash = mow, gpm Rate Area, sq ft

Example 1: (Backwash Rate) D A filter with a surface area of 150 sq ft has a backwash flow rate of 2900 gpm. What is the filter backwash rate in

(10 ft) (15 ft)

2900 gpm 150 sq ft

(25 ft) (10 ft)

Backwash = Flow, gpm Rate Area, sq ft

(25 ft) (10 ft)

Example 3: (Backwash Rate) O A filter 15 ft by 15 ft has a backwash flow rate of 3150 gpm. What is the filter backwash rate in gpm/sq ft?