Ms. Humby et Csb. Fitzpatrick, ATTRITION OF GRANULAR FILTER MEDIA DURING BACKWASHING WITH COMBINED AIR AND WATER, Water research, 30(2), 1996, pp. 291-294
Attrition resistance of granular filter media is becoming increasingly
important as materials such as GAC and anthracite are being more freq
uently used as filter media. The purpose of this study was to evaluate
the attrition experienced by various media during backwashing by perf
orming accelerated backwash tests in a pilot column, using a combined
water and air backwash at combinations that gave the condition known a
s collapse-pulsing. Since the dominant mode of attrition was assumed t
o be abrasion, the effluent was sampled at a number of intervals to de
termine the amount of fine material in the effluent. Coal based GAC ex
hibited the highest weight loss (similar to 7%) and sand the least (si
milar to 2%).