DEVELOPMENT OF A FRIABILITY TEST FOR GRANULAR FILTER MEDIA

At present there is no generally accepted test available for character izing the friability of granular filter media in the context of its ab ility to withstand handling and placing, as distinct from abrasion res istance during backwashing - which is the subject of other, existing, test methods. Most existing procedures tend to be grinding tests and h ave little meaning. The approach selected in this work was to adapt th e ring shear test, in which a sample (large enough to be analysed by s ieving) is subjected to shear under a known compression load and the c hange in the undersize fraction is assessed. A representative selectio n of dry media was submitted to the test and the results proved to be reproducible and capable of distinguishing (clearly) between friable a nd non-friable resistant types. The procedure is likely to become the basis of a standard test.