Dg. Hemmings et Csb. Fitzpatrick, PRESSURE SIGNAL ANALYSIS OF COMBINED WATER AND AIR BACKWASH OF RAPID GRAVITY FILTERS, Water research, 31(2), 1997, pp. 356-361
Many problems encountered in water filtration are associated with the
effectiveness of backwashing. Combined air and water backwashing espec
ially using flow rate combinations resulting in ''collapse-pulsing'' p
rovide the most effective cleaning. This study examines a technique of
analysing pressure signal fluctuations in order to determine the onse
t of ''collapse-pulsing''. The technique provides a non-subjective and
practical method of ''collapse-pulsing'' determination. The resultant
pressure fluctuation traces are examined in combination with headless
versus water velocity profiles at particular set air flow rates. The
occurrence of significant fluctuation patterns at the position where h
eadless becomes constant implies that ''collapse-pulsing'' determined
by this technique is the onset of three phase fluidisation. Copyright
(C) 1996 Elsevier Science Ltd.