In this study, dewatered alum sludge cakes were used as substrate in a laboratoryscale tidal vertical flow reed bed system treating animal farm wastewater. The“tidal flow” operation was employed to enhance oxygen transfer into the reed bedsystem, while dewatered alum sludge cake was used to enhance phosphorus (P)removal in the system through ligand exchange. Except for the removal of Pwhich was consistently high throughout the experiment, the removal of organics(BOD5, COD) exhibited a trend of gradual and increasing removal. Thishighlights the obvious advantage of the use of the dewatered alum sludge cake inthe reed bed. For the removal of organics, a mean removal percentage of82.3 ± 3.5 % was obtained for BOD5 at an average loading of 84.6 g/m2.d. Inaddition, the first-order kinetics constant for BOD5 removal (KBOD, m/d) obtainedin the system was about 9 times the rate constant commonly obtained inconventional horizontal flow systems. The mean level of dissolved aluminium(Al) monitored in the effluent was 0.04 ± 0.01 mg/l and this is well below thedischarge limit of 0.2 mg/l for Al discharge into all waters.
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