Two strategies for improving animal farm wastewater treatment in reed beds

In this study, dewatered alum sludge cakes were used as substrate in a laboratory scale tidal vertical flow reed bed system treating animal farm wastewater. The “tidal flow” operation was employed to enhance oxygen transfer into the reed bed system, while dewatered alum sludge cake was used to enhance phosphorus (P) removal in the system through ligand exchange. Except for the removal of P which was consistently high throughout the experiment, the removal of organics (BOD5, COD) exhibited a trend of gradual and increasing removal. This highlights the obvious advantage of the use of the dewatered alum sludge cake in the reed bed. For the removal of organics, a mean removal percentage of 82.3 ± 3.5 % was obtained for BOD5 at an average loading of 84.6 g/m2.d. In addition, the first-order kinetics constant for BOD5 removal (KBOD, m/d) obtained in the system was about 9 times the rate constant commonly obtained in conventional 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 the discharge limit of 0.2 mg/l for Al discharge into all waters.