Abstract
Microalgae are microscopic organisms that are commonly found in freshwater. Freshwater surfaces with excessive microalgae will result in unpleasant surface scum, severe oxygen depletion, and fish die-offs. One of the usually employed techniques to remove microalgae is through chitosan powder; in this approach, the cationic chitosan molecules are used to flocculate the anionic microalgae. However, this technique has the potential to generate sludge and requires considerable quantities of flocculant. To avoid such limitations, chitosan macrobeads were proposed in this study. This study aimed to compare the microalgae removal efficiency via flocculation (using chitosan powder) and adsorption (using chitosan macrobead). The removal experiment was conducted using microalgae from similar local pond water. Results showed that both methods are effective in removing wild microalgae. In particular, 60 %, 44 %, and 54 % of microalgae were removed by 2 g of chitosan powder at pH 2, pH 7, and pH 10. On the other hand, 2 g chitosan macrobeads removed 99 %, 91 %, and 95 % of microalgae at pH 2, pH 7, and pH 10. Such observation implies that the use of chitosan macrobeads for microalgae adsorption is less affected by pH. The isolation of spent chitosan macrobead amicrobial was done as there was no sludge formation. More importantly, the chitosan macrobead succusses removed almost all of the microalgae from the pond water within 24 h regardless of the medium pH, leaving a clear solution. Microscopic studies further verified the attachment of microalgae (in cluster form) on the chitosan macrobead. With the encouraging results, future study is suggested to further optimize the microalgae removal efficiency by modifying the surface pore structure of the chitosan macrobead.
