Low-frequency sonication-assisted coagulation of eutrophic lake water using Moringa oleifera seed extract and polyaluminum chloride

This study evaluated 40-kHz probe sonication before coagulation of real eutrophic lake water (15.5 NTU; chlorophyll a , 22 µg L −1 ) using Moringa oleifera (MO) seed extract or polyaluminum chloride (PACl) in separate experimental series. MO-based screening selected an acoustic power of 28 W for 30 s. At 1.0 mL L −1 MO, sonication increased turbidity removal from 61.40% to 73.02% and chlorophyll a removal from 73.33% to 85.01%. Within the PACl series, at 0.5 mg Al L −1 , the corresponding removals increased from 42.69% to 53.91% and from 77.89% to 85.70%. Higher removal was also observed at early sedimentation times. DOC did not increase significantly immediately after sonication at 28 W for 30 s, but increased at 42 W and exposure times of at least 60 s. Post-MO coagulation DOC remained approximately 13–14 mg L −1 . Zeta potential became less negative, indicating an altered electrokinetic response of the bulk suspension rather than a cell-specific mechanism. The selected treatment required 0.63 kWh m −3 of electrical energy at laboratory scale. These findings identify within-system sonication benefits alongside organic-carbon and energy limitations, without establishing the relative superiority of MO or PACl.