The use of Moringa oleifera as a natural coagulant in surface water treatment

•Moringa oleifera (MO) as natural coagulant for cyanobacteria removal from water.•MO oil-extraction is not necessary when using MO seeds as a coagulant in C/F/S.•High-turbidity waters doesn't need the extraction of the MO seeds.•Low-turbidity waters, MO extracted with NaCl (1 M) presented the best removals.•Aromatic organic matter was partially removed by MO extracted with NaCl (1 M).

Moringa oleifera (MO) seed is a natural plant with active bio-coagulate compounds that can be used for water clarification since it reduces the use of chemical-based coagulants. This study aims to evaluate the impact of Moringa oleifera (MO) seeds and MO seeds with a reduced amount of oil as coagulants in conventional water treatment to remove cyanobacteria from different natural surface waters. Tests were performed for waters with low (5-10 NTU) and high (30-60 NTU) initial turbidity with and without Microcystis aeruginosa cells and for MO integral powder, MO oil-extracted with ethanol and with a pressurized technique, and MO extracted with NaCl. The results show that MO oil-extraction is not necessary when using MO seeds as a coagulant in coagulation/flocculation/sedimentation (CF/S). Chlorophyll a and turbidity removals were up to 85% for high-turbidity waters, with 50 mg·L−1 MO obtained, for MO integral powder and for all of the MO extraction methods used. Therefore, for these waters, integral powder (without any extraction) can be used. For low-turbidity waters and using a 1 M saline extraction of the active coagulant compound, chlorophyll a and turbidity removals were approximately 60%. It was also demonstrated that MO is capable of removing some of the organic matter present in water, namely, aromatic organic matter, between 40 and 50% when using MO extracted with NaCl. However, dissolved organic matter results showed an increase independent of the type of MO extraction used.