Evaluation of the potentiality of Vicia faba and Opuntia ficus indica as eco-friendly coagulants to mitigate Microcystis aeruginosa blooms

This study aims to explore the potentiality of Vicia faba seeds and Opuntia ficus indica cladodes, as eco-friendly coagulants, to sanitize water from Microcystis aeruginosa blooms. The effect of factors influencing coagulation-flocculation activity were studied, namely, coagulant dose (5-20 mg/L), pH (5-8), rapid-mixing speed (100-250 rpm) and slow-mixing (presence or absence). Levels used for each factor, were studied by using the experimental research methodology. The efficiency of the studied natural coagulants was compared to that of chemical coagulants (aluminum sulfate and ferric chloride). The assays were conducted using the standard jar test method. Indeed, turbidity, optical density, chlorophyll a and carotenoids reductions were maximal (more than 85%) with 5 and 10 mg/L doses, under the presence of slow-mixing speed of 40 rpm and rapid-mixing speed of 200 rpm. The favorable pH to perform the treatment was confirmed at pH 5. The analysis of extracts by chemical assays and Fourier-transform infrared spectral analysis, confirmed the presence of total sugar, phenols, proteins, and flavonoids groups, which are known by their coagulating potential. Results demonstrated that these two natural coagulants could be used as an eco-friendly alternative to chemical coagulants to decontaminate water polluted with cyanobacteria blooms.