This study explored the application of whole and defatted Moringa oleifera seed-derived coagulants in powder (P-MOS and DP-MOS), aqueous extraction (AEP-MOS and AEDP-MOS), and saline extraction (SEP-MOS and SEDP-MOS) in the treatment of a synthetic turbid water by coagulation, flocculation, and sedimentation in a jar test apparatus. The performance of M. oleifera seed-derived coagulants was quantified and compared with alum in terms of the ability to neutralize and restabilize the suspension charge, turbidity removal, effect on pH and electrical conductivity, residual organic matter, as well as cytotoxicity in the treated water. All evaluated forms of M. oleifera seed-derived coagulants were able to neutralize and restabilize (in overdose) the particles charges in the suspension. Saline extractions obtained the best turbidity removal results (90%) between the M. oleifera seed-derived coagulants, while alum removed 98% of turbidity. Differently from alum, increased dosage of M. oleifera seed-derived coagulants did not change pH value. Saline extractions and, to a lesser extent, alum increased the electrical conductivity with increasing coagulant dosage. M. oleifera seed-derived coagulants increased residual organic matter (DOC), unlike alum, which did not change this property with increasing dosage. Saline extractions at high dosages enhanced the cytotoxicity to mammalian cells. On the other hand, defatted seeds reduced water cytotoxicity when compared to whole seeds. Despite not being able to reduce the residual organic matter, the previous oil extraction proved to be an important step in the processing of M. oleifera seed-derived coagulants, not changing the turbidity removal capacity and reducing the cytotoxicity of the treated water in addition to generating a significant by-product (Ben oil). Although saline extractions have shown the best turbidity removal results, they should be used with caution due to increased electrical conductivity and cytotoxicity of the treated water at high dosages.

Coagulation is the most sensitive step in drinking water treatment. Underdosing may not yield the required water quality, whereas overdosing may result in higher costs and excess sludge. Traditionally, the coagulant dosage is set based on bath experiments performed manually, known as jar tests. Therefore, this test does not allow real-time dosing control, and its accuracy is subject to operator experience. Alternatively, solutions based on machine learning (ML) have been evaluated as computer-aided alternatives. Despite these advances, there is open debate on the most suitable ML method applied to the coagulation process, capable of the most highly accurate prediction. This study addresses this gap, where a comparative analysis between ML methods was performed. As a research hypothesis, a data-driven (D²) fuzzy inference system (FIS) should provide the best performance due to its ability to deal with uncertainties inherent to complex processes. Although ML methods have been widely investigated, only a few studies report hybrid neuro-fuzzy systems applied to coagulation. Thus, to the best of our knowledge, this is the first study thus far to address the accuracy of this non-hybrid data-driven FIS (D²FIS) for such an application. The D²FIS provided the smallest error (0.69 mg/L), overcoming the adaptive neuro-fuzzy inference system (1.09), cascade-correlation network (1.18), gene expression programming (1.15), polynomial neural network (1.20), probabilistic network (1.17), random forest (1.26), radial basis function network (1.28), stochastic gradient tree boost (1.25), and support vector machine (1.17). This finding points to the D²FIS as a promising alternative tool for accurate real-time coagulant dosage in drinking water treatment. In conclusion, the D²FIS can help WTPs to reduce operating costs, prevent errors associated with manual processes and operator experience, and standardize the efficacy with real-time and highly accurate predictions, and enhance safety for the water industry. Moreover, the evidence from this study can assist in filling the gap with the most suitable ML method and identifying a promising alternative for computer-aided coagulant dosing. For further advances, future studies should address the potential of the D²FIS for the control and optimization of other unit operations in drinking water treatment.

This study evaluated the use of Moringa oleifera (MO) seed as a natural coagulant for the removal of turbidity and apparent color in the water treatment with low initial turbidity through the in-line filtration technique. The morphology and surface charge were investigated by characterization techniques such as optical microscopy, laser particle size, and zeta potential. The cationic proteins of the MO seed were extracted in aqueous solution. The jar test showed the potability standards for turbidity and apparent color were reached in the pH range from 4.0 to 8.5 and dosages ≥ 5 mg L-1 of MO. The dominant coagulation mechanism is adsorption and charge neutralization. This study showed that treating low-turbidity water with MO seed by the in-line filtration technique is possible.