Natural coagulants have been increasingly popular in the past few years due to its benefits and the fact that it resolves mos t of the associated problems when using chemical coagulants. Plant-based natural coagulants perform coagulation either by polymer bridging or charge neutralization, it can be extracted from various plant components. Concerted research and development efforts have been conducted in discovering new plant species and constituents that can be used as natural coagulants, which further boosting the effectiveness of existing plant-based natural coagulants. The objective of this paper is to provide a mini review on studies done over the span of ten years regarding plant-based natural coagulants. This paper also includes advantages and disadvantages of natural coagulants prior to identify several potential research gaps to provide platform towards the need of further study.

The adequacy of chemicals as coagulants such as alum is all around perceived. Nevertheless, there are numerous drawbacks related with the use including high operational costs, impeding impacts on human wellbeing and generation of huge sludge volumes. In this manner, it is crucial to supplant these chemical coagulants with organic-based coagulants to minimize the downsides. Therefore, the aim of this study is to identify the suitability of selected local wastes in becoming organic-based coagulant as to treat raw water. Regarding choice of organic-based coagulants, this study focused on the local waste materials, which are chestnut peels, bagasse and maize cobs. These waste materials were prepared by washing, drying, grinding lastly sieving in obtaining powder of coagulants ready to be used. A jar test was then performed to decide the effect of individual characteristic coagulants on the effectiveness of turbidity removal under different working variables of pH and coagulant dosage. Based on the findings, bagasse contributed to the highest yield of 79.5% followed by chestnut and maize cob. From the jar test experiments, the optimum dosage of 90 mg/L and pH 7.5 was obtained. At these optimizations, highest turbidity removal of 97.3% was recorded by bagasse compared to the other tested natural coagulants. This showing that bagasse as one of the representatives of organic wastes has the potential to physically treat the water. Keywords: Organic-based coagulant; Organic wastes; Coagulant dosage; Turbidity removal.

It is important to develop renewable bio-coagulants to treat turbid water and efficient use of these bio-coagulants requires process optimization to achieve robustness. This study was conducted to optimize the coagulation process using bio-coagulant of deshelled Carica papaya seeds by employing response surface methodology (RSM). This bio-coagulant was extracted by a chemical-free solvent. The experiments were conducted using the Central Composite Design (CCD). Initially, the functional groups and protein content of the bio-coagulant were analyzed. The Fourier Transform Infrared Spectroscopy analysis showed that the bio-coagulant contained OH, C=O and C-O functional groups, which enabled the protein to become polyelectrolyte. The highest efficiency of the bio-coagulant was obtained at dosage of 196 mg/L, pH 4.0 and initial turbidity of 500 NTU. At the optimum conditions, the bio-coagulant achieved 88% turbidity removal with a corresponding 83% coagulation activity. These findings suggested that the deshelled Carica papaya seeds have potential as a promising bio-coagulant in treating the polluted water.

The adequacy of chemical coagulant such as alum is all around perceived. However, there are numerous drawbacks including impeding impacts on human well-being and generation of high sludge volumes. Therefore, this study was conducted to investigate potential of fruit wastes - jackfruit (artocarpus heterophyllus) seeds, banana trunk peduncles (musa) and mango (mangifera indica) seeds in becoming natural coagulant to treat wastewater. A series of jar test was performed to determine the effect of individual coagulants on turbidity removal, coagulation activity and COD removal under various operating factors such as type and concentration of solvents used for extraction, pH and coagulant dosage. From the findings, optimum solvent concentration of 2.5M of sodium hydroxide (NaOH) reacted with banana trunk peduncles at optimum pH and dosage of pH 7 and 50 mg/L, respectively with turbidity removal of 90.2%, coagulation activity of 83.4% and chemical oxygen demand (COD) removal of 94.8%.

This study evaluated the efficiency of deshelled papaya seeds as the natural coagulant in improving quality of river water. The deshelled papaya seeds biomass was mainly characterized for functional groups using FTIR, surface charge and protein content. Coagulation and flocculation tests were conducted using batch test for various dosages and pH values. The optimum dosage and pH were then tested in treating river of Class III to Class V. The functional groups in deshelled papaya seeds were O-H, C=O and C-O groups. The surface charge and protein content was +0.4 meq/g and 363 mg/g, respectively. The deshelled papaya seeds coagulant was able to remove turbidity up to 87.6 and 88.3% for river of Class III and Class IV, respectively, as well as 57.6 and 62.1% of total coliform and escherichia coli, respectively, from Class III river at dosage 196 mg/L and pH 4. This study demonstrated that the deshelled Carica papaya seeds-derived coagulant is capable in treating common pollutants of river and simultaneously shows antibacterial properties.