Optimising the Removal of Humic Substances from Peat Water by Moringa oleifera Seeds

UMI ZUBAIDAH, SETERIK (2023) Optimising the Removal of Humic Substances from Peat Water by Moringa oleifera Seeds. Masters thesis, University of Malaysia, Sarawak.

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Abstract

Widely used commercial coagulants such as alum and ferric chloride have been related to a variety of neurological and neurotoxic diseases due to the existence of their residuals. Therefore, the purpose of this work was to optimise the performance of Moringa oleifera seed, a natural coagulant, to remove humic substances from peat water, a potential source of drinking water. The coagulant was derived by drying the seeds for several days and then crushing them into a fine powder. Various instrumental techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), Fourier Transform Infrared Spectroscopy (FTIR), and gas chromatography-mass spectrometry (GC-MS) were used to assess the morphology, functional groups and composition of the seeds. The SEM images revealed that the morphology of Moringa seeds is amorphous, with no fixed shape and numerous tiny pores. EDX statistics showed that carbon was the most abundant element, followed by oxygen. The FTIR spectrum revealed the coagulant's ionizable groups, which are hydroxyl, carboxyl, and amino groups. GC-MS results revealed that oleic acid is one of the primary components of the seeds, which mostly consist of fatty acids that aid in the coagulation process. In addition, the n-hexadecanoic acid composition in its methanolic extract demonstrated that the seeds possess antibacterial capabilities. Peat water samples were analysed for pH, dissolved oxygen (DO), turbidity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solid (TSS), and humic substance ratio (E4/E6), with the water, was then classed into Class III of National Water Quality Standard (NWQS), requiring considerable treatment for water supply. Box-Behnken Design (BBD) and Response Surface Methodology (RSM) were used to optimise three independent factors that influenced the coagulation process (coagulant dosages, pH of peat water, and contact time) and a quadratic model was acquired data. The optimum conditions of 1.94 g/L of coagulant, pH 7.6, and contact time of 86 min resulted in the removal of 88.4% of humic substances, closer to the predicted removal of 91.1%. The largest inhibition zone was demonstrated by the ethanolic extracts against S. aureus (18.33 ± 0.58 mm), while the weakest activity was observed in hexanic extract against E. coli at 5.00 mm. These findings ascertain that M. oleifera possesses antibacterial properties against both gram-positive and gram-negative bacteria. In summary, this study explores the potential of M. oleifera seeds as a natural coagulant for treating peat water by characterising their properties, optimising their coagulation, and testing their antibacterial activity. The findings suggest that M. oleifera seeds have promising potential for use in water treatment and may provide a safer and more environmentally-friendly alternative to commercial coagulants. Keywords: Moringa oleifera, coagulation-flocculation, response surface methodology, antibacterial

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