Abstract The aim of this study was to investigate the reduction of total dissolved solids (TDS) from aquaculture wastewater using Sesamum indicum seeds extract (SIC). The physicochemical properties (protein content, carbohydrate content, etc) of the seeds were determined. The coagulant was obtained from the seeds using the salt extraction technique. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were done the coagulant (SIC) to determine its morphology and functional groups present, respectively. The effects of SIC dosage (0.1-0.5 g/L), pH (2-4), temperature (303-323 K) and settling time (0-60 min) on the reduction of TDS using SIC were examined. The coagulation-flocculation kinetics of the process was also studied. Sesamum indicum seeds were found to contain 30.6 % protein and 7.58 % carbohydrate which implies that it can be used as a coagulant for solids/particles removal. Maximum removal of 82 % was obtained at the optimum conditions of dosage: 0.4 g/L, pH: 2, temperature: 303 K and settling time: 60 min. The coagulation-flocculation parameters were successfully determined using the first-order (where reaction order, α = 1) and second-order (α = 2) reactions at the optimum conditions. The regression coefficient, R2 values indicated that the removal of TDS using SIC fitted into the second-order reaction (R2 = 0.9837) than the first-order reaction (R2 =0.9314). This implies that the order of the coagulation reaction, α is 2. At these conditions, the reaction rate (Km) and coagulation-flocculation half-life ( ) were evaluated as 0.0002 L/g.min and 20 min, respectively. From this study, it can be concluded that Sesamum indicum seeds can be applied for the pretreatment of aquaculture effluents.
Keywords Coagulation-flocculation, Sesamum indicum seeds, Total dissolved solids, Aquaculture wastewater, Wastewater treatment, von Smoluchowski model.