چكيده به لاتين
In modern society, due to urbanization and industrial development, the release of wastewater containing oil into the environment increases. Oily wastewater dangerous because of its oil content substantial threats to soil, water, air and human. Removing oil from water is increasingly important in many industries, such as the oil and gas industry, the petrochemical industry, and the food industry, due to the large volume of oil wastewater they produce. Coagulation and flocculation technology, which is widely used in water treatment, has unique advantages in the treatment of oily wastewater, because it can treat without phase transfer, easy operation, low cost and good efficiency. With the continuous increase in the production of sludge in water treatment plants and in line with the legal and economic measures to avoid waste generation and useful reuse of waste, several research efforts, especially in recent years to reuse sludge in water treatment plants in useful ways. Water treatment sludge can be considered as a valuable raw material for the treatment of various pollutants in wastewater due to its high content of metal hydroxide, mainly and easily available and free. Therefore, in this study, the removal of oil turbidity in water was investigated using Iron-based water treatment sludge and ferric chloride along with process optimization and modeling. For this purpose, in the first step, the effect of pH, coagulation dose, initial turbidity and mixing and settling times on the removal of turbidity from samples of artificial turbidity made with olive oil and distilled water were investigated using the Jar test. According to the results, the turbidity removal efficiency using water treatment sludge at acidic pHs, especially at pH 4, and increasing the dose in the range of 100 mg/L to 650 mg/L and also increasing the turbidity to 450 NTU increased. Turbidity efficiency was increased by using ferric chloride at pH 6 and increasing the dose in the range of 5 mg/L to 30 mg/L as well as increasing turbidity to 450 NTU. Also, increasing the fast and slow mixing times had little effect on the removal efficiency. Also, major removal of flocs occurred with water treatment sludge in the first 10 minutes and with ferric chloride in the first 20 minutes of sedimentation. In the second step, the coagulation ability of both coagulants and the effect of input parameters were evaluated using the Response Surface Methodology (RSM) method in Design Expert software. According to the results, the water treatment sludge had the best performance in removing the turbidity of the sample with the initial turbidity of 381.08 NTU and pH equal to 4.21, at a dose of 658.11 mg/L from the coagulant (93.5% turbidity removal). Ferric chloride had the best performance (91% removal of turbidity) in removing the turbidity of the sample with an initial turbidity of 450 NTU and a pH of 6, at a dose of 32.5 mg/L of coagulant. According to the results of Response Surface Methodology, the parameters of pH, coagulant dose and initial turbidity were the most effective parameters affecting the turbidity removal efficiency of both coagulants, respectively, which were consistent with the preliminary experiments. In addition to the results of jar experiments, light microscope images, scanning electron microscopy (SEM) showed the formation of flocs and coagulation process by the water treatment sludge. By performing zeta potential analysis, it was found that at the optimal pHs, the zeta potential is close to zero and at acidic pHs, double layer compaction occurs, which leads to better removal. But the mechanism of charge neutralization and sweep coagulation (at all pHs) also occurs.
