With low prices for petroleum and the rising demand for energy sources, most petroleum companies are trying to find ways to make existing technologies more efficient. Since renewable sources have not established themselves as sufficient means to meet energy requests yet, the world is concentrating on unconventional hydrocarbon reservoirs. Hydraulic fracturing, which is an essential part of the current well stimulation process in unconventional fields, requires large amounts of freshwater. At the same time produced water, coming from underground during petroleum production, is considered to be one of the biggest challenges to increase the productivity of wells. To mitigate the scarcity of freshwater and disposal of contaminated produced water, operators are actively investing in technologies that can be used to economically turn wastewater into clean water. In this study, the efficacy of the coagulation-flocculation-sedimentation (CFS) process was investigated on 14 produced water samples collected from the Permian basin. First, the samples were characterized in terms of pH, total suspended solids (TSS), total dissolved solids (TDS), zeta potential (ZP), turbidity, organic matter presence, and ion concentrations. Then, a jar test was used to pretreat these wastewater samples in a laboratory. Varying doses of alum and ferric sulfate were tested in the coagulation process. In the flocculation process cationic starch and polyamine were tested with a dose of 20 mg/L. After the jar test pH, TSS, TDS, ZP, and turbidity of samples were measured again. The optimum dose of the coagulants was determined based on the maximum TSS removal. All measured values of the parameters at optimum coagulant doses were analyzed by using Pearson correlation. Produced water characterization results indicated that the samples are high in TDS and dissolved Na+ and Cl? ions are the main reason for that. Zeta potential analyses showed that TSS in the wastewaters are mainly negatively charged. The most TSS reduction of 86% on average was achieved by addition of ferric sulfate as a coagulant. In some wells, the addition of cationic starch as a flocculant showed 10% on average reduction in TDS. Pearson correlation revealed some positive correlations between TDS and ZP, Ca+ and Mg+ ions. On the other hand, the negative correlations were determined for TSS and depth, Li and depth, ferric sulfate optimal dose and ZP, and TDS and pH.
