Evaluation of pre-treatment techniques for shale gas produced water to facilitate subsequent treatment stages

Two traditional pretreatment methods were adopted for the pretreatment of shale gas produced water in view of facilitation for subsequent treatment processes. The research was focused on alkali precipitation due to its better performance on shale gas produced water pretreatment compared with flocculation. Agitating time, settling time, stirring speed, dosage of coagulant aids were determined by optimal configuration. The results showed that adding together with 1.0 g/L NaOH and 2.0 g/L Na2CO3 under 200 rpm stirring for 5 min and after 30 min settling, suspended solids (SS) in the effluent could drop below 20 mg/L and concentration of hardness ion could be less than 150 mg/L, which was well ma the water quality to facilitate the following single or multiple-effect evaporation. The optimized alkaline pretreatment method towards produced water had excellent adaptability and practicability with economic cost and easy operation. It had significant potential and could be widely used in the shale gas produced water pretreatment process.