A hybrid process of powdered activated carbon countercurrent two-stage adsorption and microfiltration for petrochemical RO concentrate treatment

•A countercurrent two-stage adsorption–microfiltration (CTA-MF) process was proposed.•Dissolved organics in petrochemical RO concentrate were removed efficiently.•A high overall recovery (91%) of reverse osmosis (RO) can be achieved.•A simple CTA-MF calculation method was established to predict the effluent.

In petrochemical wastewater reclamation, the dissolved biorefractory organics from reverse osmosis concentrate (ROC) is a key obstacle to increasing the overall recovery of reverse osmosis (RO) technology. A hybrid process of countercurrent two-stage adsorption and microfiltration (CTA-MF) was proposed to remove the organics in ROC by powdered activated carbon (PAC). In order to analyze the CTA-MF process, a simple calculation method was established based on the adsorption accumulation principle and response surface methodology (RSM) equations. Approximately 37% of fresh PAC was saved through the CTA-MF process compared with a conventional adsorption process. When the fresh PAC dosage was 0.48 g/L, the average values of chemical oxygen demand (COD) and dissolved organic carbon (DOC) were decreased from 94.1 mg/L and 25.6 mg/L to 36.9 mg/L and 6.98 mg/L, respectively, which coincided well with the predicted results and met the influent requirement of RO for high overall recovery.