Separation of tetracycline from wastewater using forward osmosis process with thin film composite membrane - Implications for antibiotics recovery

To minimize the risk of antibiotic wastewater generated by the pharmaceutical industries, the potential separation efficacy of tetracycline (TC) from aqueous solution using forward osmosis (FO) process with thin film composite membrane was systematically studied. First, the microstructure and transport properties of TFC membrane were characterized. Then, the effects of membrane orientation, feed velocity and solution pH on the behavior of the FO process for TC separation were studied. Finally, the performance of TFC membrane for TC separation in a long-term FO mode operation was investigated. The results showed that the membrane performance in FO mode (active layer facing the feed solution) and PRO mode (active layer facing the draw solution) was highly affected by solute resistivity (K) value. The water flux and TC rejection achieved over 20 LMH and 99.0% in FO mode, respectively. High TC concentration factor (CF) of 2.6 was obtained in FO mode, indicating the concentrated TC solution could be harnessed to recover the TC by conventional crystallization. However, severe water flux decline accompanied with low tetracycline CF was found in PRO mode, which was mainly attributed to serious fouling and high K value occurred in the porous support. With the flow velocity rising, the shear stress and mass transfer coefficient (k) on the membrane surface increased, alleviating the membrane fouling. Acidic environment would favor the separation due to the change of TC speciation and TFC membrane properties. A long-term testing demonstrated that more than 97% TC rejection and 74% water flux recovery were well maintained with simple hydraulic cleaning after 5 cycles FO mode operation. This work implied that the FO based technology could be developed as an effective alternative for the treatment of tetracycline antibiotic wastewater as well as the recovery of antibiotics from the wastewater. (C) 2015 Elsevier B.V. All rights reserved.