Investigation on operational parameters and membrane fouling performance in treating synthetic aquaculture wastewater via forward osmosis with sucrose as draw solution

Abstract

Forward osmosis (FO), a membrane separation process driven by a natural concentration gradient, is served as a potential strategy in the aspect of wastewater treatment. In this work, a worthy attempt at aquaculture wastewater treatment using a self-made FO system was conducted, confirming it was a promising approach to treating aquaculture wastewater. Optimization of operational parameters of the FO system, including draw solution (DS) concentration, cross-flow velocity, and DS temperature, was systematically investigated to enhance the running efficiency. Different selected parameters highly influenced the water flux during the single-factor experiments, and the findings indicated that the optimal conditions were DS of 1.5 M, cross-flow velocity of 15 cm/s, and temperature of 32 °C with consideration of FO performance and economical cost. An excellent linear relationship between chemical oxygen demand (COD) changing multiples and operational parameters was obtained from experimental results, offering a great interception performance of organic contamination. On the basis of optimal operating conditions, membrane fouling experiments with different running time were conducted, and the microscopic morphology and element composition of the fouled membrane were also analyzed. The results demonstrated that a layer of cake was coated on the surface of the membrane, and the main elements in the fouling cake included C, O, Na, and S, which were highly determined by the component of the feed solution (FS) and working time. Afterward, the 60-h FO fouled membrane was cleaned under the method which combined hydraulic power and chemical agents, and the water flux recovered to 12.79 Lm−2 h−1, proving a good performance for the recovery of water flux. This investigation showed that employing sucrose as DS was effective for reducing wastewater volume, and it provided an alternative choice and a sustainable way for the separation of organic pollutants from water resources.