Removal of steroid hormones from mariculture system using seaweed Caulerpa lentillifera

The removal of steroid hormones from the mariculture system using seaweeds (Caulerpa lentillifera, Ulva pertusa, Gracilaria lemaneiformis, and Codium fragile) was investigated. The results illustrated that both 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) could be removed by the seaweeds at different levels, and the Caulerpa lentillifera was the most efficient one. More than 90% of E2 or EE2 at concentration of 10 µg/L was removed by Caulerpa lentillifera within 12 h. Processes including initial quick biosorption, the following slow accumulation, and biodegradation might explain the removal mechanisms of E2/EE2 by Caulerpa lentillifera. E2/EE2 removal was positively related to the nutrient level and the initial concentration of steroid hormone. A significant linear relationship for E2 and EE2 existed between the initial pollutant concentration and the average removal rate. The highest removal kinetic constant (k) value was obtained at 30°C as 0.34 /h for E2 and at 20°C as 0.28 /h for EE2, demonstrating the promising application potential of Caulerpa lentillifera in the water purification of the industrialized mariculture system with relatively high water temperature. Simultaneous and efficient removal of E2 and EE2 by Caulerpa lentillifera was still achieved after 3 cycles in the pilot-scale experiment. The steroid hormones and nutrients in mariculture wastewater could also be simultaneously removed using Caulerpa lentillifera. These findings demonstrated that Caulerpa lentillifera was the promising seaweed for the removal of steroid hormones in mariculture systems.