Removal of tricaine methanesulfonate from aquaculture wastewater by adsorption onto pyrolysed paper mill sludge.

Tricaine methanesulfonate (MS-222) has been widely used in intensive aquaculture systems to control stress during handling and confinement operations. This compound is dissolved in the water tanks and, once it is present in the Recirculating Aquaculture Systems (RASs), MS-222 can reach the environment by the discharge of contaminated effluents. The present work proposes the implementation of the adsorption process in the RASs, using pyrolysed biological paper mill sludge as adsorbent, to remove MS-222 from aquaculture wastewater. Adsorption experiments were performed under extreme operating conditions, simulating those corresponding to different farmed fish species: temperature (from 8 to 30 °C), salinity (from 0.8 to 35‰) and different contents of organic and inorganic matter in the aquaculture wastewater. Furthermore, the MS-222 adsorption from a real aquaculture effluent was compared with that from ultrapure water. Under the studied conditions, the performance of the produced adsorbent remained mostly the same, removing satisfactorily MS-222 from water. Therefore, it may be concluded that the produced adsorbent can be employed in intensive aquaculture wastewater treatment with the same performance independently of the farmed fish species.