Performance in nitrogen, turbidity and phosphorus removal in a RAS using moving bed settler and membrane aerated biofilm reactor

Abstract

The objective of this research was to evaluate the efficiency in the removal of nitrogen, phosphorus and turbidity in a Recirculating Aquaculture System (RAS) for Nile tilapia culture by means of a moving bed settler (MBS) and a membrane aerated biofilm reactor (MABR). In a RAS for the cultivation of Oreochromis niloticus with a biomass density of 21.7 kg/m3, the performance of an MBS operated with hydraulic retention time (HRT) of 0.6 hours and of an MABR with HRT of 1.2 hours was evaluated. The performance of the treatment units was determined by calculating the nitrogen removal efficiency in the forms of total nitrogen (TN), un-ionized ammonia (NH3-N), ammonium (NH4 +-N), total ammonia nitrogen (TAN), nitrites (NO2-N), nitrates (NO3-N), turbidity and total phosphorus (TP). The mean total removal efficiencies of the monitored water quality parameters were 98.6 % for turbidity, 17.5 % for TN, 42.8 % for TAN, 55.9 % for NO2-N, 36.3 % for NO3-N and 29.7 % for TP. The RAS treatment units, operated with relatively low HRT, demonstrated good performance in maintaining water quality in favorable conditions for tilapia farming.