Treatment of simulated aquaculture water using biofilters subjected to aeration/non-aeration cycles

The overall objective of this research activity is the development of a fix ed-film biological nutrient removal (BNR) biofilter system for the reuse an d discharge of a selected aquaculture water. The three stage biofilter syst em used in the study provided alternating aeration/non-aeration cycles for phosphorus removal in two of the three biofilters. The removal of TOC and a mmonia improved as the cycle duration (CD) increased as a result of the red uction in the frequency of the transition periods between the cycles. The s ystem achieved limited net phosphorus removal due to the limited sludge was ting and lack of external organic carbon supplies during phosphorus uptake, However, the phosphorus activity in the system was significant and was mod ified by the CD. The denitrification activity was coupled with phosphorus u ptake and both activities appeared to have been supplied by an internal org anic carbon source. The major challenges of achieving phosphorus removal in the system include: (1) overcoming the deterioration in the performance of the system during t he transition period following the start of each new cycle; and (2) wasting the excess biomass following the aeration cycle. Without active sludge was ting, the system behaves as a phosphorus reservoir with a limited storage c apacity. On the other hand, frequent sludge wasting may disrupt the perform ance of the system. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.