Water Quality Management Efficiency of Biofilteration in a Recirculating Aquacultural System

Abstract

One of the major challenges of recirculating aquaculture technology is the maintenance of water parameters at levels safe for the healthy growth of the aquatic life being reared. A biofilter is an indispensable component of a recirculating aquacultural system (RAS). It improves the biochemical qualities of the system water for re-use. In this study a fully designed and constructed recirculating aquacultural system was stocked with eighteen thousand catfish fingerlings and run for one complete rearing cycle of seventeen weeks using plastic as the biofilter media. Total ammonia nitrogen (TAN) concentration of the system was measured at the inlet and outlet points of the biofilter during the culture period. The results indicated that for the untreated water, the concentration showed a general increase through the culture cycle while for the treated water there was a marked drop in concentration values for the first four weeks, followed by a fairly constant value for the rest of the period. These values for the treated water were significantly (p < 0.05) below the critical value for safe fish culture. The maximum TAN value obtained for the untreated water was 12.770 x 10^-1 mg/l, while that for the treated water was 4.226 x 10^-1 mg/l. The minimum TAN values were 6.214 x 10^-1 mg/l and 1.396 x 10^-1 mg/l for the treated and untreated water respectively. Statistical analysis indicated significant (p < 0.05) difference between TAN values for treated and untreated water. Based on the TAN concentrations of       inflow and outflow of the trickling filter, its efficiency was determined over time and result showed that the plant reached at average efficiency of 79% in three weeks, having started with an efficiency of 32% at the beginning of operation.