Denitrification with polycaprolactone as solid substrate in a laboratory-scale recirculated aquaculture system.

A denitrification system based on the biodegradable polymer Poly-epsilon-Caprolactone (PCL) was tested in a laboratory-scale recirculated aquaculture system with eels in comparison to a reference system without denitrification. The experiments were conducted with fluidized bed reactors in two parallel systems to examine the feasibility and performance of the process and to observe the condition of fishes by measuring weight gain during the test-period. The most evident effect of the system with denitrification was the low nitrate concentration compared with the untreated reference system. A further advantage was the stability of the pH in the systems with denitrification whereas pH of the untreated water decreased due to nitrification. All over the test-period the eels showed a similar weight gain in both systems.