Evaluation of Nitrification Performance Using Nitrifying-DHS Reactor with Various Sponge-Pore Sizes for Breeding Tank of Marine Aquaria

Abstract

The effect of sponge-pore size for a combined downflow hanging sponge (DHS) and upflow sludge blanket (USB) filtering system for the nitrification and denitrification, respectively, of a marine aquaculture system was evaluated. The nitrifying DHS reactor maintained the concentrations of total ammonia nitrogen and NO2 -N of the breeding water at 0.08 mg-N L and 0.05 mg-N L, respectively. The DO concentration in the breeding water was about 6.17 mg L without direct aeration of the tank. Despite the high DO of the denitrifying USB reactor influent, the nitrogen-removal performance was good and the NO3 -N concentration in the breeding water was maintained below the theoretical value. Regarding the effect of sponge-pore size for nitrification by the DHS reactor, the sponge with the smallest pore size, named CFH-30, had the fastest nitrification rate and sludge growth rate. Microbial community analysis of sludge contained in sponge revealed that sponge with the largest pore size had the highest detection rates for ammoniaoxidizing archaea and nitrite-oxidizing bacteria.