Design and function of a closed, recirculating seawater system with denitrification for the culture of black tiger shrimp broodstock
P.
Menasveta, T. Panritdam, P. Sihanonth, S. Powtongsook, B. Chuntapa, P.
Lee-2001
Aquacultural
Engineering, 25 (1): 35 - 49
Abstract:
A
closed, recirculating seawater system with a denitrification process was
designed for the culture of black tiger shrimp broodstock. The system
comprised a circular rearing tank (9 m3 volume), a nitrifying
biofilter (6 m3 volume) and denitrification process. The
denitrification process comprised a deoxygenation column, a bacterial
substrate column (143 L volume) and a re-aeration column connected to the
biofilter. The experimental period was 81 weeks, consisting of 3 sequential
trials using different substrates, bacterial inoculates and carbon sources:
Trial 1- porous plastic balls for substrate, mangrove soil for inoculant and
ethanol for the carbon source; Trial 2- crushed oyster shell for substrate,
a strain of laboratory cultured bacteria for inoculant and ethanol for the
carbon source; and Trial 3- crushed oyster shell for the substrate, no
inoculant and methanol for the carbon source. The nitrifying biofilter
controlled ammonium-N and nitrite-N within acceptable ranges
(<0.5 and <0.2 mg L-1, respectively). The nitrate-N,
however, became elevated gradually during trial 1 (<50 mg L-1).
During trial 2, modification of bacterial substrate and the inoculation with
denitrifying bacteria reduced nitrate-N in the denitrification column
and the rearing tank (p<0.05). Changing the carbon source to
methanol and increasing the hydraulic residence time in trial 3 resulted in
a significant reduction (P<0.05) in nitrate-N (from >160
to <25 mg l-1) without the need for bacterial inoculation.