Biology Reference
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5.9 mg/L, whereas no amylase activity was detected. In addition, protein
and amino acids values of treated whole bonitos were slightly higher
than treated fi sh waste. Volatile basic nitrogen (VBN) and trimethylamine
(TMA) were found to exceed the thresholds of 6 mg/100 g and 50 mg/100
g, respectively (Shih et al
.
, 2003).
A biofi lter reactor was operated to remove nitrogenous wastes, such
as ammonium, nitrite and protein from uneaten feed and cell debris, and
glucose in a recirculating aquaculture system. In a continuous fi xed-slab
reactor,
Aspergillus niger
NBG5 was used for the remediation of the above
nitrogenous wastes. The results showed that
A. niger
NBG5 consumed
the nitrogenous wastes simultaneously, removing more than 95% of the
wastes in 50 h, while ammonium and protein were metabolized prior to the
nitrite. In addition, the fungus metabolized nitrogen at low temperatures
(22°C), whereas carbon was metabolised at high temperatures (35°C)
g-cell/day) by
A. niger
NBG5 was observed at 35°C in the presence of
ammonium and nitrite (Hwang et al., 2004).
Hwang et al. (2007) investigated the potential removal of nitrogenous
substances by
Aspergillus niger
NBG5 in a continuous stirred tank reactor
(CSTR) system. In the CSTR system, glucose and aquacultural wastewater
were exchanged in a mixer every 24 h. Nitrite was removed during the
pretreatment of wastes using ozone. The nitrogenous wastes passed
CSTR with a hydraulic retention time of 3.3 h, an operating temperature of
7LPHK
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&2'
Fig. 9.1
Concentration of ammonium, nitrite, protein and TAN (1) after treatment with
A.
niger
at 22°C, and COD and TAN (2) after treatement with
Bacillus subtilis
(Hwang et al
.
, 2004,
2007; Liu and Han, 2004).
