heterotrophic bacteria production on the solid waste obtained from the
drum fi lter of the recirculating aquaculture system resulted in additional
protein retention and nutrient discharge (Schneider, 2006a).
A shrimp hatchery effl uent was fed in three glass reactors at 24-27°C,
pH 7.8-8.0, oxygen concentration 8 mg/l, and hydraulic resistance time 5
d. Each reactor consisted of a retention chamber at the top for the water
treatment, three stages with the constructed microbial mats overlaid at
each stage, and several small holes serving as a sprinkling fi lter at the
bottom. The effl uent fl owed throughout the surface of the fi rst bed
which contained mats, and then sprinkled to the second and third bed.
The results indicated 97% ammonia N and 95% nitrate N concentration
removal, while 80% biological oxygen demand (BOD) reduction was also
Effl uent slurry produced in a recirculating aquaculture system with
African catfi sh was used as substrate for growing heterotrophic bacteria.
The effl uent was pumped in a bacteria growth reactor through the drum
fi lter of the recirculation system. The reactor was operated in a continuous
fl ow and HRT of 6 h, while different levels of molasses (0-2.5 g C/l) were
added to the effl uent due to organic carbon defi ciency of the fi sh waste. The
results indicated inorganic N and orthophosphate-P reduction from the
waste up to 90% and 98%, respectively. VSS concentration, Kjeldahl-N and
TOC levels increased with increasing molasses concentration (Schneider,
BO D (effluent)
BOD (after bioremediation)
Ammonia (after bioremediation)
Nitrate (after bioremediation)
Fig. 9.7 Trends in BOD 5 , ammonia, and nitrate concentration in effl uent and after
bioremediation with mats (Source: Paniagua-Michel and Garcia, 2003).