Biology Reference
In-Depth Information
Fishmeal and Fish Oil Waste Water
Fishmeal wastewater (FWW), one of the main wastes of the fi sh processing
industry, contains soluble protein, high concentrations of suspended
solids with little amount of Ca, Mg, P, Na and S. Figure 8.3 shows the
process for fi sh meal and fi sh oil production including approximate
fi gures for quantities of inputs and outputs. Anaerobic nitrifi cation and
denitrifi cation can result in 20-70% removal of the initial chemical oxygen
demand (COD) especially due to the presence of fats and proteins (Huang
et al., 2008). Physical-chemical methods such as coagulation-fl occulation,
centrifugation or nano-fi ltration can be used to recover solids (especially
insoluble proteins) to be recycled to the fi sh-meal production (Garrido
et al., 1998).
Landed fi sh:
1000 kg
Emissions to air:
Boiler emissions Odour
Water vapour 600-700kg
Water:
Clearing and
processing: 0.2 m
3
Fresh water for
steam: 0.3 m
3
Sea water: 20 m
3
Wastewater 21 m
3
:
COD (off loading) 30 kg
COD (processing) 12 kg
Fish meal
and fi sh oil
production
Energy:
Fuel oil: 49 L
Electricity: 32 kW.h
216 kg fi sh meal
34 kg fi sh oil
Fig. 8.3
Inputs and outputs for fi sh meal and fi sh oil production using average technology.
Once the solids are separated, most of the soluble COD of the waste
waters can be effi ciently removed by anaerobic digestion. In spite of the
high effi ciency reached in anaerobic treatment, an organic load accounting
for about 20% of the initial COD remains in the waste water, thereby
necessitating a further treatment for COD and nitrogen removal. The
particular characteristics of these waste waters are their high nitrogen
content as ammonia or organic nitrogen, their salinity and quite a high
COD, which can complicate the nitrifi cation step. After their treatment by
anaerobic digestion, effl uents with high ammonia and organic nitrogen
contents and a fraction of residual COD are produced. A biological
nitrifi cation/denitrifi cation process is proposed to reduce both the residual
carbon and the nitrogen. The aerobic stage has the double objective of
