TABLE OF CONTENTS Pages Symposium 1 - the National Sea ...

And the physical characteristics of fish manures (Chen et al., in press) are described as:
• Wide size distribution
• Significant non-settleable portion, ~ 50%
• Organic in nature, > 80% by weight
• Specific gravity < 1.1
• High in nutrient content
Table 1. Waste generation (kg/day per 1,000 kg live weight) from a catfish RAS and
other commercial animal production systems (Chen et al., 1997
Animal BOD5 Solids TKN Sludge Volume
(L)
Catfish 0.8-1.3 4.2 0.20 70-420
Beef cattle 1.6 9.5 0.32 30
Dairy Cow 1.4 7.9 0.51 51
Poultry 3.4 14.0 0.74 37
Swine 3.1 8.9 0.51 76
Total suspended solids (TSS) are a key indicator of overall water quality and the
efficiency of the solids removal system. Chen et al. (1993) expressed the various key
water quality parameters in a RAS system with catfish in relation to TSS (Table 2):
Table 2. TSS (mg/L) and BOD, COD, TKN and TP expressed as weight percentage of
the TSS (from Chen et al. 1993
TSS
(Mg/L)
BOD5 BOD20 COD TKN TP
Mean 973 23 59 101 4.0 0.7
STD 260 6.6 16.9 17.7 0.7 0.2
As mentioned, the effectiveness of removing manures and suspended solids from an RAS
is extremely critical. Chen et al. (1994) described several unit operation processes and
their appropriateness for moving solids based upon solids size:
Gravitational separation
• settling tanks (particles > 100 micron)
• hydro-cyclones
• foam fractionators (particles < 30 micron including dissolved solids)
Physical filtration
• granular filter (particles > 60 micron)
• sand filter (wide range including particles < 30 micron)
• bead filter (wide range including particles < 30 micron)
• screening (screen size dictates, typically > 60 micron)
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