7 Reduction of Seafood Processing Wastewater …
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drum screens are mechanically operated and complex in nature which consist of a
cylinder for rotating along its axis, and the effluent enters through an opening at
one end. However, it causes the breakdown of the solids, making it more difficult to
separate; high-intensity of waste streams should be minimized before screening or
even settling (Metcale and Eddy 2004; Chan et al. 2009; Mekonnen and Hoekstra
2015).
Sedimentation is used widely in the wastewater treatment industry. Sedimentation in the simplest form of removing the heavier particles from the water through
deposition due to mass of particles in the bottom of the tank or basin. In general,
sedimentation separates solids from water body using gravity settling of the heavier
solid particles.
This operation is used in the primary and also in secondary treatment to separate
the generated solids in biological process units such as activated sludge or trickling
filters. Sedimentation proceeds in many ways such as discrete settling, flocculent
settling, and zone settling based on the properties of the present solids. The average
removal efficiencies for BOD 5 was reported to be 91–99% by using sedimentation.
In fish-processing wastewater, the sedimentation removed 52–90% for SS and 72–
92% for TN and 72–77% for TP performances, found at 5 days HRT (Sohsalam
et al. 2008). A schematic diagram for discrete settling approach is shown in Fig. 7.5
(Baker et al. 2012; Baker 2016).
Flow equalization is crucial in reducing the hydraulic flow loading of the waste
stream. Equalization units consist of a flat tank and pumping equipment to reduce
the fluctuations of the waste streams. The equalizing tank increases flow loading
and makes flow rate to a uniform discharge over a 24-h day. Removal percentage
of BOD 5 from 50 to 55% was achieved in equalization tank of seafood wastewater
treatment plant by using fluctuations system and removed 40% of oil and grease and
50% of suspended solids (Goel et al. 2005; Hasar et al. 2009). Flow equalization
is normally used near the head end of the effluent discharge to the receiving water
bodies (Li et al. 2018).
Seafood processing wastewater contains large amount of oil and grease, which
will vary depending on the process used, the type of treatment, and operational
procedure. Gravitational separation is used to remove oil and grease. There are two
ways to breakdown emulsion: pH adjustment and heat. However, heat may not be
economical unless there is excess steam available as shown in Fig. 7.6 (EPA 2003;
Kim et al. 2010).
Electrocoagulation can also be applied to treat seafood processing wastewater.
Investigation on the effective conditions and several electrode materials showed that
aluminium was favoured compared to iron. The best charge loading reported was
1.67–9.95 F/m
3 wastewater with current density of 30–80 A/m
2 . The removal percentage of 94% for oil and grease was achieved for the wastewater tested (Chen et al.
2000).
Among effective systems used to remove oil and grease is the dissolved air flotation (DAF) procedure (reference). DAF uses air bubbles to remove suspended matter
from wastewater stream. The air bubbles attach themselves to discrete floating particles of oil and grease. The attachment reduces the specific gravity and increases
109
drum screens are mechanically operated and complex in nature which consist of a
cylinder for rotating along its axis, and the effluent enters through an opening at
one end. However, it causes the breakdown of the solids, making it more difficult to
separate; high-intensity of waste streams should be minimized before screening or
even settling (Metcale and Eddy 2004; Chan et al. 2009; Mekonnen and Hoekstra
2015).
Sedimentation is used widely in the wastewater treatment industry. Sedimentation in the simplest form of removing the heavier particles from the water through
deposition due to mass of particles in the bottom of the tank or basin. In general,
sedimentation separates solids from water body using gravity settling of the heavier
solid particles.
This operation is used in the primary and also in secondary treatment to separate
the generated solids in biological process units such as activated sludge or trickling
filters. Sedimentation proceeds in many ways such as discrete settling, flocculent
settling, and zone settling based on the properties of the present solids. The average
removal efficiencies for BOD 5 was reported to be 91–99% by using sedimentation.
In fish-processing wastewater, the sedimentation removed 52–90% for SS and 72–
92% for TN and 72–77% for TP performances, found at 5 days HRT (Sohsalam
et al. 2008). A schematic diagram for discrete settling approach is shown in Fig. 7.5
(Baker et al. 2012; Baker 2016).
Flow equalization is crucial in reducing the hydraulic flow loading of the waste
stream. Equalization units consist of a flat tank and pumping equipment to reduce
the fluctuations of the waste streams. The equalizing tank increases flow loading
and makes flow rate to a uniform discharge over a 24-h day. Removal percentage
of BOD 5 from 50 to 55% was achieved in equalization tank of seafood wastewater
treatment plant by using fluctuations system and removed 40% of oil and grease and
50% of suspended solids (Goel et al. 2005; Hasar et al. 2009). Flow equalization
is normally used near the head end of the effluent discharge to the receiving water
bodies (Li et al. 2018).
Seafood processing wastewater contains large amount of oil and grease, which
will vary depending on the process used, the type of treatment, and operational
procedure. Gravitational separation is used to remove oil and grease. There are two
ways to breakdown emulsion: pH adjustment and heat. However, heat may not be
economical unless there is excess steam available as shown in Fig. 7.6 (EPA 2003;
Kim et al. 2010).
Electrocoagulation can also be applied to treat seafood processing wastewater.
Investigation on the effective conditions and several electrode materials showed that
aluminium was favoured compared to iron. The best charge loading reported was
1.67–9.95 F/m
3 wastewater with current density of 30–80 A/m
2 . The removal percentage of 94% for oil and grease was achieved for the wastewater tested (Chen et al.
2000).
Among effective systems used to remove oil and grease is the dissolved air flotation (DAF) procedure (reference). DAF uses air bubbles to remove suspended matter
from wastewater stream. The air bubbles attach themselves to discrete floating particles of oil and grease. The attachment reduces the specific gravity and increases