9420.pdf

Various types of flotation devices are available. A unit manufactured locally (known as
Aerosep) was recently pilot tested at the Ucluelet Seafood Processors facility which
processes surimi. The wastewater from the surimi process was first preconditioned with
coagulant and then fed to the Aerosep at a flow rate of approximately 4 m 3
/hr. It was
demonstrated that Aerosep, under optimum conditions, achieved a TSS reduction of
80-95 % and consistently achieved TSS levels of less than 200 mg/L (International Water
Solutions, 1993). Dosing levels of chemicals have not been reported.
5.3.4.2 Other Bubble Generation Systems
Other forms of bubble generation systems have been investigated. Among these, the
most common is dispersed (or induced) air flotation which makes use of an impeller and
draft tube assembly to supply air to the bottom of a reactor vessel, and to generate and
disperse the bubbles. To the knowledge of the authors, there are no full scale
installations of this kind of flotation cell for treating effluent from fish processing plants.
Other alternative bubble generation methods include in situ electrolysis of water
(electroflotation), and use of hydrogen peroxide to chemically generate oxygen bubbles.
Shifrin et al. (1972) reported high removal efficiencies of fats, suspended matter and COD
(99.8 %, 86.5% and 59.8% respectively) when fish cannery wastewater was treated with
.
dispersed air flotation.
Electroflotation may yield skimmings with a higher total solids content (9-12%) than DAF
(3-5%) (del Vane and Aguilera, 1990). Recovery of 85 % of protein from fish processing
wastewater was achieved using electroflotation after pH adjustment (del Vane and
Aguilera, 1990). It should be pointed out that no full scale installation exists.
The use of hydrogen peroxide instead of air in DAF units proved to be more effective in
fat, oil and grease recovery and BOD removal when poultry and meat processing effluents
were treated in DAF units (pers. comm. with Mr. Robert Gec of Degussa). Testing of
hydrogen peroxide in the fish processing industry is still to be done.
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