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To the knowledge of the authors, no full scale anaerobic treatment at fish processing
facility exists.
5.3.6 Other Types of Treatment
A number of other types of treatment processes have been reported or tested on fish
wastes at the bench or jar scale level. They remain largely unproven with respect to
technical feasibility and costs. A highlight of selected ones are presented in this section.
5.3.6.1 Ultrafiltration
The ultrafiltration process employs a semipermeable membrane to separate macromolecular
substances from water. The membrane coats the wall of a closed space.
When the solution contained in the enclosure surrounded by the membrane is
pressurized, the water, inorganic salts and organic compounds of small molecular weights
are forced through the membrane and collected as a permeate. Macromolecular \
substances such as proteins are left within the membrane enclosure as concentrate
(Chao et al., 1980). To the knowledge of the authors no full scale ultrafiltration
installations exist in the fish processing plants.
The flux of permeate across the membrane is the most influential factor on the capital
cost and operating costs of an ultrafiltration process. It is generally felt, based on
laboratory scale tests, that a flux rate in the range of 0.33-0.61 m3/m2~day is the needed
for the ultrafiltration process to be economically feasible (Chao et al., 1980). Table 5.7
presents a summary of ultrafiltration efficiency in treatment of blue crab steam cooker
discharge (laboratory scale tests).
Ohsihima et al. (1993) reported recovery of 90 % of proteins from red-meat fish ,
processing wastewater when ultrafiltration was applied, and Ninomiya et al. (1985)
reported that proteins were concentrated from 0.1 -2 % to 0.4-18 % using ultrafiltration
treatment.
Precipitation and separation of proteins in aqueous solution can also be effected by
relying on electrolytic rather than chemical means. Effectiveness of direct acid
precipitation, ion exchange chromatography, ultrafiltration and microgas ‘dispersion -
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