Biomedical Engineering Reference
In-Depth Information
of 5-10 μm) as pretreatment process before ultrafiltration of effluent from fish meal
production in a fish meal factory located in Talcahuano, Chile. The result indicated that
microfiltration with a pore size of 5-10 μm was an efficient pretreatment process for this
effluent. Besides removing a great part of the suspended matter (visual observation),
microfiltration drastically reduced the oil and grease content which could be adsorbed onto
the ultrafiltration membrane surface, thereby affecting its performance.
During recovery of protease from the spleen of yellowfin tuna which is a solid waste
from tuna canning process, microfiltration has been applied as a pretreatment process to
remove suspended solids from spleen extract before recovery of protease by ultrafiltration (Li
et al., 2008). A hollow fiber membrane with pore size of 0.1 μm was employed in a cross-
flow microfiltration system. All visible solids in spleen extract can be removed by
microfiltration with given conditions while transmission of protease was higher than 0.90.
Microfiltration could remove not only suspended solids but also large molecular weight
proteins. As a consequence, protease was also partially purified by microfiltraiton. The clear
permeate from microfiltration could be used as a feed for concentration and purification of
protease by ultrafiltration. Since suspended solids and a part of proteins were removed by
microfiltration, the fouling load in ultrafiltraion process was significantly reduced.
3.2. Ultrafiltration
Ultrafiltration is a selective fractionation process using applied pressures up to 10 bars. It
is employed for concentration of suspended solids and solutes having molecular weight
greater than 1,000 Da. The permeate contains low-molecular-weight organic solutes and salts.
Ultrafiltration has been used for fractionation, concentration and purification of proteins and
some bioactive compounds (e.g. bioactive peptides, chitooligosaccharides) produced from
fishery processing waste. In comparison with microfiltration, ultrafiltration could perform a
higher capacity of separation with a smaller pore size. In comparison with nanofiltration and
reverse osmosis, ultrafiltration requires lower applied pressure. Thus, ultrafiltration probably
provides the most applications in fishery industry. Within the fish processing industry,
ultrafiltration has been mostly applied for brine recovery, wastewater treatments, recovery of
marketable compounds from wastes, and applied as a pretreatment process for nanofiltration
and reverse osmosis. However, to operate properly, ultrafiltration usually requires the
removal of fats, large membrane surface and frequent washing (Marti et al., 1994). Thus there
must be a suitable selection of membrane and cleaning systems to prolong its lifetime.
Ultrafiltration treatment has been proposed as an alternative to secondary biological
treatment, and has been proved to be effective in the organic matter recovery in fish canning
industry (Del-Rosario and Duldulao, 1988). The rejection coefficient for either protein or
carbohydrate solute of the tuna broth was approximately 54.5% while solute recovery was
about 90%. The ultrafiltered broth had negligible turbidity and odor. It has been also reported
that recovery of 90% of proteins from red-meat fish processing wastewater was obtained
when ultrafiltration was applied and proteins were concentrated from 0.1-2 % to 0.4-18 %
(NovaTec, 1994).
Two ultrafiltration modules equipped with Ceraver and Patterson Candy International
(PCI) membranes were tested for recovery and concentration of proteins from the wastewater
of a fish plant. Despite of different cut-off values, apparent rejection coefficients were rather
