Biomedical Engineering Reference
In-Depth Information
the separation is mainly based on their sizes. Membrane material is usually made up of
ceramics, teflon, polypropylene, or other polymers. Applications of microfiltration for water
treatment in fishery industry have been reported.
A microfiltration membrane with 0.4 μm nominal pore size has been installed in a
membrane bioreactor for treatment of a saline backwash flow from a re-circulating
aquaculture system with a total of 35 tonnes of annual rainbow trout ( Oncorhynchus mykiss )
production (Sharrer et al., 2007). The membrane bioreactor performed exceptionally well
during this study. The physical exclusion of total suspended solids and bacteria (total
heterotrophs and total coliform) from the mixed-liquor suspended solids (MLSS) was nearly
completed. Further, the associated biological oxygen demand was almost completely
removed. Consistent removal of total nitrogen at all treatment levels was achieved. It
provided that sufficient acclimation of each salinity level was also given. A clear water was
collected from permeate side. This system can treat approximately 22 m 3 /day.
Gemende et al. (2008) tested two microfiltration systems, Zenon ZW500 (PVDF,
nominal pore size 0.04 μm, membrane area 10 m 2 ) and Eido-HF-PP-M6 (PP, nominal pore
size 0.1 μm, membrane area 12.75 m 2 ) in pilot scale (in 6 culture tanks, each with a volume of
1 m 3 and a fish stocking density of about 20 to 60 kg/m 3 ) at the aquaculture company
Fischwirtschaftsbetrieb Andreas von Bresinsky, Oelzschau, Germany. The tests showed the
applicability of both microfiltration systems to maintain process stability of the biological
water purification and fish breeding. In addition, the biomass was enriched to concentrations
that allow a subsequent utilization by fermentation. Furthermore, wastewater and residual
loads were reduced remarkably. For long-term operation (more than one year) it could be
proved that the integration of microfiltration is not only technically and economically
interesting for the special re-circulating aquaculture system, but also results in remarkable
reduction in wastewater and residual loads. Though the initial fluxes (about 8 to 15 l/m 2 h)
and average fluxes (about 3 to 5 l/m 2 h) in this test were relatively low. This could be
attributed to the small transmembrane pressure (less than 0.05 bar) and the high retentate
biomass concentrations up to 15 g/l. The flux values for the microfiltration of formulated fish
water reported by Viadero et al. (2002), have ranged from 12.5 to 250 l/m 2 h for suspended
solid concentration of about 5 to 18 mg/l.
Surimi is a Japanese term of washed and dewatered fish mince widely used as a raw
ingredient in manufacturing of artificial crab meats or kamaboko (Lee, 1984). For surimi
processors, recovering the suspended solids (myofibrillar proteins) is more commercially
interest. Huang and Morrissey (1998) successfully performed a continuous filtration to
recover the suspended myofibrillar proteins from minced-fish washing water at refrigerated
temperatures (12-15 o C) using polysulfone microfiltration membranes with a nominal pore
size of 0.2 μm. Lin et al. (1994) used microfiltration for recovering proteins and recycling
water from commercial surimi processing wastewater. The solids in the final dewatering
process (screw press) were concentrated up to 15.5 folds by a rotary screen (pore size of 100
μm) followed by microfiltration (pore size of 50 and 30 μm, in series). The result
demonstrated that the proteins recovered by microfiltration showed highly functional
properties in comparison with proteins in regular surimi. Solids recovered from the surimi
processing wastewater by microfiltration could be directly added to surimi to increase yield
without any effect on its quality.
According to its separation capacity, microfiltration has been more widely applied as a
pretreatment method. Afonso and Borquez (2002) applied a microfiltration process (pore size
Search WWH ::




Custom Search