Wastewater Characterization of Fish Processing Plant Effluents

The primary product of herring processing of fish processing facilities in the B.C. Lower
Mainland is cured herring roe. Due to the relatively short fishing season and the necessity for
freezing herring to preserve fish shape and quality of the roe, herring processing is divided
into two distinct phases:
! Vessel unloading and freezing, and
! Thawing, roe "popping", and roe processing.
These phases take place at different times. The fish processing operations that occur during the
individual phases are described in detail in the following sections.
2.9.2 Vessel Unloading and Freezing
Herring are delivered to the fish processors suspended in chilled seawater in the holds of
fishing boats and fish packer vessels. Vessel unloading is done with wet pumps, as described in
Section 2.1. Intermediate storage of the herring may be required, as the capacity of the vessel
unloading pumps may exceed the throughput of subsequent handling steps.
Herring may undergo additional washing steps to remove blood, slime, and scales, before being
frozen and sent to cold storage. Freezing generally takes place in brine freezing channels which
contain a saturated sodium chloride solution at -18EC followed by tunnel freezing to rapidly
freeze the individual fish.
Herring sex sorters are available to separate male from female herring. The use of such sorters
results in reduced water consumption and wastewater contaminant loadings. Also reduced are
labour requirements for subsequent handling steps, as all male fish would be sent to a reduction
plant rather than undergoing additional treatment (washing, freezing, and belly slitting - see
below). Ideally, sex sorting of herring should take place immediately after vessel unloading.
FREMP 03/21/1994
Fish Processing Plant Effluent 15