9420.pdf

offal with wastewater, which is the predominant offal disposal method in ‘Alaska, to fine
screening, and the use of dissolved air flotation in one plant in Newport, Oregon (see
Section 5.3.3). The level of treatment implemented depends to a large extent on the
location of the plant. The level of treatment at B.C. fish processing plants is generally
superior to that practised in Alaska and equal to that practised in Washington and
Oregon. Only three processing plants grind and discharge their offal in B. C.. A flow
diagram of a typical waste treatment scenario is shown in Figure 5.4.
Most fish processing plants in Northern Europe screen their effluent prior to discharge to .
the municipal sewer or to a receiving water body. Screen mesh sizes vary from 40 to
5000 um. The end of pipe treatment is not widely implemented and it appears to be
generally preceded by completion of an in-plant water reduction program which lasts
several years. End of pipe treatment typically involves a dissolved air flotation unit with
or without chemical addition. Only one facility has biological treatment (NovaTec, 1993a).
Generally, wastewater is generated at fish processing facilities from a variety of processes,
such as:
Intermediate fish storage;
Fish cleaning;
Fish transport (for example in wet pumps and fluming);
Fish freezing;
Fish thawing;
Preparation of brines; ‘
Equipment sprays;
Offal transport;
Cooling water;
Steam generation; and
Equipment and floor cleaning.
Most of these uses have been addressed in Section 4 and are inherently connected to
the particular type of fish processing taking place at individual facilities, such as the use
of cooling water for salmon canning. In addition to these applications, water is also used
to flush offal and blood from equipment and floors, and to transport or flume the offal to
floor drains and collections sumps. Department of Fisheries and Oceans Fish Inspection
Regulations require that all conveyor belts be equipped with water sprays, and automated
processing equipment generally have permanently installed water sprays to keep the
51
I