Improving waste solids quality and recovery from fish processing plants

Improving waste solids quality and recovery from fish processing plants

A. Ismond

Improving waste solids quality and recovery from fish processing plantsThis is part of A Sustainable Future: Fish Processing Byproducts
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The design and operation of fish processing plants can significantly impact the quality and quantity of recovered byproducts, especially if they are rendered into fish meal. Most fish processing plants are designed to maximize the recovery and quality of their food products with less consideration for the recovery and transport of non-food waste or processing byproducts. These plants generate a sizable percentage of waste as dissolved solids and very fine particles in wastewater, thereby reducing waste recovery. The recoverable fine particles that are sent to rendering will likely not be recovered as fish meal and will increase the pollutant load in the rendering operation wastewater.

A detailed inspection of a fish processing facility can reveal areas where waste solids can degrade because of inappropriate temperatures and times, and also areas where they can become contaminated. The degradation of the recovered solids has the potential to affect the protein quality of the rendered meal and oil byproducts.

Properly designed waste conveyance systems that recover waste solids before they reach floor drains or sumps are preferable. Fluming waste solids with water increases the breakdown of solids and decreases the amount of solids that can be recovered. Additionally, if saltwater is used for fluming it can increase the salt and ash content of the waste solids. If the solids are then rendered the resulting fish meal will be of a lower quality. Hence, dry conveyance of waste solids is preferred. For waste solids that circumvent the waste conveyance system, the design and operation of wastewater floor drains, sumps, and pumps can affect the quality and quantity of recovered waste solids. The same is true for the wastewater treatment equipment used for recovering waste solids. And finally, the methods by which potentially food-grade products are rejected, and unacceptable fish are added to the waste stream, can be of concern.

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