General

Fish canning and byproduct manufacturing occurs in almost every country that borders on the ocean. The industry experienced a 20% increase in the quantity of fish processed and additional increases are expected as well. Exports of canned fish and fish meal are also increasing because of diminishing supplies in other countries. Allen Filters, Inc’s Engineering Department has many years of experience in devising comprehensive treatment plans for cannery water and waste water processing and pollution control.

This is part of a series highlighting several case histories of waste stream management in a variety of industries.

The following is a case history of a typical cannery with a severe waste water pollution problem, resulting is several significant fines.

Fish Processing

Defrost water

This cannery’s fish processing begins with freezing the catch as soon as it is brought in from the company’s 125 fishing ships. The ships have freezers on board to initially freeze the fresh catch. The catch is then moved to several very large freezers to await processing.

When the fish is subsequently defrosted, a significant flow of ice water with fish parts is generated around the clock. This is waste stream consists of cold water and some fish parts. This constitutes waste stream no. 1

Frying Oil

In addition to fish canning for human consumption the company also produces fried, breaded shrimp and fish sticks, ready for packing and exporting. The oil used is mostly soy and safflower oil.

The company wanted to reuse the oil as many times as could be safely done.

This was problem no. 2.

Boiler Fuel

The company’s boilers are burning heavy fuel (HFO) oil, which was causing problems with burner nozzles plugging and causing air pollution. The heat is used in several different operations such as cooking, salting and drying of fish heads and backbones for sale to Africa.

The HFO required pretreatment.

This was problem no. 3.

Fish Processing Waste Water

The most heavily polluted water is generated by the main fish processing area. The waste water contained large quantities of fish parts and blood, resulting a in high organic loading.

The precooking also generates some waste water, which is combined with the fish processing waste stream.

This was problem no. 4

Allen’s Engineers devised a comprehensive solution for all problems as is shown below. It emphasized not only treatment of fluids but also the reuse of purified water.

FIGURE 1 – COLD WATER TREATMENT AND REUSE

Solutions

The systems installed are shown in Figure 1.

Defrost Water Treatment and Reuse

The water generated by the defrosting operation is the least polluted. It has a minor amount of fish parts, but otherwise it is just cold at about 8-10 ? C. The cold water is pumped through a series of stainless steel reusable strainers. Each strainer has a backwash system, which is activated automatically by individual differential pressure switches. After each backwash, the strainers are ready to be used again. The backwash is directed to the fish meal operation to be turned into fertilizer or animal feed.

The clean cold water is directed to the heat exchangers to function as cooling water.

Heavy Fuel Treatment.

The company has several large boilers that use Heavy Fuel Oil (HFO).

Heavy Fuel Oil is a high-viscosity oil with a significant concentration of sulfur and rich in asphaltenes. Asphaltenes are long-chain, high molecular weight molecules that polymerize and create problems clogging burner nozzles and causing a high level of air pollution.

The solution to this problem was an additive that fractures the asphaltenes polymers, homogenizes the fuel, making it less viscous. The additive is also a combustion catalyst, which improves cleaner burning with less smoke and soot. Boiler maintenance is greatly reduced also.

The additive is injected into the fuel, prior to being subjected to a vacuum distillation process in an Allen Oil Conditioner, to eliminate water, volatile contaminants and reduce the sulfur content. The resulting homogenized fuel is pumped to the boilers. Significantly less smoke emitted by the boiler stack was immediately noted. Air pollution sampling will be instituted in the future.

Frying Oil Treatment and Reuse

Frying oil when continuously heated over a period of time may polymerize and form free radicals, which are hazardous to human health. It also has a tendency to become rancid and odorous. The remnants of flour and particles also tend to accelerate the deterioration of the oil.

The Allen Frying Oil treatment process consists of solids filtration of the hot oil in a kidney-loop fashion, through stainless steel recleanable strainers to remove solids such as flour particles and bread crumbs. The system is designed o withstand up to 1500 ?C. The oil is then pumped through activated carbon adsorption filters. The activated carbon absorbs any free radicals and polymers, thereby allowing the reuse of the clean oil several more times.

Auto-oxidation is a free radical reaction involving oxygen that leads to deterioration of fats and oils which affect flavors and odors.

To detect the limit of reuse, the peroxide value is determined by using a field test kit. It is a titrimetric determination.

The peroxide value is the concentration of peroxide in an oil or fat. It is useful for assessing the extent to which spoilage has advanced. The peroxide value is defined as the amount of peroxide oxygen per 1 kilogram of fat or oil. This is expressed in units of milliequivalents. The limit for reuse is 10 milliequivalents

The good quality oil is reused, while the bad oil is mixed with the boiler fuel and burned, thereby realizing an additional savings in fuel cost.

Fish Processing Waste Water

This waste water is characterized by an extremely high organic loading, consisting of fish parts and blood.

To treat this waste, an Extended Aeration Activated Sludge Process was used to reduce the organics by biological treatment in a packaged waste treatment plant. After the biological treatment, the effluent is disinfected by Ultra Violet Radiation, followed by fine filtration and activated carbon adsorption.

After this treatment, the water can be reused in various ways, such as make-up water, boiler feed water or discharged. Effluent criteria have been consistently below 5 mg/l BOD5 , Total Suspended Solids (TSS), COD and Total Carbon (TC).

Conclusion

Although canneries have often been implicated in surface water and ocean pollution, incurring considerable fines, the technology exists to prevent this. The individual treatment systems can be implemented in modules, over a period of time.