2.1. Key areas to consider Before we can assess the sources of product loss and therefore pollution, we must understand the process. The basic process for producing fishmeal is outlined in the attached flow diagram (Figure 4). This is a generic flow diagram and I am sure it will vary for each plant in Peru. When we made our assessment of the Pisco plants, we started with this diagram and a two-page questionnaire. Based on the answers in the questionnaire, we modified the flow diagram for each plant. The interview took about two hours at each plant. The questionnaire that we used is shown in Figure 5. The diagram and questionnaire are key elements of a pollution prevention program and are necessary for doing an assessment of the facility.
Based on the interview, a tour of the plant and an evaluation of the flow diagram, we found that there were four key areas to consider in the Peruvian fishmeal industry:
2.1.1. Raw material quality
Raw material spoilage means economic losses because it:
You cannot make a prime or high quality product if the raw material is not fresh. You cannot expect to recover the optimum yield from the raw material if solids and oil are going out in the vessel bilge, in the pumpwater water, in the blood water and in the stickwater if it is not evaporated. If the fish are stale, the stickwater will be stale and the concentrate added back on the presscake will reduce the quality of the fishmeal further. The volatiles from the stickwater will come out and enter the condensate water raising the BOD}5} and when the presscake is dried the volatiles in the fish will be discharged to the atmosphere causing odors. Therefore your first line of defense is fresh raw material. Reducing the storage temperature of the fish by only 5-6 centigrades will reduce the biochemical reactions that cause spoilage by 50% and extend the storage time by 100%. Figure 8.
When the fishing vessels arrive at the unloading stations, they are pumped to the factory with wet pumps that were designed specifically for the Peruvian situation, that is distances of up to 1500 meters with as much as a 15 meter rise, large pumping volume (200 mt) in short periods of time to get the vessels back on the fishing grounds, and free Pacific Ocean water. The ratio of water to fish was not important because it was discharged back overboard, the major criteria was speed. The unloading operation probably damages the fish further causing solids and oil to be lost and discharged overboard. When there is a large concentration of factories on the same small body of water (harbor or bay) then the level of pollution in that bay, especially if the tidal flow is poor is devastating. In fact, if you are all unloading at the same time then the chances are good that you are using your neighbor's effluent in the seawater you used to unload your fish. That much discharge into the harbor attracts sea birds and probably also leads to salmonella contamination in the water which then comes into the factory with the fish.
Bloodwater is produced on the fishing vessel when the catch is stored during the return trip to the factory and after the fish have been unloaded into the raw bins of the plant. Blood water results from bacterial activity and autolysis (self digestion) from the enzymes in the fish gut and from what the fish are eating. This reaction increases with temperature and both protein and oil are lost as a result. Once the fish reach the raw holding bins they continue to deteriorate. Liquids (oil and water with solids) continue to leach out of the fish. If not processed, valuable product is lost. A report from Chile states that the solids in the bloodwater increased from 5% after 1 hour storage to 14.5% after 21.5 hours of storage. A Scandinavian report indicated that the bloodwater losses could amount to 10-15% of the original weight of the raw material.
Figure 9. The bloodwater is produced by the decomposition of the fish and is released by the pressure that they undergo in storage. If the produced bloodwater is not allowed to escape from the fish, it will accelerate the decomposition process and produce more bloodwater.Stickwater volume and content changes with the condition and age of the fish. As the fish get older, more of the protein is broken down into water soluble fractions and oil is released. The ultimate end product is all liquid with some bones. Every factory should be equipped with a stickwater plant. Stickwater can represent 60% of the weight of the raw material from fresh fish and even more from older fish. If the stickwater is not recovered then valuable product is lost and the volumen of effluent from that factory would overwhelm the receiving body of water. It is not possible to recover the blood water fraction without the stickwater plant.
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