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DEPURATION--THE NATIONAL POSTURE
Eugene T. Jensen
Public Health Service
The National Shellfish Sanitation Program, and therefore the shellfish industry is rapidly approaching--and may already have reached--a technological crossroad. refer, of course, to the growing problem of maintaining a satisfactory confidence factor in our National Program. We are particularly concerned with the sanitary quality of waters from which shellfish are harvested for food use.
When the National Shellfish Sanitation Program was established in 1925 the problems of maintaining effective sanitary control of growing areas were relatively simple. Cities were smaller, there was little recreational use of the coast--in fact much of it was inaccessible--and the problems of variable water quality associated with waste treatment was limited to a few small areas. Consequently, only a small percentage of the coastline was polluted or subject to pollution. Under these conditions it was technically and politically feasible to make sanitary evaluations of estuarine areas and to prohibit harvesting from those few areas which were not of satisfactory quality. Under these conditions a program with a high confidence factor could be maintained without undue difficulties.
In the last 15 years many factors have comb i ned to increase pressures on the sanitary quality of our coastal areas. In turn this has made it increasingly difficult to evaluate the sanitary quality of the estuaries, and to assure that shellfish would be harvested only from waters of acceptable quality. Population growth, particularly in the coastal counties, increased leisure time with great interest in beach homes and boats; and improved highways which make the coasts more accessible, all have contributed to these problems. Such problems are, of course, not limited to the shellfish program. One has only to look to the community problem of safe water supply and related controversies over recreational use of municipal water reservoirs and their tributary watersheds.
To keep our discussion in perspective we need to restate the fundamental elements of our program:
We are committed to the principle that shellfish must be as safe to eat
Shellfish is not an essential food item and consumers will not purchase
The problems of assuring the sanitary quality of coastal areas will increase
What choices do we have as program administrators at this technological juncture? Insofar as preventing the transmission of disease through shellfish, we must first make a basic choice on use of shellfish:
We will maintain a program which will permit consumers to eat shellfish
Discourage or limit the consumption of shellfish in at least some forms
If we take the first choice, we must then go to explore the problems of maintaining a consistently effective program. Can we continue to build on the present program of sanitary surveys for growing areas and patrol of closed areas or must we adopt a more sophisticated approach? Our discussions in recent months with representatives of industry and the State control agencies indicate that all have a strong preference for the first choice. They also recognize that this choice carries with it the responsibility for a control program with a high confidence factor. Assuming that this is the consensus we must then examine our present program and problems and decide if they will do the job!
Again we must make a choice between several approaches:
To maintain our present program based on surveillance of the sanitary quality of areas. This would also require an aggressive program in support of pollution prevention and pollution abatement programs including the necessary technical efforts at State and Federal levels to assure that these programs will be effective in terms of shellfish culture objectives.
2. To continue our present program based on sanitary evaluation of growing areas,
but with the additional safety factor of depuration. Such a program would be effective on a long term bas is only if accompanied by aggressive support for pollution prevention and abatement.
3. To establish shellfish reserves in areas which are not influenced by waste
disposal practices of communities, and which are denied to all recreational
To place all shellfish production on a farming basis in which environmental conditions can be controlled. This might be an open farming system, as now used by the Japanese in Hiroshima Prefecture, or a closed system such as discussed by Mr. McKernan, Director, Bureau of Commercial Fisheries, at the Oyster Institute meeting two years ago.
We must clearly understand that we cannot talk about the United States as a single unit, having identical problems. We recognize that population growth and use of the estuaries varies greatly from area to area. We also recognize that sanitation problems are species related--e.g., the surf clam is not common in the half-shell trade. In some areas and with some species of shellfish there is an urgent need for action to assure continuing satisfactory program confidence factor. However, with other species or in other areas this need may be several years away. Inevitably, this introduces an element of inequality which cannot be avoided. Everyone cannot be treated the same without being unfair to some percentage. But, we always come back to the factors of public safety, public confidence and market inter-relationships.
Let us now look briefly at these alternative courses of action:
First, we have the proposal of no change, other than aggressive and coordinated support for pollution prevention and abatement in terms of shellfish objectives. This approach has served us quite well in the past, and it is still a manageable process in most areas. But, as previously explained, we believe that this approach is rapidly becoming obsolete and that we must move rapidly to the development and adoption of new methods if we are to maintain a satisfactory confidence factor.
Second, is the proposal that areas be "reserved" for shellfish culture as they are now set aside for migratory waterfowl, military use, National Parks or recreational areas. This may be practical in a few limited areas but in most places it is already too late because of the present degree of development and public and industry pressure for multiple use of the water areas. It seems probable that these pressures will grow, rather than diminish, and the "reserves" would limit very severely the total number of acres of land avai lable to the shellfish industry, would not solve the related problems of "wild" growth and patrol, and would not solve the problem of salmonella, etc., from waterfowl or wild animals.
Third, we have the proposal that shellfish be grown only under controlled conditions--a system under which water quality problems can be more readily managed. While this concept may seem revolutionary, we need only look at the trout industry to obtain an indication of what can be done. The Japanese culture techniques, as applied in Hiroshima, is use of the same idea but under open seas conditions and the West Coast oyster industry is another variant. The extent to which such systems might be adopted by industry is difficult to predict. As pointed out by Mr. McKernan in a talk before the oyster industry the concept has great merit, but it would also pose great financial, technical and sociological problems. Of the several systems which we are considering, the proposal for "shellfish farming'' to "open seas" conditions will also run head on into the problem of multiple use of the estuaries. | doubt if the shellfish industry will be able to preserve great areas of the coast for its exclusive use.
Finally, we have the process of depuration with a general control of sanitary quality of coastal waters. It is, of course, essential to recognize that depuration is not a substitute for pollution control. Also, our other programs for evaluations of the sanitary quality of shellfish growing areas would have to be continued. The depuration process seems to offer a process whereby most of coastal areas could continue to be used for shellfish culture. It would impose no limits on how shellfish might be consumed. It would require no sweeping changes in the structure of industry. It appears to offer a reasonable level of security to the consumer, it meets the problem of wild growth, it allows multiple use of our estuaries, and it offers a product of superior organoleptic quality, and it might offer substantial savings in the construction and operating costs for sewage treatment plants in many coastal areas.
On the negative side depuration adds to the cost of handling (as compared with a product harvested for direct use), requires official agency supervision, changes in industry marketing practices, and a substantial capital investment. We admittedly do not have all the scientific information we would like to have about the process, particularly in terms of costs and design factors. Generally, however, it is our belief that adoption of the depuration process is the most practical approach to maintaining an acceptable confidence factor in the shellfish program.
We concede that there are areas in which direct harvesting can be permitted for many more years and we also recognize that there are areas in which the establishing of shellfish reserves or controlled production will produce equivalent results. But for great areas of the country we feel that a choice must soon be made between adoption of the depuration process or abandonment of the shellfish industry as it now exists. If this is so, we must then face the questions of when, where, how and who. Where is it first needed, when will it be needed, what types of plants are needed for maximum effectiveness and efficiency, and who will pay for costs of treatment.
It is my belief that we must address ourselves to these problems rather than to debate of the relative merits of the process.
Actually the depuration process is not new. As a process, it was investigated extensively by European workers about 40 years ago and is now in wide use in many of the European countries. In fact, much of the European shellfish industry is entirely
dependent upon the process. We understand that there is no epidemiological evidence which indicates that the process has not been satisfactory from a public health standpoint even though some of the shellfish are harvested from areas which, by our standards, would be classified quite heavily polluted.
We in Public Health Service have been very interested in learning more of the European experiences. Two years ago a field team was sent to Europe to gather firsthand information on this process and on their administrative experiences. We had anticipated that this report would have been completed and available for your study well in advance of this meeting. The prolonged hospitalization of one of the investigators disrupted this schedule; however, we anticipate it will be completed and available within the next few months. In addition, there has been considerable experience with the process both in the United States and in Canada. Many of you are familiar with the Newburyport plant which has been operated by the Massachusetts State Department of Health for many years. In addition, a commercial plant is now in operation in Maine, and a second commercial plant has been established in Florida. Many of you are also familiar with the investigation of the process made by several of the States and by the Canadian agencies. Much of this experience will be summarized in the following reports from the States and by Mr. C. B. Kelly representing the Public Health Service shellfish research program. I think you will agree that some real progress has been made and that further progress can be expected in the near future.
In my opinion we are quite safe in assuming that both the effectiveness and economics of depuration can be improved through research and development effects. However, I do not think we should let our imperfect knowledge stand as a barrier to early--in some areas immediate--adoption of the process.
In summary, it is our recommendation that the Workshop endorse the following concepts if shellfish are to be used as food:
1. That a satisfactory confidence factor is necessary to protect the health
of the consumers and to assure their continued acceptance of the product.
2. That in many areas the problems of assuring continuous high sanitary quality
of shellfish areas are such that it is becoming exceedingly difficult to
3. That the National Shellfish Sanitation Program be conducted at programs
at a level which will assure satisfactory confidence factors.
4. Encourage continuing research programs into depuration processes and any
other techniques which would help to assure the sanitary quality of shellfish.
PRESENT STATUS OF DEPURATION IN FLORIDA
Florida, with approximately 8,000 miles of shoreline, has many acres of actual or potential water bottoms suitable for shellfish culture. Due to price and production fluctuation, it is hard to approximate the economic value of the shellfish yield in Florida, but a rough estimate would place the State-wide industry at 1.5 to 2.0 million dollars annually.
Florida's oyster industry is largely centered at Apalachicola, but other areas of production exist in the State's many estuaries. In the past, most of Florida's leading estuaries supported a thriving shellfish industry. However, many of these areas have been rendered unproductive largely due to sewage pollution and not because of any actual lack of water bottoms suitable for shellfish production.
One of the most important problems of our shellfish industry is to make oystering a reliable source of income year in and year out. Partly because the production areas are so scattered and the miles between areas so great, it is desirable that each area be self-sustaining. In order to have a reliable supply of marketable shellfish in most, if not all of the areas, the pollution problem must be dealt with. An effective control of pollution itself is desirable but not always possible. Depuration or cleansing of shellfish from marginal or polluted waters could be a possible solution to this dilemma.
The Florida Board of Conservation Marine Laboratory has been testing depuration methods for approximately one year. With the cooperation of Bay Seafoods, Inc. of Palmetto, Florida, a series of tests was conducted to check depuration technique and methods. This particular phase has been terminated, but perhaps a brief discussion of that work would be in order.
The physical structure of the plant consisted basically of three parts: the holding tank, the sterilization unit, and the circulating system.
The holding tank was constructed of 3/4-inch marina plywood coated with epoxy resin. The dimensions were 16 ft. long x 8 ft. wide x 4 ft. deep. It had a maximum capacity of about 3,800 gallons, but the experimental volumes used ranged from 1,500 to 2,000 gallons.
The sterilizing unit measured 30 inches wide x 9 ft. long and housed six 30watt germicidal lamps. The height of the lamps was varied during the test. The bottom of the sterilizer was constructed of corrugated plastic to give greater irregularity to the water and afford better killing power.
The circulating system contained a 1/2-HP electric pump, one 1/2-inch PVC plumbing and a diatomaceous earth filter of the swimming pool type. The water was drawn directly from the bay and adjusted for salinity with fresh well water. Aeration was accomplished by the use of baffles between the sterilizing unit and the holding tank.
Coliform counts of the water and also the meats were used to evaluate the system. Checks were made using two different species--the American Oyster (Crassostrea virginica) and the Rangia Clam (Rangia cuneata). Up to 40 bushels of clams were used in these tests.