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Multifunctional Shellfish Refining Plant Operating in a Closed Containment System and Inventory Management Strategy for Safety Certification

Table of contents

Objective:

We aim to develop and implement a closed circuit system in the construction and operation of a NB multifunctional shellfish storage plant operating in a closed circuit.

Background

In 2001, for the first time, the oyster industry on the eastern coast of NB faced harvesting area closures as a result of domoic acid. The closure lasted two weeks, during which time the company was unable to supply its clients. This negatively affected the company's credibility in terms of its ability to supply its markets on a continual basis, which consequently affected its sales volume trends. Had the situation lasted a month, it would have had catastrophic results. In that case, we would have had to produce inventories of stored oysters to be able to continue regularly supplying oysters to the markets and thereby protect these clients from the environmental hardships faced by this industry on a regular basis.

The development of a multifunctional oyster plant (wet storage, decontamination and refining) that operates in a closed circuit is a priority for Maison BeauSoleil Inc. The New Brunswick oyster industry is in full expansion and company sales are growing, but it faces supply and safety issues. Building such a facility is one of the most important criterion of the product safety assurance strategy that the company seeks to implement. This type of development should also help strengthen supply during certain critical periods related to ice break-up, overcome supply difficulties and the risks associated with domoic acid, take advantage of oyster and other shellfish marketing opportunities in other areas closed off from shellfish harvesting, refine (clean and sand) bottom oysters and other shellfish, while ensuring the operation's profitability. The design should also take into account the possibility of storing scallops in case the company decides it would like to diversify its production. Building this type of plant could allow the company to address constraints that have curbed expansion of its European markets.

The company currently manages its supply at the start of winter (ice forming) and in spring (ice break-up) by taking advantage of the geographical distribution of its promoters' shellfish operations. SaLant Aquaculture Inc. operates in Neguac Bay at the mouth of the Miramichi River, while Aquaculture Acadienne Ltée operates further south in Richibucto Harbour. This allows for relatively efficient management based on when the ice starts to form, even though certain difficulties did emerge in the past two years, and this at a time when sales volumes were fairly low. Supplying oysters became increasingly difficult. It became increasingly difficult to efficiently manage the supply of oysters then and the company was unable to adequately supply its end-of-season markets during the past two years. Add to this the anticipated sales volumes over the next few years and possible expansion of the European market, which primarily focuses on the holiday period at year-end.

Profitability for this type of infrastructure depends on the extent of its use. Using it for decontamination and storage purposes during critical periods does not justify the use of this type of infrastructure on a regular basis. However, its usage could be maximized by using it to decontaminate bottom living oysters from areas closed to shellfish harvesting and to refine (cleaning, sand removal) bottom living oysters. It would also be relevant to examine market diversification possibilities, namely, decontaminating soft-shell crabs from areas closed to shellfish harvesting and storing and conditioning European oysters, sea scallops and bay scallops.

Maison BeauSoleil Inc. had considered building an infrastructure similar to the region's shellfish storage plants that operate in an open circuit. However, it encountered water supply problems because of the region's topography. The plant would have had to be situated roughly a kilometre from the coast to have suitable conditions for inlet installation. The seabed slope in Neguac Bay is very gradual and the bottom muddy. Placing the water inlet too close to the coast would also have posed bacteriological contamination risks and it could have been damaged by ice. The company was also not sheltered from the risks associated with PSP toxins. It also wanted to minimize the risk of introducing invasive species into Neguac Bay's coastal ecosystem. Pumping well water was not an option because of the costs involved, the uncertainty of whether salt water patches would be available near the plant and the high concentrations of manganese in the underground salt water patches. So the company decided that the most appropriate solution would be a storage system operating in a closed circuit; this would also fall more in line with its environmental impact philosophy. Given the fact that closed circuit technology is not used in North America for shellfish storage, it was difficult to find local experts to implement this type of infrastructure. Although its use is fairly recent in France, the closed circuit shellfish storage system elicited interest. It serves primarily as a storage facility for processing purposes and did not address issues related to shellfish conditioning and decontamination. Nonetheless, production techniques in a closed circuit have been perfected for fish farming. But needs related to biological results and economic dynamics are not always the same. That's why the company wanted to put together a team of local specialists with knowledge of pisciculture-related fields, while continuing to gather outside knowledge. The multifunctional storage plant opened in 2009, a little over a year after construction began. This report presents the steps leading up to the project's completion.

Design Development

The development of the multifunctional closed circuit plant design started with an analysis of wastewater treatment in fish farms and ways to adapt those technologies to meet our needs. That was followed by a substantive mission to France to evaluate water treatment systems used by the shellfish industry. Specifically, the mission's purpose was to learn more about a new aeration and skimming technology, perfected and patented by IFREMER1: the SKIM wastewater treatment system, which is used increasingly within the aquaculture sector to treat wastewater. The SKIM system appears to have great potential and could easily be integrated into recirculation systems for shellfish storage and conditioning; in addition it requires less maintenance than other systems. After extensive review of water treatment approaches in fish and shellfish recirculation and wastewater treatment systems, the company decided to work towards implementing the SKIM system for water treatment into its multifunctional shellfish storage and conditioning plant. This type of technology could effectively meet the treatment requirements of wastewater produced by shellfish in closed circuit storage conditions considering its simple operation and maintenance, lower purchase, operating and maintenance costs compared to other devices, and lower temperature operating capacity. Although the SKIM system could have operational limits at high temperatures in the context of decontamination and shellfish farming, it seems to have enough capacity for shellfish conditioning with a shorter treatment time and lower storage temperature compared to that required for decontamination.

Skimming involves creating a foam rich in nitrogen compounds but that may contain a considerable amount of particles. The process consists of forming bubbles inside a vent, thus imitating a natural process seen in sea water. Foam is evacuated through the top of the vent. Filtration is the primary function carried out by the SKIM. The system works efficiently because of the air-water exchange created by micro-bubbling under pressure and a filtering capacity to the smallest micron. All suspended solids, even micro-organisms (bacteria) are trapped through the thousands of filters formed by micro-bubbling. It uses a cyclonic back-flow hydraulic system. The foam is recycled in an upper condensation chamber, and the water drains out through the bottom.SKIM’s performance would surpass those of regular systems (biofilters, UV and ozone filters). In theory, it replaces a hydraulic network, pump, water circulator, oxygenator, sand filter, biofilter, UV and ozone disinfection systems. It is also easy to install, easier to maintain, consumes little electricity, and is a natural process.

The new shellfish holding tank storage infrastructures proposed by Maison BeauSoleil Inc. includes a raw material reception area, dry storage areas, wet storage holding tanks area, water treatment area and processing (oyster washing) area. It is also possible to assess tank depths relative to the plant foundation. Many changes had to be made to the original plans to reflect the production objectives, knowledge acquisition specifically related to storage technology, conditioning and cultivation of living organisms in a closed system.

The storage tank area measures 15.6 x 15 metres for a 234 m2 surface area. It contains four storage tanks installed lengthwise and arranged in such a way to allow for use of a lift loader. The two tanks along the walls on either side extend 18.45 metres and allow for the use of 36 storage tanks stacked three rows high. The centre tanks are slightly shorter so that the lift loader can access both aisles. The 14.85 metre length allows for the use of 30 tanks each. The internal measurements of the storage area tanks are 18.45 x 1.2 x 2.4 and 14.85 x 1.2 x 2.4 metres respectively. The two tank sizes have respective capacities of 34,300 and 30,700 litres of water. An additional 36,000-litre water reserve was built underground, alongside the plant.

A deeper section was built into the end of each tank to allow the SKIM units to be installed and operated. They are 3 metres deep compared to 2.4 metres for the storage tank section, which means the SKIM units can be left in place whether the tanks are empty or operating at full capacity.

The tank sections where the SKIM units are installed, or the wastewater treatment area, is separated from the storage area by a wall because of humidity in the storage area, gas exchanges, and especially the ammonia level. With a surface area of 126 m2, the water treatment area also houses an ozonation system, in case the SKIM system does not perform well enough to decontaminate the shellfish, and a refrigeration unit. The space is also used as a storage area for Dark Sea trays and holding tanks.

It is crucial that the water circulate towards the treatment units so that the SKIM units work properly. For that reason, the tank dimensions had to be reviewed to promote the circulation of water, transportation of sediment and other suspended solids towards the water treatment system and ensure there were no stagnant water areas inside the circuit. Initial plans included a side roundabout circulation to funnel wastewater and suspended solids towards the SKIM units. However, the tank configuration had to be reconfigured after the construction engineer raised doubts about the support capacity of the sections of suspended floor surrounding the tanks and the load, including the anticipated volumes of oysters and water in the holding tanks.

Since the new tank configuration made it difficult to install a central panel to create unidirectional circulation towards the water treatment units, they were replaced by strategically placed pumps. The depth of the tanks along with the pumping action creates a roundabout movement of water from top to bottom that helps transport the particles most likely to settle on the bottom towards the water treatment system. An aeration system is built into each pumping unit and helps optimize gas exchanges (oxygen, ammonia).

One of the design principles proposed by Maison BeauSoleil Inc. for storage that justifies a lower water treatment capacity is that shellfish become dormant when water temperatures fall below 5°C. Consequently, their levels of metabolic activity are much lower than normal. As a result, they require much less oxygen and will produce much less metabolic gas. This results in much less restrictive demands of the SKIM treatment system, which works just as well at low temperatures as high ones in terms of eliminating suspended solids -including sediments, bacteria, viruses and others.

A cooling mechanism was built into the system to keep the oysters at temperatures below 5°C. With a 20-tonne capacity, the mechanism includes a refrigeration unit and heat exchanger. The heat exchanger, made from titanium which is more stable in salt water, was designed to be used in a series of tanks or individually. The heating and cooling mechanism is also linked to the water treatment section by a connection that can be opened or closed depending on requirements. Each tank can therefore operate in a series or individually should the company ever decide to use one or two tanks for conditioning and decontamination purposes. The tanks, just like the holding tanks (see Section II on holding tanks), were designed to minimize the risks of cross contamination. The edges were built 50 cm from the floor so that any possible water overflow can run from one tank to another.

A dry storage area was set up so that shellfish could be kept cool before being transferred to holding tanks or the sea or to meet daily production requirements. The storage area is also an important part of shellfish inventory management in accordance with the company's strategy targeting product safety as presented in Section III (Shellfish Safety Assurance Program).

Approach

The start of construction was pushed back several times as a result of delays obtaining the various permits. Government agencies needed the finalized plans in order to reach a decision about the possible environmental impact, while the innovative nature of the project made it difficult to finalize project details. Construction could not begin until the end of October 2008 after government agencies had determined that the construction and operation of a storage plant operating in a closed circuit had little risk of negatively impacting the environment. Additional delays were encountered as a result of challenging construction conditions. Because of the depth of the tanks and the late work period, the contractor encountered soil quality problems, freezing and thawing, water infiltration and then freezing and snow coverage. It was decided that such conditions could lead to instability in terms of the floor and have undermined the integrity of the water holding tanks. Infill work, pouring the foundation and raising the structure were eventually put off until spring, when the ground had dried out and stabilized. Further delays were incurred to install the water treatment equipment, which is a European technology that is compliant with Canadian electricity standards. Consequently, wiring from the various pieces of equipment had to be replaced and a new electrical panel had to be developed. The delivery of the heat exchanger was delayed, which further delayed installation of the piping network. The plant only became operational at the end of November 2009, just in time for the company to build up its winter inventories.

Operational Set-Up

Tanks were filled using a 3,800-litre tanker truck. The tanker fills up at the lower Neguac docks on the far side of the riprap that serves as the breakwater. There is no activity on the dock at that time of year. Water samples were taken at the dock for water safety analysis and at the pumping site to ensure the sanitary quality of the water. Nevertheless, although no signs of bacteriological contamination were noted in the samples, the system ran for a few days before becoming fully operational to ensure the tank water was completely safe. A final series of samples was taken from the tanks before they became operational.

Operating Parameters - Scientific Monitoring

The first trials ran from October 19 to November 20, even though the refrigeration system was not yet operational, which allowed us to evaluate the oyster conditioning procedure. The temperature was slightly higher than conditions under which the company plans to work for oyster conditioning. Temperatures in tank no. 1 varied from 10 to 16°C during the trial period, while target temperatures for oyster conditioning are usually between 10 and 12°C. A series of 10 samples was taken from every batch of oysters before they were stored in holding tanks the following day. However, only three batches showed signs of bacteriological contamination and the levels of contamination were relatively low (20, 48 and 48 MPN), which is not a good indication of the system's conditioning capacity. No signs of fecal coliforms were noted in the samples after a 24-hour storage period. The differences are not significant, in light of contamination rates and the number of contaminated batches. Moreover, water temperatures were higher than those the company plans on using for oyster conditioning. However, signs of mortality were apparent in the conditioning trials control group after one month of storage. The tank was at full capacity when the signs of mortality were observed, which suggests that the system might have reached its maximum capacity for that temperature.

Approximately 100 lbs of lobster were also stored in a holding tank at the end of the trial period and grown for 2 weeks. High mortality rates were observed for the lobster, which suggests that a significant amount of ammonia gas had been produced. The systems might have surpassed their maximum support capacity for that temperature regime (higher than 12°C). The oxygen level had dropped by 20-25% when the tank was used at full capacity. Unfortunately, we were unable to monitor changes in the ammonia level during that period because the probe malfuntioned. Since the oxygen probe levels also showed inconsistencies, two new probes were ordered for summer monitoring due to more restrictive operational conditions and the possibility that two tanks would need to be used for oyster conditioning. However, given the results from the first trials, we anticipate conclusive results. The first signs of mortality were not observed until after one month of the system operating at extreme conditions (temperature and load level). According to the company that markets the SKIM, one unit can process 12 tonnes of shellfish at 10-12°C.

Temperature Monitoring

A temperature difference was noted between the various tanks and could be explained by the load levels and, consequently, by the variations in water flow in the holding tanks. The temperature difference is not excessive, however, and is within operational limits, the goal being to maintain water temperature in the tanks below 5°C. Adjustments to flow levels from each tank passing through a heat exchanger should help reduce temperature variations. The refrigeration capacity seems sufficient since water temperature in the four tanks was maintained below the target limit. Closer monitoring is nevertheless planned for the coming months to ensure that water flows are controlled and to reduce the temperature differences in each tank.

Conclusion

We were unable to complete all of the trials to validate the operation of the shellfish storage plant in terms of closed circuit product conditioning as construction work was not completed until early fall, after the period that presents considerable contamination risks. However, the facilities were used to full capacity during the winter for oyster storage. More than a million oysters were kept in storage with no signs of mortality, which proves that the system performs well enough to store oysters at low temperatures. The results of the conditioning trials, although basic and at higher temperatures than those suggested for oyster conditioning, also demonstrated the feasibility of using such an approach for shellfish conditioning and decontamination. We just need to ensure that the system does not exceed its support capacity at the temperature regime suggested for conditioning. If it does, that type of approach could be used for conditioning as long as the support capacity is not reached. That poses no problem given that the tank intended for oyster conditioning has a 24 tonne-capacity for shellfish, which represents an inventory of 400,000 oysters and greatly exceeds the company's weekly needs in summer. Reducing the load level is therefore not a problem in itself. In addition, given the innovative nature of the process, the company, for safety reasons, installed an RK2 ozonation system in case the SKIM system cannot meet the demands of the shellfish conditioning process.

Scientific monitoring is scheduled for summer 2010 in order to validate the conditioning approach and results according to holding tank position. As the water temperature in the holding tanks must be higher to facilitate an increase in the metabolic activity levels of stored shellfish, we wonder if we could standardize product conditioning by using three stacked holding tanks, or is it necessary to work with two stacked holding tanks, which would be an operational deviation in terms of time required for oyster conditioning in the top holding tanks compared to the bottom holding tanks. What would be the consequences of water quality variations (O2 and nitrate) for shellfish survival according to thermal regime?

The storage objectives are to operate at temperatures below 5°C; this involves considerable costs in electricity to lower and maintain temperature at those levels. To save energy, how would the system perform between 5 and 10°C? Despite being active, is the oyster's metabolic activity level not just as high as it is at a temperature above 10°C? The capacity of the water treatment system could be sufficient for storage at this temperature regime considering that such an approach would represent substantial savings in terms of refrigeration costs.

According to the supplier, a SKIM unit can process 24 tonnes of products at 10°C. Estimates are based on the Pacific oyster (Crassostrea gigas) while we produce the American oyster (Crassostrea virginica). Are there physiological differences between the two species? What about sea scallops, bay scallops and European oysters? How much leeway do we have, given that the shellfish would only be processed for 24 to 72 hours.

One can assume that storage at low temperature makes it possible to maintain oyster meat yields during summer due to reduced metabolic activities and spawning prevention. Is it possible to change the seasonal metabolic pattern of oysters by keeping them in winter conditions (in holding tanks) for short periods of time and then returning them to the water in cultivation conditions? If not, is it possible, using this type of approach, to significantly delay triggering spawning in order to market an oyster with high meat yields for the entire summer season? And, what about the European oyster, whose eggs develop inside the broodstock? Would it be possible to delay the development of gametes and eggs to allow for summer marketing of the European oyster?

Development and Trials of a Holding Tank Adapted to Store Shellfish in a Closed Circuit

Objective

We aimed at developing a shellfish storage tank to maximize the use of space within a closed circuit system and explore the possibilities of using one or two tanks for shellfish conditioning and decontamination.

Background

There are several types of holding tanks (large boxes) on the market for shellfish storage. Even though a subfloor and bubbler system must be added, they are well suited for storing shellfish in bulk. Using them with oysters is more problematic because cramming them can lead to erosion of their frills. Furthermore, other bulk shellfish such as bay scallops, sea scallops and clams cannot be stored in this type of holding tank due to the fragility of their shells. Maison BeauSoleil Inc. wanted a structure that made it possible to store oysters and other shellfish in the smallest containers possible for the holding tanks. Handling smaller amounts of shellfish makes the task less physically awkward for workers since shellfish must be handled manually, in addition to minimizing frill loss and reducing risk of crushing the shells of more fragile shellfish. Holding tanks currently available on the market are not adapted for that type of use, however. For example, the inner dimensions of a Xactic box are 109.4 x 95 x 97.5 cm for a 1,013.1-litre volume. Containers used by the company for handling oysters measure 60 x 40 x 17 cm. It would therefore be possible to store 18 containers in a Xactic box. The fill level would only be 69.3%. That means it would take 185 Xactic boxes to store one million oysters compared to 76 for the new holding tanks developed by the company. Using that type of holding tank also means that more water would be needed, given that 30.7% of the holding tank volume would be from water alone, which should consequently increase pumping and refrigeration costs in addition to requiring a larger water reserve. Developing a holding tank to optimize the use of space is still problematic because of the size of the existing shellfish boxes. The holding tanks would have shortcomings in terms of water circulation because they would not be able to be loaded evenly. Stagnant water could occur, which would have serious consequences on shellfish quality and survival in storage.

As a result of issues related to water supply, quality consistency and the environment (minimize risks of introducing new species), the company recommends operating a closed circuit system. This approach involves the restriction of water circulation throughout the system to minimize water loss. The control of water circulation throughout the system would become even more critical if the company ever decides to use a series of holding tanks or one tank for conditioning and decontaminating oysters and other shellfish. Even if the tanks are designed to minimize cross-contamination between tanks, the company would be sure to further reduce those risks while minimizing water loss.

Holding Tank Development and Trials

An initial meeting with representatives from the manufacturing companies that make rotational molding and plastic containers (president and engineer), Maison BeauSoleil (general manager and one co-owner) and even the resource specialist helped to understand the company's needs and expectations in terms of holding tank operational criteria. Follow-up meetings further defined features of the holding tanks and their operation. The points raised included, but were not limited to:

Internal storage structures

Dark Sea trays are the preferred shellfish support structures in holding tanks; they can be used to transfer oysters directly from culture sites to holding tank culture sites and vice versa, without additional handling. Their square 50 x 50 cm size, coupled with their truncated edges, also allow for better space management inside the holding tanks. With their shape (truncated edges with a hole in the centre), it may also be possible to develop a device to handle them (remove and place them in the holding tanks) mechanically.

Need for an insulated holding tank

The storage area is insulated because the water needs to be kept refrigerated. But the holding tanks do not need to be insulated, which would involve additional unjustifiable costs.

Storage capacity

The internal dimensions should allow for storage of 4 columns of 10 Dark Sea trays (2 rows of 2 columns).

The holding tanks should be strong enough to be stacked 3-4 rows high. With the amount of space available above the tanks in the storage area and the columns of 10 Dark Sea trays, storage tanks will actually have to be stacked three rows high. The holding tank design should allow for optimal use of the internal space. The internal dimensions must therefore be based on those of the Dark Sea trays.

Internal dimensions

Allowances should be made for extra space on the sides to make it easier to place and remove the rows of trays. However, too much space could affect water circulation inside the holding tanks and take up additional unwarranted space in the plant. The design of the Dark Sea trays with their truncated edges lends itself well to such an approach.

Spaces of still water

The holding tanks should be designed to minimize stagnant water and to promote optimal water circulation inside the trays of oysters and other shellfish.

Water quality inside the holding tanks

The holding tanks should be designed in such a way that water quality is as constant as possible between the top and bottom tanks. In the existing holding tanks, water flows through the oysters from top to bottom, meaning that shellfish in the bottom tanks would be fed by water that will have passed through oysters in the top 2-3 holding tanks. This approach means increased water flow to attempt to maintain an acceptable water quality (nitrate, O2) and, consequently, additional pumping costs. This would be acceptable for storage at low temperatures, but may be problematic at the higher temperatures used for shellfish conditioning.

Closed circuit operation

The stacked holding tanks must minimize water loss when in operation since water is continuously recycled and, as a result, water volume and water loss are important operational constraints.

Sediment/mud

Excessive amounts of mud could negatively affect water treatment system functioning in addition to water quality (nitrate, O2) and the survival and shelf life of stored oysters. Therefore, holding tanks should be designed to retain the maximum amount of mud inside without affecting the oysters.

Cross-contamination

The company plans to use one, possibly two rows of tanks for shellfish conditioning and decontamination. Operating with stacked holding tanks should therefore help minimize water loss and consequently the risks of cross-contamination with other rows of holding tanks. In existing plants, storage areas used for shellfish decontamination must be separated from storage areas used for processing to avoid cross-contamination risks.

Ergonomic aspects

The holding tanks should allow for efficient handling of stored oysters.

Questions were also raised about the volumes of oysters stored per holding tank and the weight of the tanks, which could influence their design. How will the holding tanks be handled? How high is the building and how big is the work space, including the inlet? How will the holding tanks be spread out and what are the dimensions of the storage and water treatment tanks? And so on... The discussions eventually focused on the possibility of adapting the existing storage structures, namely, the Xactic boxes. The company suggested increasing the size of the Xactic boxes and integrating a system to bring the water back up on the inside of the tank side walls. However, the approach was felt to be unacceptable because inserting overflow mechanisms into the side walls would have involved another tank size increase and the risk that the system could not withstand the anticipated water volumes, which could lead to overflow and water loss. It was suggested that efforts focus on an approach to allow tanks to be emptied from the bottom through a series of openings in the floor of the tanks.

An initial series of drawings was prepared by the plastics container manufacturer and was reviewed by Maison BeauSoleil staff and the resource specialist. A second work session allowed him to refine tank drawings using the proposed recommendations to facilitate the storage of trays in rows, integrate a new holding tank overflow system and bottom draining and circulation system. The engineer emphasized the need for a small inside corner so that holding tanks could be removed from the mold, which is in line with the company's desire for a space between tray columns inside the holding tanks. The initial holding tank sketches proposed by the plastics container manufacturer show the four openings on the bottom, two overflows in opposite top corners, a ledge to prevent spills, stands on the bottom so a subfloor could be installed and a V-shape on the bottom. The overflows and ledges were retained, as were the water drains in the floor, although their position needed to be reconsidered. Subfloor supports were rejected because of the high manufacturing cost of the screened plates and additional handling costs. Reserves were suggested for the side design, and the engineer suggested that ribs would help reinforce them.

The second series of sketches proposed for the holding tanks shows the first subfloor system proposed that was replaced by a support mechanism for the tray columns built into the bottom of the tanks. Floor drains were repositioned to the centre of the Dark Sea trays. The bottom and sides of the holding tanks were also reconsidered to address comments about the importance of their sturdiness. Ribs were added on the sides and bottom. An extra support was added to the tank bottoms.

The drawing details were finalized in the third and fourth sessions. Specifically, the size, drain details and bottom configuration were reviewed, in addition to a mechanism to collect excess mud at the bottom of the tanks.

The internal dimensions of the holding tanks are 50.5 x 50.5 x 43" and can accommodate 4 columns of 10 or 11 Dark Sea trays.

The external dimensions are 55.5 x 55.5 x 46.5" and include a base for use with a lift loader.

The configuration of the sides was reviewed to ensure that holding tanks would support full tanks of oysters stacked three columns high. The walls have five ribs to reinforce the sides.

The floor configuration was designed to support the columns of trays while separating them from the bottom without having to use a subfloor. The 5-cm space between the trays and the bottom provides better water circulation around the trays. This also made it possible to reinforce the bottom. A fault was added to the centre of the tanks to reinforce the bottom like the ribs.

The drains in the tank floors are used to transfer water from one tank to the tank below.

Two overflows are situated in opposite corners of the tanks and are used to funnel excess water to the tank below.

The edges are three centimetres higher than the overflows and work to prevent water overflows and minimize water losses.

The mud retaining mechanisms were built by inserting a pipe into the floor drains. The exit pipes located two centimetres above the floor let water flow through while heavier mud settles on the bottom.

Once the drawings were checked, the manufacturer began making the mold for the tanks' rotational molding. However, the first molding trials were inconclusive because there were problems with plastic distribution and curing (cooking). After changes were made to the mold, a series of six holding tanks was constructed for trials, specifically, to check their integrity when filled with water and stacked three columns high. To do so, two columns of three holding tanks were filled with water and left that way for two weeks. No distortion was noted during the trials. A more in-depth analysis of the holding tanks was done and it confirmed the internal integrity since there was no water flow between the walls of the tanks. Maison BeauSoleil Inc. concluded that the holding tanks were strong enough for its shellfish storage activities.

Based on analyses, 36 holding tanks were constructed for trials in the plant and to check the functioning of the holding tanks and water treatment tanks. Making the holding tanks operational was not easy because it was difficult to find an acceptable compromise between drain size and flow. Holding tanks operate on the principle that the volume of water is greater than the ability of the bottom drains. As long as there is a water yield, it is possible to fill the tanks and generate a surplus of water yields (overflow). The pipes (overflow), situated at the top of the holding tanks on opposite sides, work to prevent excess water from overflowing from the tanks to the floor by bringing it to the tank directly below them. Since the molds manufacturer could not accurately determine the size of the opening because of the oyster factor in the tanks, a decision was made to make a hole large enough for a 2.5 cm pipe. In theory, it was sufficient to insert a flow restrictor inside the floor drains to adjust the water flow. Many trials were needed before the size of the drain was set at 9.4 cm. The floor drain combined with the overflows make it possible to pass approximately 60% new water (according to the volumes of stored oysters) directly into the tank just below and, as a result, increase the proportion of first-pass water (having only passed through shellfish in one tank) in the lower tanks and consequently maintain relatively stable water quality in the columns of tanks. This approach is considered particularly important for oyster conditioning and possible decontamination.

After flow control mechanisms were installed in the floor drains and the flows were configured, all the holding tanks were filled with oysters and stacked on top of a water tank. However, after two weeks of operation, we noticed that the exterior walls of the lower tanks bulged. Signs of water flow had also been noted on the floor next to the tanks. All of the water was transferred to another container and each tank was visually inspected by the manufacturer for bulging and leakage. The leakage seemed to be limited to the lower tanks. A more extensive analysis was conducted by the mold designer, who determined the sides were the problem and that there were weak points along the bottom side ribs. There are no major operational constraints with the integrity of the holding tanks when they are resting equally on their entire base, as when they are installed on top of another tank or on the floor. However, that is not the case for the bottom tanks installed on top of the water storage tanks. The force exerted on the walls is much greater when the tanks are on the water tanks and only two sides are supporting the load. The tension exerted by the weight caused the ribs to break on the bottom, which reduced the tanks' resistance and led to the bulging walls. Structuring foam was injected between the walls to improve their support capacity. The life span of this first series of holding tanks was lowered by the tank manufacturing company engineer from 10 years to 5 years. According to the engineer, there would have been no problems had the tanks been installed the other way around on the water tanks. However, the company's floor manager says that because of the way the tanks are shaped, they must be arranged that way so that they can be moved with the lift loader.

Errors in the mold were corrected to ensure there would be sufficient space between the side ribs and tank base. Structuring foam was also injected between the walls to improve the support capacity of the tanks for plant operations.

Conclusions

The tanks developed by Maison BeauSoleil Inc. in partnership with Everest Plastik Inc. can be used to store 44 Dark Sea trays. It is possible to store 250 oysters per tray for a capacity of 11,000 oysters per holding tank. The plant's storage capacity would be 1.45-million oysters. However, in low-temperature conditions, it might be possible to increase capacity to 1.7-million cocktail oysters, considering that the densities could be increased to 300 oysters per tray and 13,200 per tank since the oysters are dormant and only water quality need be maintained.

After problems installing the flow control mechanism in the tank bottoms, the first trials were more than conclusive. The tanks are easy to load with Dark Sea trays. Controlling water flow through bottom openings and overflows helps water circulate efficiently through the oysters; no overflows were noted.

Using columns of trays also made it possible to handle them using a lift loader. Finally, the use of Dark Sea trays also facilitated efficient transfer from the plant to at-sea storage sites and vice versa.

Shellfish Safety Assurance Program

Objectives:

Since 2007, Maison BeauSoleil Inc. has been working at adopting an oyster harvesting and inventory strategy. The project was to develop, validate and implement an approach that would reduce or eliminate potential risks of consuming contaminated oysters while being somewhat flexible with Fish Inspection Regulations related to shellfish harvesting.

Background

Shippagan Harbour was closed in 2002, apparently, as a result of the city's work on the wastewater treatment facilities. Nobody, either at the municipal or government agency levels, felt it necessary to inform the shellfish growers. The Dugas oyster farm (a regional producer) had to assume the oyster returns and losses during the incident. The consequences would have been even more damaging for Maison BeauSoleil Inc. given its marketing strategy, which promotes a premier trademark for its oysters. If a municipality can allow itself this type of spillage without risk of reprimand, what of illicit dumping, defective individual sewer systems and other issues?

The oyster industry regularly faces stoppages to its harvesting and marketing activities as a result of shellfish area closures resulting from bacteriological contamination. According to Environment Canada and the Canadian Food Inspection Agency, the use of floating bags in specific areas could also have played a role. Although some changes to the culture structure helped improve the situation by limiting seabird access to floating bags and OysterGro cages (Comeau et al 20082), it is impossible to completely stop birds from using the culture structures and thereby eliminate risks of bacteriological contamination for oysters farmed on surface-level structures. For that reason, oysters being cultivated in floating bags and other surface structures must be conditioned for 15 days (with sampling) or 30 days (without sampling) before being shipped to the plant. Oyster farmers must, in partnership with a processing plant, adhere to a safety assurance program that specifies oyster conditioning procedures. Implementing and managing such an agreement is the responsibility of the processing plant.

Maison BeauSoleil Inc., aware of the risks that consuming unsanitary products has on human health and its responsibility relative to its supplier agreement, would like to ensure its product is safe and respect its commitment to its suppliers. That is why it built a microbiology laboratory in 2007 to be able to meet the sampling requirements of this initiative. This type of quality assurance involves considerable financial constraints for the company since the oysters it receives from its suppliers must be paid for upon delivery; it must then wait between 15 and 30 days to market them and up to 30 days to receive payment. In addition, the company is not sheltered from closures due to PSP toxins, and that, combined with the prolonged conditioning period, could make it more difficult to regularly supply its markets. There is also a risk that some producers are not respecting the conditioning protocol (shellfish safety assurance program). Therefore, aware of its responsibility to monitor human health risks and given its intermediary role between oyster production and consumption, Maison BeauSoleil Inc. would like to ensure it has closer and more targeted, but also more flexible control of the oyster safety management process it plans to market. Construction of a multifunctional shellfish storage infrastructure operating in a closed circuit, combined with its microbiology laboratory, is one key element in its approach, which aims to certify the safety of its product by giving the company the ability to condition and possibly decontaminate its shellfish. Aware of the costs of building and operating such an infrastructure, the company is looking to replace the decontamination process in its plant with a conditioning procedure. This approach would also benefit its marketing strategy; "decontaminated product" would no longer need to be written on its labels.

The oyster safety assurance programs in place between the plant and its suppliers seek to ensure that no oysters cultivated in suspended bags and OysterGro cages are marketed without being conditioned for at least 15 days, in accordance with Canadian Food Inspection Agency requirements. Dark Sea trays are not considered in this approach because of the low risk of contamination for oysters cultivated in those structures. Risks of bacteriological contamination are low for those structures because they are not suspended at the surface but instead used in deeper water further from the coasts and therefore away from potential sources of contamination. Oysters cultivated in floating bags or OysterGro cages are not necessarily contaminated, but they run the risk of contamination, which justifies the conditioning procedure. It would be possible to more closely define the risks of bacteriological contamination if we knew more about the operational production sites associated with a management approach and a sampling plan that would target the most at-risk batches. The Canadian Food Inspection Agency considers that all oysters cultivated in suspended structures pose a safety risk and must be properly conditioned for at least 15 days with sampling and 30 days without sampling, unless an acceptable risk management approach is developed.

Maison BeauSoleil Inc. is attempting to shorten the pre-marketing period for oysters raised in suspension by defining the relationship between contamination risks and the use of shellfish areas by seabirds and other human activities. A holding tank conditioning procedure could enable them not only to respect government standards for product safety, but also to lower them beyond measurable levels. With this approach, sectors that are less at-risk might require reduced conditioning requirements than those more at-risk. For example, a batch cultivated in an area with a low incidence of seabirds on its structures and less human activity would pose less of a risk than a batch cultivated in an area with a high incidence of seabirds on its structures, and each batch would be dealt with accordingly.

Methodology

In 2007, a sampling program was implemented for all incoming oyster batches in order to create a database that could help determine contamination risk levels according to time of year, region and supplier. The fecal coliform levels were analyzed in each sampled batch.

Results

The period from early December to mid April was considered to have no significant risks of bacteriological contamination due to ice and relatively low water temperatures, suggesting dormant oysters. Samples taken during that period showed no signs of bacteriological contamination. The spring period from mid April to mid May also shows relatively few significant risks of bacteriological contamination since the oysters harvested at that time of year come from structures used for overwintering. The total fecal coliform levels were relatively low during that period. In addition, although fecal coliforms were present in samples during that period, the levels were not high and were lower than regulatory requirements. The same was true for the period from mid May to late June. Since seabirds do not generally use the culture structures before early July, probably due to the weaning period, the contamination risks for that period were deemed relatively low. Risks of bacteriological contamination in the fall, from mid September to early December, would also be relatively limited considering the low fecal coliform levels reported in the samples and the fact that oysters are generally in overwintering conditions, the weaning period has finished and seabird populations in oyster production areas have decreased considerably.

Distribution of results according to fecal coliform levels in the samples: Ninety four (94) percent of the batches did not exceed the tolerance limits, 8.23% had levels between 230 and 1,000 MPN, while 2.16% (3 samples) had over 1,000 coliforms per litre. In the group between 230 and 1,000 MPN, 12 batches had contamination levels below 280 MPN. Aside from one batch from Lamèque Bay, samples that had levels above 500 MPN came from oysters that had not been conditioned, which shows the increased bacteriological contamination of oysters raised in suspension in floating bags and OysterGro cages, in case producers should ever want to avoid conditioning their oysters. Samples were taken during the critical period from high-risk regions, given the abundance of seabirds in those regions. The context for results obtained in Lamèque Bay differs in that oysters were stored in Dark Sea trays. In theory, they should have a fairly low risk of bacteriological contamination due to the technique's distinctive features. Therefore, to try to understand such a result, a series of water samples was taken after results of the bacteriological analysis were confirmed; they suggest that there were some spills. Even though the producer relocated his conditioning sites, the region was classified as high risk to prevent a similar situation from recurring.

Signs of bacteriological contamination were observed more frequently during summer months, though they were generally below the limits. A 29% proportion of the samples showed no signs of bacteriological contamination in the summer compared to 40% in the spring and fall. The averages for batches that showed signs of bacteriological contamination were 75.2% for the summer compared to 56.5% for the spring and fall. These results could be from increased activity (density) of seabirds along the coasts, although other factors such as heavy rainfall could have consequences. Therefore, the entire area might have a low risk of bacteriological contamination that is not necessarily related to culture structures or the proximity to human development. The results indicate that the prescribed conditioning procedures for suspended oysters would be appropriate.

Signs of more frequent contamination were observed for certain regions and seem to correlate with the proximity to harbour infrastructure and coastal communities and even the migration patterns of seabird colonies. Tracadie, Neguac, Richibouctou and Bouctouche bays would therefore be more problematic. Even though the sampling was not very representative, Lamèque and Shippagan bays were also deemed critical due to the proximity of harbour infrastructures and the abundance of seabirds. Saint-Simon Bay South and Saint-Simon Bay North have lower contamination risks due to fewer seabirds and less shoreline usage. It is important to note that few samples were taken in this region during the summer. Tabusintac Bay and others seem to have variable conditions; the estuary seems more problematic than the bay.

Proposed Oyster Safety Management Procedure

The results obtained over the past three years as part of the oyster sampling program to track coliforms and access its new holding tank storage and conditioning facilities can be used to direct our efforts based on oyster safety risk. Maison BeauSoleil Inc. suggests the following oyster safety management plan based on three strategic elements: a definition of the risk levels, categorization of the periods, regions and suppliers according to their risk level, and a processing procedure for batches according to their risk level.

The risk definitions are as follows:

The high-risk batches of oysters imply that they might have high fecal coliform levels, higher than the standards established in the Fish Inspection Regulations (higher than 230 MPN). The batches could have come from a supplier who had not conditioned the oysters, is operating in a region with major human development and a considerable seabird colony during a critical period or, from a new supplier who had not yet established credibility with the company and is operating in a region with major human development and considerable seabird colonies during a critical period.

The medium-risk batches imply that they might show signs of contamination, but little risk of surpassing the Fish Inspection Regulations (higher than 230 MPN). The batches could have come from a supplier who had a history with the plant that had conditioned its oysters. The oysters could be from a region with major human development and a considerable seabird colony during a critical period. The batches could also be from regions with low levels of human activity and low seabird density, without conditioning in a non-critical period.

The low-risk batches have a low risk of showing signs of bacteriological contamination. The batches could have been delivered during a non-critical period from a supplier who had a history with the plant that conditioned its oysters. Oysters harvested during a critical period in the regions with little human activity and low use by seabirds are also included in this group.

The batches with no significant risk have negligible risks of bacteriological contamination. The oysters could have been harvested during a no-risk period or stored in overwintering structures in regions with low levels of human activity and low seabird density.

The batch processing procedure based on bacteriological contamination risk that the company intends to implement, considering the risk management criteria and the storage and conditioning capacity of the storage plant includes a 48-hour holding tank conditioning period for medium- and high-risk batches or a 6-day sea conditioning period given that oysters come from open shellfish harvesting areas. A 48-hour processing period was deemed sufficient for oyster conditioning in decontamination plants while a 6-day, at-sea period was deemed sufficient for oysters raised in suspension. Microbiological tests will be conducted on all medium- and high-risk batches to ensure product safety before marketing or transferring them to holding tanks for storage. However, since holding tank system operation could not be completely validated, we suggest following an intermediary protocol in order to confirm the procedure. The intermediary procedure in place for 2010 is defined as follows:

High-risk batches. All high-risk batches will be placed in a refrigerated warehouse and an oyster sample will be taken for bacteriological analysis. The results of the analysis will determine the processing procedure for those batches. In cases where the total fecal coliform or coliform levels are higher than Canadian Food Inspection Agency standards, the batches will be transferred to the company's deep water oyster conditioning/decontamination sites. In cases where signs of bacteriological contamination have been noted, but they are below the prescribed limits of the Fish Inspection Regulations, the batches would be stored in holding tanks for conditioning. The number of days in storage would be based on the level of contamination. An oyster sample would be taken for bacteriological analysis before their processing or transfer to holding tanks for storage. In cases where no signs of contamination are noted in the samples, the batches could be directly transferred to holding tanks for storage or could be processed.

Medium-risk batches. In cases where batches pose a potential risk (medium) according to site, period and supplier criteria, a sample will be taken upon reception and the batches will be stored in conditioning tanks. In cases where the contamination levels are higher than the regulatory requirements, oyster batches will be immediately transferred to the company's deep water oyster conditioning site. In cases where contamination levels are lower than the regulatory requirements (lower than 230 MPN), batches will be stored in conditioning tanks. The length of conditioning will be based on the safety level. Monitoring was suggested for 2010 to establish operational standards for conditioning in holding tanks according to water temperature regime and tank position. Before the standards are established, a second series of samples will be taken from the batches prior to their transfer to storage tanks in preparation for processing. Batches that show no signs of contamination could be directly transferred to storage tanks in preparation for processing without further analysis.

In cases where batches pose a low risk, they will be stored in conditioning tanks for two days before being transferred to storage tanks in preparation for processing. No samples would need to be taken for bacteriological analysis. Considering the risks would be limited to signs of contamination below regulatory requirements, a two-day conditioning period is deemed sufficient.

Batches that pose no significant risks can be processed immediately without decontamination procedures or stored directly in holding tanks for processing.

Conclusion

The approach suggested by Maison BeauSoleil Inc. should help improve risk management related to the safety of oysters marketed by the company. However, there are still some aspects that it wants to validate that would allow it to further clarify its approach for both safety assurance and certification. Continuing its sampling program for oyster inventory management and operating its shellfish storage plant would allow for the creation of a more comprehensive history for each period, each bay and each producer. Scientific monitoring is planned for 2010 to more clearly define the operational procedures for the holding tank oyster conditioning system, including the length of shellfish conditioning based on product safety level and temperature regime. A better understanding of the plant's operational ability could also help to reduce sampling. It would no longer be necessary to take samples after holding tank conditioning of batches posing a low risk or even a medium risk of bacteriological contamination.

The operational limits were established based on the Fish Inspection Regulations, specifically from 20 to 230 (MPN) for the transfer to conditioning within the plant. Having a better understanding of how the holding tank system performs could make it possible to transfer the batches with the highest risk levels without overloading the system, while maintaining the plant's product safety certification requirements and reviewing the conditioning procedure for batches in the sea. In terms of scientific monitoring, stricter sampling at every stage of the process could help specify and validate the conditioning procedure for oysters that will be marketed.

Overall Conclusions

With the anticipated increase in production volumes over the next few years, the NB oyster industry or Canadian industry as a whole could face a marketing problem if it fails to set up infrastructures to globalize its markets. Safety assurance and product labelling requirements related to decontamination are also constraints that need to be addressed in order to help the NB oyster industry reach its full potential. Depuration and infrastructures had been identified by the NB oyster industry as priorities for innovation. In the context of the NB oyster industry, because of the cultivation technique that involves a risk in terms of shellfish safety, implementing a multifunctional closed circuit infrastructure is an essential part of a coordinated development strategy. The difficulties in meeting the demand and, as a result, supplying increasingly large volumes during critical periods (ice forming and break-up, closures due to PSP toxins) could be addressed by building new facilities. Similarly, risks of introducing illnesses and invasive species could be minimized along with increased closures due to PSP toxins. Building new facilities is an important tool for introducing a safety assurance program, not only to allow the company to take their product safety certification further while relaxing regulatory requirements, but also to help the NB and Canadian oyster industry become more competitive in export markets.

Construction work on the new shellfish storage facilities operating in a closed circuit could not be completed until the fall. Despite construction delays, a series of trials was completed in the fall and more than one million oysters were placed and kept in storage for sale during the winter without any operational constraints. Even though they were basic, the trials for oyster conditioning in holding tanks demonstrated the potential of the closed circuit approach, given its capacity to operate at higher temperatures.

The project enabled the NB oyster industry to equip itself with the tools to address NB shellfish marketing constraints and especially:

  1. Regulatory requirements related to conditioning in the sea and product safety.
  2. Regulatory restrictions on exports to European and Asian markets.
  3. More restrictive requirements for environmental protection and the introduction of invasive species.
  4. The need to be able to supply markets on a continual basis throughout the year and especially during critical periods.
  5. Product safety assurance.

More importantly, this type of infrastructure, associated with a better understanding of the safety risks of oysters raised in suspension, could enable the company to implement and further develop its oyster harvesting strategy based on the degree of product safety risk. Confident about the results obtained and the support it received from the Canadian Food Inspection Agency, Maison BeauSoleil Inc. is planning a handling series starting in 2010 to further develop its certification approach for the safety of its product. It is planning on leading the following projects:

An oyster batch sampling program to refine its risk analysis.

Mastering the operational conditions of its shellfish storage facilities in a closed circuit.

Improving the conditioning procedures of oysters in the sea and in holding tanks.

Validating the temperature limits (0-5°C versus 5-10°C) for shellfish storage to reduce energy costs.

Fine tuning a conditioning technique for summer sales of the American oyster (in terms of meat yields) and the European oyster (no oyster larvae in the meat).

The idea of a shellfish storage plant operating in a closed circuit and the operation of its holding tank system has already aroused the interest of the east coast shellfish industry. The company has already addressed information requests from a PEI processing plant that had to close its culture sites during the summer due to heavy rainfall and the associated bacteriological contamination risks. It thinks that the approach proposed by Maison BeauSoleil Inc. would help them better manage the risks associated with unexpected closures. A Nova Scotia lobster trading company also expressed strong interest in the approach developed by Maison BeauSoleil Inc., specifically the idea that a closed circuit system could enable them to better define regulatory requirements for exporting shellfish to Europe.

1 Hussenot J., Piquet J.-C. (2006). Purification de coquillages en Escherichia coli, essai avec et sans traitement de l'eau (écumeur Skim). 1. Conditions de température estivale. Rapport d'essai confidentiel pour EMYG Aquaculture. - In : IFREMER-LGP, Arcachon 3 juillet 2006.

2 Comeau, L.A., P. St. Onge, F. Pernet et L. Lanteigne. 2008. Deterring coastal birds from roosting on oyster culture gear in eastern New Brunswick, Canada. Aquacultural Engineering.

Date Modified: 2012-11-06

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