Funding: Data2ustain
Irish Ocean Harvest Ltd
Irish Ocean Harvest approached Data2Sustain to investigate and test an improved aeration system and monitoring solution for a prototype 10,000-litre oyster holding tank. The client expressed strong interest in developing a complete system that would improve the quality and condition of the oysters prior to shipping, while also providing continuous monitoring and control of key water parameters, including temperature, salinity, dissolved oxygen and PH.
The Challenge
A key requirement identified by the client was the ability to remotely monitor these parameters, as their existing system required personnel to travel to the site several times per day to manually check and record the readings. The client also highlighted the potential to improve the existing process through better data collection, allowing operating conditions to be monitored over time and potentially optimised based on the information gathered.
A second area of interest identified during the investigation was the development of a remote pumping station to improve the management of water levels within the tanks. The proposed system would allow water to be pumped remotely from the main house to top up the tanks when required, or to fill the tanks in preparation for the following weeks batch of oysters. This would further reduce the requirement for manual intervention and site visits while improving the efficiency and consistency of the overall process. The project therefore presented an opportunity to develop an integrated system combining aeration, water-quality monitoring, remote control, data collection and automated pumping, with the potential to significantly improve the management and quality of the oyster holding process.
WiSAR Solution
Mechanical Design and Process Control:
The client purchased a 10,000-litre tank for the development of the test before invest prototype system. Before progressing to the optimisation and control aspects of the project, the first area investigated was the existing aeration process. The client was using a surface aeration method in the existing system, whereby water was continuously recirculated from the tank and discharged through a spray bar positioned above the water surface. This process allowed atmospheric oxygen to mix with the water and increase the dissolved oxygen levels. However, it was identified that during the warmer seasons, the dissolved oxygen percentage could fall significantly, which presented a risk to oyster health and resulted in potentially high levels of oyster mortality.
The testing phase involved a number of different aeration trials, which took approximately four to five weeks to complete. The initial trial consisted of a small pond system using a customer-supplied pump, with a Venturi system fitted to draw air into the water and promote oxygen transfer. This produced marginally positive results; however, it was identified that a separate Venturi system would likely be required for each tank if the system were to be fully integrated. This would result in a significant increase in both capital and ongoing energy costs as the number of tanks increased.
Following further research, the project moved towards a diffused aeration system. A 200 litre per-minute air pump was purchased for testing, with two fine-bubble tube diffusers installed in the tank using flexible hoses and weights to position them within the water. During the trials, it became apparent that the type of diffuser and the available air pressure were important factors. The air pump was operating at approximately 0.3 bar, and the relatively long pipe run around the tank meant that any pressure loss, restriction or leakage within the system had a significant effect on performance. The fine-bubble diffusers also presented difficulties when attempting to position them at the bottom of the tank. Research indicated that placing the diffusers as low as practical would provide greater contact time between the air bubbles and the water, allowing more oxygen to be transferred before the bubbles reached the surface. However, when the fine-bubble diffusers were positioned approximately one metre from the bottom of the tank, although good oxygen levels were achieved, the air distribution and water mixing were not sufficient and the pump couldn’t overcome the hydrostatic effect of the water acting on the pump. The aeration remained concentrated in a particular area of the tank, resulting in areas with limited circulation or potential “dead spots”.
Further research and consultation with an aeration specialist, the system was changed from fine-bubble to coarse-bubble diffusers. This produced significantly more aggressive mixing throughout the tank and proved more suitable for the application. The dissolved oxygen levels increased and remained more consistent throughout the testing period, while the client also reported a very low mortality rate among the oysters. The testing process involved continual modification and optimisation of the flexible pipework, diffuser arrangements and pump configuration before the final diffused aeration system was established.
Once the mechanical aeration system had been proven and the client was satisfied with the resulting dissolved oxygen levels and oyster condition, the project could progress towards the automation and monitoring stage. The proposed system would incorporate monitoring of key water parameters, including dissolved oxygen, pH and salinity, with the potential for remote monitoring and control. One of the main advantages identified with the final aeration system was that only one air pump would be required per tank system, providing a considerably more economical solution than the initial Venturi-based approach if the system were expanded commercially. This has the potential to reduce both capital expenditure and ongoing energy consumption while maintaining improved water conditions and oyster quality. As part of the final stage, the client was also provided with preliminary requirements for potential future commercialisation, including pump sizing and a pipework schedule to assist with the development and expansion of the system at a later stage.
Automation & Control:
With regard to the automated monitoring system, a PLC programme was developed to process the analogue signals from the pH, temperature, salinity and dissolved oxygen sensors. A small test rig was modified to allow the sensors to be connected and readings to be collected and monitored through the PLC. These readings were then compared against the customer’s existing instruments, which had been recently calibrated, to verify the accuracy of the new monitoring system. Once the client was satisfied that the readings from the PLC-based system were consistent with the calibrated instruments, the next stage involved investigating remote connectivity. The PLC was configured to allow the monitored values to be accessed remotely through an IP address, demonstrating that the customer could view the water-quality parameters without having to physically attend the site.
The successful demonstration of the remote monitoring system reassured the client that the proposed solution could significantly reduce the time currently spent travelling to the site to manually check and record water-quality readings. In addition to the monitoring system, PLC programming was also developed for the proposed remote pumping system, allowing the pumping process to be incorporated into the overall automated solution. The research, testing and programming carried out during the project demonstrated that the monitoring, control and pumping systems could be integrated into a single solution relatively easily and at a comparatively low cost. This provides the client with a practical foundation for developing and implementing a larger commercial system in the future, with the potential to further automate the process and improve both operational efficiency and water-quality management.
Environmental Considerations:
- Designing the system around one appropriately sized air pump per tank, rather than multiple individual aeration units, provides an opportunity to reduce the energy and equipment requirements as the oyster-holding operation expands.
- Data-driven environmental management – Continuous recording of temperature, salinity, pH and dissolved oxygen would provide a better understanding of how the tank environment changes over time. This could allow the system to be operated more efficiently and identify problems before they lead to significant environmental or biological impacts.
- Reduced travel and emissions – Remote monitoring means the operator does not need to travel to the site several times per day to manually check water parameters. This could reduce vehicle use, fuel consumption and associated carbon emissions.
Impact & Benefits
Overall, the project was successful in demonstrating the technical feasibility and potential commercial benefits of the proposed system. The prototype mechanical aeration system demonstrated that the dissolved oxygen level within the water could be significantly increased and maintained at a more stable level. This provides the client with the potential to improve the condition and quality of the oysters prior to sale while also significantly reducing oyster mortality during the holding period. From a data and automation perspective, the project successfully demonstrated how the system could be fully automated and how key water-quality parameters, including dissolved oxygen, temperature, pH and salinity, could be monitored remotely. The prototype sensors were connected to the PLC system, with the collected data made accessible remotely through an IP address. This demonstrated to the client that the requirement for frequent manual visits to the site could potentially be significantly reduced, while also providing a continuous record of the conditions within each tank.
Following the successful completion of the prototype testing, the client has positively engaged with the findings and intends to investigate funding opportunities to further develop and commercialise the system. A further area of development identified by the client is the use of the collected data for batch-level monitoring and traceability. The proposed system could assign each tank or batch of oysters a unique QR code, which could then be linked to information such as the date the oysters were harvested, when they entered the holding tanks, and the temperature, dissolved oxygen, salinity and pH conditions recorded throughout the holding period. This could ultimately create a digital passport for each batch of oysters, providing a detailed record of the environmental conditions and handling history from harvesting through to sale. The client sees significant potential in this concept as a future development of the project, particularly in improving traceability, demonstrating product quality and providing customers with greater transparency regarding the origin and conditions of the seafood product.
Social & Economic Benefits:
Reduced Operating Costs:
- The proposed aeration system has the potential to reduce energy consumption by using a single appropriately sized air pump per tank rather than multiple individual aeration systems. This could reduce ongoing electricity costs as the system is expanded.
Reduced Labour Requirements:
- Remote monitoring of dissolved oxygen, temperature, salinity and pH would reduce the need for the client to travel to the site several times per day to manually check readings. This would save time and allow staff to focus on other areas of the business.
Improved Oyster Quality:
- More stable and controllable water conditions should help maintain the oysters in better condition prior to sale, potentially reducing mortality and increasing the proportion of oysters that reach the customer in saleable condition.
Future Digital Product Passport:
- The data collected from each batch could potentially form the basis of a digital passport for the oysters, providing customers with information on their origin, handling and environmental conditions. This could create additional commercial value and support future traceability requirements.
