Biosecurity Planning Research Articles

Description of swine producer biosecurity planning for foreign animal disease preparedness using the Secure Pork Supply framework.

Preventing potential foreign animal diseases is a high priority, with re-emerging threats such as African Swine Fever emerging close to North American borders. The Secure Pork Supply (SPS) plan provides a voluntary framework for swine producer biosecurity planning and disease outbreak preparedness. However, biosecurity knowledge varies greatly among swine veterinarians, managers, and caretakers within the industry, which impacts the understanding, quality, implementation and biosecurity plan agreements with the SPS guidelines unless review procedures and quality control mechanisms are in place. Therefore, this study aimed to describe and identify the level of biosecurity planning agreements between producer-and/or swine veterinarian-made biosecurity plans for commercial swine sites and the SPS plan guidelines during a review process. Biosecurity maps (N = 368) and written plans (N = 247) were obtained from six Midwest swine companies/veterinary clinics. Maps were evaluated on accuracy and placement of mandatory map features based on SPS guidelines, and discrepancies between the development of producer-made biosecurity maps and written biosecurity plans. Multivariable mixed logistic regression analyses were conducted to identify differences in SPS planning accuracy based on herd size, production stage, and characteristics related to geographical site location (e.g., land cover type and expected feral swine population density in the region). In this study, 55.8% (205/368) of all provided biosecurity maps had to be revised due to misplaced or missing map features. In addition, 80.9% (200/247) of the written plans had one or more conflicts with the corresponding biosecurity maps. The main biosecurity planning issues involved feed delivery activities, where the mapping of vehicle movements (89.9%, 222/247) were in direct conflict with the written SPS plans. Sites located in areas with a moderate expected feral swine population density had 3-fold increased odds of needing map revisions compared to sites with low expected feral swine population density. Sites located in predominately farmland had 7.3% lower odds of having biosecurity map and SPS plan conflicts for every 1.0% increase in farmland landcover in a 10-km radius around the swine site. Human oversight or lack of knowledge regarding biosecurity planning and implementation is common, which may culminate in important preparedness shortcomings in disease prevention and control strategies for U.S. swine farms. Future efforts should focus on additional biosecurity training for swine producers and veterinarians alongside with quality control benchmarking of producer made plans.

Cross-Sectional Survey of Horse Owners to Assess Their Knowledge and Use of Biosecurity Practices for Equine Infectious Diseases in the United States.

Horses are transported in the United States more than any other livestock species and co-mingle at various events; therefore, they are considered to be at an increased risk for infectious disease transmission. The fragmented movement of horses combined with numerous sites of co-mingling makes tracing the potential spread of a disease outbreak a necessary part of an infection control plan, both locally and nationally. The cross-movement of personnel with horses and the persistence of endemic diseases make biosecurity implementation an ongoing challenge. Although many of the risks for infection are known, there is limited documentation about the usefulness of prospective control measures. The objective of this survey was to determine horse owners' understanding and knowledge of biosecurity practices for preventing infectious diseases in the United States. Questions covered owner demographic information, including horse use which was divided into 10 categories as follows: Pleasure/Trail Riding, Lessons/School, Western Show, English Show, Breeding, Farm/Ranch, Retired, Racing, Driving and Other. The survey was distributed by sending requests to a list of horse owner organizations, which then sent emails to their members. The email request described the survey and provided a website link to start the survey. A total of 2413 responses were collected. Analysis of the results included cross-tabulation to identify significant differences in biosecurity knowledge and awareness by horse use. Significant differences by horse use were identified for vaccination, biosecurity planning, use of isolation, disease risk, monitoring for diseases, co-mingling of horses, sanitation, medical decision making and health record requirements for horse events. In summary, the results suggest that most owners are not highly concerned about the risk of disease or the use of biosecurity. There are several biosecurity applications and techniques which can be increased and will benefit horse health and welfare. These include reliance on temperature monitoring, isolation of new horses at facilities, risks of horse mingling, entry requirements such as vaccination and health certificates at events, and an emphasis on having biosecurity plans for facilities and events where horses co-mingle. The information from this study will be used to create tools and information that horse owners and veterinarians can use to implement appropriate biosecurity practices for different types of horse uses and events.

Unevenly distributed biological invasion costs among origin and recipient regions

Globalization challenges sustainability by intensifying the ecological and economic impacts of biological invasions. These impacts may be unevenly distributed worldwide, with costs disproportionately incurred by a few regions. We identify economic cost distributions of invasions among origin and recipient countries and continents, and determine socio-economic and biodiversity-related predictors of cost dynamics. Using data filtered from the InvaCost database, which inevitably includes geographic biases in cost reporting, we found that recorded costly invasive alien species have originated from almost all regions, most frequently causing impacts to Europe. In terms of cost magnitude, reported monetary costs predominantly resulted from species with origins in Asia impacting North America. High reported cost linkages (flows) between species’ native countries and their invaded countries were related to proxies of shared environments and shared trade history. This pattern can be partly attributed to the legacy of colonial expansion and trade patterns. The characterization of ‘sender’ and ‘receiver’ regions of invasive alien species and their associated cost can contribute to more sustainable economies and societies while protecting biodiversity by informing biosecurity planning and the prioritization of control efforts across invasion routes. The impacts of biological invasions may be unevenly distributed globally, with a few regions bearing most of the cost. This study identifies cost distributions of invasions among origin and recipient countries and continents, and determines socio-economic and environmental predictors of cost dynamics.

Multiple invasion trajectories induce niche dynamics inconsistency and increase risk uncertainty of a plant invader

AbstractOur knowledge of how niche dynamic patterns respond to invasion trajectories and influence invasion risk prediction is elusive for the majority of notorious invaders, hindering scientific understanding, biosecurity planning and practice, and management implementation of biological invasions. We used Mikania micrantha, one of the world's worst invasive alien species (IAS), to test the hypothesis that multiple invasion trajectories could induce niche dynamics inconsistency and increase risk uncertainty of IAS. We compiled a robust database of M. micrantha occurrence across its native range in Central and South America and invaded range in China. This database was used to clarify different invaded ranges and invasion trajectories of M. micrantha in China. Principal components analysis of climatic variables associated with the database was used to explore the niche dynamic patterns associated with multiple invasion trajectories of M. micrantha. Maximum entropy algorithm was used to predict the high‐risk area of M. micrantha invasion using occurrence datasets for invaded ranges where niches remained conservative, and to detect area changes with the inclusion of occurrence datasets for invaded ranges where niche shifts occurred. M. micrantha invasion occurred in three geographically distinct regions, with conservative climate niches in southern and southeastern China and climatic niche shifts in southwestern China. A high‐risk area for M. micrantha invasion spanned multiple provinces and cities and expanded considerably with the inclusion of the occurrence dataset for southwestern China. Our findings contribute to the theoretical understanding of invasion mechanisms and the practical optimization of biosecurity planning and implementation.

Practical biosecurity – an integral piece to herd health planning

Biosecurity is the one aspect of a cattle operation that the pro­ducer has the most control over. Each producer has practices in place to protect their cattle and optimize their health. Vet­erinarians are purposefully trained to understand the compo­nents of biosecurity including animal health, epidemiology, infectious disease and public health consequences. Biosecurity planning is an important piece to herd health planning that can benefit the producer and the veterinarian. The National Cattle­men’s Beef Association (NCBA) Producer Education team works on the Beef Quality Assurance (BQA) and other Beef Checkoff-funded programs each day to ensure cattle producers and vet­erinarians have industry-leading information and resources. Several resources developed by the Producer Education team at NCBA, and the separately managed Secure Beef Supply, are available for producers, veterinarians and transporters to re­view for more information on biosecurity to improve cattle wel­fare before and during potential disease outbreaks.

Prevention and preparedness: biosecurity, early warning and contingency planning

Disaster and disaster risk management are described differently by various agencies, but the underlying principles remain the same. Disaster risk management is a continuous and integrated multidisciplinary and multisectoral process of planning and implementing measures that establish a culture of risk avoidance by building resilient communities. Such communities can only be created through a systematic process of education, training and development, involving all stakeholders. A researched comprehensive disaster management plan should be developed, but will only be successful if it sets clear priorities; is practised, tested, adapted and/or amended where necessary; and is practical, feasible and well understood by all those who are involved. Everyone who plays a role in implementing this plan must recognise that role and be well trained in its execution. Capacity building for disaster management is also a multisectoral, multidisciplinary, integrative process, achieved through a system of integrated education, training and public awareness programmes.

Multiple invasions of a generalist herbivore-Secondary contact between two divergent lineages of Nezara viridula Linnaeus in Australia.

The presence of distinct evolutionary lineages within herbivorous pest insect taxa requires close attention. Scientific understanding, biosecurity planning and practice, and pest management decision‐making each suffer when such situations remain poorly understood. The pest bug Nezara viridula Linnaeus has been recorded from numerous host plants and has two globally distributed mitochondrial (mtDNA) lineages. These mtDNA lineages co‐occur in few locations globally, and the consequences of their divergence and recent secondary contact have not been assessed. We present evidence that both mtDNA lineages of N. viridula are present in Australia and their haplotype groups have a mostly separate distribution from one another. The north‐western population has only Asian mtDNA haplotypes, and the population with an eastern distribution is characterized mostly by European mtDNA haplotypes. Haplotypes of both lineages were detected together at only one site in the north of eastern Australia, and microsatellite data indicate that this secondary contact has resulted in mating across the lineages. Admixture and the movement of mtDNA haplotypes outside of this limited area of overlap has not, however, been extensive. Some degree of mating incompatibility or differences in the climatic requirements and tolerances of the two lineages, and perhaps a combination of these influences, might limit introgression and the movement of individuals, but this needs to be tested. This work provides the foundation for further ecological investigation of the lineages of N. viridula, particularly the consequences of admixture on the ecology of this widespread pest. We propose that for now, the Asian and European lineages of N. viridula would best be investigated as subspecies, so that “pure” and admixed populations of this bug can each be considered directly with respect to management and research priorities.

Tourism biosecurity risk management and planning: an international comparative analysis and implications for Ireland

Gestión y planificación de riesgos de bioseguridad en el turismo: un análisis comparativo internacional y sus implicaciones Para irlandaPropósitoEste documento tiene como objetivo revisar el estado de la planificación nacional de bioseguridad. Los autores reconocieron que la vectorización turística puede aumentar el riesgo de especies exóticas invasoras (EEI) y enfermedades; representa un riesgo sustancial de bioseguridad para los destinos turísticos de todo el mundo. Esta investigación evalúa la provisión de medidas de mitigación de bioseguridad dentro de los planes y directrices nacionales de bioseguridad a nivel internacional. La posición del autor en este tema sostiene que la falta de suficiente gestión y planificación del riesgo de bioseguridad para el turismo podría tener graves impactos en el medio ambiente, la sociedad y la economía de un destino.Metodología de diseñoLos autores revisaron sistemáticamente la planificación nacional de bioseguridad a través de un enfoque de investigación de métodos mixtos. Los primeros criterios esenciales identificados a partir de la literatura internacional permitieron el análisis de contenido para evaluar planes y estrategias nacionales de bioseguridad específicos. En segundo lugar, los datos cualitativos se recopilaron realizando entrevistas semiestructuradas dentro de los organismos y organizaciones nacionales de gobierno.RecomendacionesLa planificación de la bioseguridad turística varía en todo el mundo, y algunos destinos demuestran planes muy evolucionados, como Hawai, Nueva Zelanda y Australia. Sin embargo, este no es el caso en Irlanda, donde la planificación de la bioseguridad a nivel nacional está severamente limitada. La planificación de la bioseguridad, la gestión de vías, la comunicación, la cuarentena y los planes de riesgo turístico son inadecuados para evitar la introducción y propagación de EEI y enfermedades en Irlanda. Las recomendaciones ofrecen a los destinos de todo el mundo y con el “estado de la isla” una oportunidad para mejorar la bioseguridad mediante el uso de vigilancia, comunicación, directrices y capacidades específicas en las etapas fronterizas dentro de un plan nacional de bioseguridad específico.Originalidad/ValorEsta revisión sobre el estado de la planificación nacional para la bioseguridad proporciona nuevos conocimientos específicamente para destinos turísticos en todo el mundo que pueden adoptar los elementos esenciales identificados dentro de esta investigación para un marco nacional de riesgo de bioseguridad turística.

Biosecurity Risk and Tourist Communication in Ireland

A lack of sufficient biosecurity communication for tourists can lead to higher biosecurity risk which may result in severe environmental, human health and associated economic impacts. The scope of this research is to assess biosecurity plans and communication strategies of Ireland’s major ports, state agencies and governing bodies involved in outdoor recreational activities which have the potential to mitigate biosecurity risk. A mixed method approach was utilised which consisted of content analysis as well as structured qualitative interviews. Analysis has revealed limited communication to tourists arriving in Ireland’s ports and few plans or biosecurity communication strategies in place by national agencies. The need to provide adequate communication of biosecurity measures aimed at mitigating the potential for tourists to vector dangerous microbes and aid biological invasions seems not to have been recognised. In order to reduce Ireland’s biosecurity risk the need for comprehensive biosecurity planning and communication is vital in order to increase tourist awareness of biosecurity measures at pre-border, border, and post-border stages. This paper concludes that low levels of biosecurity communication is worrying and may pose a considerable biosecurity risk to Ireland. It offers an opportunity to be improved before a serious biosecurity breach occurs possibly resulting in a lost tourist season or expensive eradication programmes as has been witnessed in other destinations worldwide. This research has also highlighted the need for theory to adequately reflect the role of communication by emphasising its inclusion in new or updated biosecurity frameworks to be developed into the future.

Modelling the establishment, spread and distribution shifts of pests

During the last century increasing human trade networks have interacted with other global changes – such as land use and climate change – to accelerate the range expansion of pest species worldwide. In this special issue, we present a series of articles that model the risk of establishment and spread of non-native harmful species, as well as shifts in the distribution of native pest species. We also provide a state-of the art review of the available literature on species distribution models for pests, weeds, and pathogens. Recent advances in modelling approaches have allowed us to significantly improve our abilities to predict changes in species distribution, and these tools have been widely used to enhance biosecurity planning and pest management. We expect that this special issue contributes toward and integration of the scientific knowledge and the development of novel approaches to model pest species distribution, as well as to better understand the factors that influence their expansion in the context of a rapidly changing world.

Understanding the biosecurity monitoring and reporting intentions of livestock producers: Identifying opportunities for behaviour change

In many countries, government strategies for biosecurity planning and outbreaks depend upon private livestock producers being willing and able to conduct surveillance of their animals and the timely reporting of suspicious signs of disease. From a behavioural perspective, these two kinds of behaviours – surveillance and reporting – should be treated separately when developing a biosecurity plan in which producers play a key role in the prevention, detection, and reporting of animal diseases. Having an effective surveillance system in place is conceptually and practically independent of a reporting system that is both feasible and trustworthy. The behavioural intentions of 200 Australian producers to monitor their livestock and report to either the government or a private vet were measured in a structured telephone interview. Structural equation modelling revealed that these intentions had different statistical relationships with a common set of predictor variables. Moreover, classification of the producers based on belief about monitoring and surveillance resulted in three contrasting groups. These results are discussed in terms of their meaning for the development of behavioural strategies to promote surveillance and monitoring of animal disease.

The role of the social sciences and economics in understanding and informing tree biosecurity policy and planning: a global summary and synthesis

Increased global biosecurity threats to trees, woods and forests have been strongly linked to the upsurge in worldwide trade and the expansion of tourism. A whole range of social, economic and political actors are implicated and affected by the movement of pests and diseases along these international pathways. A number of factors affect the actions of stakeholders, and wider public, including their values and motivations, how risks are perceived and acted upon, their ability to act, as well as the existing regulatory and economic environment. Understanding these factors is key to any future attempts to improve biosecurity policy and practice, and we present available evidence on six key dimension: (1) the role of different stakeholders and the broader public within tree health; (2) levels of knowledge and awareness of tree pests and diseases amongst the variety of end-user ‘stakeholder’ groups, and influences on their attitudes and practices; (3) social acceptability of management approaches; (4) the impact of formal and informal governance arrangements; (5) risk communication; (6) economic analyses on the impact of tree pests. We conclude by identifying evidence gaps and emphasising the need for better integration within the social sciences and between the social and natural sciences to promote effective interdisciplinary and policy-relevant contributions to tree health.

Amphibian conservation: clarifications to comments from Andreone

We appreciate the comments from Andreone (2016) regarding our proposed alternative strategy for addressing the amphibian crisis. Andreone recognizes the utility of an Incident Command System approach but doubts the feasibility of implementation at an international level. We stated in our original article, however, that ‘the feasibility of our suggestion is debatable, but our point is that radically different approaches are necessary to effectively manage the largest extinction event in modern history’ (Muths & Fisher, 2015). There are examples of where such top-down strategies are being applied; e.g. for the brown tree snake Boiga irregularis (Stanford & Rodda, 2007), and biosecurity planning for Micronesia and Hawaii (NAVFAC Pacific, 2016). Another example is presented by Andreone. In Madagascar a community-wide conservation plan has been developed complete with prioritization of specific actions (Andreone, 2016). As with any top-down strategy, challenges will surface, especially when making decisions that affect economics. We note this caveat in our article, and Andreone points out such issues in Madagascar, where there are mismatches in priorities between biodiversity conservation and civil needs. Our suggestion is that a new paradigm needs to be considered given the gravity of amphibian decline, and one option may be to take a global approach focusing on specific, major threats. Application of an Incident Command System would not necessitate competition with, or emasculation of, local conservation priorities or actions.

Biosecurity and the management of emergency animal disease among commercial beef producers in New South Wales and Queensland (Australia)

Australia places great importance on the prevention and management of emergency animal diseases (EAD), with strict quarantine measures offshore and at the border. Livestock producers are crucial for disease control onshore; however, limited information is available on commercial livestock producers’ practices in relation to the management of disease risks. The aims of this paper are to investigate how commercial beef producers in Australia’s Northern and Southern beef zones manage EADs and to identify drivers for effective biosecurity and EAD prevention. This paper forms part of a broader mixed methods research project involving an analysis of literature and current policies, qualitative semi-structured interviews with government and industry stakeholders and a cross-sectional study among beef producers. The cross-sectional study used a postal survey (n=182) and face-to-face interviews (n=34) to gather data on beef producers’ knowledge and practices on biosecurity and EADs and their communication networks. Findings indicate that producers are uncertain about the roles and responsibilities of stakeholders involved in biosecurity and EAD management. This uncertainty may create confusion about EAD management and impact upon producers’ willingness to report animal disease, with over 20% reporting the last veterinary contact more than five years ago and an additional 8.5% who had never contacted a veterinarian. Producers had a generally high awareness of the key sources of animal disease risk and they prioritise herd health planning as part of their everyday practices. Over 40% of producers had limited knowledge of the meaning of EAD; and EAD and biosecurity planning was given a low priority, primarily due to the perceived limited likelihood of an EAD event in Australia and the belief that EAD prevention is primarily the role of government. Only a moderate implementation of biosecurity practices, such as isolating incoming animals, having a single property entry point or keeping visitors’ records was reported. If faced with an unusual disease event, most producers would contact their private or government veterinarian; however, in some instances most would also treat themselves and over a third would do nothing. Findings from this study suggest that there is a need for better coordination between stakeholders to encourage a shared biosecurity and EAD understanding and to communicate a consistent message to all stakeholders including producers. Further, there is a need for improving producer awareness of the importance of EAD prevention and biosecurity practices as well as the stakeholders’ roles within the broader animal health system.

Will climate change impact the potential distribution of a native vine (Merremia peltata) which is behaving invasively in the Pacific region?

Merremia peltata is a species with uncertain status in the island nations of the Pacific region. It has been designated introduced and invasive in some countries whereas it is considered native in others. Recent increase in its abundance across some island landscapes have led to calls for its designation as an invasive species of environmental concern with biological control being suggested as a control strategy. Climate change will add to the complications of managing this species since changes in climate will influence its range limits. In this study, we develop a process-oriented niche model of M.peltata using CLIMEX to investigate the impacts of climate change on its potential distribution. Information on the climatic requirements of M.peltata and its current geographic distribution were used to calibrate the model. The results indicate that under current climate, 273,132km(2) of the land area in the region is climatically unsuitable or marginal for M.peltata whereas 664,524km(2) is suitable to highly suitable. Under current climate, areas of climatic suitability for M.peltata were identified on the archipelagos of Fiji, Papua New Guinea, Solomon Islands and Vanuatu. By the end of the century, some archipelagos like Fiji, Hawaii, New Caledonia and Vanuatu will probably become more suitable while PNG and Solomon Islands become less suitable for M.peltata. The results can be used to inform biosecurity planning, management and conservation strategies on islands.

A risk based approach to non-native species management and biosecurity planning

The introduction of non-native species (NNS) is becoming an increasing problem across the globe. The need to identify and manage the pathways of their introduction has been identified as a priority for biosecurity management. There is a clear role for marine spatial planning to provide a multi-sector framework to assist in this management. A risk-based approach to identifying pathways and areas of introduction has been developed for the Shetland Islands (north Scotland), as part of the Shetland Islands’ Marine Spatial Plan, Scotland. Working closely with local stakeholders was key to this process, which incorporates local and national data sets to form a high resolution model. It has been successfully used within the SIMSP and to guide the development of the Biosecurity Plan for the Shetland Islands. It also highlights the requirements for national and local legislation and policy to address and reduce all pathways within a region.

Taxonomic uncertainty and decision making for biosecurity: spatial models for myrtle/guava rust

The causal agent of myrtle rust, initially described as Uredo rangelii, was recorded in Australia for the first time in 2010. Much of the monitoring effort in Australia and elsewhere is driven by existing understanding of Puccinia psidii sensu lato (guava rust), because U. rangelii is part of the guava rust complex. Bioclimatic analyses for guava rust in Australia indicate highest risk along the eastern coast, from northern Queensland to the south coast of NSW. These analyses rely on native and invaded range records for Puccinia psidii sensu lato. However, models that are instead fitted to records representing U. rangelii emphasise different risk areas, with less focus on northern coastal Queensland and new predictions into NSW tablelands and north-eastern Victoria. These differences have important implications for biosecurity containment and monitoring efforts. Here we use this example as a case study to explore the implications of taxonomic uncertainty for predictions of the potential distribution of a species of biosecurity concern in Australia. The important message is that the different patterns implied by different taxonomic assumptions may have very different management implications and taxonomic uncertainty should be evaluated alongside other sources of uncertainty. We could find no published example where taxonomic uncertainty was evaluated in biosecurity planning, despite the fact that taxonomic uncertainties are common. We outline how to model such uncertainties and discuss methods for exploring them and their impacts on predicted distributions.

Nematodes: important players in biosecurity planning

Biodiversity, the variety of life on Earth, is essential to maintaining and sustaining the living networks and systems that provide humanity with health, wealth, food, fuel and the vital services that life depends upon. The year 2010 was celebrated as the International Year of Biodiversity with the aim of achieving a significant reduction in the rate of biodiversity loss at the global, regional and national levels as a contribution to poverty alleviation and to the benefit of all life on Earth. The rate of biodiversity loss is an ongoing problem and many of the underlying factors have not been given due attention. One of the sub-terrestrial factors that needs to be addressed during the post-2010 period is the biodiversity of nematodes, an important component of the food web and carbon cycle. The diversity of nematodes in agro-ecosystems, agro-forestry, animal husbandry, oceans/ponds/rivers, and their relationship to soil processes suggests that nematodes are important players in the maintenance of ecosystem biodiversity.

Feral pigs: predicting future distributions

Feral pig populations are expanding in many regions of the world following historically recent introductions. Populations are controlled to reduce damage to agriculture and the environment, and are also a recreational hunting resource. Knowledge of the area over which feral pigs may expand in the future could be used regionally to assist biosecurity planning, control efforts and the protection of biodiversity assets. The present study sought to estimate the future distribution of a recently introduced, expanding feral pig population in the remote Kimberley region of north-western Australia. An existing survey of feral pig distributions was enhanced and remote-sensing and weather data, reflecting or correlated with factors that may affect feral pig distributions, were collated and analysed. Relationships between feral pig distributions and these data were identified by using a generalised additive modelling approach. By the use of the model, the distribution of favourable habitat was estimated across the study region (89 125 km2). The potential future distribution of feral pigs in the Kimberley was then estimated, assuming only natural dispersal of feral pigs from areas of known feral pig status (cf. hunter-assisted movements or escape of domestic pigs). The modelling suggests that feral pigs could expand their distribution by realistic natural dispersal in the future (to 61 950 km2). This expansion possibility contains several strategically important areas (such as sea ports and biologically significant wetlands). This approach has the potential to improve biosecurity planning for the containment of the feral pig in the Kimberley and may have utility for other recently introduced invasive species in other regions. These results may also be used to improve pest-management programmes and contingency planning for exotic-disease incursions.

Process requirements for achieving full-flow disinfection of recirculating water using ozonation and UV irradiation

A continuous water disinfection process can be used to prevent the introduction and accumulation of obligate and opportunistic fish pathogens in recirculating aquaculture systems (RAS), especially during a disease outbreak when the causative agent would otherwise proliferate within the system. To proactively prevent the accumulation of fish pathogens, ozonation and ultraviolet (UV) irradiation processes have been used separately or in combination to treat water in RAS before it returns to the fish culture tanks. The objective of the present study was to determine the process requirements necessary to disinfect the full RAS flow, using ozonation followed by UV irradiation, just before the flow was returned to the fish culture tank(s). We found that a proportional-integral (PI) feed-back control loop was able to automatically adjust the concentration of ozone (O3) generated in the oxygen feed gas (and thus added in the low head oxygenator) in order to maintain the dissolved O3 residual or ORP at a pre-selected set-point. We determined that it was easier and effective to continuously monitor and automatically control O3 dose using an oxidative reduction potential (ORP) probe (in comparison to a dissolved ozone probe) that was located at the outlet of the O3 contact chamber and immediately before water entered the UV irradiation unit. PI control at an ORP set-point of 450 and 525mv and a dissolved O3 set-point of 20ppb provided almost complete full-flow inactivation of heterotrophic bacteria plate counts (i.e., producing <1cfu/mL) and improved water quality (especially color and %UVT) in a full-scale recirculating system. Achieving this level of treatment required adding a mean dose of approximately 29±3g O3 per kg feed. However, because water is treated and reused repeatedly in a water reuse system, the mean daily O3 demand required to maintain an ORP of 375–525mV (or at 20ppb dissolved O3) was 0.34–0.39mg/L, which is nearly 10 times lower than what is typically required to disinfect surface water in a single pass treatment. These findings can be used to improve biosecurity and product quality planning by providing a means for continuous water disinfection in controlled intensive RAS.