Search

Resirkulerende akvakultursystemer (RAS) har økt i popularitet som en bærekraftig og effektiv metode for oppdrett av fisk. Dette er lukkede systemer hvor vannet kontinuerlig blir resirkulert gjennom ulike vannbehandlingskomponenter for å opprettholde en stabil vannkvalitet. Dette reduserer behovet for vannutskiftning og minimerer miljøpåvirkningen sammenlignet med tradisjonelle oppdrettsmetoder. Formålet med bacheloroppgaven var å undersøke hvordan implementering av proteinskimmer påvirker vannturbiditet og nivåer av finpartikler i et RAS-anlegg, og hvilken effekt det har på vannkvalitet og fiskehelse og -velferd hos Atlantisk laks. I oppgaven ble det brukt metodetriangulering for å få mer innsikt og en dypere forståelse av bruken av proteinskimmer i resirkulerende akvakultursystemer. Det ble utført et grundig litteraturstudie ved å undersøke eksisterende litteratur og forskning for å kunne si noe om forventet effekt ved implementering av proteinskimmer. Resultatene indikererte at høyere konsentrasjoner av suspenderte og oppløste partikler kan øke turbiditet og vannfarge, samtidig som de kan redusere effekten av desinfiserende behandlingsmetoder som UV og ozon. Finpartikler og turbiditet kan påvirke fiskehelsen både direkte og indirekte. Resultatene av studiet avdekket imidlertid motstridende forskning når det gjaldt den direkte påvirkningen av suspenderte partikler på fiskehelsen. Oppgaven konkluderer med at implementering av proteinskimmer i resirkulerende akvakultursystemer har vist seg å være en effektiv metode for å redusere turbiditet og finpartikler i vannet. På grunn av begrenset litteratur og forskning er det usikkert hvordan turbiditet og finpartikler påvirker fiskehelse og -velferd i RAS-anlegg. Det er derfor viktig å utforske denne sammenhengen for å kunne sikre optimale miljøforhold, samt bidra til optimalisering av RAS som en bærekraftig og effektiv metode for oppdrett av atlantisk laks. Recirculating aquaculture systems (RAS) have gained popularity as a sustainable and efficient method for fish farming. These closed systems continuously recycle water through various water treatment components to maintain stable water quality, reducing the need for water exchange and minimizing environmental impact compared to traditional farming methods. The aim of the bachelor's thesis was to investigate how the implementation of a protein skimmer affects water turbidity and levels of fine particles in a RAS, and its impact on water quality, fish health, and welfare in Atlantic salmon. The thesis is based on methodological triangulation to gain insights and a deeper understanding of the use of protein skimmers in recirculating aquaculture systems. A comprehensive literature review was conducted to examine existing literature and research, in order to assess the expected effects of implementation of a protein skimmer. The results indicated that higher concentrations of suspended and dissolved particles can increase turbidity and water color, while also reducing the effectiveness of disinfection treatment methods such as UV and ozone. Fine particles and turbidity can have both direct and indirect effects on fish health. However, the study revealed conflicting research findings regarding the direct impact of suspended particles on fish health. The study concludes that the implementation of protein skimmers in recirculating aquaculture systems has proven to be an effective method for reducing turbidity and fine particles in the water. Due to limited literature and research, it remains unclear how turbidity and fine particles affect fish health and welfare in RAS facilities. Therefore, it is important to explore this in order to ensure optimal environmental conditions and contribute to the optimization of RAS as a sustainable and efficient method for farming of Atlantic salmon.

Purpose: The purpose of this thesis is to identify appropriate Production Planning and Control (PPC) methods in a Make to Order (MTO) manufacturing environment. This is done through two steps. First, the MTO environment needs to be defined. This narrows down the field of appropriate PPC methods, as well as highlights the characteristics of the environment in which the methods are to be applied. By looking at the variety in systems that has undergone review, these characteristics should be defined under two categories: complexity and dynamism. Complexity represents numeral values that are known, such as Bill of Material (BOM), number of routings, product mix (number of products), and number of converging or diverging routings. Dynamism represents numeral values that vary over time in a significant way, such as demand fluctuation, processing time variation, and rate of innovation (new product introduction). Using these environmental characteristics, PPC methods will be compared by how they perform in the different scenarios. Key PPC methods as suggested by Stevenson et al. (2005) are under consideration: MRP (ERP), Kanban, CONWIP, DBR (TOC), POLCA and WLC. How these methods perform in various scenarios relating to the environmental characteristics, and how the methods address the important performance issues found in the MTO industry relating to their competitiveness, will be compared in order to provide a guide as to which PPC method to choose. Design: A literature review will be conducted, identifying key literature that holds validity, both in terms of PPC methods and MTO environmental characteristics. In addition the Key Performance Indexes found in the MTO industry will be used as a base mark for PPC performance given the various manufacturing environments described. Findings: The MTO environment were found to include a number of definitions. High-Variety/Low-Volume production are for the most part some kind of MTO manufacturing. In addition, Engineer-to-Order (ETO) share a number of traits when compared to MTO, as the production part of the Customer Order Decoupling Point (CODP) is shared. Engineering and reengineering becomes part of the environmental factors (complexity and dynamism) that impact the applicability of a PPC method. Of the six key PPC methods in the MTO industry defined by Stevenson et al. (2005), four showed the most promise for optimal performance in the MTO environment identified. Kanban does not perform well in MTO other than as a support for a manufacturing line, and MRP uses pure push logic, commonly found in any MTO company that has yet to review their PPC. In certain scenarios push does perform better, at least when compared to the identified PPC methods. If complexity and dynamism reach very high levels, the variable inputs needed to build any of the other PPC systems are impossible to define. If the complexity and dynamism lie within acceptable levels, all four could be viable. WLC is the system that shows the most promise. This is because two other PPC methods share many traits with WLC, namely CONWIP and DBR. This lowers the barrier of implementation, and allows for a gradual maturing of the system, which can start out as a loose CONWIP/DBR, and over time increase the number of deciding inputs to become a WLC. POLCA is a stricter system than WLC (especially if a simple, loose CONWIP/DBR is used as a base), but does show great promise. Of the two systems, WLC handle dynamism better, whereas POLCA handle complexity better. Research limitations: There is severe limitations when studying PPC methods without a case study. Because the parameters of each manufacturing environment receives varying degree of attention in the reviewed literature, a case study would help pinpoint crucial environmental factors. It would also help in showing the actual functionality of the studied methods. Value: The thesis will hold value for companies that fall under the MTO category defined in the thesis, given that they need to select a PPC system to improve production performance, and address any performance issues they may have. Keywords: Production planning and control, kanban, CONWIP, WLC, POLCA, DBR, TOC, MTO, ETO, HVLV, customization