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Eutrophication is a global problem that has a major impact on aquatic ecosystems. Over the past 50 years, the nutrient content of lakes and streams has increased as a result of urban development and agricultural sources. It can cause health problems for both humans and animals through direct contact or when consumed. In addition, it can result in the extinction of aquatic organisms. By studying the topography, soil chemistry, hydrology and human impact of areas, we can understand how nutrients are transported from their sources of origin to surface water, where they increase nutrient content. Understanding this is crucial to identify and prioritise areas that require action to reduce the effects of eutrophication. The purpose of this study was to trace potential sources of dispersion of nutrients to the surface water through analysis of these. The site chosen for the study was the area of Tvärålund where the stream Sjöbäcken and lake Tväråträsket are located, where 11 sampling points were also placed. These had the purpose of proving any emissions from ancillary activities. The results indicate that only one of the selected sampling points was contaminated from active point sources (individual sewers) while the remaining points showed a constant increase supported by a linear relationship between distance from the reference point and measured concentration.

The primary objective of this study was to determine the salinity effect on nutrient release and the denitrification rate in a sediment-water system. To accomplish this objective, bench-scale microcosm studies of York River sediments and Occoquan Reservoir sediments were conducted. Seawater and freshwater were mixed in various ratios to simulate seasonal, salinity-varying environments in the Chesapeake Bay and its tributary estuaries. Experiments were conducted under aerobic, anaerobic, and anoxic conditions. The results showed that high salinity can cause flocculation of particles and result in lower concentration of phosphate under aerobic conditions, but the flocculation effect was not obvious under anaerobic conditions. The release of ammonia was governed by the salinity; the increasing salinity accelerated the release of ammonia by ion exchange. The denitrification rate under anoxic conditions in the system was not influenced by the salinity. / Master of Science

The effects of temperature and mean cell residence time (MCRT) on processes involved in biological nitrogen and phosphorus removal were investigated by operating pilot-scale continuous-flow reactors over a range of temperatures and MCRITs. Two systems were operated as high-rate University of Cape Town (UCT) biological nutrient removal (BNR) processes. A third system was operated as a conventional, fully aerobic activated sludge system for comparison. Less aerobic volume was needed to achieve complete nitrification in the BNR system than in the conventional system when temperature and MCRT conditions were suitable for complete nitrification. This occurred at 15 d MCRT and temperatures from 10 to 20 °C., and at 5 d MCRT and 20 °C. However, the BNR system was more susceptible to nitrifier washout at 5 d MCRT and temperatures of 10 and 15 °C. Although less volume was needed for complete nitrification in the BNR system, specific nitrification rates and the degree of nitrification were equal in the two systems when compared on the basis of aerobic MCRT. This phenomenon occurred because the MLVSS concentrations were higher in the aerobic zone of the BNR system than in the conventional system for the same organic loading and total MCRT. Nitrification and denitrification rates were a function of MCRT and temperature, with temperature having a greater effect at lower MCRTs. Batch experiments showed that anoxic uptake of phosphorus occurred, although at a much lower rate than aerobic uptake. Biological phosphorus removal was adversely affected by colder temperatures. Operation of the BNR process at the lowest MCRT which provided complete nitrification prevented washout of phosphorus removal organisms, and provided the best combined nitrogen and phosphorus removal when phosphorus removal was COD-limited. Higher MCRIs were optimal under P-limiting conditions. Anaerobic stabilization ranging from 8% to 27% was measured in the BNR system, and was a function of temperature at a 15 d MCRI. A mechanism for anaerobic stabilization was proposed. Yield coefficients for the BNR and the conventional system were equal and were 0.41 mgVSS/mgCOD. The decay rate in the BNR system, 0.063 d⁻¹, was lower than the decay rate in the conventional system, 0.110 d⁻¹. This resulted in higher MLVSS concentrations in the BNR system. / Ph. D.

Seaweed production systems are necessary to fill a product demand in multiple sectors whilst contributing to the bioeconomy. The multiple seaweed qualities drive the research for sustainable seaweed production worldwide. The main studies of seaweed production consist of life cycle assessments, where cradle-to-gate analyses have been calculated. However, these assessments have had incomparable results because of the various methods used. Therefore, this thesis utilized the life cycle inventories of six previously made life cycle assessments of brown seaweed and recalculated these concerning three key environmental impact categories – Global warming potential, Freshwater Eutrophication, and Marine Eutrophication. This was done by collecting and recalculating the six different inventories to the same functional unit and then assessing the environmental impacts of the recalculated inventories. The results showed that the life cycle impact assessments of brown seaweed production varied, yet the most impacts could be seen during the cultivation stage of the life cycle, mainly due to the plastics used within the system. The variations in the results are a consequence of the various data resources used, the design and location of the production systems, and the goal and scope of the reports. This thesis also demonstrated that a replication of life cycle assessments includes several obstacles, questioning the scientific method of LCA, for example, lack of transparency and deficiency in reporting methods and data. / Globalt sett minskar tillgänglig landareal för odling, samtidigt som efterfrågan för ekologisk och hållbart producerade produkter ökar. Det här har lett till att fler sektorer söker sig till det som kallas Blue growth. Blue Growth är användandet och utnyttjandet av marina miljöer för produktion, inom olika sektorer, som gynnar både det marina ekosystemet och bioekonomin. Algodling är ett exempel på en produktion som gynnar bioekonomin. Alger är en alltmer efterfrågad produkt, som redan används i flertal sektorer, så som läkemedels-, textil- och livsmedelsindustrin. Det är främst algernas egenskaper som gör att de är attraktiva att kultivera, tillsammans med strävandet av en hållbar produktion.  Den här masteruppsatsens syfte är att jämföra tidigare livscykelanalyser som har gjorts på produktionen av brunalger. Livscykelanalyser är ett verktyg inom industriell ekologi som mäter en produkts påverkan genom alla livscykler. Resultatet ges i ett numerärt värde, och är summan av produktens påverkan inom den specifika kategorin. Det denna rapport har gjort är att räkna om livscykelanalyser som tidigare har gjorts på brunalger, för att få jämförbara resultat. Syftet med rapporten är därför att granska och utvärdera publicerade livscykelanalyser av odlade brunalger. Tre delmål sattes upp vilka var:  Bedöma skillnader och likheter i de olika livscykelinventeringarna. Studera och utvärdera skillnaderna mellan den beräknade livscykelanalysen av brunalger till samma parametrar. Utvärdera processen för att räkna om redan gjorda livscykelanalyser.  Fem rapporter valdes ut, varav sex stycken livscykelinventeringar sammanställdes, eftersom en rapport innehöll två olika livscykelanalyser. Studien började med, att sammanställa all tillgänglig data, samt att räkna om kvantiteterna i inventeringarna. Därefter räknades alla sex livscykelanalyser om, med samma förutsättningar och metod. Detta innebar att resultatet som fanns i de slutgiltiga summorna kunde jämföras och diskuteras. De tre kategorierna som livscykelanalyserna mättes mot var: potentiell global uppvärmning (kg koldioxidekvivalenter), övergödning i sötvatten (kg fosfor) och marinövergödning (kg kväve).  Det som jämförelsen visade var att alla omräknade livscykelanalyser hade olika totalbelopp i de tre kategorierna. Likväl kunde kultiveringssteget anses vara det livscykelstadie som har störst påverkan på brunalgodling, främst på grund av plastanvändningen.  På grund av de olika påverkningsgraderna som rapporterna hade, fanns det många faktorer som diskuterades kring likheterna och skillnaderna. Först och främst kan datainhämtningen ha en stor påverkan på tilliten och förtroendet på resultaten. För det andra skildrades inventeringarna på olika sätt, varav både kvantiteter och materialvalet skildes åt. Dessa skillnader kan bero på den geografiska placeringen av produktionen, men även på hur utformningen av produktionen såg ut.  Det som studien även visade var att en omberäkning på livscykelanalyser var svår att utforma utan att flertalet antaganden gjordes på grund av avsaknad av data. Processen att räkna om redan gjorda livscykelanalyser kan därför anses problematisk, vilket gör att livscykelanalys som vetenskapligt verktyg kan ifrågasättas om inte replikering av resultat kan göras med stor säkerhet.

Made available in DSpace on 2014-12-17T15:03:33Z (GMT). No. of bitstreams: 1 AndrieviskGPS_DISSERT.pdf: 1181960 bytes, checksum: 3416b1e3bd91514fea43dc2c94f227dc (MD5) Previous issue date: 2014-03-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The phytoplankton growth is dependent of several abiotic (nutrients, temperature) and biotic (predation by zooplankton) variables. In this work, a mathematical model was developed in Stella software to understand the planktonic dynamics of Extremoz Lagoon (RN) and to simulate scenarios of different environmental conditions. Data were collected monthly at two points of the lagoon. The state variables are phytoplankton and zooplankton and forcing variables are nitrogen, phosphorus and temperature. The results show that: a) the model are well coupled, especially when some constants assume different values; b) simulated nutrient concentrations reduction decreases phytoplankton biomass, but the increase of nutrients does not stimulate the growth; c) changes in the temperature does not change the phytoplankton biomass; d) changes in zooplankton biomass affect directly and reduces the phytoplankton, indicating a topdown control mechanism; e) changes in the nutrient concentration modified the biomass of zooplankton suggesting a rapid flow of energy between nutrients, phytoplankton and zooplankton and a ecosystem likely arranged in an inverted pyramid (higher concentration of zooplankton than phytoplankton) / O crescimento fitoplanct?nico ? dependente de uma s?rie de vari?veis abi?ticas (nutrientes, temperatura, luz) e bi?ticas (preda??o por zoopl?ncton e outros fitoplanct?fagos, bact?rias que provocam lise celular no fitopl?ncton). Neste trabalho, um modelo de compartimentos foi desenvolvido no software Stella para entender a din?mica planct?nica da Lagoa de Extremoz (RN) e simular diferentes cen?rios de altera??es em importantes vari?veis ambientais como fitopl?ncton e zoopl?ncton. As medi??es foram realizadas mensalmente em dois pontos da lagoa. As vari?veis de estado s?o fitopl?ncton e zoopl?ncton e as for?antes s?o nitrog?nio, f?sforo e temperatura. Os resultados mostram que: a) o modelo se ajusta bem aos dados, especialmente quando algumas constantes assumem diferentes valores; b) simula??es de redu??es das concentra??es de nutrientes diminuem a biomassa fitoplanct?nica, mas o aumento dos nutrientes n?o favorece o crescimento; c) altera??es na temperatura n?o modificam a biomassa fitoplanct?nica; d) modifica??es na biomassa de zoopl?ncton afetam diretamente e consideravelmente o fitopl?ncton, indicando um mecanismo de controle top-down; e) altera??es nas concentra??es de nutrientes modificam a biomassa do zoopl?ncton sugerindo um r?pido fluxo de energia entre nutrientes, fito e zoopl?ncton e um prov?vel ecossistema arranjado em pir?mide invertida (maior biomassa de zoopl?ncton do que fitopl?ncton)

Cette thèse de Doctorat examine le réseau trophique estuarien lié aux herbiers à zostères, Zostera noltii et quantifie le rôle trophique des consommateurs de la macrofaune benthique, dans deux zones intertidales de l’estuaire du Mondego, à différentes périodes de 1993 à 2008. Elle s’intéresse spécifiquement (i) à l’incorporation de l’azote issu des activités humaines, en considérant l’assimilation d’azote comme un indicateur de l’eutrophication et (ii) au rôle des zostères dans le réseau trophique benthique. Six modèles ont été développés afin d’analyser les effets, (i) d’un enrichissement en nutriments, (ii) des mesures de mitigation, et (iii) d’une inondation centennale, sur les propriétés du réseau trophique benthique estuarien. La présence de Z. noltii change peu la structure du réseau trophique planctonique, soutenu en partie par la matière organique particulaire et supporte principalement des poissons comme prédateurs. Les autres consommateurs montrent une grande variabilité de signature isotopique, ce qui suggère qu’ils peuvent changer de régime alimentaire en fonction des changements de l’environnement. En revanche, les δ13C et δ15N des producteurs et consommateurs de l’estuaire du Mondego montrent très peu de variation saisonnière, malgré une saisonnalité météorologique marquée, ainsi qu’une forte variation saisonnière des paramètres de la colonne d’eau (apports en sels nutritifs et concentration en chlorophylle a). Les modèles à l’état stable montrent enfin que la structure trophique de la communauté benthique de l’estuaire du Mondego est affectée différemment par chacun des évènements particuliers étudiés. / This dissertation examines the estuarine food web related to the eelgrass Zostera noltii and quantifies the ecological trophic role of benthic macrofauna consumers, in intertidal areas of the Mondego estuary, covering different time periods from 1993 to 2008. It specifically focuses (i) on the incorporation of the nitrogen derived from human activities, considering the N uptake as an eutrophication index, and (ii) on the role of the eelgrass in the benthic food web. In addition, six mass-balanced models were developed to assess the effects of (i) a period of nutrient enrichment, (ii) the implementation of mitigation measures, and (iii) a centenary flood, on the benthic estuarine food web properties.

This study determined effects of addition of secondarily treated municipal wastewater effluent on an urban reservoir receiving system. Monthly water quality monitoring of the receiving reservoir and the wastewater, chemical analysis, and monthly laboratory algal assays, were conducted from September 1984 to September 1985. The nutrient status and algal growth potential of the receiving water and the wastewater confirmed the biostimulatory properties of the wastewater. Field validation studies were conducted using limnocorrals. Tertiary treatment of the wastewater using chemical coagulation precipitation with alum and ferric chloride reduced phosphorus concentrations in the wastewater to levels which supported significantly less algal biomass than untreated wastewater. These studies indicate ferric chloride to be a more effective coagulant for phosphorous removal alum.