Abstract The subject of the study was to search and test restoration measures for the most common physical habitat degradations in Finnish rivers. Methods for constructing nursery and spawning habitats for salmonid fishes were tested in small rivers dredged for timber floating in the Iijoki watercourse. Physical habitat modelling was used to simulate the effects of restoration measures to the hydro-physical conditions and potential fish habitats. The rehabilitation of the river bed and the placement of boulder structures, especially large boulder dams, made the rapids spatially more complex and increased the availability of potential physical habitat for brown trout (Salmo trutta). The physical habitat model was applied in the river Siikajoki to estimate the impacts of flow regulation patterns on the physical habitat quality. No single flow event causing a bottle-neck effect on the potential habitat suitable for brown trout was found. In a sensitivity analysis of habitat modelling, modifications of the suitability criteria appeared to have a major influence on habitat suitability for young brown trout. The applicability of low reefs and narrow side channels for fish habitat improvement was studied, using the large river impoundment of Oulujoki as a test area. Limited validation experiments of the model results were carried out on the basis of fish telemetry experiments and observations by local rod fishermen. The restoration measures appeared to diversify the channel structure and increase sheltered lateral habitats for grayling (Thymallus thymallus). Habitat structure and fish populations of seven small forest streams and two modified streams were surveyed using visual evaluation and electrofishing studies. None of the studied streams was found to be in pristine condition in all of its reaches. Brown trout was the most abundant species in most of the study streams. In most streams the brown trout distribution correlated positively with substrate size. The accumulation of fine materials on the stream bottom due to forestry operations was estimated to be the most harmful human impact on the studied streams. Some restoration suggestions were made for each of the streams.

The water level at Hjälta power station in Faxälven varies depending on the water flow that passes through the power station. The varying water level causes head losses, lesser energy generation and loss of income. The varying water level is caused by a short but narrow and shallow part of the river, known as Klockarforsen. To increase the water flow and decrease the resulting head losses, it is possible to dredge the stream bed in Klockarforsen in order to achieve a greater depth.  By using a sonar to map the bathymetry in Klockarforsen, it has been possible to create a model of this part of the river. The model has been constructed and processed in ArcGIS and HEC-RAS, in order to examine how a dredging would affect the water level, head losses, energy generation, income and retention water levels.  The results show that a dredging to a depth of four or six meters could raise the water level and the head height at Hjälta power station with an average of 0.32 and 0.41 meters, respectively. During the period between 2014-2019, 1.11-3.84 GWh more energy would have been generated annually if Klockarforsen had been dredged. Which means that the income for the power station would have increased by between MSEK 0.39-1.3 per year. The increased energy generation and income are considerable, but in terms of how much energy and income is generated annually, the figures are more modest. The energy production and income increase by between 0.13-0.3 percent annually.

This master’s thesis is concerned about the flow of hydro-mixture in pipelines. In the first part, I am reviewing the characteristics of disperse systems, pumps and pipelines used in hydro-mixture transportation. Slurry pumps and polyethylene HDPE pipelines receive an extra attention. In the second part, I am working with data obtained from the co-operation with the PROGROUPE Sediment Removal company. These data were measured during revitalization of the water dam Gabčíkovo. In the next step, I use the data to suggest the required characteristic for the slurry pump for pump station in project of revitalizing Borovoe lake, situated in Kazakhstan.

Corals are frequently exposed to elevated turbidity and deposited sediment caused from coastal construction, dredging, and/or beach renourishment. This study addresses the effects of turbidity and deposited sediment on the survival and growth of newly settled and 6-week-old Orbicella faveolata recruits and disentangles the effects of turbidity and deposited sediment. We conducted two experiments in which newly settled coral recruits were reared in one of ten different turbidity and deposited sediment treatments for five weeks (0 NTU/ 0 mg cm-2, 3.4 NTU/ 0 mg cm-2, 8.2 NTU/ 0 mg cm-2, 16 NTU/ 0 mg cm-2, 29.1 NTU/ 0 mg cm-2, 0 NTU/ 0 mg cm-2, 3.4 NTU/ 27.7 mg cm-2, 8.2 NTU/ 50 mg cm-2, 16 NTU/ 101 mg cm-2, 29.1 NTU/ 220 mg cm-2). The highest turbidity treatment in the absence of deposited sediment (29.1 NTU/ 0 mg cm-2) had the best survival, suggesting that turbidity in the absence of sediment is beneficial to coral recruits, as it decreases harmful light levels. However, when recruits were exposed to both turbidity and deposited sediment, representative of normal coastal construction conditions, high turbidity when coupled with deposited sediment (16 NTU/ 101 mg cm-2 and 29.1 NTU/ 220 mg cm-2) had negative effects on coral recruits. Based on the results from the first experiment, the experiment was repeated with six-week-old symbiotic recruits for two weeks to determine if the sensitivity to light and benefits of high turbidity were related to the presence of symbionts. Six-week-old recruits also had the highest survival in the highest turbidity treatment, suggesting that light sensitivity by coral recruits is not dependent on the presence of symbionts within the first six weeks post-settlement. While the low light associated with turbidity increases recruit survival, turbidity is a proxy for deposited sediment, which has negative effects on coral recruits. Based on the results from this study, regulations should prevent turbidity from exceeding 8.2 NTU to prevent excessive deposited sediment on coral reefs, and its deleterious effects on corals.

It has been common in forestry and agriculture to drain waterlogged areas through ditching in order to cultivate them. The ditches that drain water are usually connected to some watercourse, such as a river. When the water flow of the river decreases and becomes more still, particles will settle and fall to the bottom of the water body and form sediment. If there is an increasing amount of nutrients and metals transported with the water, it could affect the water quality negatively, since an increased amount of nutrients could result in eutrophication and many metals are toxic in high amounts. In the Sangis River there is an increased amount of sediment deposited at the mouth of the river and inside the estuary, which has resulted in the river and the estuary becoming shallower. The origin of the deposited sediments is believed to partly be from ditching. The residents of the village of Sangis have said that it is difficult to cross the estuary by boat because of the deposited sediments, therefore, their wish is for a channel dredged in the Sangis River and its estuary that they can use. The main aim of this master's thesis was to analyse the geochemical status of the surface water and the sediment in the estuary of the Sangis River and to give recommendations for future actions preventing sedimentation of the river channel. The analyse of the geochemical status of the sediment was achieved by sampling six sediment- cores in the estuary and analysing for different parameters. The analyse of the geochemical status of the surface water was achieved by comparing the water quality regarding metal concentrations in the estuary with other nearby rivers and classifying the concentration of phosphorous in the estuary, to determinate if there was an ongoing eutrophication. The following analyses were conducted for the sediment-cores: Element distribution were analysed with P-XRF, pH and electrical conductivity were measured and loss on ignition was also calculated trough combustion of the sub-samples. The results showed for the P-XRF that the dominating main elements were iron, sulfur, calcium and potassium. Iron and sulfur were correlated to each other in all profiles and had a peak between 20-35 cm in the sediment. This indicated that there could be formation of iron sulfides at that depth. Therefore, sub-sample 4.D was analysed with SEM-EDS instrument and framboidal pyrite (FeS2) was detected in the sample. The results from the pH and conductivity showed that the pH-value varies greatly both with depth and between the sediment cores. However, for the conductivity it could be seen how it peaked at around 20-35 cm in all profiles, with the highest EC-value in profile 4. It could be concluded that the surface water in the estuary contains elevated concentrations of copper and that there is an ongoing eutrophication as well. Due to the eutrophication, it has most likely resulted in an increased amount of aquatic plants during the summer. The increased amount of organic material has probably resulted in oxygen-free bottoms, since all the oxygen has been consumed when the organic material has been decomposed. The formation of framboidal pyrite shows that the redox ladder has reached the two last steps, since framboidal pyrite (FeS2) consists of reduced sulfur and dissolved iron and is formed during anoxic conditions. Reduced sulfur forms when sulfate is reduced in order to oxidize organic matter and dissolved iron forms when iron-oxide hydroxides are reduced in order to oxidize organic matter. If dredging is carried out in the Sangis river and its estuary, oxidation of framboidal pyrite will occur, this could result in formation of acid and leachate of metals that were previously bound to framboidal pyrite. The consequences if it leaches into the river and the estuary is that it creates an acidic environment with elevated metal concentrations, where marine life would find it hard to live. The extent and impact of leached acidity and metals needs to be studied further.

Sverige har en stor miljöskuld i form av fiberbankar fulla med miljöfarliga restprodukter från den pappers- och massaindustri som har definierat stora delar av svensk industri. Stora delar av östkusten samt flertalet sjöar fortsätter påverkas av dessa fiberbankar som kontinuerligt släpper ut miljögifter allt eftersom de eroderas av vågor eller då det organiska materialet bryts ned. Att minska dessa utsläpp av miljögifter är ett måste. Ett alternativ för att ta vara på de gamla restprodukterna är att muddra bort det varsamt för att sedan processera det på land. En sugenhet har tagits fram i ett tidigare examensarbete som minimerar spridning av sedimenten vid muddring. Syftet med detta projekt är att konstruera en flotte som möjliggör användandet av den tidigare framtagna sugenheten utan att onödig upprörning och spridning av sediment riskeras. En potentiell källa till upprörning är då sugenheten kommer i svängning pga. okontrollerade rörelser på flotten som uppstår via vågpåverkan. En litteraturstudie över olika stabiliseringsmetoder gjordes och därefter togs ett flertal koncept fram som sedan utvärderades mot kravspecifikationen. Det koncept som sedan vidareutvecklades var en flotte som baseras på SWATH teknik samt med så kallade ”Heave plates”, horisontella plattor under vattnet som skapar ett hydrodynamiskt motstånd Flotten som tagits fram baserar sig på uppdragsgivarens, Teknikmarknad, tidigare flotte för muddring av organiska sediment. En uppskattning av konceptets kostnad gjordes sedan genom skapandet av en komponentlista där för konceptet nödvändiga delar listades tillsammans med pris. Det framtagna konceptet är autonomt, relativt billigt, kräver minimalt med underhåll och minimerar risken för spridning av miljöfarliga ämnen vid muddring. / Sweden has a large environmental debt in form of underwater fibre deposits, full of leftover chemicals from the pulp and paper industries that has defines large parts of early Swedish industry. Large parts of the east coast and several lakes continues to be affected by these deposits that continuously release environmentally hazardous materials when the deposits are eroded by waves or the organic material breaks down. To slow down these emissions is a must. One alternative is to carefully dredge the material away with purpose-built equipment to later process it on land. In an earlier thesis, a dredgehead was developed that minimize the spreading of material during dredging. The purpose of this project is to develop a barge that enables the use of the earlier developed dredgehead without increasing the risk of spreading of sediment. A potential cause of spreading is if the dredgehead would start swinging due to uncontrolled motions of the barge caused by waves. A literature study was conducted to find different stabilizing methods and several concepts where developed. The different concepts were evaluated based on the requirement specification. The superior concept was a SWATH based design with added Heave plates to increase the hydrodynamic resistance. The barge is based on a previous barge developed by the stakeholder, Techmarket, for low flow dredging of organic sediment. An estimate of the concept added cost was done through a component list where the necessary parts were listed together with the price. The proposed concept is autonomous, demands minimal maintenance and minimizes the risk of spreading of hazardous materials while dredging.

Massa- och pappersindustrin i Sverige har genom åren skapat en stor mängd restprodukter i form av pappers- och träfiber och rester av processkemikalier från produktionen. Vidanläggningar på Sveriges östkust deponerades dessa ofta rakt ut i havet där fiber ackumulerats genom åren till fiberbankar. Ett sätt att hantera dessa ansamlade utsläpp är via muddring, d.v.s. att avlägsna sedimentet från vattnet för att hantera det på annat håll. Syftet med detta projekt är att konstruera ett system för att muddra fiberbankar via en autonomfarkost. Ett flertal koncept genererades för att lösa olika delar av problemet och dessa utvärderades med Pughmetoden för att välja den bästa lösningen. Ett koncept utvecklades med en impeller som river upp sediment innesluten i en kon från vilken sedimentet pumpas vidare, där pumpen även driver impellern. Två vinschbaserade delsystem för att förflytta konen i vertikal- och horisontalled konstruerades. CFD-simuleringar och hållfasthetsberäkningar utfördes för att dimensionera komponenter och även egenfrekvensanalys för att säkerställa att impellern inte kan excitera någon egenfrekvens hos systemet. Det färdiga konceptet har fördelen jämfört med befintlig teknik att det är autonomt och anpassat för muddring av fiberbankar och inte bara organiskt bottensediment. Det behöver inte hellersupportsystem för att förhindra spridning av sediment som virvlas upp under drift. / The wood and paper industries in Sweden have through the years created large amounts of waste in the form of wood and paper fibers with residual process chemicals. Facilities on the east coast of Sweden often dumped these waste products straight into the ocean, where fiber was accumulated into fiber banks over the years. One way of dealing with these deposits is through dredging, i.e., removal of the pollutant from the water and processing it elsewhere. The goal of this project is to design a system for dredging of fibrous sediment via anautonomous vessel. Several concepts were generated to solve different parts of the problem. These concepts were evaluated using the Pugh method to find the best solution. A concept was developed using animpeller to tear up sediment enclosed in a cone from which the sediment was pumped up fromthe ocean floor. The pump is also the power source of the impeller. Two winch-based subsystems for vertical and horizontal movement of the cone were designed. CFD simulations and solid mechanics calculations were performed to dimension critical components, as well as modal analysis to ensure that the impeller cannot excite any eigenfrequency in the system. The finished concept has the advantage compared to existing technology that it is autonomousand adapted for dredging of fiber banks instead of organic sediment. It does not need separate support systems to prevent the spread of suspended sediment in the water during operation.

The state of Georgia has two large ports that are accessed by way of navigable entrance channels. One of these ports is located in Brunswick, Georgia, and is maintained by the United States Army Corps of Engineers via periodic dredging. Sediments removed from the channel are typically pumped several miles offshore of Brunswick and placed in dredged material mounds, thus removing the sediment from the littoral cycle. This offshore placement, while being the most economically viable method, often negatively impacts the sediment budget of the coastal region and causes erosion downdrift of the channel, specifically along Jekyll Island. Onshore placement of the dredged material is not feasible due to increased associated costs and the high fraction of fines present in the material; thus, nearshore placement is a potentially viable alternative. Nearshore placement could possibly reduce erosion rates and provide protection to property from waves and storms. The USACE initiated a thorough field data collection campaign in 2002 to study the possibility of beneficial placement of dredged material. The author analyzed the existing data to predict the rate and direction of sediment movement away from an existing dredge mound. These predictions are then compared to bathymetric survey data in an effort to validate the results and methodologies used for sediment transport predictions. The ultimate goal is to use the results of this study along with numerical models currently being developed by the Corps to assess the possibility of sediments being transported toward the shore thus re-entering the littoral cycle and providing a benefit to the coast of Georgia.

Le dragage de sédiments marins produit des millions de tonnes de déchets chaque année qu’il faut gérer durablement. Les deux sédiments étudiés, conservés dans des conditions anoxiques sous eau (sédiment brut), et oxiques soumis à l’altération naturelle (sédiment vieilli), présentent une contamination élevée en cuivre, plomb et zinc prépondérante surtout dans les fractions fines. Des phases réactives ont été identifiées telles que sulfures et matière organique, auxquelles le cuivre et le zinc sont en grande partie liés. Un dispositif expérimental innovant couplant un test de consommation d’oxygène à une colonne de lixiviation a été développé ; il a permis de mettre en évidence la réactivité des sulfures encore présent dans le sédiment vieilli malgré les conditions de stockage à l’air ambiant. La composante biologique a été étudiée également, à travers un test qualitatif mesurant l’impact des bactéries sulfo- et ferrooxydantes sur les paramètres pH et Eh des sédiments. Malgré l’importante concentration en carbonates conférant un pouvoir de neutralisation élevé, la communauté des bactéries neutrophiles sulfooxydantes a été capable d’abaisser le pH jusqu’à 4,5 – 5 unités. Cette réactivité a été contrôlée en soumettant les sédiments à un traitement de stabilisation-solidification avec des liants hydrauliques. L’évaluation environnementale par des tests cinétiques en mini-cellules d’altération et des tests de lixiviation en monolithe a démontré la bonne stabilisation des éléments métalliques pour les deux sédiments. Leur valorisation en mortiers cimentés a donc été envisagée. L’étude de la résistance mécanique de la substitution du sable par les sédiments entiers a montré la mauvaise résistance mécanique. En revanche, après application d’un traitement d’enlèvement de la fraction fine contaminée, la résistance s’est montrée satisfaisante pour des applications non-structurantes et constitue ainsi une filière de traitement et de valorisation pertinente dans la gestion de sédiments. / Millions of tons of sediments are dredged every year leading to a need for a sustainable management. Both studied sediments, stored in anoxic conditions under a layer of water (raw sediment), and in oxic conditions submitted to natural weathering (weathered sediment), showed high contamination of copper, lead and zinc, concentrated mainly in the finer fraction. Reactive phases such as sulfides and organic matter were observed, with which copper and zinc are partially linked. An innovative experimental set-up coupling an oxygen-consumption test with a column leaching test has been developed; this set-up highlighted the sulfides reactivity which is still occurring in the weathered sediment, despite years of natural aging. The biological component of this reactivity has been also studied, through a qualitative assessment of the impact of iron- and sulfur-oxidizing bacteria on pH and Eh of sediments. Although high amount of carbonates responsible for important neutralization potential were detected, bacterial community of neutrophilic sulfur-oxidizing bacteria has been able to lower the pH until 4.5 – 5 units. This reactivity is controlled by submitting both sediments to a stabilization/solidification treatment with hydraulic binders. Environmental assessment with kinetic test in weathering cells and monolithic leaching test demonstrated that trace metals appear well stabilized for both sediments. Thus, their valorization in cemented mortars has been assessed. When total sediments were fully substituted to sand, they showed poor mechanical strength. However, when a sieving treatment for removing of the fine contaminated fraction was applied, the sediments mortars revealed good mechanical strength for use in non-structural applications. This research confirmed thus that the reuse of the coarser fraction of a marine sediment, raw or weathered, offered an efficient and interesting way of treatment and valorization.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management