Eutrophication is of interest in the field of water quality. Eutrophic lakes, when used as sources for drinking water, can cause problems during the treatment process, for example algae blooms can clog filters, requiring more water and energy to be used during the cleaning and backwashing of the filters. Excess nutrient loading and eutrophication can also harm fish and aquatic life habitats. Certain species of algae and cyanobacteria can be toxic to humans as well. Since 1998, Dr. A. Woodruff Miller has collected water samples from 46 lakes and ponds in Yellowstone National Park. The Carlson Trophic State Index, the Vollenweider Model, the Larsen Mercier Model, the Burns Trophic Level Index, and the Naumann Trophic Scale were then used to assign each lake or pond to a trophic state classification (Oligotrophic, Mesotrophic, Eutrophic, and Hyper-Eutrophic). Of the 46 total lakes and ponds that have been tested over the past 14 years, five lakes are classified as slightly oligotrophic, implying that the waters are relatively clear and free from nutrient pollution. Of the 46 lakes, 19 are classified as slightly mesotrophic, mesotrophic, or strongly mesotrophic. These classifications imply that the waters are moderately clear and contain some nutrient pollution. Of the 46 lakes, 14 are classified as slightly eutrophic, eutrophic, or strongly eutrophic. This implies that the waters have high turbidity and nutrient content. Of the 46 lakes, 8 are classified as slightly hyper-eutrophic or hyper-eutrophic. These lakes are noticeable for their high algae content with very high nutrient content. These classifications are based on the most recent year sampled.

Over-fertilization of lakes happens when a large amount of nitrogen and phosphorus is added to the water. This has a negative impact on the water quality and the ecosystem since it often leads to massive phytoplankton growth, oxygen free bottom areas and fish dead for example. The purpose of this study was to investigate if, and how, the municipalities in Sweden work with the environmental objective “no over-fertilization” of lakes. The purpose was also to investigate if there is a difference between how municipalities in northern and southern Sweden work with the environmental objective “no over-fertilization” of lakes. The method used was a questionnaire, which was sent as a web-survey to all the 290 municipalities in Sweden. The result of this study indicates that most of the municipalities in Sweden work with the environmental objective “no over-fertilization” of lakes. Agriculture and wastewater seem to be the two largest sources that cause over-fertilization of lakes in both northern and southern Sweden. Although more than half of the municipalities in Sweden claim that they do not have enough resources to achieve the environmental objective “no over-fertilization” of lakes, which mostly depends on limited financials, personnel and expertise.

Accumulation of beach cast biomass on coastal zones around Gotland is an increasing problem that reduce the recreational value of beaches and cause environmental degradation of coastal environments. Beach cast was once regularly harvested on Gotland, as it was considered a valued biofertilizer, but as it seized to be used in combination with the eutrophication of the Baltic sea, beach cast accumulation has increased in scale. The use of beach cast as a resource for bioenergy and agriculture does not only provide important services that can replace the use of greenhouse gases and finite resources but can also mitigate eutrophication and increase the quality of coastal zones as nutrients are retrieved from the water. Macroalgae and seaweeds are hyperaccumulators of heavy metals which pose a challenge for the utilization of beach cast as a fertilizer. Especially cadmium, a heavy metal that is harmful for human consumption, is strictly regulated and limits the amount of beach cast that can be used for agriculture. This thesis has analysed the potential benefit of beach cast harvesting and three potential utilization strategies of beach cast; fertilizer to food crops, fertilizer to fast growing energy forest (Salix) and biogas production with digestate utilization. The result indicate that all strategies are possible and viable utilization strategies under certain conditions. Because of the complex and site specific factors that affect beach cast utilization, adapting strategies depending on the conditions and needs of the local coastal zones is required. Cadmium uptake is affected by a range of factors that can be controlled so that beach cast can provide nutrients and improve soil structure without contaminating the soil. Especially promising is the prospect of fertilizing Salix with beach cast as the cadmium absorption and growth rate of Salix enables large amounts of beach cast to be spread without risk for it accumulating in the soil. The cadmium contained within the Salix can later be removed from the environment entirely as it is collected from the ash when Salix is converted to bioenergy. Recent studies also indicate that food crops can be safely fertilized with beach cast without cadmium being transferred if specific crops are chosen. Cadmium uptake to crops can also be limited if specific beach cast with low cadmium content are used and if the beach cast is pre-composted with other substrates. Both for Salix and food crops its instead legal restraints on cadmium spreading that limits the use of beach cast. When abiding by the set cadmium restrictions, beach cast can only marginally supply the macronutrient requirement of the average food crop on Gotland. Biogas production and digestate utilization from beach cast provides many environmental benefits as clean renewable energy is generated that can replace fossil fuels and the nutrients contained in the digestate can be spread on arable land. From the conducted energy balance of the system on Gotland it was found that beach cast has theoretically good conditions to ferment beach cast. However, beach cast isn’t practically viable on Gotland because the substrate can’t compete financially with other available substrates and it requires costly pre-treatments. Regardless of which beach cast utilization strategy chosen, harvesting is concluded to have a positive effect on mitigating coastal eutrophication and beach and water quality. Although it cannot on its own mitigate a net nutrient loading to coastal zones in Gotland, harvesting easily available beach cast can reduce the nutrient loading to coastal zones on Gotland with up to 27 % and 4,5 % phosphorus and nitrogen respectively.

Recent urbanization of Utah Valley, Utah, has highlighted the impacts of anthropogenically-driven eutrophication of Utah Lake, which may lead to more frequent harmful algal blooms. To examine changes in trophic state, three freeze cores were taken from Utah Lake (Goshen Bay, Provo Bay, and near the Provo Boat Harbor) to examine the extent of eutrophication since European settlement. 210Pb and 137Cs chronologies were constructed for all three cores, although due to low supported 210Pb in the Provo Boat Harbor core, an additional pollen analysis was performed. Lower juniper pollen counts in addition to higher POACEAE (grasses and cereals) counts above 27 cm suggests that land clearance was taking place and horizons above this depth are post-1850s, when Utah Valley was settled. Chronologies in Goshen Bay and Provo Bay show that horizons above 40 cm are post-1950s. Hydrogen index (HI) values derived from RockEval pyrolysis were used to characterize the organic matter in the cores. Material from all three cores show an up-section increase in HI, consistent with the increasing deposition of algal matter. δ15NATM and δ13CVPDB isotope ratios were also measured for organic matter in the cores. 15N shows enrichments upward in the cores, combined with a depletion in 13C across all three. δ15NATM values suggest increasing anthropogenic influence with time that may contribute to algal blooms and eutrophication. δ13CVPDB ratios become depleted towards the top of the core showing a change in the lake’s ecology which may be due to the introduction of invasive Phragmites. X-Ray diffraction (XRD) analysis was used to analyze mineralogical differences. Eastern Utah Lake and Goshen Bay cores contain 70-80 % calcite, 10-15% quartz and 10% dolomite. Provo Bay samples contain 50-60% calcite, 20-30% quartz, and 10% dolomite. The dominance of calcite suggests that the sediment is dominated by endogenic minerals, albeit with a greater contribution of detrital minerals in Provo Bay. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for elemental analysis. Concentrations of phosphorous and trace metals increase in the younger sediment of all three cores, suggesting greater anthropogenic influence on lake water with time. Overall, the rise in HI, P, trace metals, and 15N since European settlement suggests that the lake has become more eutrophic and anthropogenically-impacted in the last 170 years. This highlights the importance of understanding human impacts on water quality to help mitigate any future damage to Utah Lake’s ecology and waterways.

Acid rock drainage (ARD), caused by the oxidation of sulphide bearing minerals, continues to be an environmental impact of both closed and operational mines, leading to waters with low pH values and high metal concentrations (Park et al., 2019). A potential treatment method for ARD is controlled eutrophication, where algae growth is stimulated in the water and metals are accumulated within the algae cells or sorbed to the outside of the cell walls (Samal et al., 2020). The aim of this study is to determine if the addition of wood ash to acidic mine waters can increase the pH, stimulate algal growth, and lower metal concentrations in the water. Two types of wood ash, as well as KNO3 and KH2PO4 were utilized for this study, along with three water sample types: neutral (pH of 7.0) water from Åkerberg pit lake, acidic (pH of 5.7) water from Maurliden mine site (Maurliden East), and very acidic (pH of 2.3) water from Maurliden mine site (Maurliden West). Two experiments were performed, Experiment I (Exp. I) involved a one-time addition of wood ash and KNO3 to samples from each of the three sites, and Experiment II (Exp. II) involved a feeding style ash addition where ash was added every five days to samples from Åkerberg and Maurliden East. Exp. II also included one sample set where artificial nutrients only (KNO3 and KH2PO4) were added to Maurliden East samples. Samples were placed inside of a climate chamber to provide daily irradiation and pH, electrical conductivity (EC), and fluorescence signal measurements were taken daily. Additionally, absorbance samples and O2 saturation measurements were taken daily for Exp. II. At the end of each experiment, samples were sent to an accredited laboratory for elemental analysis and chl-a analysis.  Algal growth was observed in Exp. I in Åkerberg samples only, and in Exp. II in Åkerberg samples and in Maurliden East samples with artificial nutrient additions only. The algal growth rate was similar in both experiments; however, Exp. II yielded a higher concentration of chl-a than Exp. I. Precipitates were observed in all samples in both experiments, including in control samples. pH results cannot confirm the ability of the wood ash to increase the pH in the samples from Maurliden East or West, and metal concentration decreases in these samples are most likely due to precipitation reactions. Metal concentration decreases in Åkerberg samples could be due to precipitation reactions and/or algal uptake.

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Eutrophication, caused by phosphate, can be detrimental both for the aquatic environment and human health. This research aims to provide deep knowledge about the adsorption properties of low-cost Fe/Mg layered double hydroxide modified biochar (LDHBC) for removal of phosphate from aqueous solution. Firstly, Fe/Mg layered double hydroxide (LDH) was synthesized by mixing FeCl3 and MgCl2. 6H2O salts in water, followed by NaOH treatment (coprecipitation method). For LDHBC, FeCl3, and MgCl2. 6H2O salts were dissolved in water, and Douglas fir biochar was added to the salts mixture to make a slurry, followed by NaOH treatment. The surface chemistry and elemental composition of both adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, and TEM. Adsorption ability of LDH and LDHBC was studied by pH effects, kinetics, and the highest capacity for the analyte.

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Man-made mixing in shallow lakes will resuspend bottom sediments and increase phosphorus concentration in the water body. The increase in phosphorus content may affect the lake productivity. During the course of this study, a better understanding of the water-sediment-phosphorus relationships of some shallow lakes in Central Florida was attempted. Column studies and batch experiments were used to investigate the effect of mechanical mixing on the release of phosphorus from bottom sediments collected from Lake Claire and Jessup. The particle size distribution and density distribution of the bottom sediments were studied and the release of phosphorus from each fraction was measured. The results indicated that dissolved oxygen, turbidity and phosphorus content in the water column increased by mechanical agitation. The total phosphorus released from smaller size particles seemed to be higher than phosphorus released from larger particles. Also, the least and highest density sediment particles showed the highest release of phosphorus.