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Laboratory Evaluation of Internal and External Nutrient Removal to Control Algal Bloom in Eutrophic Lakes
Başlık:
Laboratory Evaluation of Internal and External Nutrient Removal to Control Algal Bloom in Eutrophic Lakes
Yazar:
Sadeghi, Sepideh, author.
ISBN:
9780355975406
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (127 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Guanghui Hua Committee members: Suzette Burckhard; Christopher Schmit; Cheng Zhang.
Özet:
Eutrophication is one of the most widespread water quality problems in lakes and reservoirs. Frequent cyanobacterial blooms resulting from eutrophication can greatly damage aquatic ecosystems and pose a high risk to human health. Phosphorus (P) and nitrogen (N) are the major causes for eutrophic conditions and can enter to the aquatic ecosystem via different sources. The combination of phosphorus precipitation and sediment capping are promising technologies to minimize internal P loading and control harmful algal blooms in eutrophic lakes. Denitrification bioreactors have emerged as an important edge-of-field treatment technology to reduce nitrate-nitrogen loads from external sources. The objective of this study was 1) to evaluate the use of natural minerals to enhance the precipitation of phosphorus and cyanobacteria during alum coagulation, 2) to reduce phosphate release during sediment capping, 3) to evaluate the synergistic effects of polyaluminum chloride (PAC) and phoslock on phosphate and cyanobacteria removal during coagulation of eutrophic lake water, and 4) to evaluate the quantity and quality of dissolved organic carbon (DOC) leaching from agricultural residues including corn cobs, corn stover and barley straw to develop a new denitrification bioreactor system that uses a combination of an agricultural residue and woodchips for enhancing the nitrate removal efficiency.
Laboratory coagulation experiments were conducted on a lake water spiked with Anabaena sp. using alum and four natural minerals (zeolite, calcite, limestone, and sand) to determine the effect of natural minerals on chlorophyll alpha, phosphate and turbidity removal. Long-term column sediment capping experiments were also conducted using different minerals after alum coagulation to evaluate their effectiveness in reducing phosphate release. The results showed that alum coagulation was able to remove 85--90% of phosphate and chlorophyll alpha from Anabaena sp. enriched lake water samples. The added natural particles did not substantially affect the removal of phosphate and chlorophyll alpha during combined alum and particle coagulation. However, natural particles substantially increased the floc settling kinetics during coagulation. The combined treatment with alum and particles also increased the resistance of the sediment to disturbance by mixing. The long-term sediment capping experiments showed that capping with natural minerals substantially reduced the levels of phosphate released from the sediment.
Lake water samples were also treated with PAC, phoslock, and the combination of these two technologies to evaluate their removal efficiencies for phosphate, chlorophyll alpha, and DOC. The impact of doses, pH, DOC levels on the removal efficiencies were investigated. The results showed that PAC alone achieved 90% removal for phosphate and chlorophyll alpha, and 23.6% removal for DOC at the maximum dose of 8 mg Al/L. Phoslock alone removed phosphate, chlorophyll alpha, and DOC by 70%, 73.3% and 4%, respectively, at a dose of 800 mg/L. The combination of PAC (4 mg Al/L) and phoslock (300 mg/L) resulted in the removal of phosphate, chlorophyll alpha, and DOC by 90%, 100%, and 35%, respectively, suggesting that the combination of PAC (4 mgAl/L) and phoslock (300 mg/L) is able to significantly enhance the phosphate, chlorophyll alpha, and DOC removal efficiencies. The combined use of PAC and phoslock exhibited high tolerances to variations in pH and DOC levels for phosphate and chlorophyll alpha removal. The combination of PAC and Phoslock also increased the settling kinetics of the flocs.
The final set of experiments showed that the DOC leaching potential followed the order of barley straw > corn stover > corn cobs > woodchips. Agricultural residues also exhibited faster DOC leaching kinetics and higher biodegradation potentials than woodchips. Although agricultural residues leached higher concentrations of nutrients during initial flush, those concentrations quickly declined within several days of leaching.
Notlar:
School code: 0205
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(680582.1) | 680582-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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