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Control of Eutrophication in Anzali Wetland by Artificial Floating Islands

Shahrouz Ebrahimi, Pouneh | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 46941 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Abrishamchi, Ahmad
  7. Abstract:
  8. Anzali wetland, in the Caspian Sea, northern Iranian province of Gilan, ranges from fresh near the tributary streams to brackish near the mouth into the harbor and the sea. Anzali wetland has faced with the serious levels of eutrophication because on the other hand, the lagoon has decreased in size during current century, to less than a quarter of its former extent and on the other hand, this wetland is faced with entering a huge amount of nutrient elements due to human activities in its watershed. Discharge of industrial wastewater, animal wastes, timber harvesting and the most important entering, rice farms irrigated wastewater are of the considerable causes of eutrophication in wetland. During few decades, reduction of entering streams flow velocity and increasing of annual precipitation in western coastal region, have increased the surface of the wetland but this size increment by itself, cannot represent the ability of system assimilation. One of the most significant ways to reduce environmental damage, and offering recreational opportunities and even aesthetic value is constructing the floating island. Providing a larger surface area for biofilms to treat pollutants, substrate floating islands increase treatment efficiency, particularly for total nitrogen, total phosphorus and colloidal heavy metals reduction. Nitrogen and phosphate devaluation will lead to elimination of blue green algae and consequently, prevention of the risk to public health and ecosystem functionality. On the basis of its water tolerance and high durability, soft rush, Juncus effuses, and reed are suggested plants at this purpose. These plants can tolerate periods of drought and total inundation. This native plant can tolerate 2.5 - 8 cm of standing water as long as the level fluctuates over the growing season and uptakes nutrient element by its expanded roots and produces sufficient oxygen for aerobic microorganism’s activity via its leave and bud. Aerobic microorganisms thereafter remove nitrogen and phosphorus compounds from wetland. To achieve the accurate results, pilot simulation and laboratory element assays, before and after of natural treatment by floating islands, are required. Suggested pilot is a pool with 6 (3×2) square meter surface area and 1meter depth and was operated for 5 months to provide sufficient time for N and P removal and also elevation of dissolved oxygen due to phytoremediation. In this research, dissolved oxygen, and phosphorus amount besides concentration of different kinds of nitrogen, including nitrate, nitrite, ammonium and total nitrogen, was measured in National Inland Water Aquaculture Institute (Bandar-e Anzali) laboratories. Results showed the efficiency of the artificial floating island. As it was expected that plant activities, soft rush and reed in this case, led to element uptake and concentration adjustment, thereafter converted them to biomass or another forms like nitrogen gas to export them away from the water body and as a result reduced the algal population. The main prospect of this experiment was reduction of nitrogen and phosphate, providing suitable environment for aerobic aquatic organisms and safe bio haven for nesting and even constructing beautiful landscape
  9. Keywords:
  10. Nutrients ; Eutrophication ; Dissolved Oxygen ; Wetland ; Algae ; Pollutant ; Nitrogen ; Artificial Floating Islands

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