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Identifying the optimal location for the outlet of petrochemical desalination plant saline wastewater in Chabahar coastal
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Fatemrh Rajaei *   |
| university of zanjan & university of zanjan |
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Abstract: (47 Views) |
Introduction: one of the environmental issues related to desalination plants, especially reverse osmosis desalination plants in coastal areas, is the discharge of their highly saline effluent into the marine environment. Increased salinity alone increases the density of water. This increase in density causes the effluent to sink and concentrate near the seabed, which can cause destruction of the ecosystem of that area. In general, the volume of effluent discharged, the location of discharge, the density and concentration of effluents, the environmental conditions of the sea such as the intensity of currents in the area, and the degree of mixing of effluent with seawater affect the amount and manner of dispersion or accumulation of these effluents. Therefore, in this study, modeling of the discharge of saline effluent from a desalination plant on the Chabahar coast was carried out to achieve the optimal design of the effluent outlet location using CORMIX software. In this regard, various scenarios were investigated using the trial-and-error method to determine the location of the inlet of the water intake and the outlet of saline effluent for better dilution and approaching the standards of the US Environmental Protection Agency (EPA).
Methodology: In this study, among the multi-valve diffusers, unidirectional and periodic diffusers were investigated. The discharge rate of saline wastewater for the desalination plant was considered to be 55 cubic meters per second and its density was 1053 kg/cubic meter. The simulations were carried out at a depth of 5 meters. The wind speed in the area was considered to be 3 meters per second and the Darcy-Weisbach Coefficient was considered to be 0.1. Based on information obtained from the Ports and Shipping Organization, the average flow speed is 0.1 meters per second. The effluent salinity was considered to be 43% higher than the seawater salinity in proportion to the final capacity. The final desalination capacity: 50,000 cubic meters per day and the final seawater intake capacity assuming an efficiency of 30% for the desalination plant: 150,000 cubic meters per day. In the simulation evaluation of salinity distribution to determine the location of the inlet of the water intake and the outlet of the saline wastewater, the EPA criterion was considered, which, based on the first criterion, water salinity within a 200-meter radius of the discharge location can increase by a maximum of 10 percent (given that the salinity of the ambient water is approximately 36 grams per liter, the salinity concentration within a 200-meter radius of the wastewater outlet is allowed to reach a maximum of 39.6 grams per liter). Variables studied in the simulated scenarios:
- Investigating the effect of single- and multi-valve wastewater discharge on the behavior of the concentration rate
- Investigating the direction and angle of the valves on the behavior of the concentration rate
- Investigating the effect of different flow speeds on the behavior of the concentration rate
Results and Discussion: The modeling results with the alternative port in the direction of the Y axis at a depth of 5 meters and 250 meters from the coast show that within a radius of 200 meters in the direction of the Y and X axes, the initial salinity will increase by 10 percent. Therefore, it is not recommended as a suitable diffuser. Also, the modeling results with the same direction port in the direction of the X axis at the wastewater discharge location at a distance of 250 meters from the coast showed a 2 percent increase in salinity at a distance of 200 meters from the desalination plant, and the increase in salinity at the intake inlet (12 meters deep and 425 meters from the coast) is less than one milligram per liter. Other scenarios at a depth of 5 m and 250 m from the shore with ports in the same direction and along the Y axis and different flow speeds in dynamic tidal conditions did not show a significant increase in salinity within 200 m of the desalination plant and are in accordance with the environmental standard limit for desalination plant salinity changes. According to the above results, the location of the water intake site was estimated to be 425 m from the shoreline and the distance of wastewater discharge from the shoreline was estimated to be 250 m.
Ethical Considerations
Data Availability Statement: The datasets are available upon a reasonable request to the corresponding author.
Funding: The article is an extract from a research project with code P/149054 entitled "Zoning and Determining the Potential of Various Land Uses within the Chabahar Free Trade-Industrial Zone."
Authors’ contribution, Fatemeh Rajaei as the author of the paper, conducted all parts of the research and wrote the whole manuscript.
Conflicts of interest: The authors of this paper declared no conflict of interest regarding the authorship or publication of this article.
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Article number: 5 |
| Keywords: Salinity concentration changes, scenarios, Site Selection, Cormix model. |
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Type of Study: Research |
Subject:
Special
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