Effectiveness of Oxygen-Saturated Seawater Injections and Air Sparging Technologies in Remediation of Coastal Marine Sediments from Sludge
2021
Ferrández-Gómez, Borja | Sanchez Sanchez, Antonio | Jordá Guijarro, Juana Dolores | Fonfría, Eva S. | Bordehore, Cesar | Cerdán, Mar | Bordehore, Cesar | Cerdán, Mar | Ferrández-Gómez, Borja | Fonfría, Eva S. | Jordá Guijarro, Juana Dolores | Sanchez Sanchez, Antonio | Universidad de Alicante. Departamento de Agroquímica y Bioquímica | Universidad de Alicante. Departamento de Ecología | Universidad de Alicante. Instituto Multidisciplinar para el Estudio del Medio "Ramón Margalef" | Universidad de Alicante. Instituto Universitario de Materiales | Química Agrícola | Electrocatálisis y Electroquímica de Polímeros | Gestión de Ecosistemas y de la Biodiversidad (GEB)
The occurrence of hypoxic muddy sediments on shallow beaches and other sheltered areas is a well-known environmental problem, which negatively affects coastal areas, tourism potential, the public use of beaches and sediment biodiversity. The usual solution is limited to dredging and removal of sludge to a landfill site. In this study, a laboratory-scale experiment was performed to determine the effectiveness of two technologies: a modification of air sparging and a new approach based on injecting oxygen-saturated seawater in hypoxic muddy sediments (oxygen-saturated seawater injections method), for remediating sludge in coastal sediments, minimizing environmental impact respect to dredging. Our results showed that both technologies significantly increased dissolved oxygen content in pore water, facilitating the oxidation of more than 90% of the organic matter, and other reduced inorganic compounds such as sulphide, with the consequent increase in sulphate concentration from 0.3 to 3.0 g·L−1. Moreover, a rise of redox potential from − 258 mV to above 200 mV, and a dramatic drop in chemical oxygen demand were also indicators that oxic conditions had been restored. After 65 days, soft, black, muddy and hypoxic sediment with high organic matter content and a characteristic foul odour was transformed into well-oxygenated sediment, which had a low organic matter content and had lost its initial shiny black colour and odour. The main difference between both technologies was the depth influenced by sediment remediation; oxygen-saturated seawater injections affected deeper areas than clean pressurized air injections.
Afficher plus [+] Moins [-]This work was supported by Own Research Program to MC and CB of the University of Alicante (Grant Number [PC15-05]) and Route Pont SL.
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