Electrochemically assisted dewatering for the removal of oxyfluorfen from a coagulation/flocculation sludge

• Published in: Journal of environmental management Vol. 258; p. 110015
• Main Authors: Acosta-Santoyo, Gustavo, Raschitor, Alexandra, Bustos, Erika, Llanos, Javier, Cañizares, Pablo, Rodrigo, Manuel Andrés
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15-03-2020
• Subjects: Coagulation-flocculation; Electrochemical dewatering; Flocculation; Halogenated Diphenyl Ethers; Highly polluted sludge; Organochlorine pesticides; Sewage; Waste Disposal, Fluid; Water; Highly polluted sludge; Coagulation-flocculation; Electrochemical dewatering; Organochlorine pesticides
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2019.110015

This work focuses on the evaluation of the electrochemical dewatering of sludge obtained in the coagulation of wastes polluted with oxyfluorfen. To do this, sludge samples were treated, aiming not only to reduce the sludge volume, but also to facilitate the degradation of oxyfluorfen contained in the cake via electrolysis with a boron-doped diamond anode. Results show that water can be effectively recovered through three sequential stages. First, a gravity-driven stage, that can recover around 60% of initial volume and where no oxyfluorfen is dragged. Then, a second stage that involves the application of pressure and which accounts for the recuperation of an additional 25% of the total volume of the water removed and in which oxyfluorfen also remained in the cake. Finally, an electrochemical stage, which involves the application of electricity with increasing electric fields (1.0, 2.0, 4.0, and 16.0 V cm−1), accounting for the recovery of the rest of water released and where an electrolytic degradation of oxyfluorfen is obtained, whose extension depends on the electrode configuration used in the electro-dewatering cell. This electrode configuration also influences the retention or loss of oxyfluorfen from the cake, being the optimum choice the placement of the cathode downstream, next to the outlet of the dewatering cell.
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•Electro-dewatering of coagulation sludge allows an improved removal of water.•Position of the electrodes in the electro-dewatering cell has a significant influence on dewatering.•Position of the electrodes also influences the oxidation of the pollutant contained in the sludge.•A configuration anode-upstream / cathode-downstream removes more water and avoids the loss of herbicide.•A configuration cathode-upstream and anode-downstream contributes to retention of water in the cake.•A configuration cathode-upstream and anode-downstream contributes to the draining of the pollutant.