Pulp & Paper Industries Effluents – The use of Electro-coagulation

March 9, 2021 admin

Removing the Adsorbable Organic Halides (AOX) from Pulp & Paper Industries Effluents by using Electro-coagulation (EC)

These days, major worries of mankind are focused on the negative effects of industrial effluents in the Environment. In pulp & paper industries the concern with Adsorbable Organic Halides contaminants is high, these being subject to continuous monitoring, as part of the most toxic and harmful contaminants present in the wastewaters. Challenging limitations of conventional methods, project P2020 PROTEUS – Produtos e Tecnologias para o sector do Eucalipto1is aimed to evaluate technologies based on Advanced Oxidation Processes (AOP) due to its significant efficiency in removing AO from those wastewaters. The main objective of the Electro-Coagulation applications to remove the Adsorbable Organic Halides, with other contaminants alongside, optimizing the operations and energy costs to reach environmental sustainability and guarantee the Ecolabel standards.

The main feature within Electro-coagulation is an electro-chemical process, which is done by applying an electrical current between electrodes inside a reactor. This study focused on the intermediate stream D0, the most concentrated source of Adsorbable Organic Halides available. First, effluent enters the Electro-coagulation reactor after passing through a flowmeter and a pH meter. A current rectifier is introduced to supply a pre-defined voltage and current to the electrodes. The flow, the surface area, the distance between electrodes, the residence time are also operating parameters defined at several different conditions to optimize the ratio efficiency and cost. After Electro-coagulation the sample is collected the amount of Adsorbable Organic Halides and other relevant parameters were evaluated. All materials used were prepared for industrial conditions and operation, such as high temperatures (>65ºC) and a low range of pH. The trials were done with a modular reactor that could take electrodes with a variable gap between them. For this study trials, electrodes used were Iron (Fe) based electrodes for removing Adsorbable Organic Halides, and also phosphorous. Because of their good electrical conductivity, one can optimize the energy consumption rate and from its easy availability, their use creates an opportunity to add value to iron scrap wastes in the process, promoting a circular economy strategy. The pilot has a flowrate capacity of 1.5LPM and was installed in the bleaching sector of Aveiro Industrial Park.

The Electro-coagulation process returned impressive results on Adsorbable Organic Halides removal with 93% efficiency. For optimized conditions, under an industrial environment, a pilot plant operated at 0.5-1.0LPM in a range of 10-35mA/cm2 (j) with a very low average specific power consumption of 75W/g Adsorbable Organic Halides removed. In these conditions, the Electro-coagulation pilot reached the reduction objectives of 45%. The Electro-coagulation presented a good stability rate on Adsorbable Organic Halides mass reduction independent of operating conditions and the results suggest that Adsorbable Organic Halides removal by Electro-coagulation process could occur with reduced residence time.

Regarding the main objective, one can conclude that Electro-coagulation is a viable technique for this purpose; in comparison, Advanced Oxidation Processes based on Fenton, nanomaterials, and nanoparticles also present good efficiencies of removal but, in terms of cost-effective techniques, Electro-coagulation is a real breakthrough, especially in Pulp & Paper Industries Effluents.

Keywords: Advanced Oxidation Process (AOP), Adsorbable Organic Halides (AOX), Electro-Coagulation, Electro-Oxidation, Wastewater.

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