Electrocoagulation coupled to activated carbon sorption/filtration for treatment of cleaning wastewaters from wood-based industry

Abstract

The objective of this investigation was to study the use of a coupled treatment (electrocoagulation (EC) and sorption/filtration treatment) with different sequencing to reduce the organic pollutants measured as chemical oxygen demand (COD) of five highly polluted wastewater streams generated after washing surfaces and machinery in the wooden floor industry and to evaluate, how different sequencing of these treatment units affects the overall system efficiency. On the basis of preliminary studies, an EC reactor (1.0 L) was constructed with monopolar electrodes in parallel connection in an array of four Al electrodes with surface area of 93.2 cm² and an applied current density of 161 A m^–2. This reactor was coupled to a sorption/filtration unit with coal activated carbon. The EC reactor was tested in two different sequences (before and after the sorption/filtration unit). The overall COD reduction varied from 2% ± 0.5% to 77% ± 2.9%, depending on the sequence and the treated wastewater stream. The best result from efficiency and operational viewpoints was obtained with the EC reactor placed after the sorption/filtration column. The increase in efficiency is likely to be due to the removal by sorption in the activated carbon of compounds that interfere with EC. Additionally, as desired, the use of EC before the sorption unit extended the activated carbon lifetime.

Keywords:

• Cleaning wastewater
• Electrocoagulation
• Activated carbon
• Wood-based industry

Acknowledgments

The financial support to the research project from the Swedish Knowledge Foundation (KK-Stiftelsen), the European Regional Development Fund, and the industry AB Gustaf Kähr are acknowledged.