A4 Conference proceedings

Continuous electrocoagulation process for treatment of mining waters

Open Access publication

Publication Details
Authors: Mamelkina Maria A., Cotillas Salvador, Lacasa Engracia, Tuunila Ritva, Sillanpää Mika, Häkkinen Antti, Rodrigo Manuel A.
Publication year: 2018
Language: English
Title of parent publication: 11th ICARD | IMWA | WISA MWD 2018 Conference – Risk to Opportunity
Start page: 267
End page: 275
Number of pages: 9
ISBN: 978-0-620-80650-3
JUFO-Level of this publication: 0
Open Access: Open Access publication


Mining industry is known to be the major producer of sulfur-rich
wastewater. Streams with high sulfate concentrations come mainly from mineral
excavation and processing as well as from continuously discharging mine
drainage. Presence of sulfate ions in water is a major environmental issue in
many countries, wherever mining has been established on a large scale. Removal
of sulfate by biological degradation, membrane filtration, adsorption, ion
exchange or precipitation with limestone is obstructed by its high solubility
and stability in aqueous solutions. However, elelctrocoagulation has been
proposed as a promising technology for the removal of sulfate ions based on the
previous studies dealing with the treatment of other industrial waters.

This research is intendent to study the removal of sulfate
and other anionic contaminants using continuous electrocoagulation with iron
electrodes. A novel design of a test unit allowed the accumulation and
recycling of solids formed during the EC process that resulted in favouring of
anions removal. The test unit was operated at a once-through mode, meaning that
treated wastewater was not delivered back to the cell. Additionally, performances
comparison of continuous EC with batch EC and conventional chemical coagulation
was performed. Removals of sulfate, nitrate and chloride were monitored during
the processes.

Application of the continuous electrocoagulation
process with a settler for solid accumulation resulted in a higher sulfate removal
and almost complete nitrate elimination as well as lower electrochemical
dissolution of electrodes. Chloride was not
removed, but opposite to chemical coagulation, its concentration was maintained
at the same level during the test. Together
with anionic contaminants removal, continuous electrocoagulation was found to
be efficient in the depletion of NH4+, Cu2+,
Ni2+ and Zn2+. During continuous operation, 70% of sulfate was
removed with iron concentration 1.2 mol dm-3. In
addition, changes in pH were much lower than those observed in a batch mode.

continuous electrocoagulation process brings a significant improvement on the
elimination of sulfate, nitrate and all selected cations from minign waters. Continuous operation provides the treatment
possibility of sulfur-rich streams of a large volume. Solids recycling allows treatment of
process mining water minimizing secondary pollution. Simultaneous removal of
anionic and cationic contaminants by EC favours its application as the main
technique at wastewater treatment plants.

Last updated on 2019-13-03 at 12:00