Industrial effluents consisting of salt solutions formed during processing or by neutralisation of acid/base streams contain a high salt concentration, and are therefore difficult to treat. Hence the removal of salts from industrial effluents by sustainable techniques is of great interest to many companies.
In this Belgian study, an industrial saline water, mainly comprising NaCl and KCl, was treated with conventional electrodialysis (ED) and bipolar membrane electrodialysis (EDBM) in lab-scale experiments.
The saline water also contained significant amounts of sulfate and calcium, which may give rise to various types of scaling.
Partial desalination (the target was removal of 50% of the chlorides) was easily achieved with both ED and EDBM. Using ED, a concentrate containing circa 2M of chlorides was obtained.
Formation of scaling was avoided by using monovalent selective anion- and cation-exchange membranes, particularly necessary to avoid CaSO4 scaling.
A further improvement was obtained by applying EDBM, which yielded an acid and a base stream with a concentration of about 2M, with relatively good purity.
From the initial lab-scale study it was concluded that both ED and EDBM are technologically feasible to desalinate the saline water.
In a second phase, the ED scenario was scaled up in a pilot-scale study, which demonstrated that the ED pilot plant was operated in a stable way during a long-term experiment.
