Wastewater Electrodialysis Membrane System

Electrodialysis Membrane System works to achieve separation on the ionic components of the water through the use of semi permeable membranes. The membranes are alternately stacked together and each of it is either anionic or cationic charged so that the cation exchange membrane will attract the anions leaving only cations to pass through and vice versa for anion membranes. The principal behind the operation relies on the use of electrical driving force whereby two different electrodes will cause electric current to pass through the solution and thus creating freshwater at the receiving end.

Electrodialysis is often engaged for use in wastewater treatment plants in order to remove and lower salt concentration. The incoming flow is usually diverted through a narrow gap created by stacks of membranes. Typical system is designed to retain wastewater for at least 10 to 20 seconds so that it can function at optimum rate when it comes to the salt removal. Several points of consideration have to be evaluated during the design part such as solubility of the salt affected by temperature of incoming wastewater, type and concentration of ions, amount and incoming flow rates before a complete system is finalized. Based on this loading criteria, it will determine the amount of driving force which is the current needed to pass through the system, number of membrane stacks needed and overall the selection on the type of membranes.

In order to come up with a well-designed electrodialysis system, engineers have the tasks to ensure that these channels whereby water will pass through should be as narrow as possible. As the salt concentration decreases in the wastewater, more electric current need to pass through but however, caution has to be taken to ensure the water molecule does not split to form H2 and O2 instead. Recent development on the engineering design has led to improvements whereby the membranes were arranged in different stack designs so that this will minimize the effects caused by concentration polarization.

In order ensure that the system operate in tip top condition, several issues need to be addressed. First, problems associated with chemical precipitation in wastewater has to be overcome because this will actually lead to clogging caused by formation of residual organic matter. To solve this issue, the feed wastewater should first undergone pretreatment so that this will avoid possible damage to the membrane and ensure better efficiency in the long run.

Related topic: Phosphate Removal by Chemical Precipitation.

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