Ecosoft EDI-16 is the industrial system intended to produce highly demineralized water with application of the electrodeionization technology. The system is equipped with the DOW EDI-310 electrodeionization modules. These are the compact spiral-wound modules that are easy to install, and take less space. The EDI-310 elements are leak-free in contrast to flat-plate constructions, and easy to clean.

The Ecosoft EDI systems are automated for uninterrupted operation without constant attention of staff.

Key advantages:

• high demineralization of water without application of reagents
• stable high quality of purified water
• uninterrupted process of purification – no need to stop filters for classification and regeneration of ion exchange resins
• possible to adjust quality of purified water and levels of automation
• no need to store and handle hazardous chemical reagents

CHARACTERISTICS

Operational characteristics and technical data:

Capacity for deionized water at 25 °C	m3/hour	15…17
Electrical resistance of purified water	mega-ohm	≤ 15
Consumed electrical capacity	kW	2…2.5
Inlet pressure	bar	3.5…4
Module type		DOW EDI-310
Connection diameters:
inlet	saddle	DN 50
outlet	saddle	DN 50
concentrate discharge	saddle	DN 20
electrolyte discharge	saddle	DN 20
Dimensions (W x D x H)	mm	2500 x 1500 x 1950
Operation mode of one module
Capacity for purified water	m3/hour	1.5…2.2
Recovery	%	up to 95
Feed water temperature	°C	10…38
Maximum feed water pressure	bar	6.9
Maximum feed water pressure for uninterrupted operation	bar	5.5
Pressure drop of feed and purified water	bar	1…2.5
Pressure drop of permeate and concentrate	bar	0.5-0.7
Intensity of electrolyte washing	L/hour	40…60
Maximum consumed electric current	A	9
Maximum operational voltage	V	160

Feed water requirements:

Hardness	meq/L	≤ 0.01
Silicate	mg/L	≤ 0.5
Total organic carbon	mg/L	≤ 0.5
pH (acceptable range)		5.0…9.0
Free chlorine	mg/L	≤ 0.05
Iron and manganese	mg/L	≤ 0.01
Turbidity	mg/L	≤ 0.1
Oxidizing agents	mg/L	none

PERFORMANCE

Electrodeionization is the process of uninterrupted water demineralization with application of ion exchange resins, ion-selective membranes and constant electric field.

The key driving force of the process is difference of constant electric field potentials on both sides of the membrane channel generated by cation-exchange and anion-exchange membrane, filled with ion-exchange resin. Specifically the electric potentials difference provides migration of dissolved ions from the water stream through ion-selective membranes and uninterrupted regeneration of ion exchange resins.

Electrodeionization consists of three processes:

1. Ion exchange, during which the ions dissolved in the feed water passing the layers of the ion-exchange resins are absorbed by the anion or the cation exchange resin;
2. Ion discharge through the layers of the ion-exchange resin and the ion-selective membranes to the zone of concentrate;
3. Regeneration of the ion exchange resin with ions of hydrogen and hydroxide ions obtained as a result of electrolytic process of water molecules subjected to direct current.

These processes in electrodeionization are run uninterruptedly.

MAINTENANCE

During operation of the electrodeionization systems it is necessary to monitor current condition of elements. Special attention should be paid to the following.

Contamination with solid particles and impurity or resins increase pressure drop on the module and decrease efficiency of water demineralization due to poor contact of functional groups of the ion exchange resins.

Content of oxidizing agents such as chlorine can destroy beads of the ion exchange resin, and lead to damage of the structure and consequently to degradation of exchange capability.

To prevent irreversible formation of deposits, it is necessary to control quality of water and permeate yield.

To retrieve system performance, it is necessary to perform chemical washing in the cases of:

1. reduction of the module efficiency by 10-15% compared to its nominal efficiency;
2. increase of electrical conductivity of the permeate by 10-15% compared to its initial value, when the value of inlet electrical conductivity hasn’t changed.

To maintain operational condition of the module, its regular operation is required without long idle periods. The long idle periods impact quality of the purified water and create conditions for microbiological fouling.

The module should work during several hours per day. Interruption of module operation for less than 12 hours does not have any impact on the modules, and no special measures for protection of the ion exchange resin are required. During the break in their operation modules should be completely filled with water.