The Application of Electrodialysis for Drinking Water Treatment
321
energy costs compared to the other technologies. On the other hand, reverse
osmosis offers also the possibility for the reduction of other impurities such as
organic substances.
Electrodialysis as a physical separation process for nitrate offers several
advantages. The process can be operated highly selectively. Hence, the water
composition is scarcely changed and the produced concentrate can serve for
nitrate recovery. Besides nitrate also hardness is removed. The process is also
characterized by very low chemical and energy consumption. Thus, only
membrane costs remain as the main cost factor.
3.2 Description of the Electrodialytic Nitrate Removal (ENR) Plant
Kleylehof
In 1990, V A TECH W ABAG started pilot tests for nitrate and hardness
removal by means of electrodialysis at the Kleylehof well in eastern Austria.
These tests were carried out for 2 years. The average nitrate concentration in the
raw water was 80 to 100 mgr! N03. The hydraulic capacity of the pilot plant
amounted to I m 3 h-!. The aims of the research program were to assess the
efficiency of desalination in view of nitrate and hardness removal, product quality,
water recovery with regard to brine quality, the selection of membranes and longterm experience (Hell et al. 1995).
Due to the specific requirements, which were best met by the electrodialysis
process, V A TECH W ABAG obtained an order for the design and erection of a
full-scale plant in 1996. The plant was to be suitable for seasonal operation in
order to cover peak demands in summer. The plant was designed for a hydraulic
capacity of 40 Is-! with three hydraulic stages and a maximum of 160 mg N03r! in
the raw water. The guarantee for the treated water, in the case of maximum nitrate
concentration in the raw water, is less than 50 mg N03r!. The plant is remote
controlled and works fully automatically.
The main components of the plant are:
• Raw water intake
• Electrodialysis unit
• Disinfection unit
• Brine loop
• Electrode rinsing loop
• Concentrate discharge
• Dosing station
The raw water is abstracted from a well and pre filtered with bag filters. Then
the raw water is distributed to the electrodialysis units and a small portion to the
brine loop.
The electrodialysis units consist of three EDR stacks with a membrane length
of I m. Each EDR stack is allocated to one rectifier. The voltage of the rectifiers is
manually adjusted according to the raw water conductivity and the requested
321
energy costs compared to the other technologies. On the other hand, reverse
osmosis offers also the possibility for the reduction of other impurities such as
organic substances.
Electrodialysis as a physical separation process for nitrate offers several
advantages. The process can be operated highly selectively. Hence, the water
composition is scarcely changed and the produced concentrate can serve for
nitrate recovery. Besides nitrate also hardness is removed. The process is also
characterized by very low chemical and energy consumption. Thus, only
membrane costs remain as the main cost factor.
3.2 Description of the Electrodialytic Nitrate Removal (ENR) Plant
Kleylehof
In 1990, V A TECH W ABAG started pilot tests for nitrate and hardness
removal by means of electrodialysis at the Kleylehof well in eastern Austria.
These tests were carried out for 2 years. The average nitrate concentration in the
raw water was 80 to 100 mgr! N03. The hydraulic capacity of the pilot plant
amounted to I m 3 h-!. The aims of the research program were to assess the
efficiency of desalination in view of nitrate and hardness removal, product quality,
water recovery with regard to brine quality, the selection of membranes and longterm experience (Hell et al. 1995).
Due to the specific requirements, which were best met by the electrodialysis
process, V A TECH W ABAG obtained an order for the design and erection of a
full-scale plant in 1996. The plant was to be suitable for seasonal operation in
order to cover peak demands in summer. The plant was designed for a hydraulic
capacity of 40 Is-! with three hydraulic stages and a maximum of 160 mg N03r! in
the raw water. The guarantee for the treated water, in the case of maximum nitrate
concentration in the raw water, is less than 50 mg N03r!. The plant is remote
controlled and works fully automatically.
The main components of the plant are:
• Raw water intake
• Electrodialysis unit
• Disinfection unit
• Brine loop
• Electrode rinsing loop
• Concentrate discharge
• Dosing station
The raw water is abstracted from a well and pre filtered with bag filters. Then
the raw water is distributed to the electrodialysis units and a small portion to the
brine loop.
The electrodialysis units consist of three EDR stacks with a membrane length
of I m. Each EDR stack is allocated to one rectifier. The voltage of the rectifiers is
manually adjusted according to the raw water conductivity and the requested