The EDR process is a new process. It reverses the polarity of the positive and negative electrodes (frequent reversal) at regular intervals (usually 15-20 minutes). This can automatically clean the dirt on the ion exchange membrane and the electrode surface, ensuring the quality and quantity of fresh water, stable operation of the ion exchange membrane and minimum concentrated water discharge. The principle of reversal electrodialysis is as followsDownAs shown in the figure.
Desalination electrodialysis reversal equipment is a membrane-based process that uses an electric field to remove salt and other dissolved solids from water.
The EDR process involves two layers of membranes connected by an electrodialysis membrane. When a direct current is applied, the membrane selectively allows positive ions to pass through, leaving behind negative ions and other impurities. The process can be reversed by reversing the polarity of the electric field, causing negative ions to pass through the membrane while positive ions are left behind.
How does it work? How does EDR work?
Under normal operation, two streams enter the EDR system and three streams leave the system. The inflow is raw water and concentrated water circulation. The outflow is fresh water, concentrated water drainage, and electrode waste water. Each EDR stack has four inlets and outlets. Two of them flow into the top and bottom electrode compartments. The electrode polarity is controlled by reversing the cathode and anode. The other two streams are water flows through the membrane stack, namely concentrated water and fresh water, which are determined by electrode reversal. The source, composition and flow direction of each stream are as follows:
1.The raw water/product liquid flows in from the water inlet, flows through the membrane stack to remove ions, and then flows into the water production pipe. Part of the raw water is diverted to be concentrated water replenishment and electrode raw water. The product water is judged as unqualified product water based on the water quality requirements, and qualified product water flows into the water production tank.
2.Brine circulates in the EDR system. As ions continue to increase, part of the stream needs to be discharged to keep the ion concentration below the precipitation point. Part of the raw water needs to be added as makeup water to maintain a constant water volume. Acid is intermittently added to the brine to prevent precipitation.
3.The cathode liquid stream flows continuously. This stream is a tributary of the raw water. The electrode waste liquid leaves the cathode and flows through the degassing component before being sent to the waste liquid.
4.The anode stream flows intermittently. The raw water of this stream is a tributary of the raw water. The electrode waste liquid leaves the positive electrode and flows through theAfter the gas components are removed, the waste liquid is sent to the waste liquid.
5.ECIP cleaning is usually performed once a day during EDR operation. Acid is added to the electrode inlet water to clean the electrode chamber to control carbonate scaling at the electrode. This process usually lasts for 1 hour each time. This procedure is not required for EDR machines. CIP cleaning is required when the EDR membrane block is blocked by dirt. CIP can be performed periodically as needed. The system must be stopped during CIP operation.
What are the components of EDR?
The EDR system consists of three parts: electrodialysis body, rectifier and automatic reversal system. The reversal operation procedure is as follows:
1. Change the polarity of the DC power supply electrode to interchange the concentrated and diluted chambers, and the ion flow will be reversed;
2. Switch the inlet and outlet valves to interchange the water supply and drainage systems of the concentrated and diluted chambers;
3. After the polarity conversion lasts for 1-2 minutes, the unqualified fresh water is returned to the concentrated water system, and then the concentrated and fresh water go their own way to restore normal operation.
What are the differences between EDR and EDI?
EDI filling electrodialysis is a new water treatment method that combines electrodialysis with ion exchange. It concentrates the advantages of electrodialysis and ion exchange, overcomes their respective disadvantages, and improves the effects of limiting current density and current efficiency.
EDR reverses the polarity of positive and negative electrodes, which can automatically clean the dirt on the surface of ion exchange membranes and electrodes to ensure the long-term stability of the ion exchange membranes and the quality of fresh water.
Difference: The desalination rate of EDR is only about 90%. It can be used for some raw water with poor quality and low water production requirements. The water production is relatively stable. It can also be used for industrial wastewater treatment. However, the service life of the electrode is shorter due to frequent reversal.
EDI mainly replaces the traditional ion exchange mixed bed to produce high-purity water. This technology has been promoted and applied in the preparation of high-purity water in the electronics, electric power, chemical and other industries.
Where can EDR be used?
EDR is used in a variety of applications including desalination, industrial wastewater treatment and food processing. Desalination EDR equipment can be used in a variety of electrodialysis applications including seawater desalination, brackish water desalination and wastewater treatment. The system is capable of removing up to 99% of dissolved salts and other impurities from water, producing high-quality product water that meets or exceeds drinking water standards.
Some of the most common applications include:
Municipal water treatment: It can be used to treat the reverse osmosis concentrated water generated during the municipal water supply treatment process.
Industrial Wastewater Treatment: Desalination can be used for the concentration and treatment of industrial process wastewater.
Power generation: It can be used to treat the reverse osmosis concentrated water produced in the process of power generation.
Mining: Desalination can be used to treat and concentrate water used in mining operations.
What are the advantages and disadvantages of EDR equipment?
1. EDR desalination electrodialysis equipment is an advanced desalination water supply equipment. The equipment reversal function reduces maintenance time and downtime because the reverse flow clears all possible blocking particles in the membrane pores.
2. Lower energy requirements, lower operating costs and handling capacity of water with high salt concentrations EDR also produces higher quality product water than other methods, with low dissolved solids content and no residual disinfectants.
4. High efficiency desalination application; low maintenance and chemical-free; modular design allows scalability; easy operation and monitoring
