1. Seawater pretreatment: Whether it is seawater desalination or brackish water desalination, feedwater pretreatment is the key to ensuring the long-term stable operation of the reverse osmosis system. It should be fully considered when formulating the pretreatment scheme of seawater desalination: there are a large number of microorganisms, bacteria and algae in seawater. The reproduction of bacteria and algae and the growth of microorganisms in seawater will not only bring many troubles to water intake facilities, but also directly affect the normal operation of seawater desalination equipment and process pipelines. Periodic high tide and low tide, a large amount of sediment is entrained in the seawater, and the turbidity changes greatly, which is easy to cause unstable operation of the seawater pretreatment system. Seawater is highly corrosive, so the materials of the equipment, valves, and pipe fittings used in the system must be screened to ensure good corrosion resistance.
2. Seawater sterilization and algae killing: foreign seawater desalination projects mostly use chemical reagents such as liquid chlorine, NaClO and CuSO4 to sterilize and kill algae. Taking into account the traffic and other factors, it is difficult to add chemical reagents to sterilize and kill algae. In the development process of this project equipment, a seawater sodium hypochlorite generator is specially used. After the seawater intake pump, a small stream of seawater under pressure is separated into a sodium hypochlorite generator, and NaClO is generated under the action of a DC electric field, which is directly injected into the beach caisson by the potential difference to kill bacteria, algae and microorganisms in the seawater.
Due to the high hardness of seawater, the direct electrolysis of seawater to produce NaClO must overcome the problem of electrode scaling. In the development process, the electrodialysis frequent reversal (EDR) technology is used for reference, that is, the electrode polarity is switched every 5-10 minutes, which effectively solves the problem of scaling and precipitation of the sodium hypochlorite generator.
