As we all know, reverse osmosis membrane technology is a commonly used seawater desalination technology. At present, the reverse osmosis membranes suitable for industrial scale mainly include cellulose acetate membrane and polyamide membrane, and their desalination rate is 94% ~ 97%. Wastewater can reach the discharge standard through physicochemical and biological methods. Disc tube reverse osmosis (DTRO) technology is a high-tech reverse osmosis technology, which first started in Germany. Compared with coil reverse osmosis, it has more obvious characteristics of high pressure resistance and pollution resistance. Even in the case of high turbidity, high SDI value, high salinity and high COD, it can run economically, effectively and stably, and is more suitable for the treatment of high salinity wastewater. In China, it is mainly used for landfill leachate and desalination of seawater and brackish water. Although the water treatment effect of DTRO is very good, the cost of membrane module of DTRO is relatively high, because it mainly depends on imports. Zheng Jin, Yantai, Shandong, used Dow environmental protection raw materials and German first-class processing equipment to realize the manufacture of DTRO membrane, which greatly reduced the operating cost of this technology and made it widely popularized in China. The retention rate of DTRO salt is 98% ~ 99.8%.
Coil reverse osmosis (DTRO) is a unique membrane separation equipment. The coil membrane module adopts an open flow channel, the linear distance between the two guide plates of DT module is 4mm, and the surface of the guide plates has a certain arrangement of protrusions.
This special mechanical design makes the treatment liquid flow through the surface of the filter membrane under pressure, forming turbulence when encountering bumps and collisions, increasing the transmittance and self-cleaning function, thus effectively avoiding membrane blockage and concentration polarization and successfully prolonging the service life of the membrane; It is also easy to clean the scale on the diaphragm during cleaning, which ensures that the coil membrane group is suitable for treating wastewater with high turbidity and high sediment concentration coefficient and adapting to harsh water inlet conditions.
DTRO membrane module has a special flow channel design form and adopts open flow channel. The feed liquid is pumped into the DTRO membrane tower from the feed inlet through the booster pump, and flows to the other end of the module from the channel between the guide plate and the shell. At the flange at the other end, the feed liquid enters the guide plate through eight channels, and the treated liquid flows quickly through the filter membrane in the shortest distance, and then flows reversely to the other membrane surface at 180 degrees. Then it flows into the next guide plate from the notch in the center of the guide plate, thus forming a double "S"-shaped route from the circumference of the guide plate to the center of the circle, then to the circumference and then to the center of the circle on the surface of the membrane, and finally the concentrated solution flows out from the flange at the feeding end.
Evaporative concentration-cooling crystallization technology is a technology that the concentrated salt wastewater after reverse osmosis treatment is re-concentrated by evaporation, and finally the concentrated solution is cooled to crystallize and separate the soluble salt substances in the high salt wastewater.
This process can separate some salt substances and obtain crystallized salt compounds, and the crystallized mother liquor needs to be returned to the previous evaporation section for circular evaporation and concentration.