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一．Reverse osmosis equipment problems in the application
 Reverse osmosis desalination compared to other desalination devices, such as: evaporator, electrodialysis, rehabilitation beds, with unique characteristics and advantages of reverse osmosis domestic work is also increasingly receive attention. With the increase reverse osmosis technology, the problems are worsening, mainly the following reasons:
 ① A full set of imported equipment as the different quality of raw water, lack of technical feasibility and process changes, not copy, not suitable for our truth. Therefore, reverse osmosis water must be based on the different quality of raw water pretreatment equipment to meet water quality requirements.
② Poor technical capacity of some companies do not know the number of reverse osmosis membrane elements and the rational choice, the reasonable arrangement of membrane components, etc., causing part of the membrane components running in an irregular situation.
 ③ Domestic film quality, but off. Film quality directly affects the removal of salt and other impurities, produced by Dow Chemical Filmtec membrane, the rejection rate can be stabilized at 90%.
 ④ Operation and management is lax. System is running, pressure should be in the film can withstand the working pressure range, to prevent the super-strength, overload operation, the membrane produce mechanical injury, leading to leakage. When the reverse osmosis system is running for some time, the system appears sharp drop of water, deterioration of water quality or pressure of water increased, that film has to wash, then into a clean state of the machine should make the system self-cleaning, you can restore membrane Function.
二．Technical improvements
 2.1 Mechanical design of the filter
 Normal use of imported equipment is mainly due to low pretreatment device is not combined with poor water quality of raw water characteristics, mechanical filter backwash is not complete, the upper filter sand caking, SDI (pollution index) increased, resulting in membrane fouling Affect the system operation. RO plant generally requires SDI <4 (the film component manufacturers have different requirements on the SDI), to achieve the above requirements, the following aspects should be improved and perfected the technology:
2.1.1The choice of mechanical filters
 Combination of raw water quality and equipment materials, packing, it is recommended to use double-layer filter material filter. The mechanism is from the filter should be large and small, in fact, mechanical filter through the upper sand layer to retain the smallest, so easy to plug the top of sand, lumps, head loss increased quickly. If the top and then add granulated anthracite sand increased capacity sewage capacity, long operation cycle, slower growth in head loss, in practice with good results.
2.1.2Mechanical filter backwash
 Mechanical filter filled with quartz sand as a larger proportion of the internal, recoil is not easy, many systems run the instability is completely ignore the backwash and clean the process, the system can not reach the device set backwashing recoil strength requirements, which Many water treatment equipment manufacturers and engineering companies problems. According to our experience in the engineering application, the use of gas, water, repeated washing method, mechanical filter backwash after fouling effect is very clear, clean sand is very clean, good recovery performance, specific measures are:
 ① Backwash devices in the design, recoil pumps, piping must meet the requirements of the amount of backwashing, backwashing strength 12 ~ 15L / (s? m2);
 ② Cleaned by compressed air filter, so filter sludge and other objects off the surface, the strength of 18 ~ 25L / (s? m2).
2.1.3The choice of the internal packing
 Internal packing, according to its drainage structures can choose different sizes of different quartz sand, quartz sand grain size but the top should be 0.3mm. in the most upper part of anthracite particles loading 0.5 ~ 1.0mm, the height of not less than 200mm.
2.2Application of activated carbon adsorption
 Activated carbon adsorber two main functions: ① some organic compounds in water adsorption, adsorption rate was 60%; ② adsorption of residual chlorine. For direct extraction of groundwater users, to cancel the activated carbon, if the hardness is greater use of water softeners, you must use the activated carbon surface water because the water disinfectant, chlorine has a strong activity of oxidation, can damage the RO membrane, under RO system water requirements of chlorine <0.1mg / L, so the use of activated carbon to adsorption of residual chlorine. Removal of residual chlorine is not a simple addition of activated carbon adsorption, but in its catalytic surface of, so there is no activated carbon adsorption saturation, but the loss of carbon and ourselves.
2.3The choice of coagulation agents
 In the mechanical filter before adding a variety of Coagulant and polymer flocculant to remove suspended solids in water, colloids and other impurities, but not under water if the facts and blindly added, not only not improve water quality, contrast agent itself or due to pharmaceutical Impurities contained on the RO membrane leaving the water into harmful substances, many of the domestic pharmaceutical water treatment system have this problem. Therefore, the choice of great stress Pharmacy. According to the characteristics of RO membranes:
 ① Should avoid the use of aluminum salt coagulant type. Coagulant aluminum type that is easy to produce aggregation of alumina into the RO after the surface difficult to clean;
 ② Should not be used cationic polymer flocculant. RO membrane anionic, cationic polymer flocculant combined with easy to generate a membrane is difficult to clean the polymer film. If you do not attach importance to the above, ranging from shortened membrane life, while in some membrane component obsolescence. Compatibility between both agents can not be ignored, such as the use of the ST with the ArgoAF150ul flocculants should be used.

2.4Reverse osmosis (RO) technology of the system

2.4.1The importance of security filters
 The main purpose of the security filter is to ensure that water does not damage the RO membrane modules, generally used in the filter pore size of 5μm, under pressure to determine the exchange before and after the filter, pressure control within the 58.8kPa.
 Systems are currently used disposable wound or PP cotton filter, even small pressure difference before and after the filter, use the time not too long, because the filter easy to grow bacteria, suggested 14 ~ 15t / (h? m2) (m2 filtration area for the filter.)