Membrane Type (CAM or Polyamide)
RO membrane found in markets can be classified into two types: CAM (Cellulose Acetate Membrane) and AP (Aromatic Polyamide). Normally we choose CAM to replace AP in treatment of surface water or waste water. The strong points of CAM are: glaze surface, without electric charge, it can low contamination deposit meanwhile microbe is not easy to stick on its surface. That feed-water can contain 0.3-1.0ppm free chlorine in operation is another merit of CAM. Chlorine, as a type of disinfectant, is able to protect CAM from corroding and blocking by microbe and algae. AP itself is chlorine resistance, but it can’t resist its oxidation, so removing chlorine is necessary.
Flow Rate
Water production flow rate is water yield through effective membrane unit surface, it is expressed by GFD (Gallon / Square Foot / Day) or LMH (Liter / Square Meter / Hour). Water production flow rate in RO system is positive proportional to contamination speed. Low flow rate, low contamination speed, vice versa. RO element with bigger membrane area could be selected to decrease flow rate.
If the system need to be cleaned per 3 months or longer period, that means the design of pre-treatment and RO system is reasonable, within 1-3 months, process is necessarily need to be revised or increase equipment.
Transverse Current Speed
Transverse is another important factor to influence contaminating speed in RO system. When transverse current speed of surface feed-water and its concentrated water is higher on membrane surface, contaminating speed would be lower. This is because high speed transverse current feed-water would lower deposition and accumulation on membrane surface, meanwhile accelerate diffusion rate of high concentrated salinity to main body solution, lower danger of deposition of indissoluble salinity.
RO cleanout
Cleanout and maintenance is an effective way to lower contaminating speed in RO system. Detailed methods include concentrated water recycling, low-pressure rinsing and regular disinfection.
Concentrated water recycling is able to remove contamination on RO membrane surface. Low-pressure rinsing can flush out contamination and concentrated water from membrane element, prevent microbe from multiplying. Regular disinfection is used to control microbe multiplying between two cleanouts.
Structure of RO Element
In the filtration of well water and surface water we mainly select spiral-wound membrane element as RO system parts. In consideration of anti-pollution capacity, installation space requirement, operation cost, etc. Spiral-wound membrane element is better than hollow fiber and frame filter. To design larger membrane area is benefit for lowering flow rate and increase transverse current speed, restraining contaminating speed.
