Summary of Common Problems in Reverse Osmosis in Wastewater Treatment
2015-05-28
1. How long should the reverse osmosis system be cleaned?
Under normal circumstances, when the normalized flux decreased by 10 ~ 15%, or system desalination rate decreased by 10 ~ 15%, or the operating pressure and the inter-segment pressure difference increased by 10 ~ 15%, RO system should be cleaned. The cleaning frequency is directly related to the pretreatment degree of the system. When SDI15 <3, the cleaning frequency may be 4 times per year; when SDI15 is around 5, the cleaning frequency may be doubled but the frequency of cleaning depends on each item Site of the actual situation.
2. What is SDI?
The best available technique for evaluating colloidal contamination in influent RO / NF systems is to measure the influent silt density index (SDI), which is an important parameter that must be determined before the RO design. During RO / NF operation, measurements must be made periodically (2 to 3 times daily for surface water), and ASTM D4189-82 specifies the criteria for this test. The inflow regulation of the membrane system is that the SDI15 value must be ≤5. Effective techniques for reducing SDI pretreatment include multi-media filters, ultrafiltration, microfiltration, and the like. Adding a polyelectrolyte before filtering can sometimes enhance the above physical filtering and reduce the SDI value.
3 general water should use reverse osmosis process or ion exchange process?
In many water conditions, the use of ion exchange resin or reverse osmosis technically feasible, the choice of technology should be determined by the economic comparison, under normal circumstances, the higher the salt content, the more economical reverse osmosis, salt The lower the amount, the more economical is the ion exchange. As a result of reverse osmosis technology, a large number of popular, reverse osmosis + ion exchange process or multi-stage reverse osmosis or reverse osmosis combined with other deep desalination technology has become a recognized technology and economic more reasonable water treatment programs, such as in-depth For more information, please consult a water treatment engineering company representative. 4. Membrane life depends on the chemical stability of the membrane, the physical stability of the components, washability, water source, pretreatment, cleaning frequency, operation and management level. According to economic analysis is usually more than 5 years.
4. Reverse osmosis membrane components can generally use a few years?
Membrane life depends on the chemical stability of the membrane, the physical stability of components, cleanability, water source, pretreatment, cleaning frequency, operation and management level. According to economic analysis is usually more than 5 years.
5. What is the difference between reverse osmosis and nanofiltration?
Nanofiltration is a reverse osmosis membrane ultrafiltration method between the liquid separation technology, reverse osmosis can remove the smallest solute, molecular weight less than 0.0001 microns, nanofiltration can remove the molecular weight of about 0.001 micron solutes. Nanofiltration is essentially a low-pressure reverse osmosis, used to deal with water purity is not particularly stringent occasions, nanofiltration suitable for the treatment of well water and surface water. Nanofiltration is suitable for water treatment systems that do not require a high desalination rate, such as reverse osmosis. However, the removal capacity of the hardness component is high, sometimes referred to as "softening film". The nanofiltration system has low operating pressure and low energy consumption Corresponding to the reverse osmosis system.
6. Membrane technology has what kind of separation ability?
Reverse osmosis is currently the most sophisticated liquid filtration technology, reverse osmosis membrane on the solubility of salts and other inorganic molecules and molecular weight greater than 100 organic matter from the interception, on the other hand, water molecules can freely through the reverse osmosis membrane, the typical soluble The removal rate of the salt is & gt; 95-99%. The operating pressure ranges from 7 bar (100 psi) for the brackish water to 69 bar (1,000 psi) for the seawater. Nanofiltration can remove the impurities in the 1nm (10 ?) and the molecular weight of more than 200 to 400 organic matter, the removal of soluble solids of 20 to 98%, containing monovalent anions such as NaCl or CaCl2 removal rate 20 ~ 80%, while the divalent anion containing salt (such as MgSO4) removal rate is high, 90 ~ 98%. Ultrafiltration separates macromolecules greater than 100 to 1,000 angstroms (0.01 to 0.1 micron). All the soluble salts and small molecules can pass through the ultrafiltration membrane, removable materials including colloids, proteins, microorganisms and macromolecular organic matter. Most ultrafiltration membranes have a molecular weight cutoff of 1,000 to 100,000. Microfiltration removal of particles in the range of about 0.1 to 1 microns, under normal circumstances, suspended solids and large particles colloidal can be retained and macromolecules and soluble salts can freely through the microfiltration membrane, microfiltration membrane used to remove bacteria, micro Flocs or total suspended solids TSS, the typical membrane on both sides of the pressure of 1 ~ 3bar.
7. Who sell membrane cleaners or provide cleaning services?
Water treatment companies can provide special membrane cleaning agents and cleaning services, the user according to the membrane company or equipment supplier's own purchase of cleaning agents for membrane cleaning.
8. Reverse osmosis membrane water to allow the maximum concentration of silica how much?
The maximum allowable concentration of silica depends on the temperature, pH, and scale inhibitor. Typically, the maximum allowable concentration at the concentrate side is 100 ppm without the scale inhibitor. Some scale inhibitors allow the highest concentration of silica in concentrated water 240ppm, consult the supplier of the scale inhibitor.
This article is taken from the North Star Energy Conservation Network
