As an environmental protection technology, membrane separation technology is widely used in modern water production industry, waste water industry and other non-water concentration due to its extremely high environmental protection benefits, ultra-low operating energy consumption, and normal temperature operation / Separation Industry.
Comparison of two-stage reverse osmosis with other traditional processes
In the modern water production industry, laboratory water has undergone methods such as distillation, ion exchange, primary reverse osmosis + EDI, primary reverse osmosis + ion exchange, etc. In recent years, the rise of two-stage reverse osmosis (DPRO) heat. This is inseparable from the continuous progress of modern membrane separation technology and the rapid marketization of its products.
From the comparison table below, we can see the characteristics of the two-stage RO and the traditional process:
1. From the perspective of salt removal rate, the water conductivity of the two-stage RO product can fully meet the requirements of CLSI in the United States and the water specifications of CHINA's analytical laboratories for laboratory pure water, as well as the requirements of USP24 and Chinese Pharmacopoeia for medical purified water Require.
2. From the perspective of the ability to remove SiO2, TOC, viruses and bacteria, two-stage RO is almost a good choice for high desalination rate. Considering the energy consumption and operating cost at the same time, the two-stage RO is undoubtedly economical. Whether it is distillation, ion exchange, or primary reverse osmosis + EDI, all have fatal weaknesses.
The obvious disadvantage of the distillation process is that the energy consumption is too high and uneconomical; although the ion exchange resin has a high desalination rate, its removal rate for TOC and bacteria and viruses is not high, and its selectivity for weak bases such as silica is not high; The desalination rate of the first-stage reverse osmosis + EDI is also very high, but the obvious disadvantage is that the water inlet requirements of EDI are very strict (even harsh), and the first-stage reverse osmosis matched with it will fluctuate greatly due to changes in the quality of the feed water. The water cannot meet the water intake requirements of EDI. At the same time, because the water intake method of the laboratory is on and off, the operation of the first-stage reverse osmosis + EDI system is very unstable.
Application of two-stage reverse osmosis
Everyone must be familiar with the single-stage RO, so is the two-stage RO a simple superposition of the single-stage RO? no! In terms of design, the two-stage RO has the characteristics different from the single-stage RO.
Two-stage RO, as the name implies, the feed water needs to pass through the first-stage RO separation and purification treatment of pure water, and then pass through the second-stage RO separation and purification treatment before finally becoming product water.
The main factor affecting the quality of reverse osmosis produced water is the quality of feed water. Once the purified water treatment system is established, the quality of the feed water has a direct impact on the quality of the product water during operation. Good water supply will inevitably produce good product water, while poor quality water supply may lead to unqualified product water. Through the above-mentioned two-stage RO principle and ultra-high desalination rate, the experimental test shows that the two-stage RO can stably produce pure water with a conductivity of <5 μs/cm under the condition of feed water conductivity <2000 μs/cm. The ultra-purification system using two-stage RO treatment technology can operate stably almost without the limitation of raw water with high salt content.
When the quality of the two-stage RO product water is stable and the conductivity is less than 5 μs/cm, the processing capacity of the subsequent purification unit can be greatly increased. Through experimental tests, when the number of purification columns is fixed, the water treatment capacity of the purification column will be increased by more than 4 times when the pure water with a conductivity of <5 μs/cm is used as the feed water compared with the pure water with a conductivity of >10 μs/cm .
To sum up, the use of two-stage reverse osmosis technology in laboratory ultrapure water machines can not only ensure that the ultrapure water machine can stably produce pure water of <5μs/cm under the condition of high-salt inflow water, but also greatly improve the purification The amount of water exchanged by the column (that is, the total output of ultrapure water) prolongs the service life of the purification column. Allowing users to obtain high-quality pure water and ultrapure water at the same time, the cost of using ultrapure water machines is lower.
