1、 Standard recovery rate, actual recovery rate, system recovery rate 1, membrane element standard recovery rate: The recovery rate adopted by the manufacturer under standard conditions.
Actual recycling rate of membrane components: the manufacturer's recycling rate during actual use.
Membrane element system recovery rate: The above recovery rates are for individual membrane elements, while the secondary system recovery rate is for the overall recovery rate of the entire reverse osmosis device during actual use.
2. To avoid wasting water resources, small reverse osmosis devices also require high system recovery rates. Common method: Concentrated water circulation (part of the concentrated water from the reverse osmosis device is discharged, and the rest is circulated into the feed pump to maintain the lateral flow velocity on the surface of the membrane element while considering the required system recovery rate) Tips: Do not directly adjust the inlet and outlet valves of the feed water/concentrated water.
3. The higher the system recovery rate, the more water efficient it is, but the impact of a high recovery rate is that: ① the desalination rate of the product water decreases. ② Possible precipitation of slightly soluble salts The osmotic pressure of concentrated water is too high, resulting in a decrease in the water production of the components. 2、 The impact of recovery rate on the system. The common approach to improve the recovery rate of membrane components is to increase the number of membrane series sections or to reflux concentrated water.
1. Increasing the number of membrane segments to improve recovery rate
For example, the concentrated water discharged after one stage of membrane filtration can directly enter the second stage membrane for filtration, or three stages and four stages can be connected in series to achieve a high recovery rate for tillage. After the membrane is connected in series, the first section has a larger water flow than the second section, so the number of membranes in the first section is generally greater than that in the second section.
2. Concentrated water reflux improves recovery rate. Concentrated water reflux refers to the process of returning a portion of the concentrated water generated by the reverse osmosis system to the high-pressure pump, mixing it with the inlet water, and then entering the membrane module again for reverse osmosis treatment. This is also an effective means to improve the recovery rate of reverse osmosis systems. Especially for systems with low water production, it is very suitable. However, due to the reflux of concentrated water, the concentration of pollutants at the inlet will increase, and the risk of scaling in the reverse osmosis system will further increase. Therefore, it is necessary to strengthen the operation control and management of the reverse osmosis system. If the reverse osmosis system used by the production enterprise has stable inlet water quality and is better than the design value, and the system's treatment capacity still has surplus capacity, this method can also be considered for system modification. Therefore, it is particularly important to set the recovery rate appropriately according to the actual situation. Based on the water quality analysis data of raw water and its seasonal variation range, consider the design methods of reverse osmosis system related to pre-treatment and water recovery rate, operating temperature, etc., and set the operating conditions.
