Author: Site Editor Publish Time: 2022-11-04 Origin: Site
Membrane softening of water is achieved by using the selective permeability of nanofiltration membranes for different valence ions. In addition to hardness, membrane softening can also remove turbidity, colour and organic matter, and its water quality is significantly better than other softening processes. Membrane softening also has the advantages of no regeneration, no pollution, simple operation and low footprint, which has obvious social and economic benefits. Membrane softening has been very common in the United States, Florida in the last 10 years or so the new water softening plant are using membrane softening, instead of conventional lime softening and ion exchange process. In recent years, as the performance of nanofiltration has continued to improve and the price of nanofiltration membrane components has continued to fall, the membrane softening method has become superior or closer to the conventional method in terms of investment, operation and maintenance.
In addition to softening, nanofiltration membranes are used in drinking water treatment for decolourisation, removal of natural and synthetic organics (e.g. pesticides, etc.), tri-causal substances, disinfection by-products (trihalomethanes and haloacetic acids) and their precursors and volatile organics, ensuring the biological stability of drinking water, etc.
Studies have shown that nanofiltration membranes can remove most of the toxic and harmful organic substances and Ames mutagens from water, making TA98 and TA100 strains in each test dose of mutagenicity than MR values are less than 2, Ames test results were negative. Further studies will investigate the retention characteristics of endocrine disruptors in drinking water by nanofiltration technology to provide a basis for safe and high quality drinking water.
Disinfection by-products mainly include trihalomethanes (THMs), haloacetic acids (HAAs) and possibly trichloroacetaldehyde hydroxide (CH). Extensive research has been carried out by foreign scientists in this area and the average retention of these three disinfection by-product precursors by nanofiltration membranes is 97%, 94% and 86% respectively. Through the selection of suitable nanofiltration membranes, the quality of drinking water can be made to meet higher standards of safe and high quality drinking water quality. In addition, the nanofiltration effluent is low corrosive and has a positive impact on the service life of the drinking water network and the leaching of metal ions from the pipeline, helping to protect all materials in the water distribution system. Tests have shown that using the necessary post-treatment nanofiltration membrane systems can reduce the dissolution of lead in the network by up to 50%, while allowing the concentration of other dissolved metal ions to meet drinking water quality standards.
High removal rates of trace VOCs from drinking water.
Direct piped drinking water applications
Nanofiltration retains ions and other particles above the divalent level and only water molecules and some monovalent ions (e.g. sodium, potassium, chloride ions) are permeated. Nanofiltration can be used to produce direct drinking water with a certain amount of ions retained in the effluent, and can reduce treatment costs.