Author: Site Editor Publish Time: 2022-09-13 Origin: Site
NF membrane was first used in the drinking water treatment industry, mainly for water softening, NF membrane for divalent and multivalent ion retention rate can reach more than 90%, for monovalent salt retention rate of 10% ~ 90%, the characteristics of NF membrane in the removal of trace amounts of harmful ions in drinking water at the same time, can retain part of the human body needs of monovalent ions. The world's first large NF membrane water purification system - France's Paris Riosse water plant was commissioned in 1999, processing water volume of 140,000 m3 / d, using FilmTec roll NF components NF200B-400 (medium hardness transmission rate), the water purification system of the Orsay River water organic removal rate of 95%, salt ions and hardness removal rate of 30% to 50%, providing high quality drinking water to approximately 800,000 inhabitants in 39 districts in the northern suburbs of Paris.
NF membranes can also be used in seawater/brackish water desalination pretreatment processes to reduce the hardness, total dissolved solids (TDS) and organic content of the water, reduce the salinity of the seawater entering the RO membrane module, thus reducing the possibility of CaSO4 scaling, increasing the recovery rate of the RO system, reducing energy consumption and costs, and having good potential for application in the field of seawater/brackish water desalination.
Generally speaking, NF is used in combination with MBR in the urban wastewater treatment process, so that MBR can perform the function of pretreatment to achieve high quality effluent and long-term stable operation of NF. It has been found that compared to the traditional activated sludge-microfiltration split pretreatment (as exemplified by the NEWater demonstration project in Singapore), MBR as pretreatment can increase the membrane flux of the subsequent high-pressure membrane operation by 30%, while the effluent quality is the same or even more stable. This shows the need for MBR as a pre-treatment for NF.
The textile dyeing and printing industry is characterised by high energy consumption, high water consumption and high pollution. The application of NF in dyeing and printing wastewater treatment is usually tailored to the different processes or sections of the wastewater. It is worth noting that in the textile printing and dyeing industry, the molecular weight of the dyes used is usually >700 Da, which is very suitable for removal by NF technology.
Waste leachate is characterised by complex composition and high concentrations of organic matter and ammonia and nitrogen. The high pollution characteristics of waste leachate determine the need to use biological methods and low pressure membrane filtration at the front end to remove most of the organic matter and suspended matter and other pollutants. The biological method with better effect on waste leachate removal at the front end is the anaerobic + aerobic combination process.
Food and beverage processing also produces a large amount of wastewater, but unlike printing and dyeing wastewater, waste leachate, etc., food and beverage wastewater usually does not contain toxic and harmful compounds, and its main pollutants are usually high concentrations of suspended or dissolved organic matter, including proteins, sugars, fats, minerals, etc. Biological methods can be used to pre-removal of organic matter, followed by NF for deeper treatment; in the case of a relatively single type of pollutant. Concentration treatment and resource recovery with NF can be considered.
