Significance of Pre-Filtration and Nanofiltration Membrane Systems

Deploying the pre-filtration method in industrial water filtration systems, includes harnessing nanofiltration membranes in preventing damage, reducing maintenance, and optimising efficiency.                           

FREMONT, CA: Membrane filtration plays an indispensable role in industrial process facilities for the filtration of water and wastewater. However, membrane systems are often delicate and susceptible to damage from large particulates present in the water. To mitigate these risks effectively, a pre-filtration step is crucial. Its main objective is to remove oversized suspended solids, thereby preventing damage, reducing the need for maintenance, and minimising the costs associated with premature membrane replacement.

Among the pre-filtering options, automatic self-cleaning scrape strainers have gained popularity and are now widely available. These strainers are becoming increasingly affordable and require minimal maintenance or attention in the process. They can effectively remove solids down to nearly 75 microns, allowing for continuous and uninterrupted flows during blowdown cycles. This eliminates the need for manual cleaning and conventional backwashing of systems. Opting for automatic scraper strainers can significantly reduce costs related to maintenance and membrane replacement.

Various filtration methods utilize membranes in the process. However, the most commonly used and well-established method is pressure-driven membrane filtration. This method relies on a liquid being forced through a filter membrane with a large surface area. Depending on the size and nature of the particles involved, the process can employ reverse osmosis, nanofiltration, ultrafiltration, or microfiltration techniques.

Reverse osmosis is utilized to produce potable or deionized water, while nanofiltration is commonly employed in wastewater treatments and by the petrochemical industry to purify gas condensates. Nanofiltration also plays a crucial role in the chemical industry for solvent recovery. Ultrafiltration and microfiltration have proven to be effective practices in water and wastewater treatments, offering potential benefits.

Industries such as automotive, aerospace, oil and gas extraction, refining, textiles, and pulp and paper mills have a high water demand, which has led to an increased need for water treatment. Ultra-pure water that meets strict limits on various constituents such as suspended and dissolved solids, dissolved gases, organic carbon, and biological organisms is particularly important in electronics and pharmaceutical manufacturing processes. Industrial applications often require water treatment to protect downstream equipment from fouling, scaling, corrosion, and other forms of damage and premature wear caused by contaminants commonly found in the source water. Therefore, pre-treatment of cooling towers and boiler feed water is frequently implemented to achieve desired outcomes. Nanofiltration membranes are also employed in treating non-potable water sources like grey water and recycled purple pipe water.

Membranes used in these processes are typically thin, porous sheets that do not effectively pre-filter large suspended particles from the water. This can lead to severe damage and fouling, resulting in premature replacement and unnecessary maintenance. Popular membrane filter manufacturers in the industry recommend pre-screening all influents from 100 to 500 microns to maintain membrane filter efficiency.