Water Filter Filtration

Water Filter Filtration

How much does it cost to put a water filter(filtration) system in your home?

It really depends on what your looking for and what your problems are.
You can go with a cheap $50 system for one faucet or you can spend $80,000 for a whole house system. That number really depends on the total water usage in your home.
There's a lot more info needed before I can really get you a close figure.
Also if you go with an R/O System you need to install it right. You can not have any metal pipes or fittings used.

Disc Water Filters and its Back-Flush Cleaning Operation

Disc Filters are extensively used for agriculture, gardening and home applications. Many types are designed with Back-Flush mechanism for cleaning the filter when clogged. The discs are made from plastic materials, mostly compatible with FDA standards. When frequently using the Back-Flush to clean the filter there is no need to replace a cartridge element and the filter operation is regenerative for many years. These types of filters are therefore friendly to the environment and in line with the recent worldwide “green” fashion.

 The purpose of this article is to highlight a problem associated with the Back-Flush mechanism in many disc filter brands, where the filtration efficiency is being degraded after the Back-Flush operation due to gaps that are being opened between discs for the Back-Flush process. The only type of water filter that is designed to avoid this problem is the SDF Semiautomatic Rotary Filter in which the discs remain tightened at all times.

In order to understand this problem and how to avoid it, more details about the various disc structures and related filtration method are explained in the following sections.

Most filtration discs are made with diagonal grooves on both faces of each disc. A stack of discs pressed together forms a filtration element. The water infiltrate between the grooves from the outer peripheral into the core of the stack. This conventional disc technology is further explained and illustrated at this link: http://www.arkal-filters.com/tech_disc.html

For backflushing operation the tightening pressure of such disc stack is mostly released to open spaces between the discs and expose the grooves to the water stream of the Back-Flush. The cleaning is however never perfect and few solid particles mostly remain on the faces of the discs, then when the stack is retightened these solid particles constitute small open spacers and degrade the filtration quality. Another problem with this mechanism is the temporary formation of opening between the upstream side (inlet) to the downstream side (clean water outlet) of the filter. Any water turbulence during this short time interval might generate migration of dirt to the clean side.

Some filters are made with SDF filtration discs that are designed with different pattern of ribs on its faces. This design enables to keep the stack tightened at all times, including during back-flush operation.

The structure of the SDF discs is such that one face of each disk is formed with a continuous raised sinuous rib that extends radially and the second face is made with annular ribs that extend circularly. When the disks are stacked together, the annular ribs cross the sinuous ribs at right angles, to form small filtering passageways between the ribs. The dirt is collected along the outer border of the sinuous rib and can be easily washed out by reverse water flow – without a need to release the tightening of the disc stack. This unique structure is further explained and illustrated at this link: http://www.ein-tal.com/index.files/Page757.htm

The design of SDF Semiautomatic Rotary Filter maintains two important features:   a.)    The disc stack always remains tightened, even during back-flush operation.    b.)    Based on the compartments designed along the filter housing, water are first filtered and then used for back-flush, thus the back-flush is always done by clean water. The design of the SDF Semiautomatic Rotary Filter is further explained and illustrated at this link: http://www.ein-tal.com/index.files/Page846.htm

The problem with the released spaces in the conventional disc stacks is more severe for the fine filtration grades (microns level). A table of available mesh grades and respective applications can be downloaded from Rain-Tal website. As shown in the mesh table, Rain-Tal Ltd is the only company that reaches the filtration level of 5 microns for its products.

For home applications it is also important to prevent sediments of calcium and magnesium. Mechanical filters of any kind are not effective for this purpose, but the SDF combined with corrosion guard element can do. This option for home applications is offered by Tamhil company and is illustrated and further explained in Tamhil website.

In conclusion, for home and drinking water applications people should be aware of the features of back-flush of any filter they use and its influence on the filtration quality.

About the Author

The author is Gideon Rosenberg, physicist, who is experienced in disc filters for over 10 years, invented four patents related to disc filters and published a paper in the 9th International Filtration Conference held at San-Antonio TX 11-13 November 2008.

Water Filter Filtration

• Whole House Water Purifier
• Water Treatment

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