Pure Water Occasional, March, 2023
 
Greetings from Pure Water Products, the Pure Water Gazette, and the Pure Water Occasional.
 
 
 
In this almost-Easter Occasional you'll hear a lot about PFAS, turbidity and bold  suggestions for solving the water shortage in western states. Read about the old faithful Fleck 5600 control valve,  the mighty Sand Trap, sediment filters, PFAS in toilet paper, nonstick pans, water-repellent fabrics, fire-fighting foam, and military bases. Hear about bold plans to save water by cutting down forests and using nuclear power to treat water. And, as always, there is much, much more. 

Thank you for reading, and sincere thanks from Pure Water Products for your continuing support.  
 
Thanks for reading!

Please visit the Pure Water Gazette, where you will find hundreds of articles about water and water treatment, and the Pure Water Products website, where there is much information about water treatment and the products we offer. On both sites pop-up ads and other distractions are stricly against the law.


 
 

Turbidity
 
Turbidity is technically a measurement of the degree to which particulate in the water interferes with light transmission. Suspended particles absorb and diffuse light. Testing water for turbidity measures the diffusion of light as it passes through the water. 
 
 
 High turbidity can be identified without a water test.


A turbidity test uses an instrument that passes light through the water and measures the amount of interference from suspended particles.The turbidity test reports results on an artificial scale using nephelometric units, or ntu. Anything above one ntu is technically an EPA “action level” violation, although the human eye only begins to detect turbidity in water at about 4 ntu. Therefore, water that appears completely clear to the eye can have excessive turbidity with health implications.

Turbidity in groundwater is often from tiny mineral particles. These can include precipitated iron, clay particles or calcium carbonate precipitation.  In surface water turbidity is more likely suspended organic matter or other sediment.

The level of turbidity can, of course, range from invisible to the eye to highly colored water that is not transparent.   

Turbidity in water is more than an aesthetic issue. It is a frequent indicactor of microbial contamination because microbes can attach themselves to suspended sediment. Turbidity also makes it more difficult to disinfect water with chemicals.  The same is true with UV treatment because suspended particles can shadow microbial contaminants protecting them for the germicidal effect of the UV lamp.
 
 
 
Residential sediment treatment can range from the "Sand Trap," shown above, which relies on gravity to drop large particles from the water, to extremely tight membrane filters that can screen out sub-micron sized particles.
 
 
Treatment for turbidity is mainly by filtration. Sediment filters can be cartridge style, granular beds, or membrane-style. With large particles, simply holding the water in a tank will allow particulate to settle out. In municipal treatment, settling and filtration are often aided by chemicals like alum which promote coagulation and flocculation of small particles to form larger particles that settle out or are filtered easily. The very tiniest of particles can be treated by extra  tight filter technologies called microfiltration and ultrafiltration and even tighter membrane systems like nanofiltration and reverse osmosis. Reverse osmosis can remove particles down to 0.001 microns. 
 
It is important to realize that turbidity in water is not just an aesthetic consideration. While crystal clear water is certainly more appealing to the eye and to the palate, turbidity is also an important health consideration because microbes thrive in unclean water. Even if water appears clear, it is a good idea to test for turbidity and to take high turbidity readings seriously.
 
 
Not all cloudiness in water is particulate. When cloudy water clears from the bottom upward as in the picture, the problem is not physical particulate but simply excess air trapped in the water. This sometimes occurs when carbon filters are new or when aerating treatment products are being used. 

 
Commonly used sediment filters:

Simple wound string, spun polypropylene and pleated cartridge filters are available in a large range of “tightness” ratings that are stated in “microns.” Cartridge filters range in size from tiny to very large. Probably the most common residential whole house sediment filter is the popular ten-inch “Big Blue.”  With cartridge filters, the smaller the micron size, the tighter the filter. The smaller the number, the more effective the filter, but also the easier it is to clog and the more it resists flow and drops water pressure. 
 
“Spin down” separators that are usually measured by “mesh” size. These have long lasting screens that are cleaned by simple blow down process. With mesh sizes, the larger the number, the tighter the filter. A 60 mesh screen is looser than a 100 mesh screen. 
 
“Sand traps” that allow large particles to drop from the water into a specially designed filter tank. 
 
Backwashing filters that contain specialty media designed to trap sediment. The newer natural zeolite media can filter down to 3 microns. 
 

 

 
 

By far our most popular backwashing filters over the years have been those built with the reliable and very user friendly Fleck 5600 control. Now only 5600 filters are shown on our website. We made the change to 5600 only for water softeners a couple of years ago and it has worked out well.
 
The 5600 has size limitations. It works only on filters that need a backwash rate of 7 gallons per minute or less.  If a larger filter than those shown on our site is needed, we can supply it, but it can’t be ordered from the shopping cart. We still stock and support the Fleck 2510 models that were recently taken down, but they are available by phone only so that we can assure that they are properly sized. We also sell much larger filters and softeners with Fleck 2815 and 3150 and Nelsen C-Series (Clack) controls that are not shown on the website.
 
The very popular Fleck 5600 SXT (simple electronics) control, pictured above, is ideal for customer-maintained filters.  No special tools are needed for repairs and parts are easy to find.  We program the control before it is shipped, and changes in programming are easy. We still supply the time-clock version of the 5600 as well for those who prefer it. 
 


 
 
 
 
 
 
 
 
 
 
 
Places to visit for additional information:

 
 
 
 
 
 
 
Thanks for reading. The next Occasional will be out eventually--when you least expect it.

Pure Water Products, LLC, 523A N. Elm St., Denton, TX, www.purewaterproducts.com. Call us at 888 382 3814.