By Roger Nathanson

It’s not uncommon to read about the hidden dangers that can be present in our drinking water. Those dangers are so small it takes a high-powered microscope (and incubation) to see them. The process for determining certain contamination is often both difficult and expensive.

Filters and what they filter
E.Coli and coliform are the standard by which many health departments and certified labs judge individual well water quality—below certain levels, drinking water is deemed safe. Yet there are also viruses and parasites such as Giardia and Cryptosporidium, which are extremely expensive to analyze. For this reason they are rarely tested—fortunately these rarely occur in properly sealed wells.

There are air- and waterborne microbes such as Legionella, Aspergillus and Pseudomonas, which must have a water medium to survive for extended periods, but they can survive on moist or dry surfaces for a short time. Again, rarely do these appear in sealed wells.

There are now special filters that have been tested by certified laboratories to remove particles down to a sub-micron level. In doing so, these filters achieve certain microbe removal…or do they?

If you haven’t had the water analyzed at both pre- and post-filtration, then you haven’t really ascertained the success of your filter. The difficulty begins with determining what to analyze. Is there an E.Coli problem? For this it is easy to ascertain the success of your product, but what about Giardia or Crypto? The sampling itself may be quite a complex undertaking and many labs do not test for microbiologicals. You will have to find one that does, or one that contracts out such testing to those with the specialized facilities for such analysis. It could cost hundreds or thousands of dollars.

Propagation breach (PB)
This is not a good thing. Every filter on the market capable of retaining and/or removing microbes (including reverse osmosis [RO] filters) will become a breeding ground; meaning you can stop the adults but you cannot stop the larvae. One micron or smaller is required to filter adult E.Coli; however, the larvae can easily pass through an RO membrane.

Many times the filter works so efficiently that it retains the microbe and its food source, thus creating a virtual feeding ground and incubation media.

How to avoid PB
Assuming that you have properly ascertained the success of your product, you can maintain this success a few ways. Be sure the filter is changed on a regular basis. The frequency of change should be within the breeding cycle. If proper filter changing is not acceptable due to cost, then filter cleaning will be necessary. Contact your filter supplier for specific cleansing and sterilization protocols.

Both methods could become exceedingly expensive and time consuming given the cost of replacement filters and the breeding rate. Therefore, the following alternatives can be used to eliminate the growth on the outside and inside of the filter.

Ozone filters
There is nothing better than bombarding the outside and saturating the inside of the filter with ozone gas. Ozone kills a wider array of microbes faster and more completely than any other oxidizer. Ozone keeps the larvae from passing by killing the adults and inactivating most organics that are the food source.

Ozone leaves no hazardous chemical residual, nor does it impart any chemical taste. Actually, ozone has been widely used to improve the taste of bottled water. Ozone is the only acceptable means of microbe inactivation in the bottled water and beverage industry and most if not all bottled water says, ozonated on the label. Filters using post-ozone injection exhibit two to three times the life and capacity due to an absence of biological fouling.

UV light filters
An ultraviolet (UV) bulb is placed on the inside or center core of the filter, which inactivates certain microbes that pass the filter membrane. The main problem with using a UV light is that it does nothing to kill the adult breeders, which penetrate and propagate the outer filter layers. UV also has a limitation as to the variety of microbes killed.

UV does nothing for extending the filter’s useful life and capacity as does ozone. However, it is a common and favorite adjunct to filtration given the low cost of UV as compared to ozone.

Probably the worst choice one could make is to inject chlorine for microbe control whether for POE or POU applications. Chlorine is not nearly as effective on single cell animals such as bacteria, viruses, protozoa and cysts. Chlorine is very good at killing algae, which is not commonly found in sealed well water unless it is being drawn from an untreated surface water supply.

The chlorine dose and contact time may have to be high (3+ ppm) in order to safely assure complete kill. The filters typically suffer early failure due to the high concentration of chlorine, which tends to deplete its capacity.

An additional drawback when using chlorine is there are by-products to contend with. Chlorinated organics (THM, chloroform, chloramines, etc.) are the result of chlorine oxidizing organic material commonly found in surface or groundwater.

Continued analysis, potability, liability and litigation
Did you know that if you sell a system based upon yielding potable water, you are liable for the consumer’s subsequent health and well-being related to the treated water supply since installation of that system?

Outline a follow-up analysis protocol on a bi-monthly basis. This will continue to verify water potability and safeguard the end user—and you. The end user must agree in writing that testing will continue without interruption while they own the system. It must be stated and agreed upon in writing that the system is not rated for potable water if the bi-monthly testing schedule is not met.

Have a set goal in mind, which corresponds with the goals of your customer. Outline a method for verifying the presence or absence of microbes in the raw water supply. Verify the well is properly secure and sealed and there is no surface water intrusion from any source or after rainfall.

Verify you have accomplished your water treatment goals. It’s not like eliminating iron or sulfur, where it is obvious as to whether you have succeeded or not. Microbes are invisible and only rarely impart taste, color or odor. You won’t know they’ve been eliminated unless you test or someone gets sick. Outline a follow-up analysis protocol on a bi-monthly basis. Be sure all agreements, protocols and outlines are in writing and agreed to by the customer.

About the author
Roger Nathanson is president of Ozone Pure Water Inc., a full service ozone / water treatment supplier since 1980. Nathanson heads the System Design, System Allocation and R&D departments. His background includes mechanical engineering, plumbing/pipe fitting, swimming pool remodeling and repair, sales and marketing. Nathanson holds a U.S. patent on a unique ozone unit/ozone generator design. Ozone Pure Water Inc. is a full service water treatment supply company, solving water treatment problems since 1980. Visit the website: or toll free (800) 633-8469; local (941) 923-8528 or fax (941) 923-8231.



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