The plus side of electropositive filtration
The advantages over traditional sieve-type filters are numerous and potentially lifesaving.
HEALTH AND SANITATION 27
By
Yuly Vesga, PhD
Electropositive filtration takes advantage of surfacecharge effects. The net effect is the creation of a strong broad-spectrum particle magnet capable of filtering particles smaller than its pore size. Here, we present a brief explanation of how and where electropositive filters can be used.
To describe what makes a positively charged filter special, we can start by discussing the mechanisms of filtration used. Filters, in general, are classified depending on the mechanism they employ to remove particles, as well as on the type of particles they isolate. There are two main types of separation mechanism: sieve retention and adsorption. Sieve retention is the most common mechanism used for conventional filtration.
This type of filter retains particles that are bigger than the filter’ s pores. While sieve retention depends on physical blockage, adsorption uses attractive forces to attain particles present in water( typically negatively charged). Accordingly, it is very easy to see which mechanism has the advantage. In the case of adsorption, the filter is capable of retaining particles that are so small they are practically impossible to hold with sieve retention. Additionally, since the adsorption process is based on adhesive forces, the pore size is not required to be smaller than the desired contaminant’ s particle size.
Electropositive filters have several advantages over traditional sieve-type filters. Filtration of colloidal and nanometer-sized particles at low head pressure, elimination of water waste, high filtration efficiency, high dirt-holding capacity, and the potential of filtering certain soluble contaminants are among the advantages observed when using electropositive filters. There are numerous applications for the separation of a wide range of particle sizes. Two outstanding applications are as a polisher and pre-filtration for RO systems. Additionally, they can also be employed in the filtration of contaminants from the water waste stream in pharmaceutical and chemical plants and the filtration of soluble and insoluble dyes. However, a significant and often overlooked ability of electropositive filtration is the removal of microbial pathogens without the need for chemical treatment.
As previously mentioned, electropositive filtration is based on the adsorption mechanism, which is considered the most efficient process for the separation of viruses and bacteria from water. Most viruses and bacteria are known to be negatively charged at a neutral pH. As a result, there is an attraction force that exists between the negatively charged viruses and bacteria and the overall positive charge from the surface-modified media. In other words, the media exhibits a positive zeta potential. It is important to remove microbial pathogens from water because microbes are not only potentially pathogenic contaminants, but also foulants in HVAC( heating, ventilation, and air conditioning). Additionally, they have a tendency to attach to surfaces and form biofilms. Finally, bacteria can play a role in corrosion.
Fortunately, these types of filters are manufactured and readily available to the public. While the worldwide population could use this type of filter, those most vulnerable to bacteria and viruses ingestion, like children, the elderly, and the immune compromised, would most benefit from this unique capability.
Filter manufacturers are doing an excellent job at offering options for implementing water filtration systems for residential use. There are two main types of system: POU( point of use) and POE( point of entry). POU systems are easily identifiable because they are connected under the sink. POE systems, more commonly known as wholehouse systems, are another very convenient option. These two systems, either by themselves or in unison, can provide the homeowner protection from many unplanned and potentially dangerous‘ water events’.
One such‘ water event’/ concern for the homeowner should be the boil water notice / warning. There are more than 5 000 boil water notices per year in the United States alone. These are issued when the water distributed by a municipality plant is suspected to be contaminated with microbiological agents. Some of
Russ Chaney
In the spirit of the sharing of unique experiences that shape the plumbing industries in our respective nations, the following article looks at how and where electropositive filters can be used. Written by Yuly Vesga, PhD, of Argonide Corp., it is the next in a regular series of similar articles that will run in this magazine.
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www. plumbingafrica. co. za April 2018 Volume 24 I Number 2