SELF-DOSING PROTECTION AGAINST MICROBIOLOGICAL CONTAMINATION IN WATER AND AQUEOUS FLUIDS

The Silverpearls preservation technology is a coated, particulate polymer material which is silver-coated wet-chemically with a layer consisting of elemental silver, the silver being an oligodynamically active metal. The Silverpearls are used for the antimicrobial treatment and/or preservation of water. Depending on their application, they are used either in specially manufactured housings, as loose bulk material or in filter elements/filter housings specially designed for this purpose.

Silver as a preservative

Silver-based products have been used to keep drinking water fresh since Charlemagne. Back then, in the form of silver vessels in which drinking water was kept, nobody knew anything about the specific effects of silver. Today we know that it is the positively charged silver ions that dock onto the microorganisms (e.g. pathogens such as Legionella, E.Coli, etc.) and disrupt the metabolism of the bacteria or lead to cell death in over 30 different mechanisms of action. The microbially acting silver ions have a unique long-term effect like no other active ingredient. Products based on chlorine or hydrogen peroxide cannot be “bound” in water, they evaporate and are therefore not suitable for preservation.

The Mechanism of Action

When the metallic (elemental) silver of the Silverpearls comes into contact with the oxygen-containing water/fluid, a concentration-dependent amount of Ag+ ions is formed. These formed Ag+ ions are solvated by water/fluids, pass into the fluid phase and are carried away. The positively charged Ag ions associate to the negatively polarized membranes of microorganisms. A large number of chemical reactions develop from this initially electrostatic interaction. These chemical reactions, with over 30 proven mechanisms of action of the silver ions, lead to reactions such as metabolic disorders and structural deformations in the microorganisms, which in turn lead to the inability to reproduce and even cell death:

• complex formation with DNA/RNA
• reactions with cytochromes
• change in membrane permeability
• blocking of the thiol groups of enzymes (-SH → SAg, e.g. inhibition of lactose dehydrogenase, glutathione peroxidase)
• reaction with carboxyl (-COOH) and amino (NH2) groups and much more.

How is the active concentration set?

Only the concentration of free solvated Ag+ ions acts as an antimicrobial effective concentration. The concentration of free silver ions in water and aqueous media depends to a large extent on which other substances (ions, complexing agents, etc.) are contained in which concentrations in the respective fluid. This fact is illustrated using the example of the chloride (Cl– ) ions contained in practically every natural drinking water , in accordance with the law of mass action:

c(Ag+) = 1,17x10-10/1,3c(Cl-)

If corresponding chloride concentrations (Cl– in[mg/L] or.[mmol/L] ) are used, the silver ion concentrations resulting under these concentration conditions are as follows:

CL– [mg/l]	CL– [mol/l]	Ag+ [mol/l]	Ag+ [μg/l]
10	0,28	4,67	50
20	0,56	2,33	25
-	-	-	-
60	1,69	0,77	8
-	-	-	-
100	2,82	0,46	5
-	-	-	-
200	5,63	0,23	2,5

That means that e.g. For example, in water with a chloride content of 20 mg/L, the maximum concentration is only 25 µg silver ions/L. It has been proven that one
effective concentration >5µg Ag+ /L with an exposure time of approx. 2 hours causes a kill rate of (4 … 6) log levels and thus ensures effective long-term protection.

Areas of application

• drinking water (according to DIN EN 15030)
• ventilation technology (according to VDI 6022)
• humidifier
• process water, cooling water pipes, lines, tanks
• fire extinguishing systems
• emergency showers
• apparatus and plant construction
• mobile gastronomy & food trucks
• camping, Boat/Yacht
• cooling towers
• evaporative cooling systems (according to VDI 2047) and much more.

Available pack sizes

• pre-assembled in the housing (SIPA80, STSN-15… STSN-200)
• bulk goods [kg]
• private label on request

Durability

Silverpearls have, protected from sunlight and
stored closed, a shelf life of 10 years. In contact with water/fluids, the shelf life or period of use depends on the respective application and is usually between 12 and 24 months.

Labelling

H410: Very toxic for water organisms with long-term effect.

Signal word: Attention

Use biocides safely. Always read the label and product information before use.

Active substance: silver (Ag+ )
BauA reg. No. N-72324
CAS No.: 7440-22-4

Technical data sheet (PDF)