Micro-organisms as bacteria and cysts continuously threaten safety of our drinking water and make it quite appropriate to focus on the question how to prevent exposure to these kinds of pathogens.

Scientific data on levels of micro-organisms indicate that the concentration of coliform bacteria (i.e. e.coli), commonly found in surface waters, ranges from 105 (also expressed as log 5) per 100 ml for polluted stream water to 109 / 100 ml in raw sewage. Considering infectious levels of 103 for immune compromised people, the target effluent concentration after treatment should be less than 1/100 ml or a reduction of at least 8 log.

Cysts (i.e cryptosporidium and giardia) are the largest waterborne micro-organisms (3 - 6 micron) and occur in surface waters in a concentration of 10/L. They are highly infectious and the target effluent after treatment should contain less than 1/100L, equivalent to a 3 log reduction.

Since 1976 we know that not only ingested bacteria can have serious health effects, but also if inhaled Legionella Pneumophilia bacteria can cause a severe form of lung infection.

Conventional methods as RO, UV treatment or chemical disinfectants only partly and inadequately inactivate micro-organisms, as water temperature, pH, turbidity and other external factors, as well as the relative resistance of micro-organisms to disinfectants, influence effectivity.

The Ster-O-Tap
low pressure membrane technology offers a consistent and efficacious solution to biological control. Ster-O-Tap membranes remove in excess of 1 million ( 106) times more organisms or particulate matter than the highest rated carbon blocks, ceramic filters or UV sterilizers.


Bacillus subtilis 

Cryptosporidium Oocysts 

Escherichia coli (ecoli

Giardia lamblia 

Salmonella Typhi

Shigella Sonii 

Enterococcus faecalis 

Pseudomonas Aeruginosa 

Vibrio Cholera 

Information regarding approximate infectious doses and size may be gathered by selecting the desired image.
Each of the bacteria is compared in size to a cut off pore size of ± 0.15 µm.