Bacterial Contamination

Most deep wells are free from naturally occurring bacteria, but not all. And it is not uncommon for wells to become contaminated from flooding on the surface or improper maintenance procedures (such as laying pipe down on the ground and then putting it down the well). Any shallow well (under 25 ft) is open to surface contamination, and precautions should be taken to ensure your safety.

The most common bacteria tests will show Total Coliforms, Feacal Coliforms, and non-Coliform or total background counts.

Removing Bacteria

• Adding chlorine and/or ozone to the water also have the benefit of being an oxidizer, so can be a useful combination if you will be removing iron or manganese as well. Chlorine has the side-effect of unpleasant tastes and odours, and the need to monitor the residual to ensure the proper amount is being used. It will also not kill cysts, but is effective against most common forms of bacteria. Ozone can be expensive and difficult to implement.
• Ultraviolet disinfection is the most cost effective method and is easy to maintain, but requires that the water be clear enough for proper UV transmittance.
• BioSand filters use a biologically active layer to "consume" unwanted bacteria. BioSand is a unique type of slow sand filtration ideal for rural water treatment. Cleaning the slow sand filter does not consume any media and produces virtually no wastewater. BioSand filters have capacities ranging from 20 litres per hour to 600 litres per hour.

To ensure against proper contamination, we recommend having two barriers against bacteria. Reverse osmosis, while considered effective against most micro-organisms, should not be used as a sole means of disinfection.