Just like hydrogen sulfide, microbiological water contamination starts from the decomposition of organic matter. These microorganisms are carried into our water supply by dead or decaying plants and animals, sewage and waste.
This type of microbiological contamination produces bacteria that can be eliminated at a large water treatment plant but are hard to remove at private wells. The bacteria can’t be seen or smelled. The best way to see if your water is contaminated is to send a sample to a lab for testing.
When microbiological contamination is caused by organic matter like algae, your water will start smelling fishy and possibly musty. Small levels of this type of contamination are not as harmful as lead, but you can still remove it with a home filtration system.