If you spot a bright-orange fuzzy deposit or oily film floating on top of a stream or in a puddle, this means there are iron-oxidizing bacteria present in the water. These bacteria feed on the iron in the water. When the iron is dissolved it reacts with the oxygen in the air creating deposits that build up in areas of low or no water flow. If you see the deposits, it means that the water is acidic and the soil contains substantial levels of iron. Iron oxide deposits are found all around the world and have always been a natural ecological process. These deposits will float away with the natural flow of the stream and raise no concern for water quality or pollution levels. The oil-slick looking residue fractures into plates when disturbed, unlike oil which will swirl. The simple test will put your mind to ease if you think there’s a bunch of oil floating in the water.
Bacteria, orange fuzz and oil slick in water
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