The presence of which organism in water suggests past or intermittent pollution?

The presence of Streptococcus fecalis, specifically a type of enterococci, in water is indicative of past or intermittent pollution, particularly from fecal sources. This microorganism is used as an indicator of water quality since its presence suggests that there has been a contamination event, typically from human or animal waste. Unlike some other indicators, Streptococcus fecalis can persist in the environment for longer periods, even after the pollution source has been removed, thus highlighting past contamination rather than ongoing pollution.

This characteristic makes it a valuable tool for assessing water safety and quality over time, as it can help determine if water has been subject to pollution that may not currently be apparent, emphasizing its utility in monitoring waterborne pathogens.