Lake Acworth
 

In early 1990's Lake Acworth's swim beach was closed because fecal coliform bacterial levels typically exceeded state standards.

Historical background on water-borne disease organisms:
Micro-organisms in water were not clearly linked to disease (e.g. typhoid and cholera) until the end of the late 1800's.
Primary sewage treatment usually kills pathogens through chlorination. However:

• stormwater sewers were often designed with connections to sanitary (sewage) sewers.
• sewage is not treated until it reaches the sewage plant so if sewers leak or back-up, untreated sewage enters the environment.

The problem with monitoring for disease-causing pathogens is that it only takes a very few, very small organisms to infect a person.  The strategy is to look for more common micro-organisms of sewage that are potentially associated with pathogens.
 
 

Fecal coliform bacteria are used as indicators. They are not usually harmful, but are very common in the human gut. They do not reproduce outside of the gut, so their presence in the environment indicates the input of feces.
However, fecal coliform as an indicator is not a perfect indicator of sewage because it occurs in the guts of all warm-blooded animals (birds and mammals).

How does one establish the source of a pollutant given the complexity of the environment and the difficulties in measuring that pollutant?

 

Acworth study conclusions:

Major source of bacteria was not from ducks and geese along the lake, but from water enterng the lake from the creeks that drain the watershed. For example:

• correlations of bacterial concentrations within the lake with incoming storm water from creeks, not with location of ducks.

Distribution of fecal coliform bacteria (FCB/100 ml) in Lake Acworth
• calculations indicate that many more ducks and geese would be needed to account for the levels measured throughout the lake, though bacteria in creeks entering the lake could account for bacterial levels in the lake.