Biological Contaminants Breakdown

Potential Contaminant

Contamination Source

Health Standard

Human and Environmental Effects

Blue-Green Algae

Naturally occurring but generally compete well in low light conditions; warm temperatures; and high nutrient concentrations. Presence of gas vacuoles and nitrogen fixing ability enhance competitive nature.


Diarrhea, vomiting, and nausea, if consumed. Potentially poisonous blooms affecting humans have been attributed to Anabaena, a blue-green heterocystic filamentous algae; can cause odor in clarified drinking water. Surface blooms; increased organic matter upon decomposition; release of toxic chemicals; noxious odors in some species; not readily cycled through grazer food chain thus decreased food sources for primary consumers.


Cryptosporidium is a microscopic waterborne parasite. It can be spread by person to person contact; handling of fecal material; drinking water or eating food contaminated with the oocysts.


Watery diarrhea, abdominal cramps, nausea, weight loss, low grade fever.

Fecal Coliform Bacteria (E. coli)


Total Coliform

Human sewage; animal wastes; septic systems.


Total Coliform is an
indicator organism  

Membrane filter - less than 1/100ml. Fermentation tube - no coliform presence allowed.

For coliform bacteria: may include diarrhea, cramps, nausea, and other gastrointestinal problmes.


Giardia lamblia, which is found in untreated water and carried by human or animal fecal matter. Round hardened cyst is ingested by other humans, animals.

no MCL

Diarrhea, intestinal gas, nausea, and abdominal cramps; generally not fatal.


Inhalation of contaminated air.

no MCL

Pneumonia-type symptoms

Other Bacteria

Human sewage; animal wastes; septic systems.


In households, cause staining, unpleasant odors and taste. Pathogenic bacteria may cause gastrointestinal illness and influenza-like illnesses when ingested.

Heterotrophic and Autotrophic bacetria can create severe problems with taste, odor, and appearance


Septic tanks; human sewage; animal waste. Possibly disposal of municipal water, sludge application to land, landfill oxidation ponds, or deep well injection of sewerage.

No MCL; EPA imposed treatment requirements that public utilities must use to remove or inactivate pathogens.

Hepatitis A one of most frequently reported viruses in water causing fever, nausea, diarrhea, and hepatitis. Other viruses imposing health threat include poliovirus, Norwalk, adenovirus, and retrovirus. Over 110 types of human enteric viruses identified.

Primary Drinking Water Standards
Secondary Drinking Water Standards
Maximum Contaminant Levels
New Publication from Wilkes University (pdf file)

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