Biological Contaminants in Water: What They Are and How to Protect Yourself

Biological Contaminants in Water: What They Are and How to Protect Yourself


Water is an essential component of life. We depend on clean water for drinking, bathing, and cooking. Whether you get your water from a municipal source or a private well, water may contain a range of contaminants. Some of the most common contaminants are invisible without a microscope but have the potential to cause serious illness. This guide will explore three types of biological contaminants and how to protect you and your family from them by using a reverse osmosis water filtration system.

What Are Biological Contaminants?

Contamination can affect the quality and safety of your drinking water. Most people know that drinking water from untreated sources such as ponds, lakes, and rivers can result in life-threatening gastrointestinal illnesses. These same contaminants – living organisms of a biological nature – can also be found in drinking water supplies provided from wells or municipal sources. The three main classes of biological contaminants are:

  • Bacteria
  • Viruses
  • Protozoan Cysts

Public health professionals refer to dangerous organisms in water as waterborne pathogen contamination. This contamination can enter water supplies through animal activity, agricultural runoff, sewage leaks, or natural disasters that compromise water sources. As mentioned in our introduction, these biological contaminants are too small to be seen by the naked eye yet pose a serious health threat if ingested. 

microbes in water

Bacteria in Water Supplies

Bacteria are tiny single-celled organisms that can be found nearly everywhere on Earth. Most bacteria pose little or no threat to health, yet certain organisms may cause severe illnesses if ingested through contaminated foods or water. Some of the most common bacteria contaminating water supplies include:

  • Vibrio cholera
  • Schistosoma
  • Salmonella
  • Clostridium 
  • Campylobacter
  • Legionella
  • E. coli (referred to as fecal coliform bacteria)


Drinking water contaminated with bacteria can cause a wide range of symptoms. Exposure to high levels of bacterial contamination, or delays in seeking treatment, can result in hospitalization or even death. Common symptoms associated with drinking water contaminated by waterborne bacterial pathogens include:

  • Nausea
  • Headaches
  • Vomiting
  • Diarrhea
  • Cramps
  • Fever
  • Fatigue 

Several of these bacteria cause known diseases such as cholera, Legionnaire’s disease, or salmonella poisoning. While most people can fight a gastrointestinal infection from waterborne bacteria with medical assistance, others may not be so lucky. Children, the elderly, and those with weakened immune systems can become seriously ill or die from their infections. 

Viruses in Contaminated Water

Viruses are tiny infectious agents that are the culprits behind many known diseases. Viruses infect a host by injecting genetic material into healthy cells; those cells then replicate the virus, causing illness to spread. What makes viruses in contaminated water so dangerous is their size; viral particles are hundreds of times smaller than bacterial cells, and many typical water filtration systems can allow these particles to pass through the filter element. Only a reverse osmosis system or submicron filter can trap viral contamination. 

Common viruses found in contaminated drinking water supplies include:

  • Hepatitis A and E
  • Enteroviruses, such as those that cause polio or Coxsackie 
  • Astrovirus
  • Rotavirus
  • Norovirus

Common viruses that cause respiratory diseases, such as influenza or coronaviruses, may be found in contaminated water supplies but it is unclear if viral infections can be passed through water contact. 

water contamination illness

As with bacterial contamination, viruses in drinking water can lead to illnesses requiring medical intervention. Victims of viral contamination report nausea, vomiting, and gastrointestinal upsets. Severe infections may affect the function of internal organs and may result in death. 

Protozoan Cysts: Hidden Dangers in Contaminated Water

Although they are less common than bacteria or viruses in drinking water supplies, protozoan cysts still represent a significant health threat. Protozoan cysts are tiny parasitic organisms protected by a hard protein shell. They require passage through an animal’s or human’s digestive system to complete their life cycle. People or animals infected with a protozoan cyst shed the particles in fecal matter; if this matter finds its way into a water supply, the infection can spread rapidly. 

water contaminants

Common protozoan parasites found in drinking water supplies include:

  • Giardia
  • Toxoplasma
  • Entamoeba
  • Isospora
  • Cyclospora
  • Blastocystis
  • Sarcocystis
  • Balantidium

In the United States, the most common of these protozoan parasites is Giardia lamblia, which can cause an intestinal disease known as giardiasis. Protozoan parasites find their way into water sources through agricultural and storm runoff, animal activity, and leaking sewage treatment systems. These infectious pathogens can cause a range of symptoms, including:

  • Diarrhea
  • Unwanted weight loss
  • Dehydration
  • Fever
  • Nausea

It requires the medical administration of powerful antibiotics to combat a protozoan cyst infection. Left untreated, a person could face long-term illness or even death. 

Protecting Against Waterborne Pathogens

We rely on clean, pure water for drinking, cooking, and bathing. Unfortunately, our water supplies may become contaminated, and we might not know until illness spreads. Several methods for treating water are contaminated with biological pathogens, including boiling, ultraviolet sterilization, and filtration.

reverse osmosis system

A reverse osmosis water filtration system is incredibly effective at removing harmful organisms from drinking water supplies. These systems can be used for municipal water sources and private wells. Reverse osmosis is a mechanical process where water is passed under pressure through a semipermeable filter membrane. The filter membrane is equipped with tiny pores that allow water to pass through but trap contaminants. Reverse osmosis (RO) system stops over 99% of all contaminants, including:

  • Bacteria
  • Viruses
  • Protozoan cysts
  • Heavy metals
  • Dissolved minerals
  • Petroleum and pesticide residues
  • Fluoride
  • Chlorine

The RO system is installed between the home water supply and the faucets or fixtures. These systems can process 75 gallons or more of water each day. Advanced systems include multiple filter stages to remove contaminants and to improve water clarity, odor, and taste. Don’t take a chance with contaminated water; a reverse osmosis water filtration system can protect you and your family from the life-threatening illnesses caused by waterborne biological contaminants. 

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