Pathogens

Pathogens in Human Feces

There are many pathogens found in human waste, these can prohibit the use of this waste for composting on food gardens. The following table shows the various factors that affect the survival of these pathogens.

Bacteria, Helminths, and Protozoa

The pathogens human faeces consist of bacteria, helminthes, and protozoa. These pathogens are contained in the raw waste but typically do not continue reproducing very far into the composting process due to poor conditions (loss of moisture, temperature, depletion of nutrients, etc.) (Dalsgaard, 2003).  The table below lists the most common pathogens found in human waste.

Viruses

Viruses of the gastrointestinal system can be contained in faecal matter;  if the faeces are combined with blood or urine bloodbourne viruses can also be found in human faeces. The occurrence of dangerous bloodbourne viruses contaminating compost is rare, but important to consider in any case.  The most common virus species and the number of strains of each virus that can be found are listed in the table below.

Raising the temperature of compost can inactivate most viruses. Of the above viruses, the most heat resistant is Hepatitis A, but even this can be denatured after being exposed to 60?C temperatures for only ten hours (Dalsgaard, 2003).  Below is a graph of temperatures and exposure times for the above viruses to become inactive. The pH level of the compost also affects the viruses’ effectiveness. Changing the pH of the compost is not a practical solution because of the wide variety of viruses requiring pH levels of varying acidity and alkalinity. Modifying the pH drastically can also harm helpful bacteria in the compost. Below is a chart of time vs. temperature of the degradation of viruses in compost (Dalsgaard, 2003).

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