Fate and transport of bacteria in manure managed in an anaerobic digester

Background

It has been well documented that the process of anaerobic digestion of manure results in a reduction of common bacteria by 85% or more.

Approach

Manure samples were collected prior to and after anaerobic digestion twice a month for one year to evaluate the reduction in generic E. coli and Enterococcus bacteria.

• The generic E. coli represented a bacteria that is relatively “less hardy” while the enterococcus represented a bacteria that is relatively “more hardy” (below).
  
• Anaerobically digested manure and raw dairy manure were applied to grass fields (see illustration at right) to monitor the bacteria die-off pattern of each manure source.

Conclusions

• Greater than 90% reduction in bacterial content of post-AD manure.
• No selection of bacteria in AD for “super bug” status.
• Johnes still present post-AD.
• No growth of bacteria when AD manure is stored in the lagoon.
• Lower number of bacteria in surface-applied AD manure