EPA Method 1681: Fecal Coliforms in Sewage Sludge (Biosolids) by Multiple Tube Fermentation using A-1 medium .This method is designed to meet the survey and monitoring requirements of the U.S. Environmental Protection Agency (EPA) in regulating the use and disposal of biosolids under 40 CFR Part 503. Method 1681 provides for the enumeration of fecal coliforms in Class A and Class B biosolids using the most probable number (MPN) procedure.

  • Fecal coliform bacteria are gram-negative, non-spore-forming rods that are found in the intestines and feces of humans and other mammals
  • Fecal coliform results are reported as MPN/g total solids (dry weight basis)
  • Class A biosolids contain a fecal coliform density below 1,000 MPN/g of total solids
  • Class B biosolids contain a geometric mean fecal coliform density of less than 2 × 106 MPN/g of total solids

Although there is not a specific number of samples required for Class A biosolids, it is recommended that a sampling event extend over two weeks and that at least seven samples be collected and determined to be below 1,000 MPN/g of total solids (dry weight basis) to qualify as Class A biosolids.

Sampling and Shipping

Analysis of multiple samples collected at the time of disposal using this procedure will satisfy the requirements of the monitoring alternative for demonstrating pathogen reduction in both Class A and Class B biosolids.

Precision of the test increases with increasing numbers of replicates per sample tested.

For fecal coliform samples for sewage sludge (biosolids) only, the holding time is extended to 24 hours for Class A composted, Class B aerobically digested, and Class B anaerobically digested sludge.

Note: client shall verify hold time requirements with their regulatory agency

  • Collect sample in a 250 ml or larger sterile container and refrigerate immediately
  • During transit maintain sample at < 10°C (DO NOT freeze) in a cold insulated cooler with ice/icepacks
  • Include a Chain of Custody with all appropriate information provided