The limitations of current pathogen indicators

AWQC Microbiology Research undertook a Water Environment Research Foundation (WERF) Project to investigate process indicators for a range of human pathogens i.e. bacteria, protozoa (Cryptosporidium and Giardia) and viruses in wastewater. Pathogen indicator pairs were identified and their removal or inactivation was investigated in commonly used domestic wastewater treatment processes in Australia, and two sites in both South Africa and the United Kingdom.

The project highlighted the limitations of relying upon current indicators. The majority of indicators currently used to monitor performance such as bacteriophage (viruses that infect bacteria) were found to be unsuitable as a measure for enteric viruses and no traditional indicator was identified for Cryptosporidium.

The project verified the presence of a number of pathogen/indicator pairs that appeared consistently across a range of wastewater treatment plants. Particle profiling was identified as a useful surrogate for indicating the presence of bacteria and protozoans.

Outcomes and benefits from the research project include:

• The project highlighted the limitations of currently used indicators
• It confirmed that pathogens and indicators were consistently present in primary and secondary treated wastewaters and sludge from a range of climatic zones
• Laboratory-scale experiments provided new information on pathogen and indicator removal for a range of tertiary treatment processes
• Particle profiling was identified as a potential rapid and cost effective alternative indicator for the presence of bacteria and protozoans.