"A set of indicator methods to evaluate the hygienic performance of normal operating biowaste composting plants was developed. The indicator methods were developed by investigating temperature measurements from indirect process tests(...)."
https://www.woodsend.org/pdf-files/jurgen-martens-FINAL.pdf
"Some of the bioassays and indicator methods are fairly simple while others require extensive laboratory support."
http://tinyurl.com/ks4mv5w
"Relatively simple and inexpensive indicator methods are available for
routine monitoring of the microbiological safety of water and the efficiency of treatment processes. "
http://www.who.int/water_sanitation_health/dwq/S03.pdf
"An initial review of methods which can be used to represent a site in a numerical model was carried out. Indicator methods appear to be the most promising. Indicator methods have been used for several years in mining studies and are finding increasing application in the water resources and petroleum industries. "
http://cordis.europa.eu/project/rcn/2924_en.rtf