Home\Educate\Water Reuse 101\Research Projects\Year\2013\Examination of Microbiological Methods for Use with Reclaimed Waters

Examination of Microbiological Methods for Use with Reclaimed Waters

Project: 07-01
Year Released: 2013
Type: White Paper

Program: Principal
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board, Water Research Foundation
Total Investment: $305,304 (Cash: $199,694, In-Kind: $105,610)

Principal Investigators: Patrick K. Jjemba, Ph.D., American Water, Zia Bukhari, Ph.D., American Water and Mark W. LeChevallier, Ph.D., American Water


Microbiological methods have not been validated for use in reclaimed water and their performance characteristics and variability are mostly unknown.

Goals and Objectives

The project reviews the methods used for microbial analyses, determine the microbiological methods currently used by the reclaimed water industry, develop a systematic process for selecting appropriate methods, and develop a framework for round-robin testing of microbiological methods by the industry.

Research Approach

An online survey was sent to 425 individuals within the US, Australia and Singapore. More than 600 genera were also screened for their possible association with reclaimed water using three search engines (Biosis, PubMed, and Web of Science) and some grey literature to prioritize 20 organisms. For the 20 priority organisms, a matrix of method and performance characteristics was developed and considered parameters such as availability of commercial test packages/kits, turn-around time, need for specialized training, recovery rates, sensitivity, specificity, holding time requirements, cost, and validation at more than one laboratory (i.e., round-robin testing). These preliminary findings were used to develop a toolkit for assisting the industry to pick suitable methods for detecting pathogens. The results were shared with a diverse panel of 30 experts (a mix of utility, regulators, engineers, and research scientists) who convened in a workshop to develop a framework for round-robin testing.

Findings and Conclusions

This report describes the state of the science regarding the methods currently used to detect microorganisms in water, with a specific emphasis on reclaimed water matrix, and protocols to validate these methods using round-robin testing. The report includes the most relevant findings from the literature review and a survey. It also highlights newer methods that have a potential for use in routine monitoring programs but are not fully developed for that application.

An accompanying electronic report entitled Examination of Microbiological Methods for Use with Reclaimed Water—Comprehensive Report provides the detailed literature review, details of the survey, details of the workshop activities and findings, as well as the details of the database, including how that database is used. The accompanying report also summarizes the conventional and more recent methods.

The study identified 148 methods for detecting microorganisms. An Access database was developed as a decision-making tool to aid utilities in selecting the best method for detecting organisms. The user-friendly database was designed in a way that the numbers and weighting can be changed based on user preferences using the “Customize Score” button. The database is provided on a CD accompanying this report or can be downloaded. Plant operators, regulators, and scientists can readily use it to decide what method(s) to apply to detect any of the 20 priority organisms in reclaimed water. With a set of drop-down options, users can search on one to four selection criteria, namely:

  • the name of the organism,
  • the name of the method,
  • the cost range (low, moderate or high); and
  • whether the method is capable of determining organism viability.

For any organism with multiple methods, the user can also compare methods based on their aggregate score.

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