Monitoring the community structure of wastewater treatment plants: a comparison of old and new techniques

Wastewater treatment is a process of increasing importance in a world with an ever growing human population. Today, most wastewater treatment processes make use of the natural self-purification capacity of aquatic environments which is the result of the presence and action of microbial communities. Consequently, wastewater treatment facilities are designed to maintain high densities and activities of those microorganisms that satisfy the various purification demands. The performance, at least of large plants, has to be constantly monitored and is subject to strict regulation. Nevertheless, malfunctions resulting in decreased purification efficacy are frequent. This has, over the decades, prompted many microbiologists to compare the structure, dynamics and function of these `good' or `bad', but always complex, microbial communities. Part of these studies was targeted to a basic understanding of the various processes, another part, however, deals with the monitoring of community structure as a means to direct the plant operation towards higher elimination rates and overall stability. Even though the last decade has seen a molecular revolution in microbiology, the standard methods for monitoring wastewater treatment plants still rely on the tools available to the researcher at the beginning of this century, the microscope and agar plates. It is the goal of this MiniReview to compare the potential of the newly available molecular methods with the old monitoring techniques.