By: Mike Baumgartner, ARWA Wastewater Technician

One of the most important tools used in pro-cess control of an activated sludge plant is the microscope. Because microorganisms follow distinct patterns in all activated sludge systems, it is possible to determine the operating characteristics of various biological systems by performing microscopic exams. A microscope with a reasonable resolution of 100 power will suffice. A slide needs to prepared using 1-2 drops of mixed liquor on a clean glass slide with a cover plate.

During the initial viewing, you should look for a few key items. They include: Floc structure (dispersed or overgrown), Floc color and Types of Indicator organisms. Remember, bacteria are the most important group of microorganisms but are too small to see. There is staining methods used with microscopes but that is for another discussion. Indicator organisms are what is concentrated on. Those are the Protozoa which consist of Flagellates, Free swimming ciliates and Stalk ciliates. And of course, we can’t leave out the Rotifer.

Observation of these indicator organisms can reveal characteristics of the activated sludge. It is important to be able to recognize a good, healthy activated sludge as seen through the microscope. An abundance of or a sud-den loss of any of the indicators will tip off the operator that trouble is heading his or her way.

For example: A sudden loss of Protozoa indicators can result from anaerobic conditions (Dissolved Oxygen Too Low) or a toxic shock condition. An abundance of Rotifers is an indication that you are stable but heading toward an older sludge. I could go on and on. Let’s end the conversation by saying that recognizing key microor-ganism indicators is only possible from repeated observations of various activated sludges. With experience, it is possible to analyze any activated sludge process performance from microscopic examinations.

First appeared in Waterline, Summer 2017

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