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Ask the Wastewater Expert

Daniel L. Theobald

Known in the industry as “Wastewater Dan,” Daniel L. Theobald, proprietor of Environmental Services, is a professional wastewater and safety consultant/trainer. He has more than 24 years of hands-on industry experience operating many variants of wastewater treatment processing units and is eager to share with others his knowledge about water conservation. (

Microorganisms in activated sludge

Someone recently asked, 'What microorganisms are in activated sludge?'
In the activated sludge process, microorganisms are mixed with waste water. The microorganisms come in contact with the biodegradable materials in the wastewater and consume them as food.
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Activated-sludge troubleshooting guidelines

Someone recently asked, “What are some troubleshooting guidelines or procedures for overall process control of activated sludge?”
Someone recently asked, “What are some troubleshooting guidelines or procedures for overall process control of activated sludge?”
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Procedures for overall process control of activated sludge

To control activated sludge, you need to “have a handle” either on aeration, sludge-wasting or return-sludge flow. Aeration-rate adjustment is probably the simplest way to go, says Wastewater Dan. But he briefly reviews all three methods in today’s blog.
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The measurement of suspended solids

Someone recently asked, “What are the procedures for measuring sludge concentrations and amounts? How is sludge quality determined?”
Sludge quality can be determined by measuring the solids concentration in various tanks, by solids inventories or by determining the sludge-return and wasting flow rates.
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How sludge settles is a key performance indicator

Someone recently asked, 'What are some procedures for measuring settle-ability of activated sludge?'
Collecting samples, use of equipment for simulating settle-ability and the interpretation of results are all part of measuring activated-sludge settle-ability.
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For a firm grasp of trends, monitor wastewater treatment ‘look and feel’

Someone asks, 'What are the parameters relevant to visual and olfactory observation of activated sludge?'
Activated sludge is a biological wastewater treatment that speeds waste decomposition. It is added to wastewater and the mixture, referred to as “mixed liquor,” is aerated and agitated. Subsequently held in a tank, the mixture settles out by sedimentation and is disposed of, i.e., as they say, “wasted,” or returned to the aeration tank as needed. The remaining wastewater then undergoes further treatment.
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Getting back to basics: What is pH?

The most used measure in wastewater treatment, and for good reasons
The “potential of hydrogen” or “pH” is the measure of free hydrogen activity in water and thereby indicative of the measure of its free acidity or free alkalinity. Gauged on a numeric scale of 0-14, solutions with a pH of less than 7.0 are acids. Solutions with a pH greater than 7.0 are bases and solutions with a pH of 7.0 are neutral.
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Batch and continuous pH control compared and contrasted

Someone recently asked, “What are process controls for adjusting and maintaining pH during wastewater treatment?”
The pH is one of the most important and frequently used measurements in wastewater treatment. Dependence of pH occurs in practically every phase of water supply and wastewater treatment, e.g., acid-base neutralization, water softening, precipitation, coagulation, disinfection and corrosion control.
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