Managing Bacteria in Activated Sludge
Waste Water Treatment Plants

The BDC 990 in Activated Sludge Waste Treatment Plants

Problems of concern in activated sludge waste treatment plants:

1.             Intrusion of toxic materials

2.             Proliferation of filamentous bacteria

3.             Prediction of 5 day BOD results

4.          Testing influents for suspected toxic activity

 Solutions:  With the introduction of the BDC 990 automatic online analyzer, the noted problems are addressed.  With biological test results available on an almost continuous basis, response to these situations can be implemented in a timely manner.  The BDC 990 also does other tests along with the bacterial activity, testing a complete chemical profile of the system and sending its results automatically to the plant’s computer along with graphs, trend lines etc;.  The machine sits by the system and does its tests at whatever frequency desired by the plant operator, stores the data and cleans itself, then waits until time to do the next profile.  To access the data, the operator just hits a key on his computer in the plant office.

 Intrusion of toxic materials

Whenever toxic materials are introduced or a low-nutrient situation arises the activity of the working bacteria will diminish precipitously.  This change will be registered on the BDC 990 and the data will be in the operator’s computer in minutes, allowing therapy to be administered quickly.

 Proliferation of filamentous bacteria

When filamentous bacteria gain in population, it is at the expense of the working organisms.  Since filamentous organisms use Oxygen, but are poor in the reducing enzymes measured by the BDC 990, a gradual diminishing of the readings will occur, diagnostic of this situation.  Oxygen measurements are much slower and less sensitive to this development.

 Prediction of 5 day BOD results

Most episodes of increased BOD levels in the effluent of activated sludge units are the result of carryover of biological solids which will have some small amount of biological activity.   Effluent with no biological activity will give a negligible reading on the BDC 990, whereas even the slightest amount of activity will register.  Once a correlation is established for a plant, a threshold for action can be established.

 Toxicity Analysis

A bonus for plant operators is offered by the capacity of the BDC 990 to run its tests on demand.  Toxicity of suspicious materials can be tested in this manner just by manipulating the menu from the keypad.  To test a suspect material in this manner, one just does the following: 

   1. Analyze the bacteria level of the plant’s working basin.
   2. Add differing amounts of the suspected toxic material to different samples from the basin.
   3. Let these sit for a few minutes
   4. Test these contaminated suspects by the procedure above.
   5. Compare results with the original sample….a decrease indicates toxicity

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