Test Yourself Answer Key

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Editorial Calendar

January ............. Wastewater Treatment

February ........... Water Supply; Alternative Sources

March Energy Efficiency; Environmental Stewardship

April .................. Conservation and Reuse

May ................... Operations and Utilities Management

June .................. Biosolids Management and Bioenergy Production

July Stormwater Management; Emerging Technologies

August .............. Disinfection; Water Quality

September ........ Emerging Issues; Water Resources Management

October New Facilities, Expansions, and Upgrades

November ......... Water Treatment

December ......... Distribution and Collection

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1. C) mixed culture.

Per California State University, Sacramento, Operation of Wastewater Treatment Plants, Volume II, Seventh Edition (Operation of Wastewater Treatment Plants, Volume II), Section 11.1 00, Importance of Microbiology, “The activated sludge process is a living biological process. Activated sludge is made up of many different types of microorganisms, referred to as a mixed culture. (A pure culture would be many microorganisms of the same type.)”

2. C) Grab samples

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.101, Collection of Samples, “Like all other samples collected for laboratory analyses, it is very important to get a representative sample for microscopic observation. These samples should be grab samples from an aeration tank, collected at the same time each day, preferably when the sludge volume index (SVI) grab sample is taken. This will allow you to correlate your microscopic observations with changes in the SVI.”

3. C) At the effluent end of the aeration tank.

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1011, Sampling Location, 1. Conventional Mode, “Regardless of whether you are operating rectangular aeration tanks in parallel or in series. or you have circular tanks, the sample should be taken at the effluent end of the aeration system.”

4. C) filamentous organisms.

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1021, Procedure for Preparing Sample, “There are two types of samples you will be preparing. The first, called a wet mount, will be used for observing live microorganisms; and the second, called a stained dried slide, will be used to observe stained filamentous organisms.”

5. A) Nocardia.

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1031, Microorganisms of Importance, 2.b. Short Filaments, “The most common short filament encountered in activated sludge plants is a type of actinomycete called Nocardia. . . Nocardia does not cause sludge bulking, but is associated with foaming or frothing in the aeration tanks and excessive brown floating scum in the secondary clarifiers.”

6. D) Stalked ciliates

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1031, Microorganisms of Importance, 3. Protozoa; Ciliate, Stalked, “These ciliates grow on a flexible stalk that is attached to a solid particle. . . The presence of stalked ciliates indicates a stable process that produces a low turbidity effluent.”

7. B) Mastigophora

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1041, Undesirable Microorganisms, “Flagellates and amoeboids are almost always present in activated sludge, but their numbers should be very low. Ideally, you should never see tiny flagellates (Mastigophora) nor short filaments (Nocardia). Long filaments are not wanted in large numbers because they prevent good settling of the sludge in the secondary clarifiers.”

8. D) an old activated sludge with a high MCRT and associated with a turbid effluent.

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1031, Microorganisms of Importance, 4. Rotifers, “Rotifers are multicellular animals. . . Rotifers are an indication of an old activated sludge with a high MCRT and are usually associated with a turbid effluent.”

9.

C) is a check to support interpretation of microscopic examination results.

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1042, Comparing Microscopic Results, 1. Laboratory Process Data, “Comparing microscopic results with laboratory process data is a check to support your evaluation and interpretation of the results from your microscopic observation. Example: If you see an upward trend in the numbers of rotifers and very few or no flagellates, the F/M should be decreasing and the MCRT increasing. This is confirmed when the laboratory process data show an upward trend in the suspended solids concentrations in the aeration tanks and a downward trend in the SVI.”

10. A) Once or twice per day

Per Operation of Wastewater Treatment Plants, Volume II, Section 11.1060, Frequency of Microscopic Examination, 2. Poor Operation, “A person in charge of a treatment plant is under a lot of pressure and feels the tension or stress when the activated sludge process is operating poorly. There is a natural tendency to watch the process more closely during periods of poor operation. Microscopic observations should be performed daily or twice per day (morning and afternoon) during times like these.”