WASTEWATER:The operator of an extended-aeration activated sludge treatment facility running at a 10-day solids retention time (SRT) completes a monthly microscopic examination of a sample of mixed liquor suspended solids (MLSS) from the effluent end of the last aeration tank before the clarifiers. He looks at three slides and documents the data in the table below. Based on all the information provided, what is the best assumption about the current plant operating condition?
Organism
Slide 1
Slide 2
Slide 3
Total
Average
Amoeba, blobs
15
18
27
60
20
Amoeba, shelled
1
0
1
2
0.7
Flagellates
21
18
23
62
21
Free-swimming ciliates
15
14
10
39
13
Stalked ciliates
3
4
1
8
2.7
Rotifers
0
2
0
2
0.7
Worms
0
0
0
0
0
Other
0
0
0
0
0A. The facility is running optimally and no changes need to be made.B. The MLSS and SRT are too high and
