Which method can be used to evaluate an aerobic treatment plant for excessive solids?

The method used to evaluate an aerobic treatment plant for excessive solids is the 30-minute settling test. This test assesses the settling characteristics of solids present in the wastewater. By measuring the volume of solids that settle out of a sample over a specified period, this test can reveal whether the plant is capable of effectively removing solids from the wastewater. An elevated amount of settled solids may indicate problems in the treatment process, such as inadequate aeration or insufficient microbial activity.

Other tests, such as the DO test (dissolved oxygen), primarily measure the oxygen present in the water rather than the amount of solids. The BOD5 analysis, which measures the biochemical oxygen demand over five days, assesses the organic matter content but does not specifically evaluate solids. The chlorine residual test measures the amount of chlorine remaining in the water after disinfection and is unrelated to solids evaluation. Thus, the 30-minute settling test stands out as the most relevant method for identifying issues related to excessive solids in aerobic treatment plants.