ABC Technical Proficiency and Best Practices 5

Question 1

Which operational parameter is used to control the age of biological solids in an activated sludge system?

Accepted Answer

Sludge retention time (SRT) also called mean cell residence time

Answer

SRT (or MCRT) controls how long biological solids remain in the system, directly affecting microbial community composition and treatment efficiency.

Question 2

A drinking water system detects a total coliform-positive sample. Under the Total Coliform Rule, the operator must first:

Accepted Answer

Collect repeat samples within 24 hours from the same site and adjacent sites

Answer

The TCR requires repeat samples be collected within 24 hours from the original site plus at least two adjacent sampling points to determine if the positive is isolated.

Question 3

An operator needs to calculate the chlorine dose required to achieve a 2.0 mg/L residual in a reservoir that has a chlorine demand of 3.5 mg/L. What dose is required?

Accepted Answer

5.5 mg/L

Answer

Chlorine dose = demand + residual = 3.5 + 2.0 = 5.5 mg/L; the dose must satisfy both the demand and leave the desired residual.

Question 4

In wastewater treatment, which test is used to estimate the oxygen demand of slowly biodegradable or non-biodegradable organic compounds?

Accepted Answer

Chemical oxygen demand (COD)

Answer

COD measures all oxidizable material chemically, including compounds resistant to biological breakdown that BOD5 would not fully capture.

Question 5

When should an operator use a portable gas detector before entering a wet well?

Accepted Answer

Before every entry regardless of previous conditions

Answer

Atmospheric conditions in confined spaces like wet wells can change rapidly, so testing before every entry is required regardless of prior safe entries.

(ABC) Association of Boards of Certification Practice Test

(ABC) Association of Boards of Certification Practice Test

ABC Technical Proficiency and Best Practices 5