Field Test and Inspection Procedures Flashcards

When collecting a water sample for bacteriological analysis, what is the minimum flush time before sample collection from a chlorinated distribution tap?

Answer: 2–3 minutes

Taps must be flushed 2–3 minutes to clear standing water and obtain a representative distribution sample.

A Hach DR spectrophotometer reads a chlorine residual of 0.00 mg/L in a distribution sample. The first troubleshooting step should be:

Answer: Replace the reagent powder pillow and re-test

Depleted or expired DPD reagent is the most common cause of a falsely zero chlorine reading.

What field parameter is used to estimate the carbonate-bicarbonate equilibrium and corrosivity of a water supply?

Answer: Langelier Saturation Index (LSI)

The Langelier Saturation Index indicates whether water will tend to deposit scale or corrode pipe materials.

Which instrument measures the dissolved oxygen concentration directly without the need for chemical titration?

Answer: Membrane electrode DO meter

A membrane electrode (polarographic or galvanic) DO meter measures oxygen electrochemically in the field.

During a wastewater effluent inspection, the inspector notices a persistent oily sheen on the receiving stream. The FIRST regulatory concern is:

Answer: Violation of oil and grease discharge limits

An oily sheen indicates a possible oil and grease permit exceedance and must be documented and reported.

A composite sample for wastewater analysis is best described as:

Answer: Multiple grab samples combined proportionally over time or flow

Composite samples integrate flow or time variations, providing a more representative average concentration than a single grab.

What is the maximum holding time for a chlorine residual field measurement once the sample is collected?

Answer: Immediately — analyze on-site only

Chlorine residual degrades rapidly after collection and must be measured immediately at the sampling point.