Which method for measuring free chlorine residual is considered the quickest and simplest?

The DPD colorimetric method is recognized as the quickest and simplest way to measure free chlorine residual in water. This method utilizes a chemical indicator, specifically DPD (N,N-diethyl-p-phenylenediamine), which produces a color change when it reacts with free chlorine. The intensity of the resulting color is then measured against a color standard or by a colorimeter, allowing for a straightforward determination of chlorine concentration.

This method is favored because it provides immediate results, often within minutes, and does not require complex equipment or extensive sample preparation. Its simplicity makes it accessible for use in field measurements, ensuring that operators can quickly assess chlorine levels to maintain water quality and safety.

In contrast, methods like membrane filtration, electrochemical, and spectrophotometric approaches may involve more intricate procedures or equipment, making them less ideal for rapid testing situations where quick decision-making is essential.