Which of the following best describes the operational challenge of automatic samplers?

The selection of the statement regarding the need for cleaning and calibration accurately highlights a significant operational challenge associated with automatic samplers. These devices are designed to collect samples over time without direct human interference, which makes them incredibly useful for monitoring water quality and other parameters in wastewater systems. However, maintaining their accuracy and reliability requires regular cleaning to prevent contamination and the buildup of residues that could alter sampling results. Calibration is equally important to ensure that the measurements taken by the sampler are precise and reflect actual conditions.

Both cleaning and calibration ensure that the sampler functions correctly and provides valid data. Neglecting these processes can lead to significant errors in sampling, compromising data integrity vital for regulatory compliance and operational decision-making. Thus, the operational challenge of maintaining the cleanliness and accuracy of automatic samplers is crucial for effective wastewater management.

While other aspects such as speed, power supply management, and the capability to sample only liquids have their own importance, they do not encompass the broader and more critical operational challenges posed by automatic samplers like the need for regular maintenance through cleaning and calibration, which are essential for consistent performance.