Which type of analysis method usually requires equipment calibration and maintenance?

The type of analysis method that typically necessitates equipment calibration and maintenance is automatic sampling. This method involves using automated devices to collect samples of wastewater at designated intervals or flows, allowing for more consistent and efficient sampling over time. Given that these devices are sophisticated and depend on precise measurements, they require regular calibration to ensure accuracy in the sampling process.

Additionally, maintenance is crucial for automatic samplers since mechanical components can wear out, and electronic systems may require updates or troubleshooting to function optimally. Ensuring that the equipment operates correctly is vital because inaccurate sampling can lead to flawed data that affects the assessment and treatment of wastewater.

In contrast, manual sampling involves physically collecting samples by an operator, which does not rely on complex equipment, and therefore lacks the need for calibration and maintenance of devices. Composite sampling combines various samples over time or flow but too does not generally require continuous equipment maintenance. Visual inspection relies solely on human observation and requires no specialized instruments or calibration. Thus, it is automatic sampling that stands out due to its reliance on calibrated and maintained equipment for effective operation.