Which method is NOT suitable for testing water quality?

The method of testing water quality that is based solely on visual assessment is not suitable because visual observations alone cannot provide a comprehensive evaluation of water quality. Factors such as the presence of dissolved contaminants, microbial life, chemical composition, and specific substances present in the water cannot reliably be detected or quantified by sight. While visual assessments can indicate some issues, such as turbidity or color, they lack precision and cannot replace thorough testing methods that involve chemical analysis or instrumentation.

On the other hand, using standardized test kits, conducting lab analysis on water samples, and utilizing field testing with portable devices are all appropriate methods for assessing water quality. Standardized test kits are designed to measure specific parameters accurately and reliably. Lab analysis allows for detailed examination and can identify a wide range of contaminants at precise levels. Field testing with portable devices offers immediate results that can help operators make quick decisions to ensure water safety.