Phoenix meter readings may vary how much from theoretical conductivity?

The correct answer reflects that Phoenix meter readings are allowed to vary by as much as 0.3 from theoretical conductivity. This tolerance level is important in the context of water treatment processes, where precise measurements of conductivity can impact system efficiency and treatment outcomes. Conductivity readings can be influenced by various factors, including temperature fluctuations, the presence of dissolved solids, and instrument calibration.

A variance of 0.3 ensures that operators can account for minor discrepancies that may arise from real-time operational conditions without compromising the overall assessment of water quality. Understanding this threshold is crucial for maintaining optimal system performance and ensuring compliance with regulatory standards.

Other options suggest narrower ranges, which may not adequately account for the complexities involved in real-world measurements and the operational variances that may occur in the water treatment process.