Table 2.

A multiple linear regression to predict OP concentrations

	Legionella	Mycobacterium	Pseudomonas	V. vermiformis	Total OPs
Overall regression model	R² 0.551; p-value < 0.001^*	R² 0.422; p-value 0.002^*	R² 0.436; p-value 0.001^*	R² 0.290; p-value 0.048^*	R² 0.542; p-value < 0.001^*
Water temperature (°C)	B −0.102; p-value 0.002^*	B 0.019; p-value 0.499	B −0.014; p-value 0.559	B 0.002; p-value 0.949	B −0.038; p-value 0.063
pH	B 0.664; p-value 0.265	B 0.085; p-value 0.873	B 0.659; p-value 0.157	B −1.530; p-value 0.024^*	B 0.588; p-value 0.126
Total chlorine residual (mg Cl₂·L⁻¹)	B −0.338; p-value 0.012^*	B −0.488; p-value < 0.001^*	B −0.201; p-value 0.051	B −0.206; p-value 0.158	B −0.201; p-value 0.019^*
Free ammonia (mg N·L⁻¹)	B 1.425; p-value 0.037^*	B −0.879; p-value 0.147	B 1.385; p-value 0.010^*	B 0.151; p-value 0.838	B 1.276; p-value 0.004^*
Nitrite (mg N·L⁻¹)	B 5.272; p-value 0.383	B −3.346; p-value 0.538	B 0.201; p-value 0.966	B 8.089; p-value 0.231	B 2.671; p-value 0.489
THMs (μg·L⁻¹)	B −0.015; p-value 0.019^*	B 0.003; p-value 0.572	B −0.009; p-value 0.053	B −0.014; p-value 0.048^*	B −0.010; p-value 0.014^*
HAAs (μg·L⁻¹)	B −0.020; p-value 0.139	B −0.029; p-value 0.018^*	B −0.014; p-value 0.184	B 0.016; p-value 0.271	B −0.012; p-value 0.148

Statistical analysis: SPSS (missing values: pairwise deletion). The seven physicochemical water quality parameters were independent variables in the regression. Unit for OP concentrations: log₁₀(GCN·L⁻¹). GCN: Gene copy number or genome copy number. B: Unstandardized coefficient.

^*:

Significant correlation (i.e., p < 0.05).