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Table 2 Calculations for determining L. pneumophila distribution across various system compartments and effects of operating conditions

From: Water heater temperature set point and water use patterns influence Legionella pneumophila and associated microorganisms at the tap

Analysis

Calculation

Practical meaning/interpretation

Temperature effect on total planktonic loads (Table 3)

\( \frac{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Distal}}\times {\forall}_{\mathrm{Distal}}+{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Recirc}}\times {\forall}_{\mathrm{Recirc}}\right)}_{\mathrm{Control}}}{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Distal}}\times {\forall}_{\mathrm{Distal}}+{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Recirc}}\times {\forall}_{\mathrm{Recirc}}\right)}_{\mathrm{Experimental}}} \)

Factor by which planktonic L. pneumophila increase in the total system if the temperature is not elevated to the experimental setting

Temperature effect on the recirculating line and tank loads (Table 4)

\( \frac{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Recirc}}\times {\forall}_{\mathrm{Recirc}}\right)}_{\mathrm{Control}}}{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Recirc}}\times {\forall}_{\mathrm{Recirc}}\right)}_{\mathrm{Experimental}}} \)

Factor by which planktonic L. pneumophila increase in the recirculating portions of the system if the temperature is not elevated to the experimental setting

Temperature effect on distal tap loads (Table 3)

\( \frac{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Distal}}\times {\forall}_{\mathrm{Distal}}\right)}_{\mathrm{Control}}}{{\left({\displaystyle \sum }{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Distal}}\times {\forall}_{\mathrm{Distal}}\right)}_{\mathrm{Experimental}}} \)

Factor by which planktonic L. pneumophila increase at the tap if the temperature is not elevated to the experimental setting

Re-growth in the recirculating lines (Fig. 3)

[Lp]Recirc − [Lp]Inf

Re-growth in the recirculating lines relative to the influent

Concentration (Fig. 4a)

[Lp]

L. pneumophila concentration

Factor increase (Fig. 4b)

\( \frac{{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Distal}}}{{\left[\mathrm{L}\mathrm{p}\right]}_{\mathrm{Recirc}}} \)

Re-growth in the distal taps relative to the recirculating line

Weekly yield (Fig. 4c)

[Lp]Distal × Distal × Use

Total amount of L. pneumophila delivered at the tap per week

Biofilm re-growth (Fig. 5)

L. pneumophila in gene copies/cm2

Biofilm densities of L. pneumophila; because the same areas were re-swabbed, any L. pneumophila detected is assumed to have re-established during that experimental condition

  1. Lp: L. pneumophila concentration in gene copies/mL, Distal distal tap, Recirc recirculating line and tank, volume, Inf influent, Use use per week (21, 3, or 1)