38
Discussion
Reply to the discussion by Krenkel & Novotny
Discussors and authors agree that reaeration in rivers as well as compressed air aeration are
diffusion dependent. Relative DO absorption may therefore be described in relation to water
temperature respectively by curve A or curve B in Fig. 8. The authors have also conclused that turbine
aeration and weir aeration disperse air saturated particles in the water by mechanical action. Otherwise
the principle of saturation values could not explain the measured dependency (curve C). A differing
view exists upon the classification of surface aerators. Based on measurements in Fig. 5 the authors
suggest that surface aerators, with energy densities of more than 20 W/m of tank volume, should be
described by curve C in Fig. 8. The hitherto practice frequently assumes curve B. To verify this
important aspect additional measurements in surface aerated tanks would be desirable.
H.A.C. Montgomery, UK.
The oxygen solubility values of Truesdale et al have been shown to be about 3% low because of the
loss of iodine by volatilization in the Winkler method. This is not important in calculating the
percentage saturation because the modifications of the Winkler method commonly used also give low
results. Correct results can be obtained by use of the alkaline iodide reagent of Pomeroy and
Kirschman which provides a much higher concentration of iodide.
Discussion
Reply to the discussion by Krenkel & Novotny
Discussors and authors agree that reaeration in rivers as well as compressed air aeration are
diffusion dependent. Relative DO absorption may therefore be described in relation to water
temperature respectively by curve A or curve B in Fig. 8. The authors have also conclused that turbine
aeration and weir aeration disperse air saturated particles in the water by mechanical action. Otherwise
the principle of saturation values could not explain the measured dependency (curve C). A differing
view exists upon the classification of surface aerators. Based on measurements in Fig. 5 the authors
suggest that surface aerators, with energy densities of more than 20 W/m of tank volume, should be
described by curve C in Fig. 8. The hitherto practice frequently assumes curve B. To verify this
important aspect additional measurements in surface aerated tanks would be desirable.
H.A.C. Montgomery, UK.
The oxygen solubility values of Truesdale et al have been shown to be about 3% low because of the
loss of iodine by volatilization in the Winkler method. This is not important in calculating the
percentage saturation because the modifications of the Winkler method commonly used also give low
results. Correct results can be obtained by use of the alkaline iodide reagent of Pomeroy and
Kirschman which provides a much higher concentration of iodide.