486
Discussion
4. HERMANN, E.R., and GLOYNA, E.F. (1958) "Waste Stabilization Ponds, Part I. Experimental
Investigations, "Sewage and Industrial Wastes, 30, 511-538. Also (1957) University of Texas
Report to Atomic Energy Commission No. AECU-3481.
Reply
This discussion shows that diurnal variation patterns of redox potential exist for ponds under
different environmental conditions. The patterns illustrated for both experimental and field studies are
not as marked as those found in the Mangere Oxidation Ponds where far greater negative values were
recorded. This is due to-the maturity of our ponds which have also been subjected to a continuous
loading 110 lbs BOD/acre/day for the last few years.
The relationship between sulphide and redox potential mentioned by the discussors is most
interesting and further investigation of these variables and pond instability is warranted.
I. Unger, Canada.
Did you attempt to relate temperature changes to changes in Eh? The changes in Eh could well be
explained by the Nernst equation and temperature change. Although concentration was not measured
the concentration ratio (ox)/(red) must have been measured.
Reply
No. It is considered that temperature would influence the diurnal pattern only in a general manner
as seen in the differences between normal summer and winter curves. The general term 'concentration'
can be misleading; for example the populations of algae and/or bacteria can be expressed as
numbers/ml but these figures do not always relate to their metabolic activity. They may be moribund
although their numbers may be high. Redox potential measurements, however, give a better idea of
'activity' in relation to the microorganisms present, or as you would put it the concentration ratio is
directly related to biological activity.
J. Blok, Netherlands.
Since methane forming bacteria are susceptible to toxicants, can this be used as a rapid
measurement of inhibition of activity?
Reply
I do not see why not. I refer you to the work of Dirisian, Molof & Borchardt
l and Grune &
Chueh
2 who used redox potential as a means of monitoring anaerobic digestion.
1 Dirisian H.A., Molof H.A. and Borchardt J.A. (1963), 'Electrode Potentials Developed during Sludge
Digestion'. Journal Water Pollution Control Federation, 35,4, 424-439
2 Grune, W.N. and Chueh C. (1958) 'Redox Potentials in Waste Treatment - Laboratory Experiences
and Applications'. Journal Water Pollution Control Federation, 30,4, 479-502.
Discussion
4. HERMANN, E.R., and GLOYNA, E.F. (1958) "Waste Stabilization Ponds, Part I. Experimental
Investigations, "Sewage and Industrial Wastes, 30, 511-538. Also (1957) University of Texas
Report to Atomic Energy Commission No. AECU-3481.
Reply
This discussion shows that diurnal variation patterns of redox potential exist for ponds under
different environmental conditions. The patterns illustrated for both experimental and field studies are
not as marked as those found in the Mangere Oxidation Ponds where far greater negative values were
recorded. This is due to-the maturity of our ponds which have also been subjected to a continuous
loading 110 lbs BOD/acre/day for the last few years.
The relationship between sulphide and redox potential mentioned by the discussors is most
interesting and further investigation of these variables and pond instability is warranted.
I. Unger, Canada.
Did you attempt to relate temperature changes to changes in Eh? The changes in Eh could well be
explained by the Nernst equation and temperature change. Although concentration was not measured
the concentration ratio (ox)/(red) must have been measured.
Reply
No. It is considered that temperature would influence the diurnal pattern only in a general manner
as seen in the differences between normal summer and winter curves. The general term 'concentration'
can be misleading; for example the populations of algae and/or bacteria can be expressed as
numbers/ml but these figures do not always relate to their metabolic activity. They may be moribund
although their numbers may be high. Redox potential measurements, however, give a better idea of
'activity' in relation to the microorganisms present, or as you would put it the concentration ratio is
directly related to biological activity.
J. Blok, Netherlands.
Since methane forming bacteria are susceptible to toxicants, can this be used as a rapid
measurement of inhibition of activity?
Reply
I do not see why not. I refer you to the work of Dirisian, Molof & Borchardt
l and Grune &
Chueh
2 who used redox potential as a means of monitoring anaerobic digestion.
1 Dirisian H.A., Molof H.A. and Borchardt J.A. (1963), 'Electrode Potentials Developed during Sludge
Digestion'. Journal Water Pollution Control Federation, 35,4, 424-439
2 Grune, W.N. and Chueh C. (1958) 'Redox Potentials in Waste Treatment - Laboratory Experiences
and Applications'. Journal Water Pollution Control Federation, 30,4, 479-502.