402
Discussion
advance in activated sludge treatment technology. However, the paper describes several related
processes simultaneously, and does not distinguish one from the other to permit ready comparison of
this particular pure oxygen application with other methods of using pure oxygen, or even with
conventional practice. For example, sludge stabilization with pure oxygen is introduced in the
evaluation, as is the addition of ozone.
The major difficulty with the paper is that it is based upon a proprietary oxygenation unit that is
purported to accomplish high oxygen transfer in a conventional aeration tank so that the tank does
not need to be covered to reclaim unabsorbed oxygen gas. It is claimed that 95% absorption of pure
oxygen was obtained in a 5-ft deep tank containing activated sludge with 8,000 mg/1 solids. However,
nowhere in the paper is this device described nor are the data for the oxygenation studies provided.
Therefore, in making a judgment of the process, the reader is obligated to take all assertions on faith.
While the use of propreitary equipment is acceptable, the scientific and professional community
cannot be expected to make judgments without full knowledge of the device and the data collected in
its use. In fact, this writer is surprised that the International Association on Water Pollution Research
would accept a paper based upon equipment and data that are not disclosed.
This writer agrees with the author that a device that provides a " . . . transfer rate, which is
approximately six times more efficient than other known oxygenation methods, opens up new
horizons for low cost wastewater treatment." However, nothing is said about the cost of the device,
problems with its maintenance, nor, most importantly, its power requirements. Many aeration devices
now available can provide extremely high oxygenation efficiencies if unlimited power is utilized in
their operation. If the savings in pure oxygen achieved with a high absorption efficiency unit demand
more than the equivalent amount of power in driving the oxygenation unit, nothing is gained.
The other data provided in the paper are either not adequate to make comparisons with
conventional practice or with other oxygen-using processes, or the comparisons when made are not
valid. For example, in Table 2, the pure oxygen system operated in a 5-gpm pilot plant is compared
with the full-scale Metro Denver Plant. A preliminary estimate of capital cost savings that might be
realized by using the new technology is included in the paper; however, the basis for this cost
comparison is not provided and, in addition, ozonation is included in the comparison which clouds the
evaluation of the pure oxygen process.
Furthermore, in making the comparisons, nothing is said about operation and maintenance, so that
the indicated savings in capital cost may well be outweighed by higher operating costs. The major cost
involved in producing oxygen, and perhaps in applying it in this proprietary method, is for power.
Also, power is a significant cost factor in the production of ozone. Evaluations based on capital
investment alone are quite misleading.
Conclusion
The writer hopes that the device upon which this paper is based is a valuable addition to the
armamentarium available for wastewater treatment. Perhaps the full-scale treatment units that were
under consideration at the time the paper was written will provide a sound basis for evaluation and
comparison of this process with conventional practice and with other new pure oxygen technology.
REFERENCES
ALBERTSSON, J.G., et al, McWHIRTER, J.R., ROBERTON, E.K., VAHLDIECK, N.P., (1970)
"Investigation of the Use of High Purity Oxygen Aeration in the Conventional Activated Sludge
Process," Water Pollution Control Research Series, 17050 DNW 05/70 Advanced Waste Treatment
Research Laboratory, Cincinnati, Ohio.
BUDD, W.E. and LAMBETH, G.F. (1957) "High-Purity Oxygen in Biological Sewage Treatment,"
Sewage and Industrial Wastes, Vol. 29, No. 3, 237.
COHEN, D.B. (1971) "A Low Cost Open Tank Pure Oxygen System for High Rate Total Oxidation,"
Metrolopitan Denver Sewage Disposal District No. 1, prepared for presentation at the International
Waster Pollution Research Association Conference in Jerusalem, 1972.
OKUN, D.A. (1948) "Pure Oxygen and Bioprecipitation Process may Reduce Sewage Treatment
Costs," Civil Engineering, Vol. 18, 288.
OKUN, D.A. (1949) "Systems of Bio-precipitation of Organic Matter from Sewage," Sewage Works
Journal, Vol. 21, No. 5. 763.
W.F. Garber, USA
The following points need consideration. The biological culture established by pure oxygen is
temperature sensitive and almost complete failure may occur at winter temperatures. This culture is so
specialized that loss of pure oxygen feed for a little as 1-4 hours may result in complete process
Discussion
advance in activated sludge treatment technology. However, the paper describes several related
processes simultaneously, and does not distinguish one from the other to permit ready comparison of
this particular pure oxygen application with other methods of using pure oxygen, or even with
conventional practice. For example, sludge stabilization with pure oxygen is introduced in the
evaluation, as is the addition of ozone.
The major difficulty with the paper is that it is based upon a proprietary oxygenation unit that is
purported to accomplish high oxygen transfer in a conventional aeration tank so that the tank does
not need to be covered to reclaim unabsorbed oxygen gas. It is claimed that 95% absorption of pure
oxygen was obtained in a 5-ft deep tank containing activated sludge with 8,000 mg/1 solids. However,
nowhere in the paper is this device described nor are the data for the oxygenation studies provided.
Therefore, in making a judgment of the process, the reader is obligated to take all assertions on faith.
While the use of propreitary equipment is acceptable, the scientific and professional community
cannot be expected to make judgments without full knowledge of the device and the data collected in
its use. In fact, this writer is surprised that the International Association on Water Pollution Research
would accept a paper based upon equipment and data that are not disclosed.
This writer agrees with the author that a device that provides a " . . . transfer rate, which is
approximately six times more efficient than other known oxygenation methods, opens up new
horizons for low cost wastewater treatment." However, nothing is said about the cost of the device,
problems with its maintenance, nor, most importantly, its power requirements. Many aeration devices
now available can provide extremely high oxygenation efficiencies if unlimited power is utilized in
their operation. If the savings in pure oxygen achieved with a high absorption efficiency unit demand
more than the equivalent amount of power in driving the oxygenation unit, nothing is gained.
The other data provided in the paper are either not adequate to make comparisons with
conventional practice or with other oxygen-using processes, or the comparisons when made are not
valid. For example, in Table 2, the pure oxygen system operated in a 5-gpm pilot plant is compared
with the full-scale Metro Denver Plant. A preliminary estimate of capital cost savings that might be
realized by using the new technology is included in the paper; however, the basis for this cost
comparison is not provided and, in addition, ozonation is included in the comparison which clouds the
evaluation of the pure oxygen process.
Furthermore, in making the comparisons, nothing is said about operation and maintenance, so that
the indicated savings in capital cost may well be outweighed by higher operating costs. The major cost
involved in producing oxygen, and perhaps in applying it in this proprietary method, is for power.
Also, power is a significant cost factor in the production of ozone. Evaluations based on capital
investment alone are quite misleading.
Conclusion
The writer hopes that the device upon which this paper is based is a valuable addition to the
armamentarium available for wastewater treatment. Perhaps the full-scale treatment units that were
under consideration at the time the paper was written will provide a sound basis for evaluation and
comparison of this process with conventional practice and with other new pure oxygen technology.
REFERENCES
ALBERTSSON, J.G., et al, McWHIRTER, J.R., ROBERTON, E.K., VAHLDIECK, N.P., (1970)
"Investigation of the Use of High Purity Oxygen Aeration in the Conventional Activated Sludge
Process," Water Pollution Control Research Series, 17050 DNW 05/70 Advanced Waste Treatment
Research Laboratory, Cincinnati, Ohio.
BUDD, W.E. and LAMBETH, G.F. (1957) "High-Purity Oxygen in Biological Sewage Treatment,"
Sewage and Industrial Wastes, Vol. 29, No. 3, 237.
COHEN, D.B. (1971) "A Low Cost Open Tank Pure Oxygen System for High Rate Total Oxidation,"
Metrolopitan Denver Sewage Disposal District No. 1, prepared for presentation at the International
Waster Pollution Research Association Conference in Jerusalem, 1972.
OKUN, D.A. (1948) "Pure Oxygen and Bioprecipitation Process may Reduce Sewage Treatment
Costs," Civil Engineering, Vol. 18, 288.
OKUN, D.A. (1949) "Systems of Bio-precipitation of Organic Matter from Sewage," Sewage Works
Journal, Vol. 21, No. 5. 763.
W.F. Garber, USA
The following points need consideration. The biological culture established by pure oxygen is
temperature sensitive and almost complete failure may occur at winter temperatures. This culture is so
specialized that loss of pure oxygen feed for a little as 1-4 hours may result in complete process