Discussion by F. Denis,
Paris
It is of interest to study the costs of treatment and sometimes the costs of non-treatment, i.e. the
charge on industrial processes to save having to instal treatment plant. One never knows the cost until
after construction or even after the elapse of some time and it is known that some new processes fail
to come up to expectations. It is necessary to be cautious in making estimates of the cost of untried
processes.
With regard to the two incineration plants mentioned in the paper, what were the costs and figures
and the actual period of their operation?
In order to make comparisons a certain number of parameters have to be varied separately. Because
there are so many variables there is a risk of simplifying the problems. The author has eliminated the
cost of personnel. Is it not true that there is a difference in the number of personnel and their
qualifications required for the processes, resulting in a difference in costs?
With regard to the sludge parameter is the author convinced that the quality and quantity of the
sludges in the two systems were really the same?
C.F. Seyfried, Germany.
The author has not given the basis of the method he has used for the comparison of cost.
The specific cost equation for an activated sludge plant of the same size can vary from 1 to 3
according to construction costs quite apart from other local considerations.
The author's curves of cost comparison cannot be used arbitrarily without knowing the actual basis
of costs and therefore his comparisons without the basis of costs have little meaning.
Replies to Mr. F. Denis and Mr. C.F. Seyfried.
It is undoubtedly correct that, in addition to capital expenditure and power cost, the total costs
will be affected by personnel and sludge-treatment costs. Sickert
1 expounded the relationship of
operating costs to capital expenditure and the break-down of operating costs. As regards the differing
quantities and qualities of excess sludge from activated-sludge and trickling-filter plants, reference
should be made to Bruce and Boon.
2
It would have been impossible and, indeed, was not intended to evolve a model covering every
eventuality nor, for that matter, to produce a standard formulae for the treatment of industrial
effluents or municipal sewage. The aim was to show that, in the case of a specific waste water whose
kinetic degradation parameters were defined in fig. 1, there'are several possible solutions to the
problem and that the total cost curve passes through a minimum.
On the basis of the major parameters, i.e. degree of purification, plant capacity, waste water
concentration, it was demonstrated that there will always be a cost minimum in relation to capital
expenditure and energy costs. Although it is true to say that personnel and sludge-treatment costs will
shift the point of minimum, the basic fact to be demonstrated does not alter. Moreover, the qualification of personnel and, consequently, the change in costs are surely of minor importance, at least
where industrial plants are concerned.
The processes mentioned, i.e. activated sludge, trickling filters, incineration, have now been
employed for industrial waste water treatment for a number of years. The incineration plants mentioned were put into use 5 years ago and are still operating. In the meantime, numerous other incineration
plants for concentrated waste have been installed both in Germany and elsewhere.
The same applies to plastic trickling filters which are commonly used in UK, USA and, more
recently, in Germany. Even though the initial expectations are too high and certain disappointments
are unavoidable, as is frequently the case with new processes, the treatment of concentrated waste
water using this process has proved to have a number of distinct advantages.
The capital expenditure shown for aeration basins refers to concrete types. A close scrutiny of fig.
2 will reveal that the basin geometry is indicated for various sizes. The stepwise increase of specific
trickling filter costs (fig. 3) is due to the fact that intermediate platforms are required whenever a
height of 7 m or 14 m, respectively, is exceeded. Both graphs are based on the same factors and
should, therefore, be regarded in relation to each other.
We feel that there would be no point in specifying absolute costs in this connection, since these are
affected by local conditions to a much greater degree than standardized costs.
REFERENCES
1. SICKERT E., 6th Intern. Conf. Water Poll. Res. Jerusalem 1972, B7 - 13.
2. BRUCE, A.M., BOON, A.G., Public Works and Municipal Services Congress 1970.
547
Paris
It is of interest to study the costs of treatment and sometimes the costs of non-treatment, i.e. the
charge on industrial processes to save having to instal treatment plant. One never knows the cost until
after construction or even after the elapse of some time and it is known that some new processes fail
to come up to expectations. It is necessary to be cautious in making estimates of the cost of untried
processes.
With regard to the two incineration plants mentioned in the paper, what were the costs and figures
and the actual period of their operation?
In order to make comparisons a certain number of parameters have to be varied separately. Because
there are so many variables there is a risk of simplifying the problems. The author has eliminated the
cost of personnel. Is it not true that there is a difference in the number of personnel and their
qualifications required for the processes, resulting in a difference in costs?
With regard to the sludge parameter is the author convinced that the quality and quantity of the
sludges in the two systems were really the same?
C.F. Seyfried, Germany.
The author has not given the basis of the method he has used for the comparison of cost.
The specific cost equation for an activated sludge plant of the same size can vary from 1 to 3
according to construction costs quite apart from other local considerations.
The author's curves of cost comparison cannot be used arbitrarily without knowing the actual basis
of costs and therefore his comparisons without the basis of costs have little meaning.
Replies to Mr. F. Denis and Mr. C.F. Seyfried.
It is undoubtedly correct that, in addition to capital expenditure and power cost, the total costs
will be affected by personnel and sludge-treatment costs. Sickert
1 expounded the relationship of
operating costs to capital expenditure and the break-down of operating costs. As regards the differing
quantities and qualities of excess sludge from activated-sludge and trickling-filter plants, reference
should be made to Bruce and Boon.
2
It would have been impossible and, indeed, was not intended to evolve a model covering every
eventuality nor, for that matter, to produce a standard formulae for the treatment of industrial
effluents or municipal sewage. The aim was to show that, in the case of a specific waste water whose
kinetic degradation parameters were defined in fig. 1, there'are several possible solutions to the
problem and that the total cost curve passes through a minimum.
On the basis of the major parameters, i.e. degree of purification, plant capacity, waste water
concentration, it was demonstrated that there will always be a cost minimum in relation to capital
expenditure and energy costs. Although it is true to say that personnel and sludge-treatment costs will
shift the point of minimum, the basic fact to be demonstrated does not alter. Moreover, the qualification of personnel and, consequently, the change in costs are surely of minor importance, at least
where industrial plants are concerned.
The processes mentioned, i.e. activated sludge, trickling filters, incineration, have now been
employed for industrial waste water treatment for a number of years. The incineration plants mentioned were put into use 5 years ago and are still operating. In the meantime, numerous other incineration
plants for concentrated waste have been installed both in Germany and elsewhere.
The same applies to plastic trickling filters which are commonly used in UK, USA and, more
recently, in Germany. Even though the initial expectations are too high and certain disappointments
are unavoidable, as is frequently the case with new processes, the treatment of concentrated waste
water using this process has proved to have a number of distinct advantages.
The capital expenditure shown for aeration basins refers to concrete types. A close scrutiny of fig.
2 will reveal that the basin geometry is indicated for various sizes. The stepwise increase of specific
trickling filter costs (fig. 3) is due to the fact that intermediate platforms are required whenever a
height of 7 m or 14 m, respectively, is exceeded. Both graphs are based on the same factors and
should, therefore, be regarded in relation to each other.
We feel that there would be no point in specifying absolute costs in this connection, since these are
affected by local conditions to a much greater degree than standardized costs.
REFERENCES
1. SICKERT E., 6th Intern. Conf. Water Poll. Res. Jerusalem 1972, B7 - 13.
2. BRUCE, A.M., BOON, A.G., Public Works and Municipal Services Congress 1970.
547