Discussion by Ralph Porges
Increasing pollution loads has focused attention on the need to achieve effective wastewater
treatment at minimum costs. One consideration is the large regional treatment facility to take advantage of economies of scale, dilution and equalization of trade wastes and reduced surveillance
efforts by the regulating agency. However, the acceptance of industrial wastes by the central facility
introduced certain problems of volume and strength control and treatability.
Farkas in his paper points out sudden changes in waste flows and concentrations, spills and slugs,
overloading and possibly toxicity may bring about effluent quantity changes in the activated sludge
process. He has presented a mathematical approach defining treatability, quantifying the effect of
mixed wastes on the biological system and a method of predicting the effects of the addition of new
industrial wastes to existing plants. This is a real step forward in assuring maximum efficiencies from
regional treatment plants.
There is need to consider the practical aspects as a prelude to the mathematical applications. It is
virtually axiomatic that toxic substances in minute qualities may not be poisonous to a biological
system and may even act as a stimulant. Of course, large amounts, particularly as a slug, could well be
detrimental. Farkas illustrated this in his discussions on the effect of formaldehyde on sludge
respiration.
A unique characteristic of activated sludge is its ability to become acclimatized to certain toxic
wastes thus permitting treatment of larger doses. This was shown by Farkas in Table 2 of his report
where five times as much phenol was handled by an adapted sludge. Projecting treatability of new
wastes to an existing system will require due care to develop an acclimatized sludge so as not to
penalize unduly new contributors to a system.
Overloading of a biological system will bring about poorer effluent quality. Farkas in Table 2 showed
that rendering wastes and blood was treatable but that significant amounts of blood caused overloading and septic conditions. This may be anticipated as blood has been shown to have a BOD5 of
92,000 mg/1.
1 Similar problems may be expected from whole milk that has a BOD 5 of 102,500,
2 and
food wastes as potatoes that has a BOD5 of 84,500.
An engineering and pilot study
4 was undertaken in the Delaware River Basin to develop feasibility
of a regional system and to confirm treatability by activated sludge. The pilot plant was upset by
heavy slugs of toxic wastes similar to that reported by Farkas. To minimize overall treatment costs and
to assure effective treatment at all times, it was established that discharges from industry must reach
the interceptor in a fairly constant condition without appreciable toxicity; each industry must have a
holding tank or comparable device or procedure such that the flow will not vary more than 10 percent
of the average that will be discharged. Significant variations will necessitate an added charge to offset
increased capacity costs.
Increasing regionalization in the Delaware River Basin, supported by experiences with the pilot
plant study, has led to consideration of pre-treatment guidelines directed primarily to industry discharging to municipal or regional systems.
5 The requirements essentially considered two major
aspects: those necessary to protect the collection sewers and wastewater treatment system and those
necessary to permit the treatment system to meet effluent quality discharge requirements and
receiving water quality objectives.
The following set forth the principal items contained in these guidelines:
1. Industries shall have a wastewater meter and composite sampling station of acceptable design to
facilitate the continuous monitoring of their wastewater flow characteristics.
2. Waste particles greater than one-half inch in any dimension are prohibited.
3. Solids from food or other processing should be reclaimed and prevented from reaching sewers by
proper screening; comminution equipment for screening and solids control is required where
necessary.
4. No discharge of any of the following described kinds of wastes shall be permitted into the sewers
or treatment plant.
a. Wastewater containing free floating oil, grease, paints, or fat of such character or quantity that
other than routine attention or expense is required to handle such materials. Normally, 50 mg/1
(as determined by the Standard Method of Analysis) shall be the maximum oil and grease
content of a particular wastewater discharged to the sewerage system.
b. Wastewater possessing a temperature higher than 150 degrees Fahrenheit.
c. Wastewater containing gasoline, benzene, naptha, fuel oil, any other flammable or explosive
material or volatile substances that create environmental hazards or nuisances.
d. Wastewater containing inert materials as sand, grit, ashes, cinders, stone dust, mud, wood, glass
plastics, or tar or viscous substance which could cause operational difficulties or abnormal wear
and tear to the system.
e. Wastewater containing substances as paunch manure, offal, blood, feathers, etc.
f. Wastewater having a pH lower than 6.0 or greater than 9.0.
h. Wastewater containing toxic or radioactive substances which would adversely affect the treatment plant processes or which may affect effluent quality requirements or stream quality
565
Increasing pollution loads has focused attention on the need to achieve effective wastewater
treatment at minimum costs. One consideration is the large regional treatment facility to take advantage of economies of scale, dilution and equalization of trade wastes and reduced surveillance
efforts by the regulating agency. However, the acceptance of industrial wastes by the central facility
introduced certain problems of volume and strength control and treatability.
Farkas in his paper points out sudden changes in waste flows and concentrations, spills and slugs,
overloading and possibly toxicity may bring about effluent quantity changes in the activated sludge
process. He has presented a mathematical approach defining treatability, quantifying the effect of
mixed wastes on the biological system and a method of predicting the effects of the addition of new
industrial wastes to existing plants. This is a real step forward in assuring maximum efficiencies from
regional treatment plants.
There is need to consider the practical aspects as a prelude to the mathematical applications. It is
virtually axiomatic that toxic substances in minute qualities may not be poisonous to a biological
system and may even act as a stimulant. Of course, large amounts, particularly as a slug, could well be
detrimental. Farkas illustrated this in his discussions on the effect of formaldehyde on sludge
respiration.
A unique characteristic of activated sludge is its ability to become acclimatized to certain toxic
wastes thus permitting treatment of larger doses. This was shown by Farkas in Table 2 of his report
where five times as much phenol was handled by an adapted sludge. Projecting treatability of new
wastes to an existing system will require due care to develop an acclimatized sludge so as not to
penalize unduly new contributors to a system.
Overloading of a biological system will bring about poorer effluent quality. Farkas in Table 2 showed
that rendering wastes and blood was treatable but that significant amounts of blood caused overloading and septic conditions. This may be anticipated as blood has been shown to have a BOD5 of
92,000 mg/1.
1 Similar problems may be expected from whole milk that has a BOD 5 of 102,500,
2 and
food wastes as potatoes that has a BOD5 of 84,500.
An engineering and pilot study
4 was undertaken in the Delaware River Basin to develop feasibility
of a regional system and to confirm treatability by activated sludge. The pilot plant was upset by
heavy slugs of toxic wastes similar to that reported by Farkas. To minimize overall treatment costs and
to assure effective treatment at all times, it was established that discharges from industry must reach
the interceptor in a fairly constant condition without appreciable toxicity; each industry must have a
holding tank or comparable device or procedure such that the flow will not vary more than 10 percent
of the average that will be discharged. Significant variations will necessitate an added charge to offset
increased capacity costs.
Increasing regionalization in the Delaware River Basin, supported by experiences with the pilot
plant study, has led to consideration of pre-treatment guidelines directed primarily to industry discharging to municipal or regional systems.
5 The requirements essentially considered two major
aspects: those necessary to protect the collection sewers and wastewater treatment system and those
necessary to permit the treatment system to meet effluent quality discharge requirements and
receiving water quality objectives.
The following set forth the principal items contained in these guidelines:
1. Industries shall have a wastewater meter and composite sampling station of acceptable design to
facilitate the continuous monitoring of their wastewater flow characteristics.
2. Waste particles greater than one-half inch in any dimension are prohibited.
3. Solids from food or other processing should be reclaimed and prevented from reaching sewers by
proper screening; comminution equipment for screening and solids control is required where
necessary.
4. No discharge of any of the following described kinds of wastes shall be permitted into the sewers
or treatment plant.
a. Wastewater containing free floating oil, grease, paints, or fat of such character or quantity that
other than routine attention or expense is required to handle such materials. Normally, 50 mg/1
(as determined by the Standard Method of Analysis) shall be the maximum oil and grease
content of a particular wastewater discharged to the sewerage system.
b. Wastewater possessing a temperature higher than 150 degrees Fahrenheit.
c. Wastewater containing gasoline, benzene, naptha, fuel oil, any other flammable or explosive
material or volatile substances that create environmental hazards or nuisances.
d. Wastewater containing inert materials as sand, grit, ashes, cinders, stone dust, mud, wood, glass
plastics, or tar or viscous substance which could cause operational difficulties or abnormal wear
and tear to the system.
e. Wastewater containing substances as paunch manure, offal, blood, feathers, etc.
f. Wastewater having a pH lower than 6.0 or greater than 9.0.
h. Wastewater containing toxic or radioactive substances which would adversely affect the treatment plant processes or which may affect effluent quality requirements or stream quality
565