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protect freshwater and saltwater aquatic life/ the recommended 24 hour
average concentration is 620 jjg/1 and 2,000 pg/1, respectively; with
recommended maximum concentrations of 1,400 yg/1 and 4,600 ng/1,
respectively.5
Toluene, a common general organic solvent, appeared in concentrations
varying from trace to more than 100 ppb in raw wastewater. In
secondary treatment waters the highest concentration was 50 ppb.
A study using mice showed that toluene is a central nervous system
depressant that can cause behavioral changes as well as loss of
consciousness and death at high concentrations.10 Human exposure to
toluene for a 2-year period has led to cerebellar disease and impaired
liver function.10 The recommended water quality criterion to protect
freshwater aquatic life is 2,300 H9/1 as a 24 hour average; the
concentration should not exceed 5,200 pg/1 at any time. The 24 hour
average and maximum concentrations to protect saltwater aquatic life
are 100 pg/1 and 230 ng/If respectively.7
Trans - 1,2 - dichloroethylene appeared in raw, primary, and secondary
effluents. The compound is a general organic solvent arid a solvent
for fats and phenol. The EPA recommended water quality criterion to
protect freshwater aquatic life is 620 pg/1 as a 24 hour average and
1,400 yg/1 as a maximum permissible concentration.5
1,1,1 - Trichloroethane was found in raw and primary effluents. Its
primary use is as a solvent and degreasing agent; trichloroethane act*.;
as a solvent carrier for water and stain repellant compounds, it
exhibits strong solvent action on organics, especially oils, greases,
waves, and tars; and it blends with other solvents to reduce their
flammability or provide added solvent properties.
1,1,2 - Trichloroethane, also known as vinyl trichloride, was
identified in the raw wastewater from one tannery. It is also a
general solvent for fats and waxes.
Trichloroethylene, another solvent for fats, oils, waxes and resins,
was identified several times in raw and primary effluents. Studies
indicate that exposure to the compound increases the incidence of
hepatocellular carcinoma in mice.11 The compound also acts as a
central nervous system depressant in humans. Symptoms of
trichloroethylene poisoning include dizziness, headaches, and
respiratory tract irritation. Severe intoxication can be fatal, and
exposure to high levels can lead to cardiac arrhythmia, pulmonary
edema, and renal and hepatic dysfunction.11
Trichlorofluoromethane was detected in a trace amount in the primary
treatment effluent of one tannery. It is used in aerosals, as a
refrigerant, and in air conditioning.
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Trichloromethane, commonly known as chloroform, appeared in the raw,
primary, and secondary effluents of several tanneries. It is a
general solvent, refrigerant, and cleaning agent, and it is registered
for pesticide use on cattle. Lab tests show chloroform to be toxic to
organisms at various levels of the food chain; in higher organisms it
exhibits both temporary and lasting effects. Several studies indicate
that chloroform is carcinogenic to rats and mice.12 Human exposure to
chloroform can lead to liver damage, hepatic and renal damage, and
depression of the central nervous system.12
The recommended 24 hour average and maximum concentrations to protect
freshwater aquatic life from the toxic effect of chloroform are 500
pg/1 and 1,200 pg/1, respectively. The recommended water quality
criterion to protect saltwater aquatic life is 620 »g/l as a 24 hour
average, with a maximum concentration of 1,400 pg/1. For the maximum
protection of human health from the potential carcinogenic effects of
exposure to chloroform, the recommended ambient water concentration is
zero.5
Basic/Neutral Fraction- Among the basic/neutral organic priority
pollutants, dichlorobenzenes, naphthalene, and the polynuclear
aromatics phenanthrene/anthracene were the most often identified.
Phenanthrene and anthracene co-elute from gas chromatograh (GC)
analytical equipment and exhibit very similar mass spectra so that
their identifications represent either 1 compound or some combination
of both compounds. The basic/neutral compounds typically are used in
the manufacture of various dyes and in pesticide formulations.
1,2 - Dichlorobenzene and its isomer 1,4- dichlorobenzene were among
the most common of the basic neutral compounds found in tanning
effluents. Tanneries use 1,2-Dichlorobenzene in a number of
processes. It is a solvent for waxes and gums, a degreasing agent for
leather, an insecticide, an intermediate in dye manufacture, and a
mask for various odors. 1,2- and 1,4-dichlorobenzene were identified
as major contaminant chemicals in a hide curing product used by
tanneries and their hide suppliers. 1,4-Dichlorobenzene is used in
the manufacture of pesticides, as an insecticidal fumigant in
controlling parasites, and in mothproofing wool on sheepskins.
Unlike the other dichlorobenzenes, 1,3-dichlorobenzene was detected
only twice in raw wastewaters.
Bioconcentration studies of the dichlorobenzenes in the bluegill
indicate that 1,3-dichlorobenzene concentrates by a factor of 66
while 1,4-dichlorobenzene concentrates by a factor of 60.13 '
For 1,2-dichlorobenzene, the criterion to protect freshwater aquatic
life is 44 pg/1 as a 24 hour average, and the concentration should not
exceed 99 Mg/l at any time. For 1,3-dichlorobenzene, the recommended
24 hour average and maximum concentrations are 310 pg/1 and 700 ug/1
respectively. The criterion to protect freshwater aquatic life from
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the toxic effects of 1 ,4-dichlorobenzene are 190 pg/1 as a 24 hour
average concentration, with a maximum concentration of 440
The criterion to protect saltwater aquatic life from the toxic effects
of 1,2-dichlorobenzene is 15 pg/1 as a 24 hour average concentration;
the concentration should not exceed 34 pg/1 at any time. For 1,3-
dichlorobenzene, the recommended criterion is 22 /jg/1 as a 24 hour
average and 49 pg/1 as a maximum permissible concentration. For 1 ,4-
dichlorobenzene, the recommended 24 hour average and maximum
concentrations are 15 pg/1 and 34 pg/1, respectively.5
For the protection of human health from the toxic properties of all
isomers of dichlorobenzene combined ingested through water and
contaminated aquatic organisms, the ambient water criterion is
determined to be 230 pg/1 total dichlorobenzene. 5
1,2,4 - Trichlorobenzene appeared in the raw wastewater of one plant
in a concentration of 1.8 ppb. It is commonly used as a dye carrier,
a heat transfer fluid, an intermediate in herbicide manufacture, and
as an insecticide against termites. The compound resists physical and
chemical degradation and accumlates in fatty tissues.
Hexachlorobenzene was identified in the secondary effluent of one
plant. The compound is used as a fungicide and in dye manufacturing.
Extremely resistant to photochemical degradation, it also degrades
slowly in the soil, Hexachlorobenzene bioaccumulates in fatty tissue.
N - nitrosodiphenylamine was the only nitrosamine identified in
tannery effluents. As a class, nitrosamines often are carcinogenic;
they have produced cancer in mammals via all routes of exposure and in
essentially all vital organs. The nature of toxic response is related
to the chemical characteristics of the particular compound
administered. The site of activity depends upon the compound, age and
species of animal, dosage level, route of administration, and rate of
exposure.14 Toxicological evidence on N-nitrosodiphenylamine is such
that the compound is considered a potential human carcinogen. For
this reason, to insure the maximum protection of human health from the
potential carcinogenic effects of exposure to the compound, the
recommended ambient water concentration is zero. 5 Nitrosamines persist
in soil, sewage, and water. They are characteristically
photosensitive; exposure of ultraviolet (UV) light split the nitroso
group with release of nitrite and secondary amines. They are
characteristically stable under alkaline conditions; in acids they
undergo photodecomposition. N-nitrosodiphenylamine is used in the
manufacture of insecticides, rubber, dyes, and solvents.
1,2-Diphenylhydrazine, also known as hydrazobenzene, was detected in
the primary and secondary effluent of one tannery. It did not appear
in the plant's raw wastewater. The compound is primarily a special
reagent in chemical laboratory operations. There is little
information available regarding the fate and effects of 1,2-
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diphenylhydrazine in the environment, but in one study, 22 percent of
rats injected with the compound developed tumors.is For tne maximum
protection of human health from the potential carcinogenic effects of
exposure to 1,2-diphenylhydrazine, the ambient water concentration
should equal zero. The recommended criterion to protect freshwater
aquatic life is 17 pg/1 as a 24 hour average concentration and 38 uq/1
as a maximum concentration.7
Nitrobenzene was detected in the raw and primary effluent of one
tannery. The concentration decreased from 425 ppb in raw wastewater
to 29 ppb in the primary effluent. Nitrobenzene is used extensively
for the preparation of dye intermediates and as a solvent. The
recommended 24 hour average and maximum concentrations to protect
freshwater aquatic life are 480 ug/1 and 1,100 ug/1, respectively. To
protect saltwater aquatic life, the 24 hour average criterion is 53
ug/1; the maximum concentration is 120 ug/1. For the prevention of
adverse effects due to organoleptic properties of nitrobenzene in
water, the criterion is 30 ug/1.
Benzidine (4,4-diamino-biphenyl), like other aromatic amines, results
from the reduction of azo dyes in wastes by hydrogen sulfide or sulfur
dioxide already present in water. It is also used directly in the dye
industry. Benzidine undergoes relatively rapid decay in lakewater. A
suspected human carcinogen, exposure to benzidine has been linked to
an increased incidence of bladder tumors.*•
3,3»-Dichlorobenzidine (3,3«-dichloro-4,4«-diaminobiphenyl) , an inter-
mediate in the manufacture of azo dyes, was detected in the secondary
effluent of one tannery The compound has been demonstrated to be
carcinogenic in non-human mammals under controlled test conditions
Exposure can lead to the development of various sarcomas and
adenocarcinomas.i7 For the optimum protection of human health from the
potential carcinogenic effects of exposure to dichlorobenzidine, the
ambient water concentration should be zero.7
isophorone was found in the secondary effluents of two tanneries.
Isophorone acts as a solvent or cosolvent for finishes, lacquers,
resins, pesticides, herbicides, fats, oils, and gums. The recommended
24 hour average and maximum water quality criterion for the protection
of freshwater aquatic life is 2,100 ug/1 and 4,700 ug/1, respectively.
For the protection of saltwater aquatic life the 24 hour average
concentration is 97 ug/1 and the maximum concentration is 220 uq/1
To protect human health from the toxic properties of isophorone
ingested through water, the recommended criterion is 460 ug/1 7
Studies indicate that human exposure to concentrations of 10 to 25 ppm
for a 15-minute period results in eye, nose, and throat irritations.i«
Several phthalate esters, including dimethyl phthalate, diethyl
phthalate, di-n-butyl phthalate, butyl benzyl phthalate, and bis-(2-
ethylhexyl) phthalate, were identified in tannery wastewater at
concentrations up to 200 ppb. Phthalate esters are used extensively
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as plasticizers and, to a lesser extent, in pesticides and lubricants
in vacuum pumps.
Phthalate esters can harm aquatic and terrestrial organisms at low
concentrations. The compounds exhibit teratogenic and mutagenic
effects under certain laboratory conditions. Of the fish species
tested, the rainbow trout was the least sensitive and the bluegill the
most sensitive to di-n-butyl phthalate. A cray fish species tested
was the least sensitive and a freshwater zooplankton the most
sensitive of all species tested.4
High levels of phthalate concentration from water and reproductive
impairment in certain species are suggestive of potential
environmental damage. The presence of these compounds in water
affects the growth and reproduction essential for maintenance of
animal populations.
As a means of protecting human health from the toxic properties of
phthalene esters ingested through water and contaminated aquatic
organisms, the recommended ambient water criteria for dimethyl
phthalate and diethyl phthalate are 160 M9/1 and 60 pg/1,
respectively.
Among the basic/neutral compounds identified in various tannery
effluents were ten polynuclear aromatic hydrocarbons (PNA's).
Naphthalene, phenanthrene, and anthracene were among the most frequent
basic/neutral compounds identified and were detected at levels ranging
from trace to more than 750 ppb. The remaining polynuclear aromatics
acenaphthene, acenaphthylene, 2-chloronaphthalene, fluorene,
fluoranthene, chrysene, and pyrene - were present frequently and
usually at low concentrations. Polynuclear aromatics generally are
used as intermediates in dye manufacture and in pesticides.
On the basis of present studies, the evidence is not clear whether
individual polynuclear aromatics produce toxicity or carcinogeriicity
in man; however, coal tars, pitch, and other materials known to be
carcinogenic to man contain many of the PNA's that produce cancer in
animals.
The effects of naphthalene poisoning on humans have been studied.
Naphthalene poisoning can cause convulsions and hematologic changes.19
Reports also indicate that workers exposed to naphthalene for
extensive periods of time are likely to develop malignant tumors.19
Naphthalene bioconcentrates in aquatic organisms and reduces or
interferes with microbial growth. It also reduces photosynthetic
rates in algae. Naphthalene accumulates in sediments by a factor as
great as up to two in the concentration in overlying water and can be
degraded by microorganisms to 1,2-dehydro-l,2-dihydroxynaphthalene and
ultimately to carbon dioxide and water.
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A combination of fluoranthene and benz(a) pyrene produced tumors in 98
percent of the mice tested, which was more than double the number of
tumors produced in the benz (a) pyrene control animals.20
For fluoranthene the water quality criterion to protect freshwater
aquatic life is 250 »q/l as a 24 hour average, and the concentration
should not exceed 560 jjg/1 at any time. The 24 hour average and
maximum concentrations to protect saltwater aquatic life are 0.30 pg/1
and 0.69 pg/1, respectively. For the protection of human health from
the toxic properties of fluoranthene exposure through water, the
ambient water quality criterion should equal 200 Mg/1-5 For
acenaphthene the criterion to protect freshwater aquatic life is 110
pg/1 and 240 pg/1 as 24 hour average and maximum concentrations,
respectively. For saltwater aquatic life the 24 hour average and
maximum concentrations are 7.5 pg/1 and 17 pg/1, respectively. The
ambient water criterion for the protection of human health is 20
pg/1.7 For the protection of human health from the toxic properties of
naphthalene ingested through contaminated aquatic organisms and water,
the recommended ambient water criterion is 143 pg/1.7
Acidic Fraction. Among the acidic fraction of the organic toxic
pollutants, phenols, defined as hydroxy derivatives of benzene and its
condensed nuclei, and a variety of substituted phenols, including
2,4,6-trichlorophenol and pentachlorophenol, were identified most
frequently, at levels often exceeding 1 ppm in raw wastewaters. These
compounds are typically used to extend raw material storage life and
in bactericide, fungicide, and insecticide formulations. 2,4,5-
trichlorophenol is a known major constituent of a biocide used by
leather tanners. Other sources which contribute to the significant
levels of phenols in raw wastewaters include synthetic and natural
vegetable tannins and dye carriers. Chlorination of such waters can
produce odoriferous and objectionable tasting chlorophenols which may
include o-chlorophenol, p-chlorophenol, 2,6-dichlorophenol, and 2,4-
dichlorophenol.
Although described in the technical literature simply as phenols, the
phenol waste category can include a wide range of similar chemical
compounds. In terms of pollution control, reported concentrations of
phenols are the result of a standard methodology which measures a
general group of similar compounds rather than specific identification
of the single compound, phenol (hydroxybenzene).
Phenol was identified 33 times in tannery effluents, more than any
other acidic organic pollutant. Phenolic compounds can affect
freshwater fishes adversely by direct toxicity to fish and fish-food
organisms, by lowering the amount of available oxygen because of the
high oxygen demand of compounds, and by tainting fish flesh. The
toxicity of phenol towards fish increases as the dissolved oxygen
level is diminished, as the temperature is raised, and as the hardness
is lessened. Phenol appears to act as a nerve poison, causing too
much blood to get to the gills and to the heart cavity.21
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Mixed phenolic substances are especially troublesome in imparting
taste to fish flesh. Monochlorophenols produce a bad taste in fish
far below lethal or toxic doses. Threshold concentrations for taste
or odor in chlorinated water supplies have been reported as low as
0.0003 mg/1.2i
The human ingestion of a concentrated phenol solution results in
severe pain, renal irritation, shock, and possibly death.
Various environmental conditions will increase the toxicity of phenol.
Lower dissolved oxygen concentrations, increased salinity, and
increased temperature all enhance the toxicity of phenol. The
recommended water quality criterion to protect freshwater aquatic life
is 600 pg/1 as a 24 hour average, and the concentration should not
exceed 3,400 M9/1 at any time.7
Although 2, 4-dichlorophenol (DCP) appears to be less toxic than the
higher chlorinated phenols, it has demonstrated toxicity to certain
microorganisms, plants, and aquatic speaies and has demonstrated
teratogenicity in nonhuman mammals.22 Fourteen percent of crayfish
exposed to 1 mg/1 DCP over a 10-day period died. When the
concentration was increased to 5 mg/1 the mortality rate increased to
34 percent within 24 hours and 100% within 1 week. At 10 mg/1 the
mortality rate was 78 percent within 24 hours and 100 percent within
48 hours.22 The compound has also been shown to have tumor producing
action in mice.22 The EPA recommended water quality criterion to
protect freshwater aquatic life from tainting is 0.4 jjg/1 as a 24 hour
average concentration; the concentration should not exceed 110 M9/1 at
any time. To prevent adverse effects to human health due to
organoleptic properties of 2.4 dichlorophenol in water, the
recommended criterion is 0.5 pg/1.5
2,4,6-trichlorophenol, like phenol, is an intermediate in the
synthesis of dyes. This compound can also be an impurity of 2,4,5
trichlorophenol which is a registered biocide used extensively in this
industry. It was found in high concentrations in raw wastewaters, and
in some cases high concentrations in final effluents. In a study of
genetic activity using an in vitro mammalian spot test with mice,
2,4,6-trichlorophenol exhibited definite, although weak, mutagenic
activity. 23 The recommended 24 hour average and maximum concentrations
to protect freshwater aquatic life are 52 jjg/1 and 150 M9/1*
respectively. To protect human health from adverse effects of 2,4,6-
trichlorophenol, the recommended criterion is 100 jjg/1.?
2, 4-dimethyl phenol has also been shown to have a tumor promoting
action in mice.2* For 2, 4-dimethyl phenol, the recommended criterion
to protect freshwater aquatic life is 38 pg/1 as a 24 hour average the
concentration should never exceed 86
Pentachlorophenol is a registered and widely used biocide in the
leather industry. It was found in high concentrations in raw
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wastewaters and in final effluents. Several bioassays have shown that
pentachlorophenol is lethal to various species of aquatic life at a
concentration of approximately 200 pg/1. The lethal concentration for
species tested ranged from 195 pg/1 for the brown shrimp to 220 pg/1
for the gold fish.25 The recommended 24 hour average and maximum
concentrations to protect freshwater aquatic life are 6.2 jjg/1 and 14
Mg/1, respectively. To protect saltwater aquatic life the 24 hour
average concentration is recommended to not exceed 3.7 jug/1; at no
time should the pentachlorophenol concentration exceed 8.5 pg/1.5
A study of genetic activity demonstrated that pentachlorophenol
exhibited weak but definite mutagenic activity.25 In nonhuman mammals
the sublethal effects of pentachlorophenol poisoning include
pathological and histopathological changes in the kidneys, liver,
spleen, lungs, and brain.25 In humans, the results of
pentachlorophenol poisoning can range from elevated blood pressure and
rapid respiration to coma and death.25 For the protection of human
health the ambient water concentration should be no greater than 140
Mg/l.s
Pentachlorophenol is highly persistent in soils. Reports have
indicated that the compound can persist in moist soil for at least a
12-month period.25
Inorganic Priority Pollutants
Several of the inorganic toxic pollutants were found in tannery
wastewaters at levels of 1 ppb or more. Prominent among these is
chromium which is used in the tanning process. The other inorganic
toxic pollutants found in tannery wastewater and discussed herein are
copper, nickel, lead, zinc, and cyanide.
Total Chromium (CrT)
Chromium compounds are used extensively throughout the leather tanning
industry, and chromium is the most prevalent toxic pollutant found in
wastewaters in this industry. Almost all compounds are used in the
trivalent form; use of hexavalent chromium in the "two-bath" tanning
process is nearly obsolete. The prevalent chromium form found in the
wastewaters is trivalent chromium, although hexavalent compounds may
also occur in waste streams primarily from spillage. It is not
possible, however, to determine the distribution accurately, for
current analytical procedures for chromium cannot always differentiate
between the valence states.
Chromium in its various valence states is hazardous to man. It can
produce lung tumors when inhaled and induces skin sensitizations.
Large doses of chromates have corrosive effects on the intestinal
tract and can cause inflammation of the kidneys. Levels of chromate
ions that have no effect on man appear to be so low as to prohibit
determination to date. The toxicity of chromium salts to fish and
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other aquatic life varies widely with the species, temperature, pH,
valence of the chromium, and synergistic or antagonistic effects,
especially those of hard water. Studies show that trivalent chromium
is more toxic to fish of some types than is hexavalent chromium.
Other studies show opposite effects. Fish food organisms and other
lower forms of aquatic life are extremely sensitive to chromium; it
also inhibits the growth of algae. Therefore, both hexavalent and
trivalent chromium must be considered potentially harmful to
particular fish or organisms.
Fish appear to be relatively tolerant of chromium, but some aquatic
invertebrates are quite sensitive. Toxicity varies with species,
chromium oxidation state, and pH.
Chromium concentration factors in marine organisms have been reported
to be 1,600 in benthic algae, 2,300 in phytoplankton, 1,900 in
zooplankton, and 440 in molluscan soft parts.26
The chemistry of chromium is very complex, especially in untreated raw
wastewaters where interferences from complexing mechanisms, such as
chelation by organic matter and dissolution due to presence of
carbonates, can cause deviation from predicted behavior in treatment
systems. Disposal of sludges containing very high trivalent chromium
concentrations can potentially cause problems in uncontrollable
landfills. Incineration, or similar destructive oxidation processes
can produce hexavalent chromium, which in turn is potentially more
toxic than trivalent chromium under certain circumstances. In other
cases where high rates of chrome sludge application are used, distinct
growth inhibition and plant tissue uptake have been noted. Therefore,
the use of agricultural land for tannery or POTW sludge disposal
should not be generally adopted in light of the potential for long-
term accumulation and toxicity in soils and plant tissue.
Copper- Copper oxides and sulfates are used for pesticides,
fungicides, and certain metallized dyes. The toxicity of copper to
aquatic life is dependent on the alkalinity of the water, as the
copper ion is complexed by anions present, which in turn affect
toxicity. At lower alkalinity copper is generally more toxic to
aquatic life. Other factors affecting toxicity include pH, organic
compounds, and the species tested. Relatively high concentrations of
copper may be tolerated by adult fish for short periods of time; the
critical effect of copper appears to be its higher toxicity to young
or juvenile fish.
In most natural fresh waters in the United States, copper
concentrations below 0.025 mg/1 as copper evidently are not rapidly
fatal for most common fish species. In acute tests copper sulfate in
soft water was toxic to rainbow trout at 0.06 mg/1 copper. In very
hard water the toxic concentration was 0.6 mg/1 copper. In general
the salmonids are very sensitive and the sunfishes are less sensitive
to copper.4
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Copper appears in all soils, and its concentration ranges from 10 to
80 ppm. In soils, copper occurs in association with hydrous oxides of
manganese and iron and also as soluble and insoluble complexes with
organic matter. Keeney and Walsh (1975) found that the extractable
copper content of sludge- treated soil decreased with time, which
suggests that a reversion of copper to less soluble forms.27
Copper is essential to the growth of plants, and the normal range of
concentrations in plant tissue is from 5 to 20 ppm. Copper
concentrations in plants normally do not build up to high levels when
toxicity occurs. For example, the concentrations of copper in
snapbean leaves and pods was less than 50 and 20 ppm, respectively,
under conditions of severe copper toxicity. Even under conditions of
copper toxicity, most of the excess copper accumulates in plant
tissues. Copper toxicity may develop in plants from application of
sewage sludge if the concentration of copper in the sludge is
relatively high.
The recommended criterion to protect saltwater aquatic life is 0.79
pg/1 and 18 pg/1 as 24 hour average and maximum concentrations,
respectively. 7
Nickel- Studies of the toxicity of nickel to aquatic life indicate
that tolerances vary widely and are influenced by species, pH
synergistic effects, and other factors.
Available data indicate that: (1) nickel in water is toxic to plant
life at concentrations as low as 100 pg/1; (2) nickel adversely
affects reproduction of a freshwater crustacean at concentrations as
low as 0.095 mg/1; (3) nickel concentrations as low as 0.31 mg/1 can
kill marine clam larvae; and (4) nickel seriously affects reproduction
of freshwater minnow at concentrations as low as 0.73 mg/1 and the
reproduction of Daphnia at 53
In nonhuman mammals nickel acts to inhibit insulin release, depress
growth, and reduce cholesterol. 2 « A high incidence of cancer of the
lung and nose has been reported in humans engaged in the refining of
nickel. 2 s
Lead. Salmonids and freshwater zooplankton are the organisms most
sensitive to lead. 1 mg/1 was lethal for trout, while 0.03 mg/1
impaired re productivity in a zooplankton, both in soft water. The
highest no-effect level on survival, growth, and reproduction was
about 0.012 mg/1. 29 in general, the salmonids are most sensitive to
lead in soft water, but the influence of pH and other factors on the
solubility and form of the lead have a strong effect on the
concentration at which acute toxicities are demonstrated.*
In humans lead poisoning can cause congestion of the lungs, liver,
spleen, and kidneys. 29 Lead has also caused the formation of tumors in
rats and mice. 29
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To protect human health from the toxic properties of lead the
recommended ambient water criterion for lead is 50 pg/1.5
Zinc. Toxic concentrations of zinc compounds cause adverse changes in
the morphology and physiology of fish. Acutely toxic concentrations
induce cellular breakdown of the gills, and possibly the clogging of
the gills with mucous. Chronically toxic concentrations of zinc
compounds, in contrast, cause general enfeeblement and widespread
histological changes to many organs, but not to gills. Growth and
maturation are retarded. In general, salmonids are most sensitive to
elemental zinc in soft water; the rainbow trout is the most sensitive
in hard waters. In tests with several heavy metals, the immature
aquatic insects seem to be less sensitive than many tested fish.
Although available data is sparse on the effects of zinc in the marine
environment, zinc accumulates in some species, and marine animals
contain zinc in the range of 6 to 1,500 mg/kg. Toxicities of zinc in
nutrient solutions have been demonstrated for a number of plants.4
Cyanide. Cyanide is one of the simplest and most readily formed
organic molecules. Cyanide and its compounds are almost universally
present where life and industry are found. Besides its importance in
a number of manufacturing processes, cyanides occur in many plants and
animals as short term metabolic intermediates. Cyanide is found in
certain acid dyes used in the leather industry, such as blue and
green; possibly, it is found also in vegetable tannins.
In addition to the simple hydrocyanic acid (HCN), the alkali metal
salts, such as potassium cyanide (KCN) and sodium cyanide (NaCN), are
commonly occurring forms and sources of cyanide. The latter compounds
dissolved readily in water; HCN formation is pH-dependent. A
significant fraction of the cyanide exists as HCN molecules up to a pH
of approximately 8, and the fraction increases rapidly as the pH of
the solution decreases. When these simple salts dissociate in aqueous
solution, the cyanide ion combines with the hydrogen ion to form
hydrocyanic acid, which is toxic to aquatic life.
The cyanide ion combines with numerous heavy metal ions to form
metallocyanide complexes. The stability of these anions is highly
variable. Those formed with zinc and cadmium are not stable;
dissociation and production of hydrocyanic acid in near neutral or
acidic environments is rapid. In turn, some of the metallocyanide
anions are extremely stable. Cobaltocyanide is difficult to destroy
with highly destructive acid distillation in a laboratory. The iron
cyanides are also very stable but exhibit the phenomenon of
photodecomposition, and in the presence of sunlight the material
dissociates to release the cyanide ion, thus affecting toxicity.
Cyanide toxicity is essentially an inhibition of oxygen metabolism,
i.e., rendering the tissues incapable of exchanging oxygen. The
cyanogen compounds are true noncumulative protoplasmic poisons since
they arrest the activity of all forms of animal life. Cyanide shows a
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very specific type of toxic action. It inhibits the cytochrome
oxidase system which facilitates electron transfer from reduced
metabolites to molecular oxygen. It does this by combining with the
reactive ferric ions of the catalyst molecule.
The persistence of cyanide in water is highly variable. This
variability depends upon the chemical form of cyanide in the water,
the concentration of cyanide, and the nature of other constituents.
Cyanide may be destroyed by strong oxidizing agents such as
permanganates and chlorine. Chlorine is commonly used to oxidize
strong cyanide solutions to produce carbon dioxide and nitrogen; if
the reaction is not carried through to completion, cyanogen chloride
may remain as a residual. This material is also toxic. If the pH of
the receiving waterway is acidic and the stream is well aerated,
gaseous hydrogen cyanide may evolve from the waterway to the
atmosphere. At low concentrations and with acclimated microflora,
cyanide may be decomposed by microorganisms in both anaerobic and
aerobic environments or waste treatment systems.
A review of the pertinent literature concluded that free cyanide
concentrations ranging from 50 to 100 ug/1 as cyanide have proven
eventually fatal to many sensitive fish; levels much above 200 ug/1
probably are rapidly fatal to most fish species. Among the species
studied were brook trout (Salvelinus fontinalis), brown trout (Salmo
trutta), smallmouth bass (Micropterus dolomieu), bluegill (Lepomis
machrochirus), and fathead minnows (Pimephales promelas).
Some information on chronic or sublethal effects of cyanide is also
available. Among the findings were: increased intestinal secretions
in the fish, Cichlasoma bimaculatum. at concentrations as low as 20
ug/1 and reduced swimming capability at concentrations of 40 ug/1.
Exposure to cyanide concentrations as low as 10 ug/1 reduced the
swimming ability or endurance of brook trout, Salvelinus fontinalis.
Growth, or food conversion efficiency of coho salmon, Oncorhynchus
Kisutch.y decreased at hydrogen cyanide concentrations of 20 ug/1.
Small freshwater fish of the family Cichlidae exposed to a cyanide
concentration of 15 ug/1 lost weight more rapidly than the control
fish in water free from cyanide.
To protect freshwater aquatic life the recommended water quality
criterion is 1.4 pg/1 as a 24 hour average concentration; the maximum
concentration should not exceed 38 pg/1 at any time. The criterion to
protect human health from the toxic properties of cyanide ingested
through water and contaminated aquatic organisms is 0.2 mg.CN-/!.?
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
PRODUCTION
is section describes waste treatment technology currently in use and
ailable for use in the leather tanning and finishing industry. Two
neral approaches to pollutant reduction are in-plant process
ntrols and end-of-pipe effluent treatment systems. End-of-pipe
eatment approaches include: (1) preliminary treatment and primary
eatment; (2) secondary treatment; and (3) advanced waste treatment.
e term pretreatment as used in the proposed regulations is defined
include in-plant controls (Level 1), preliminary treatment of
gregated streams (Level 2), and primary treatment of combined
reams by coagulation-sedimentation (Level 3). These technologies
e intended to precede either separate industrial "secondary"
ological treatment by direct dischargers, or discharge to a publicly
ned treatment works (POTW). It is necessary to reduce shock loads,
otect the biological system, remove the suspended solids that resist
eatment, remove heavy metals (including chromium which would render
TW sludges unacceptable for agricultural use), prevent damage to
wer lines, and reduce health and life hazards in sewerage
intenance.
econdary" treatment, typically a biological treatment process, is
tended for use in this industry to remove biodegradable organic
terial subsequent to pretreatment as defined above. A major
iduction of BOD5, suspended solids, phenols, some related phenolic
impounds, and certain other toxic organic pollutants is accomplished
L "secondary" treatment, as well as a significant degree of
.trification.
Ivanced waste treatment, typically following primary and secondary
•eatment processes, includes technologies which remove residuals of
ispended solids, heavy metals, and dissolved organic compounds, and
reduce an effluent of high clarity and very low conventional,
mconventional, and toxic pollutant content.
irrent Practices
irrent practices in the tanning industry range from no treatment of
istewater to several types of "secondary" treatment. Because POTWs
rovide secondary treatment, effluent quality requirements for
idirect dischargers to municipal sewer systems are less stringent
lan for tanneries that discharge directly to surface waters. A
irvey of 89 wet-process tanners indicates that 12 percent of the
idirect dischargers have no pretreatment, whereas all direct
Lschargers surveyed have at least primary treatment and some form of
?condary treatment, which may still need upgrading to meet either or
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both BPT and BAT limitations. With increasing numbers of stat<
imposing more stringent water quality limitations in NPDES permits fc
POTW's, there is a trend toward some pretreatment by all tanners.
The information collection forms and questionnaires, site visits, ai
sampling visits of wet processors have provided a profile of currer
control practices in the leather tanning industry. Most tannei
discharge to municipal treatment plants. These indirect discharge!
comprise 170 tannery operations, or about 90 percent of the industry
Of these dischargers, 88 percent provide preliminary treatment, one
fifth of the treatment operations consisting of coarse screening onl}
The remaining 12 percent do not provide preliminary treatment. Nor
of the indirect dischargers provide secondary treatment.
Eighteen plants (about 10 percent of the industry) discharge thej
wastewater directly to surface waters. All 18 provide some type c
secondary treatment, five using activated sludge treatment and th
other 13 using lagoons or other treatment methods.
One plant, now closed, operated a physical-chemical treatment system.
Waste Control and Treatment Considerations
The pollutants found in leather tanning and finishing wastewater
differ little from those in wastewaters of many other industries an
can be treated by conventional methods for suspended solids reductior
oil and grease removal, pH control, and BOD5 reduction. Specifi
constituents peculiar to certain tanning processes, such as the toxi
pollutants chromium and phenol, and the nonconventional pollutant
sulfide, TKN, and ammonia can be removed with available treatmen
methods currently practiced by the industry.
Tannery waste treatment cannot overlook the interrelationship of th
different media (i.e. air, water, and land) for pollutant discharge
for example, coagulation-sedimentation and sludge dewatering produce
waste product for land disposal. If a chromium tanning process i
used, this waste will contain large quantities of trivalent chromium
and care must be exercised in managing the waste disposal to preven
leachate contamination of ground or surface waters. The practice o
chromium reuse or recovery within the plant should reduce the chromiu
content of the sludge.
Tannery wastes can create or contribute to the following problems fo
POTW's and separate industrial wastewater treatment facilities:
1. discharge of significant concentrations and mass
of toxic pollutants:
2. large pieces of scrap hide and leather clogging
or fouling operating equipment;
3. excessive quantities of hair and other small
screenable solids;
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4, highly acidic or alkaline waste streams;
5. wastewater flow surges;
6. excessive loadings of suspended and settleable
solids and BODJ5, consistently or in surges;
7. odors, facilities corrosion, very high dissolved
oxygen demand in biological treatment system aeration
basins, and hazardous gas generation from sulfide
bearing wastes
8. a problem with disposal of sludges containing
chrome; and
9. pass through of ammonia nitrogen.
ich of the problems outlined can be reduced significantly or
Liminated by applying pretreatment technology in leather tanneries.
Lne screening effectively removes hair, fibers, and scrap material
:om wastewater and is available in many different configurations,
Dme of which are particularly effective on tannery type wastes.
greening equipment also must be installed, operated, and maintained
roperly to function well.
iste streams from specific processes in tanneries can be highly
::idic or alkaline. If such streams are discharged without pH
ljustinent or mixing with a different neutralizing stream, the waste
bream may create problems within the sewer or at the treatment plant.
pH control mechanism of holding and mixing various wastes or of
irectly adjusting the pH of the waste is easily implemented as a
retreatment technology.
Low and waste loading surges, which can be particularly disruptive to
iological treatment systems employed by POTWs, can be minimized by
Dualizing the rate of flow or waste loading discharge. If space
imitations at a tannery preclude an equalization tank, discharge
cheduling, as practiced by at least one tannery, can reduce the
agnitude of these surges.
atch basins, wet wells, and other preliminary treatment facilities
hat provide a retention time and space for solids separation from the
aste stream can be very effective if properly designed and
aintained. Such a facility requires regular maintenance in order to
perate consistently and effectively.
he potential problems in disposing of municipal sludge that contains
hromium can be alleviated by chromium removed by tanneries. In this
anner, a smaller quantity of sludge containing a higher concentration
f chrome is more easily disposed of in a controlled environment.
hrome recovery and reuse technology is available and in use by the
ndustry. This substantially reduces the chrome content of the waste
tream and of sludges generated in treatment of these wastes.
n its evaluation of available treatment technologies, EPA has
ttempted to do the following:
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1. Identify methods of substantially improving the currently
treatment l^s.^0™™ °f m°St ^^ wastewate^
2. Present information on recycle, recovery, and/or reuse
r*liShi29i2 • 3S 7iabl?T ?°St effective, established, and
reliable options for pollution control.
3. Describe the performance of in-place preliminary treatment
and secondary treatment technologies on the toxic pollutants
found in tannery wastewaters.
«. Present information on the effectiveness of advanced waste
treatment technologies on pollutants as 1) demonstrated in
use, 2) transferable from a related use or experimental
work, or 3) thought to be effective based on a knowledge of
chemical process technology and of the similarity of
structure. <*emicals of similar molecular size and
This discussion groups the pollution control technologies by the point
?hPaPfl^ati?": in-Plant' Preliminary treatment, and end-of-pipe
The distinction between the first two may blur in some instances- but
the focus of the first is on in-plant waste control , whlrell ' the
second group of technologies typically involves waste treatment and
pollution control preparatory to discharge into a municipal sewer or
into an industrial secondary treatment system. Each treatment
approach is discussed with a description of equipment! examples of
systems currently being used, and reduction levels expected?
IN-PLANT CONTROL TECHNOLOGY - LEVEL _1
Appraisals of plant waste production must first investigate the
??™ aC^ng °yCle f°r any Codifications which can reduce the waste
~SL concentration of waste constituents. Particular emphasis
thf ?otal wfsteCstreamh°S? faCt°rS ^iCh ^ Pr°blems in treatment "I
tne total waste stream, in some instances, reuse or recoverv of
of
can
Process changes and waste stream segregation are two methods of
pollutant reduction and/or control essential to achieving
provides ^useful ^g"1"^ ^ "6 "-3tionnaires from
The following steps can often reduce pollutants and the costs of waste
treatment: waoi_t:
1. process changes;
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2. substitution of process ingredients;
3. water conservation and reuse;
4. repair and replacement of leaky or faulty equipment;
5. installation of automatic monitoring devices to detect
abnormal quantities of selected constituents in waste
effluents;
6. recovery and reuse of process chemicals; and
7. in-plant treatment to remove a specific waste
constituent.
'rocess Changes
'rocess changes have been difficult to make in this industry because
>f the diverse tanning methods employed. While tanning operations
;raditionally employed the batch system, it is possible that more of
:he chemical applications as well as the washing and rinsing could be
landled more efficiently on a counter-current continuous flow basis.
This would achieve maximum utilization of all active ingredients,
.eaving only concentrated wastes of small volumes for treatment and
lisposal. Substitution of effluents from one process for make-up
/ater in another generally is feasible at some points within a
:annery. Before tanneries can make this change however, they must
establish the quantity and pollutant content of water required for
?ach operation.
Substitution of Process Ingredients
Chemical ingredients of low pollution potential for those which are
problem pollutants often can be used to advantage in industrial
processes. Difficulties caused by high concentrations of contaminants
Ln spent tan liquors from vegetable tanning processes have been
Lessened through recovery and reuse of those spent liquors in
segregated, concentrated waste streams, and through the use of
synthetic tanning agents (syntans). A number of process chemical
substitution opportunities exist; some of these opportunities are
liscussed later in this section.
4ater Conservation and Reuse
\ tannery survey of water needs will help to reduce the volume of
vastes because water usage generally exceeds the quantity needed.
Some methods of water conservation are listed below:
1. Encourage employees to implement any potential
water saving practices. Eliminate the
constantly running hoses observed in (a few)
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tanneries (one practice requiring employee
participation) .
2. Examine tanning formulas to determine if floats
can be reduced. Use of hide processors
and other specially designed vessels has
permitted use of lower float volumes.
3. Limit or eliminate some washing and rinsing
operations.
a. Use batch rinses, or alternative ly, use
the counter-current flow technique.
b. use preset meters or timers to limit total
flow.
4. Use of wash waters and rinses for process solution
makeup.
5. Use of equipment such as hide
processors, pumpable drums (rather than floor
dumping), float storage tanks, and other reuse
equipment.
6. Recirculation of non-contact cooling water,
such as for vacuum driers.
Tannery no. 397 has undertaken a comprehensive water conservatic
program. Through implementation of this program, total water use h
decreased by nearly 50 percent. Installation of hide processors fc
washing the incoming hides has reduced water use in thif process hv -
^^ °fPr°CeSS Wat« in th
savinasol °2sPr°CeSS Wat« in th* ^"9 operationa achiev<
savings of 25 percent. Installation of paddle vats and
recirculating flume arrangement following the un hair ing operation V
-
~~~ « - s -
tine screen for solids removal. A vegetable tanning recycle ar
reclaim system using evaporators has reduced water uL for +M
In recent years, the hide processor (modified concrete mixer) ha
proven to be an extremely effective means of reducing water use and a
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en hide processors are used in the beamhouse operation, water use
xough deliming will be about 8.35 I/kg of hide (1 gal/lb of hide).
nnery 444, which uses hide processors for all operations from the
.w product through chrome tanning or "blue" stage, has indicated that
.ter use is from 12.5 to 16.7 I/kg of hide (1.5 to 2.0 gal/lb of
.de).30 Some tanneries use hide processors in the retan, color, and
.tliquor operations.
iere are also reports of water reuse from one process to another.
.nnery no. 24 uses the same water for washing following their
lodified pickle" operation and their vegetable tanning operation.30
iere are also some indications that retan operations can use spent
.quors from the vegetable tanning process. Tannery no. 144 indicates
;e of bate wastewater for alum tanning make-up water.30 Tannery no.
J5 plans to recirculate approximately 20,000 gallons per day of
reatment plant final effluent water for use in the delime wash which
>llows the hair pulp process and for wash water following the bate
rocess.30
le Institute for Leather and Shoe Research (TNO), of the Netherlands,
ctensively researched water reuse. The water consumption in upper
rather tanneries including rinsing processes appears to be 70 to 100
'kg hide and in sole leather tanneries 50 to 60 I/kg hide.31 The
:udy indicated that 80 to 90 percent of effluent volume comes from
Lnsing before and after the different wet tannery operations.
irough measurement of the electrical conductivity of wash waters it
is found that the conductivity decreases very rapidly after a short
Line; after that, the decrease is small in proportion to the amount of
iter used. It appears, therefore, that either shortening the rinsing
Lme substantially or replacing the rinsing by washing will save a
insiderable amount of water.
ible 18 presents a comparison of procedures for continuous rinsing
.id batch washing. The batch washing procedure reduces the water
Dnsumption to one-fifth of that in the standard procedure (a
eduction of 80 percent).31 It was shown that process time can be
Dnsiderably reduced also if the hides are not too dry. Differences
.1 leather quality were very small except for the distinctly tighter
rain obtained with the new procedure,,
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Table 18. Soaking of Wet Salted Prefleshed Hides
With Continuous Rinsing and Batch Washing
Standard Procedure New Procedure
Rinse continuously 1/4-hour Wash 1/4-hour with 250
percent water at 25°C
Drain- Stop for 1-1/2 hours
Add 250 percent water at wash 1/4-hour (same water).
18 degrees C.
Drum 5 min/hour for 7 hrs. Drain.
Drain.
Add 250 percent water at 18°C.
Rest overnight (15 hours).
Total time—24 hours Total time—2-1/2 hours.
Water consumption: 12.5 I/kg water consumption:
— nj-de 2.5 I/kg hide
Many tanneries in Australia have recently economized in the use
water, particularly by eliminating waste in washing and by the use
lower floats However, lessened water use tends to increase t
suspended solids and BOD concentrations in the wastewater stre^?32
German literature has reported that "previously about 75 percent
resultaanS°Ual<,n T^ ™S US6d f°r rinsing orations and as
result, and also as a consequence of working with long floats t
and^nf ^v ?**? *?**** ™facturerwas somewhere
140 and 200 I/kg of salted hide. When rinsing is replaced by bat
washing the amount of water can be reduced. short floats in t
tannery operations lead to reduction in process time and a faster a
more uniform uptake of chemicals, without the danger of a loose grai
I/kg h!de?"32he t0tal am°Unt °f Water use can be reduced to 35 ?o
French and British research institutes support the replacement <
rinsing by batch washing. 3 2 In Great Britain, tanneries
considering the reuse of liquors either direSly or after bioLaic
Based on a total plant consumption basis, Perkowski indicated that <
— German tanneries water use was reduced from 200 I/kg of raw hie"
some
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processed to as low as 40 I/kg while employing various reduction and
reuse procedures. 33 Work was also done on the following to reduce the
quantity of pollutants entering the wastewater stream:
1 Brushing off adhering salt from the salted hides before
soaking;
3. Removing lime sludge; the lime can be used in agriculture or
can be burnt in a kiln to recover quicklime (a possible lime
recovery scheme)«32
P.J. Van Vlimmeren, at the Institute for Leather and Shoe Research
(TNO) in Holland, has investigated water recovery and reuse schemes
within tannery processes. He reports that when unhairing is possible
in the first or second soaking liquor (i.e., in a salt solution), 70
to 80 percent of the organic pollutants and nearly all the
preservation salt can be collected in about 5 I/kg of raw hide
processed. "For example, a tannery which was using 14.3 litres
water/kg hide in soaking to reduce the salt content of the hide to 2
percent could obtain the same salt content by washings with altogether
4.2 litres water, i.e., a reduction of about 70 percent."32
Water use reduction and the associated changes in pollutant loading
were reported as follows for a U.S. tannery (No. 431) studying the
effects of in-plant process changes:
"Hide processors were installed and the traditional hair-
save methods of leather production were replaced by a
•straight through1 hair-burn process in which soaking,
unhairing, bating, pickling and tanning is accomplished
within a single processing unit. Besides eliminating
numerous hide handling steps, this process change effected a
50 percent reduction in beamhouse-tanyard effluent volume
from an average 107 gallons per side to 54 gallons per side.
While much of this water was eventually restored as 'sewer-
flushes,' an overall 38 percent reduction in 1970 effluent
volumes has been observed, primarily due to an intensive
water conservation campaign. Consistent with a 50 percent
reduction in lime usage, the pH was lowered from 11.0 to 9.8
with a corresponding 31 percent reduction in fixed suspended
solids."34
Other tanneries reporting on their extensive and intensive wastewater
reduction program indicated that, typically, the first 50 percent
reduction was achieved primarily by educating all employees on water
conservation practices and management emphasis on constant use of such
practices. Water reuse within specific processes in the tannery is
the second thrust of this wastewater reduction program. Reuse
technologies tend to involve simple, widely used equipment such as
cooling towers, filters, separators, decanters or holding tanks. The
cost of purchase and installation is rapidly recovered by reduced
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water and chemicals use, lower sewer charges or less obviously by
reduced loading of a tannery's own treatment system.
-V*
A concomitant of water use reduction may be an increase in a pollutant
concentration in pretreated discharges to municipal systems. Most
municipal ordinances regulating discharges to a sewer specify
concentration limits. A joint understanding of the actual municipal
requirements at a specific sewer inlet and of the likely consequences
ot a water reduction program in a tannery would be a vital first step
to an informed decision by both a municipality and a tannery on
controlling wastewater volume, pollutant concentration, and/or
pollutant loading.
Repair and Replacement of Faulty Equipment
Industrial waste problems are often complicated or intensified by the
fact that faulty or obsolete process equipment remains in service
without proper repair or replacement. Operating personnel also can
increase waste disposal problems because large quantities of usable
materials often are lost through careless or accidental spills or
through excessive drainage of liquids from hides as they are
transferred from one process to another. Emphasizing the importance
of eliminating these sources of wastes often simplifies waste disposal
problems.
Automatic Monitoring Devices
No waste reduction and elimination program can be complete without
adequate control measures. Automatic monitoring equipment for
detecting abnormal levels of selected constituents closely guards
against the failure of established precautionary measures. For
example, abnormal and accidental concurrent discharges of concentrated
highly alkaline lime-sulfide unhairing liquors and highly acid
chromium tanning or pickle liquors are immediately detectable by DH
meters and alarms installed on the effluent lines from these
processes. In addition to indicating loss of materials, automatic
sensing devices also can operate recovery equipment.
Recovery and Reuse of Process Chemicals
The most efficient method of eliminating pollutants from tannery
wastes and of reducing the volume of effluent is through reuse of
water and chemical agents and through recovery of materials which are
normally wasted.
Reuse or reduction of process solutions or recovery of process
chemicals are demonstrated methods of waste constituent reduction. A
detailed summary of methods available to reduce waste constituents bv
process adjustments is given by Williams-Wynn.as
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\ number of vegetable tanneries are using recycle systems to reduce
^he amounts of tan liquor discharged into the waste streams. The
jiritan process employs such a technique by counter-current flow of
-annage in relation to the hides. In most cases, some blowdown is
necessary to prevent the build-up of contaminants in the tanning
solution. One tannery recovers this blowdown tan liquor, concentrates
Lt in a triple effect evaporator and sells the concentrated liquor.
Dther tanneries use this blowdown liquor in retanning operations.
Reuse or recovery of chrome tan liquors also exists but not to the
same extent as vegetable tanning. Hauck36 has summarized methods for
recovery and reuse of spent chrome tanning solutions. During World
rfar II, the reuse of chrome tan liquor was common practice because of
the scarcity of chromium salts.
Tannery no. 279 studied the reuse of chrome tanning solutions. These
tests showed that the chrome liquors could be reused for periods of up
to six weeks without reduction of leather quality.30 The spent tan
Liquor in this study was settled and sludge was drawn off the bottom
of the holding tank. The clarified solution was brought to the
required concentration with chromium salts, sulfuric acid, and sodium
chloride. Because of the sludge drawoff, this was not a complete
recycle system; however, a substantial portion was recycled and only a
small amount wasted.
This same study also examined the feasibility of recycling of the
unhairing solutions. Tests on recycling of the unhairing solutions
were performed on three separate occasions. The longest recycle time
was two weeks. The study concluded, however, that since the
concentration of waste material in the solution leveled off after a
few days, the solution conceivably could be reused indefinitely. The
spent liquor was drained and settled in much the same manner as the
chrome tan liquor. After removing the sludge from the bottom of the
tank, 65 percent of the original volume remained. About 50 percent of
the sulfhydrate and the lime needed for the next run was available in
that portion retained for reuse. After two weeks of use, the solution
had no objectionable odor and the amount of ammonia coming off was not
considered substantial.
Tannery no. 253, a shearling tannery, has been able to reuse its
chrome tan solution up to five times.30
The same tannery has reused its pickle liquor up to five times. This
is accomplished through refortification of pickle liquors by the
addition of chemicals prior to adding another load of hides.
Tannery no. 388 reports reusing retan liquors.30 Tannery no. 385
reports reusing the finishing oils.30 Many tanneries report recycling
their pasting frame water, either wholly or partially.
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Stream Segregation
In-Plant Treatment. Stream segregation is not an in-plant treatmen
technology, ^er. se. it is, in reality, a critical first step t
implement most in-plant technologies available to tanneries. It i
the physical separation or segregation of at least the two majo
wastewater streams in a tannery. One stream originates in th
beamhouse, is highly alkaline, and contains a substantial organic loa
of dissolved and suspended hair. The other stream originates in th
tanyard, is acidic, and has a chrome content of measurable level.
These two major and substantially different wastewater streams can b
most effectively pretreated as separate streams rather than in
combined state. These two major streams are the specific proces
waste streams which respond more completely and cost effectively t
separate treatment. *
Based upon information from tanneries no. 237 and 431, EPA develope
proportionate raw waste load flows and pollutant loads from th
beamhouse, and from the tanning, retanning, and wet finishin
operations. The values for the various wastewater parameters
including flow, are presented in Table 19.
Table 19
Proportioned Flows and Pollutant Loads for Beamhouse and
Tanyard/Retan/Wet Finish Operations
Parameter
Flow
BOD5
COD
TSS
Oil and Grease
TKN
Ammonia
Chromium
Beamhouse
40X
65
56
69
49
46
0
0
Tanyard/Retan/Wet Finish
60%
35
44
31
51
54
100
100
The isolation of the specific process waste streams or the segregatioi
of the two major streams can be accomplished by a variety of
means such as the following:
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1. Pump-out mechanism on the drum, wheel, vat, or other
processing equipment connected to a specific holding or
treatment tank or vessel by piping;
2. Collection of wastewater discharged from a hide processing
vessel directly into a holding or treatment tank or
container;
3. Separate below-grade sewers;
4. separate above-grade sewers; and
5. Flow direction control diverters in grate- cove red floor
troughs.
Control of Specific Waste Constituents
Reduction. Lime used in unhairing liquors is responsible for the
alkalinity of the final effluent. Insoluble calcium compounds simply
add to the sludge quantity. Though the pH of the mixed effluent has
to be sufficiently high to precipitate chromium salts, it is desirable
bo reduce the amount of lime to a minimum. Experiments at the
Institute TNO by P.J. Van Vlimmeren "have shown that an amount of U
percent hydra ted lime (on salted weight) is an optimum level with
regard to the quality of the leather.1131
"Because lime has a limited solubility, it is generally regarded as a
•safe1 alkali for use in unhairing. Consequently, tanners are tempted
to use a considerable excess of this material — far more than is needed
to satisfy the alkali-binding capacity of the skin collagen and to
keep the liquor saturated with lime." So reports D. A. Williams-Wynn
of the Leather Industries Research Institute (South Africa) in a
report concerning various operable concentrations of lime liquors.
The study points out that, "the disposal of this excess of lime, most
of it undissolved but not easily settled, especially in the presence
of soluble protein, is a problem with which tanners constantly
grapple, yet they persist in using a large excess."35
Their "experiments have shown that the amount of lime needed for
effective unhairing is less than is required to saturate the protein,
so there is certainly no justification for any undissolved lime to ce
present in beamhouse liquors."35
Table 20 lists the values for insoluble calcium hydroxide in effluent
from 6-day hair-saving pit liming processes in which the lime offer
was progressively reduced. The table is reproduced from William-
Wynn's published study.35
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Table 20. Analysis of Lime Liquors
Lime Offered
4 percent
3 percent
2 percent
1 percent
Insoluble Ca(OH)_2
in Lime Liquors
0.43 percent
0.22 percent
0.01 percent
KT-i 1
Lime Unused
53. 5 percent
36. 6 percent
3. 5 percent
~ ^"C"U . Nil Nil
"Unhairing was effective even at the lowest level
of the lime
amount under two percent seems to be the
anao«
and 0.4 percent. The values are means of fnnr-
determinations averaged over the four sulfide con^ntrat ionf. "3 *
"In a hair-burning, drum-unhairing process in which the sulfide
off^* W?S mu°h
-------
The following summary is quoted from Money and Adminis1 research:
"It has been shown that lime-sulphide unhairing liquors can be
recycled more than 20 times, perhaps indefinitely. The only
treatments necessary before re-use are temperature adjustment and
replenishment with lime, sulphide and water, preferably as
washings from the previous unhairing. For 20 cycles the average
consumptions based on greenhide weight were 1.5% lime, 2.2%
sodium sulphide and 40-55% water; the higher water usage occurred
when solids were removed before each use, a procedure which has
advantages. Salted hides can be unhaired satisfactorily in re-
used liquors if they first have an adequate soak to reduce their
salt content. Recycling of lime liquors has no apparent effect
on leather quality or yield even though, when compared with
conventional unhairing, it results in a decrease in hide swelling
and an uptake of proteins of their degradation products. This
method could be developed as a no-effluent system of unhairing if
liquors can be cycled indefinitely or, after a certain number of
cycles, can be utilized as a source of protein. Even if the
liquors are discharged after 20 uses there can be overall a 20-
fold reduction in effluent sulphide, seven-fold reduction in
effluent lime and protein, and a five-fold reduction (80 percent)
in the amount of water used. If wash liquors from the previous
unhairings are used to replenish the float, as is recommended,
the fresh-water consumption could also be reduced 20-fold (95
percent)."37
Obviously it is simpler to leave the solids in the liquor. However,
if they are removed after each use (or several uses) there is no
problem with fat accumulation, the protein recovery is greater, and
the hides are cleaner after unhairing. Vibrating and rotating screens
and other systems for removing the solids from the liquor are being
investigated. It is an advantage to be able to remove the hair debris
and fats without removing all the insoluble lime. The present work
has shown that only a small proportion of the lime liquor protein is
lost as volatile products, but substantial amounts of the protein or
its degradation products are taken up and retained by the hide. It is
estimated that a hide unhaired in a recycled liquor would contain more
protein, approximately 1 percent of the green hide weight, than it
would if unhaired in a fresh lime liquor. This extra protein could be
beneficial by adding substance to the leather, and it could affect the
feel of the resultant leather; but in the matched-side trials no
differences have been detected in the final leather.
Most existing beamhouses would have to be modified for recycling of
lime liquors, and the facilities necessary will be similar to those
for recycling chrome liquors. Rapid and effective drainage of the
liquor can be achieved by using a drum with a perforated false bottom
covering a drainage valve, or a hide processor or cement mixer.
Provision of a storage tank capable of holding the daily output of
lime liquors plus washings would be preferable; but it may be possible
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to pump liquor directly from one drum to another. A pit unhaird
system would be ideally suited to recycling, although floats a
amounts of reagent would differ from those given for drum liming.
A sulfide reuse system has been installed and used by tannery no. 2
(subcategory one - Hair Pulp/Chrome Tan/Retan-Wet Finish). Th
system has achieved a reduction in sulfide-containing wastewater fr
27,000 gpd to 10,000 gpd.
This reuse scheme was developed by an Italian engineering fi
(Idronova) and operates with sedimentation and filtering equipme
used by the European wine industry. The system operates as follows:
1. The unhairing float from the hide processors is pumped to
enclosed holding tank at 12 gpm. From there it is pumped
a rate of 20 gpm to a hydrodynamic sedimentator whi
facilitates solids settling and filtration of the flo
during gravity flow. Pumps provide circulation and si
reduction to reduce large solids to about 1/4 inch size.
2. Solids are settled out using gravity and centrifugal for
with the solids being drawn out the bottom of the unit in
a solids container for disposal. oil, grease and oth
floating material are skimmed off the top of the solids bo
3. The supernatant sulfide liquor flows close to the top of t
separation chamber, where it is drawn off. The reclaim
liquors flow by gravity to two large storage tanks. Fr
these tanks the reclaimed liquors are pumped back to t
hide processor. Some sludge build-up occurs in the
storage tanks, but it is subsequently discharged a
disposed of as solid waste.
4. The tanks are closed and vented outside the the building
prevent any build-up of sulfide in the building. 1
storage tanks are also provided with mixers.
Enzyme Unhairinq for Hair-Save Operations. Prerequisites for a
hair-saving method are: it must unhair easily and mechanically, wi
removal of fine hair (if possible without reliming); it must
economical, not time-consuming; it must be suited to mechanized a
automated production processes; and it must give good leather qualit
Hair-saving processes require more labor than hair-burn processes, a
tanners will not incur additional costs unless there is a profit fr
the proceeds of the hair and a cost savings in wastewater treatmen
Present trends in the industry are definitely toward the hair-bu
process.
Frendrup and Larsson** made a detailed study of the effects of vario
depilatory methods on the characteristics of the residual waste
They found that when hair was loosened chemically and remov
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mechanically, the total nitrogen content of the unhairing wastes
averaged 1.2 g/1. When the hair was destroyed completely by chemical
means (hair-pulping or burning), the total nitrogen content ranged
from 5 to 7 g/1. In addition, an appreciable reduction in oxygen
demand, and in quantities of sulfides and sludge was observed with
hair-saving methods. Hair containment and housekeeping practices are
significant influences on these results.
Enzyme unhairing is one of the hair-saving methods known at the
present time. Based on a considerable amount of work by the TNO
Institute, this method reportedly could be developed for use in the
production of sole leather, but for upper leather some difficulties in
connection with the feel of the leather still must be overcome. A
combination of the Liritan vegetable-tan process and enzyme unhairing
(for sole leather) was also investigated at TNO.3* The latter
combination of the two developments reduced pollution by vegetable
tannage to only 10 percent of that from traditional methods, according
to TNO.
Sulfide Removal. In situ sulfide oxidation in the drum or paddle with
the hides has been investigated and is in use. TNO Institute
investigated3i this method of oxidizing sulfides in the lime liquors
during and after the liming process. It was found that a vigorous
movement of the liquor and a free air supply are very important. In
the alkaline medium the manganese catalyst converts into insoluble
manganous hydroxide. Flotation of the hydroxide by hair remnants or
foam must be prevented to retain the catalytic activity. When the
oxidation of sulfides is combined with the liming operation the latter
is started in the usual way, either in a paddle or in a drum. After
complete removal of the hair, a small amount of manganous sulfate,
e.g., 200 g/cubic meter (m3), is added and paddling or drumming is
continued for some additional time. Using hair-burn liming procedures
and the lowest sulfide concentrations necessary for complete unhairing
and the production of good quality leather, over 95 percent of the
residual sulfides could be removed by oxidation within three hours.
This additional drumming had little effect on the appearance and
physical properties of the leather produced in this way. Tannery No.
245 is using this method of in situ sulfide oxidation as standard
practice.
The TNO technique of in situ sulfide oxidation in combination with a
sulfide liquor reuse system reduced the sulfide content of the
wastewater discharged to POTW from 118 mg/1 to about 2 mg/1 concurrent
with a reduction in wastewater volume.
Chrome Reduction. Tanyard wastewater is generally acidic and, because
of the chrome content, is toxic to some organisms. The acidic nature
of the waste stream can be neutralized by mixing with the beamhouse
wastes that are alkaline or by pH adjustment with chemicals. The
chrome content can be reduced by using one of a number of
technologies. One technique is to increase the uptake of chrome by
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the leather in tanning. A second is to reuse chrome liquors, as is,
in some part of the beamhouse, tanyard, or retan process without first
recovering the chrome from the solution. A third way is to
precipitate the chrome with an alkaline chemical, producing a chrome
sludge either for disposal or for chrome recovery. The alkaline
chemical source can be beamhouse waters, fresh lime, or bases such as
caustic soda or soda ash.
Aside from their application as methods of reducing the chrome content
in tannery wastewater some of these methods have been used in the past
as chrome conservation methods. During World War II, chrome supplies
were cut off and tanners were able to reduce their chrome use 20
percent.39 under current conditions of increasing chrome prices and
reduced imports, an economic incentive exists for tanneries to
introduce these methods of chrome conservation, which will improve the
wastewater quality as well. In fact, several tanneries have already
started chrome recovery and reuse programs.
Increasing the uptake of chrome is an effective method of reducing
chrome in the wastewater and conserving chrome. Chrome fixation can
be increased by increasing the chrome concentration, increasing the
temperature, adjusting the concentration of neutral salts to the
minimum required to prevent swelling of the hides, increasing the
basicity of the chrome waste slightly, and adjusting the pH of the
tanning liquor during the tanning process. Some of these methods may
affect the quality of the leather.*« After World War II, tanners went
back to the older methods. The efficiency of chrome use is now about
70 percent.3*
Reuse of chrome liquors without first removing the chrome has been
extensively studied recently and is practiced in some tanneries. From
the literature it appears that the most common technique in chrome
liquor reuse is to fortify the liquor with acid and salts and use the
forfifled liquor in the pickling process. The chrome introduced into
the pickling liquor gives a pretannage.
Scroggie and others in Australia did a series of studies on reuse of
spent chrome tanning liquors for pickling. In the fourth part«o of
the studies the spent chrome liquor was used to make up the pickling
acid added to the hides right after the bate. The hides were obtained
from five different Australian tanneries. Scroggie obtained more than
5 percent uptake of chrome as Cr2o3 on a dry weight basis. This
chrome was distributed in a normal fashion throughout the hide. He
reused the chrome 12 times over the course of several months and noted
that the concentration of neutral salts reached steady state in about
J to 4 cycles. He recommended that "the liquors can apparently then
be used indefinitely (with occasional screening, etc., as
necessary). "*o ^' uv" ' "*
In further studies**, Scroggie ran actual plant tests at an Australian
tannery which used hide processors for the tanning process. He found
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that a savings of about 25 percent could be realized on tanning
reagents in Australian tanneries. A second run of 18 successive
cycles over the course of several months again revealed that neutral
salt concentration reached steady state after three or four cycles.
Scroggie also thought that hide processors were better than drums for
this sort of recycle process because the lime and bate liquors can be
readily removed as needed minimizing volume build-up and problems with
pH. It is also possible to pump spent chrome liquor out below the
level of the oil layer and to pump the sludge out of the bottom of the
hide processors to get a clean recycle stream. It is possible to
remove about 95 percent of the spent chrome liquor from the
processors. There is about 20 percent savings of chrome, complete
savings of neutral salts, and no increase in dissolved protein.
Scroggie also indicates it is possible to modify a tanning drum for
reuse to get similar results. Scroggie further reported that:
"Throughout the entire process the 're-cycled' leather was at
least comparable with corresponding leather from the normal
production. On removal from chrome-tanning, the leather showed
no difference in general appearance, grain quality, or 'feel1 and
there was no grain 'draw1, chrome 'blotching' or veininess
apparent; random cross-sections showed a complete chrome
penetration in all cases. These observations were confirmed by
the tannery personnel who carried out a complete assessment of
the finished leather. They reported that there was no difference
in the subjective properties of the 're-cycled' leather when
compared with normal production leather of the same type.
Neither was any difference detected between 're-cycled' and
control sides in Lastometer load or distension, or in Cr2<33
content or ash weight of the finished leather."41
And he concluded that:
"A method is now available for the re-cycling of chrome liquors
which can be fitted into current production schedules in
tanneries and which has been shown to produce leather of
comparable quality to that produced by conventional
processing."4l
In the sixth part of his studies42, Scroggie reported on a series of
full-scale tannery tests of chrome recycling. He stated that the
common chrome uptake of 70 to 80 percent is a consequence of the law
of mass action—reaction rate depends on chrome concentration—rather
than any inactivation of the chrome complexes thereby requiring an
intermediate reactivation before reuse. Thus, direct reuse is an
effective technique. He found that the solid commercial chrome
preparations were better than the liquid forms because there was no
accumulation of excess chrome liquor to be disposed.
Hide processors have the best drainage characteristics for recycling
chrome, but they should be lined to prevent corrosion. Two collection
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tanks for the chrome liquor are necessary. Lime-sulfide unhairinq
solution recycling is desirable but not necessary for effective chrome
recycling. in several of these tests the quality of the leather
decreased. This was traced to a slight acidic swelling of the hide
Scroggie lists several advantages of chrome reuse. The first is that
the possibility of shock loading on the secondary biological system is
reduced. The second is that the required amounts of sodium chloride
and sodium sulfate are reduced. The third is that there is a saving
of 20 to 25 percent of the associated cost for the process in
Australian tanneries. The other three advantages of chrome recycling
which he cites are: j-j-"y
"(iv) With proper control, leather of at least comparable quality
to conventionally tanned leather can be produced while there are
indications that leather quality can be improved in some
respects.
" (v) Recycling is considered to be superior to the alternative
method practiced in some overseas countries of chromium
precipitation and recovery as it is more convenient to use and is
less costly. It is also considered to provide a more complete
solution to the problem than that provided by attempts to improve
the uptake of chromium, for example, by the use of very low
floats or more highly reactive chromium reagents.
"(vi) The possibilities for economic utilization of tannery
sludges are extended by the exclusion of chromium which is
precipitated in such sludges by the common method of mixing of
all tannery processing effluents for treatment."
Ward, Slabbert and Shuttleworth have described tests of chrome reuse
and recovery in South Africa.*3 The sulfate reached steady state after
four cycles. Chrome analyses and other precautions are recommended.
France** studied the use of organic acids for pickling and later
studied recycling of spent chrome/organic acid liquor to the pickling
process. He tested his method at several tanneries and found little
difference in the properties of the leather produced by his method and
conventional processes. He obtained faster tanning and better
exhaustion with his method. He tried recycling of the liquors for
even greater efficiency and possible economic advantages. He advises
against reusing the wring liquor because of its fat content. He also
advises pumping the spent chrome liquor about 2 feet below the oil
r^ J /^T ^* SlUdIe leVel- He found that less chrome c°uld be
charged and all of it used. About half as much time was required for
S^h Fr?CeS?i af H?6 convention<*l Pickle plus tan processes require.
With a low float, the pickle may even be eliminated in some cases
His process requires no added salts because the low float results in
more concentrated liquors. About 10 to 11 percent of the recycle"
stream consists of soluble salts at steady state. The cost of the
organic acids, a mixture of formic and acetic acids, is higher than
sulfuric acid. The same amounts are used, but faster processing is
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possible and savings in other chemicals can cut overall costs. He
mentions that this process is already in use but does not mention
where. The additional equipment required for this process is one
tank, one pump, and some piping; investment could be low for this
reason.
Pierce and Thorstensen have published an account of the chrome reuse
at tannery no. 245. *5 Hide processors are used at this tannery. The
spent chrome liquors are collected in a tank large enough to hold six
tannages. Oil and grease are skimmed to prevent darkening of the blue
stock, and the liquor is used for pickle make-up. Sulfates and other
salts build up at first but eventually level off. There is more spent
chrome liquor available than is required for pickle. When the excess
completely fills the tank it is precipitated with soda ash and sodium
hydroxide for reuse. This does not decrease the amount of chrome used
in the tanning process, but with the reuse of chrome in the pickling,
there is increased uptake without additional chrome being bought.
Pierce and Thorstensen note that the system saves money and that the
chrome released to the sewer typically is 1.6 mg/1 (as Cr) , based on
an effluent flow of 600,000 gallons per day.
Tannery no. 233 is reusing chrome. The chrome liquor is collected.
They skim grease and remove the suspended solids. Then they use the
clear chrome liquor without grease or fibers as a pretan. If the
grease is not removed there can be a color problem. Previously they
precipitated chrome with beamhouse waste from a pigskin unhairing
operation or sold spent chrome. A concentration of 2 mg/1 of chromium
has been achieved in the total discharge to the municipal sewer.
Precipitation of chrome for recovery was practiced in World War II.
Hauck has published a paper outlining the methods in use then and
known now. Precipitation may be accomplished by beamhouse wastes, by
fresh lime, or by bases whose sulfates are soluble, such as caustic
soda or soda ash.36 The chrome precipitate may be disposed of or
recovered for use in the process. Hauck recommends using a base whose
sulfate is soluble for the precipitation. In this case the chrome
precipitate may be washed to remove the sulfate before the chrome is
recovered. This prevents build-up of salts. He finds that fresh lime
is not as good because the calcium sulfate whch is formed cannot be
washed out. He recommends using beamhouse waste for the precipitation
only if the chrome is to be disposed of instead of recovered. For
reuse the chrome precipitate is redissolved in sulfuric acid, the
chrome solution is analyzed, the basicity and salt concentrations are
adjusted and it is ready for reuse.
An article in Leather and Shoes describes chrome precipitation with a
proprietary buffer mix.46 The supernatant chrome concentration
reportedly can be lowered to about 0.1 ppm average (range 0.06 to 0.5
ppm) with this product.
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A new process for chrome precipitation uses sulfides. This process
called "Sulfex", avoids the problem of the possible evolution of
hydrogen sulfide by using only a small amount of soluble sulfide in
equilibrium with an excess amount of nearly insoluble iron sulfide
The leftover iron sulfide is filtered out with the precipitate. This
process appears to be useful for removing small amounts of chrome
remaining in the wastewater after the bulk of the chrome has been
precipitated. It does not appear to be suitable for bulk
precipitation of chrome.** *e
A full-scale tannery test of chrome precipitation and reuse was
conducted at tannery no. 431.34 During this test only part of the
chrome liquor was collected for precipitation. The entire liquid
contents of the hide processors used for chrome tanning were collected
in a tank at the end of the tanning process. None of the chrome
liquor from retan or chrome-containing liquors from operations such as
wringing was collected. About two-thirds of the chrome was collected
and about one-third was not. The collecting tank could hold the
contents of two hide processors at once. Alkali and polyelectrolvte
were added, soda ash and lime were the alkalis tested to determine
which was the more cost-effective. The precipitated chrome sludge was
thickened to about half its original volume, then further thickened on
a vacuum filter. The chrome sludge cake was conveyed to another tank
and dissolved in sulfuric acid. A cyclone separated the insoluble
calcium sulfate from the dissolved chrome and the chrome solution was
then stored for reuse. This precipitation process recovered between
98.0 and 99.9 percent of the chrome from the liquor. When lime was
used to precipitate the chrome, some of the chrome ended up in the
calcium sulfate sludge which was to be landfilled. In this case about
66 percent of the chrome was recovered in usable form. The effluent
trom the chrome recovery system contained about 2 mg/1 of chrome
Because only part of the chrome was treated, however, the reduction of
™ o f ?v c^omiim ln the effluent was 37 to 40 percent. Collecting
more of the chrome would result in a greater reduction of the total
chromium even if the treatment efficiency was not as high. EPA's
pretreatment standards and effluent limitations assume a chromium
r^?rVTtem
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noted by data from tannery no. 431, over 98 percent of this chromium
is assumed by EPA to be recoverable.
Ammonia Nitrogen Reduction. The nitrogen loadings in the raw waste of
a hair-burn process have been reported as follows:
1. The average TKN loading for subcategory one (hair pulp,
chrome tan, retan-wet finish) is 11.7 kg/kkg and the average
ammonia nitrogen loading is 5.5 kg/kkg hide.49
2. An EPA sponsored tannery study reports 15.7 kg/kkg of hide
of TKN, and the 4.6 kg/kkg of hide for ammonia nitrogen, in
which the bating operation is totally responsible for the
latter.34
These loadings indicate that the elimination of nitrogen-containing
deliming chemicals during the bating process would significantly
reduce the ammonia nitrogen and TKN in the effluent.
Koopman of TNO has analyzed residual liquors for nitrogen in a paper
on deliming with magnesium sulfate.5° The standard procedure (deliming
with 3 to 3.5 percent ammonium sulfate) produces a total nitrogen
content of 7 kg/kkg of hides; in comparison the test procedure (7
percent magnesium sulfate) results in a total nitrogen content of 0.62
kg/kkg of hides. Koopman also indicates a total addition of 7.4
kg/kkg of ammonia sulfate, which is 0.4 kg more than the residual. He
attributes this loss to some of the nitrogen from the ammonium sulfate
escaping in the form of NH_3 gas during deliming.
Koopman elaborates in his paper50 on alternative deliming media as
follows:
"The purpose o." deliming is partially or completely to neutralize
the bases present in the hide without giving rise to acid
swelling. In this process, the lime must also be partially
removed in order to prevent the formation of spots.
"The deliming media in use in leather preparation may be divided
into four groups: namely, ammonium salts, strong deliming acids,
weak deliming acids, and deliming with magnesium sulfate.
"1. Ammonium Salts
"In the deliming of cowhides, use is made preponderantly of
ammonium sulfate and ammonium chloride, alone or in combination
with acid. The combined action of ammonium salt plus acid
depends on the principle that the ammonia, which the lime in the
hide frees from the ammonium salt, is again converted to the
ammonium salt by the reaction with the added acid. Ammonium
salts of organic acids are used as well, frequently with addition
of organic acids with the same acid residue as from the ammonium
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salt. Thus buffer solutions are created, which have the property
that they can be used to neutralize reasonable quantities of lye
without danger of excessive pH, which might give rise to acid
swelling.
"The use of ammonium salts in the deliming of cowhides confers
the following advantages:
1. Deliming can be accomplished rapidly.
2. No acid swelling can occur during deliming.
3. Alkali swelling is largely eliminated.
4. The most frequently used ammonium salts (sulfate and
chloride) are inexpensive.
"2. Strong Deliming Acids
"In addition to strong inorganic acids like hydrochloric and
sulfuric acid, a number of organic acids must be included in this
category, such as formic acid, acetic acid, lactic acid, and
aromatic sulfonic acid. Strong deliming acids, such as
hydrochloric and sulfuric, are cheap. They are in general use as
preliminary deliming agents, achieving a superficial deliming.
Because of the fact that with these strong acids the pH during
the deliming can fall very rapidly, there is always the danger
that acid swelling will set in the delimed outer layers of the
hide before the acid has had time to penetrate deeper into the
hide and delime the deeper layers. The somewhat milder lactic and
formic acids can be safely used, adding them in installments and
checking the pH of the deliming liquor and the hide. Because of
the slow course of the deliming, these acids are used principally
in the deliming of thin skins (goat, sheep, calf), and not for
cowhide. Disadvantages associated with the use of organic acids
are their high price, together with the resulting higher COD
content of the wastewater.
11 Weak Deliming Acids
"These do not directly displace the lime bound to the hide.
After neutralization of the lime that is still present in the
capillaries, the balance between chemically bound and free lime
is shifted, the free lime is neutralized, and so on. This
process takes place very slowly, so that these acids can
penetrate into the interior of the hide and provide uniform
deliming. The most important agents of this group are boric
acid, and sodium bisulfite. Boric acid yields leather with a
handsome grain, and is partly on that account regarded as one of
the best deliming agents. Its relatively high price and the
slowness of the deliming process will stand in the way of its
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general adoption in the manufacture of cowhide. Because of the
low acidity of boric acid, a substantial excess is required in
order to obtain complete neutralization of phenol phthalein.
Sodium bisulfite is more frequently used as a deliming agent than
boric acid. Commercially, it is available mostly in anhydrous
form as sodium metabisulfite, Na2S2O5f in aqueous solution
yielding the weak acid bisulfite NaHSO3. During deliming, sodium
bisulfite is converted to calcium sulfite, which is not easily
soluble in water, but the solubility can be increased by addition
to the deliming liquor of an excess of sodium bisulfite, thus
avoiding possible spotting. Deliming with bisulfite has the
disadvantage that in an acid medium the rather aggressive sulfur
dioxide can escape.50
"4. Deliming with Magnesium Sulfate
"The fact that ammonium sulfate and chloride give very rapid
deliming of cowhide led Koopman and the other researchers to the
idea that this property might also be possessed by magnesium
salts, in this case the sulfate (epsom salt) and the chloride.
The OH- ions from the pelt are bound in a similar manner without
danger of acid swelling according to the following equation:
Mg+2 + 20H- = Mg(OH)2
"The chemical reactions for deliming with ammonium sulfate and
hydrochloric acid are:
(NH4_)2SO4 + Ca(OH)2 = CaSOU. +
2NH40H + HC1 = 2NH4C1 + 2E20
and for deliming with magnesium sulfate and hydrochloric acid:
MgS04 * Ca(OH)2 = CaS04 + Mg (OH) 2
Mg(OH)2 + 2HC1 = MgCl2 + 2H20
"It is apparent that in addition to the precipitation of CaSOj* in
the hide, there is now also a precipitation of Mg(OH)2. Alkali
swelling is largely obviated, the Mg (OH) 2 precipitate is
converted into a soluble magnesium salt. Apparently all the
Mg(OH)2 still present in the hide after deliming is converted
back to a soluble magnesium salt during the pickling. An
incidental advantage of magnesium sulfate and chloride is that
they are two very cheap products.
"When deliming was carried out with magnesium salts plus acid,
instead of ammonium sulfate plus acid, the researchers found:
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1. The visual characteristics of the leather were not
adversely affected.
2. The most important physical characteristics were
affected not at all or very slightly.
3. The nitrogen (TKN) content of the wastewater was
significantly reduced.
4. The total processing time was not affected.
"In addition, with the same final pH after chrome tanning,
followed by the same processing methods, the ash content of the
leather in both cases would be equal."
Koopman states that commercial deliming products can be used for
deliming light leathers (thin hides); however, for deliming of thicker
leathers, the producers recommend only the products containing
nitrogen compounds in the form of ammonia or amine. Koopman describes
some of the factors or conditions which determine the required amount
of a particular deliming agent:
1. The alkalinity of the hide, which is connected with the
method of liming;
2. The degree of deliming desired;
3. The course of the rinsing processes after the liming and
preceding the deliming;
U. The thickness of the hide;
5. The time at which mechanical operations, such as fleshing
and splitting, are performed, with or without removal of
lime adhering to the flesh side;
6. The desired deliming time.
Koopman concludes his research with the following remarks:
"It has been found that in the deliming of leather, magnesium
sulfate shows definite promise as a replacement for ammonium
sulfate. Magnesium sulfate does not have a deleterious effect on
the quality of the leather, either as regards visual
characteristics or as regards the principal strength and stretch
characteristics. Like ammonium sulfate, magnesium sulfate
permits complete and rapid deliming and acid swelling does not
occur during the deliming.
"Magnesium sulfate (Epsom salts) is a cheap deliming agent; as
compared with ammonium sulfate, the quality of the effluent water
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is distinctly improved by its use. The replacement of ammonium
sulfate by magnesium sulfate in deliming can, under specified
conditions, lead to a definite reduction in the estimated
purification costs.
"Tests on a semi-industrial scale using magnesium sulfate as the
deliming agent have given, in all respects, favorable results.
It would be a logical continuation to now increase the scale, and
conduct one or more practical industrial-scale tests. In
addition to magnesium sulfate, the use of magnesium chloride,
which is also cheap, might merit consideration."50
This information suggests that deliming with epsom salts should
realize a 67 percent reduction in the ammonia content of the total
tannery effluent. This percent reduction was based upon engineering
analysis of data from plant no. 431 (Table 19) on the amount of
aqueous ammonia which would be removed from the segregated tanning,
retanning, wet finishing waste stream by complete removal of ammonia
from deliming. Since ammonia is also measured as TKN, a concurrent
reduction of TKN is achieved.
Summary of Industry Efforts to Implement In-Piant Controls
Table 21 lists some feasible in-plant process change methods and
indicates the number of tanneries which have considered and decided
either positively or negatively to implement these in-plant changes.
Sulfide substitution and elimination of bating were widely considered
but the tanners found no solution which, in their experience, did not
interfere with leather quality. Fourteen tanners considered a
substitute for ammonium sulfate and one tannery (no. 397) has used
magnesium sulfate in deliming with a considerable reduction in
nitrogen waste load.
As indicated in the table, opinion is almost equally divided on the
use of hide processors and also almost equally divided on lime and
unhair liquor reuse. Some tanners state that the leather produced in
hide processors is of poorer quality, while others state that the
leather is of better quality and the hide processors improve in-plant
control. Some tanners think that hide processors are more economical
because less labor is required and lower water use results. Others
object to the cost of installation and problems of maintenance.
In lime and unhair liquor reuse the question focuses on labor and
materials savings, lower waste load and questionable leather quality.
Several of the responses recorded on Table 21 in the negative column
included comments which indicated that decisions are still pending and
that further studies are being conducted.
Decisions on protein recovery apparently depend on the economic
situation of each tannery. The important question involves the
volume, quality, and the market for recoverable protein. Reuse or
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TABLE 21 IN PLANT PROCESS CHANGES INDICATED
ON QUESTIONNAIRE FROM TOTAL OF 46
LEATHER TANNERIES
PROCESS CHANGE METHODS
Sulfide substitute in unhairing
Ammonium sulfate substitute in
deliming
Eliminate the bating step
Use of hide processors
Wash/soak water reuse
Lime liquor reuse
Unhairing liquor reuse
Protein recovery
Spent chrome liquor reuse
Liritan vegetable tan process
Recovery of spent vegetable tan
liquor
Process or equipment wash water
reuse
Cooling water reuse
Other
NUMBER OF PLANTS
WHICH CONSIDERED
BUT DECIDED AGAINST
PROCESS CHANGES
17
12
12
14
15
12
8
6
19
5
NUMBER OF PLANTS
WHICH ARE OR WILL
BE IMPLEMENTING
PROCESS CHANGES
0
2
0
13
7
13
10
3
10
5
8
13
14
5
148
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recovery of tan liquors is generally an economic question with most
decisions indicated on that basis. From the questionnaires it also
appears that wash water and cooling water reuse is usually implemented
if convenient and if the tanner perceives some real benefit from such
an investment.
Table 22 lists the more commonly used waste stream segregation methods
and the number of tanneries reporting the use of these methods. Of
the 46 plants whose input was included on the table, nearly half
indicate using one or more of the listed beamhouse or tanyard waste
segregation methods. Nearly half also indicate using one or more of
the waste stream segregation methods for specific tannery processes.
Tanners generally concede the value of segregating certain process
streams for reuse of process liquor, for process chemical recovery,
and for more efficient treatment of final wastewater. However, it is
also apparent that stream segregation must be tailored to the
individual tannery situation. Some tanners do not consider their
facilities readily adaptable to such renovations due to either limited
space or the type of construction employed in the original building.
Floor and sewer construction methods are also mentioned as being
particular problems.
It is quite evident that many of these in-plant technologies are well
established and that a different cost situation (e.g., the cost of
ammonia removal by treatment versus elimination by substituting
chemicals) will motivate tanners to further implement these pollution
control methods. As the cost of processing chemicals and POTW cost
recovery and operating charges increase, the cost-effectiveness for
many of these in-plant control technologies will also become more
attractive. Chrome recovery is an excellent example of the cost of
processing chemicals making recovery economically attractive as well
as environmentally sound.
END-OF-PIPE TREATMENT
Preliminary Treatment - LEVEL 2
The need for preliminary treatment or pretreatment is based on the
following factors:
1. Removal of toxic pollutants found to pass inadequately
treated through a POTW.
2. Removal of causes of treatment system upset or hazards and of
collection system obstructions or potentially damaging materials.
3. Stringent water quality criteria imposed upon POTW in NPDES
permits.
4. Reduction of load to secondary treatment units.
149
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TABLE 22 WASTE STREAM SEGREGATION IN LEATHER-
TANNERIES AS REPORTED IN QUESTIONNAIRES
FROM 46 PLANTS
NUMBER OF TANNERS NUMBER OF TANNERS
WHO INDICATED WHO INDICATED
USE OF SPECIFIC USE OF SPECIFIC
BEAMHOUSE AND PROCESS WASTE
METHOD OF WASTE STREAM TANYARD WASTE STREAM SEGREGATION
SEGREGATION SEGREGATION METHODS METHODS
Total number of plants reporting
use of one or more of the 20 20
following methods
~"~~~~~"~~"~~~~~-~———————-—•—————————____________ __________ _ ________ _
Below grade separate sewers
or piping 16 9
Above grade separate sewers
or piping 10 9
Diverters 13 g
Collection trough 10 10
Concentric bearings 4
Isolate specific process steps - 9
Collect specific wastewater - 13
Other 3 5
150
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5. Sludge disposal criteria.
Tannery effluents exhibit a wide range of pollutants and pollutant
concentrations. Suspended solids vary from 300 to 14,000 mg/1 with an
average of 2,000-3,000 mg/1.30 5l The BOD5 of tannery effluents can
vary from 150 mg/1 to 3,000 mg/1, with an average of 1,000 to 2,000
mg/1.30 Grease concentrations in tannery waste can be as high as 850
mg/1. Sulfide and chromium concentrations also show a wide variation
in raw wastes. Normal concentrations of lime and chromium salts do
not appear to damage the system; short-term high concentrations could
be detrimental to biological activity. High alkalinity and
corresponding high pH are caused by lime discharges from beamhouse
operations. Such discharges normally are intermittent. Trivalent
chrome is used extensively as a tanning agent and hexavalent chrome
may appear in trace amounts. Trivalent chromium salts are soluble in
acid and neutral solutions. For wastewaters with pH in the range of
8.0 to 10.0, trivalent chromium hydroxides are highly insoluble, in
the range of 0.5 mg/1 or less, and will precipitate readily in primary
clarifiers.
Preliminary treatment operations consist of one or combinations of the
following operations and processes:
1. screening;
2. equalization;
3. sulfide oxidation;
4. carbonation of beamhouse wastewaters; and/or
5. ammonia nitrogen removal.
Screening. Fine screening removes hair particles, wool, fleshings,
hide trimmings, and other large-scale particulates. While reducing
undesirable wastewater constituents, screening contributes to the
volume of solid waste which must be disposed. The highly putrescible
wastes are commonly disposed of on-site or at remote landfill
operations.
Screening equipment includes coarse screens (bar screens) and fine
screens, either permanently mounted or rotating with self-cleaning
mechanisms. An example is the three-slope static screen made of
specially curved wires using the Coanda or wall attachment phenomenon
to withdraw the fluid from the under layer of a slurry which is
stratified by controlled velocity over the screen. This method has
been found to be highly effective in handling slurries containing
fatty or sticky fibrous suspended matter53 and is in use in the
leather tanning industry.
The principal function of screening is to remove objectionable
material which has a potential for damaging plant equipment and
clogging pumps or sewers. To date, much of the screening employed in
this industry has not been effective due to poorly operated screens,
or screens with openings that were too large, or both. This has
151
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resulted in continuing operational problems, such as clogging of
pumps, binding of clarifier sludge rakes, and so on. Therefore
effective fine screening is essential in all cases.
Equalization. Equalization of waste streams is important in
pretreatment facilities. The batch nature of tannery operations
creates wide fluctuations in waste flows and waste strengths. Such
variations can be difficult to handle and may result in over- or
under-design of the preliminary and secondary treatment units. The
volume and strength of waste liquors vary depending on process
formulations and scheduling of tannery operations. Alkaline wastes
are associated with beamhouse operations, while acid discharges arise
from the tanyard. In order to produce optimum results in subsequent
treatment operations, the equalization of flow, strength, and pH of
strong liquors may be necessary. Although some oxidation may occur,
no removal of waste constituents is normally reported for
equalization. Equalization basins provide storage capacity for
hydraulic balance. Auxiliary equipment must provide for mixing and
maintaining aerobic conditions. Detention times should be determined
based upon the wastewater generation patterns of the tannery and the
requirements of the secondary treatment facility. Typically these
patterns run in 24-hour cycles. In addition, most tanneries do not
operate more than 5.5 or 6 days per week. Where a POTW does not
receive sufficient wastewater to maintain an active biomass in a
activated sludge plant, additional hydraulic equalization capacity may
be necessary to carry the plant until the tannery resumes production
Basins can be monitored through pH and flow measurement.
An equalization tank or basin is usually fairly large and is most
economical at low ratios of height to surface area; size is mainly
subject to the fact that effective biological treatment requires
retention of wastewater heat. Tanneries with insufficient space for
such a tank have another option. This option, in use by at least one
tannery, is to schedule wastewater dumps from the tanning facilities
according to a wastewater discharge schedule that is designed to
smooth the hydraulic loading on the POTW. When scheduling of dumps is
combined with equalization tankage providing less than 24 hour
detention time, significant improvement in the performance of
subsequent treatment processes is obtained.
Sulfide Oxidation. Sulfides in the beamhouse waste constitute a
potential problem because they will release hydrogen sulfide if mixed
with wastes which can reduce the pH of the sulfide-bearing waste.
The removal of sulfides is not accomplished with plain sedimentation.
Sulfides are more satisfactorily removed through oxidation. Various
methods for oxidizing sulfides include:
1. air oxidation;
2. direct chemical oxidation;54
3. catalytic air oxidation.54 55 s*
152
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Air oxidation with diffusers provides some removal, but only with
excessive aeration times.
Direct chemical oxidation with ammonium persulfate and ozone was
studied by Eye and Clement.5* Ammonium persulfate produced low
removals. Ozone was most effective; however, the expense of ozone-
generating facilities and developing contact equipment negated further
study.54
Studies by Chen and Morris56 revealed that many metallic salts are
effective catalysts when compressed air at high temperatures is
utilized. Manganous sulfate was the most effective catalyst in the
more alkaline solutions at near-ambient temperatures. Nickel, cobalt,
and manganous ions also are effective, and potassium permanganate is
predicted to work well.5* Their best formulations achieve complete
removal with contact times as short as 15 minutes.
Kessic and Thomsom57 obtained 95 to 97 percent oxidation of sulfides
at contact times of approximately 20 minutes using manganous ion as
the catalyst. These solutions were very dilute and achieved residual
sulfide levels between 0.3 and 1.0 mg/1. In two studies, Ueno58 5«
obtained between 92 and 100 percent sulfide oxidation using high
temperatures, great excesses of air and many different catalyst
systems. Among those found to give good results were ferric sulfate,
ferric chloride, activated carbon, carbon black, ammonium
peroxydisulfate, and hydroquinone.
Eye and Clement5* found that potassium permanganate plus air, ozone,
or manganous sulfate plus air could remove sulfides completely with
contact times between 3 and 30 minutes. In this study a first-stage
(continuous) flow reactor removed 80 percent of the sulfide, and a
second-stage batch reactor removed the rest. An actual tannery waste
required 1.5 hours of treatment with potassium permanganate and air.
Bailey55 and Eye5* further describe the effectiveness of the metallic
catalysts. In a laboratory study54, potassium permanganate was the
most effective agent, with manganous sulfate also proving effective.
Although the relative costs for the two catalysts favor manganous
sulfate, the available space and capital costs for the two different
systems will determine which catalyst is the best for a given
situation. Optimum results were obtained with a manganese to sulfide
weight ratio of 0.15. Pretreatment facilities employing catalytic
oxidation should approach 100 percent removal of sulfides.
Available information indicates that the catalytic oxidation process
can be designed to remove all dissolved sulfides. However, residual
sulfur forms, which are chemically bound to organic matter in the
wastewater and therefore not removed by this catalytic oxidation
process, can be subsequently redissolved in significant quantities.
This reappearance of sulfide could easily occur in a long sewer
collection system. Further, alternative sulfide control systems, such
as spent liquor reuse, will remove the majority of sulfides, but will
153
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not completely remove sulfides without the addition of catalytic
oxidation. Sulfide recovery has been demonstrated at full scale at
Once received in secondary treatment facilities, sulfides are largely
removed. However, in order to minimize dangers of potential hydrogen
sulfide release and to eliminate the immediate oxygen demand exerted
in subsequent biological processes, a catalytic oxidation process is
necessary for tanneries with sulfide-bearing wastes.
Catalytic sulfide oxidation can achieve complete removal (not
detected) of sulfide. Sulfide liquor reuse or sulfide recovery (as in
Tannery No. 444) would assist in removal and provide economic return-
however, it is generally considered an optional measure to achievement
of complete removal of sulfides.
Carbonation of Beamhouse Waste Stream. Carbonation is effective in
the treatment of alkaline wastes. In this process, carbon dioxide
reacts with lime to form calcium carbonate, which has a solubility of
only 25 to 50 mg/1. The crystalline structure of the carbonate
nucleus provides an effective surface for adsorption of organic
matter. Suspended solids and BOD5 are both reduced. Inorganic
suspended solids in the form of calcium carbonate are significantly
reduced and thus reduce excessive alkalinity, which in turn reduce
mixing requirements in activated sludge aeration basins and secondary
sludge production and dewatering requirements.
Four U.S. tanneries (numbers 60, 24, 58, 397) have operated flue gas
or carbon dioxide Carbonation. This technology is used instead of a
strong acid, such as sulfuric acid, to reduce the pH of the highly
alkaline waste streams from the beamhouse operations. Such DH
reduction can be done for a variety of reasons, such as to precipitate
excess lime, to neutralize the waste stream, and to provide sufficient
PH reduction to allow a substantial degree of protein precipitation.
Substantial operating cost savings can be realized by exchanging the
cost of acid for the cost of electrical power to operate thl
Carbonation system, primarily the blower.
Stack gas containing 8 to 12 percent carbon dioxide, obtained from any
fuel combustion process, can be used. Introduction of gas into the
waste stream requires a suitable diffuser system and reaction vessel
and continuous operation of the boilers.
Table 26 indicates removals of suspended solids and BOD5 for
carbonation in conjunction with coagulation to remove dissolved
proteins and excess lime. The BOD5 removals range from 65 to 92
percent, while suspended solids reductions from 79 to 99 percent are
recorded. t^*^cnu axe
Field data from tannery no. 24 indicate high reductions in suspended
solids, BOD5, and total alkalinity. Estimated flows from the
154
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cattlehide vegetable tannery were 1,700 m3/day (0.45 mgd) . Primary
clarifier overflow rates were about 20.4 m3/day/m2 (500 gpd/ft2) for a
chemical system utilizing flue gas carbonation and a combination of
iron salts and polymers. (Sulfuric acid was also used to assist pH
control). Table 23 presents the removals which were indicated60:
Table 23
Performance of Flue Gas Carbonation and Chemical Coagulation
Pollutant
Paramater Influent (mq/1) Effluent (mq/1) % Removal
Suspended 2,110 100 95
Solids
BOD5 1,660 270 84
Total Alkalinity 640 0 100
(as CaCQ3)
Carbonation is attractive for tannery pretreatment facilities, where
carbon dioxide is available at the cost of piping from the plant
boilers. Removals are high, under proper operating conditions, for
suspended solids and BODJ5.
In some instances, pH control is a necessary adjunct to equalization
for effective removal of chromium, prevention of sulfide gas
evolution, and enhancement of the protein/lime precipitation process.
Normally, this has been accomplished by feeding sulfuric acid, lime or
sodium hydroxide to lower or raise pH as required. This requires
chemical feeding equipment with a pH sensing and control system.
Pumping equipment also may be required where tankage or gravity flow
constraints exist.
To reduce COD, BOD, nitrogen, dissolved solids, and suspended solids
from the beamhouse waste stream, various methods of protein recovery
have been successfully demonstrated in tannery unhairing wastes. A
typical spent unhairing liquid from a hide processor run contains
about 8,000 to 9,000 mg/1 of TKN, most of which is contributed by the
denatured hide proteins. Likewise, the total volatile solids
concentration of 51,000 mg/1 (of which 30,000 mg/1 are volatile
suspended solids and 21,000 mg/1 are volatile dissolved solids)
reflects the extremely high protein decomposition.
Happich, et al.,61 demonstrated that a recovery scheme employing:
removal of suspended solids by gravity sedimentation, screening,
centrifugation and/or filtration; removal of soluble inorganic
compounds by dialysis or ultrafiltration; acidification with acetic
acid to pH 5.0 and 3.8; and washing and drying; yields a protein
fraction of 90 to 92 percent purity. These results were obtained from
lime sulfide hair pulping effluent samples from five unidentified
155
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side-leather tanneries which use the high-sulfide, hair pulping
process. First, catalytic oxidation of the sulfide liquor removed the
sulfides; this was followed by acidification. Acid precipitation to a
pH of 4.0 gave the best yield. Sulfuric acid has also been used to
precipitate the proteins, as have chrome or pickle liquors. However,
care must be taken to avoid the toxic effects of chromium in the
protein sources, if the by-product is intended for the feed industry.
Happich reported that approximately 30 percent of the COD (37 percent
of BOD5) present in the untreated hair-burn waste was separated in the
solids fraction after a two-stage centrifugation. Another 31.5
percent of the COD (34.9 percent of the BOD5) ultrafiltration
transferred to the filtrate, and 38.5 percent of the COD (28.1 percent
of the BOD5) was actually removed with the protein. According to
Happich, effluent COD decreased by 70 percent and 65 percent of the
protein in the effluent was recovered. The product could be purified
to 90 percent protein by reprecipitation. The amino acid composition
did not differ significantly from the protein recovered from un-
oxidized lime-sulfide unhairing effluent.
Happich noted that the recovered protein contained the hair. He
concluded, however, that the recovered hair protein was low in most of
the amino acids found in whole egg protein and would require some
supplementation for subsequent use as feed (typically for chickens).
Once properly supplemented, autoclaved cattie-hair has proven to be a
satisfactory source of protein for feed formulations. If no market
for feed formulas exists near a tannery, however, the protein sludge
may be dewatered on a gravel bed filter and sold as fertilizer or
taken to a landfill site for disposal.
Van Meer experimentally tested segregation of specific process streams
for reuse or treatment.*2 Wastewater volume and COD and nitrogen
loading were substantially reduced, the former to 3-4 I/kg hide and
COD and nitrogen from this source by 89 and 90 percent, respectively
This method carries out the unhairing in the first soaking liquor or
in a separate short float. The initial wastewater treatment consists
of catalytic oxidation of the sulfides with manganese sulfate and
aeration. This is followed by acidification with sulfuric acid and
sodium chloride to pH 4.0 and precipitation of the proteins. The
resulting sludge is then either dried on a gravel bed or filtered from
the effluent in a sand filter. The recovered sludge can be used as a
fertilizer or feed source. The COD and TKN in the combined soaking,
unhairing and wash liquors after acidification, were reportedly
reduced 84 and 86 percent, respectively.
A leather tannery waste management studya* conducted under an EPA
grant in tannery no. 431 reported on experiments in the recovery of
crude protein from unhairing liquors:
"To determine the degree of effluent reduction possible through
protein recovery from manganese catalyzed, air-oxidized unhairing
156
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wastes, a sample of oxidized waste from an early.«.paddle
aeration run was sent to the U.S. Department of Agriculture
Eastern Regional Research Center in Philadelphia for protein
recovery by a modified treatment scheme. Precipitation by
acidification of the sample to pH 4.2 yielded a tan color protein
of 80% purity.
"Another bench-scale experiment was conducted...to further define
the conditions for optimum precipitation of protein and
subsequent reduction of contaminant levels.
"Concentrated hair-burn liquor was air-oxidized using manganese
sulfate as the catalyst, at a Mn++/S= ratio of 0.15. After
oxidation, the liquor contained approximately 160,000 mg/1 of
total solids, of which 58,400 mg/1 was suspended solids.
"Varying levels of concentrated H2SQ4...were added to eighteen
500 ml aliquots of the oxidized waste. The samples were mixed
using a Phipps and Bird laboratory stirrer for 5 minutes at 100
rpm followed by 5 minutes of "slow" mixing at 50 rpm. After
settling for 60 minutes, the supernatant liquids were decanted
and analyzed for pH, total solids and suspended solids. The
pH(s, which varied from 0.3 to 9.4, were consistently higher than
the expected values. This is most likely due to the times
elapsed in the precipitation runs contrasted to the 10-15 minutes
required for the original titration. While there is no apparent
relationship between supernatant pH and suspended solids
(supernatant suspended solids concentrations were consistently
within the 280-630 mg/1 range except at pH 9.4 where a markedly
increased level of 1,670 mg/1 was observed) the optimum for
reduction of total solids (was found to be)...within the 0.9 to
5.0 pH range.
"The volumes of the resultant sludges varied from 300 ml to 475
ml with the minimum lying within the 1.0 to 3.9 pH range.
Fortunately, this range of minimum sludge volume is also within
the optimum range for precipitation of protein.
"At pH 3.2, the supernatant analyzed at 100,200 mg/1 of total
solids (minimum observed for 18 runs) and 401 mg/1 of suspended
solids. Thus, approximately 75% of the total solids and 99.7% of
the suspended solids present in the original, air-oxidized waste
sample were transferred to the 300 ml sludge fraction after
precipitation and settling.
"Undoubtedly, further sludge dewatering will be required to
concentrate those solids which occupied 60% of the original
sample volume. Since a portion of the sludge (which contained
approximately 80% moisture) dewatered readily by gravity on a 18-
mesh screen, dewatering methods recommended for further
investigation include gravity screening and sand bed filtration.
157
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Lab-scale attempts at vacuum filtration failed to generate a firm
cake indicating that conventional rotary vacuum drum filtration
is not a feasible alternative. As indicated (previously) these
concentrated hair-burn liquors comprise only a small fraction of
the total wastewater flow (i.e. , approximately 11,700 gal hair-
burn liquor vs approximately 1.5 million gal total daily flow)
yet contribute substantially to pollutant loadings. Therefore
it appears from these results that precipitation of crude protein
from oxidized unhairing wastes can effect significant reductions
in total plant loadings provided adequate methods of sludoe
dewatering and disposal can be demonstrated."
The effectiveness of flue gas carbonation of beamhouse waste streams
is optimal when the PH is lowered to the isoelectric point. when
limited to only the introduction of flue gas, the treatment
lu of ^!neSS t^1S g?05;ess wil1 not be ^ great since the operating
PH of the process is higher than the isoelectric point. Removal
efficiencies were conservatively selected to represent expected
performance in this industry, as follows: BODS - 60 percent, where
removals as high as 84 percent were noted ;~TSS - 65 percent, where
removals higher than 95 percent were noted; COD - 60 percent where
removals of as high as 90 percent or more were noted; oil and grease -
and TKN - 65 percent- where
Nitrogen Reduction. Ammonia is difficult to remove from
tannery wastewaters. Biological systems which remove BOD have not
seen effective in removing ammonia. For this level of treatment. EPA
wastes"^ ohvsi^T aite?na*i ves for removing ammonia from Seiimfng
wastes by physical-chemical treatment processes. The ammonia
introduced into the tannery wastewater stream by the deliming process
ranges from 67 to 90 percent of all the ammonia in the raw waste
str!amSUwflf ^^f* ^^ °l treatment °f this ammonia containing
wastewat« " " *
These processes assure that the primary ammonia containing stream is
«H£f9aJ:ed and vte ammonia removed before it is combined with other
waste streams. The segregated ammonia containing stream has a hiaher
concentration of ammonia than a combined stream, and it is therefore
t0 treat by Physical-chemical methods. Th4 methods consilerel
1. water evaporation followed by crystallization
precipitation of ammonium sulfate;
2. distillation of ammonia;
3. precipitation of ammonia as calcium ammonium phosphate;
or
158
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4. precipitation of ammonium sulfate by addition of ethanol;
5. reverse osmosis; and
6. ion exchange.
No tannery now uses these methods for treating ammonia wastes.
Several of them are technologies used in other industries while others
should work because of known chemical principles. Use of alternate
deliming agents has been discussed in the In-Plant Control portion of
this Section.
Evaporation/Crystallization
Evaporation plus precipitation is a well-known technology and is
used to prepare many solid chemical products from aqueous and
organic solutions. This technique evaporates water from the
deliming waste until the ammonium sulfate concentrates
approximately at the saturation value. The ammonium sulfate is
then crystallized by cooling the solution and removing an
additional small amount of water by applying a vacuum. One
disadvantage of this process is that relatively large amounts of
water must be evaporated. For example, if the segregated stream
contains 1 percent ammonium sulfate, then the concentration of
this stream to the saturation point of about 50 percent requires
evaporation of about 98 percent of the stream. The evaporated
water will contain about 0.2 percent ammonium sulfate if the
evaporation occurs at about 95°C. Thus, the percent of the
ammonium sulfate removed will range from 60 percent if the
original concentration was 0.5 percent to 90 percent if the
original concentration was 2 percent. Energy costs are a
significant limit on this process,
Distillation
Distillation is well-known and widely practiced. If one
component of a mixture has a higher vapor pressure than the
others at a certain temperature then boiling the mixture at this
temperature will concentrate the more volatile component in the
vapor phase. Addition of a strong base to deliming waste will
convert most of the ammonium sulfate to free ammonia, which is
much more volatile than water. At 25°C ammonia is so much more
volatile than water that removal of 90 percent of the ammonia
requires evaporating only 8.5 percent of the water; removal of 99
percent of the ammonia requires evaporating only 16.3 percent of
the water. It is important to distill at the lowest possible
temperature because the relative volatility of ammonia compared
to water decreases as the temperature increases. A disadvantage
and serious limitation in this method is that the ammonia cannot
be economically recovered after distillation and must be vented
159
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into the atmosphere, causing unacceptable odor and consequent air
pollution problmes.
Precipitation with Phosphate
The fact that calcium ammonium sulfate is insoluble in water is
the basis for predicting the possibility of precipitating ammonia
with phosphoric acid if the proper amount of lime is present.
The insolubility of the calcium ammonium sulfate salt causes
difficulties in the production of the fertilizer ammonium
phosphate. It is possible that excess lime would cause an
increase in the cost of this process. Calcium phosphate is not
very soluble in water and would precipitate from solutions
containing lime and phosphoric acid. It may thus be necessary to
precipitate excess lime by flue gas carbonation before attempting
to remove the ammonia with phosphoric acid.
Precipitation with Ethanol
Ammonium sulfate is insoluble in solutions of ethanol and water
if the ethanol concentration is more than approximately 90
percent. Thus, it is possible to predict that ammonium sulfate
can be precipitated from water by adding nine parts by weight of
ethanol to each part of ammonium sulfate solution. The cost of
ethanol, however, precludes further consideration.
Reverse osmosis
Reverse osmosis can concentrate aqueous solutions of salts. A
cellulose acetate membrane suitable for producing fresh water
from seawater or brackish water would be suitable also for
concentrating aqueous ammonium sulfate. Free ammonia would
probably go through such a membrane. Pressure requirements are
the main limitation on how much the ammonium sulfate solution can
be concentrated. Concentration to even 5 percent would require
the use of several hundred psi. Fouling could also be a serious
problem. Cost and process limitations preclude this from further
consideration.
Ion Exchange
Ion exchange has been used to remove small amounts of impurities
from water. To remove ammonium ion, exchange with an acid is
necessary. Suitable resins exist, but again fouling could be a
serious problem which, along with cost, minimizes the potential
for application of this process.
160
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Primary Treatment
Plain sedimentatipn. Plain sedimentation is concerned with the
removal of non- flocculating discrete particles and flotable low-
density materials such as grease and scum. Tannery wastes have high
concentrations of both suspended solids and grease. As shown in Table
oercentPend.hdi S°U^ r?ductions c™ «nge from approximately \0 to 90
Mnoh ^Kv, l6 rfductlons in BOD5 can range from 30 to 60 percent.
Much of the suspended material removed is in the form of insoluble
lime which produces a voluminous and heavy sludge? Although grease
removals are not indicated, high removals are expired wi?h surf acl
skimmers installed in clarifiers. surtace
Sutherland cites the operation of full-scale plain sedimentation
^"-entation reduced the suspended solids content of a side
*> 370
Laboratory experiments by Sproul, et al^* utilizing beamhouse and
chrome liquors showed that plain sedimentation at an overflow rate of
24.5 ma/day/m^ (600 gpd/ft*) gave average removals of about 22 percent
of suspended solids and 35 percent of BODS. Pilot scale experiments
by sproul, et a^" show that equalization of plant flows fol lowed bv
ln ed* gaVe sus?ended solids and BOD5 removals up to 99
nd50 ~
o? i-h» * m? ' resPe=tlvely- Chrome liquors in excess of 1 percent
of the total flow proved to be an effective coagulant for comoosi^
or comoos
wastes containing 2,000 mg/1 suspended solids. Overflow rates^f If 3
m3/day/m3 (350 gpd/ft^) produced a 2 percent underflow concentration!
Field operations at tannery no. 237 tend to confirm these removals. 30
ratef^f^Tfl^ T^^^ tW° circular clarifiers with overflow
mt/IL ,0 8 £;5, m^day/ni% . ^6° gpd/ft^) at an average flow of 1,030
m /day (0.8 mgd) . NO equalization facilities are provided other than
mixing in a pump wet well. Cattlehide processing during the samolina
period averaged 81,700 kg (180,000 Ib) green- sal?ed and brine-cured
tan f /^ -da^ f°r hair pulp be^house operations followed by chrome
tan and finishing. The following average removals resulted^o
Table 25
Pollutant Removals by Plain Sedimentation at Tannery No. 237
Paramater Influent fmcr/1) Effliren* fr^/i]
Suspended Solids 3,125
2,108
Total Chromium 51
Total Alkalinity 980 /1H 0-
(as CaC03) 27
Grease 490 57 go
162
-------
Suspended solids and BODJ5 removals were 70 percent and 45 percent,
respectively. A low chromium removal of approximately 50 percent
occurred. Higher removals would result if a pH of 8.5 or greater were
maintained (using equalization or chemical addition) in the primary
clarifiers. If sodium alkali is contributing to the high pH, a pH of
10-10.5 may be needed for best removal. Theoretically, all chrome
should precipitate as chromic hydroxide; however, a very small residue
is expected. Although chrome removal from the wastewater is
desirable, it does create a sludge problem if proper disposal
precautions are not taken. Total alkalinity was reduced 27 percent,
reflecting sedimentation of suspended lime. Grease removal was 90
percent.
Coagulation -Sediment at ion. Chemical addition prior to sedimentation
of combined wastewater streams has further increased the removal
efficiencies of primary clarifiers. This is a key step in removal of
insoluble toxic pollutants, most importantly chromium. Chemical
coagulation results in higher removals of suspended solids, BODJ5,
sulfides, chrome, and alkalinity through flocculation of colloidal
particles. Alum, lime, iron salts, and polymers have exhibited
satisfactory results. Table 26 indicated that suspended solids
removals from 50 to above 98 percent and BOD.5 reductions of
approximately 50 to 99 percent are achieved.
Chemical coagulation followed by sedimentation has been applied at a
plant using the chrome tanning process.*4 Raw wastewater analyses
indicate concentrations of BOD5 at 2,500 mg/1 and suspended solids of
about 2,530 mg/1. The results drawn from the laboratory-scale
investigation were shown in Table 26. Other chemical coagulation
results were as follows:
1. Use of an anionic polymer at a concentration of 1 mg/1
resulted in a reduction of about 84 percent in suspended solids
and 60 percent in BODj>.
2. Adjustment of the waste to pH 9.0 with sulfuric acid and
subsequent settling gave average removals for suspended solids
and BODJ5 of 90 and 67 percent, respectively.
3. Use of ferric chloride at a concentration of 600 mg/1
produced average removals of 60 and 65 percent, respectively, for
suspended solids and
4. Ferric chloride coagulation was less effective in removal of
suspended solids than was adjustment to the same pH with sulfuric
acid.
5. Ferric chloride removes dissolved sulfides, but chemical
costs are high.
163
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6 Coagulation with alum at concentrations less than 500 mg/1
after adjusting to a pH of 6.5 reduced the BOD5 by 90 percent and
suspended solids from 45 to 57 percent. Alum concentrations
higher than 500 mg/1 created a floe that would not settle.
7. Buffing dust resulting from finishing tanned hides was not
found to be an effective coagulant.
In general, polymer addition produced a rapid formation of floe,
minimizing the need for flocculating equipment. Without pH
adjustment, polymers produced consistently higher removals than other
coagulants tested.
Sulfides appearing in the pretreatment influent are not completely
removed in chemical units. Inconsistent removals are indicated in the
literature by researchers.** 64 65 with pH adjustment to 8.0, an upper
limit on sulfide removal may be 90 percent.* « Sulfide removal reduces
oxygen demand and averts hydrogen sulfide problems.
Chromium will precipitate as a hydroxide most effectively at a pH of
approximately 8.5. A 90-percent removal in a laboratory study by
Sproul, et al.6* occurred at a pH of 8.0.
In pilot plant coagulation and sedimentation operations described by
Howalt and Cavett** and also by Riffenburg and Allison*^ 93 and 99
percent removals of color were observed, respectively.
A thesis by Hagan*8, investigated color removal through coagulation
and precipitation. In coagulation, inter-particle attraction created
by suitable polymer develops a large floe that tends to settle at an
optimum pH. Hagan also reported that the common-ion effect assisted
in precipitation removal. The basis of this contention is that the
hiqh hydroxyl ion concentration at high pH reduces the solubility of
color vectors such as digallic acid, which contains hydroxyl
functional groups. Addition of coagulants and pH control at this
point further increase the relative efficiency. Laboratory results on
a vegetable tannery waste indicate high color removals (94 percent)
through a combination of chemical precipitation and coagulation with
calcium hydroxide and an anionic polymer.*° The efficiency is
dependent on pH control around 12. Many low removal may have resulted
from inefficient control of the physical-chemical operations, ;:..ich
require operator attention to be successful.
Based upon the above performance data, the following removals are
considered achievable with the implementation of carefully operated
coagulation-sedimentation: BOD5 - 60 percent, where removals as high
as 85 percent were noted; TSS - 60 percent, where removals as high as
99 percent were noted. As noted in Table 26, removal efficiencies
greater than 90 percent have been noted but not used because of
dissimilarities in technology such as the use of two stage systems and
use of very high chemical dosages of costly chemicals, such as 5000
165
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HS™^~
"
"Secondary" Biological Treatment - LEVEL 4
As mentioned previously, preliminary treatment and primary treatment
£iiter Process. very few tanneries and some POTW's use
s use
A trickling filter is an aerobic biological unit. Wastewater
constituents are brought in contact with a microorganism mass
166
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developed on the surface of the filter media. To achieve high
removals from tannery effluents, toxicity and excessive organic loads
must be avoided. Lime deposition on filters also has, in some
instances, retarded biological activity. Also, the high strength of
tannery wastes requires the provision of a large surface area.
Although recirculation and improvements in filter media may reduce
overall area needs, waste load reduction may not be consistent
throughout the year to meet the demands of future effluent limitations
requirements. Temperature is critical in operation. High heat losses
can occur in the spray distribution system and across the bed media,
yielding low efficiencies. Populations of nitrifying organisms will
be suppressed by continual dosing of the system with carbonaceous
organic material.
Two tanneries in the southeast have indicated that they are using a
trickling filter or trickling filter-like system as one component in
their secondary treatment system. Tannery no. 400 uses a rock media
filter as the first stage in a two-stage biological system. This
tannery does not have an unhairing step. The purchased hides have
been previously unhaired and prefleshed. The tannery is a vegetable
tannery using the "Liritan" process. Data on the reduction of BOD5
and suspended solids across the trickling filter is not available.
Another southeastern tannery (no. 24) also uses a trickling filter as
the first stage in a two-stage biological system. Operational data
reported in 1972 indicated that the plastic media filter was
ineffective, with removals of less than 30 percent BOO5 and suspended
solids. Kinman*9 reported improved operation of the overall system by
cleaning the media and increasing the air supply to the filter.
Confirming data obtained in a recent field survey at Tannery no. 24
indicate that the trickling filter (oxidation tower), including
secondary clarification, has the combined performance characteristics
displayed in Table 27.
Table 27
Performance Characteristics of Trickling Filter Treatment
for Tannery Wastewaters
Influent to
Pollutant Trickling Filter
Parameter (mq/liter)
BOD5
Suspended Solids
COD
Total Kjeldahl
Nitrogen (as N)
Ammonia Nitrogen
(as N)
270
110
Effluent From
Clarifier
(mq/liter)
62
45
240
210
60
Removal
(percent)
77
59
167
-------
The flow to the filter was approximately 4,000 m3/day (1 mad)
con +- «*. 8»H>ended solids may not be possible due to the
colloidal characteristics of the suspended material and the relativelv
cUri?Ier "^ °f " m3/day/m2 <800 *><"«"> ^ thl secondary
Trickling filters have limited application in the treatment of high
ov3*rf tann"y w^tes. system upsets are common due to organic
overload and climatic conditions. Existing filters mav h«
system
tasasas. Lagoons, also referred to as oxidation ponds or
availaW* *%£*' ^ ^^ "sed for tannery treatment where land
available and where la
s availaW* n
is available and where land values are low enough to make laaoon
systems an economical alternative to activated sludge! LagoonI slrve
two purposes: egualization and the provision of a desirable
environment for biological activity. In a large lagoon with a
9
s 1 clarificationmay
whfi/h mU ti0n' however' can Deduce the efficiency to the poini
where it becomes necessary to construct a new lagoon or dredge the old
There are three types of lagoons based on the biological environment
that exists for the stabilization of organic wastes. These types are:
Aerobic Lagoon— Biological stabilization in the presence of
-SJSST sss.r-s
the dissolved oxygen content in the llgoonf
2. Anaerobic Lagoon— Biological stabilization in the absence of free
oxygen.
3. Aerobic/Anaerobic Lagoon— A stratified lagoon where aerobic
activity predominates near the surface and anaerobic activitv
takes place near the bottom of the lagoon. anae^ot)ic activity
em°n!trati0n at a tanner* in Virginia, Parker investigated
denitrification, as indicated b • '
ation, as indicated by reduction of KM •* '
168
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systems. The aerobic lagoon is followed by anaerobic treatment in
another lagoon to reduce the nitrate to nitrogen gas, which then
enters the atmosphere.
Thirteen tanneries surveyed presently treat their waste with lagoons,
either as pretreatment, major method, or finishing step to some other
system. Several tanneries indicated that lagoons are only a temporary
treatment while other more efficient systems are planned or being
built. Eleven of the thirteen tanners use mechanical aeration of
their aerobic or aerobic/anaerobic lagoons. Aeration increases
dissolved oxygen content and thereby reduces retention time or lagoon
size, which saves on land requirements. Four tanners have
aerobic/anaerobic lagoons while three others are equipped with multi-
stage aerobic and anaerobic lagoons. Nearly all (85 percent) provide
screening of wastewater and 38 percent are using plain sedimentation
or coagulation-sedimentation as a primary treatment before discharging
into lagoons. Several tanners reported adding phosphoric acid to
provide an adequate nutrient balance for effective biological
activity.
A major disadvantage of using aerobic lagoons to treat tannery wastes
is the decrease of efficiency during the winter months, especially in
the northern states. In addition, ice cover can inhibit aerobic
conditions. A northeastern tannery (no. 401) reported the data in
Table 28, which exemplifies the seasonal variation in effluent quality
from their lagoon system:
Table 28
Aerobic Lagoon Performance as a Function of Season
Pollutant Summer and Fall Winter and Spring
Paramter (mg/liter) (mq/liter)
BOD5 15 98
COD 176 398
TSS 19 85
Cr 0.7 3.5
Grease 26 43
TKN 39 65
Sulfide 0.2 O.JJ
This data typifies the shortcoming of aerated or aerobic lagoons for
treating leather tanning wastewater. The extensive surface area for
heat dissipation and the low solids (microbial population) content of
the lagoons precludes consistently good effluent quality during winter
months.
Anaerobic lagoons are usually covered to retain the heat so they are
less affected by low ambient temperatures. A scum layer of grease may
169
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accumulate on the surface to reduce heat loss and ensure anaerobic
conditions. Polyvinyl chloride, Hypalon^, and styrofoamj, have been
used to cover anaerobic lagoons to retain heat, control odor, and in a
few cases to attempt collection of methane gas. For optimum
ohnn?r£n0!; *? K^ redUSe °d°r Production, the PH of anaerobic lagoons
should be kept between 7.0 and 8.5. Anaerobic lagoons are used by the
method indU3try as One part of a system and not as the sole treatment
Under the proper biological conditions, i.e., pH control, sufficient
nutrients, etc., and with long retention times (usually requiring
large amounts of land in relation to plant size), lagoons can provide
consistent effluent quality in warmer climates. Land values and
alternate^ *?**? ^^ lag°°nS *** m°re economical than
alternate treatment systems. In colder climates winter operation can
never approach summer treatment efficiency, unless they utilize costly
covers, or the system has sufficient storage capacity to hold several
months discharge.
Activated Sludge Systems. The activated sludge process is one of the
most controllable and flexible of all secondary treatment systems. It
is applicable to almost all treatment situations and plays a very
important role in this industry for treatment of toxic pollutants?
With proper design and operation, high organic removals are possible
Designs based on solids retention time (SET) afford optimum residence
time for solids with minimal hydraulic retention. However, pilot
studies are required to establish appropriate design parameters
wastewaLr rel*tive rate °f biological growth and decay wiL a given
Basically, the activated sludge process consists of: mixing of
returned activated sludge with the waste to be treated; aeration and
separation of the activated sludge from the mixed liquor and disposal
?n™ excess. sludge. Activated sludge is typically preceded by some
form of primary treatment, especially in tannery applications
ovf^tnn ln P2^6**™:1^ may include the use of equalization, sulfide
some* form'of SSe^^' ***™™^™ or clarification, and
Based on the influent and effluent data from samples collected and
analyzed during this program, BCD5 removal varied from 89 to 98
fromenQO ?oaCQ«Vated Sludge Svstems' Suspended solids removal ranged
from 90 to 98 percent. BOD5 measurements of filtered samples
indicated the significance of solids removal and hence the import an ce
of the size and design parameters for the final clarifier. Successful
.
of r?a.?n f the activated <*«** treatment system depends on a number
of factors such as: continuity and uniformity of feed by means of
equalization whether provided by a separate equalization tank or by
the design of the aeration basin, maintenance of nutrient balance and
high mixed liquor solids in the aeration basin, and linal
170
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clarification designed for very low overflow rates for removal of
suspended solids.
Tannery no. 237 in Minnesota has initiated full activated sludge
operations for an estimated 3,600 m3/day (0.95 mgd) flow from a chrome
tanning, hair pulp facility with finishing operations. The project
was partially financed through an Environmental Protection Agency
grant. The system at Tannery No. 237 uses screening, plain
sedimentation, activated sludge, final clarification and sludge
filtering.
The combined tannery flows are screened, then pumped to dual plain
sedimentation basins. The 12-m (40-ft) diameter clarifiers are
equipped with surface skimmers. Four concrete lined lagoons are used
as activated sludge aeration basins. Each lagoon has a capacity of
3,875 m3 (1 mil. gal.) at 1.8 m (6 ft) operating depth, which may vary
in operation. Three lagoons are operated in parallel and the fourth
lagoon functions as a sludge digester. An aeration capacity of 60 hp
per lagoon was installed. Return sludge design permits recycle to
each lagoon as well as ahead of the primary clarifiers. Aeration and
digestion are followed by final sedimentation in two 12-m (40-ft)
diameter clarifiers. The effluent is chlorinated prior to discharge
to a nearby watercourse. Primary sludge and waste activated sludge
are dewatered in a pressure filter and landfilled on-site. Automatic
samplers permit monitoring of individual treatment units to ensure
better operational control.
Data for this activated sludge system at plant no. 237 shows more than
90 percent removal of BODj> in the summer months and 90 percent removal
of suspended solids (final effluent BOD_5 concentrations ranged from as
low as 8 mg/1 to as high as 489 mg/1); EOD5 and suspended solids
removal decrease somewhat in the winter. Wintertime removal
efficiencies are: BODj>—89 percent; suspended solids—88 percent.
EPA believes that these results do not accurately reflect the
achievable final effluent concentrations (i.e., BODji> and TSS) of
activated sludge systems since a number of design and operational
factors contributed to poor performance, such as lack of equalization,
very shallow aeration basins with inadequate mixing, under designed
secondary clarifiers, frequent changes in experimental mode of
operation, presence of significant quantities of sulfides from primary
treatment, and other factors.
EPA evaluated a full-scale activated sludge plant in a Kentucky
tannery (No. 47) in a two-week study. This tannery is a cattlehide
tannery with pulp hair beamhouse operations and alum tanning with some
chrome and vegetable tanning. At the time of the study, flow was 61
m3/day (0.016 mgd). The treatment system consists of screening,
primary clarification, extended aeration activated sludge, and
secondary clarification. Primary treatment includes a rotating,
coarse screen followed by fine screening and 24-hour equalization.
Overflow rates of 13.6 and 13.4 m3/day/m2 (290 and 285 gpd/ft2) were
171
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observed in primary and secondary clarifiers, respectively. Hydraulic
detention time averaged 1.6 days in the aeration basin. "unc
Additional data from sixty months of operation indicate long-term
average effluent performance in the range of 60 mg/1 of BODS and 95
mg/1 of TSS. Variability showed no seasonal influence, but rather the
influence of equipment failures or shock waste loads! This is
f^TV • significant since all system equipment is located in a
flood plain and is therefore above ground and exposed to the elements
thus exacerbating the potential for temperature influence. eieinen1:s*
An activated sludge facility in New York (tannery no. 320) is
finisM™ ^a^nl ?ffluent f*om a save hair beamhouse, chrome tan,
finishing, and rendering operations. Total wastewater from thes4
processes is about 1500 m3/day (0.4 mgd). Combined flows are screened
? ?Q7/i equalization. The equalization basin had a 24-hour capacity
^r-i^ J unclarifi?d discharge from the equalization basin is
directed to an aeration basin with approximately 12-hour detention
/oon ?? °rgtn*c load to the basin of about 3600 kg per day per 1000 m3
nf ?a + ^'^y/1'000 ft»). The final clarifier hL an overflow rate
of 24 to 28 m3/day/m2 (500 to 600 gpd/ft2) . ^J-uw tdte
An organic removal of 80 percent produced an effluent BOD5
concentration of 343 mg/1 and suspended solids reductions of 92
percent. Effluent suspended solids concentrations of 190 mg/litre
*£l 5*i lnff?ec^iye solids capture in the final clarifier. The pH of
the effluent is 8.0 to 8.5. The most interesting aspects of these
treatment operations are the high pH of waste entering the aeration
m^iL-jan^ • e 4.l!19h mixed 1:L<3uor suspended solids concentration
maintained in the aeration basin. In many cases, a pH above 11 0 is
seen^as potentially toxic to biological activity.' Eowev^r? carbon
tbou rVrrnSm "-Pi"^- is adequte touce the pH
to about 8.0, at which point biological stabilization occurs Since
primary clarification is not provided, all suspended solids in thl
^o?er^ Waf 6 9° directly to the aeration basin. All solids captur
must, therefore, occur in the final clarifier. The most important
fact to note is that from the start of operation, the tre^tmen? plant
"af overloaded compared to the design of the system. Further some
difficulty in solids capture in the final cl Jifier was^xplrienced
In spite of the very high effluent concentrations, variability and
upsets were not related to winter conditions. t^inty ana
Removals of 89 percent for BOD5 and 90 percent for suspended solids
were observed during a sampling visit for toxic pollutants at plant
no. 320. However at the time samples were taken the skimmer in the
clarifier was not working properly and was by actually stirring ^p the
water, it was decreasing the removal efficiency. Furthermore no
'
"~
172
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A related biological treatment technology is the oxidation ditch. The
oxidation ditch is essentially a modified form of the activated sludge
system. Applications of this process on domestic waste treatment are
numerous in Europe. A full-scale installation at Oisterwijk,
Netherlands, has successfully treated chrome tannery wastes since
1973. This system is called the Carrousel system. In tannery
treatment, the wastes were directed to an oval ditch or "race track"
for aeration. Separate equalization facilities were not required
since the ditch provides excellent equalization. An adjustable
immersion dish aerator operates in a localized and limited volume of
the channel and imparts oxygen to the wastewater and regulates the
velocity of flow in the channel. The effluent is clarified prior to
discharge with the sludge returning to the aeration zone. The
oxidation ditch operates in the extended aeration mode (one day
hydraulic detention or greater) and at high mixed liquor solids. The
resulting food-to-microorganism (F/M) ratio is very low. At these low
F/M ratios (0.05), long detention time, and high sludge age,
endogenous respiration minimizes the amount of waste sludge.
Data for the first year operation of the Carrousel system on leather
tanning waste at a hydraulic load of 1800 m3/day is summarized in
Table 29.
Table 29
Carrousel System Performance for Leather Tanning Wastewater
Pollutant
Parameter
BODS
COD
Cr
Total N
NH4-N
Raw Secondary Effluent
1100
3390
19.5
408
264
20
249
0.27
270
248
Percent
Removal
98
93
99
34
5
This fully-operational European Carrousel treated the flow from a side
leather tannery using 25,060 kg per day of green-salted hides (55,200
Ib/day). The tanning process produced 1800 m3/day (0.475 mgd) of
wastewater from pulp hair, chrome tan, and finishing operations.
Hydraulic detention time in the oxidation ditch varied from 2 to 3
days, and the rate of activated sludge return was estimated at 75
percent. Production of secondary sludge was about 0.3 kg (Ib) dry
solids per kg (Ib) BOD^ applied, or 0.55 kg (Ib) dry solids per kg
(lb) BODJ5 without primary sedimentation. The organic load on the
ditch varied from 23.5 to 48.2 kg BODJ5 per day (51.8 to 106.2 lb BOD_5
per day). The oxygen supplied was about 1.75 times the average
requirement, however. This was sufficient for peak demands. High
removals of BODj> (98 percent) and COD (88 percent) result at the low
F/M ratio.
173
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Sulfides were completely oxidized with the aeration supplied and
chrome precipitation was highly effective, with concentrations below 1
mg/1 observed in the effluent. Nitrification was sporadic, with some
denitrification through the liberation of nitrogen gas.
High removals of BOD, COD, suspended solids, chromium and detergents
resulted from the operation of the Carrousel tannery waste treatment
facility. Efficiency did not decrease during the winter months.
This same system was recently installed at a shearling tannery (no.
253) in New England. This Carrousel system treats 300,000 gallons per
day of primary effluent. During a very cold period (even for New
England) from December 1976 through February 1977, average influent
and effluent BODS concentrations were 341 mg/1 and 8 mq/l
respectively. Ammonia concentrations in the influent and effluent
were 32 mg/1 and 8 mg/1, respectively. This indicates that this
activated sludge system produced better results than the Netherlands
application, including demonstration of nonsensitivity to winter
temperatures in removing carbonaceous oxygen demand (BODS) and
nitrogenous oxygen demand (ammonia) by nitrification. This'svstem,
like the activated sludge system at tannery no. 320, operated at hiqh
mixed liquor suspended solids (6,000 - 15,000 mg/1).
These results have been further corroborated by a POTW in New England
treating greater than 90 percent of its waste load from tannery no
^!Z J ^ .POT*! 1S a high rate (F/M 9reater than 0.1) short hydraulic
detention time (approx. 12 hrs.) activated sludge system. During the
first year of operation (1976), final effluent quality was poor due an
extended acclimation period and to lack of familiarity with the
operational idiocyncracies of the plant. After operational procedures
were refined, effluent BODS concentrations improved dramatically, from
an average range of 102-393 mg/1 to a range of 49-67 mg/1. in fact
during the very cold winter months of 1976-1977, effluent BODS quality
improved to 34 to 45 mg/1, since that time tannery flow has increased
o^r^?™ ^• f n des^ limits for extended periods of time, but better
operating skills have maintained average BODS effluent quality below
80 mg/1. Therefore, the basic feasibility of the activated sludqe
demonstrated. ^ imp°rtanCe °f dili*ent operation have blen lirmly
Activated sludge systems, including various modifications, have been
and can be effective in organic reductions to low BODS concentrations
even under low temperature conditions. Removals of'suspended solids
prior to final effluent discharge and maintenance of a large Juantity
of active biomass in the aeration basin, especially during winter
montns to compensate for lower rates of organism activity, appear to
fina?c!ar!rLr?n COnservative design *nd diligent operation of the
Based on the discussion above, treatment of process wastewaters by a
high solids, low F/M, extended aeration activated sludge system is
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appropriate for the leather tanning industry. The performance of
primary coagulation-sedimentation followed by activated sludge
biological treatment has been established primarily by plant no. 47,
as noted in Section IX of this document. The long-term performance
(annual average) for this plant is BOD5 - 60 mg/1, and TSS - 95 mg/1.
With the addition of in-plant control and preliminary treatment (i.e.,
chromium recovery, ammonia substitution, catalytic sulfide oxidation,
flue gas carbonation of segregated beamhouse wastewaters, and water
conservation/reuse), the Agency believes that this long-term
performance is improved primarily due to longer hydraulic detention
times and reduced pollutant loads. Additional rationale is presented
in Section X. The Agency has conservatively estimated the achievable
long-term concentrations in the effluent from this secondary
biological process as follows: BOD5 - UO mg/1; TSS - 60 mg/1; total
chromium - 1 mg/1; oil and grease - 14 mg/1; TKN - 30 mg/1; ammonia -
10 mg/1; and phenol - 0.25 mg/1. For residual COD an effluent
concentration of 250 mg/1 was determined from a ratio of COD to BODJ5
developed from biological treatment data during an EPA study.71 This
relationship is displayed in Figure 3. For BODj> concentrations below
160 mg/1 the plot approximates a straight line. Achievable COD
concentrations for technologies which generate effluent BOD5
concentrations below this value have been determined using the BODj>
concentration and Figure 3.
Rotating Biological Contactor. The rotating biological contactor
(RBC) consists of a series of closely spaced flat parallel disks which
are rotated while partially immersed in wastewaters being treated. A
biological growth covering the surface of the disk adsorbs dissolved
organic matter present in the wastewater. As the biomass on the disk
builds up, excess slime is sloughed off periodically and is settled
out in sedimentation tanks. The rotation of the disk carries a thin
film of wastewater into the air where it adsorbs the oxygen necessary
for the aerobic biological activity of the biomass. The disk rotation
also promotes thorough mixing and contact between the biomass and the
wastewaters. In many ways the RBC system is a compact version of a
trickling filter. In the trickling filter, the wastewaters flow over
the media and thus over the microbial flora; in the RBC system, the
flora is passed through the wastewater.
The system can be staged to enhance overall waste load reduction.
Organisms on the disks selectively develop in each stage and are thus
particularly adapted to the composition of the waste in that stage.
The first stages might be used for removal of dissolved organic
matter, while the latter stages might be adapted to nitrification of
ammonia.
The RBC system was developed independently in Europe and the United
States about 1955 for the treatment of domestic waste, but found
application only in Europe, where there are an estimated 1,000
domestic installations.72 The use of the RBC for the treatment of
industrial wastes in the U.S. has been under evaluation for some time.
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Bench scale tests have been made on tannery wastewater. Other pilot
scale results on meat packing waste showed a BOD5 effluent
concentration of approximately 25 mg/1.73
Data from one of the suppliers of RBC systems indicate ammonia removal
of greater than 90 percent by nitrification in a multistage unit.73
Four to eight disk stages with maximum hydraulic loadings of 61
1/day/m2 (1.5 gpd/ft2) of disk area are considered normal for ammonia
removal with final ammonia concentrations as low as 2.0 mg/1 or
less.74
Rotating biological contactors with secondary clarifiers could be used
as a substitute for an entire aerobic system. The number of stages
required depend on the desired degree of treatment and the influent
strength. More typical applications of the rotating biological
contactors, however, may be for polishing the effluent from biological
processes, nitrification of effluents, and as pretreatment prior to
discharging wastes to a municipal system. A BOD5 reduction of 98
percent is reportedly achievable with a four-stage RBC.72
The major advantages of the RBC system, as indicated by the suppliers
of this equipment, are its relatively low first cost; the ability to
stage to achieve dissolved organic matter reduction with the potential
for removal of ammonia by nitrification; and its resistance to
hydraulic shock loads. Disadvantages are that the system should be
housed in cold climates to maintain high removal efficiencies and to
control odors. Although this system has demonstrated its durability
and reliability for domestic wastes in Europe, its use on several
industrial wastes in the United States has not yet established a high
degree of confidence in this technology.73
Nitrogen Control. Nitrogen control is provided through the process of
nitrification-denitrification, as described below.
Nitrification.
Nitrification is the biological conversion of nitrogen in organic or
inorganic compounds from a more reduced to a more oxidized state. In
the field of water pollution control, nitrification usually is
referred to as the process in which ammonia as ammonium ion is
oxidized to nitrite and nitrate sequentially. When aeration systems
are used to treat an industrial wastewater, some nitrification can be
expected to occur naturally, thus reducing the quantity of ammonia
requiring further removal.
Adequate process design and operating control are necessary for
consistent results. Factors that affect the nitrification process
include concentration of nitrifying organisms, temperature, pH,
detention time, dissolved oxygen concentration, and the concentration
of any inhibiting compounds.74
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Nitrifying organisms are aerobic and adequate dissolved oxygen (DO) in
the aeration system is necessary. DO concentrations should be above 1
to 2 mg/1 to assure consistent nitrification. Nitrification is
affected by the temperature of the system. Available information
provides conflicting data on the systems1 performance at low
temperatures. Although detailed studies are lacking,it should be
possible to achieve nitrification at low temperatures and compensate
for slower nitrifying organism growth rates by maintaining a longer
solids detention time and hence larger nitrifying active mass in the
system.76
The optimum pH for nitrification of municipal sewage has been set
between 7.5 and 8.5. Nitrification can proceed at low pH levels, but
at less than optimum rates. During nitrification, hydrogen ions are
produced and the pH decreases, the magnitude of the decrease being
related to the buffering capacity of the system.
The removal of nitrogen compounds from a tannery waste stream is
important because these compounds: exhibit an oxygen demand similar
to that of BOD; provide nutrients for plant organisms in the receiving
water body, increasing eutrophication rates; and may present a
significant hazard to aquatic organisms.
Biological oxidation of organic and ammonia nitrogen to nitrites and
nitrates is accomplished by only two bacteria types, nitrosomonas,
which convert ammonia and organic nitrogen to nitrites, and
nitrobacter, which convert nitrites to nitrates. The growth
conditions necessary for these bacteria can be supplied by
conventional secondary activated sludge systems, although longer
detention times are required, generally resulting in larger systems
for BOD control, especially at low operating temperatures.
Very little data exists on nitrification toxicity effects. Sulfides
under BPT conditions should be reduced to a concentration of 1 mg/1, a
level below concern for either nitrifying bacteria. Chromium, which
is reduced to a level of 2 mg/1 after chromium recovery and combined
primary treatment, is of potential concern since one source77 lists
chromium toxicity at levels of 0.25 mg/1. While actual test data is
limited, the acclimatization of organisms should tend to mitigate any
problem with chrome toxicity. Removal of phenol and other potentially
toxic organic chemicals in the primary and first stage along with the
acclimatization of the organisms of activated sludge to the tannery
wastes should permit effective nitrification.
Nitrification rates are reported to be dependent on temperature. One
reference7® states that proper nitrification occurs only at
temperatures of at least 12 to 15°C. One successful application of
nitrification has been demonstrated at a rendering plant in Ohio.
This is a conventional activated sludge system which uses two
consecutive aeration tanks in series prior to secondary clarificatin
and multi-media filtration. The system operates at a temperature of
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at least 55°F (12.8°C) even on the coldest days by virtue of the high
raw wastewater discharge temperature associated with the rendering
process, estimated at 90°F (32°C); and on extremely cold days, by
covering the tops of the aeration tanks with boards. Tanneries
discharge raw wastewater at temperatures approximating 70°F (21°C) in
winter, and thus the expectation would be that lower temperatures may
occur in a tannery nitrification system. Heat addition is also
possible as an alternative but would increase operating expense unless
waste heat recovery (such as stack gas heat) were employed. Only
during the coldest time of the year in the northern locations should
temperature maintenance be of concern.
To operate successfully, nitrifying bacteria must have proper pH
conditions (7.5 to 8.2) and nutrients (such as calcium, magnesium,
phosphorus, copper, and iron).78 These requirements, if not present in
tannery wastewaters, will have to be provided by chemical addition.
Only pH control and phosphorus addition are expected to be needed for
normal tannery wastewaters.
Physical-Chemical Processes - LEVEL 4 A
Chappel Process. The Chappel process is a patented physical-chemical
process for treating wastewater streams. The basis for this process
is the assumption that all waste streams contain components which
flocculate or settle in the proper environment. The process consists
of dividing the wastewater stream into two equal parts, treating one
part with the acid solution (mineral acids, aluminum sulfate, and
oxidizing chemicals) and the other with the alkaline solution (sodium
hydroxide, forms of dissolved aluminum, and oxidizing chemicals), and
then reuniting the divided waste streams. Some flocculation and
solids formation takes place when the acid solution and the alkaline
solution are added to the separated parts of the waste stream.
Additional flocculation and solids formation takes place when the two
parts of the wastewater stream are reunited. The reunited wastewater
stream flows into a series of two or more settling tanks. The
wastewater and sludge entering each of the tanks is initially agitated
and allowed to settle. Supernatant and sludge are pumped counter-
current through the series of settling tanks. Agitation in each tank
mixes settled sludge with the wastewater. According to Chappel, the
sludge aids the flocculation and settling of pollutants in the
wastewater stream. The wastewater stream from the final settling tank
is passed through a sand or multi-media filter and discharged to the
receiving waters. Some of the sludge from the first settling tank is
recycled to aid flocculation and sedimentation and the remainder is
removed for disposal. It has been indicated that this sludge has no
oxygen demand and is sterile; however, it may require dewatering,
The Chappel process was used to treat less than 100,000 gallons per
day of wastewater from a retan facility (no. 247). In this
installation, there were nine settling tanks (existing idle tankage
used in part), and only 25 percent of the effluent is passed through a
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*4
rudimentary* sand filter. The other 75 percent is discharged directly
to the receiving river. It is particularly noteworthy that this
system was housed within the tannery itself. This is very important
to plants which have very limited adjacent land available for
installation of equipment.
The effluent quality from this installation far surpassed state permit
requirements. This process is highly effective in removing pollutants
from tannery no. 247 wastewater, as shown in Table 30. It is obvious
that this application of physical-chemical treatment was highly
effective in removing toxic pollutants (see also Table 36, Section X)
including chromium, and conventional and nonconventional pollutants.
Table 30
Treatment of Wastewater with Chappel Process
at Tannery No. 247
Pollutant
Parameter
BOD5
COD
TSS
TKN
NH3
OSG
cr
Typical Influent
Value (mg/1)
700 -
1200 -
300 -
120 -
60-1
110 -
16
800
2700
800
270
60
280
Typical Effluent
Value (ma/11
3 -
20 -
6 -
3 -
1 -
4 -
less
10
40
11
6
3
9
than 0.1
Process effectiveness has been tested in treating tannery wastes from
three other tanneries. Results are summarized in Table 31.
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Table 31
Performance Summary of the Chappel Process Treating
Tannery Wastewaters
Pollutant Influent Value Effluent Value
Parameter (mg/1) (mq/1)
Tannery No. 57
BOD5 1800 5-70
Sulfide 70 0. 1
Tannery No. 409
Chromium 20 0.1
Sulfide 1.8 0
Tannery No. 213
Chromium 40 0.1
Sulfide 1 0.2
Wastewaters with significantly higher BOD5 may require a modification
of the process to obtain effective treatment. The modification
consists of operating two systems in series; the first removes the
bulk of the pollutants, while the second "polishes" the wastewater.
This process is also being used to treat a paper mill waste, although
data is not currently available.
On a long-term basis, the Agency conservatively estimates that this
physical-chemical treatment system will produce the same effluent
concentrations as can be produced by a PAC upgraded (Level 5} and
multi-media filtered (Level 6) activated sludge system. Both the
physical-chemical (Level 4A) and biological treatment (Level 4)
systems are preceded by in-plant control (Level 1), preliminary
treatment (Level 2), and primary treatment (Level 3), which will
produce pretreated effluent concentrations similar to or lower than
those listed in Table 30 as "Typical Influent" at plant no. 247. The
long-term treated effluent performance (concentrations-mg/1) is
conservatively estimated by EPA to be somewhat higher than represented
in Table 30 because the available data from plant no. 247 was not for
a sufficient length of time to estimate effluent variability. The
estimated concentrations are as follows: BOD_5 - 14 mg/1; TSS - 16
mg/1; COD - 180 mg/1; oil and grease - 6 mg/1; total chromium - 0.33
mg/1; TKN - 15 mg/1; ammonia - 5 mg/1; and phenol - 0.1 mg/1.
Color Removal. Vegetable extracts and syntans used in the production
of leather comprise only a small percentage of the total waste volume,
however, spent vegetable tanning solution can be responsible for a
major portion of the organic content and most of the color agents in a
total wastewater discharge.
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Several factors relating to the chemical structure of the color agents
were considered significant in efforts to reduce color by Nemerow. *«
Tomlinson, et. al.«o conducted laboratory investigations with mimosa
(wattle) extract with lesser amounts of quebracho and chestnut bark
extracts. Two commercial syntans, Orotan TV (a phenolic syntan) and
Leukanol D-48 (an acid or naphthalene syntan), were also used in the
blend. A small amount of sodium bisulfite was added to accelerate the
adsorption of tannin by the hide protein collagen. These six
ingredients, mixed in the proper proportions with water amounting to
about 75 percent of the total weight of the solution, constituted the
stock tanning solution.
During the course of the investigations, the following treatment
techniques for the removal of color were evaluated: oxidation with
sodium hypochlorite, use of lime or alum, and coagulation with organic
polymers.
Color removal from the vegetable tanning solution was achieved under
the treatment conditions developed in the course of the research The
treatment scheme, as described in Tomlinson and applied to an actual
tannery, would involve the following sequential steps:
1. Segregation of the spent vegetable tanning liquor.
2. Addition of sulfuric acid to reduce the pH of the solution
below 3.0.
3. Addition of a predetermined dosage of a preselected cationic
organic polyelectrolyte and, at the same time, continued
addition of sulfuric acid to maintain the pH below 3.0.
4. Slow mixing to provide sufficient contact time for maximum
color removal.
5. Sedimentation for approximately 30 minutes.
6. Decantation of the treated supernatant, at a regulated rate,
to the remainder of the waste flow from the tannery for
further treatment, if needed.
7. Withdrawal of the sludge for further dewatering, if
required, and disposal.
Tomlinson summarizes his study as follows:
"A commercially available cationic polymer was used successfully
for color removal in the research. The optimum dosage was on the
order of 30 mg/1. (This procedure resulted in a reduction in
color of more than 90 percent). Concurrent with the excellent
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color removal, significant reductions were observed in the COD
(50 to 60 percent) and suspended solids (85 to 90 percent).
"Sludge amounting to approximately 30 percent of the original
volume of the tanning solution is produced as a result of the
need to remove the color and reduce the other pollutants. It was
shown in this research that the sludge resulting from coagulation
at a pH of approximately 2.5 to 3.0 settled better and had
greatly improved dewatering characteristics compared with sludges
resulting from treatment at higher pH levels.
"The economic feasibility (of this technology) would depend on
the characteristics of the waste, the effluent requirements, and
the cost of achieving them by other methods. For a given real
situation, complete laboratory studies would have to be made with
various polyelectrolytes to determine the combination of
polyelectrolyte, dosage, pH, mixing time, flocculation time and
settling time that would produce the desired results at least
cost. Because characteristics of tanning solutions vary, it is
to be expected that optimum treatment combinations would also
vary."
Upgrading Biological Treatment with Activated Carbon - LEVEL 5
The use of activated carbon in treating industrial wastewaters has
been generally successful depending on the application, the soundness
of engineering, the degree of proper operation and maintenance, and
the performance criteria established for the system. According to
Cheremisinoff81 "adsorption studies indicate that most of the EPA-
proposed dissolved organic toxic chemicals can be removed from the
water by activated carbon (and) other similar chemical contaminants
(aromatic, nonpolar, high molecular weight), such as OSHA-defined
carcinogens and the chemicals under examination by EPA for inclusion
on the toxic substances list are also predicted to be adsorable from
wastewater by activated carbon."
Cheremisinoff explains further:
"Adsorption makes possible the purification of wastewater streams
containing only small amounts of impurities that would be
difficult to clean by other means and at an attainable cost.
Carbon is the most versatile of the solid adsorbents and finds
the widest application in both air and water pollution control.
The use of activated carbon for removal of organic compounds from
air and water streams has a long history of successful use, being
one of the most efficient organic removal processes available.
"The ability of activated carbon to adsorb material either from
gases or from liquids stems from its highly porous structure.
Each particle consists of a vast network of interconnecting pores
of a variety of sizes. The highly porous structure results in a
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very large surface area, providing many sites upon which
adsorption of molecules can take place. Normally, adsorption on
activated carbon is the result of physical attraction of
molecules to the carbon surface by van der Waals forces. As a
rule, molecules with higher molecular weights experience greater
forces of attraction than materials of lower molecular weights
Hence, activated carbons, aside from the effects of molecular
screening due to the sizes of the pores, have a preference for
higher molecular weight substances.
"When a granule of activated carbon is placed in contact with a
mixture of gases, the higher molecular weights are preferentially
attracted to the carbon where they are adsorbed. when a granule
of activated carbon is placed in contact with a liquid mixture,
there is a similar tendency for higher molecular weight
substances to be adsorbed. However, in the liquid systems the
situation is more complicated. In liquid systems, activated
carbon tends to have a preference not only for substances which
are of higher molecular weight but also for those substances that
are non-polar in nature. Thus, there is a particular affinity
for the adsorption of non-polar organic molecules from polar
solvents such as water. f^iaj.
"The forces of attraction between the carbon and adsorbate
molecules are greater for adsorbate molecules which are similar
in size to the carbon pores. The most tenacious adsorption takes
^oCexW!?en th? P?reS are barely l^ge enough to admit the
adsorbate molecules. The smaller the pores with respect to the
molecules, the greater the forces of attraction. The pores
cannot be so small, however, that the adsorbate molecules find it
difficult to enter, or the adsorptive capacity for those
molecules will be greatly reduced. Although the effects are not
completely understood, it is known that the presence of elements
other than carbon can have a considerable influence on a carbon's
adsorptive capabilities. Particularly important is oxygen, which
can exist in a variety of chemically combined conditions with the
surface carbon atoms. These oxygen groups appear to increase the
affinity of the carbon for polar compounds and decrease its
selectivity for non-polar compounds.
"Carbon adsorption systems are of two types-regenerative and
nonregenerative. For operations in which daily carbon
requirements are large or under constant use, granular carbons
offer the advantage of established methods of regeneration which
greatly reduce carbon replacement costs. Powdered carbons offer
mfvanno?eh ^ aPPlicat^ns where the daily carbon requirements
may not be large enough to warrant installation and operation of
snPMf?/^ener^1Ve equi?ment- Jt is also possible that some
specific adsorptive capacity may be available in certain types of
powdered carbon."si ^yy** or
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Powdered carbon is mixed directly with the liquid to be treated. This
•slurry1 is then agitated to allow proper contact. Finally, the spent
carbon, carrying the adsorbed impurities, is filtered or settled out.
In practice, a multiple-stage, counter-current process is commonly
used to make the most efficient use of the carbon«s capacity.
A relatively new application of powdered activated carbon (PAC) is
being tested and evaluated in combined carbon-biological systems,
because of the ability of activated carbon to improve the performance
of biological systems. This concept is now undergoing extensive
testing, using powdered carbon material in activated sludge systems.82
The carbon is metered into the system with the influent at a
concentration normally less than 100 mg/1. It is recirculated and
purged along with the biological solids at a rate which maintains an
equilibrium concentration of 1000-2000 mg/1. Since the powdered
carbon is added directly to the activated sludge process, this
eliminates the need for carbon-adsorption beds or columns.
Powdered carbon may provide some of the following benefits when added
to activated sludge systems:
1. improved toxic pollutant removals;
2. improved organic pollutant removals, including BOD, COD, and
TOC;
3. more uniform operation and effluent quality, particularly
during periods of widely varying organic and hydraulic
loads;
4. decreased effluent solids and thicker sludges resulting in
reduced sludge handling costs;
5. adsorption of organics, such as detergents, oils and dyes
that are refractory to the biological system;
6. protection of the biological system from toxic waste
components;
7. more effective removal of phosphorus and nitrogen;
8. increased effective plant capacity at little or no
additional capital investment;
9. savings on operating costs resulting from reduced defoamer,
coagulant and power requirements; and
10. greater treatment flexibility than other methods since
carbon dosages can be varied to match waste strengths and
flow rates.
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Powdered carbon improves treatment in the activated sludge process
because of its adsorptive and physical properties. Carbon adsorbs the
pollutants and oxygen, localizing them for bacterial attack. Because
reac^n? blc"ac^°" . i? dependent upon the concentration of thl
reactant, this localizing effect serves to drive the reaction further
towards completion, resulting in improved BOD removal, a a "any
pollutants that are not biologically degraded in a conventional
11 9e tem W°U1< be degrad*d if the* we« i* Sntlct wi?h
theMos e* we« ntct wi
the biomass for a longer period of time, when adsorbed by the carbon
these molecules settle into the sludge. Contact time is ther^b
extended from hours to days. This results in lower effluent COD and
High density powdered carbons improve solids removal in secondary
clarifiers. This results in lower effluent suspended solids and also
wou?dU?LT/n ?°2- ^ hlgh °rganiC load Conditions which normalfy
would lead to sludge bulking, the dense carbon will act as a weighting
agent keeping the sludge in the system. A doubling of sludge voluml
BothXe?he" nlf ^f wherVarb°? addition is practiced is not^ncommon?
Both the use of greater sludge mass and the extended retention of
slowly degraded compounds by the carbon give more time for the
compound to be biologically stabilized. when dispersed Mofloc
results due to low organic loads, carbon serves as a seed for floe
formation, preventing loss of solids under these conditions
Phosphorus and nitrogen removals are reportedly enhanced.
Powdered carbon can be added at any convenient point in the activated
sludge process to get it into the reaction section, it is not
necessary to add carbon continuously in most cases. Batch addition at
any time of day is generally satisfactory. A dense, easily we?ted
carbon can be added dry or slurried with water, in fart, the very
nature of the slurried carbon in a solution provides extremely
^T Ka?d thorou|h contact between the carbon particlefand the
solution being treated-more so than with granular carbon treatment
Chemical coagulants can be added along with the carton to prS;
simultaneous removal of colloidal organics. provide
The effectiveness of powdered carbon as an additive to improve
activated sludge treatment has been demonstrated in a variety of
industrial applications and at POTWs. These improved operatina
properties of activated sludge as demonstrated in oiher application!
covers wastewaters with similar characteristics. For example both
leather tanning and petroleum refining wastewaters IrTpr^rea?ed
prior to biological treatment and PAC addition. Pretreated wastewater
in both industries also contain toxic pollutants. Therefore i* T«
EPA- s belief that PAC addition is tLnsferabt; becaulf of tte exact
duplication of the technology as used in other industries to
teSogyVa'lso "ansfera^ej "* *»*.«» "«*«— "? this
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This type of treatment has gained acceptance in the last tour years
and is currently an essential part of treatment at 60 to 80 plants.
These plants range in size from 10,000-gpd package units located along
the Alaska pipeline to a fully integrated 40-mgd powdered activated
carbon treatment system (PACT).84
The PACT process involves a continuous addition of powdered activated
carbon to the aeration tank. Buildup in the aeration tank occurs (a
function of the sludge retention time), providing a substantial
reservoir of carbon in the system. The continuous addition of fresh
carbon to the aeration tank allows the process to adsorb nonbiological
organic matter present in the wastewaters, thereby providing a degree
of advanced treatment concomitant with normal secondary treatment. A
recent study85 indicated that powdered activated carbon addition to
activated sludge systems provides exceptional resistance to shock-
loading by trichlorophenol, presumably due to the large reservoir of
carbon carried in the MLSS- Trichlorophenols occur in most tannery
wastewaters at concentrations ranging up to about 10 ppm in the raw
wastewater. A study86 completed on organic-chemical wastewater
indicated that the PACT system was economically, preferable in
achieving the desired effluent quality to columnar, granular and
activated-carbon systems, both preceding and following activated
sludge.
Data pertaining to effectiveness of the PAC treatment system in
removing toxic pollutants indicates good performance for many organic
constituents. Removal in excess of 95 percent for total phenol was
observed through the treatment system, producing an effluent
concentration of less than 0.02 mg/1.87
The addition of PAC to an activated sludge system was investigated on
a pilot scale to improve the treatment of petroleum refinery
wastewater. It was found that "effective removal of oil and colloidal
solids in the pretreatment step is necessary for successful
operation." In addition, cost effectiveness was achieved by "operating
at a very high sludge age and a low carbon dose." The higher sludge
age did not result in the deterioration of settling characteristics.
A decrease in effluent variability was noted which was attributed to
enhanced nitrification at low temperatures and dampening effects of
increased hydraulic loading to the activated sludge plant. In
addition to effective removal of ammonia (less than 1 mg/1), PAC
addition was responsible for reductions of 65 percent for soluble
organic carbon and 95 percent for phenolics with a residual
concentration of less than 0.02 mg/1.86
A similar study was conducted by another refinery which was interested
in improving conventional activated sludge systems. Accomplished with
pilot plant units, increased sludge age (from 10 to about 50 days) in
combination with powdered carbon addition was found to be a potential
alternative to installing costly granular activated carbon columns to
treat secondary effluent. With good pretreatment, upgraded activated
187
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sludge proved effective in reducing ammonia, oil and grease, and
phenols to median levels of less than 4.0, 5.0 and 0.1 mq/1
respectively.ee liy-«-r
In the poultry processing industry, addition of powdered carbon at a
southern commercial poultry processing plant improved effluent quality
and process control. so A full-scale evaluation of powdered carbon
treatment began in August 1974. In this plant, two activated sludge
units treat an average of 400,000 gallons during a 10-hour working
day. The poultry waste passes through air flotation treatment prior
to activated sludge treatment. Polymer is continuously fed to
secondary clarifiers to improve solids settling. Sludge solids are
removed periodically (every 3-4 weeks) and transported to drying beds.
The variable flow in this system, attributable to normal processing
operations, caused frequent sludge bulking, high effluent solids, and
variable effluent quality prior to use of powdered activated carbon
Three aerobic lagoons were required for further organic removal!
Prior to carbon addition, the activated sludge effluent averaged 35
ppm suspended solids, 70 ppm oil, 7 ppm BOD5, and 24 ppm ammonia-
nitrogen «
During the monitored period, influent to the activated sludge system
averaged 254 ppm BOD5, 95 ppm oil, and 129 ppm suspended solids.
Dissolved oxygen levels of 8-11 ppm were maintained in the activated
sludge aeration basins. Powdered carbon was maintained in the
aeration basins at an equilibrium level of 1,000-1,200 nom Thic?
required a daily addition of 10-15 ppm based on influent to" make up
*!. £a^on 1°?*. 2U5"igJ Sludge wastin9- After carbon addition,
variability diminished and overall quality improved. Average effluent
solids decreased 60 percent to 12 ppm, BOD5 decreased 57 percent to 3
n^n^oeareaSed 1° Ve*cent to 21 PP1"' *"d nitrogen decreased 83
percent to 4>Ppm. Assuming that the influent analysis made during the
control period is typical of normal plant operation, the overall
" percent:
The basis for estimating the performance of activated sludge with PAC
addition started with the long-term performance of activated sludge as
previously described under "Secondary" Biological Treatment - Level 4
preceded by in-plant control (Level 1) , preliminary treatment~1Zevel
2), and^ primary treatment (Level 3). The range of removal
efficiencies and final effluent concentrations after PAC addition in
the above referenced applications served to guide EPA's estimates of
removals in this case. As summarized in Table 32, EPA estimates that
±n?g™ally S^lized leather tuning effluents can be upgraded by
about 50 percent for BOD and 60 percent for TSS. This nominal level
was chosen because the pilot and full scale studies were performed on
biologically stabilized wastewater in other industries where the
characteristics of the tested effluent was similar to treated leather
tanning wastes .
188
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PAC upgraded biological treatment will yield the following
concentrations: BOD5 - 20 mg/1, or approximately 50 percent removal
where 60 percent removal or more has been reported; TSS - 25 mg/1, or
approximately 60 percent removed where similar removals but
substantially lower effluent concentrations were achieved; COD - 195
mg/1, as developed by the COD to BODjS relationship (see Figure 3) ; oil
and grease - 10 mg/1, or approximately 50 percent removal where
effluent concentrations as low as 5 mg/1 were reported; (total)
chromium - 0.5 mg/1, or approximately 50 percent removal estimated
somewhat less than TSS removal due to residual TSS and fine, insoluble
chromium which may carry over from secondary clarifiers; TKN - 20 mg/1
and ammonia - 5 mg/1, or approximately 50 percent reduction where
greater removals and effluent concentrations as low as 4 mg/1 were
reported, and where nitrification without PAC addition at plant no.
253 has produced ammonia concentrations very close to these
concentrations; and phenol - 0.1 mg/1, which is a concentration
achieved by this technology in the petroleum refining industry.
A full-scale demonstration of this technology is now underway at
tannery no. 253 and additional data will be reviewed by EPA-
Table 32
Incremental Increase in Summary of Performance of Activated Sludge
by Powdered Activated Carbon Addition 86 87 88 89
Demonstrated
Incremental Estimated
Increase in Increase in
Efficiency Effluent Efficiency Estimated
Parameter (percent) Cone, (mg/1) (percent) Cone, (mg/1)
BOD5 57 3 50 14
TSS 60 12 60 16
Oil and Grease 70 5 50 6
Ammonia 83 4 50 5
Phenol 95 0.1 60 0.1
189
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Table 33
Summary of Multi-Media Filtration Performance
Range of ~ " ~~~~—
Incremental Estimated
Increase in Increase in Estimated
Performance Effluent Performance Effluent
Parameter (percent) Cone, (ma/1) (percent) Cone, (mg/11
BOD1 50 6 30 14
TSS 45 - 77 5 35
16
Multi-Media Filtration - LEVEL £
With the exception of gravity sedimentation, deep-bed filtration is
the most widely used unit process for liquid-solids separation. Deep-
bed filters have been employed in systems for phosphorous removal from
secondary effluents, and in physical-chemical systems for the
treatment of raw wastewater.
Filtration has been applied in a wide variety of municipal and
industrial applications. In most cases, filtration is used for
nr^e1??*0*-??81?"*1 suspended solids afte* biological treatment. 103
105 lie 119 Filtration is also being used in the leather tanning
industry for separation of residual biological and inert solids which
may include PAC with adsorbed toxic organic compounds and insoluble
heavy metals such as chromium. Therefore, EPA believes that multi-
media filtration technology is transferable, and that the same range
of performance demonstrated in other applications is also transferable
to the leather tanning industry.
Waste containing suspended solids passes through a filter containing
K^nUla£ ma^er1i?1 resulting in the capture of suspended solids in the
or ;h. ^h6?Dually the pressure drop through the bed becomes excessive^
or the ability of the bed to remove suspended solids is impaired. The
filtration cycle ceases and the bed is backwashed prior to its return
to service in an ideal filter, the size of the particles should
decrease uniformly in the direction of flow. This condition t=
partially achieved with the use of a multimedia deep bed fUter
This type of filter uses materials with different densities ranging
from large size particles with the lowest densities at the top of the
the lilt- ^i^10163 Wlth the highest densities at the bottom of
the filter. With this arrangement, the filter has a large storaae
capacity for suspended solids, and is able to remain in operation for
long™/r^10dS ?5 5lme; Influent soli3s should be limited to about
100 mg/1 to avoid too frequent backwashing. Effluent suspended solids
are normally less than 10 mg/1.us Filtration can also accomplish
removal of free oil, and to a limited degree, emulsified oil. Where
190
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concurrent removal of suspended solids is necessary, filtration can be
effective.
A summary of the typical performance of several applications of
filtration applied on activated sludge and other biologically
stabilized effluents is given in Table 33. From these data, EPA finds
that a reasonable estimate of achievable performance by filtration is
30 percent removal of BODJ5 and 35 percent removal of TSS. For
purposes of applying this technology to PAC upgraded effluent quality
(Level 5), the following conservative long-term performance is
achievable with multi-media filtration of upgraded activated sludge
effluent: BOD5^ - 14 mg/1, or approximately 30 percent removal; TSS
16 mg/1, or approximately 35 percent removal; oil and grease - 6 mg/1,
or approximately 40 percent removal.
A lower removal efficiency for TSS (35 percent) than noted in the
literature was considered appropriate because of the low operating
range of long term average effluent concentration in this industry
(less than 20 mg/1), and the very fine solids which must be separated.
A somewhat lesser efficiency for BODj> removal (30 percent) was
conservatively estimated because of the low operating range of
concentration (less than 20 mg/1) and for lack of more extensive data.
Oil and grease removal efficiency was estimated to be approximately 40
percent because residual oil and grease after biolgocial treatment is
likely to be associated with suspended solids, and thus removed at an
efficiency comparable to TSS. Other effluent concentrations were
estimated as follows: COD - 180 mg/1, as developed by the COD to BODJ5
relationship (see Figure 3); TKN - 15 mg/1, or approximately 25
percent removal due to removal of residual insoluble proteinaceous TKN
with TSS; ammonia - 5 mg/1, or no change since filtration does not
enhance nitrification; (total) chromium - 0.33 mg/1, or approximately
35 percent removal which is the same as the anticipated removal of
TSS; (total) phenol -0.1 mg/1, or no change since phenol is removed
by biological treatment and none occurs in filtration. These values
were chosen as representative of the performance to be expected on
similar biologically stablized leather tanning wastewater where the
residual biological solids, inert PAC particles and oil and grease are
amenable to physical separation.
Granular Activated Carbon Columns - LEVEL 2
The properties outlined during the discussion of powdered activated
carbon are also pertinent to granular activated carbon (GAC). Rather
than being mixed in a slurry, granular carbon is packed in beds or
columns. The water to be treated is then either filtered down or
forced up through the beds. In this manner, each successive layer of
carbon acts to remove impurities, with maximum adsorption taking place
in the early stages of contact and less and less taking place as the
gradually purified solution continues on until (if the bed is
sufficiently deep) all adsorbable organic impurities are removed. In
191
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some cases, suspended matter (via filtration by the carbon) as well as
dissolved pollutants (via adsorption) can be removed simultaneously. *i
As noted by Cheremisinof f e i, carbon adsorption has a wide range of
applicability to wastewaters with residual dissolved organic compounds
of high molecular weight (i.e., chlorinated phenols) which must be
removed. For this reason, EPA believes that GAG are transferable to
application in this industry.
Minor a 2 describes the benefits of activated carbon treatment as
follows:
"The properties of many organic chemicals complicate conventional
biological treatment. Activated carbon can be an attractive
systemf fo ^ f°11OWing **™^*S °*er biological
1. insensitivity to toxics (and will in
fact remove most toxic organics) ;
2. less sensitivity to temperatures;
3. less time required for start-up;
4. higher removal of BOD, COD, and TOC
for many (but not all) wastes; and
5. effectiveness in streams with high
dissolved solids.
"Since it can be regenerated and entrainment into the wastewater
nh . by screens' th* granular carbon has been
chosen over powdered carbon in the majority of applications. The
technology for evaluating the applicability of granular activated
carbon and the ability to design commercial systems from pilot
data are well established. t^-tut
"The ability of activated carbon to be regenerated for economical
reuse is a distinct advantage. Both powdered and granular
carbons are capable of being regenerated by existing technology.
Granular activated carbon is regenerated thermally at
temperatures of 1600-1800<>F. Due to the high hardness and
fofof ! c°D attrition °f coal-base granular carbon, system
losses of 5-8 percent per cycle are commonly experienced.
ac^vat?d c*rbon is also regenerated thermally at 1600-
applications."91
However, a major inhibition to the widespread use of granular
activated carbon has been the high capital cost of installing thermal
to^hff^^i11^63 ^ Sma11 installations. A possible %oiu™on
to this problem has been developed by a major chemical company whereby
customers can lease carbon adsorption systems at a guaran^ed monthly
^ ^^^ *** resP°nsibility *<* regeneration at
centra
192
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As mentioned previously, granular carbon has been chosen over powdered
carbon in the majority of full-scale industrial applications.
Adsorption equipment consists of adsorbers or columns holding the
granular activated carbon beds through which wastewater flows. They
can be designed for pressure or gravity flow to achieve the desired
contact time of the water and carbon. Suspended solids and space
considerations are also a factor in adsorber configuration. When
suspended solids are present, they will be filtered out on the carbon
bed. This dual purpose of carbon beds can be usefully employed as
long as the adsorbers are designed to accommodate backwashing and bed
cleaning procedures, such as air scour and/or surface wash.
Performance criteria for the application of activated carbon columns
should be developed from continuous on-line pilot scale (or larger)
apparatus for any complex wastewater. Because of the waste-specific
nature of adsorption, an approach to evaluating activated carbon
performance from on-site investigations has been developed.92 Although
the published document is directed towards the organic chemicals and
plastics industry, the general approach can be applied to most
wastewaters including those generated by leather tanners.
The effectiveness of granular carbon adsorption in treating industrial
waste was reviewed by D. G. Hager.93 Examples of TOC, color, and
phenol removal were demonstrated for 107 different industrial sources.
Fifteen plants have operated for two years, meeting the adsorption
design objectives. In addition to the wastewater survey conducted by
Hager, a selected number of adsorption isotherm tests were conducted
on synthetic samples of water containing toxic chemicals as defined by
EPA. Other data in the literature94 95 96 97 suggest that carbon
adsorption should be an effective treatment method for organics
similar to the designated toxic chemicals, including a wide range of
organophosphorus compounds, and polycyclic aromatic hydrocarbons.
Based on the adsorption isotherm test results in the initial 1973
survey93, several plants elected to follow up with pilot studies.
Fifteen plants installed adsorption systems; the results of these
studies are summarized in Table 34. In those cases where the TOC
effluent appears high, the carbon is being used to remove chemicals
prior to conventional biological treatment. These are chemicals that
are toxic in nature and would have a tendency to inhibit or destroy
the biological activity of the system. The data also reveal that in
every case some form of pretreatment, such as equalization, pH
adjustment or filtration, was used prior to carbon adsorption. All
rely on off-site reactivation of the carbon where both rotary kilns as
well as multihearth furnaces are employed.
To achieve advanced treatment of secondary effluent from an organic
chemical manufacturing complex, granular activated carbon columns
following trimedia filtration were selected based on extensive pilot
plant data.98 The in-place biological treatment system was operating
193
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effectively in removing BOD, COD and TOC from the complex wastewaters;
however, the removal of color, odor and toxic constituents was
necessary. In addition, suspended solids required further reduction.
At another chemical manufacturing plant, the effluent from a
coagulation-sedimentation step is fed directly to the carbon columns
for removal of organic impurities. Most notable is the reduction of
phenol which consistently over several years averaged better than 99
percent." Spent carbon is directed to a reactivation furnace for
regeneration.
Filtration of the effluent from biological treatment systems prior to
introduction into carbon columns is an accepted practice to minimize
clogging of the columns. Application of carbon columns in this
industry is after filtration (Level 6) and upgraded activated sludge
biological treatment (Level 5). Granular activated carbon columns
should yield residual concentrations for the significant pollutant
paramters as follows: BODj> - 6 mg/1; TSS - 3 mg/1; COD - 165 mg/1;
oil and grease - 2 mg/1; total chromium - 0.25 mg/1; TKN - 14 mg/1;
ammonia - 5 mg/1; and phenol - 0.1 mg/1. All of these effluent
concentrations are estimates based upon literature data, with the
exception of: (total) chromium - 0.25 mg/1, or approximately 25
percent removal attributable to removal of residual TSS, to approach
the limits of chromium solubility.
Membrane Technology
General Various membrane processes that are finding interest in
pollution control applications as end-of-pipe treatment and for in-
plant recovery systems are ultrafiltration, reverse osmosis, and
electrodialysis. Although these processes are available for producing
a concentrated solution from a relatively dilute feed, each process
tends to occupy a specific region of application due to economic as
well as technological considerations.
In contrast to the membrane processes of reverse osmosis or
ultrafiltration, however, electrodialysis employs the removal of the
solute (with some small amount of accompanying water) from solution
rather than the removal of the solvent. Another major distinction is
that only ionic species are removed. The fact that only ionized salts
will be removed allows for the simultaneous separation of these
substances from any neutral or un-ionized organic matter that may be
present. Although these features are similar to ion exchange, the
advantage is that in electrodialysis the process is continuous, with
nothing to be regenerated, hence no chemical additions are
required.100 The process finds usefulness in treating brackish waters,
removing dissolved inorganics in 750-7500 mg/1 concentrations, and in
some by-product recovery schemes. The necessary equipment is usually
compact, and proven plant scale performance exists, both in municipal
and industrial applications.
195
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ionic components of a solution are separated
er USe °f semiPermeabl« ion-selective membranes in the
ecroiaysis process. in water a salt dissolves to produce
positively charged anions. if an electrical field is placed Icrosl
!^1Utl?n' the cations migrate toward the negatively charged
cathode while the anions migrate in the opposite direction toward ?he
£?£* Y char?ed an0de' Cation-exchange membranes are permeabll
simnarlv^asr™? Y -tO Cations' while ™i™ exchange membranes
similarly pass only anions. Because of the alternate soacino nf
cation and anion permeable membranes in the electric field
compartments of concentrated and dilute solutions (salts) are formed
dUutio^idTanl *£t0 /hlCh th? •fCed W3S i^roduced become th4
referred in ~ ^ streams exiting from these compartments is
referred to as the dilution stream (any organic matter present will
remain in this stream). The stream issuing from the concentrate
compartments is the brine. concentrate
In commercial practice the basic appratus for electrodialysis is a
F?™ r,?f*^CtangUlar membranes terminated on each end by an electrode.
Flow of the process streams is contained and directed by spacers that
alternate with the membranes. The assembly of membranes? spices and
electrodes is held in compression by a pair of end places The
apparatus thus resembles a plant-and-frame filter presf. Ancillary
exce nC"? POW6r SUPPly' pUm*S' and Piping, is conventional
components are used wherever possible to avoid
-~ — • •*•"*•' £^^-«hx t^f ,*,*^ju v* *—V d V VJ JL L4
process streams. C^entS ""* the Production of metal ions into the
Since unwanted side-reactions of hydrogen gas and alkali formation
take place at the cathode while chlorine and acid form at the anode
these two compartments must be provided with separate flush streams?
±^?h *'!^!0dialySiS 1S n0t a new P"cess ™* has, in fact, been
- sss
.
the low level of technological development. Because of
Most of the stable membranes today, however, are based on copolymers
of divinyl-benzene-styrene with ion-exchange groups. The cation
available
196
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Most membranes permit operation up to 50 degrees C, although membrane
development activity is attempting to raise that limit. The ability
of the different types of membranes to withstand pH extremes varies
considerably. For example, some are stable in acid environments
ranging from 5 to 35 percent HJ2SO4 and from 4 percent up to
concentrated HCl. On the alkaline side, some membranes cannot be used
at all, while others are claimed to be stable in 50 percent NaOH.
Almost all of the electrodialysis membranes are quite sensitive to
oxidizing solutions. Some permit short duration exposure to 1 ppm
chlorine while needing less than 0.1 ppm for long-term operations.
Fouling of the membranes is the primary disadvantage of the system.
This may occur through scaling (the chemical precipitation of salts),
which is caused by exceeding solubility limits. Suspended organic
matter also needs to be removed down to 50-100 microns. The physical
configuration of the electrodialysis stack affects its susceptibility
to solids fouling. Iron and manganese should be limited to 0.2 ppm
combined. Trivalent ions, such as aluminum and phosphate, may cause
increased electrical resistance. Some organic matter, including ionic
surfactants (MBAS), and tannic, fulvic, and humic acids, as well as
butyrate and larger esters, can cause membrane blockage. To reduce
membrane fouling, activated carbon pretreatment, possibly preceded by
chemical precipitation and some form of multi-media filtration, may be
necessary.
Other limitations to this process are the high initial costs,
requirement for skilled labor, high energy costs, need for membrane
cleaning and replacement, sophisticated equipment and instrumentation,
and the production of excess brine waters.
The principal action of electrodialysis—to concentrate ionic
materials—enables consideration of systems which accomplish the
following separations: to reduce the volume of brine waste streams;
to recover inorganic salts; to remove inorganic salts from waste
streams to facilitate further treatment; to separate and recover ionic
materials from complex aqueous solutions containing neutral organics;
and to concentrate acids.
In the metals industries, electrodialysis can be used to recover
metals from plating waste streams.101 Substantial disposal problems
exist from depleted plating baths and rinse waters. Materials sud. as
cyanides of zinc and cadmium can be reconcentrated to bath strength
and can be reduced in concentration to very low levels. A closed-loop
recovery process103 incorporating electrodialysis and ion-exchange
permits complete recovery of nickel, allows reuse of the dilute stream
for rinsing, and recovers the acid required for the regeneration of
the ion-exchanges. Copper and chromium have also been recovered from
etching processes; while a waste stream of dilute ammonium fluoride
from glass etching has been successfully separated and concentrated by
electrodialysis for further treatment.
197
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Within the leather tanning and finishing industry, it mav crove
feasible to remove such trace inorganics as chromium/copper? lead
nickel, and zinc by the electrodialysis process. This remains to be
" — titutents° £
Bleaching wood pulp with chlorine or hypochlorite solution yields a
copious effluent stream of salty water, the disposal of which has
become a significant problem in the paper industry. io« By the use of
electrodialysis, an effluent of 4000 ppm Nacl can be separated into a
UP to Jfooo1 n°ntal^n9 5?° PPm °r 16SS °f Salt and a ^rine stream of
up to 150,000 ppm. The water stream, demineralized to the ouritv
required by the process, is recycled as wash water. The brine stream
is electrolyzed in a membrane cell to sodium hydroxide solution and
chlorine; these substances may be used directly, or part of each mav
be combined to form sodium hypochlorite solution. Thus thf brine
stream is also returned to the process. orine
By using a process similar to that described above, it may be possible
to significantly reduce the total dissolved solids and chloride
concentrations present in tannery wastewater. The largest portionfof
the dissolved solids are sodium chloride and calcium sulfate? Sodium
on ?£ '„ 1C^ C3n te f°Und in the ran9e ^ 500-8900 ppm (depending
on the category) , comes principally from removal of salt or brine from
the raw hides by washing and also from salt added in the cicklina
operation. Used in conjunction with total dissolved solids thl
chloride parameter indicates percentages of other dissolved solids
*r^ °, ^he substantial amount of dissolved s^liS/chloridls
present, electrodialysis may find application in reducing these minor
**
any
Whenever an effluent stream contains an organic or inorganic ionic
material, electrodialysis offers a possible method for recoverv
separation, segregation, or concentration of that material Provided
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-------
pollutants discharged by tanneries to POTW's or surface waters. These
technologies are pertinent to the leather tanning industry because
they (1) reflect current practices of the industry, (2) were evaluated
during demonstration studies conducted by the industry, or (3) will
control or remove selected pollutants. In instances where the control
of specific constituents is a primary concern, technology transfer was
necessary. An example of this approach is the upgrading of secondary
biological treatment with PAC addition. To control toxic organic
compounds and heavy metals, EPA assessed this technology from
information developed by the organic chemicals and petroleum refining
industries and then applied it to leather tanning effluents.
Applicable technologies for the leather tanning industry and their
performance were determined upon the best available information. As
can be seen from Figures 4 through 8, segregation of the waste streams
from the beamhouse and tanyard operations is an integral part of
comprehensive waste management for the industry. For subcategories
with beamhouse operations, the segregated waste stream will be
subjected to sulfide oxidation and flue gas carbonation. Ammonia
substitution in the bating process and chrome recovery and reuse are
applicable to the tanyard processes. The effluents resulting from
these measures, which are defined as Levels 1 and 2, are then combined
for equalization followed by coagulation-sedimentation (Level 3). A
schematic of the appropriate end-of-pipe treatment technologies,
including Level 3, is provided in Figure 9.
The effectiveness of the selected technology scheme which includes in-
plant controls and end-of-pipe treatment is summarized in Table 35.
For each level of technology through Level 3 (coagulation-
sedimentation) , long-term performance is shown in terms of percent
removal for the selected parameters. Effectiveness for Levels 4
through 7 in removing pollutants is expressed as residual effluent
concentrations over a long term.
TOXIC POLLUTANT REDUCTIONS
The list of 129 toxic pollutants is divided into four groups of
chemicals: volatile organics, semi-volatile organics, inorganics
(primarily metals), and pesticides and PCB«s. The first group is
primarily composed of chemicals that readily vaporize at ambient
conditions. Common solvents such as benzene, toluene and carbon
tetrachloride are typical chemicals in this group. Removal of these
chemicals from wastewater would occur any time the wastewater is not
confined in a completely enclosed container such as a pipe or a full
tank. The removal rate is substantially increased by introducing
turbulence in the wastewater from any source such as a mixer, an
aerator or in cascading flow in a treatment device. The removal of
these chemicals as a vapor results in a discharge to the atmosphere.
The second group of chemicals, the semi-volatile organics, includes
higher molecular weight organics such as phenol and the substituted
199
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phenolics that are used as hide and leather preservatives. Removal of
some of these compounds from wastewater is known to occur in a number
of ways, such as oil-water separation by skimming in sedimentation
tanks, and biological treatment by activated sludge. For other
chemicals in the group, no determination of an effective technology to
remove them has been made or reported. Secondary biological treatment
removes phenol.
*
Physical-chemical mechanisms such as adsorption of the chemicals on
settleable and suspended solids or entrainment or reaction with
additives or reaction products in precipitation, coagulation, and/or
sedimentation has been demonstrated to be effective in toxic pollutant
removal.
The inorganic toxic pollutants are the metals plus cyanide. Chromium
is listed as one of these pollutants and is in widespread use in the
tanning industry. Specific processes to control, recover, or remove
chromium have been described previously in this section. Treatment by
physical-chemical means is the primary removal mechanism for metals
removal. Cyanide removal has not been specifically applied in this
industry as it has been in the electroplating industry.
Pesticides and PCB's comprise the fourth group of toxic pollutants.
Physical-chemical methods, especially adsorption, are reportedly
effective in removing pesticides from wastewaters. Similar technology
is being installed to remove PCB's from wastewater by a plant that
previously manufactured PCB's.
The effectiveness of various end-of-pipe treatment systems in removing
toxic pollutants from leather tannery wastewater is indicated in Table
36. These results originate from the field sampling and laboratory
analysis of wastewater from 22 tanneries and two POTW's with a large
proportion of tannery wastewater to treat.
In Table 36, the notation ND indicates that the compound was not
detected with the analytical procedure prescribed for that specific
sample. Sometimes ND notations in the "INF" (influent) column are
followed by indications of presence of the compound in the "EFF"
(effluent) column. The determination of toxic pollutants at low-level
concentrations is a question of detection of the compounds, with the
analytical methodology not the absolute determinant of presence or
absence of the compounds. A compound not detected may be present, but
at a very low concentration. To analyze some influent samples it
became necessary to dilute them to a considerable extent and thereby
reduce the concentration. In some cases, this dilution reduced the
concentration of a compound to a level below the detection limit.
This prevented identification and quantification in the specific
sample and waste stream that it came from. This produced the influent
ND notations in the table for some compounds followed by reported
presence in the effluent stream.
207
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The trace "tr" designation was used to indicate the identification of
the presence of a compound but with insufficient quantity (generally
less than 10 ug/1 for organic compounds) to quantify its presence.
The results in this table suggest a number of conclusions, as follows:
1. Volatile organics are largely removed in any type treatment
system that is in use in the leather tanning industry,
except for some degree of persistence of chloroform. The
uniformity of removal is probably due to the volatility and
resulting ease of stripping these compounds from solution.
It also appears that this occurs regardless of treatment
effectiveness on any other pollutant parameters whether
conventional, nonconventional, or toxic.
2. Semivolatile organics also receive some degree of removal by
all waste treatment systems in use. Those systems that are
most effective in removing the conventional and
nonconventional pollutants (EOD5f TSS, etc.) also seem to
be most effective on semivolatiles.
3. Metals comprise the inorganic group of toxic pollutants and
include chromium. All of the treatment systems remove the
metals to some extent; and performance on the metals seems
to correlate with removal of conventional and
nonconventional pollutants, most importantly TSS. The most
effective treatment system on metals is the physical-
chemical system.
4. The fate of the toxic pollutants removed from the wastewater
was not determined. However, EPA believes it is highly
probable that a substantial percentage of the pollutants
removed are removed with the solids separated from the
wastewater.
5. In general, effective waste treatment for the toxic
pollutants seems to correlate well with effective removal of
the conventional and nonconventional pollutants. If the
treatment system does well on the latter, then it will do
well in removing the toxic pollutants.
SLUDGE HANDLING AND DISPOSAL
A major part of tannery waste treatment involves the handling and
disposal of the semi-solid sludges obtained from liquid treatment
processes. The most predominant methods of ultimate disposal of
tannery waste sludges include sludge lagoons, landfills, dumps, and
spreading on the land.
209
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Some attempts have been made to dewater sludges prior to ultimate
disposal, with varying success. The three principal dewater ing
techniques include centrifugation, vacuum filtration, and pressure
filtration. Centrifuges have appeared to meet with less success than
vacuum filters or pressure filters.
Reducing the moisture content of sludge by spreading on drying beds
has also been successful in some areas. This is particularly
attractive to smaller facilities where land area is available.
One of the principal difficulties with tannery waste is the chromium
content in sludges and the potential toxic impact of this metal on the
environment. In testing a heat-treated alkaline sludge, it has been
indicated that some of the trivalent chromium may be oxidized to the
thron^erV°r^ *^e^ < the trivalent chromium is converted
through the high temperature, high pressure, high pH, and the
oxidizing environment of the heat treatment process.
Chromium reuse reduces the levels of chromium in the sludge. Disposal
sfn!^rve^n^^^in?^heS! 10W6r residual quantities of chromium in a
sanitary landfill will reduce environmental problems.
Prior to dewater ing in mechanical equipment, sludge is normally
o?Rdth^ed b^USG Of *erric salts, lime, polymers, or a combination
of these. The quantity and type of chemicals required are dependent
upon characteristics of the sludge being handled.
Dewatering with mechanical equipment such as centrifuges generally can
produce a cake containing 15 to 30 percent dry solids. Plate and
frame filter presses have been found to produce cakes of 40 to 50
percent dry solids.. The higher capital cost of filter presses may be
l£a£a a 5T ** 10Wer !f ulin* and disposal costs where landfills are
located great distances from the tannery or the POTW.
Some sludge is disposed of on the land, taking advantage of its lime
content for agricultural purposes. One disadvantage of this type of
r™5^ Practice is the potential toxic effects of chromium or other
constituents on plants, groundwater, and surface water supplies.
Lagoons for dewatering have some limited uses. In humid areas where
°r 6XCeeds ev*P°ration, such application is not
Use of lagoons, drying beds, landfills, and landspreading all require
key attention to the environmental impacts. Particularly important is
the leaching of potential toxic or organic materials to the
groundwater supplies or surface waters. Proper controls must be taken
to ensure that these conditions will not develop ^axen
210
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SECTION VIII
COST, ENERGY, AND NON-WATER QUALITY ASPECTS
Plant sizes and related production rates have been selected for
purposes of economic impact analysis. Five typical "model" plants
were selected in Subcategories One and Two; three model plants were
selected in Subcategories Three and Seven; four model plants in
Subcategory Five; and two model plants in Subcategories Four and Six.
CAPITAL COST ASSUMPTIONS
EPA calculated the waste treatment system capital costs based on the
plant production, wastewater flow, and related pollutant load data for
typical "model" plants in each subcategory. Capital costs for
specific treatment system components largely depend on the wastewater
flow or hydraulic load.
The actual component cost estimates are based on unit cost curves.
The following assumptions are reflected in the capital costs:
1. Costs are expressed in December 31, 1977, dollars.
2. Expected accuracy for these conceptual-type estimates is plus or
minus 40 percent.
3. Engineering costs are not included in cost estimates. However,
most states require that design plans and specifications be prepared
by a registered professional engineer in accordance with applicable
codes.
4. Construction work to be performed by outside contractor using union
labor and no work to be done by in-plant labor or maintenance
personnel (except stream segregation work). The construction
contractor's overhead and profit are included in the cost estimates.
5. No land acquisition cost is included.
EPA believes that the capital cost estimates in this report may be
higher than the actual cost that tanneries will incur in installing
the suggested technology. For example, a pollution control consultant
to the industry reported that to his knowledge none of the tanneries
for which he was consulting had used an outside contractor to build
waste treatment facilities, but that the facilities at each tannery
had been built with in-house labor. This would represent a
substantial cost savings. There are numerous other investment cost
reductions available to the resourceful tannery in design,
construction, and operation of treatment ictechnology. These
reductions cannot be accurately defined or predicted, nor is the
211
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effect of them included in the cost data. The intent of this cost
information is to present maximum expected costs of wastewater
treatment technology suggested for the industry.
ANNUAL COST ASSUMPTIONS
The components of total annual cost are capital cost, depreciation,
and operating and maintenance costs, the latter including manpower,
chemical, and power costs. The cost of capital is estimated to be 9
percent of the investment cost. This cost is an estimate of the
weighted average of the cost of equity and of debt financing
throughout the industry. The depreciation component of annual cost
was estimated on a straight-line basis, with no salvage value and an
assumed-year life for all capital investment costs.
The rate for tannery labor manhours was set at $5.00 per hour plus 50
percent for burden, supervision, etc., based on information from the
industry. The electrical power cost was estimated to be 2.5 cents per
kilowatt-hour (kWh). The operating year was assumed to be 260 days
per year in all cost calculations to account for the variable numbers
of days per week of operation reported by the industry. The operating
year used for the wastewater treatment plant was 365 days per year.
Operation and maintenance costs are based on December 31 1977
dollars. '
CAPITAL AND OPERATION AND MAINTENANCE COST CURVES
Using the assumptions stated above, total installed costs were
developed by the technical contractors based upon: 1) the design
factors presented in Section VII of this document for each unit
treatment process, and 2) updated cost information for equipment and
material, labor, chemicals, and energy. Costs were developed for each
of the treatment technologies described in Section VII. The capital
cost curves were obtained by plotting the total installed costs
against wastewater flow rate. The annual operation and maintenance
costs were computed by totaling the manpower, maintenance, chemical
and electrical power costs. This total was compared to average flow
rate in the operation and maintenance cost curves. Cost curves were
generated for eight wastewater treatment levels (as introduced in
Section VII), stream segregation, and sludge dewatering. The
rationale, design basis, and items included in each of the cost curves
are described in the following sections.
Stream Segregation - Level 1
Because of different in-plant treatment requirements for the beamhouse
and tanyard wastewaters, the flows from these sources have to be
physically separated until after Level 2 in-plant treatment. The
segregation of the beamhouse and tanyard wastewaters involves
modifications to processing wheels, piping from the wheels to a sump
212
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and installation of the sump system for each of the two waste streams.
The piping and sump pumps have been sized to simultaneously handle the
flow from two wheels.
The number of processing wheels that require modification was
determined by dividing the plant production in hides per day by 270.
The cost of modifying each wheel was computed to be $5,000. The first
cost of the sump pumps and the sump pit was calculated at $28,000,
regardless of the plant production rate. The installed cost of the
piping, fittings, valves, and pipe hangers was computed for each of
the tannery sizes considered. The total installed cost for steam
segregation, including piping, pumps, and modifications, is plotted
versus average flow rate in Figure 10.
The operation and maintenance costs associated with stream segregation
were computed using the following criteria:
1. Maintenance - 20 percent of installed cost of piping,
processing drum modifications and sump pump.
2. Operation - 60 horsepower-hours per processing drum per day.
Figure 11 shows the annual operation and maintenance costs for
stream segregation for the range of flow rates considered.
Stream segregation applies to subcategory numbers 1, 2, 3, 6, and 7.
Sulfide Oxidation - Level J
The recommended in-plant process changes include the recovery and
reuse of the chemicals contained in the unhairing liquors. The
recovery and reuse of the unhairing liquors removes most of the
sulfide content of the beamhouse waste stream. The remaining residual
sulfide concentration must be completely removed prior to discharge to
the end-of-pipe treatment plant to eliminate the possibilities of
corrosion and the health problems associated with hydrogen icsulfide
gas generation. The residual sulfide concentration in the unhairing
waste can be removed by utilization of the sulfide oxidation process.
The recommended sulfide oxidation process includes two holding tanks,
a pump, blower, and chemical feeding equipment. The spent unhairing
wastewater is pumped into the storage tanks, the magnesium sulfate is
added, and the air for oxidation is supplied by the blower. The
design criteria for each of the components included is as follows:
1. Holding tanks (each) = 75 percent of daily flow of unhairing
wastewater;
2. blower = 0.22 cfm/lb (0.014 m3/min/kg) sulfide oxidized;
3. pump = capable of draining two unhairing vats in 60 minutes;
213
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Figure 10. Capital Cost Curve for Stream Segregati
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Figure 11. Operation and Maintenance Cost Curve for Stream Segregation
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U. sulfide content (after recovery and reuse) = 3 pounds fkal/1000
pounds (1000 kg) of hides processed; and Pounds (*g)/1000
5. wastewater volume = 0.52 gallons/pound (0.0043 m3/kg) of hide
processed.
A plot of the installed cost of sulfide oxidation incorporation based
on the above parameters is shown on Figure 12 as a function of th*
number of cattlehides processed per day of operation.
Sulfide oxidation applies to subcategory numbers 1, 2, 3, and 6.
Ammonia Substitution - Level _1
During the unhairing operation, lime and sharpeners are added to
loosen or dissolve the hair attached to the hide. Bating follows the
reducfthe oH^f the f^- the.alkaline ««l"ng of thl hides Ld to
reauce the pH of the solution prior to the tanning operation. The nH
sulfate10withSthrr"?duaSieiimey^CallX by ?h? "action"^ am^niSm
^o I - • residual lime to produce calcium sulfate. Most of
The reduced ammonia content in the wastewater effluent resulting from
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if "Ite"^??"" Um°* 'na th« -»"«"Mi™ Of M,n..lo. for a.oni,
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shows the operation and maintenance cost curve for sulfide
and ammonia substitution in bating, suitide
Ammonia substitution applies to subcategory numbers 1, 2. 3, and 6.
216
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PRODUCTION, NUMBER OF HIDES / DAY (CATTLE HIDES)
Figure 12. Capital Cost Curve for Sulfide Oxidation
217
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Figure 13. Operation and Maintenance Cost Curve for Sulfide Oxidation
and Ammonia Substitution
218
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Flue Gas Carbonation/Sedimentation - Level 2
Flue gas carbonation is the final in-plant wastewater treatment step
for the beamhouse wastewater prior to the equalization basin. Flue
gas carbonation consists of blowing flue gas from a boiler into the
beamhouse wastewater prior to a clarifier. The lime and protein
particles that are precipitated in the clarifier will be withdrawn by
a sludge pump for resale as a by-product or be dewatered for handling
as solids waste.
The capital cost for flue gas carbonation includes the flue gas
handling equipment, sludge pump, and circular clarifier. The
installed cost of the flue gas handling equipment required for
carbonation, blower, piping, and diffuser is shown graphically on
Figure 14. The volume of beamhouse wastewater was conservatively
estimated to be 75 percent of the total wastewater flow from the
tannery for cost estimating purposes. The clarifier sizing is based
on a hydraulic overflow rate of 400 gpd/ft2 (16.3 m3/d/m2) . Figure 15
shows the flue gas carbonation clarifier capital cost, plotted against
beamhouse flow rate.
The operation and maintenance (OSM) cost for the flue gas handling
blower and piping was computed at 20 percent of the capital cost plus
the electrical power cost for the blower. The O&M costs for the
clarifier and sludge pump were calculated using 2 manhours of labor
per day, 5 percent of the capital cost, and the electrical power
required for the clarifier drive and the pump motors. The operation
and maintenance cost curve for flue gas carbonation/sedimentation is
shown in Figure 16.
Flue gas carbonation/sedimentation applies to subcategory numbers 1,
2, 3, and 6.
Equalization and Coagulation-Sedimentation - Level ^3
Following flue gas carbonation the wastewaters from the beamhouse and
tanyard combine and enter the equalization tank. The equalization
tank smooths out pH swings during tank dumps, equalizes surges in flow
rate, and stores wastewater for use by the succeeding treatment units
during weekends and plant shutdowns.
Figure 17 is a graph of the capital cost of the equalization capital
cost against the total average design wastewater volume. The
installed cost of equalization is based upon a detention time of 36
hours; a steel tank on concrete slab; and a mixer size of 0.1 hp/1,000
gallons (26.4 hp/1,000
The operation and maintenance cost for equalization is equal to the
electrical energy required for the connected horsepower of the mixer,
operating 24 hours per day, 365 days per year.
219
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REFERENCE: Q INFORMATION FROM TANNERY CONSULTANT
DATA FROM TANNERY
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Figure 14. Capital Cost Curve for Flue Gas Handling Equipment
230
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O
UJ
(O
z
O
JOOJ
50
G.RD. K
M 3/ OA'
3,000
f 5
— T \ n—i 1
1 50
o too
,000
»
100
[X)
,000
10
-I— 1 1 1
500,000
00
BEAMHOUSE WASTEWATER FLOW
Figure 15. Capital Cost Curve for Flue Gas Carbonation Clarifier
221
-------
too
50
cr
<
UJ
o
o
LU
o
Z 10
UJ
Z
-------
1000
500
O
O
O
-trt-
X
100
o
UJ
to -I
50
6.RD. 1C
M 3/ DA>
),000
f 5
— 1 1 T
0 K
— 1 1
50
>0
1 1
,000
»
I — r-
100
DO
000
10
300,000
00
Figure 17.
AVERAGE WASTEWATER FLOW
Capital Cost Curve for Equalization
223
-------
was*ewater- included in the capital cost is the solids-
-sssss •ssss.isr a" -
The operation and maintenance cost for coagulation-sedimentation was
forerann,f i Y addlng the.cost of the coagulation chemicals to the cost
^L,*" manhour requirements. The annual manhour requirements for
operation and maintenance labor are shown in Figure 19.
Treatment Level 3, as described in Section VII, includes both
^» ^*^°n coagulation-sedimentation. The capital cost would be
the additive costs obtained from Figures 17 and 18. The operation
maintenance costs for treatment Level 3 can be deterSned^rom Fi
Equalization and coagulation-sedimentation of combined streams applies
to all subcategories.
Secondary Biological Treatment - Level l
"' aS described i« Section VII, consists of
tende^ aeration ^P« activated sludge process.
a-Ksra
aeration provided by subsurface static aerators;
aeration basin is an earthen lagoon with Hypalon lining-
detention time is determined by F/M of 0.1.
final clarifier overflow rate is 150 gpd/ft* (6.2
maintenance cost for secondary treatment is
i* n rf*m -v- XN *^O r-» —,. -~ ^
of
Upgraded Secondary Treatment with PAC Addition - Level 5
As described in Section VII on treatment technology, the pollutant
removal effir-i^n™ ^f ^^4.^,.,^^^ _, , /JL **' t^oj.j.urant
(treatment Level 4) can be
activated carbon to the
224
-------
1000
500
O
O
O
-co-
X
100
50
10
G.RO. 10,000
M 3/ DAY 50
50,000
IOO,OOO
500,000
100
300
1000
AVERAGE WASTE WATER FLOW
Figure 18. Capital Cost Curve for Coagulation-Sedimentation
-------
10.000
5,000
MAINTENANCE LABOR
100
FT.* 1
V.2
2
BOO
3 5
1,0.
0
>0
l(
1 r
>U 21
8,000
X> *<
— 1
•»ft
Figure 19.
PRIMARY CLARIFIER SURFACE AREA
Annual Manhour Requirements for Coagulation-Sedimentation
226
-------
100
90
CT
UJ
\
O
O
o.
•-
X
UJ
o
10
IT
UJ
O.
O
O.P. D. 10,000 I
M3/DAY 80
80,000
100,000
500,000
100
9OO
1000
AVERAGE WASTEWATER FLOW
Figure 20. Operation and Maintenance Cost Curve for Equalization
and Coagulation-Sedimentation
227
-------
IOOO
500
O
O
O
100
O
O
to
z
, sp_
G.RD. 10,000
M 3/ DAY 30
100
9OO
900,000
IOOO
Figure 21.
AVERAGE WASTE WATER FLOW
Capital Cost Curve for Activated Sludge Secondary Treatment
228
-------
100
50
o
o
-co-
X
UJ
o
Is.
UJ
<
2
<6
O
tr
UJ
o.
o
e.p. o. 10,000
1 1 1
1 1
1 1
80,000
I — P—
1 1
100,000
M3/DAY 50 100 300
500,000
1000
AVERAGE WASTE WATER FLOW
Figure 22. Operation and Maintenance Cost Curve for Activated
Sludge Secondary Treatment
229
-------
aeration basin. The carbon will be added manually by the bag into the
aeration basin influent. Thus, the capital cost is only the cost of
enough carbon to attain the desired concentration in the aeration
basin, based on the following design criteria: aeration
powdered activated carbon concentration = 1800 ppm;
cost of new carbon (no regeneration) = $0.30/lb ($0.66/kg) ;
sludge age = 30 days; and
number of complete carbon replacements = 12 per year.
The operation and maintenance costs were equal to the annual cost of
replacing the activated carbon lost in the wasted activated sludge
coltf f or r Jhon3 ^ relationship of annual operation and maintenance
costs for carbon replacement versus wastewater volume.
PAC addition to activated sludge applies to all subcategories.
Multi-media Filtration - Level 6
Multimedia filtration follows upgraded activated sludge in the
treatment scheme and is defined as treatment Level 6. The capital
cost of multi-media filtration includes the media, tanks? pumps
Piping valves, and installation and is shown graphically versus
wastewater volume in Figure 24. The cost data shown on Figure 24 wal
fUtratfoTio? renderin9 industry study incorporating multi-media
The cost curve for operation and maintenance of multi-media
filtration. Figure 25, is based on the following components:
Labor = 1/3 man-year for a system operating at less than 100,000
gpd (379 m3/d) wastewater flow;
Labor = 1/2 man-year for systems handling more than 100,000 and
(379 m3/day) ; yP
Power = 10 hp continuous for systems handling less than 100.000
gpd (379
Power = 15 hp continuous for systems rated at 100,000 to 250 000
gpd (379-948 m3/day) ; and
Power = 20 hp continuous for systems handling more than 250,000
gpd (948 m^/day) .
Multi-media filtration applies to all subcategories.
230
-------
100
50
tr
UJ
V
o
o
UJ
o
z
Z JO.
UJ
,000
— 1 1 1
— 1 1
1 1
60,000
I — T~
1 1 r
100,000
500,000
MS/DAY 50 100 300 1000
AVERAGE WASTEWATER FLOW
Figure 23. Operation and Maintenance Cost Curve for Upgraded
Secondary Treatment
231
-------
1000
500
O
O
O
100
a
UJ
50
10
G.RD. 10
M 3/ DAY
,000
5
' ' '
0 l(
)0
1 1
50
1 1
000
»
1 1
100
X)
1 1— T
ooo
10
1 I 1
500,000
OO
Figure 24.
AVERAGE WASTEWATER FLOW
Capital Cost Curve for Multi-Media Filtration
232
-------
100
fifi-
cr
UJ
\
o
o
q.
--
x
UJ
o
UJ
h-
z
o
cr
UJ
a.
o
10
1
O.P. D. 10,000
— 1 1 T
1 1
1 I
50,000
r i
1
100,000
MVDAY 50 100 300
500,000
IOOO
AVERAGE WASTEWATER FLOW
Figure 25. Operation and Maintenance Cost Curve for
Multi-Media Filtration
233
-------
Granular Activated Carbon Columns - Level 7
The use of granular activated carbon columns following multi-media
filtration will further reduce the pollutant levels of BOD5, TSS, COD
and oil and grease. Granular activated carbon column treatment is
referred to as treatment Level 7. The capital cost for the complete
activated carbon column system with two columns is shown on Figure 26
The costs used in this document for carbon columns were taken from the
EPA technology transfer document for carbon adsorption. 10* The costs
shown in Figure 26 are based on an empty bed contact time of 30
minutes.
The operation and maintenance costs associated with treatment Level 7
are summarized in Figure 27 based upon the following design criteria:
Carbon used = 1300 Ib/mgd treated (0.16 kg/m3) ;
Carbon cost = $0.34/lb ($0.75/kg) regenerated by outside
contract; and
Manpower = 2 man- days/week
GAC columns apply to all subcategories.
Physical/Chemical Treatment - Level
The Chappel process, treatment Level 4A, is a patented physical-
chemical treatment process which can produce a treated effluent
quality equal to secondary treatment including powdered activated
carbon followed by multi-media filtration. The tannery treatment
train for direct dischargers using the Chappel process consists of
stream separation, in-plant process changes and treatment
equalization, primary coagulation- sediment at ion and then the Chappel
treatment units. The physical-chemical Chappel process consists of
the following equipment:
circular steel equalization tank, 8 ft. deep, providing 1 hr
detention time;
acid and alkaline chemical addition tanks;
three steel settling tanks, 8 ft. deep, each providing 6-hr
detention time including sludge pumps, aerators, and agitators-
and *
a clarifier with a 400 gpd/ft2 (16.4 ir^/d/m*) hydraulic overflow
rate.
The capital cost of the Chappel treatment process, shown graphically
in Figure 28, was taken from a rendering industry study. 106 The
234
-------
1000
500
-
X
100
<
en
50
6.RO. 1C
M 3/ DAI
),000
f 5
1 1 T
0 l<
— 1 1
50
30
1 1
000
3
DO
100
OOO
10
, I T
5OO.OOO
00
Figure 26.
AVERAGE WASTEWATER FLOW
Capital Cost Curve for Activated Carbon Column System
2,35
-------
100
QC
<
UJ
o
o
UJ
o
UJ
z
o
H S
Ou I
*'», iO.GOu
T)AY SO
1 1 1
1 1 | I T
00,000
r — r~
•oo,
1 1 r
000
1 ' 1 '
500,000
100
300
1000
AVERAGE WASTEWATER FLOW
Figure 27. Operation and Maintenance Cost Curve for
Activated Carbon Column System
236
-------
1000
G.PD. 10
M 3/ DAY
,000
5
1 1 1
0 K
I 1
50
>0
r — i —
000
»
r T
100
X)
i i I
ooo
10
5
00
T
AVERAGE WASTE WATER FLOW
Figure 28. Capital Cost Curve for Chappel Process
237
-------
equalization settling, and clarifier tanks were priced using air lift
pumps at a cost of $750 per foot ($2,460 per meter) in diameter.
Figure 29 is a plot of the operation and maintenance cost of the
Chappel process against treated flow rate.
Sludge Dewatering
The sludge produced from the various wastewater treatment plant
processes, such as coagulation-sedimentation, extended aeration
activated sludge, and multi-media filtration backwash, is relatively
dilute varying from 0.5 to 8 percent solids. To allow for easier
handling and disposal of sludge from the wastewater treatment
facility, a sludge drying or dewatering device is required. A
horizontal tank leaf filter press sized to provide 700 ft* of
filtration area per million gallons (17 mi2/i,QOO m^) of wastewater
was used as the basis for the sludge dewatering cost estimate.
The capital costs required for sludge dewatering are indicated in
Figure 30. The operation and maintenance cost estimate for dewatering
of the sludge is shown in Figure 31.
CAPITAL AND OPERATING COST SUMMARY
Capital costs and operation and maintenance costs have been presented
for the in-plant control, preliminary treatment, and end-of-pipe
technologies applicable to leather tanneries for pollution control.
The levels of technology indicated correspond with those presented in
Section VII of this document. The capital expenditure required to
implement a pollution control program to achieve these levels of
performance will depend on the type and extent of pollution control
equipment in place at each tannery, and on tannery-specific cost-
effectiveness trade-offs between in-plant and end-of-pipe
technologies. In-plant technologies usually involve the reuse,
recovery, or removal of process materials that are pollutants from
specific waste streams, whereas end-of-pipe technologies are applied
to the total wastewater stream to reduce the pollutant loading.
The costs for sulfide and chrome recovery are not included in the
technology tabulation. Chrome and sulfide recovery or reuse processes
are being installed or considered in the industry because of the
strong economic incentive and favorable return on such investments.
The trend in the cost and supply situation for chrome essentially
mandates chrome reuse, thus eliminating chrome recovery as strictly a
pollution control measure.
An increase in energy consumption will occur wherever additional
wastewater treatment or processing is implemented. Substitution of
raw materials with non-polluting alternatives is possible and requires
no additional energy expenditure. Recovery and reuse of raw
materials, instead of once-through use, will produce an overall net
238
-------
100
50
OC
UJ
V
o
o
q.
--
x
UJ
o
z
<
r joj
UJ
(0
z
o
ac
UJ
a.
o
1
e.p. o. ic
"
>.ooo
i — ' ' — n
i , | 1 1
50,000
1 — T~
1 1 r
100,000
' 1 '
500,000
M3/DAY 50 100 300 IOOO
Figure 29.
AVERAGE WASTEWATER FLOW
Operation and Maintenance Cost Curve for Chappel Process
239
-------
1,000
500
O
O
O
X
I
100
O
UJ
50
10
M V DAY
50
REFERENCE: O COSTS CALCULATED FROM LITERATURE
A COSTS OF TANNERY INSTALLATIONS
O
A
G.RO. 10
,000
1 1 1
1 1 I I 1
50,000
1 1
100
000
1 '
500,000
100
900
IOOO
Figure 30.
AVERAGE WASTE WATER FLOW
Capital Cost Curve for Sludge Dewatering
240
-------
100
o
o
o
o
z
<
r 10
UJ
H
<
3E
-------
energy savings in the total economy of the industry, although energy
consumption in a specific tannery may increase.
MONITORING COSTS
The estimated cost is $300 per sample for analysis of acid fraction
organic pollutants and $25 per sample for each inorganic toxic
pollutant based on current sampling and analytical procedures and
technology. The estimated cost of analysis for all pollutants
regulated by BAT (BOD5, COD, TSS, Oil and Grease, Total Chromium,
Phenol (UAAP), TKN, Ammonia and Sulfide) is approximately $100 per
sample. See Section XIV - MONITORING for further details.
ENERGY REQUIREMENTS
The design of end-of-pipe wastewater treatment plant units is
dependent on the performance of in-plant and pretreatment technologies
for specific waste streams originating within a tannery. Reuse of
process streams, recovery and reuse of chemicals, and reduction of
wastewater volume are primary aspects of these technologies. Each of
these reuse and reduction processes is inherently energy conserving in
the production of leather and in wastewater treatment.
The removal or reduction of pollutants in any wastewater stream
requires an energy expenditure. The higher levels of treatment as
described in Section VII produce a higher quality effluent with lower
levels of pollutants. This means a greater energy consumption than at
lesser levels of performance.
NON-WATER QUALITY ASPECTS
Solid Wastes
Characteristics. Solid waste from a tannery with a wastewater
pretreatment/treatment system may include any or all of the following:
1. fleshings,
2. hair,
3. hide trimmings,
4. tanned hide trim and shavings,
5. leather trimmings,
6. buffing dust,
7. leather finishing residues,
8. wastewater treatment sludges, and
9. general plant waste.
The specific types of solid waste generated by a tannery depend upon
the type of processing operations conducted. The quantity of each
type of waste generated depends upon the volume of production at the
tannery.
242
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Tanneries which generate fleshings and hide trimmings sometimes sell
these waste materials to rendering plants, or occasionally to glue
manufacturers. Since these waste materials are highly putrescible,
daily collection is required. Very small tanneries which process only
a few hundred hides per day often find it uneconomical to sell this
waste since the by-product recovery value is exceeded by the handling
and transportation costs.
Most vegetable leather tanneries and a few chrome leather tanneries
remove hair from hides using a hair save operation. At a few of these
tanneries, the hair is washed, dried and baled, and subsequently sold
as a by-product. Most of these plants, however, merely screen out the
removed hair and dispose of it in landfills. A few plants allow the
hair to enter the general plant wastewater, which can result in
plugging of pipes, clogging and destruction of pumps, fouling of
clarifier sludge raking mechanisms and weirs, etc. Use of the hair
save method is declining in favor of the hair-pulp method. As noted
in Section III, however, some tanners still use a modified hair save
beamhouse which produces hair that is disposed of in a landfill. At
tanneries using the hair pulp method of hair removal, the hair is
dissolved and becomes part of the wastewater stream.
Some chrome leather tanneries, particularly split leather tanners
located in the northeastern U.S., generate large quantities of tanned
hide trimmings and shavings. This waste material can be sold as a by-
product. By-products are used in the manufacture of fertilizer,
chrome glue, hog feed supplement, and leather board, and provide an
energy source for steam production. The majority of this type of
waste, however, is disposed as solid waste.
A recent industry study estimated that the total quantity of solid
waste disposed in the land in 1974 was 203,000 metric tons.106 The
distribution of the total quantity of waste between the four major
waste types was as follows:
243
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Table 37
Industry Estimates for Land Disposal of Solid Wastes
Percent of
Type of Waste Quantity* Total Waste
Wastewater 122,000 60
treatment residues
(screenings 8 sludge)
Tanned hide trimmings 71,000 35
& shavings and leather
trimmings
General plant waste 6,000 3
Leather finishing 4,000 2
residues
*metric tons generated in 1974
Reuse and recovery with reuse are two technologies that will reduce
solid waste generation in wastewater treatment plants. Alternative
chemicals use may have similar results.
Pollution control applied to specific waste streams before all are
combined into a single total wastewater stream may produce a solid
waste, but the specific contaminants in the solids will generally be
known and in the most concentrated form. Such solid wastes are most
manageable in terms of proper control and disposal. Numerous small
quantities of solid waste of more concentrated composition may be less
economical to handle and transport, but will be much more
environmentally manageable than a single, large, dilute, and
multicontaminated solid waste. The latter would usually result from a
waste treatment system confined exclusively to end-of-pipe technology.
The primary contaminants of solid wastes from tanneries are chromium
and other heavy metals occurring in the wastewater, such as copper,
lead, and zinc. Repeated reuse of the chromium containing streams
and/or recovery and reuse will reduce chrome contamination of the
solid wastes. The other metals originate in the raw materials or as
corrosion products from the equipment in the tanneries. The former
can be controlled by changing raw materials or their composition, or
by eliminating the use of such raw materials. Alternative
construction materials for equipment would be the best solution to the
corrosion source.
Disposal Alternatives. Approximately 60 percent of the wastewater
treatment residues produced come from chrome leather tanneries with
primary and/or secondary wastewater treatment facilities, while 20
percent originate from chrome tanneries with secondary wastewater
treatment systems. Treatment plant sludge from chrome tanneries is
244
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normally dewatered prior to disposal. Sludge dewatering may^be
accomplished using gravity or mechanical means. Gravity dewatering
(sequential settling) is relatively uncommon; however, sludge drying
beds on the tannery plant site are used by some tanners. Mechanical
sludge dewatering is normally accomplished using vacuum filters,
centrifuges, or filter presses. These three mechanical dewatering
techniques have all been found to be effective in producing sludge
cakes ranging from 10 to 40 percent solids. There seems to be a
preference for filter presses due to the drier (40 percent solids)
filter cake produced.
Secondary wastewater treatment sludges from vegetable tanneries are
normally dewatered in evaporative lagoons, after which the sludge is
either used as a soil conditioner or disposed of in a dump or
landfill.
Sewer sump sludge is composed primarily of precipitated lime and is
not normally dewatered prior to disposal* Dumps and landfills are the
most common disposal facilities for this waste.
The different types of solid waste disposal facilities utilized and
estimates of the proportion of the total quantity of tannery solid
waste going to each type of facility are shown in Table 38. As shown,
nearly all tannery solid waste is disposed in landfills or dumps.
Trenches, lagoons, and certified hazardous waste disposal facilities
are currently used almost exclusively for sludge disposal. A small
percentage of tanneries operate their own disposal sites. Tannery-
owned disposal facilities are usually associated with vegetable
leather tanneries and are the result of the plant's remote location or
the fact that other disposal sites will not accept the solid waste.
Most tannery solid waste which is land disposed contains substantial
concentrations of trivalent chromium (up to several percent on a wet
weight basis) and, in many cases, copper, lead, and zinc as well. For
example, the "typical" concentrations of certain constituents in
tannery sludge are presented in Table 39. As shown, sludge from
vegetable leather tanneries is the only type which does not normally
contain significant heavy metal concentrations, unless concurrent
chrome tanning or retanning occurs at the same plant. The recent
trend toward chrome reuse or recovery would not be reflected in this
data and would suggest lower chrome concentrations in future sludges.
EPA believes that many of the toxic pollutants, especially heavy
metals, are removed with the sludge. There are no data available on
the fate of these pollutants or the actual distribution of these
pollutants between the solid and liquid phases. These toxic
pollutants would thereby become part of the solids to be disposed of
from leather tanneries. No analyses were made for toxic pollutants at
the time the data in Table 39 was generated, thus no additional
information is currently available regarding toxic pollutants in
sludges from leather tanning waste treatment. A substantial amount of
245
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Table 38
Disposal Sites Utilized
General Category of
Disposal Site
Landfill
Dump
Trenches or lagoons
Certified***
Specific Type of Disposal Site
municipal sanitary
private sanitary
municipal engineered*
private engineered
municipal converted**
private converted
on-site tannery
municipal
private
on-site tannery
municipal
private
on-site tannery
private
Percent of
Waste Disposed
60
3
3
5
10
20
1A
5
25
20
1
A
9
A
A
1
6
*Engineered disposal sites which do not provide daily cover
**Dumps which have been coverted to landfills without being engineered
***Certified hazardous waste disposal facilities
246
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Table 39
"Typical" Sludge Characteristics*
Constituent
Solids content
Chromium (mg/1)
Copper (mg/1)
Lead (mg/1)
Sulfides (mg/1)
Phenols (mg/1)
Chrome leather tannery
pre treatment /treatment sludge
before
dewatering
5-10
3,000-6,000
100-150
10-25
20-50
<10
after
dewatering
20-30
10,000-15,000
150-200
50-150
50-150
<10
Chrome leather
tannery sewer
sump sludge
(not dewatered)
5-15
2,000-4,000
100-200
10-25
30-60
<10
Vegetable leather
tannery secondary
treatment sludge
(not dewatered)
3-6
<5
<10
<5
25-50
-------
data will become available and will be considered prior to
promulgation of these regulations.
The fact that 60 percent of tannery solid wastes are waste treatment
residues and that the disposal sites reportedly used include a wide
variety°f types Su9itted facility. See 43 FR 185ol
(April 28, 1978). Finally, the proposed treater, storer, and disposer
standards would establish technical design and performance standards
for leather tanning waste storage facilities, and for landmis
basins, surface impoundments, incinerators, and other facilities wher4
such wastes would be treated or disposed, as well as security
contingency plan, employee training, recordkeeping, reporting
248
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inspection, monitoring and financial liability requirements for all
such facilities. See 43 FR 58946, 58982 (Dec. 18, 1978).
Hide and Leather Waste Alternative Uses
The following discussion was taken from a report prepared for the
Tanners Council of America (TCA), February 18, 1977.
The four use areas selected for analysis were chosen to consider as
broadly as possible all categories of solid waste and also several
types of initial processing (i.e., size reduction, incineration,
pyrolysis and hydrolysis). The use areas selected for analysis were:
1. Incineration of blue split and finished leather waste;
2. Fiberized leather for loose building insulation;
3. Pyrolyzed leather waste to make activated carbon and by-
product chemicals; and
4. Hydrolyzed leather and cattle hair to make leather and hair
meals for use in animal and pet foods.
Incineration. Incineration of various leather wastes with provision
for useful recovery of the released energy is a surprisingly
productive use for the materials. Leather is a "clean" fuel in the
sense that it contains virtually no sulfur. The heating value (dry
basis) is about 80 to 90 percent as much as that for a low-sulfur
Western coal.
The heating value of wet blue waste is naturally diminished somewhat
by the water present, but it still amounts to about 55 to 75 percent
of that for a low-sulfur Western coal. By burning the available
leather waste, a blue split tannery could save nearly all the money
now spent for coal or fuel oil to furnish the required process hot
water. The incinerators could probably be switched over to coal
without any problems when and if better uses for the waste leather
were developed, making this kind of venture essentially risk-free.
In addition to the recovery of energy, incineration of chrome tanned
leather waste also permits the recovery of a non-renewable resource,
chromium oxide. In one case, an ash from the incineration of chrome
tanned waste contained 2.23 percent hexavalent chromium. The
trivalent chromium (Cr^OJ) content of chrome tanned leather ash is
known to range from 13.5 to 58.3 percent.
The incineration ash would have a minimum value of about $200 per
contained ton of Cr2O3 on the basis of the current value of imported
chromite ore. If the ash could be upgraded to a pigment grade product
249
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(99-1- percent Cr2O3) , it could be sold for about $1 per pound as the
purified pigment.
on the basis of competition with a low-sulfur Western coal at $19 to
$21 per ton delivered in Chicago, blue leather waste would have an
approximate value of $11.75 to $15.75 per ton (dry basis). This value
takes account of the heat required to evaporate the water from the wet
waste. sale of the ash would add about $4 per ton to the realizable
valae of the blue leather waste by incineration, making the total
realizable value by incineration in the range of $16 to $20 per ton
(dry basis).
The capital cost (installed) of an incinerator handling about 1.2 tons
of waste per hour would be at least $600,000. such an installation
would furnish 8,645 Ib/hour (19,040 kg/hr) of steam.
"Poured" Insulation. Ground or fiberized leather waste has many
attributes which make it a good candidate material for use as a loose
insulation for residences and light commercial structures. It is
strongly resistant to environmental degradation and surprisingly
f^a S to ignition, even though it can be incinerated. A study
sponsored by the Tanners' Council of America found only one company in
the business of producing a fiberized leather product. There was no
indication of any effort to promote the material for insu^tion
pur pose s.
No measurements have been made on the insulation performance of
fiberized leather, but measurements of its apparent bulk density place
the material in the range of granulated cork and chopped cellulesic
insulation. The thermal conductivity of bulk leather is comparable to
o^i*°r P?perV a^in indicating that a fiberized leather material
should perform technically much like cellulosic insulation.
The chief problems to be dealt with in developing fiberized leather as
*£ .1^Ulati?n material are the cost of fiberizing and the requirement
that the product be odorless. Both of these problems can likely be
SOlKeK; KTh\ t0tai COSts for a f^erized leather product would
probably be about $110 per ton, which would be comparable with
cellulosic insulation at $240 per ton. y*±au±e wirn
The market for all insulation material has grown remarkably in the
last few years due to the rapid increase in the cost of all forms of
energy. The growth in the use of cellulosic insulation materials has
been at the rate of 34 percent compounded annually ove^the last few
years. It is believed that in 1976 the total market for cellulosic
sHoo ?onrnfab£Ut 30?'°°£ t0nS- This may be Compared with the
in'the un?ted°ltates?e ^^ "*** M±M tO be avai^ annually
250
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Activated Carbon. Upon heating leather waste to a temperature of 400
degrees C, a 50 percent yield of a hard granular char could be
obtained. This has been interpreted to mean that leather could be
converted in about this yield to a hard, granular, activated carbon.
Although there are three literature references during the last 20
years to making activated carbon from leather wastes, none of these
references noted that hard granules could be obtained. This is a
significant feature because hard granular activated carbon is a
premium material.
Activated carbon is manufactured commercially in the United States by
nine different companies. A new producer completed a semi-works plant
in 1976 and plans to complete a full scale plant in 1978. Production
will be based on a new proprietary one-step process in contrast with
the two-step processes used by the other producers. It has been
suggested that future work on the conversion of leather waste to
activated carbon should be directed toward the development of a one-
step process in view of the energy conservation possibilities in such
an approach.
The selling prices for granular activated carbons are in the range of
$0.40 to $0.50 per pound ($0.88 to $1.10 per kg). This is
significantly higher than the $0.10 to $0.12 per pound ($0.22 to $0.26
per kg) prices paid for powdered activated carbons. The price of a
granular carbon reflects both the absorption efficiency of the
material and its resistance to attrition in use (i.e., its hardness).
Activated carbons are also used to remove: tastes and odors from
potable waters; impurities and colored substances from sugar;
impurities from a great variety of chemicals; and harmful or odorous
substances from gaseous effluents. A small but well-known use is as a
component in cigarette filters.
The energy costs for charring leather wastes and then treating the
char to activate it are no doubt significant factors of unknown
magnitude. Capital costs are evidently also an important factor. The
volatile materials evolved in the carbonation process would at least
have value as fuel. It seems likely that the ammonia given off could
be advantageously recovered for use as fertilizer. The mixture of
volatile organic materials also evolved might have value as chemical
intermediates greater than their value as fuel.
Leather and Hair Meal for Feeds. Although both leather and hair are
protein materials, neither of them is digestible as such. Hydrolysis
will render each of them digestible, and both of the resulting meals
have been shown to be useful supplements in diets for swine and
poultry.
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Hair meal is very similar in amino acid composition to feather meal
which is a well-established ingredient in poultry diets. Therefore
feathe!remeal0 nutritional utility* hair meal is the full equivalent of
In the case of ruminants (sheep and cattle) , hair meal could be used
bPranS^L V?;rtually ^ of the nitrogen requirements of the animals
sheep and Yc^?.n° well-defin?d ^^o acid requirements. Because
sheep and cattle can use nitrogen from a number of very low cost
sources (urea, grass, alfalfa, etc.) it is believed that hair meal
would be too expensive for inclusion in their diets?
However, there is some danger that hair meals might be contaminated
"^^
attempt is made to Lrket haL *
Animal consumption of feather meal is currently 100,000 tons annually
^*>,ample s"pPlie.s available. Hair meals would compete directly with
feather meal, which sells for about $185 per ton. The cost of
recovering, washing, and drying hair amounted to $120 per ton ?n
making hair meal, the drying would not take place until "after
hydrolysis, so that hair preparation would be somewhat less £han $120
^"i T~OXl •
The basic costs associated with the conversion of hair to a dry meal
amount to about $65 per ton. The total costs ($180 per ton) are well
below the present ceiling of $300 to $340 per ton set by the current
selling price of feather meal. However, present protein prices are
high because the 1976 soybean crop in the United States was about 20
percent below the 1975 crop and the 1976 foreign crop III also below
expectations. At the same time, demand has remained strong!
Leather meal is permitted as a component in the diets of swine at a
i^te^ar^a^^V"118 is t0° Sma11 an amount to ««*e
p^T * i- U attractive as a component in swine rations
However, feeding tests with broilers indicated that 6 percent leather
meal in the diet afforded an economic advantage over ttrSntrolttrt
***«**<** ^-ther meal "and
Leather meal has not yet been approved for inclusion in poultry diets
s«fiS^.«%.5SG? a^if^-£s*jiissuajs
SETS srta' - -- "
252
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Dioxins are known to have been impurities in the chlorinated phenols
used as fungicides in the processing of hides into leather. Recent
advances in the manufacture of chlorinated phenols have led to great
reductions in the amounts of dioxins contained in these fungicidal
phenols. High temperature drying of hydrolyzed leather may also lead
to the conversion of the small amounts of chlorinated phenols in the
hides into dioxins. If this were the source of the dioxins, then the
formation of dioxins might be avoided by drying the hydrolyzed leather
sludge for a longer time at a lower temperature.
This use for leather meal has good economic prospects. The poultry
feed market in 1975 amounted to over 26,000 tons. If all this feed
were to contain 6 percent of leather meal, almost 1,600 tons of
leather meal could be used in this single application annually. This
is considerably less than the 80 thousand tons of chrome leather waste
previously referred to as being annually available in the United
States.
In view of the similarity between leather meal and meat scrap/bone
meal in respect to protein quality, it seems likely that leather meal,
free of dioxins, should sell at about the same price as meat
scrap/bone meal. Recent price quotations show that meat scrap/bone
meal (50 percent protein) sells for a little over $250 per ton. On
this basis, leather meal, containing as it does about 65 percent
protein, should sell for about $325 per ton. Leather meal today sells
for only $102.50 to $108 per ton.
Air Pollution
The major potential source of air particulate matter from a tannery is
from hide buffing operations. However, most tanneries control this by
wet scrubbing. Scrubber water is generally combined with the total
waste stream. Several tanneries are adding buffing dust to sludge
derived from liquid waste treatment for disposal.
In addition to process sources, tannery boilers can be a source of air
pollution. With proper design and maintenance of gas- and oil-fired
boilers, there should be no emission problems; however, with coal-
fired boilers, fly ash emissions are a problem. Fly ash emissions can
be kept to a minimum with proper design and operation. Dust
collection equipment may be used to further control air pollution.
Wet scrubbers or electrostatic precipitators are capable of providing
in excess of 98 percent removal of the fly ash. If a wet scrubber is
used, the waste dust slurry can be discharged to the wastewater
treatment system. Fly ash from the electrostatic precipitators can be
combined with the dewatered sludge for disposal.
Sulfide is the other potential air pollutant of consequence
originating from leather tannery wastes. The sulfide content of
tannery wastes must be reduced and maintained at a low level for
253
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biological treatment systems to work, to protect the health and lives
of workers exposed to leather tanning wastewaters, and to minimize the
potential for air pollution from any waste treatment system.
Imposition of BPT, BAT, BCT, NSPSr PSES, and PSNS will not create any
fr^f^a^ial *lr P°llution Problems. However, small amounts of
volatile organic compounds may be released to the atmosphere by
aeration systems in biological treatment. «»P"ere cy
Noise
Noise levels associated with wastewater treatment and control both in-
plant and at end-of-pipe are of no material significance as a specific
tannLgS?acm£es? ^ in°rease in the «»**«* noi^ levels in leather
254
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION
OF THE BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE—EFFLUENT LIMITATIONS GUIDELINES
GENERAL
The effluent limitations which were required to be achieved by July 1,
1977, are based on the degree of effluent reduction attainable through
the application of the Best Practicable Control Technology Currently
Available (BPT). The BPT technology is generally based upon the
average of the best existing performances by plants of various sizes,
ages and unit processes within the industry. This average is not
based upon a broad range of plants within the leather tanning and
finishing industry, but has been derived from performance levels
achieved by exemplary plants. In industrial subcategories where
present control and treatment practices are uniformly inadequate, a
level of control higher than any currently in place may be required if
the technology to achieve this level can be practicably applied.
BPT emphasizes not only treatment facilities at the end of
manufacturing processes, but includes control technologies within the
process itself, if such in-plant control technologies are considered
to be normal practice within an industry.
In establishing BPT effluent limitation guidelines, EPA must consider
several factors, including:
1. the manufacturing processes employed by the industry;
2. the age and size of equipment and facilities involved;
3. the engineering aspects of application of various types
of control techniques;
4. the cost of achieving the effluent reduction resulting
from the application of the technology; and
5. non-water quality environmental impact (including
energy requirements).
The BPT regulations promulgated by EPA on April 9, 1974 (39 FR 12958)
were remanded by the United States Court of Appeals in Tanners'
Council of America v. Train, 540 F.2d 1188 (4th Cir. 1976). The Court
held, among other things, that: 1) the Agency's basis for technology
transfer from the meat packing industry to the leather tanning and
finishing industry was not supported by the record, and 2) EPA's
255
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consideration of seasonal variability in effluent concentrations and
tne need for cold climate adjustments was inadequate.
MANUFACTURING PROCESSES
As indicated in earlier sections, there are differences in tanning
processes which result in varying raw waste characteristics. The
Agency has recognized these variations by establishing seven major
industry subcategories for effluent limitations.
AGE AND SIZE OF EQUIPMENT AND FACILITIES
As indicated in Section IV of this report, no significant data
substantiate the claim that tannery age or size justifies different
o"!^n^ limit
-------
substantial tannery waste. It also allows a certain degree of
positive control of the treatment parameters if necessary because of
waste characteristics, loadings, or ambient conditions.
It must be noted that low solids aerated lagoons are not considered to
be equivalent to this BPT technology since these systems perform
poorly during the winter months in northern climates. Plants using
these systems will be required to upgrade their treatment facilities
to achieve the BPT effluent limitations on a consistent basis.
Extensive data now in the record also show that, for the pollutants
regulated by BPT, winter climate does not affect the performance of
properly designed and operated extended aeration activated sludge
systems. These systems have been demonstrated in the leather tanning
and finishing industry and technology transfer from meat packing or
any other industry is no longer required.
Development of the Limitations
The pollutants controlled by this revised regulation include the same
pollutants controlled by the remanded BPT regulation, specifically
BOD5, TSS, oil and grease, pH, and (total) chromium. The discharge of
these pollutants is controlled by mass effluent limitations (kg/kkg or
Ibs per 1,000 Ibs of raw material). The Agency calculated the mass
limitations using demonstrated effluent concentrations, average water
use data for the individual subcategories (see Section V), and the
appropriate variability factors to establish maximum monthly average
and maximum day values. Since the mass effluent limitations are based
on flow, these values vary among the subcategories.
Sixty months of operating data from the activated sludge system at
tannery no. 47 has been statistically analyzed, excluding data from
two brief periods of upset. Based upon this analysis, EPA established
the maximum average concentrations for a 30-day period for the
parameters regulated under BPT as follows: BOD5 - 90 mg/1, and TSS -
145 mg/1. Results of analysis of operating data from the Berwick,
Maine POTW (excluding data from the initial start-up and operator
familiarization period and periods of upset or mechanical
difficulties) serve as the basis of limitations for oil and grease -
25 mg/1, and (total) chromium -3 mg/1. The effluent concentrations
listed above are the same for all subcategories, and therefore the
differences in average water use (gallons/pound of hide) determine the
differences in mass effluent limitations.
The 30-day maximum effluent concentrations presented above are
approximately 1.5 times greater than the long-term average for these
parameters, as observed at tannery no. 47. The variability analysis
of this data indicated that the ratio of maximum daily concentration
to maximum 30-day average concentration is approximately 2.0. This
ratio was used to calculate the mass effluent limitations reflecting
the maximum value for any one day. It is noteworthy that these
257
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effluent concentrations were achieved on a year-round basis-
necessary! Varianoe ** Winter °Pe"tio" in «" cH»a?ee it no^
ENGINEERING ASPECTS OF CONTROL TECHNIQUE APPLICATION
The specific level of technology defined as BPT is practicable because
SiS h^thVann?£Y tnaaatfy already practice it; other industries
with high strength wastes use it also. Data from tannery no 47
(subcategory No. 3) and the Berwick, Maine POTW, which receives
er°ma- 5°
for theBTefauenr- ^"*** «o. 4, served as thbas
tor the BPT effluent concentrations. Performance of the treatment
system at plant no. 253 (described in section VII) supports thlse
limitations, since it achieves effluent levels well below thole
"
acceedpLs* mtsT- ^ ve^etable Banning plns have
identical to ?££ W^h require effluent concentrations virtually
identical to those noted above. The Hartland, Maine POTW which
treats more than 90 percent tannery wastewater, achieves effluent
Fiae-101 *" • ^nerallV l««r tha thos notd abve
(Figure 32). Differences in raw waste loads among subcateqories can
activatedn^nf ^-^ ^^^ ^signed coagulation-sedimtion and
activated sludge units. Transfer of technology from other industries
such as meat packing, is no longer necessary to es?abUsh emuln^
limitations for leather tanners. For the other direct discharaers
waste control and treatment is uniformly inadequate? and required
transfer of BPT technology and performancl to the reSlna
subcategories. Most of the existing biological treatment sys^ms in
the industry are inadequate. For example, some of the plants^ Tl) do
euiPment necessary to be oerae '
e^ S e?uPment necessary to be operated as high' solids
extended aeration activated sludge; (2) are overloaded activat^
As noted in the discussion in Section VII, high solids extended
:ssr ^^t^g:^ovtfs^
oraej For tannery wastii treatlVwIth
?Lurf fo trea*ment caPac^y and should thus represt a ™ximUm"ost
figure for any tannery. Some of the important design factors are:
258
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200i
175-
SLUDGE BULKING
(HIGH FLOW)
SLUDGE BULKING(YOUNG SLUDGE)
AND SAND FILTER START-UP
Figure 32. Average Monthly Final Effluent Concentrations
of BOD5^ TSS, and Chromium (Total) from an
Activated Sludge System in a Northern Climate
(Hartland, Maine POTW)
259
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Equalization Detention: 36 hours
at design flow
Primary Sedimentation Overflow Rate: 29 m3/d/m2
(700 gpd/ft2)
Aeration Basin F/M 0.05-0.1
Ratio
Mixed Liquor 6000-10,000 mg/1
Suspended Solids (MLSS)
Sludge Age 20-30 days
Oxygen Delivery 2.5 kg/kg BOD5 in influent
to basin
Nutrient Balance: Carbon: Nitrogen:
Phosphorus - 100:5:1
Secondary Clarification Overflow Rate: 8 m3/d/m2
(200 gpd/ft2)
The importance of diligent operation has been demonstrated in at least
two cases. An activated sludge system at Tannery No. 237 in Minnesota
. n n
as Tsf ma/1 to* ^ "^ ?«"****"™ *lch varied from as high
m^o I 9 4.- S 10W as 8'8 mg/1' Bending upon the experimental
mode of operation. During the first year (1976) of operation of a
fi e ,:
IoD5°fffl°f .time1'^Utvi?tter °P«*«ti»3 skills nave maintained avlrage
BOD| effluent quality below 80 mg/1, except for periods of operational
difficulties (i.e., inoperative clarifiers, etc.). Therefore the
basic feasibility of the activated sludge process and the imwrtancf
of operational control have been firmly demonstrated. importance
COST AND EFFLUENT REDUCTION BENEFITS
EPA expects that the total capital investment necessary to upgrade the
effluent* limita"3'^ ^ 18 direct. dfschargers not achieving BPT
costs for all of these plants will increase by^^S^llion^er^Sr6
Achievement of proposed BPT effluent limitations wil! remove
approximately 54 million pounds per year of conventional pollutant!
260
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300
250
200
o 150
o
z
o
o
L_ 100
y.
u.
bJ
50
PRIMARY B SECONDARY CLARIFIERS
"OUT OF OPERATION
PRIMARY
CLARIFIER
OUT OF
OPERATION
SLUDGE
BULKING
DJFMAMJJ ASONDJ FMAMJ JASONDJFMA
76"77' '78* '79*
Figure 53 Average Monthly BODc & TSS Effluent Concentration
from an Activated Sludge System in a Northern Climate
(Berwick, Maine POTW)
261
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o
PU
K)
NOUVaiN30NOO
262
-------
(BOD5, COD, TSS, and Oil and Grease), 284,000 pounds per year of
chromium, 374,000 pounds per year of sulfide, 100,000 pounds per year
of TKN, and significant quantities of other toxic pollutants in
leather tanning and finishing wastewaters. EPA believes that these
effluent reduction benefits outweigh the associated costs.
NON-WATER QUALITY ENVIRONMENTAL IMPACT
Unrecovered waste products removed from tannery discharges or from
processing steps within the tannery take the form of general tannery
solid wastes or waste sludges from treatment facilities. EPA
estimates that the proposed BPT effluent limitations will contribute
an additional 22,000 metric tons per year of solid waste in the form
of sludges from upgraded wastewater treatment systems. The major non-
water quality impact of these wastes is the increased burden on ^the
land to accept their disposal. Waste trimmings and hair from hides
are presently recovered as by-products. Recovery and reuse of chrome
in some tanning operations will substantially reduce chrome levels in
waste sludge produced by the treatment facility. In addition, this
will reduce the potential release of toxic chrome due to the use of
dewatered sludge at landfills. In all cases, however, dewatered
sludges from chrome tanneries need separate handling at disposal sites
in order to avoid any potential difficulties. Proper landfill siting
and operation will minimize the impact of tannery waste disposal on
the land. See Section VIII for a discussion of how RCRA will impact
upon the handling and disposal of tannery solid wastes.
EPA has estimated that the energy required by a typical plant to
achieve BPT effluent limitations is approximately 1 percent of the
total energy consumed for production purposes. This estimate is based
upon the total energy used by the industry from all fuel sources for
production purposes as documented in the 1972 Census of Manufacturers.
The bulk of this increased energy usage is for aeration equipment
operation.
APPLICATION OF BPT EFFLUENT LIMITATIONS
1. If a tanner processes hides in more than one subcategory (e.g.,
cattlehides and shearlings), the effluent limitations should be pro-
rated based on the percentage of the total hide weight being processed
in each subcategory.
2. The production figure recommended for applying these limitations
is the daily average production of the maximum 30 consecutive days.
BPT EFFLUENT LIMITATIONS
Based on the rationale outlined above, mass effluent limitations
(kg/kkg or lb/1000 Ib) for the seven subcategories established for the
leather tanning industry are presented in Table 40.
263
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Table 40
BPT EFFLUENT LIMITATIONS
Subcategory One - Hair Pulp/chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BPT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive davs
Mass Units - kg/kkg (or lfc/10QQ m of raw matieria1
BOD5
TSS
Total Chromium
Oil and Grease
PH
7.0
11.2
0.24
2.0
3.5
5.6
0. 12
1.0
Within the range of 6.0 to 9.0 at all times.
Subcategory Two - Hair Save/Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BPT Effluent Limitation^
Maximum for Average of daily
any one day values for 30
consecutive
Mass Units - kg/kkg for ihxmnn ib) of raw
BOD5
TSS
Total Chromium
Oil and Grease
PH
8.2
13.4
0.28
2.2
4. 1
6.7
0. 14
1.1
Within the range of 6.0 to 9.0 at all times.
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Subcategory Three - Hair Save/Non-Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BPT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BOD5
TSS
Total Chromium
Oil and Grease
pH Within the
6.0
9.6
0. 20
1.7
range of 6.0 to
3.0
4.8
0.10
0.83
9.0 at all times.
Subcategory Four - Retan-Wet Finish
Pollutant or
Pollutant Property
EPT Effluent Limitations
Maximum for
any one day
Average of daily
values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BOD5
TSS
Total Chromium
Oil and Grease
pH
2.6
4.2
0.086
0.70
1.3
2. 1
0.043
0.35
Within the range of 6.0 to 9.0 at all times.
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Subcategory Five - No Beamhouse
Pollutant or
Pollutant Property
BPT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecuti
d<
Mass Units - kq/kkg (or lb/1000 Ib) of raw
BOD5
TSS
Total Chromium
Oil and Grease
PH
5.0
8.0
0. 17
1.4
2.5
4.0
0.083
0.69
Within the range of 6.0 to 9.0 at all times.
Subcategory Six - Through-the-Blue
Pollutant or
Pollutant Property
BPT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkq (or lb/1000 Ibl of raw
BOD5
TSS
Total Chromium
Oil and Grease
PH
4.0
6.6
0. 14
1. 1
2.0
3.3
0.068
0.56
Within the range of 6.0 to 9.0 at all times.
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Subcategory Seven - Shearling
Pollutant or
Pollutant Property
BPT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BOD5
TSS
Total Chromium
Oil and Grease
PH
20. 8
33.6
0.70
5. 8
10.4
16.8
0.35
2.9
Within the range of 6.0 to 9.0 at all times
267
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE—
EFFLUENT LIMITATIONS GUIDELINES
GENERAL
The effluent limitations which must be achieved by July 1, 1984, are
not based on an average of the best performance within an industrial
category. Instead, they are based on the very best economically
achievable control and treatment technology employed by a point source
within the industrial category or subcategory, or by another industry
from which technology is readily transferable. BAT may include
process changes or internal controls, even when not common industry
practice.
Best available technology economically achievable (BAT) emphasizes in-
process controls, as well as control or additional treatment
techniques employed at the end of the production process. In
developing BAT effluent limitations EPA also considered:
1. the manufacturing processes employed;
2. the age and size of the equipment and facilities involved;
3. the location of manufacturing facilities;
4. process changes;
5. the engineering aspects of the application of various types
of control techniques;
6. the cost of achieving the effluent reduction resulting from
application of the technology; and
7. non-water quality environmental impact (including energy
requirements).
The BAT technology level considers those processes control
technologies which at the pilot plant, semi-works, and other levels,
have demonstrated sufficient technological performance and economic
viability to justify investing in such facilities. BAT represents the
highest degree of demonstrated control technology for plant-scale
operation, up to and including "no discharge" of pollutants where
feasible. The costs of this level of waste control are defined by
top-of-the-line of current technology, subject to limitations imposed
by economic and engineering feasibility. Technical risk may exist
with respect to performance and certainty of costs and some
269
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«d adaptation before
MANUFACTURING PROCESSES,. AND SIZE, AGE AND LOCATION OF FACILITIES
The processes employed in different sized tanneries within earh
PROCESS CHANGES
isolation and collection for trea^enr^ °% ^:?lant waste stream
the recommended effluent limitaSons" ^ facilltate achievement of
considered such chanaes and l^ • ®wei:o"s tanneries have
experimental work has teln conductedL
IDENTIFICATION OF BAT TECHNOLOGY
sedimentation) and Level
270
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sludge system with nitrification) technologies are the basis for BPT
effluent limitations. Additional technologies considered BAT are
presented below.
In-Plant Control and Preliminary Treatment
Level 1 - Water conservation and reuse to reduce flow
(all subcategories)
- Stream segregation for preliminary treatment
(subcategory nos. 1, 2, 3, 6, and 7)
- Ammonia substitution in deliming
(subcategory nos. 1, 2, 3, and 6)
- Chrome recovery and reuse
(subcategory nos. 1, 2, 5, 6, and 7)
- Sulfide liquor reuse followed by catalytic oxidation of
residual sulfide (subcategory nos. 1, 2, 3, and 6)
- Fine screening of segregated streams (all subcategories)
Level 2 - Flue gas carbonation and sedimentation for
beamhouse wastewaters (subcategory nos. 1, 2, 3, and 6)
A schematic diagram of these technologies for all seven subcategories
is presented in Figures 4 through 8 (Section VII). The end-of-pipe
technologies which follow are applicable to all subcategories (Figure
9).
End-of-Pipe Treatment
Level 5 - Addition of powdered activated carbon (PAC)
to upgrade extended aeration-activated
sludge (Level 4)
Level 6 - Multimedia filtration
Level 7 - Granular activated carbon columns
Level 4A - Alternative Technology - Physical/chemical treatment
Table 41 tabulates the long term performance of BAT technologies for
each subcategory, starting with raw waste loads and continuing through
segregated stream in-plant control and preliminary treament, combined
stream end-of-pipe primary and secondary biological treatment, and
advanced waste treatment.
The Agency considers physical/chemical treatment (Level 4A in Figure
9), an alternative technology for direct dischargers, enabling them to
achieve an effluent quality equal to that produced through Level 6
(multi-media filtration). This technology can be applied after Level
3 by direct dischargers. The existing biological treatment systems of
direct dischargers which exhibit poor performance can be upgraded with
physical/chemical treatment to achieve the desired effluent quality.
271
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"**? 1O**S m P«dicated on demonstrated flow
££ =,
DEVELOPMENT OF BAT EFFLUENT LIMITATIONS
BAT Reduced Flow
EPA analyzed the log-normal distribution of the wastewater flow data
for each subcategory to determine the geometric mean »„* ? * ,
=="s £•* ~
osof Ascribed above
flow.rate c^puted for each subcategory was then compared to
The ke °
1
rates employed to evaluate BA?' technology? SUmma"ZeS the reduc^ "ow
272
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. C« O
o a -* .o
eno^t"-. «
. 00 CM 00
SO i-l • i-l
m i-i o eo •
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-------
Table 42
SUMMARY OF REDUCED SUBCATEGORY FLOWS FOR BAT
Total Number Number of Plants
of Plants Reduced Flow Operating at
ReDortina Flow aal/lb (1/kcr) Reduced Flow
One
Two
Three
Four
Five
Six
Seven
31
12
16
8
14
2
3
3.5
3.7
2.7
1.3
2.3
2.5
11.0
(29)
(31)
(23)
(11)
(19)
(21)
(92)
11
1
4
2
5
1
1
Raw Waste Loads
The mean values for wastewater flow (gal/lb of raw material) and raw
waste loads (kg/kkg raw material) reflect the geometric mean of the
log-normal distribution for each parameter. Subcategory Six (Through-
the-Blue) required a different approach because of limited
information. Raw waste loads for each pollutant parameter relating to
this subcategory were derived by subtracting from subcategory no. 1
raw waste loads the subcategory no. 4 raw waste loads, since through-
the-blue plants are exactly the same as hair pulp, chrome tan, retan-
wet finish plants (subcategory one), but without retan-wet finish
operations (subcategory four).
In computing the raw waste concentrations to reflect the reduced
flows, the pollutant load measured in kg/kkg remained constant. This
was done because while available data for this industry does show
trends in pollutant reduction, these data do not conclusively confirm
that reduced water contact with the product concurrently produces
reduced pollutant loads. With a constant pollutant load and a reduced
flow per unit of production, the calculated pollutant concentration
(mg/1) predicted by this methodology is greater for each parameter
than the BPT values. The BAT raw waste characteristics are shown in
the second column of Table 41, which provides a comparison with the
current average subcategory waste concentration listed in the first
column. These results represented the expected average raw waste
characteristics used in the engineering analysis of BAT technology.
BAT Treatment Technology
EPA developed the BAT effluent limitations in building block fashion,
basing pollutant control levels on BPT technology (primary treatment,
secondary biological treatment). Individual unit treatment processes
included as a part of in-plant control and preliminary treatment are
281
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discussed in section VII and are identified (above) as BAT
Y, EP?' Althou9h Plants in the industry have used
treatment processes, the combination of all of the
processes utilized for this regulation has not been demonstrated.
Starting from raw waste loads (lbs/1,000 Ibs) determined for each
^v^ory, including pr°ven flow red«<*ions, the performance of each
of the unit treatment processes was applied to reduce these loads in
the appropriate sequence (Level 1 and 2) for the segregated waste
«M ???*•• rV^* St^ ln thlS analvsis Portrayed in Table «fwas to
utilize industry data discussed in Section VII on the proportions of
flow and pollutant loads separately attributable to beamhouse
operations and tanyard, retan-wet finish operations, so that the
effect of segregated stream pretreatment technologies can be
subsequently established. The raw waste load flow (gll/lt? and
Sect?orvii^d '^'T^ lbl Portions (summarized 'in Table fSf
f? £?/•»! applied to BAT raw waste loads for each subcategory
(labeled -Raw Waste Load with Reduced flow" in Table U1) to yield
separate flow (gal/lb) and pollutant loads (lb/1,000 lb) for these two
f reap3' 2nd caiculated concentrations (labeled '-Raw Beamhouse Stream"
anard tr631"" in Tafcle »- As an example, subcategory
toTable35
Beamhouse:
Tanyard:
3.5 gal/lb x 0.4 = 1.4 gal/lb
3.5 gal/lb x 0.6 = 2.1 gal/lb
Similarly, BAT raw waste load BOD5 would be segregated as follows:
Beamhouse:
Tanyard:
62.3 lb/1000 lb x 0.65 = 40.5 lb/1000 lb
62.3 lb/1000 lb x 0.35 = 21.8 lb/1000 lb
Remaining parameters were caluclated in the same manner. The "Raw
Beamhouse Stream" mass loadings were then subjected to Level 1
technology (sulfxde oxidation) to completely remove sulf ides and level
2 technology (flue gas carbonation-sedimentation) to reduce excels
I InT Vr e.n ^ n0tSd ^der "Percent Removals' For Treatment levels
? .: Beamhouse" in Table 35. For the same subcategory No 1
example, the raw beamhouse stream would be reduced by sul?lde
residuals: ** flUG ^ Carbonation efficiencies to th^f ollowing
BOD5
Sulfide:
40.5 lb/1000 lb x (1.0-0.6) = 16.2 lb/1000 lb
2.47 lb/1000 lb x (1.0-1.0) = 0.0 - complete removal
Remaining
resulting
parameters were calculated in the same manner. The
wastewater characteristics (lb/1,000 lb - calculated
Beamhouse Stream" "f
tohereova o
substitution as discussed in Sectiovil
282
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under "Percent Removals For Treatment Levels 1 and 2 - Tanyard." Again
for the subcategory No. 1 example, the raw tanyard stream chromium,
ammonia, and TKN would be reduced as follows:
Chromium: 2.9 lb/1000 Ib x (0.8) = 2.32 lb/1000 Ib captured
2.9 lb/1000 Ib x (1-0.8) = 0.58 lb/1000 Ib discharged
Ammonia: 3.98 lb/1000 Ib x (1-0.67) = 1.33 lb/1000 Ib discharged
3.98-1.33 = 2.65 lb/1000 Ib removed by substitution
TKN: (6.8 - 2.65) lb/1000 Ib = 4.15 lb/1000 Ib
No reductions were made for other parameters. The resulting
wastewater characteristics (lb/1,000 Ib - calculated concentrations)
are presented under "Treated Tanyard Stream" of Table 41.
The next pretreatment technology applied is coagulation-sedimentation
of combined streams (Level 3) which is a part of BPT technology.
Influents to combined stream pretreatment were calculated by adding
the flow (gal/lb) and mass loadings (lb/1,000 Ib) under "Treated
Beamhouse Stream" and "Treated Tanyard Stream" to yield "Level 2
Primary Influent." For the subcategory No. 1 example, flows were added
as follows:
Treated Beamhouse flow + Treated Tanyard flow = Combined
flow to Level 3
1.4 gal/lb + 2.1 gal/lb =3.5 gal/lb
Pollutant loadings were calculated as follows:
Beamhouse + Tanyard = Combined load to Level 3
BOD5: 16.2 lb/1000 Ib + 21.8 lb/1000 Ib = 38 lb/1000 Ib
Ammonia: — + 1.33 lb/1000 Ib = 1.33 lb/1000 Ib
Chromium: — + 1.58 lb/1000 Ib = 0.58 lb/1000 Ib
Sulfide: 0.0 + =0.0
It is noteworthy to compare the water use and pollutant mass loadings
of this column of Table 41 to the first column of Table 41, "Existing
Average Raw Waste Load." Application of Levels 1 and 2 technology to
BPT systems, accomplish major reduction in the waste load treated by
BPT technology (Level 3 and Level 4). For example, in subcategory
one, flow is reduced by approximately 25 percent; BODJ5 load reduced by
approximately 40 percent; TSS load reduced by approximately 45
percent; COD load reduced by approximately 75 percent; and ammonia
load reduced by approximately 67 percent. It is on this basis that
engineering estimates were made of the reduced long-term average
treated effluent concentrations as a result of the addition of in-
plant control and preliminary treatment (Levels 1 and 2) as a part of
BAT technology. The starting points of these engineering estimates
were the BPT effluent limitations that were based upon plant
performance (see Section IX). EPA estimates conservatively that the
long-term final effluent concentration for BODJ5 will be reduced from
60 m/gl to 40 mg/1; TSS will be reduced from 95 to 60, where effluent
283
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eterdn bh V tO 1; COD Concentration was
determined by the relationship between COD and BODS (Fiaure 1» -
ammonia removal by nitrification will be improved from nil to 10 J/i
determined gTtJS"7 aC*iev*A *" Plant <">• 253; TKN concentration was
«h^f 2 f by.the approximate 4:1 ratio to ammonia generally noted
.
oftheles
,
related to the improved TSS performance expected at thi level" phenol
BOD5), were not precisely calculated through use of availahii
»
Engineering analysis established the performance of additional
a
284
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nitrification by biological treatment is improved and where the
performance of plant no. 253 approaches this concentration without the
influence of PAC; TKN concentration will be reduced from 40 mg/1 to 20
mg/1 in keeping with the 4:1 ratio of to ammonia; and phenol will be
reduced from 0.25 mg/1 to 0.1 mg/1 by enhanced biological treatment,
with this concentration being achieved by well run biological
treatment systems in the petroleum refining industry and in some cases
by plants in the leather industry.
Suspended solids remaining in BAT OPTION TWO effluents were then
treated through a system of multi-media filtration transferred ^from
numerous other industrial and municipal applications. The primary
treatment accomplished by multi-media filtration is control of
suspended solids, including residuals of insoluble chromium. EPA
estimates that TSS concentrations will be reduced by approximately 35
percent from 25 mg/1 to 16 mg/1, where consistently lower effluent
concentrations of 10 mg/1 have been noted in other applications;
chromium will be reduced by an amount similar to TSS from 0.5 mg/1 to
0.33 mg/1, where effluent concentrations as low as 0.17 mg/1 have been
reported in the leather industry (see Table 37) without the use of
filtration. The literature notes that application of filtration
technology also removes BOD probably associated with TSS. EPA
estimates that approximately 30 percent of the BOO5 will be removed,
from 20 mg/1 to 14 mg/1. The COD concentration associated with this
reduction is determined by the COD to BODJ3 relationship (see Figure
3) . In concert with BODj> removal, a small reduction in oil and grease
will be accomplished, from 10 mg/1 to 6 mg/1; effluent concentrations
as low as 5 mg/1 have been reported. It is also estimated that a
small removal of TKN concentration will occur, from 20 mg/1 to 15
mg/1; this is due to the removal of residual proteinaceous solids
(TSS). No further reductions are made in either ammonia or phenol
because biological treatment does not occur in filtration. The
resulting effluent quality (Table 41) was the basis for BAT Option
Three - Level 6.
Finally, the performance of granular activated carbon (GAC) columns in
pilot plant and additional limited industrial application was applied
to the effluent quality resulting from BAT Option Three - Level 6,
with the resulting final effluent quality (Table 41) serving as the
basis for BAT Option Four - Level 7. The final effluent
concentrations were based largely upon reported concentrations in
other applications with similar treatment preceding GAC columns.
The mass effluent limitations presented in Table 43 for the seven
subcategories are based on BAT Option Three - Level 6. EPA selected
this option because it provides significant removal of the toxic
pollutants of concern in the leather tanning industry (primarily
phenol and substituted phenols, and chromium and other heavy metals)
by in-plant control, pretreatment, and end-of-pipe treatment.
Although the Act does not require a balancing of costs against BAT
effluent reduction benefits, the costs of the technology options
285
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ssssr
.tl
S£i
optimal*0"3 ^^ °peration and "-aintenance procedures mly not be
EPA considers physical/chemcial treatment technology (Level «A) an
L^eT 6°r dM r^d^Char9erS t0 Pr0<3uce an *«l«ent quality equal to
or foll^ina M f ^ls=h«gers can apply this technology after Level 3
or following biological treatment to achieve BAT effluent quality.
trL^' SamPlf bef°re C6aSing °Peration- "ad physical/chemical
an Sf? * ^ Pla°e WhiCh achieve<3 l°«er effluent concentrations for
all pollutant parameters (both indicator and toxic ixxLlutan^ ^
Data Variability
Long-term performance is the basis for all of the reductions and
rss ^s-«:rjs2sr.s S£sr% snsiH
Table 43 shows the BAT effluent limitations as mass units
-------
procedure was COD. For the BAT effluent limitations, residual COD was
computed from the BOD5 to COD relationship (Figure 3) presented in
Section VII.
REGULATED POLLUTANTS
The BAT effluent limitations proposed for the leather tanning industry
focus on three major groups of pollutants:
1. Non-toxic, non-conventional pollutants. The non-toxic,
non-conventional pollutants limited by BAT (ans NSPS) include total
Kjeldahl nitrogen (TKN), ammonia, and sulfide. As noted below, these
pollutants serve as "indicator" pollutants for the removal of toxic
pollutants, except for sulfides. These pollutants are subject to
numerical limitations expressed in Ibs per 1000 Ibs of raw material.
2- Toxic pollutants. The toxic pollutants expressly controlled for
direct dischargers in each subcategory are phenol and chromium, which
are subject to numerical limitations expressed in Ibs per 1000 Ibs of
raw material. Since the EPA has adopted the control of "indicator"
pollutants as the basis for controlling toxic pollutants, no effluent
limitations are recommended for any toxic pollutants other than
chromium and phenol.
3. Indicator pollutants. The difficulties of toxic pollutant
analyses have prompted EPA to propose a new method of regulating
selected toxic pollutants. Historical data and inexpensive analytical
methods are limited for certain toxic pollutants. Therefore, EPA is
proposing numerical limitations on "indicator" pollutants for which
there is substantially more data; these include BOD5, COD, TSS, oil
and grease, TKN, ammonia, (total) chromium, and (total) phenol. The
data available to EPA revealed that when these indicator pollutants
were controlled, the concentrations of toxic pollutants were
significantly lower than when indicator pollutants were present in
high concentrations. Moreover, the treatment systems existing in the
industry were designed for removal of conventional and nonconventional
pollutants.
EPA's consideration of "indicator" limitations was brought to the
attention of Congress during the formative stages of the Clean Water
Act of 1977. At that time, EPA was examining several techniques to
alleviate the difficulties of lengthy and expensive analytical
procedures. The proposed alternate "indicator" limitations serve that
purpose. This method of toxics regulation obviates the difficulties,
high costs, and delays fo monitoring and analyses that would result
from limitations solely on the toxic pollutants.
Quotations recently obtained from a number of analytical laboratories
indicate that the cost of each wastewater analysis for organic toxic
pollutants ranges between $650 and $1,700, excluding sampling costs.
Even if cost were not such a factor, the availability of laboratory
287
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ths stubeganW°Ulf ^fuT6? •*Ut*»»l constraints. When
sophisticated Sment could oerfo™ te?hnician ""ng the mos?
analysis in an 8-h^ work dav ^rl, °nly °ne complete organic
commercial laboratories in the" n£?JS V6r' t?ere were only ^oiit 15
n e n
capability to perform these Lalysef Todaf thf^ SU"icient
commercial laboratories known to EPA which hfve ^! ar«.f^out 5°
perform these analyses and <-he ™™vL . ™ nave the capability to
such capability alsTfncreases? ^ci^c^S^8^ bee""6 *"""?
^j-a.j.^ieiicy aiso nas been improving.
be effectively controlled by' limitation o 6S^hat.th?se Pollutants can
even though the toxics (other than oheno? ln^icator. Pollutants
expressly regulated by numerica^limitations chromium) are not
inorganic compounds. An indicator for 9?h» c°mP°unds, and the
compounds is "total phenol" as mtaanrS h substituted phenolic
method (KAAP) . This mpth^rl ™ measured ^bV the 4-aminoantipyrine
.
TKN, and ammonia) are controlled *h?« pollutants (especially COD,
resistant to rapid bLdegrfdatfon wUl
"
w
Similarly, EPA concludes tha contro of z?nr ? *f aS wel1'
copper is accomplished by a sDecif£> if™T«.J?- ' d' nicke1' an
by control of TSS as an indicator ^uitant °" tOtal chromi™. ™
Many of the toxic organic compounds are known to be resistant
^S"1, cS«rsL,?s, s-insssf f;r ^ » : s™
"
»
determined by a traditional and ^a" ^e /apidly and reliably
method. traditional and relatively inexpensive analytical
non-conventional pollutant of
pollutants are therefore l
288
-------
It should be noted that some of the indicator pollutants, such as
BODS, COD, TSS and oil and grease, are classified as "conventional"
pollutants under Section 304 (a) (U) of the Act or proposed regulations.
Where conventional pollutants serve as "indicator" pollutants for
toxic pollutants, BAT limitations for these pollutants have been
established to assure installation of waste treatment technology
adequate for the removal of toxic pollutants. In such cases, the
"indicator" limitations on conventional pollutants will be established
regardless of the BCT test. Furthermore, some of the "indicators" are
nonconventional pollutants. These non conventional "indicator"
pollutants will not be subject to economic and water quality
modifications under Sections 301 (c) and (g) of the Act. Exceptions
may be justified. A specific discharger may attempt to show that his
waste stream does not contain any of the toxic pollutants that a BAT
effluent limitation on a conventional or non-conventional toxic
"indicator" was designed to remove. If this can be shown, then a
limitation on a conventional pollutant would be subject to the BCT
cost test, and a limitation on a non -conventional pollutant would be
subject to requests for modifications.
The Agency is also considering the possibility of establishing
numerical limitations (either in concentration or mass units) for the
following toxic pollutants: phenol (by GC/MS methods), 100 yg/1:
2,4,6-trichlorophenol, 50 pg/1; pentachlorophenol, 25 pg/1; lead,
250 pg/1; zinc, 250 pg/1; cyanide, 500
The numerical limitations under consideration for phenol (100 pg/1) ,
2,4,6-trichlorophenol (50 pg/1) , and pentachlorophenol (25 pg/1) are
based upon the structure, known chemical properties, and available
treatability data for these compounds as developed by Strier.107 These
are considered to be 30 day average concentrations based upon combined
activated sludge - powdered activated carbon biological treatment. 108
The numerical limitations being considered for lead (250 pg/1) , zinc
(250 ng/1) , and cyanide (500 jjg/1) are based upon their treatability
as indicated by data developed during the sampling and analysis
program for this industry. Strier «s limitations developed were
higher108: lead and zinc - 500 pg/1, and cyanide - 1,000 H9/1- Strier
developed these limitations utilizing data from a number of industrial
sources and projecting different treatment schemes.' The data now
available in this industry, however, supports the lower
concentrations .
Comments and additional data are welcomed on all of these toxic
pollutant limitations being considered by the Agency.
289
-------
ENGINEERING ASPECTS OF THE APPLICATION OF BAT
situation, some of the process^ ar* X d "?*£* Waste treatn,ent
beamhouse operations and tanv*^ „ grouped by function into
these different operations varies ?„ n^" tlons' /he wastewater from
'
---- -
pollutantmixes and loadng. eSlgne for ^pecxfic, less variable
C°lleCtion of »«tewater from the beamhouse and tanyard
m
essential to achieve th recmended
with a beamhouse and tanvard in arir- -
recovery and reuse of process chfmt^? ' ^ concePt facilitates
have expressed the samfopfnion with reqard tr^?fS ^st^ s™™**
management and control. A tarn^rv mf^ effective wastewater
and effective treatment system. 9 d operating a consistent
Another method of pollutant reduction employed by the industrv i* i-o
properly designed and operated? C-Laritier and the fHter unit are
290
-------
Cost-effective removal of oil and grease is best accomplished in
preliminary treatment or end-of-pipe primary treatment with
well-maintained and properly designed catch basins or clarifiers with
skimmers. Industries such as leather tanning, which
characteristically produce high oil and grease in their wastewater,
concentrate their removal efforts in primary treatment. Moreover,
"secondary" treatment technologies will work better when high oil and
grease loadings are avoided. Equipment fouling and overloads to the
secondary treatment system are associated with excessive influent oil
and grease loading. Many toxic pollutants which are not soluble in
water tend to be included in fats, oils, and greases, and therefore
can be reduced by separating or skimming the floating oil and grease
from primary clarifiers.
Ammonia reduction in leather tanning wastewaters has been achieved by:
1) end-of-pipe extended aeration technology; 2) physical-chemical
treatment; and 3) substitution of magnesium sulfate for ammonium
sulfate in the deliming process of the tanyard operations. Using
magnesium sulfate directly reduces the ammonia content of tannery
wastewater by 67 percent, but increases chemical cost. One vegetable
tannery has indicated leather quality problems resulting from the
substitution while other plants did not report problems. As
substantial body of literature, highlighted in Section VII, indicates
that substitution for ammonia is feasible.
Most tanneries select a chemical alternative strictly on the basis of
cost. However, waste treatment cost for ammonia removal must now be
included in cost considerations because of the BAT effluent limit.
Reduced costs of ammonia removal support the use of an alternative to
ammonium sulfate. Ammonia substitution is then justified as a part of
the basis for BAT effluent limitations.
Wastewater treatment technologies recommended for achieving the BAT
limitations are producing low ammonia concentrations in the effluent
from leather tanneries and from industrial plants with comparable
waste streams, such as rendering plants. To achieve substantial
ammonia reduction, the recommended technology requires proper design
and carefully controlled operation. Long-term operating data from
shearling Tannery No. 253, which operates a Carrousel oxidation ditch
activated sludge system (subcategory no. 7), is the basis for transfer
of this nitrification technology to the remaining subcategories of the
leather tanning and finishing industry. With the exception of the
initial startup period, and periods of upset including April and May,
1979, this plant has produced consistently low effluent concentrations
of ammonia and TKN during both summer and winter months, as shown in
Figures 35 and 36.
Data from a full-scale nitrifying high solids extended
aeration-activated sludge system in other subcategories is not yet
available for comparison. EPA believes that with in-plant control of
ammonia to reduce the higher masses (lb/1,000 Ib) and concentrations
291
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for purely economic reasons, with the added benefit of improved
wastewater quality. Chrome recovery and reuse, which is approaching
standard practice, is an example of such decision-making within the
industry. Other process changes include sulfide reuse and recovery,
and substitution for ammonia in deliming. Reduction of water use can
be accomplished through conservation and recycle systems (including
pasting frame wash water), and other process modifications such as
those highlighted in Section VII of this document. The total mass of
regulated pollutants for all direct discharges removed from BPT
effluent levels by this BAT technology option would be as follows:
610,000 Ibs/year of BOD5; 2,000,000 Ibs/year of COD; 1,100,000
Ibs/year of TSS; 710,000 Ibs/year of oil and grease; 21,000 Ibs/year
of chromium (total); 1,670,000 Ibs/year of TKN; 620,000 Ibs/year of
ammonia; 5,100 Ibs/year of phenol (total); and 26,000 Ibs/year of
sulfide. EPA estimates the total mass of toxics pollutants discharged
would be as follows: 640 Ibs/year of volatile organics; 80C Ibs/year
of base/neutral organics; 2,000 Ibs/year of acid organics; and 380
Ibs/year of the inorganic pollutants exclusive of chromuim.
NON-WATER QUALITY ENVIRONMENTAL IMPACT
EPA has found that a significant portion of the toxic pollutants
removed from tannery wastewater remains intact in the solids that are
removed from the wastewater. These solids are subsequently disposed
in landfills and other disposal sites with variable controls, as
indicated in Sections VII and VIII. The impact of such disposal is
the primary non-water quality concern resulting from the BAT effluent
limitations. EPA estimates that achievement of BAT effluent
limitations will generate an additional 41,000 metric tons/year of
sludges from BAT treatment technology as applied by all direct
dischargers.
Energy consumption for waste treatment will increase in order to
achieve the proposed limits. However, the wastewater control and
management practices implemented to reduce the total flow may result
in a net energy saving, compared to the energy expended to achieve BPT
effluent limitations. Reduction in pumping and other operations
associated with wastewater movement and control will reflect less
energy use.
BAT EFFLUENT LIMITATIONS
The effluent concentrations and associated mass loadings listed in
Table 41 are long-term averages. Variability has been factored into
the maximum month and maximum day effluent limitations presented in
Table 45.
297
-------
Table 45
BAT EFFLUENT LIMITATIONS
Subcategory One - Hair Pulp, chron* Tan, Retan-Wet Finish
Pollutant or
Pollutant Property
BAT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kq/kkq
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH Within the
. -~— „.
(or lb/1000 Ib)
2.*
. 1
9f»
.5
2^
. 5
OQ 1
• J I
0.053
2-*
. 3
0*7 ~»
. 77
Of\ -t c
.015
0.0
range of 6.0 to
of raw material
0.61
5.8
0.70
0.26
0.015
0.66
0.22
0.0043
On
.0
9.0 at all times.
Subcategory Two - Hair Save/chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BAT Effluent: Limitations
Maximum for Average of daily
any one day values for 30
consecutive
Mass Units - kg/kkq for 1b/1000 lh) of ..... ^
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
2.3
10.0
2.6
1.0
0.053
2.4
0.81
0.016
0.0
0.65
6.2
0.74
0.28
0.015
0.69
0.23
0.0046
0.0
Within the range of 6.0 to 9.0 at all times.
298
-------
Subcategory Three - Hair Save/Non-Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BAT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ibl of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
1.6
7.3
1.9
0.70
0.039
1.8
0.60
0.012
0.0
0.47
4.5
0.54
0.20
0.011
0.51
0.17
0.0034
0.0
Within the range of 6.0 to 9.0 at all times
Subcategory Four - Retan-Wet Finish
Pollutant or
Pollutant Property
BAT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
pH
0.81
3.5
0.91
0.35
0.018
0.84
0.28
0.0056
0.0
Within the range of 6.0 to 9.0
0.23
2.2
0.26
0.10
0.005
0.24
0.081
0.0016
0.0
at all times
299
-------
Subcategory Five - No Beamhouse
Pollutant or
Pollutant Property
BAT Effluent Limitatinns
Maximum for Average of daily
any one day values for 30
consecutive davs
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
pH
1.4
6.2
1.6
0.60
0.034
1.5
0.49
0.010
0.0
0.40
3.8
0.46
0.17
0.0096
0.43
0.14
0.0029
0.0
Within the range of 6.0 to 9.0 at all times.
Subcategory Six - Through-the-Blue
Pollutant or
Pollutant Property
BAT Effluent Limitation^
Maximum for Average of daily
any one day values for 30
.consecutive davs
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH Within
1C
. D
6n
. 8
10
. 8
0.67
0.035
If
. 6
0.56
0.011
0.0
the range of 6.0 to
0. 44
V • *T •?
4.2
0.50
0.19
0.010
0.47
0.16
0.0031
0/\
.0
9.0 at all times
300
-------
Subcategory Seven - Shearling
Pollutant or
Pollutant Property
BAT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - ka/kkg (or lb/1000 Ibl of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
pH
6.7
29.8
7.7
2.9
0.16
7.4
2.4
0.049
0.0
Within the range of 6.0 to 9.0
1.9
18.0
2.2
0.83
0.046
2.1
0.69
0.014
0.0
at all times
301
-------
-------
SECTION XI
EFFLUENT REDUCTION ATTAINABLE BY BEST
CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY
INTRODUCTION
The 1977 amendments added section 301(b) (4) (E) to the Act,
establishing "best conventional pollutant control technology" (BCT)
for discharges of conventional pollutants from existing industrial
point sources. Conventional pollutants are those defined in section
304(b) (4) - BOD, TSS, fecal coliform and pH - and any additional
pollutants defined by the Administrator as "conventional." On July
28, 1978, EPA proposed that COD, oil and grease, and phosphorus be
added to the conventional pollutant list (43 Fed. Reg. 32857).
BCT is not an additional limitation, but replaces BAT for the control
of conventional pollutants. BCT requires that limitations for
conventional pollutants be assessed in light of a new "cost-
reasonableness" test, which involves a comparison of the cost and
level of reduction of conventional pollutants from the discharge of
POTW's to the cost and level of reduction of such pollutants from a
class or category of industrial sources. As part of its review of BAT
for certain "secondary" industries, EPA proposed methodology for this
cost test. (See 43 Fed. Reg. 37570, August 23, 1978).
EPA is proposing that the conventional "indicator" pollutants, which
are used as "indicators" of control for toxic pollutants, be treated
as toxic pollutants. In this way, effluent limitations will be
established for the conventional indicator pollutants at BAT levels,
and the limitations will not have to pass the BCT cost test. When a
permittee, in a specific case, can show that the waste stream does not
contain any of the toxic pollutants that a conventional toxic
"indicator" was designed to remove, then the BAT limitation on that
conventional pollutant will no longer be treated as a limitation on a
toxic pollutant. The technology identified as BAT for control of
toxic pollutants also affords removal of conventional pollutants to
BAT levels. As noted below, these effluent levels passed the BCT cost
test, and therefore, are also designated as BCT effluent levels.
APPLICATION OF BCT METHODOLOGY
EPA applied the BCT cost test to the costs associated with the removal
of conventional pollutants in the leather industry. In the first step
in the analysis, EPA calculated the size of an average plant for each
subcategory based upon the actual production of plants with direct
discharge. No plants existed in subcategory no. 6 (through-the-blue),
and the average plant size for indirect dischargers was used. Raw
waste load data (Tables 6-12) for each subcategory determined the
amount of wastewater and pollutant^load generated by each plant for an
303
-------
°
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6.
EFFLUENT LIMITATIONS
The pollutants controlled by this regulation include the conventional
conv^^onal'polfutants^OD^nfoil200!' TSS' Md PH' 9nd the **<>*>*<*
bas; o A ,aj- Fua.j.urants COD ana oil and crrease- Tho TJ^T. 4-^^v^^-i
Table
304
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Subcategory One - Hair Pulp/Chrome Tan/Retan - Wet Finish
Pollutant or BCT Effluent Limitations
Pollutant Property Maximum for Average of daily
any one day values for 30
— . consecutive days
Mass Units - kq/kkg (or lb/1000 lb) of raw material
BODS 91 f\ *i
— *• • 0.61
COD 9.5 5.8
TSS 2.5 0.70
Oil and Grease 0.91 0.26
pH Within the range of 6.0 to 9.0 at all times.
Subcategory Two - Hair Save, Chrome Tan, Retan-Wet Finish
Pollutant or BCT Effluent Limitations
Pollutant Property Maximum for Average of daily
any one day values for 30
. __ __ consecutive days
Mass Units - kq/kkcf for lb/1QOO lb) of raw material
BOD5 ? q A CC
— £• 3 0.65
COD 10.0 62
TSS 2.6 £^4
Oil and Grease 1.0 Q 28
PH Within the range of 6.0 to 9.0 at all times.
306
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Subcategory Three - Hair Save/Non-Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
BCT Effluent Limitations
Maximum for
any one day
Average of daily
values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BODS
COD
TSS
Oil and Grease
pH Within
1.6
7.3
1.9
0.70
the range of 6.0 to
0.47
4.5
0.54
0.20
9.0 at all times.
Subcategory Four - Retan-Wet Finish
Pollutant or
Pollutant Property
BCT Effluent Limitations
Maximum for
any one day
Average of daily
values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 Ib) of raw material
BOD5
COD
TSS
Oil and Grease
0.81
3.5
0.91
0.35
0.23
2.2
0.26
0.10
PH
Within the range of 6.0 to 9.0 at all times.
307
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Subcategory Five - No Beamhouse
Pollutant or
Pollutant Property
BCT Effluent Limitations
Maximum for Average of daily
any one day values for 30
— consecutive davs
Mass Units - kq/kkq (or lb/1000 Ib) nf ^w materia
BOD5
COD
TSS
Oil and Grease
PH
1.4
6.2
1.6
0.60
0.40
3.8
0.46
0.17
Within the range of 6.0 to 9.0 at all'tirnes.
Subcategory Six - Through-the-Blue
Pollutant or
Pollutant Property
BCT Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive
Mass Units - kg/kkq (or lb/1QOO Ibl of raw material
BOD5
COD
TSS
Oil and Grease
PH
1.5
6.8
1.8
0.67
0.44
4.2
0.50
0.19
Within the range of 6.0 to 9.0 at all times.
308
-------
Subcategory Seven - Shearling
Pollutant or
Pollutant Property
BCT Effluent Limitations
Maximum for
any one day
Average of daily
values for 30
consecutive days
Mass Units - kg/kkg (or lfc/1000 Ib) of raw material
BOD5
COD
TSS
Oil and Grease
PH
6.7
29.8
7.7
2.9
1.9
18.0
2.2
0.83
Within the range of 6.0 to 9.0 at all times.
309
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SECTION XII
NEW SOURCE PERFORMANCE STANDARDS
INTRODUCTION
The basis for new source performance standards (NSPS) under Section
306 of the Act is the best available demonstrated technology (BADT).
New plants have the opportunity to design the best and most efficient
leather tanning processes and wastewater treatment technologies.
Therefore, Congress directed EPA to consider the best demonstrated
process changes, in-plant controls, and end-of-pipe treatment
technologies which reduce pollution to the maximum extent feasible. A
major difference between NSPS and BAT is that the Act does not require
evaluation of NSPS in light of the BCT cost test.
EPA has selected control and treatment technology Level 6 (including
multi-media filtration) as the basis for NSPS because it provides for
the maximum feasible removal of toxic pollutants of concern. The
Aqency rejected Level 7 (GAC columns) because EPA believes that GAG
columns are too expensive and sophisticated for use in this industry.
Although EPA believes that physical-chemical treatment (Level UA) may
be a viable option, it rejected this technology option because of
technical and cost questions regarding its application to raw
wastewaters different from those of the retan-wet finish plant
(Subcategory Four) where it was installed. However, a new plant may
well overcome cost and technical questions with careful design and
pilot plant evaluation.
NSPS EFFLUENT LIMITATIONS
Since the control and treatment technology basis for NSPS is the same
as that established for BAT (Level 6), the methodology used to develop
the effluent limitations, the engineering aspects of this technology,
and the numerical effluent limitations (Table 43) are also the same.
311
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SECTION XIII
PRETREATMENT STANDARDS
GENERAL
The effluent limitations that must be achieved by new and existing
sources in the leather tanning and finishing industry that discharge
into a POTW are termed pretreatment standards. Section 307(b) of the
Act requires EPA to promulgate pretreatment standards for existing
sources (PSES) to prevent the discharge of pollutants which pass
through, interfere with, or are otherwise incompatible with the
operation of POTW's. The 1977 amendments to the Act also requires
pretreatment for pollutants, such as heavy metals, that limit POTW
sludge management alternatives, including the beneficial use of
sludges on agricultural lands. The legislative history of the 1977
Act indicates that pretreatment standards are to be technology-based,
analagous to the best available technology for removal of toxic
pollutants. The general pretreatment regulations (40 CFR Part 403),
which served as the framework for these proposed pretreatment
regulations for the leather tanning and finishing industry, can be
found in 43 Fed. Reg. 27736-27773 (June 26, 1978).
Consideration was also given to the following in establishing a
pretreatment standard:
1. the manufacturing processes employed by the industry;
2. the age and size of the equipment and facilities involved;
3. the location of manufacturing facilities;
4. process changes;
5. the engineering aspects of the application of
pretreatment technology and its relationship
to POTW;
6. the cost of application of technology in
relation to the effluent reduction and other
benefits achieved from such application; and
7. non-water quality environmental impact (including
energy requirements).
PRETREATMENT STANDARDS FOR EXISTING SOURCES (PSES)
Manufacturing Processes, and Size, Age, and Location of Facilities
The processes employed in different size tanneries within each
subcategory are basically similar. Furthermore, the factors of size,
313
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age, and processes employed do not affect the pretreatment control
technology used and proposed. Hence these factors were not direct^
oT facil?t?^ernining the *«*«*»«* standard. A!SO, ?he loc^ion
of facili was not a factor to be considered
Process Changes
- °Ut in Section VII< ^direct dischargers should consider
wf^^a was^ewater management and control practices to reduce
wastewater volume and pollutant loadings, as well as the surcharges
and capital cost recovery paid by tanneries discharging to POTW?f
This reduction can be achieved by implementing the following measures ":
1- Appoint a person with specific responsibility for water
management. This person should have reasonable powers to
enforce improvements in water and waste management and
implement better housekeeping practices. wgement and
2. Determine or estimate water use and waste load strength from
in all
Make all employees aware of good water management practices
and encourage them to apply these practices. one practice
™ri?? emplo?ee Participation is the elimination of the
constantly running hoses observed in some tanneries.
Recirculate non-contact cooling water, such as that from
vacuum driers.
Segregate waste streams from each major in-plant process
6. Use more care in unloading, unfolding and otherwise
pr°cessin^ to minimize salt entry into
7. Collect unhairing waste stream, reduce pH to isoelectric
point to precipitate dissolved protein, and recover the
protein as a valuable by-product. recover tne
8. Reuse or recover active chemicals from waste streams such as
Examine tanning formulas to determine if floats cap be
reduced. Use of hide processors and other specially
designed vessels has lowered float volumes, specially
314
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10. Provide regularly scheduled maintenance attention for
screening and solid waste handling systems throughout the
operating day. A backup screen may be desirable to minimize
solids entry into the municipal sewer system.
Such practices are feasible and may be economically attractive through
the reduction of municipal water and sewer use charges resulting from
lower flows and waste loadings.
Pretreatment Technology
Candidate control technologies for pretreatment are the same as those
considered as candidate BAT technologies for direct dischargers.
These technologies are as follows:
Level 1 - Water conservation and reuse to reduce flow
(all subcategories)
- Stream segregation for preliminary treatment
(subcategory nos. 1, 2, 3, 6, and 7)
- Ammonia substitution in deliming
(subcategory nos. 1, 2, 3, and 6)
- Chrome recovery and reuse
(subcategory nos. 1, 2, 5, 6, and 7)
- Sulfide liquor reuse followed by catalytic oxidation of
residual sulfide (subcategory nos. 1, 2, 3, and 6)
- Fine screening of segregated streams (all subcategories)
Level 2 - Flue gas carbonation and sedimentation for
beamhouse wastewaters (subcategory nos. 1, 2, 3, and 6)
Level 3 - Primary coagulation-sedimentation of combined streams
(applicable to all subcategories)
Performance of these levels of treatment were described in Section VII
for the specific technology. Table 41, presented in Section X,
indicates the performance of these technologies for tannery
wastewaters. Figures 4 through 9 schematically showed the
pretreatment technology identified for existing sources by
subcategory.
Rationale For The Pretreatment Standard
The rationale for developing the pretreatment standards rests
primarily on the concept of controlling pollutants which interfere,
pass through, or are otherwise incompatible with POTW treatment
systems and sludge disposal. See Section 307(b) of the Act and EPA's
recently promulgated pretreatment regulations (40 CFR Part 403, 43
Fed. Reg. 27736-27773 (June 26, 1978). BOD5, TSS, oil and grease,
total chromium, sulfide, ammonia, and other toxic pollutants are
present in sufficient concentrations in the raw waste from tanneries
315
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and Iluigfdisp^al. Wlth P°tential Problems of Pollutant pass-through
For this technology-based analysis, EPA has assumed the following:
1. Any joint municipal-industrial POTW which receives
leather tanning and finishing wastewater has been
assumed to provide primary sedimentation and
secondary biological treatment including final
clarification and sludge management. These
facilities are assumed to be properly designed
and diligently operated.
2. Analysis of pass-through and upset relating to POTW has been
determined up to the point of wastewater release from
control of the leather tanning and finishing plant;
therefore, specific collection system circumstances
may warrant consideration at the local level.
3. Local water quality constraints and unique
operational or sludge disposal problems,
have not been considered during this engineering analysis.
4. Strict adherence to and local enforcement of the
general prohibited discharge provisions of the
pretreatment regulation, and similar provisions
in local ordinances, is essential to ensure that
potential problems of upset and/or pass-through
noted below are not permitted to occur.
Tannery wastewaters potentially can create or contribute to the
following problems for a POTW:
1. potential problem with future disposal of sludges
containing toxic pollutants, especially chromium;
2. odors, facilities corrosion, very high dissolved
oxygen demand in aeration basins of biological
treatment systems, and hazardous gas generation
from sulfide-bearing wastes;
3. wide fluctuations in pH, and hydraulic and
pollutant loads;
4. excessive quantities of hair and other small
screenable solids;
5. high concentrations of suspended and settleable
solids, BOD5, and other pollutants; and
6. pass-through of ammonia nitrogen.
316
-------
The potential problems listed above can be largely eliminated through
leather tanners1 strict adherence to local discharge provisions and
national pretreatment regulations. Moreover, properly designed and
diligently operated POTW»s can suitably treat leather tanning and
finishing wastewater.
The information gathered during this study indicates that the BOD5 and
TSS found in tannery wastewater are amenable to removal by properly
designed and operated activated sludge secondary biological treatment
systems. Operating data from four joint municipal-industrial POTW's
which employ the activated sludge process to treat more than 50
percent tannery wastewater indicates that influent BOD5 and TSS
concentrations, which range from 250 mg/1 to 950 mg/1 and 200 mg/1 to
900 mg/1, respectively, can be reduced to effluent concentrations of
10 mg/1 to 65 mg/1 and 11 mg/1 to 75 mg/1, respectively. The broad
range of influent concentrations did not indicate a sensitivity to a
maximum level beyond which the wastewaters were not effectively
treated. However, none of these plants consistently achieved the BOD5
and TSS effluent concentrations which served as the basis for BAT and
BCT regulations.
Chromium is removed to low effluent concentrations from wastewater in
POTWfs which include primary treatment and secondary biological
treatment systems. Data from one municipality indicates that influent
chromium (trivalent) concentrations, often greater than 100 mg/1, are
reduced in the final effluent to concentrations of less than 2 mg/1.
Other POTW data indicate final effluent concentrations from 1 mg/1 to
as little as 0.1 mg/1.
Chromium removal occurs in treatment systems, but POTW's do not
monitor for chromium as extensively as they monitor for BOD5 and TSS.
Alkaline precipitation of chromium occurs readily in primary
clarifiers. EPA found no evidence that chromium interferes with the
performance of biological treatment systems in use as secondary
treatment. Two factors influence the chrome concentration of POTW
effluent: (1) dilution resulting from other wastes entering the POTW;
and (2) removal occurring within the waste treatment processes.
However, the presence of carbonates and improper pH can substantially
impair trivalent chromium removal. Moreover, comparison of observed
chromium effluent concentrations with those required by BAT effluent
limitations for direct dischargers indicates that the POTW effluent
may contain higher concentrations. With the bulk of the chromium
removed at the individual industrial sites by pretreatment through
Level 3, affected POTW's will be able to improve upon the effluent
concentrations of chromium and approach the levels of chromium
required by BAT. Consistent achievement of BAT chromium
concentrations by the POTW is one of the criteria for eligibility for
"credits" as set forth by 40 CFP Part 403.
A few municipalities have had substantial difficulty in finding
acceptable sites for disposal of sludges containing large quantities
317
-------
of chromium. Pretreatment through Level 3 at the industrial
-------
during summer months, when rapid bacterial uptake of
dissolved oxygen can cause release of unoxidized hydrogen
sulfide.
A careful review of the extent of these sulfide-related problems has
led EPA to conclude that national regulation is necessary. Currently
available and practicable technology (catalytic oxidation) can remove
most if not all dissolved sulfides. Where a tanner has segregated the
siilfide-bearing beamhouse wastewater for separate catalytic oxidation,
sulfide carry-over by the hides or skins into tanyard and wet
finishing waste streams may require the precipitation of this residual
to achieve the effluent limitation. Coagulation with ferric chloride
is an approach available for controlling sulfide in tanyard and wet
finishing wastewaters. However, it also is likely that sulfide will
be liberated to the atmosphere during the acid-based processes
including tanning. Taken together, sulfide removal technology and
provision of suitable pH conditions can achieve a pretreatment
standard of 0.0 mg/1 (not detectable by the analtyical method for
sulfide) at the point of discharge to the POTW sewer.
Effluent data from POTWs indicate that ammonia nitrogen passes
through both POTW's and separate tannery wastewater treatment systems
which are well designed and operated. Substitution for ammonia in the
deliming process, along with beamhouse pretreatment to remove a
substantial portion of the protein which ultimately contributes
substantially to ammonia, should sufficiently reduce the ammonia
content of leather tanning wastewaters. This should allow
nitrification in POTW biological treatment systems to be more
successful in controlling pass-through of this pollutant.
EPA has reviewed the proposed pH range of 6.0 to 9.0, with special
regard for the control of hydrogen sulfide gas evolution and trivalent
chromium removal at low values of pH. The Agency has determined that
for maximum control of sulfides in gravity collection systems and POTW
headworks, and for maximum removal of trivalent chromium largely in
primary clarifiers, the optimum pH range is 7.0 to 10.0. Potentially
dangerous evolution of sulfides can occur below a pH of 7.0, and below
a pH of 6.0 potentially inadequate removal of trivalent chromium can
occur. At pH greater than 10.0, the potential may exist for
disruption of biological treatment systems. Therefore, the
appropriate general sections of the regulation have been amended to
require pH no lower than 7.0 and no higher than 10.0 for the four
subcategories which include beamhouse operations, and to require pH no
lower than 6.0 and no higher than 10.0 for the retan-wet finish, no
beamhouse, and shearling subcategories.
Methodology Used to Develop PSES Effluent Limitations
Engineering analysis developed the PSES effluent limitations using in-
plant control and primary treatment technologies in building block
fashion. Within the tannery, the beamhouse and tanyard waste streams
319
-------
sss
ta±rd1 wfste1011/1 Sh°WS.the bre^°«n of the raw beamhouse and
tanyard waste streams prior to separate control measures
Engineering Aspects of Pre treatment Technology
Publicly Owned Treatment Works -
and Relationshic to
- Kexationstiip to
S6Ction' the
associated with leather
taSnninf
her ce enera
chromium precipitate in primary
a necessary
the
to equalization for effective
s
320
-------
sulfhydrates in the unhairing process risk catastrophic accidents if
pH is not controlled when segregated wastewaters are mixed. Plants
which do not operate a beamhouse may need lime addition to increase pH
to a level where effective biological treatment can be maintained, to
minimize corrosion, and to reduce chromium residuals to a level
acceptable to the POTW.
Effective fine screening (with openings in the range of 0.040 inches
to remove easily separated scraps, fibers, and hair) was lacking at
most leather tanning and finishing plants in the industry. Without
fine screening, pipes can become clogged and pumps, clarifier sludge
rakes, and other related equipment at the POTW can incur severe
damage.
The Agency recognizes that many plants in urban areas will require
extensive planning and judicious use of interior floor space and
adjacent land to incorporate pretreatment facilities. Constraints on
available interior plant floor space and adjacent land was a key
decision criterion in the pretreatment technology selection process.
Moreover, the selected PSES were not as stringent as EPA would have
preferred due to land constraints,
In cases where a number of plants are located in close proximity to
each other, combined pretreatment facilities may afford a cost-
effective approach to reduce both total costs and costs to each
tanner, minimize duplication of facilities at each plant, and take
advantage of economics of scale. This is likely to be especially
germane to sludge dewatering and transporting equipment, and to the
identification, development, and use of hazardous waste disposal
sites.
COST AND EFFLUENT REDUCTION BENEFITS
Approximately 170 tanneries currently discharge to POTW's, and are
thus subject to pretreatment standards for existing sources. While a
few of these plants have some wastewater treatment in place, the
following estimated costs assume none. EPA estimates that total
investment costs to meet proposed PSES will be approximately $59
million, with total annual operating costs of about $21 million,
increasing current operating expenses by 3.0 percent.
EPA estimates that the total mass of regulated pollutants for all
indirect dischargers removed from untreated wastewaters by this PSES
technology option would be as follows: 2,300,000 Ibs/year of chromium
(total); 1,400,000 Ibs/year of ammonia; and 1,800,000 Ibs/year of
sulfide. The total mass of pollutants not regulated but removed from
untreated discharge levels by this PSES technology option would be as
follows: 30,000,000 Ibs/year of BOD5; 88,000,000 Ibs/year of COD;
46,000,000 Ibs/year of TSS; 8,200,000 Ibs/year of oil and grease; and
2,500,000 Ibs/year of TKN. EPA estimates the total toxic pollutant
discharge would be as follows: 6050 Ibs/year of volatile organics;
7500 Ibs/year of base/neutral organics; 18,000 Ibs/year of acid
321
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llunts exciusi-
underlie efflt u,n?ations19er ^ the con^^rations which
Non-Hater Quality Environmental Impact
The proposed pretreatment standard will substantially reduce the
'
and
th37'°°° metric *«*« P« year will be generated
by
concentraionsof toxpollutas11"
322
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PSES EFFLUENT LIMITATIONS
Table 48 lists the pretreatment standards for existing sources in each
subcategory.
Table 48
PSES EFFLUENT LIMITATIONS
Subcategory One - Hair Pulp/Chrome Tan/Retan-Wet Finish
Pollutant or Maximum Average of daily
Pollutant Property concentration concentrations
for any one for 30 consecutive
__ day days
milligrams per liter (mg/1)
Total Chromium 6 3
Ammonia 136 68
Sulfide 0.0 0.0
pH Within the range of 7.0 to 10.0 at all times.
Subcategory Two - Hair Save/Chrome Tan, Retan-Wet Finish
Pollutant or Maximum Average of daily
Pollutant Property concentration concentrations
for any one for 30 consecutive
dav-mg/1 days-mg/1
milligrams per liter (mg/1)
Total Chromium 6 3
Ammonia 138 69
Sulfide 0.0 0.0
pH Within the range of 7.0 to 10.0 at all times.
323
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subcategory Three - Hair Save. Non-Chrome Tan, Retan-Wet Finish
Pollutant or
Pollutant Property
Total Chromium
Ammonia
Maximum Average of daily
concentration concentrations
for any one for 30 consecutive
ciay-mq/1 days-mg/1
milligrams per liter (mg/1)
PH
Within the range of 7.0 to 10.0 at all times
Subcategory Four - Retan-Wet Finish
Pollutant or
Pollutant Property
Average of daily
concentration concentrations
for any one for 30 consecutive
milligrams per liter
Total Chromium
Ammonia
PH
o.0
Within the range of 6.0 to 10.0 at all times
Subcategory Five - No Beamhouse
Pollutant or
Pollutant Property
Maximum Average of daily
concentration concentrations
for any one for 30 consecutive
day-m/1 days-ma/l
milligrams per liter
Total Chromium 6 3
Ammonia + c (•
Sulfide ofo 00
PH Within the range of 6.6 to 10.0 at all times,
324
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Subcategory Six - Through-the-Blue
Pollutant or Maximum Average of daily
Pollutant Property concentration concentrations
for any one for 30 consecutive
dav-mq/1 davs-mg/1
milligrams per liter (mg/1)
Total Chromium 6 3
Ammonia 120 60
Sulfide 0.0 0.0
pH Within the range of 7.0 to 10.0 at all times.
Subcategory Seven - Shearling
Pollutant or Maximum Average of daily
Pollutant Property concentration concentrations
for any one for 30 consecutive
dav-mq/1 davs-mg/1
milligrams per liter (rng/1)
Total Chromium 6 3
Ammonia 52 26
Sulfide 0-0 °-° .
pH Within the range of 6.0 to 10.0 at all times.
PRETREATMENT STANDARDS FOR NEW SOURCES (PSNS)
Section 307 (c) of the Act requires EPA to promulgate pretreatment
standards for new sources (PSNS) coincidently with the adoption of
NSPS. New indirect dischargers, like new direct dischargers, have the
opportunity to incorporate the best available demonstrated control
technologies (BADT) including process changes, in-plant controls, and
end-of-pipe treatment. New plants can select and locate on a s^t- to
ensure adequate installation of the treatment system.
325
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treatmen scheme considere c» BAt
dischargers. The PSNS technologiefare af follo^
Level 1 - water conservation and reuse to reduce flow
- Stream segregation for preliminary treatment
- Ammonia substitution in deliming <*tment
- Chrome recovery and reuse
"
- Fine screening of segregated streams
Level 2 - Flue gas carbonation and sedimentation
for beamhouse wastewaters
Level 3 - Equalization of combined streams followed by
primary coagulation-sedimentation
Level 4A - Physical /chemical treatment (Chappel Process)
techno^ies with r^pec(f **£**», ^^^L^^^o^es
As noted in the rationale for the pretreatment standard for
°US
to tat
waters. , and discharge direct to navigable
EFFLUENT LIMITATIONS
The general pretreatment regulations
. ,
326
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Table 49
PSNS EFFLUENT LIMITATIONS
Pollutant or
Pollutant Property
Maximum
cone en tr at ion
for any one
day-mg/1
Average of daily
concentrations
for 30 consecutive
davs-mg/1
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide
pH Within the
74
325
84
32
1.8
79
26
0.53
0.0
range of
21
200
24
9
0.5
23
7.5
0.15
0.0
6.0 to 9.0 at all times.
Equivalent mass limitations for each subcategory are as follows
Subcategory One - Hair Pulp/Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kq/kkg (or lb/1000 lb) of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
2.1
9.5
2.5
0.91
0.053
2.3
0.77
0.015
0.0
0.61
5.8
0.70
0.26
0.015
0.66
0.22
0.0043
0.0
Within the range of 6.0 to 9.0 at all times
327
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Subcategory TWO - Hair Save/Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive
Mass Units - kg/kkg (or Ih/lQQQ ib) Qf
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
2.3
10.0
2.6
1.0
0.053
2.4
0.81
0.016
0.0
0.65
6.2
0.74
0.28
0.015
0.69
0.23
0.0046
0.0
Within the range of 6.0 to 9.0 at all times.
Subcategory Three - Hair Save/Non-Chrome Tan/Retan-Wet Finish
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive davs
Mass Units - kg/kkcr (or lb/1000 Ib) nf
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
1.6
7.3
1.9
0.70
0.039
1.8
0.60
0.012
0.0
:n
0.47
4.5
0.54
0.20
0.011
0.51
0.17
0.0034
0.0
Within the range of 6.0 to 9.0 at all times.
328
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Subcategory Four - Retan-Wet Finish
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 lb) of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
0.81
3.5
0.91
0.35
0.018
0.84
0.28
0.0056
0.0
0.23
2.2
0.26
0.10
0.005
0.24
0.081
0.0016
0.0
Within the range of 6.0 to 9.0 at all times
Subcategory Five - No Beamhouse
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 lb) of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
6.2
1.6
0.60
0.034
1.5
0.49
0.010
0.0
0.40
3.8
0.46
0.17
0.0096
0.43
0.14
0.0029
0.0
Within the range of 6.0 to 9.0 at all times
329
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Subcategory Six - Through-the-Blue
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive days
Mass Units - kg/kkg (or lb/1000 lb) of raw materia
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH Within the range
1.5
6.8
1.8
0.67
0.035
1.6
0.56
0.011
0.0
of 6.0 to
0.44
4.2
0.50
0.19
0.010
0.47
0.16
0.0031
0.0
9.0 at all times
Subcategory Seven - Shearling
Pollutant or
Pollutant Property
Effluent Limitations
Maximum for Average of daily
any one day values for 30
consecutive _days
Mass Units - kg/kkg for lb/1000 lb) of raw material
BOD5
COD
TSS
Oil and Grease
Total Chromium
TKN
Ammonia
Phenol
Sulfide (mg/1)
PH
6.7
29.8
7.7
2.9
0.16
7.4
2.4
0.049
0.0
1.9
18.0
2.2
0.83
0.046
2.1
0.69
0.014
0.0
Within the range of 6.0 to 9.0 at all times
330
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SECTION XIV
MONITORING
INTRODUCTION
When required to carry out the objectives of the Act, EPA is
authorized by Section 308 to require the owner or operator of a
polluant discharge source to establish and maintain records, make
reports, install and use monitoring equipment or methods, sample
effluents and provide such other information as the Administrator may
reasonably require. The authority under Section 308 has been
frequently used by permit issuers to set monitoring requirements to
"determine whether any person is in violation" of the requirements of
a permit or other requirements of the Act (Section 308(a) (2)).
Additionally, EPA has frequently sought information under Section 308
to aid in developing regulations for many industries.
In these, and perhaps other "toxics" regulations, EPA is setting
monitoring requirements for direct and indirect dischargers for the
purpose of "developing or assisting in the development" of future
effluent limitations guidelines, pretreatment standards and standards
of performance (Section 308 (a) (1)). These monitoring requirements are
not intended to supersede or duplicate compliance monitoring
requirements set by NPDES permit authorities. A mandatory monitoring
and analysis program is feasible at this time because the costs for
toxic pollutant analyses have decreased and laboratory availability
and efficiency have dramatically increased since the initiation of
this study.
MONITORING PROGRAM
•
The monitoring program included in the proposed regulation will serve
a number of purposes. First, the long term data generated on
conventional, nonconventional and toxic pollutants will allow the
Agency to review and revise, if necessary, the proposed regulations.
Where data indicates that treatment technologies discharge effluent
levels different from those in the regulations, adjustments will be
made and the regulations amended. Second, the data collection program
is designed to permit the Agency to establish express limits on
specific toxics of concern (i.e., pentachlorophenol,
2,4,6-trichlorophenol, lead, etc.), or alternatively, establish
statistically valid correlations among "surrogate" (now "indicator")
pollutants and the toxic pollutants of concern. Selection of
surrogate pollutants would allow identification of a shorter and less
costly (in terms of monitoring expense) list of pollutant parameters
for which plants would be required to sample and analyze. Third,
these monitoring requirements will combine all major data collection
activities into one reporting mechanism.
331
-------
are numerous developments and alternatives potentially available
monitoring cost for toxic pollutants in addition to the
ar^ -f. »of surrogates (indicators) of toxic pollutants A
specific group or groups within the total list of toxic pollutants"may
somelme™^°r ?* la?9e n^ber °f SamPles nationwide1" may produce
Approaches? SCale "lth automate<3 °* similar cost reduction
The proposed monitoring and analysis program would require continuous
tlow and pH monitoring at points of discharge to POTWs (for indirect
dischargers) or discharge to receiving waters for direct
dischargers). Plants which process more than 3.1 million pounds plr
year of raw material will be required to collect a 24-hour composite
sample once every week (in all cases during a representative periol of
m^aT" n^^^^,0^1..^. ™*«*?_ - 3imilar6p!e^s of
oil and
asr rj£si ss ss
24-hour composite sample once quarterly (again dSing a representative
Plants which process less than 3. 1 million pounds per year of raw
material will be required to collect a 24-hour composite samnle ™™
V
afsohbrt°^en°i'- "^ Pe»talorophenolconcurrt grab sles' musl
also be taken twice per year and analyzed for cyanide (total™.
All plants will be additionally required to report the total
zsrir ss.
.
etc.), and the hourly values of flow and pH for the reriod of £^?1
.
332
-------
quantitatively specifies the design and operating features of all unit
processes and equipment.
Monitoring requirements for direct dischargers will be effective on
the issuance of a new NPDES permit or renewal or extension of an
existing permit, and will remain in effect for two years from that
date. Monitoring requirements for indirect dischargers will be
effective three years from the date of promulgation of these
regulations (or on the earlier installation of technology to meet
pretreatment standards) and will remain in effect for one year. On a
quarterly basis, all individual data points generated by this
monitoring program must be submitted directly to the Project Officer,
Leather Tanning and Finishing Industry, Effluent Guidelines
Division (WH-552), EPA, U01 M St. S.W., Washington, D. C. 20U60.
Copies also must be submitted to NPDES authorities (direct
dischargers) and affected POTWs (indirect dischargers). Where these
individual data points are submitted for compliance monitoring
purposes, duplicate sampling and analyses are not required.
333
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-------
SECTION XV
ACKNOWLEDGEMENTS
The program was conducted by a team of staff members and consultants
of the Midwest Research Institute (MRI), Minnetonka, MN, under the
direction of Mr. Robert J. Reid. Major contributors included Messrs.
R. R. Rich, E. P. Shea, Mrs. Vicki Moteelall, Ms. Janine Neils,
Messrs. James Spigarelli, Clarence Haile, R. H. Forester, Chris Lough,
Edward Conway, J. R. Neleigh, K. R. Walker, D. Weatherman, J. G.
Edwardsff R. F Colingsworth and I. N. Ibraham, Mrs. Robin Raslmussen
and Mrs«, Mary Weldon.
Contributions were also made to this study by the consultants:
Lawrence Rust, Stanley Consultants, Inc., and SCS Engineers, Inc. The
EPA contractor for the economic impact study, Development Planning and
Research Associates, Inc., was also very helpful in providing
information for use in this report.
Thanks are also due to Mr. David Ertz and Mr. Ralph Oulton of the E.C.
Jordan Co., for their final technical editorial review to this
document.
The cooperation and assistance of the Tanners1 Council of America was
invaluable to this program especially in the persons of Dr. Robert
Lollar and Mr. Eugene Kilik, who provided personal time and attention
during various stages of the data collection process. The numerous
tannery owners, managers, superintendents and operators who submitted
information, opened their plants to program staff, and othe?rwise
cooperated are acknowledged and thanked for their patience and hnlp.
The people in the various offices of the EPA, of state pollution
control agencies, and of local POTW and other public agencies or
officials are also acknowledged for their help on this program.
Mr. Barry Malter of the Office of General Counsel is specially
acknowledged for his major contribution to the development of
technical and legal rationale, and to the integrity and readability of
the preamble, regulation, and this * development document. Ms.
Margherita Pryor also provided significant editorial improvement to
this document.
Word processing for this project was performed by Ms. Nancy Zrubek,
with assistance from Ms. Kaye Starr and Ms. Carol Swann. Their
personal sacrifice and long hours made possible the assembly of a
large volume of written material into a document of high quality in a
very short period of time. Without their efforts, the preamble,
regulations, and this development document would not be available.
335
-------
effort. Their contributions are gratefully acknowledged?
336
-------
SECTION XVI
REFERENCES
1. Development Document for Proposed Effluent Limitations
Guidelines and New Source Performance Standards for the
Leather Tanning and Finishing Industry, U.S. Environmental
Protection Agency, Report No. 440/1-74-016-a, Washington,
March 1974.
2. Leather Facts, New England Tanners Club, Peabody, MA, 1965,
3. Personal Communication with P. Maier, Dwars, Heederik en
Verhey B.V., the Netherlands.
4. Quality Criteria for Water, U.S. Environmental Protection
Agency, Report No. 440/9-76-023, Washington, D.C., July
1976.
5. Proposed Water Quality Criteria, U.S. Environmental
Protection Agency. 44 FR 15926, March 15, 1979.
6. Benzene. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 292421, Natl. Tech. Inf. Serv.,
Springfield, VA.
7. Proposed Water Quality Criteria, U.S. Environmental
Protection Agency, 44 FR 43660, July 25, 1979.
8. Tetrachloroethylene. Draft Criteria Document, U.S.
Environmental Protection Agency. PB 292443, Natl. Tech.
Inf. Serv., Springfield, VA.
9. Carbon Tetrachloride. Draft Criteria Document, U.S.
Environmental Protection Agency. PB 292424, Natl. Tech.
Inf. Serv., Springfield, VA.
10. Toluene. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 296805, Natl. Tech. Inf. Serv.,
Springfield, VA.
11. Trichloroethylene. Draft Criteria Document, U.S.
Environmental Protection Agency. PB 292445, Natl. Tech.
Inf. Serv., Springfield, VA.
12. Chloroform. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 292427, Natl. Tech. Inf. Serv.,
Springfield, VA.
337
-------
13. Dichlorobenzenes. Draft Criteria Document o s
Environmental Protection Agency. PB 292U29, Natl. Tech"
Inf. serv.. Springfield, VA.
11. Nitrosamines. Draft Criteria Document, U.S. Environmental
Springfield,^?^- PB 2"™*' Hat1' TeCh' Inf' Serv-
15. 1.2-Diphenylhydrazine. Draft Criteria Document, u S
"
16. Benzidine. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 297918 Natl T^b r^f &
Springfield, VA. ' Serv.,
17. 3,3|-Dichlorobenzidine. Draft Criteria Document, u s
TPww^ -w-^-^*~«Mk *^.M j__ —. n •«. _ . . • . " *
18. isophorone. Draft Criteria Document, U.S. Environmental
Protection * —
*ra.Wucv.uj.uii Agency. PB 296798, Natl. Tech Inf q*>™
Springfield, VA. i«.i. lecn. int. Serv.,
19" Protection6" °raft Criteria Docuinent' U.S. Environmental
20. Polynuclear Aromatic Hydrocarbons. Draft Criteria Document,
U.S. Environmental Protection Agency. PB 297926 Natl
Tech. Info. Serv., Springfield, VA. ^^^. Natl.
21. ^heno1-. Dr*ft Criteria Document, U.S. Environmental
22. 2,4-Dichlorophenol. Draft Criteria Document, u s
Environmental Protection Agency. PB 292431, Natl. Tech"
Inf. Serv., Springfield, VA.
23. Chlorinated Phenols. Draft Criteria Document, u.s
Environmental Protection Agency. PB 296790, Natl Tech
Info. Serv., Springfield, VA.
24. 2,4-Dimethylphenol. Draft Criteria Document, U.S.
TPffcTT1* W»X^.*>**M ^*.M. _1_ —. 1 1-* _ _ _ i . • *
338
-------
25. Pentachlorophenol. Draft Criteria Document, U.S.
Environmental Protection Agency. PB 292439, Natl. Tech.
Inf. Serv., Springfield, VA.
26. Chromium. Draft Criteria Document, U.S. Environmental
Protection Agency, PB 297922, Natl. Tech. Info. Serv.,
Springfield, VA.
27. Copper. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 296791, Natl. Tech. Info. Serv.,
Springfield, VA.
28. Nickel. Draft Criteria Document, U.S. Environmental
Protection Agency. PB 296800, Natl. Tech. Info. Serv.,
Springfield, VA.
29. Larsen, Bjarne C., "Utilization of the Hide Processor in
Reducing Tannery Effluent," presented at the 67th Annual
Meeting of the American Leather Chemists1 Association,
Mackinac Island, Michigan, June 20 through 23, 1971, as part
of the Mini-Symposium on Tannery Effluents.
30. Data obtained from questionnaires sent to individual
tanneries in the industry.
31. van Vlimmeren, P.J., "Tannery Effluent," Journal of the
American Leather Chemists' Association, Sept. 1972, p. 395-
396.
32. van Vlimmeren, P.J., "Tannery Effluent Report to the Members
of the Effluent Commission of the International Union of
Leather Chemists' Societies," Journal of the American
Leather Chemists' Association, Oct. 1972, p. 431-465.
33. Perkowski, S., "Water Reuse Systems in the Leather
Industry," Das Leder (Ger.), 21, 63 (1970); Chem. Abs. 72,
16326 (1970),
34. Leather Tannery Waste Management Through Process Change,
Reuse and Pretreatment, U.S. Environmental Protection
Agency, Report No. 600/2-77-034, Washington, January 1977.
35. Williams-Wynn, D.A., "No-Effluent Tannery Processes,"
Journal of the American Leather Chemists' Association,
Volume LXVIII, No. 1, 1973.
36. Hauck, Raymond A., "Report on Methods of Chromium Recovery
and Reuse from Spent Chrome Tan Liquor," Journal of the
American Leather Chemists' Association, Volume LXVII, No.
10, 1972.
339
-------
37. Money, c., and Adminis, u., "Recycling of Lime-Sulfide
of L^th9 Llquors- Im S™311 Scale Trials," Journal Society
38. Frendrup, w., and Larsson, "Effect of Depilating Methods on
39. Theis, Edwin R., o-Flaherty, Fred, -Conservation of Chromium
Leather lndustry,« Hide and Leather and shoes.
40. Davis, M.H., Scroggie, J.G., "Investigation of Commercial
^5°m^Tannir,9 Systems Part IV— He-cycling of chrome Liquors
and Thexr use as a Basis for Pickling," Journal of the
|22ietv of Leather Technologists and Chemists, vol. 577 ^
11. Davis, M.H., Scroggie, J.G., "Investigation of Commercial
Chrome-Tanning Systems Part V— Recycling of Chrome Liquors
<* ^S
42. Burns, J.E., Colquitt, D.E., Davis, M.H. , Scroggie, J.G.,
Investigation of Commercial Chrome-Tanning Systems Part VI-
-Full-scale Trials of chrome Liquor Recvclina
L^taT Sf ^ conce«tration," Journal of ^
tieather lechnolociists and Chemists, ^/oTTeoTpTTo I
<»3. ward, G. J., slabbert, N.P., shuttleworth, S.G., "Recent
Developments in Tannery Process Modification for Reducina
stl-560? S° d WaStes'" ^CA. Vol. 71, December 1976?^
" "Recycle of Tan Liquor from organic Acid
Process," JALCA, Vol. 70, May 1975, p. 206-219.
«5. Pierce, Robert, Thorstensen, Thomas C. , "The Recycling of
Chrome Tanning Liquors," JALCA, Vol 71, April 1976, p. 161-
46. Robinson, John w. , "Practical chrome Recovery/Recycle
System," Leather and shoes. August 1976, p. 38-H2.
47. Telephone contact technical representative Permutit Company
Inc., Paramus, New Jersey, May 19, 1977.
48. Chementator, Chemical Engineering. May 9, 1977, p. 86-87.
340
-------
49. Supplement for Pretreatment to the Development Document for
the Leather Tanning and Finishing Point Source Category,
U,S. Environmental Protection Agency, Report No. 440/1-
76/082, Washington, November 1976.
50. Koopman, R.C., "Deliming with Magnesium Sulfate: A New
Deliming Process in Which the Pollution of Wastewater is
Reduced", Development and Improvement of Tanning Methods, V,
Deliming and Straining of Skins for Box Leather, Section D,
Institute for Leather and Shoes-TNO, June 1974.
51. Moore, Edward W., "Wastes from the Tanning, Fat Processing,
and Laundry Soap Industries," Source Unknown.
52. McKee, Jack Edward, and Wolf, Harold W., eds., Water Quality
Criteria. 2nd ed., The Resources Agency of California,
State Water Quality Control Board, Publication No. 3-A 1963.
53. steffan, A. G., In-Plant Modifications to Reduce Pollution
and Pretreatment of Meat Packing Waste Waters for Discharge
to Municipal Systems, prepared for Environmental Protection
Agency Technology Transfer Program, Kansas City, Mo., March
7-8, 1973.
54. Eye, J. David and Clement, David P., "Oxidation of Sulfides
in Tannery Wastewaters," Journal of the American Leather
Chemists' Association, Vol. 67, No. 6, 1972.
55. Bailey, D. A., and Humphreys, F. E., "The Removal of Sulfide
from Limeyard Wastes by Aeration," British Leather
Manufacturer's Research Association, Laboratory Reports, XV,
No. 1, 1966.
56. Chen, Kenneth Y., and Morris, J. Carrell, "Oxidation of
Sulfide by 02: .Catalysis and Inhibition," Journal of the
Sanitary Engineering Division Proceedings of the American
Society of Civil Engineers, Volume 98, No. SAl, February
1972.
57. Kessick, M. A. and Thomson, B. M. "Reactions Between
Manganese Dioxide and Aqueous Sulfide," Environmental
Letters, Vol. 7, No. 2, 1974.
58. Yasuo Ueno, "Catalytic Removal of Sodium Sulfide from
Aqueous Solutions," Journal of the Water Pollution Control
Federation, Vol 46, No. 12, December 1974.
341
-------
59. Yasuo, Ueno, "Catalytic Removal of Sodium Sulfide from
Aqueous Solutions and Application to Wastewater Treatment "
Water Research. Vol. 10, 1976. duiueut,
60. Data obtained by Stanley Consultants field investigations.
61. Happich, w.F., et al., "Recovery of Proteins From Lime-
-
62,
70.
Vol.
van Meer, A. J. J. , "Technical Note," JALCA, 68 (1973),
346.
63. Sutherland, R., Industrial and Engineering Chemistry 39
628, 1947. — " '
64. Sproul, Otis J., Atkins, Peter F., and Woodward, Franklin
Sliv, "Investigations on Physical and Chemical Treatment
Methods for Cattleskin Tannery Wastes," Journal Water
Pollution Control Federation, Volume 38, No. 4, April 1966.
65. "Report of the Symposium on Industrial Waste of the Tanning
Industry," Journal of the American Leather Chemists'
Association, Supplement No.^5, 1970. ^^ memists
66. Howalt, W., and Cavett, E. S., Transactions of American
Society of Civil Engineer sf 92, 1351, 1928. "
67. Riffenburg, H. B. , and Allison, W. w. , Industrial and
Engineering Chemistry f 33, 801, 1941. ~ -
68. Hagan, James R., and Eye, J. David, and Gunnison, G c
vea^,hnt0 S** Rem°Val °f C°lor from Biologica
Vegetable Tannery Wastes," Masters Thesis
University of Cincinnati, 1972. "e^ners rnesis,
69. Kinman, Riley N., "Evaluation of Bona Allen Wastewater
nn^en£ ^f°r Peri°d Februa*Y 1* 1972 to January 25, 1973."
Unpublished report, March 5, 1973.
Parker, Clinton E. , Anaerobic - Aerobic Lagoon Treatment for
1970?
annnq WaStes^ EPA Grant 12120 DIK,
71. Biological Treatment, Effluent Reuse, and Sludge Handling
for the Side Leather Tanning Industry, U.S. Environmental
eC ^'
i9 60 0/2-78- 01 3, Cincinnat
1978, pages 102 and 104.
342
-------
72 Upgrading Meat Packing Facilities to Reduce Pollution Waste
Treatment Systems, Bell, Galyardt, Wells, prepared for
Environmental Protection Agency Transfer Program, Kansas
City, Missouri, March 7-8, 1973. Omaha.
73. pevelopment Document for Effluent Limitations Guidelines and
New Source Performance Standards for the Red Meat Processing
Segment of the Meat Product and Rendering Processing Point
Source Category, U. S. Environmental Protection Agency,
Report No. 440/1-74-012-a, Washington, February 1974.
74. Lue-Hing, Cecil, et al., "Nitrification of a High Ammonia
Content Sludge Supernatant by Use of Rotating Disks,"
presented at 29th Annual Purdue Industrial Waste Conference,
May 1974.
75. Loehr, Raymond C., Agricultural Waste Management, Academic
Press, New York, 1974.
76. Anthonisen, A.C., Loehr, R.C., et al., "Inhibition of
Nitrification by Un-ionized Ammonia and Un-ionized Nitrous
Acid," presented at the 47th Annual Conference, Water
Pollution Control Federation, October 1974.
77. Eckenfelder, W., Water Quality Engineering for Practicing
Engineers, Barnes and Noble, Inc., New York, 1970.
78. Adams and Eckenfelder, "Nitrification Design Approach for
High Strength Ammonia Wastewaters," Journal WPCF,
Washington, D. C,, March 1977.
79. Nemerow, N.L., "Color and Methods for Color Removal," Proc.
llth Ind. Waste Conf•, Purdue Univ., Ext. Sec. 91 W.
Lafayette, Ind., 584 (1956).
80. Tomlinson, H.D., Tackston, E.L., Koon, J.H., Krenkel, P.A.,
"Removal of Color from Vegetable Tanning Solution," Journal
WPCF, Vol. 47, No. 3, March 1975, p. 562-576.
81. Cheremisinoff, Paul, N., P.E., "Carbon Adsorption of Air and
Water Pollutants," Pollution Engineering July 1976, £_._ 2±-
32.
82. Minor, Paul, S., "Organic Chemical Industry's Waste Waters,"
Environmental Science S Technology, Vol. 8, No. 7, July
1974, p. 620-625.
83. DeJohn, P.B. and Adams, A.D., "Treatment of Oil Refinery
Wastewater with Granular and Powdered Activated Carbon,"
30th Annual Purdue Industrial Waste Conference, May 6, 1975.
343
-------
'
85
86.
87.
88.
89.
90.
93.
95.
Conferenc, April i.
Ferguson, J.F., "Combined Powdered
ssas. .
Barry, L.T., and Flynn, B.P., "
Pollution
Activated carbon
Home for the
°
Oriw... c. a.. st.n.tro.. M.K.. Halk, J.D..
Alternative"!"'; "*CtiVated Slud^e Enhancement: A viable
£e£rt? Tertiary Carbon Adsorption," Unpublished
Black, James P. and Andrews, James N.,
C
Carbons in Wastewater Treatment," p 13
aager, D.G., "Waste Treatment Advances: Wastewater
Eichelberger, J. w. . and Lichtenberg, J.j. j
Works Assn., 63, No. 1, January 1971. ~
344
-------
96. Masek, V., Gas Woda Tech. Sanit, 39 (8), 1965.
97. Hager, D.G., and Rizzo, J.L., "Removal of Toxic Organics
from wastewater by Adsorption with Granular Activated
Carbon," presented at EPA Tech. Trans. Session on Treatment
of Toxic Chemicals, Atlanta, April 1974.
98. Marek, A. C. and Askins, W., "Advanced Wastewater Treatment
for an Organic Chemicals Manufacturing Complex," U.S./USSR
Symposium on Physical/Chemical Treatment, Cincinnati, Ohio,
November 12-14, 1975.
99. Shumaker, Thomas P., "Carbon Treatment of Complex Organic
Wastewaters," presented at Manufacturing Chemists
Association Carbon Adsorption Workshop, Washington, D.C.,
November 16, 1977.
100. Mulligan, Thomas J., and Fox, Robert D., "Treatment of
Industrial Wastewaters," Chemical Engineering/Desk Book
Issue, October 18, 1976, p. 62.
101. Leitz, Frank B., "Electrodialysis for Industrial Water
Cleanup," Env. Sci. and Tech., Vol. 10, No. 2 February 1976.
102. Membrane Processes for Treating Metal Finishing Wastes,
USPA, Project 12010 HJQ to the American Electroplaters.
103. Eckenfelder, W. Wesley, Jr., "Pretreatment of Industrial
Wastewaters for Discharge into Municipal Systems," presented
at Technology Transfer Seminar, Minneapolis, Minnesota,
October 2, 1976.
104. EPA Technology Transfer Document, "Process Design Manual for
Carbon Adsorption," 625/1-71-002a, October 1973, p 5-4.
105. Adams, Carl E., and W. Wesley Eckenfelder, Jr., Process
Design Techniques for Industrial Waste Treatment, Enviro
Press, Nashville, TN, 1974.
106. Assessment of Industrial Hazardous .Waste Practices-Leather
Tanning and Finishing Industry, SCS Engineers, Inc.,
prepared for U.S. Environmental Protection Agency, Solid
Waste Management Program, Washington, D.C., February 1976.
107. Strier, M.P., Treatability of Organic Priority Pollutants -
Parts C and E, Draft Document, Effluent Guidelines Division,
EPA, June 1978, May 1979.
345
-------
108. *nternal EPA Memorandum from M.P. Strier to D.F. Anderson
thfLeath^ Tf°r-the Drel°pment Of ^fluent Limitations for
the Leather Tanning Industry, May 14 , 1979.
109. Plunkett, Handbook of Industrial Toxicology. chemical
Publishing Co., 1976.
110. Siebert, C.L., »A Digest of Industrial Waste Treatment »
Pennsylvania State Department of Health, 1940.
111. Reuning, H.T., Sewage Works Journal, 20, 525, 1948.
112. Harnley, John W. , Wagner, Frank R. , and Swope, H. Gladys,
"Treatment of Tannery Wastes at the Griess Pfleger Tannery
" Journal, Volume XI?? NO!
113. Eldridge, E.F., Michigan Engineering Experiment station
Bulletin, 87:32, November 1939. -
Fales, A.L., Industrial and Engineering Chemistry, 21: 216
1929
115.
"Industrial Waste Survey at Caldwell Lace Leather Company,"
„ • Radiological and Industrial Waste
Section, Cincinnati, Ohio.
116. Eye, J. David, Treatment of Sole Leather Vegetable Tannery
Wastes, Federal Water
Department of Interior,
12120, September 1970.
117. Kunzel, Mehner A., Gesund, Ing. 66:300, 1943.
118. Middlebrooks, E. Joe, et al., "Evaluation of Techniques for
*£Zll TTRemoval from Wastewater Stabilization Ponds," Utah
State University, Logan, Utah, January 1974.
119. E.C.Jordan Co., inc., "Filtration and Chemically Assisted
r^1;1;10^10? °f Biol°9ically Treated Pulp and Paper Mill
Industry Wastewaters," Draft Report to EPA, 1979.
346
-------
SUPPLEMENTAL BIBLIOGRAPHY
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457.
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Atkinson, John, "A New Application of Mimosa in Leather Processing,"
The Leather Manufacturer, January 1976, Pp. 24-29.
Bailey and Hopkins, Preservation of Hides with Sulfite. II. A
Matched side Comparison of Leathers from Hides Preserved with Sodium
Sulfite or Brine Curing.
Bailey, Hopkins, Taylor, Filachione, Preservation of Hides with
Sulfite. ill. Statistical Evaluation of Shoe Upper Leather Prepared
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Cowhides.
Baird, Carmona, Jenkins, "Behavior of Benzidine and Other Aromatic
Amines in Aerobic Wastewater Treatment," Journal WPCF, July 1977, Pp.
1609-1615.
Barber, Nicholas, "Sodium Bicarbonate Can Settle Many Wastewater
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Benishek, Betty, "Health Hazards," The Leather Manufacturer, April
1976, Pp. 34-36.
Berg, Edward L., Wastewater Treatment System at Caldwell Lace Leather
Company.
Bernardin, F.E., Jr., "Selecting and Specifying Activated-Carbon-
Adsorbtion Systems," Chemical Engineering, October ^18, 1976, Pp. 77-
82.
347
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Brooks and Rumsey, Limnol^ oceanoa^ 10:521(1965). P. 12017
^^^^^
,
wastewater
Clark, Douglas w. , BOD; A Re- Evaluation .
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Practical Treatment
.
Environmental Protection
Effluents."
is- "Effect of
Solids m Tannery Unhairing
- •«-«-
Cope, Research Findings, U.S. Fish wildl. Ser. circ 226
wnoo.
th«
348
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Data obtained through communication with municipal treatment plants.
Data obtained through communication with tannery firms.
Davis and Scroggie, "Investigation of Commercial Chrome-Tanning
Systems - Part III - Recycling of Used Chrome Liquors," Journal of
Society of Leather Technicians & Chemists/ Vol. 57, Pp. 53-58.
Downing, Tomlinson and Truesdale, "Effect of Inhibitors on
Nitrification in the Activated-Sludge Process," J_-_ Proc. Inst. Sewage
Purif., 3, 537, 1964.
Envirogenics Systems Company, "Development and Demonstration of
Process for the Treatment of Chlorinated Cyclodiene Pesticide
Manufacturing and Process Wastes," December 1973.
Envirogenics Systems Company, "Status of Developments of Reductive
Degradation Treatment of Endrin-Heptachlor and Chlordane Manufacturing
Wastes," EPA Contract No. 68-01-0083, September 1974.
Eldridge, E.F., Michigan Engineering Experiment Station Bulletin, 87,
32, November 1939. Cited in Reference 15.
Eye, J. David, Treatment of Sole Leather Vegetable Tannery Wastes,
Federal Water Pollution Control Administration, Department of
Interior, Grant No. WPD-185, Program No. 12120, September 1970.
Eye, J.D., "Tannery Waste Management," Journal WPCF, Vol. 48, No. 6,
June 1976, Pp. 1280-1281.
Eye and Clement, "Oxidation of Sulfides in Tannery Waste Waters,"
Eye and Graef, "Pilot Plant Studies on the Treatment of Beamhouse
Wastes from a Sole Leather Tannery."
Eye, J.D., "Clarification of the • Lime-Bearing Wastes from a Sole
Leather Tannery."
Eye, J. David, "Tannery Wastes," Journal WPCF, June 1971, Pp. 998-
1001.
Fales, A.L., Industrial and Engineering Chemistry 21, 216, 1929.
Cited by Reference 15, Pp. 11770-11772.
Feairheller, Taylor, Bailey, Windus, "New Amino Acids Formed in Hair
During Unhairing."
Feairheller, Taylor, Bailey, Windus, "Further Evidence in Support of
the Elimination Reaction as the Mechanism of Alkaline Unhairing."
349
-------
0" 1 *<*»<»"** for Pesticide
,
Frendrup w., "The Influence of Unhairing Methods Upon the Amount and
?3':«'-'"-
Giusti D.M., et al., "Activated Carbon Adsorption of Petrochemicals "
Journal WPCF, Vol. 46, No. '5, p. 947, retrocnemicals,"
Vetaut, Goniprow, "A New Modified Chrome Tan System » The T^^
Manufacturer. July 1976, Pp. 20-22. Astern, The Leather
Grief eneder, "Tannery Effluent."
Hauck, Raymond, -some Notes on Thermal Unhairing."
°" Util""ion of Fleshings and Blue
350
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Heidemann, E., "A Very Rapid Liming and Tanning Process."
Henderson, Trans. Am. Fish Soc, 88:23 (1959).
Hockenbury and Grady, "Inhibition of Nitrification-Effects of Selected
Organic Compounds," Journal WPCF, May 1977, Pp. 768-777.
Homel and McVaugh, "A Meat Packer's Solution to Meeting 1983 Effluent
Requirements."
Hopkins and Bailey, "Preservation of Hides with Sulfite. I.
Concentration and Application Effects on Small-Scale Experiments with
Cattlehides."
Hopkins, Bailey, Weaver, Korn, "Potential Short-Term Techniques for
the Preservation of Cattle Hides."
Hunter and Sproul, "Cattleskin Tannery Waste Treatment in a Completely
Mixed Activated Sludge Pilot Plant," Journal WPCF, October 1969, Pp.
1722-1723.
"Industrial Waste Survey at Caldwell Lace Leather Company," EPA,
Office of Operations, Radiological and Industrial Waste Evaluation
Section, Cincinanti, Ohio.
Information from Polybac Corporation on NITROBAC - Technical Data
Sheet.
Irving, H.M.N.H., "The XVth Procter Memorial Lecture: Fact or Fiction?
How Much Do We Really Know About the Chemistry of Chromium Today?"
Journal of Society Leather Technologists & Chemists, Vol. 58, P. 51.
Johnston and Williams-Wynn, "The Liritan Semi-Rapid Sole Leather
Tannage," Journal of Society Leather Technologists & Chemists, Vol.
55, P. 192.
"Tannery Wastes," Journal WPCF, June 1970, Pp. 1188-1189.
Advertisements for Two Oxidation Ditch Systems, Journal WPCF.
Kennedy, D.C., "Treatment of Effluent from Manufacturer of Chlorinated
Pesticides with a Synthetic, Polymeric Adsorbent Amberlite XAD-4,"
Environmental Science and Technology, 7(2):138 (1973).
Kilik, Eugene L., "A Vision of the Tannery of the Future," The Leather
Manufacturer, July 1976.
Kinman, Riley N., "Treatment of Tannery Waste Water from Bona Allen,
Inc., Buford, Georgia."
351
-------
Effluent
-^^
0" S"
Prsses, " "N—A^- ^vent System for Tanning
Kremen. Seymour S. , "sole leather Tanning in a Solvent System."
Kremen and Southwood, "The infiin=»nr>o ~f « ^
Solvent Dehydration of HSes anfsSns... y<*°9en ^^ °n
' "Curing with Used Salt
Krisnamurthi and Padmini, "Purification of Used salt for Curing."
Kunzel-Mehner, A., Gesunhd,.. Ing^. 66, 300, 1943
" »«
. , »« f-
Effluents. ' part of a roini-symposium on Tannery
352
-------
Maire, Max S., "Engineering Aspects of Solvent Hide Processing."
Maire, Max S., "Offal Redux,» The Leather Manufacturer, September
1976, Pp. 12-23.
"Leather Chemists Meet for Pollution Pow-Wowr» The Leather
Manufacturer, June 1976, Pp. 9-10.
Marie and Sundgren, "Spray Irrigation of Tannery Wastes."
Marks, D.R., "Chlorinated Hydrocarbon Pesticide Removal from Waste
Water," EPA Grant 80315-01, Velsicol Chemical Corporation, May 1975.
Marks, D.R., "Testimony of Daniel R. Marks Respecting Technology to
Remove Endrin from Water," FWPCA (307) Docket No. 1, State of
Tennessee, Country of Shelby, March 14, 1974.
Mccreary and Snoeyink, "Granular Activated Carbon in Water Treatment,"
Journal AWWA, August 1977, Pp. 437-444.
McLaughlin, Blank, Rockwell, "On the Reuse of Salt in the Curing of
Animal Skins," Journal American Leather Chemists Assoc., Vol. XXIII,
No. 7, 1928.
"Meet a Tough Contender - Dry-Cleanable Leather," Chemical
Engineering.
Metzel and Somerville, "Unhairing Calfskins and Side Leather by an
Enzymatic Process."
Minor, Paul S., "Organic Chemical Industry's Waste Waters',
Environmental Science 6. Technology, Vol. 8, No. 7, July 1974, Pp. 620-
625.
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of Zinc Chloride or Calcium Hypochlorite as Alternatives to Sodium
Chlorite."
"New Sulfide-Precipitation Process for Removing Heavy Metals,"
Chemical Engineering, May 9, 1977, Pp. 86-87.
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48.
The Chemistry and Technology of Leather, Reinhold Publishing Corp.,
1956, Edited by O1Flaherty, Roddy, Lollar.
353
-------
waste
Arbor
Pierce and Thorstensen, -The Recycling of Cnro.e
Tanning Liguors .
Waste conf. of 1977, Purdueuniversity.PreSented 3t 32nd Industrial
n0f n,,°e R— - s-P—
Leather Ifechnoloaists S cheS. Vof. I^'P. ^f33^ 2f Society of
°f
«Removal of Heavy Metals fron, Wastewater," c 4 a. April 26, 1976.
Reuning, H.T., sewage Works Journal. 20, 525, ma.
"Revamping Toxics Control Program at PPa » T
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Robinson, John w. "Pr-^r-»-i ^=1 /-.^
I Shoes, august 1976! Pp? 38-\2 *eC°V^'R*c^ System,- Leather
naae
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satyendra. M., ,,Some Aspects of Tannery Effluent Control."
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354
-------
Shade, H.L., "Waste Water Nitrification,» Chemical Engineering
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Shivas, Stephen A.J., "A Study of Tannery Pulped Hair Soils."
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Corporation," Personal Communication, September 11, 1976.
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Shuttleworth, Dorrington, Cooper, Tutt, Every, "Pilot Plant Aeration
of Tannery Beamhouse Liquors," Journal of Society Leather
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State Department of Health, 1940.
Sivparvathi and Nandy, "Evaluation of Preservatives for Skin
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No. 14-12-596, Water Pollution Control Research Series 16040 ELO
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"Development of Treatment Process for Chlorinated Hydrocarbon
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Compounds Using Metallic Couples," U.S. Patent No. 3,737,384, for U.S.
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Sykes, R.L., "A Positive Approach to the New Pressure Groups - The
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355
-------
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" American CouncU
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°l H« Process Eguipment, «
on
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n
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in the
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356
-------
Whitehouse, "A Study of the Removal of Pesticides from Water,"
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Upgrading Sewage Lagoons to Meet Advanced Wastewater Treatment
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Carbon," Chemical Engineering Profession, May 1977, P. 65.
357
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-------
SECTION XVII
GLOSSARY
Aerobic
A biological process in which oxygen is used for microorganism
respiration needs. Especially relating to the degradation process of
waste matter in the presence of dissolved oxygen.
Anaerobic
A biological process in which chemically combined oxygen is used for
microorganism respiration needs. Relating to biological degradation
of waste matter in the absence of dissolved oxygen.
Back
That portion of the animal hide, especially cattlehide, consisting of
the center portion of the hide along the backbone and covering the
ribs, shoulders, and butt (excluding the belly).
Bating
The manufacturing step following liming and preceding pickling. The
purpose of this operation is to delime the hides, reduce swelling,
peptize fibers, and remove protein degradation products from the hide.
Beamhouse
That portion of the tannery where the hides are washed, limed,
fleshed, and unhaired when necessary prior to the tanning process.
That portion of the hide on the underside of the animal, usually
representing the thinnest part of the tannable hide.
Bend
That portion of the hide representing the entire hide cut down the
backbone with the bellies and shoulders removed.
Biochemical Oxygen Demand (BQD5)
The amount of oxygen required by microorganisms while stabilizing
decomposable organic matter under aerobic conditions. The level of
BOD is usually measured as the demand for oxygen over a standard five-
day period. Generally expressed in mg/1.
359
-------
Slowdown
0
of contaminants in any process
Blue
The
o -~~~.mi.my. niaes in T
characteristically blue in color!
Buffing
to
96
Pressing are
the nap of the uderide tn eaher. "" SUrfaCe and
Buffing Dust
Small pieces of leather removed in the buff in™
dust also includes small particles of a£™ 9 °peration- B««ing
and 1S of a coarse powder consistency? abrasive use<3 in the operation
Carding
shearlin,
****** Which Can ^ oxidized to
agent under acidic
A measure of the amount of
carbon dioxide
conditions
Chlorine Cr>n^act Tank
Chromium (Total)
Clarification
360
-------
Coagulant
A substance which forms a precipitate or floe when added to water.
Suspended solids adhere to the large .surface area of the floe, thus
increasing their weight and expediting sedimentation.
Collagen
The fibrous protein material within the hide which provides the bulk
of the volume of the finished leather and its rigidity.
Colloids
Microscopic suspended particles which do not settle in a standing
liquid and can only be removed by coagulation or biological action.
Color
A measure of the light-absorbing capacity of a wastewater after
turbidity has been removed. One unit of color is that produced by one
mg/1 of platinum as K^PtCl6.
Coloring
A process step in the tannery whereby the color of the tanned hide is
changed to that of the desired marketable product by dyeing or
painting.
Combination Tanned
Leathers tanned with more than one tanning agent. For example,
initially chrome-tanned followed by a second tannage (called a RETAN)
with vegetable materials.
Composite Sample
A series of small wastewater samples taken over a given time period
and combined as one sample in order to provide a representative
analysis of the average wastewater constituent levels during the
sampling period.
Concrete Mixer
A term often applied to hide processors.
Conditioning
Introduces controlled amounts of moisture to the dryed leather giving
it varying degrees of softness.
361
-------
Corium
Curryin
«» flesh. Also called
water system- ciassicaiiy
Degreasinq
and recovered as byproduct
Deliming
"
to
from the
s:
Demineraliza-hion
Dermis
That part of the hide which is between the flesh and the epidermis.
Desalinization
The process of removing dissolved salts from water.
Detention (Retention)
The dwelling time of wastewater in a treatment unit.
Dewatering
The process of removing a large part of the water content of sludges
DO
Dissolved oxygen. Measured in mg/1.
362
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Drag-out
Loss of process chemicals and solution onto products during processing
which are made up by periodic fresh addition of chemicals and
solution.
Drum
A large cyclinder, usually made of wood, in which hides are placed for
wet processing. The drum is rotated around its axis, which is
oriented horizontally. Also called wheel.
Dry Milling
The rotating of leather in a large wooden drum with no added chemicals
or water. Dry milling softens the leather.
Electrodialysi s
A form of advanced waste treatment in which the dissolved ionic
material is removed by means of a series of semipermeable membranes
and electric current.
Embossed
A mechanical process of permanently imprinting a great variety of
unique grain effects into the leather surface. Done under
considerable heat and pressure.
Enzymes
complex protein materials added to the hide in the bating step in
order to remove protein degradation products that would otherwise mar
hide quality.
Epidermis
The top layer of skin; animal hair is an epidermal outgrowth.
Equalization
The holding or storing of wastes having differing qualities and rates
of discharge for finite periods to facilitate blending and achievement
of relatively uniform characteristics.
Equivalent Hides
A statistical term used to relate the production of tanneries using
various types of raw materials. An equivalent hide is represented by
3.7 sq m of surface area and is the average size for a cattlehide.
363
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Eutrophication
« excessive growth of aquatic plts
Fatliquoring
the softness and pUabUiof the
Finishing
With
"astewater which results
substances
processes- Regulates
Fleshing
tanning, fleshing is often accomplished af^er
Float •
£.•"£* iEL-LTT £-£ °Uhr-
-------
Multi-Media Filter
A filtration device designed to remove suspended solids from
wastewater by trapping the solids in a porous medium. The multi-media
fitter if characterized by fill material ranging from large P«twJ«*
with low specific gravities to small particles with a higher specific
gravity? Irldation from large to small media size is in the direction
of normal flow.
Grain
The epidermal side of the tanned hide. The grain side is the smooth
side of the hide where the hair is located prior to removal.
Grease
A group of substances including fats, waxes, free fatty acids, calcium
and magnesium soaps, mineral oils, and certain other non-fatty
materials? The grease analysis will measure both free and emulsified
oils and greases. Generally expressed in mg/1.
Green Hides
Hides which may be cured but have not been tanned.
Head
That part of the hide which is cut off at the flare into the shoulder;
i,e., the hide formerly covering the head of the animal.
Hide
The skin - of a relatively large animal, at least the size of mature
cattle.
Ion Exchange
The reciprocal transfer of ions between a solid and a solution
surrounding the solid. A process used to demineralize waters.
lonization
The process by which, at the molecular level, atoms or groups of atoms
acquire a charge by the loss or gain of one or more electrons.
Isoelectric Point
The PH at which acidic ionization balances basic ionization so that an
electrolyte will not migrate in an electrical field.
365
-------
Liming
Nitrogen
n
Nitrogen^ Nitrat-
-------
The reciprocal logarithm of the hydrogen ion concentration in
wastewater expressed as a standard unit.
Parts per million. The expression of concentration of constituents in
wastewater, determined by the ratio of the weight of constituent per
million parts (by weight) of total .solution. For dilute solutions,
ppm is essentially equal to mg/1 as a unit of concentration.
Pasting
The process step generally following the retan-color-f atliquor
operations whereby the hide is attached to a smooth plate with a
starch and water paste and dried in a controlled heated vessel.
Pickling
The process that follows bating whereby the hide is immersed in a
brine and acid solution to bring the skin or hide to an acid
condition; prevents precipitation of chromium salts on the hide.
Plating
The finishing operation where the skin or hide is "pressed" in order
to make it smoother. Plating may be done with an embossing plate
which imprints textured effects into the leather surface.
Polymer
An organic compound characterized by a large molecular weight.
Certain polymers act as coagulants or coagulant aids. Added to the
wastewater, they enhance settlement of small suspended particles. The
large molecules attract the suspended matter to form a large floe.
POTW
Publicly owned treatment works, i.e., municipal waste treatment
system.
Pullery
A plant where sheepskin is processed by removing the wool and then
pickling before shipment to a tannery.
Method of unhairing in which depilatory agents are used to dissolve
hair entirely in a few hours.
367
-------
Retanning
agents. fanning imparts
Reverse Osmosis
A process whereby water r»r-/- 4-~
membranes under high pressures S£! - P3SS thr°Ugh
relatively free of Pd!IsSvId sollL^^^0^ the »«*rane is
concentrated form on the f eeFs'idf of^ne ^fane an"
Sanding
tb.
Sedimentation
Clarification (settling)
Setting_Out
condition for drying
Sharpeners
Shavin
Shavins
and stretches
moistur«- Puts hides into proper
<*««"«»•• — «•
the size of wood shavings? ^"^ hld6' Which are approximately
Shearling
A lamb or sheepskin tanned with the hair retained.
Shoulder
That part of the hide between the neck and the ,ain body of the hide.
368
-------
lolT&ll required°if full hides were processed.
Skin
The pelt or skin of animals smaller than mature cattle; e^, pigskin.
sheepskin, calfskin.
Skiver
The thin layer shaved or cut off the surface of finished leather.
principally sheepskin.
Sludge
Staking
Sulfide
ionized sulfur. Expressed in mg/1 as S.
Suspended Solids (SS
constituents suspended in ^stewater «hich can usually be remove, by
sedimentation (clarification) or filtration.
Syntan
• •• ~««mva n « used in combination with
° ^
369
-------
Tanning
The chemicals derived
-
That portion O-F
are perked
Toggling
tanning
The total amount
-stevater.
-organic, in
n
Trimming
-
Trimming.c;
«
The process where the hair- io
«e halr ia removed from the hide
A control device placed in
measurement or control of the
370
-------
PRIORITY POLLU2MS
IELD"SAMPLING PROCEDURES
APPENDIX A
- SCREENING AND VERIFICATION
be estimated. Raw wastewater samples were o depending on
treatment or following min imal Pr^^^luentPsampies were
r secondary treatment.
The sampling method ^-l and
The samp and t
being sampled f o r sampling at both the «£ were used to account
points. automatic samplers an° ^°" ration. samples were taken
for short term ^^^V coSSS^ was prepared by combining the
every 15 minutes, and a 2U hr. ^P^1^^ f?owS recorded during each
samples on the basis of relative *«" aliquots were removed
collection period. From the 24-hr, f""^*1*^ ^Isic water quality
to satisfy the sample ™qwe*e£s of the^ o ^^ fQr the
paran^ters. The remaining volume ^e^|dcom|om the water supply.
72-hr composite. Blanks were =? f samples taken after
sampling requirements were not ^rigorous ^ £ for activated
secondary treatment hbeca«s^heh°^^ SmpiSg Period. Either grab
sludge may be c01^*1^ " the ?ana ; he entire lample retained, or an
SSSirUSJS 'warimployed^^e collected samples were mixed
for the composite.
normal vinyl tubing, the Cample collection i ^ samplers
le »~* The
normal vny u, ^ sa
backflushed before and after each sample »^~* as sampled.
ssr - —
The samples and blanks were kept on ice prior to shipment and shipped
in insulated containers.
371
-------
Method Develop and Procedures
Minor changes in
verification processes, ^Tl^*™*:*^ **
Volatile organics- The SSential methodology was the same.
=(«c«o«t« ,« Muis' "" -1"" into th.
.,
a duplicate water
except that the
372
-------
samples were acidified to PH 1 with HO. prior to extraction. The
extracts were then analyzed by GC/MS.
electron capture detector.
procedure
HN03/K2Cr207, and HNO3/HC104/H2S01.
Cyanide: Samples were analyzed for cyanide by a colorimetric method.
Sulfides were removed before distillation.
373
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APPENDIX B
netected In
Treated Effluents
acenaphthene
acrolein
acrylonitrile
1,2,4-trichlorobenzene
1,2-dichloroethane
hexachloroethane
1,1-dichloroethane
1, 1,2-trichloroethane
chloroethane
bis(chloroethyl)ether
bis (2-chloroethyl) ether
I^chloroethyl vinyl ether
2-chloronaphthalene
para-chloro-meta-cresol
2-chlorophenol
1,3-dichlorobenzene
1,1-dichloroethylene
1,2-dichloropropane
1,3-dichloropropene (cis- & trans)
2,4-dimethyIphenol
2,4-dinitrotoluene
2,6-dinitrotoluene
U-chlorophenyl phenyl ether
4-bromophenyl phenyl ether
bis- (2-chloroisopropyl) ether
bis-(2-chloroethoxy) methane
methyl chloride (chloromethane)
methyl bromide (bromomethane)
bromoform (tribromomethane)
bromodichloromethane
tr ichlorofluoromethane
dichlorodifluoromethane
dibromochloromethane
hexachlorobutadiene
hexachlorocyclopentadiene
2-nitrophenol
4-nitrophenol
2,U-dinitrophenol
4,6-dinitro-o-cresol
n-nitroso-dimethylamine
n-nitroso-di-n-propylamine
butyl benzyl phthalate
di-n-octyl phthalate
(benzo(a)anthracene)
375
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3,4-benzopyrene (benzo (b) pyrene)
3, 4-benzof luoranthene (benzo (b) fluoranthene)
2f rant^ (b*™ <*> ^orant
1 , 12-benzoperyiene (benzo (ghi) perylene)
6ean^acene
indeno 6:^e^anf^acene (dibenzo (a,k, nthracene)
******
tricMoro4thlen ****** M' ^^P^ylene pyren
a7ldrinChl°ride (chloroethylene)
dieldrin
chlordane
• -DDE (p,p«-DDX)
^
a-endosulfan
b-endosulfan
endosulfan sulfate
endrin
endrin aldehyde
heptachlor
heptachlor epoxide
a-BHC
b-BHC
r-BHC (lindane)
s-BHC
PCB-1242 (Arochlor 1242)
PCB-1254 (Arochlor 1254)
PCB-1221 (Arochlor 1221)
PCB-1232 (Arochlor 1232)
PCB-1248 (Arochlor 1248)
PCB-1260 (Arochlor 1260)
PCB-1016 (Arochlor 1016)
toxaphene
2.3, 1, 8-tetrachlorodibenzo-p-dioxin (TCDD)
376
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APPENDIX C
Toxic pollutants De*^ted In Treated
gffluents At Two Plants Or Less
trans-1,2-dichloroethene
1,1,1-trichloroethane
tetrachloromethane
(carbon tetrachloride)
1,1,2,2-tetrachloroethene
1,1,2,2-tetrachloroethane
chlorobenzene
hexachlorobenzene
n-nitrosodiphenylamine
1,2-diphenylhydrazine
benzidine
3,3•-dichlorobenzidine
nitrobenzene
isophorone
fluorene
fluoranthene
pyrene
diethyl phthalate
di-n-butyl phthalate
chrysene
2,U-dichlorophenol
377
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APPENDIX D
Pollutants Detected In Treated Effluents
At or Below The Limit Qf Detection
benzene
phenanthrene/anthracene
beryllium
cadmium
mercury
antimony
asbestos*
arsenic
selenium
silver
thallium
*Total chrysotile fiber count
379
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APPENDIX E
2,4,6-trichlorophenol
chloroform
1,2-dichlorobenzene
1,4-dichlorobenzene
ethylbenzene
methylene chloride (dichloromethane)
naphthalene
pentachlorophenol
phenol
bis (2-ethylhexyl) phthalate
toluene
chromium
copper
cyanide
lead
nickel
zinc
381
*U.S. GOVERNMENT PRINTING OFFICE : 1979 0-300-369/6427
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