United States
Environmental Protection
Agency
Research and Development
Water Engineering
Research Laboratory
Cincinnati, OH 45268
EPA/600/S2-86/032 May 1986
Project Summary
Treatment of Drinking Water by
Bromide Addition and
Powdered Activated
Carbon Adsorption
James M. Symons and Paul L. K. Fu
Although the phenomenon of the forma-
tion of trihalomethanes during the
disinfection of drinking water with free
chlorine has been known for over 10 years,
water utilities are still seeking effective
methods of control while maintaining good
disinfection. This brief study was con-
ducted to determine the feasibility of a
new approach to trihalomethane control.
Reports in the literature state that
predominantly bromine-substituted
trihalomethanes are adsorbed on activated
carbon better than are predominantly
chlorine-substituted trihalomethanes. The
goal of the proposed treatment scheme,
therefore, was to minimize the concentra-
tion of trihalomethanes in finished water
by adding bromide to water to deliberate-
ly create predominately bromine-
substituted trihalomethanes that could
subsequently be removed by powdered ac-
tivated carbon.
The proposed treatment process did
produce a water significantly lower in
trihalomethane concentration than the for-
mation potential in the source water. Two
factors, however, worked against achiev-
ing the goals of the proposed treatment.
One, when bromide is added to water,
more trihalomethanes are formed, as
expected. Two, apparently because of
competition from other organics, these ad-
ditional trihalomethanes, although
bromine-substituted, did not adsorb on the
powered activated carbon used in these
tests effectively enough to overcome the
production of additional trihalomethanes.
Furthermore, the residual bromide in the
water after adsorption that stimulated the
formation of trihalomethanes during post-
chlorination resulted in higher trihalo-
methane concentrations in simulated tap
water than would exist with conventional
treatment. Therefore, unless natural
waters would behave differently or
another powdered activated carbon would
be more effective in a competitive adsorp-
tion situation, this proposed treatment
scheme cannot be recommended.
A second phase of this study was to
determine the influence of pH, bromine
concentration, and time on the formation
of non-purgeable organic chlorine and non-
purgeable organic bromine, as measured
by neutron activation.
After 4 hours of exposure at constant
bromide concentration, the concentrations
of both parameters declined as the pH in-
creased from 6.2 to 9.2. Possibly because
of the slower oxidation of bromide at
higher pH, however, this trend was not
maintained when the pH reached 1O.7.
At constant time and pH, the concen-
tration of non-purgeable organic bromine
increased as the bromine concentration
increased, but the concentration of non-
purgeable organic chlorine was not con-
sistently correspondingly surpressed.
In the absence of bromide at constant
pH, the concentration of non-purgeable
organic chlorine increased as time in-
creased from 4 hours to 6 days. In the
presence of all three bromide concentra-
tions studied (4.2,8.4, and 16.8 ^mol/L),
however, the concentrations of both non-
purgeable organic chlorine and bromine
declined with time (from 4 hours to 6
days), sometimes to zero for non-
purgeable organic bromine.
This Project Summary was developed
by EPA's Water Engineering Research
-------
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report order-
ing information at back).
Background
The creation of chlorinated by-products
during the disinfection of drinking water
with free chlorine has been well
documented. The details of this reaction
and the various treatment options avail-
able to drinking water utilities to avoid high
concentrations of trihalomethanes (THMs)
in tap water have also been discussed in
depth in the research literature.
In spite of this research — much of it
successful — each of the techniques for
THM control currently available to water
utilities has disadvantages, either because
of cost, degree of effectiveness, or in-
terference with the disinfection process.
The purpose of this project was to in-
vestigate the feasibility of a new treatment
technique for THM control — a technique
based on the principle of enhancing the
formation of dibromochloromethane and
bromoform during the THM formation
reaction by adding a low concentration of
bromide, thereby consuming most of the
active precursor, and then lowering the
THM concentration by adsorption on
powdered activated carbon (PAC).
If most of the "active" (reactable)
precursor could be consumed during the
THM formation phase of the process, final
disinfection with free chlorine should be
possible without additional excessive THM
formation. Further, if the dibromochloro-
methane and bromoform formed during
the reaction phase of treatment could be
economically adsorbed on PAC, the
resulting tap water should meet the U.S.
Environmental Protection Agency's
(USEPA) Interim National Primary Drinking
Water Regulation (INPDWR) for total
trihalomethanes (TTHMs) of 0.10 mg/L.
Even if effective, however, this process will
only be considered successful if it does
not aggravate the formation of other
halogenated disinfection by-products
measured as non-purgeable organic
halogen (NPOX).
As an exploratory project, resources
(funds and time) were limited. Therefore,
after some preliminary experimentation to
set boundary conditions, only one final
test could be performed. Inconclusive,
unexpected, or unsuccessful results could
not be verified by repeat studies, under
similar or revised conditions.
Theoretical Considerations
Although removing all of the organic
2
carbon (TOO from drinking water as a
control strategy for preventing THM for-
mation has intrinsic advantages, only a
small percentage of the carbon in humic
acid reacts with free chlorine to be incor-
porated into THMs, indicating that only a
few sites on the precursor(s) are "active."
Therefore, theoretically, if the "active"
sites on the TOC in drinking water could
be made to react and the reaction prod-
ucts could be removed, the remaining TOC
should be unreactive. Driving the THM for-
mation reaction toward completion and
removing the reaction products should,
therefore, prevent further formation of
THMs in the distribution system during
finished water chlorination.
Further, enhancement of the THM for-
mation reaction will occur if the pH of the
water is elevated. Conversely, other
chlorination by-products, as measured by
non-purgeable organic chlorine (NPOCI),
do not form as readily at high pH.
In addition, because of the favorable ad-
sorbability estimated for CHBr2CI and
reported in the literature for CHBr3, the
THMs formed during free chlorination
might be easily removed by adsorption on
powdered activated carbon (PAC) if the
predominant THM species were CHBr2CI
and CHBr3.
Finally, this will occur if a small amount
of bromide is present or is added to the
water before free chlorination. The
presence of bromide increases the reac-
tion rate of THM formation. Counter to
these favorable features, however, is the
feature that as the bromide concentration
in water increases, so does the total quan-
tity of TTHMs formed at higher pH, even
though the TTHMs are mostly bromine-
substituted. An unknown factor in the pro-
posed treatment scheme is the influence
of the presence of bromide on other
disinfection byproducts, as measured by
NPOCI and non-purgeable organic bromine
(NPOBr).
Objectives
Based on these theoretical considera-
tions, this feasibility study was undertaken
with the following objectives:
1. Assess the potential of the pro-
posed treatment concept.
1A. Determine practical reaction
conditions of pH and bromide
concentration that will:
a. minimize the CHCI3 con-
centration,
b. maximize the CHBr2CI and
CHBr3 concentration,
c. avoid excessive TTHM
concentrations.
d. result in a high initial rate of
THM formation, and
e. result in a high conversion of
the total (6-day) precursor,
as measured by THM forma-
tion potential (THMFP), to
THMs in 4 hours.
1B. Determine the adsorbability of
the reaction products (THMs)
on PAC in the presence of
residual TOC and NPOX.
1C. Determine the adsorbability of
NPOCI and NPOBr on PAC in
the presence of residual TOC
and THMs.
1D. Convert as much potentially
reactive THM precursor to
THMs as possible in the reac-
tion phase, such that, after ad-
sorption treatment, the water
could be post-chlorinated
without significant THM
reformation.
2. Determine the influence of pH and
bromide concentration on the forma-
tion of NPOCI and NPOBr.
Experimental Procedures
Format/on of Trihalomethanes
and Non-Purgeable Organic
Halogen
The investigation of the influence of pH
and bromide concentration on the forma-
tion of THMs was carried out in 500 ml
amber bottles cleaned with a commercial
acid cleaning solution and sealed head-
space free with screw caps with Teflon® *
cap liners. The source of THM precursor
was a commercially available soil humic
acid (AHA), and the solvent was Houston
tap water that had been passed through
an adsorption bed of granular activated
carbon (GAC) and a mixed bed ion ex-
changer. Free chlorine was provided by
diluting commercial hypochlorite. Bromide
was added as potassium bromide (KBr).
Four bromide concentrations were studied;
0 mg/L, 0.5 mg/L KBr (4.2 (/mol/L), 1.0
mg/L KBr (8.4 ^mol/D, and 2.0 mg/L KBr
(16.8 f/mol/L). Before any experiment, a
6-day chlorine demand study was per-
formed to ensure that in the actual experi-
ment sufficient chlorine would be added
to provide a free residual of > 2 mg/L at
the end of the test.
In a typical THM formation test, four
replicate bottles for each condition were
filled with 5 mg/L of AHA in Dl water, and
the appropriate pH buffer, KBr, and free
* Mention of trade names or commercial products does .
not constitute endorsement or recommendation for •
use.
-------
chlorine dose were added. As a compan-
ion, four control replicate bottles were
prepared. These controls were identical to
the test samples except for the lack of any
AHA. All samples were held at room
temperature, about 25 °C. After exposure
times of 4 hours (0.17 day), 1 day, 3 days,
and 6 days, one test bottle and one con-
trol bottle was dechlorinated, in turn, with
sodium sulfite. After the reducing agent
was added, 65-mL, clean (solvent rinsed
and baked at 150 °C for 1 hour) amber
bottles were carefully filled and capped
head-space free with screw caps with
Teflon® faced septa. These bottles were
stored at 4°C until THM analysis. After
the 65-mL bottles had been filled, separate
250-mL amber glass bottles were also
filled head-space free for those cases
where NPOX analyses were also to be per-
formed. These bottles were stored at 4°C
until the particular experiment was over;
then the bottles were shipped to the
analytical laboratory by overnight courier.
Analytic Procedures
To analyze for THMs, a liquid-liquid ex-
traction (LLE) procedure was used with
pentane as the extraction solvent. THMs
were measured by gas chromatography
with an electron capture detector.
Procedures for Adsorption of
Trihalomethanes and
Non-Purgeable
Organic Halogen
The test started with seven, square, 2-L
jars being filled with 1.5 L of the GAC-
treated Dl water. To each of the jars was
added 5 mg/L of AHA, 1 mg/L KBr (8.4
^mol/L Br), 500 mg/L NaN03 (to prevent
the adsorption of interfering inorganic
chloride and bromide), 10 mg/L free
available chlorine (FAQ, and 35 mg/L
alkalinity as CaCO3 (NaHCO3); the pH
was adjusted to 6.9 with H2SO4. The
seven jars (open) were then slowly mixed
in a test apparatus for 4 hours.
After the reaction period was com-
pleted, 25 mg/L of Na2S03 was added as
a dechlorinating agent to six of the jars
and the jars were sampled for THM and
NPOX analysis. The seventh jar continued
to be slowly mixed for 2 more hours. This
control jar was not given any further treat-
ment, but was sampled for THMs and
NPOX after 4 and 6 hours of reaction time
to determine losses of THMs and NPOX,
if any, to the atmosphere.
After dechlorination, each of the six jars
received one of the following doses of
PAC: 0, 5, 10, 25, 50, and 100 mg/L. After
30 minutes of contact with the adsorbent
with adequate mixing to prevent signi-
ficant settling, 35 mg/L of NaHCO3 (to
ensure adequate alkalinity for good
coagulation) and 100 mg/L of alum were
added to each jar. All jars were then sub-
jected to 1 minute rapid mix, 30 minutes
of flocculation (slow mix), and 1 hour of
settling.
The supernatant liquor was then
decanted and filtered before being ana-
lyzed for THM and NPOX. After the super-
natant liquor was removed, the sludge was
placed in a graduated cylinder for further
concentration. Finally, the concentrated
sludge was membrane filtered before
neutron activation analysis for NPOX.
Water samples were analyzed for NPOX
according to USEPA Method 450.1.
After removal of the sludge, the super-
natant liquors were rechlorinated and
stored in bottles for 3 days to simulate
post-chlorination and passage through a
distribution system. The samples were
then dechlorinated and analyzed for THM
and NPOX. Each of the six samples were
compared with the 3.5 day, pH 7, 25 °C
THMFP of the source water to determine
the effect of the treatment scheme.
Summary of Results
From the matrix of experimental condi-
tions and based on the constraints chosen,
the most practical reaction conditions for
the formation of THMs were: pH, 7±;
bromide concentration, 8.4/^mol/L (1 mg/L
KBr); exposure time, 4 hours.
At the chosen conditions, after the
4-hour reaction period, the treated water
had the following analysis:
Analyte
CHC/3
CHBrC/2
CHBr2CI
CHBr3
TTHM
NPOCI
NPOBr
0.28
0.28
0.67
0.25
1.48
3.29
1.77
33
46
140
63
282
117 as Cl
63 as Cl
Under the chosen reaction conditions,
for a sample containing 5 mg/L of AHA as
the THM precursor, 57 percent of the
6-day total THMFP, "total" precursor, was
converted to TTHM, and the TTHM was
62 percent (CHBr2CI + CHBr3) and only
19 percent CHCI3, on a ^mol/L basis.
After a 4-hour reaction period, simple
alum coagulation removed 16 percent of
the TTHM, 45 percent of the NPOX, 35
percent of the NPOCI, and 60 percent of
the NPOBr.
This same treatment resulted in 43 per-
cent less TTHM in a simulated tap water
sample (3-day distribution time) than in
untreated source water and 4 percent less
NPOX, 2 percent less NPOCI, and 7 per-
cent less NPOBr.
Treating the water with 50 mg/L of PAC
for 30 minutes before alum treatment
removed an additional 10 percent of the
TTHM and an additional 25 percent of the
NPOX, 28 percent of the NPOCI and 19
percent of the NPOBr when compared
with simple alum coagulation removals.
Increasing the PAC dose to 100 mg/L
removed an additional 38 percent of
TTHM and an additional 22 percent of
NPOX, 36 percent of the NPOCI, and
negative 6 percent of the NPOBr beyond
alum treatment.
Treating the water with 50 mg/L of PAC
before alum coagulation removed 68 per-
cent of the 335 /jg/L, 3.5-day THMFP in
the source water and 60 percent of the
3.5-day NPOX formation potential
(NPOXFP1-67 percent of the 3.5-day
NPOCIFP and 53 percent of the 3.5-day
NPOBrFP. Increasing the PAC dose to 100
mg/L resulted in 77 percent removal of
3.5-day source water THMFP and 65 per-
cent removal of 3.5-day source water
NPOXFP-70 percent of the NPOCIFP and
63 percent of the NPOBrFP.
The 50-mg/L-PAC-treated simulated tap
water contained 0.11 mg/L TTHM and
0.06 mg/L NPOX as Cl and the 100-mg/L-
PAC-treated simulated tap water con-
tained 0.08 mg/L TTHM and 0.06 mg/L
NPOX as Cl.
The proposed treatment approach was
successful in lowering a high concentra-
tion TTHM formation potential in a
simulated source water; it produced a
simulated tap water that met the USEPA
Regulation for TTHM without excessive-
ly increasing the concentration of other
disinfection by-products, as measured by
NPOX.
When compared with conventional
treatment, however, the chosen PAC was
unable, in competition with the other
organic compounds present, to adsorb the
additional THMs formed when bromide
was added. Conventional treatment (no
bromide added) produced waters contain-
ing TTHM concentrations of 33.8 pig/L and
28.5 ^g/L for PAC doses of 50 and 100
mg/L, respectively, whereas the cor-
responding waters containing 1 mg/L KBr
had TTHM concentrations of 60.5 ^g/L
and 58.3 f*g/L. Three-day THMFP values
were slightly higher in the samples con-
taining bromide as well.
With the PAC used, adsorption of
bromoform (as an example, THM) was 10
to 50 times less than adsorption in
previous studies performed in "organic-
3
-------
free" water. This was attributed to the
competition from other organic com-
pounds for adsorption sites.
In "organic-free" water, Nuchar® S-A
was equal to or better than reports in the
literature for the adsorption of chloroform,
but was poorer for the adsorption of
bromoform.
In contrast to the THMs, the organic
compounds contributing to the remaining
THMFP were well adsorbed on the PAC,
being completely removed by the 25, 50,
anc 100 mg/L PAC dose.
NPOCI was poorly adsorbed by the PAC
used and NPOBr was not adsorbed at all.
The remaining NPOCI and NPOBr forma-
tion potential was hardly adsorbed at all
in this study.
Only 0.24 ymol/L of 3-day THMFP re-
mained in the water after rechlorination of
the alum-coagulated and settled water. In
contrast, 1.72 jmiol/L of 3-day NPOXFP
was found after this same water was
post-chlorinated.
NPOCI and NPOBr could be analyzed in
the sludges by neutron activation, but the
mass balances indicated greater than 100
percent recovery of removed NPOCI and
NPOBr.
In addition to the major objective of this
study, an investigation was also con-
ducted to determine the influence of the
variables, pH, bromide concentration, and
exposure time on the resulting concentra-
tions of NPOCI and NPOBr, as determined
by neutron activation. The following
statements summarize the findings of this
phase of the investigation:
NPOBr concentration declined more as
pH increased than did NPOCI concentra-
tion, at a constant bromide concentration.
Although the NPOBr concentration
increased as the bromide concentration
increased, the NPOCI concentration was
not consistently suppressed, as was the
case with TTHMCI.
In the presence of all three bromide con-
centrations studied, as exposure time
increased, the concentrations of NPOCI
and NPOBr generally declined, sometimes
to zero for NPOBr. In the absence of
bromide, the concentration of NPOCI con-
tinued to increase from 4 hours' to 6 days'
exposure, at all four pH values studied.
At a constant bromide concentration,
after 4 hours' exposure, the distribution of
chlorine to bromine is not influenced much
by pH, either in the THMs or the NPOXs.
At a constant pH and 4 hours of ex-
posure, the total quantity of halogen
substituted into organic matter was about
the same at bromide concentrations of 0,
4.2, and 8.4 ^mol/L When 2 mg/L of KBr
(16.8 ^mol/L) was added to the water,
however, total halogen substitution rose.
The full report was submitted in fulfill-
ment of Cooperative Agreement No.
CR-811659-01-0 by the University of
Houston under the sponsorship of the U.S.
Environmental Protection Agency.
James M. Symons and Paul L K. Fu are with the University of Houston, Houston
TX 77004.
Alan A. Stevens is the EPA Project Officer (see below).
The complete report, entitled "Treatment of Drinking Water by Bromide Addition
and Powdered Activated Carbon Adsorption," (Order No. PB 86-171 410/AS;
Cost: $11.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PA
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-86/032
006324U
-------
United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA/600/S2-86/033 May 1 986
x°/EPA Project Summary
Field Investigation and
Evaluation of Land Treating
Tannery Sludges
Robert M. Lollar and Waldo E. Kallenberger
Land treatment of wastewater
sludges from tannery processes has
been investigated during a five-year
field plot study. The experimental de-
sign included eight field test plots re-
ceiving selected applications of three
types of tannery sludges over a three-
year period.
1. Two 0.2 hectare plots received
beamhouse (hair-bum) sludge at two
different sludge application rates (110
mt/ha and 220 mt/ha sludge). The 110
mt/ha sludge loading rate was selected
to provide the assumed optimum load-
ing of proteinaceous nitrogen.
2. Two total chromium loading rates
(2240 kg/ha and 4480 kg/ha total
chromium) were applied to two 0.2
hectare plots that received trivalent
chromium-containing (chrome) sludge
and to two 0.2 hectare plots that re-
ceived mixed tannery (hair-burn and
chrome) sludge.
3. A single 0.1 hectare plot received a
triple total chromium loading (6720 kg/
ha) of the mixed sludge, and a single 0.2
hectare control plot received no sludge
addition.
The five-year study included analyses
of sludge, soil core, plant-tissue, and
soil pore and runoff water samples to
evaluate the feasibility of land treat-
ment of tannery sludges. The data gen-
erated indicated that land treatment is
potentially an environmentally accept-
able technology for management of
wastewater sludges from trivalent
chromium tanneries; however, waste
application rates must be carefully con-
trolled.
The applied trivalent chromium ap-
peared to remain primarily in the top-
soil without any detectable oxidation
to hexavalent chromium. Transport of
trace quantities of chromium in soil
runoff water appeared to be associated
with movement of soil particles. Appli-
cation levels of tannery sludges con-
taining hair-burn wastes will be limited
by the mineralization rate of the pro-
teinaceous nitrogen and the crop inor-
ganic nitrogen requirements. Elevated
salt concentrations of the hair-burn
sludges also will require specific con-
sideration.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Environ-
mental Research Laboratory, Ada, OK,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
The main objective of this project was
to characterize the major technical and
environmental aspects associated with
the utilization of land treatment technol-
ogy for the disposal of tannery waste-
water sludges. Tanneries in the United
States primarily utilize trivalent chro-
mium coordination compounds in the
conversion of skin and hide substance
into leather. Total current annual gener-
ation of chromium-containing waste-
water sludges is estimated to be ap-
proximately 25,000 metric tons (dry
basis).
Tannery solid wastes containing
chromium have for many years been
applied to agricultural soils since they
-------
contain proteinaceous, slow-release ni-
trogen. Wickliff, et al. (Water, Air, Soil
Pollution 17:61-74, 1982) published the
results of greenhouse investigations on
the application of trivalent chromium-
containing tannery wastewater sludges
to two soils. Crops utilized were tall fes-
cue, hybrid sweet corn and bush beans.
These workers concluded that tannery
sludge may be applied to soils as a fer-
tilizer amendment without adversely af-
fecting soil chemical properties. Fur-
thermore, the amount and frequency of
sludge application should be deter-
mined by: total and available nitrogen;
total salt content; total and available
chromium; and soil organic matter.
However, there has not been a defini-
tive field study which would provide
data on the design, operation and clo-
sure of tannery land treatment sites. A
five-year field site investigation utilizing
tannery wastewater sludges was de-
signed to provide the necessary data.
The project had three specific objec-
tives:
1. To assess potential adverse im-
pacts of land treatment on various
environmental sectors.
2. To estimate the accumulation,
degradation and migration of soil
contaminants.
3. To provide data for the optimiza-
tion of site design, operation and
closure.
Procedure
A suitable field site was located within
the Scott Creek Valley in western Santa
Cruz County, California. The actual
study site was located on a small, al-
most level marine terrace remnant lying
about 115m above the floor of the val-
ley. The soils of the marine terraces are
about 1.5 m deep with a thick, well de-
veloped B horizon; they have low per-
meability.
Test plots, 0.2 hectare in area, were
constructed at the site with fencing,
wells, berms, roadways and drainage
systems. PVC pipes connected the col-
lection boxes at the base of each test
plot to concrete sedimentation vessels
equipped with V-notch weirs for dis-
charge measurement.
Two types of tannery sludges were
applied to the field site test plots at four
different time intervals from June 1981
until October 1983. The proper amount
of each sludge was spread on the ap-
propriate experimental plot and incor-
porated into the topsoil to a depth of
approximately 15 cm by tilling.
Analyses of sludge, soil core, grass,
and soil pore and runoff water samples
from each plot were conducted
throughout the project period. Parame-
ters receiving special attention were:
chromium, total Kjeldahl nitrogen, salt,
and nitrate-nitrogen.
Results
Although the project data indicated
that the applied trivalent chromium
remained predominantly in the plot top-
soil, there was some apparent move-
ment of trace level amounts of chro-
mium in runoff water which appeared to
be associated with movement of soil
particles. Hexavalent chromium was
never detected in any of the sludge, soil
core, or soil pore and runoff water sam-
ples. Data from Ribgut grass tissue
analyses indicated no increase in chro-
mium at the 2240 kg/ha sludge loading
level. At the mixed sludge triple loading
(6720 kg/ha)'level, enhancement in
plant tissue chromium was suggested
by the data; however, the results were
considered inconclusive due to the lim-
ited number of samples analyzed.
Trivalent chromium concentrations
found in the soil below the plow zone
before the first and following the last
sludge applications were:
Chromium - mg/kg
Soil Depth
30 - 60 cm
60 - 90 cm
Background
29-49
24-49
May 1984
11-73
33 - 102
However, the chromium material bal-
ance in the top 15 centimeters of soil
was not complete; as shown by the fol-
lowing:
Sampling and analytical variability for
both sludges and soils contribute to this
incomplete recovery. The data obtained
during the five-year study indicate a sig-
nificant increase in the chromium level
in the topsoil of the five treated plots.
Mineralization rates for the proteina-
ceous nitrogen in tannery sludges cur-
rently are not available in the literature
and were not determined during this
study. Soil water samples in March 1985
from the triple loaded plot had a median
nitrate-nitrogen value of 42 mg/l. It is
assumed that leaching problems asso-
ciated with land application of tannery
sludges would be eliminated if sludge
application rates were limited to the op-
timum loading level which would pro-
vide for the nitrate-nitrogen demands of
the plant growth. Furthermore, the proj-
ect data indicated that the salt content
of the hair-burn beamhouse sludges
should be considered in loading deci-
sions.
Conclusions
Land treatment provides a potentially
environmentally acceptable technology
for management of tannery wastewater
sludges from trivalent chromium tan-
nery processes if sludge application
rates are carefully controlled. The uti-
lization of land treatment technology for
management of these sludges must in-
clude the following considerations:
1. Chromium tannery wastewater
sludges are characterized by a signifi-
cant organic Kjeldahl nitrogen content
(2 to 4.5 percent) which primarily results
from the proteinaceous materials in the
animal hides which are converted into
leather in the tannery. Therefore, land
treatment of these sludges should be
guided by the mineralization rates of the
proteinaceous nitrogen and by the inor-
ganic nitrogen demands of the plants
grown on the treatment site.
Chromium - mg/kg
Plot Loading
Cr Sludge - 1
Mixed Sludge - 1
Cr Sludge - 2
Mixed Sludge - 2
Triple Loading
Estimated
Loading
1100
1284
2130
2310
3530
Average
640
1390
1620
1190
2320
Found
Range
590-700
1240-1540
1380-1800
1080-1300
2010-2500
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2. Chromium tannery wastewater
sludges are characterized by significant
salt contents (4 percent sodium on a dry
basis from unhairing wastewater
sludges and 2.7 percent from the
chromium-containing wastewater
sludges). Land application of these
sludges may result in poor grass germi-
nation and weed intrusion; therefore,
careful attention should be paid to these
possible salt effects, especially when
the unhairing wastewater sludges are to
be applied.
3. Trivalent chromium in tannery
wastewater sludges remains primarily
in the topsoil after land treatment, how-
ever, there may be some limited trans-
port of chromium in soil pore and runoff
water. The transport in runoff water is
assumed to be associated with soil par-
ticle movement.
4. Hexavalent chromium was not de-
tected during this five-year field study;
therefore, it is assumed that applied
travalent chromium will not oxidize to
the hexavalent form in this soil environ-
ment.
Recommendations
This five-year field plot study was the
first in-depth field investigation of the
land treatment of chromium tannery
wastewater sludges. The study.results
disclosed certain areas in which the
project efforts could have been im-
proved by additional prior information.
The following recommendations are
made for further study which would fa-
cilitate future utilization of land treat-
ment technology for management of
tannery wastewater sludges:
1. Improved sludge and soil sam-
pling protocols which recognize the
high analytical heterogeneity of the
substrates should be developed.
2. Inter-laboratory analyses of sludge
and soil samples by EPA Method 3050,
SW846, Test Methods for Evaluating
Solid Wastes, 1982, showed satisfactory
agreement for total chromium and cal-
cium. Future work involving tannery
waste should restrict sludge and soil
analysis to EPA Method 3050, SW846.
3. Improved agricultural practices to
main more uniform sludge incorpora-
ion into the topsoil and to secure grass
)r other crop growth are needed. The
jffect of the high sodium content of the
lair-burn sludge on the weed intrusion
nto the test plots also requires further
:onsideration.
4. Proteinaceous nitrogen mineral-
zation rates for wastewater sludges
from chromium leather tanneries were
not found in the literature. Combined
laboratory and field studies directed to-
ward these mineralization rate determi-
nations are recommended.
5. Chromium transfer from the top-
soil appeared to be limited; the chro-
mium which was transported in soil
water runoff appeared to be associated
primarily with movement of soil parti-
cles. Further field studies are recom-
mended to determine the ultimate form
in the topsoil of the added chromium.
Dehydration of trivalent chromic hy-
droxide forms very insoluble trivalent
chromic oxide. Soil physical chemical
studies to provide data on the physical
form of the chromium in the topsoil
would be desirable to establish the up-
per permissible limit for trivalent chro-
mium addition to topsoils.
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Robert M. Lollar and Waldo E. Kallenberger are with Tanners' Council of America.
Cincinnati. OH 45221-0014.
Don A. Clark is the EPA Project Officer (see below).
The complete report, entitled "Field Investigation and Evaluation of Land Treating
Tannery Sludges," (Order No. PB 86-176 542/AS; Cost: $16.95, subject to
changej will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
Ada, OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-86/033
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