United States
Environmental Protection
Agency
Municipal Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-117 Sept. 1984
Project  Summary
Chlorinated  Organic  Compounds
in  Digested,  Heat-Conditioned,
and  Purifax-Treated  Sludges

Albert B. Pincince and Christopher J. Fournier
  A study was conducted to investigate
the  effects  of sludge stabilization
methods on the production of priority
pollutants  and chlorinated organics.
Three  stabilization  methods  were
examined in pilot studies— the Purifax*
process, anaerobic digestion, and heat
conditioning.
  Results showed that sludge processed
by  the  Purifax process  at chlorine
dosages normally used in processing
wastewater sludges contains 2 to >14
times the total organic chlorine in raw
sludge.  Both insoluble and  soluble
forms of organic chlorine increase with
chlorine dosage. According  to the
study,   most  of  the  chlorinated
compounds are associated with the
solid fraction of the sludge. More than
94 percent of the total organic chlorine
is insoluble,  and about 97 percent of
that is associated with the cake. Using
the Tchebychev inequality, it was deter-
mined that the probability that Purifax
treatment  produces the  same
concentration  of  insoluble  organic
chlorine in sludge  cake as the other
stabilization  processes is  less than
22.5 percent (assuming a unimodal
distribution, this probability is less than
10 percent).  Leachate obtained by the
EPA extraction  procedure contained
less than 0.2 percent of the  organic
chlorine in the sludge cake after Purifax
treatment.   In  analyses for  priority
pollutants, less than 16 percent of the
chlorinated material was identified. A
new analytical technique  using
ionization/gas chromatography/mass
*Mention of trade names  or commercial products
does not constitute endorsement or recommenda-
tion for use
spectrometry gave results inconsistent
with the priority pollutant analyses.

  This Project Summary was ifeve/oped
by EPA's f(^unicipal Environmental Re-
search 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 ordering information at
back).

Introduction
  In the Purifax process, chlorine gas is
added to wastewater sludge, septage, or
digester  supernatant  to stabilize and
condition the material before dewatering
and disposal. The chlorine dosage is high
(50,000 mg/kg of dry solids), and the
residual chlorine  concentration is also
high (roughly 60 to 400 mg/L). Because
of these  high concentrations, concern
has existed  that the process  might
produce  unacceptable  levels  of
chlorinated organics. The objective of this
study was  therefore to determine the
effects of stabilization processes on the
production  of  priority  pollutants  and
chlorinated organics. Three stabilization
methods  were examined-the Purifax
process, anaerobic digestion, and heat
conditioning.

Procedures
Sources of Sludge
  To allow for variability in sludges from
plants receiving  different  types  of
wastewater, sludges were tested from
three  wastewater treatment  plants--
Amherst,  Massachusetts, Willimantic,
Connecticut; and  Pittsfield, Massachu-
setts  The  Amherst  plant  serves a

-------
residential  area  that  has developed
around  several college  campuses. The
Willimantic  plant  receives flow from
some 20 industries, which constitutes
about 25 percent of the total flow for the
plant. Industrial processes include dyeing
of cotton and  synthetics, production of
woolen  fabrics, and poultry processing.
The  Pittsfield  plant receives  about  5
percent of  its  total flow from  two
industries—General   Electric  and  the
Crane Paper  Company. The  General
Electric  plant  discharges  pretreated
wastes containing phenolic compounds.
The Crane Paper Company's main dis-
charge consists of  liquids  from  a pulp
digestion process.

Anaerobic Digestion
  The feed material added  to the batch
digesters included mixtures of rawsludge
and digested sludge seed in two ratios of
raw  sludge to seed by volume, 25/75,
and 50/50.
  Digestion temperature was maintained
at 35°C, and the digester contents were
continually mixed with digester gas. The
tests lasted 28 days. Gas production was
very low by that time, and changes in total
volatile  solids were  minimal. Also, the
total  volatile   solids  in  the   sludge
approached  the  concentration  in  the
digester seed.

Heat Treatment
  Bench-scale  heat-conditioning tests
were  conducted on a 1 -L autoclave. This
unit was used as a batch heat-condition-
ing system in which approximately 0.8 L
of sludge was mixed and heated for  30
min to 180°C at 970 kPa. (Full-scale heat-
conditioning units operate at  120° to
220°C and 1700 to 2000 kPa for 20 to 30
min.)

Purifax Pilot Tests
  The pilot plant tests were conducted to
provide sludges with high, medium, and
low chlorine residuals (as compared with
medium residuals  at full-scale Purifax
processing  plants).   Medium residuals
were  those from 150 to  200 mg/L; high
residuals were 280 to 350 mg/L; and low
residuals were 60 to 120 mg/L.

Results
  Only Purifax-treated sludges showed
substantial  increases in total  organic
chlorine after  processing (Figure 1). In
these tests and others, the total organic
chlorine  content   in  Purifax-treated
sludge is 2 to >14 times that in raw, heat-
conditioned,  or  digested  sludge. The
   200
   700
                                   Amherst Sludge

   200
6
.0
I
a  ;oo
   roo
                                   Pittsfield Sludge

                                 Willimantic Sludge
             I
             to
I
                          <3
.0
,*5
•6
                                       if
                         II
h
                                                                  .
 Figure 1.    Effects of stabilization processes on total organic chlorine levels in sludge.
 only  exception  is  the  concentration
 shown for heat-conditioned sludge from
 Pittsfield, which appears to be an error.
 These ratios are for a chlorine residual of
 about 170 mg/L (a  medium residual),
 which occurred after a chlorine dosage of
 about 1500  mg/L.  The  dosage  and
 residual are comparable to those used at
 Purifax plants.
   The concentrations  of  soluble  and
 insoluble organic chlorine increase with
 increased chlorine residual or chlorine
 dosage. There is scatter to the data for all
               four  combinations,  but  a statistically
               significant  line of  fit can  be  drawn
               through  the  data.  Coefficients  of
               determination  (r2) range from 0.18  to
               0.32. For the number of samples in each
               case, the trends are significant at 1.5- to
               8.1 -percent levels.
                 The tests showed that more than 94
               percent of the total organic chlorine in all
               tested sludges is insoluble. For Purifax-
               treated sludge, more than 97 percent of
               the organic chlorine  is insoluble. Since
               most of the organic chlorine is insoluble.

-------
nearly all of it ends up in the cake after
centrifuging.  The data show that less
than  3 percent  of the total  organic
chlorine in processed  sludge is in  the
centrate. In the Purifax-treated samples,
only  1.4 percent of the chlorine was in
the centrate. And of the portion in  the
cake, less than 0.2 percent was leached
by the EPA extraction procedure.
  Tests were conducted to quantify  and
identify chlorinated compounds present
before and  after processing in sludge
from the Amherst wastewater plant (the
one  serving  a  residential  area).  Test
methods included those for quantifying
organic priority pollutants and a new
analytical technique--ionization/gas
chromatography/mass  spectrometry.
The tests for priority pollutants identified
only  a  portion  of  the   chlorinated
compounds.  For  sludge samples, tests
identified  less  than 16 percent of  the
chlorinated material in feed sludge  and
less than  2.6 percent in Purifax-treated
sludge. For cake samples, tests identified
less than 0.1  percent  of  the  residual
chlorinated compounds. Though the new
analytical   technique  identified  com-
pounds with properties similar to those of
some chlorinated priority pollutants, the
two techniques identtfied different com-
pounds.
  Purifax  treatment  of the  Amherst
sludge produced  an approximate 5-fold
increase in total chlorinated organics. It
appears that the identifiable chlorinated
organic compounds are approximately
the  same  before  and after   Purifax
processing,  although proportions have
shifted. The  reliability of the analytical
technique for  quantifying  the various
organic compounds is  not sufficiently
trustworthy  to  permit statements about
quantitative changes in these compounds.
Confirming work is recommended, prefer-
ably  with  improved  extractions  and
analytical techniques.
  The full  report  was submitted in
fulfillment of Contract No. 68-03-2803 by
Camp Dresser  & McKee Inc. under the_ ^
sponsorship  of the U.S. Environmental««,
Protection Agency.
Albert B. Pincince and Christopher J. Fournier are with Camp, Dresser & McKee,
  Boston. MA €2108.
James A. Ryan is the EPA Project Officer fsee below).
The complete report, entitled "Chlorinated Organic Compounds in Digested, Heat-
  Conditioned,  Purifax-Treated Sludges." (Order  No. PB  84-212  695; Cost:
  $13.00, 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:
        Municipal Environmental Research Laboratory
        U.S. Environmental Protection Agency
        Cincinnati. OH 45268
                                •ft U S. GOVERNMENT PRINTING OFFICE; 1984 — 759-015/7803

-------
United States
Environmental Protection
Agency
Center for Envi,
Information
Cincinnati 0
isearch
Official Business
Penalty for Private Use $300

-------