US Army Corps
                                       of Engineers
                                       Cold Regions Research &
                                       Engineering Laboratory
Assessment of the treatability of
toxic organics by overland flow
   APPLIED
 WASTEWATER
GRASS AND
VEGETATIVE
   LITTER
                            VOLATILIZATION
                            FLOW
                                         WASTEWATER
                                         COLLECTION
        VOLAT  ZATION
            SORPTION

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OVERLAND FLOW RESEARCH REPORTS

   This is one of a series of reports on wastewater treatment by overland flow published by the
U.S. Army Cold Regions Research and Engineering Laboratory.  Other published and available
reports on this topic are listed below.

Jenkins, T.F. et al. (1979) Prototype overland flow test data:  June 1977-May 1978. CRREL
Special Report 79-35.

Jenkins, T.F., D.C. Leggett, C.J. Martel and H.E. Hare (1981) Overland flow:  Removal of toxic
volatile organics. CRREL Special Report 81-1.

Martel, C.J., T.F. Jenkins and A.J. Palazzo (1980) Wastewater treatment in cold regions by over-
land flow. CRREL Report 80-7.

Martel, C.J., T.F. Jenkins, C.J. Diener and P.L. Butler (1982) Development of a rational design
procedure for overland flow systems.  CRREL Report 82-2.

Palazzo, A.J. (1982)  Plant growth and management for wastewater treatment in overland flow
systems. CRREL Special Report 82-5.
   For conversion of SI metric units to U.S./British
customary units of measurement consult ASTM
Standard E380, Metric Practice Guide, published
by the American Society for Testing and Materials,
1916 Race St., Philadelphia, Pa. 19103.

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CRREL Report 83-3
January 1983
Assessment of the treatability of
toxic organics by overland flow
T.F. Jenkins, D.C. Leggett, L.V. Parker, J.L. Oliphant
C.J. Martel, B.T. Foley and C.J. Diener
 Prepared for
 U.S. ENVIRONMENTAL PROTECTION AGENCY
 Ajaptovad lot public usiaase; distribution unlimited

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                      Unclassified
SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)
               REPORT DOCUMENTATION PAGE
          READ INSTRUCTIONS
      BEFORE COMPLETING FORM
 1. REPORT NUMBER

   CRREL Report 83-3
                                                2. GOVT ACCESSION NO,
                                                                       3. RECIPIENT'S CATALOG NUMBER
4. TITLE (and Subtitle)

ASSESSMENT OF THE TREAT ABILITY OF
TOXIC ORGANICS BY OVERLAND FLOW
                                                                       5. TYPE OF REPORT & PERIOD COVERED
                                                                      6. PERFORMING ORG. REPORT NUMBER
7. AUTHORS
T.F. Jenkins, D.C. Leggett, L.V. Piker, J.L. Oliphant,
C.J. Martel, B.T. Foley and C.J. Diener
8.  CONTRACT OR GRANT NUMBER(s)

  Interagency Agreement
  USEPA AD96-F-1402-0
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Army Cold Regions Research and Engineering Laboratory
Hanover, New Hampshire 03755
10.  PROGRAM ELEMENT, PROJECT, TASK
    AREA & WORK UNIT NUMBERS
11.  CONTROLLING OFFICE NAME AND ADDRESS
U.S. Environmental Protection Agency
R.S. Kerr Environmental Research Laboratory
Ada, Oklahoma  74820	
12.  REPORT DATE
    January 1983
13.  NUMBER OF PAGES
           59.*
 14. MONITORING AGENCY NAME ft ADDRESSf// different from Controlling Oftlce)
15.  SECURITY CLASS, (of this report)
                                                                        Unclassified
                                                                       ISa.  DECLASSIFI CATION/ DOWN GRADING
                                                                           SCHEDULE
16.  DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.
17.  DISTRIBUTION STATEMENT (of the abstract entered in Block 20, II different from Report)
18.  SUPPLEMENTARY NOTES
19.  KEY WORDS (Continue on reverse aide it necessary and Identify by block number)
Land treatment
Organic compounds
Overland flow
Wastewater treatment
20%.  ABSTRACT (Cbzitfaue oa rvvers* sfoto ff ncctwaacy and. Identity by block number)
  The removal efficiency for 13 trace organics in wastewater was studied on an outdoor, prototype overland flow land
treatment system. The removal for each of these substances was greater than 94% at an application rate of 0.4 cm/hr
(0.12 m3/hr-m of width). The percent removals declined as application rates were increased. The rate of removal from
solution was described by the sum of two mass-transport-limited, first-order rate coefficients representing volatilization
and sorption. A model based on the two-film theory was developed; the observed removal rate coefficients were re-
gressed against three properties of each substance:  the Henry's constant, the  octanol-water partition coefficient and the
molecular weight. The dependence of the removal process on temperature was studied and is included along with
                     EDITION OF  MOV 65 (S OBSOLETE
                                                                     Unclassified
                                                        SECURITY CLASSIFICATION OF THIS PAGE fWttm Data Entered)

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                Unclassified
SECURITY CLASSIFICATION OF THIS PAGE(T?han Data Entand)
  20.  Abstract (cont'd).

  average water depth in the model.  The decrease in removal rate as temperature declined is supported by the known
  dependence of Henry's constant and diffusivity on temperature. The model was validated on a second overland flow
  system.  The surface soil concentrations of the trace organics determined at the end of the experiment suggest that a
  secondary mechanism renews the surface activity rapidly enough so that contaminants do not build up on the surface,
  with the possible exception of PCB. Biodegradation is suggested as the predominant secondary mechanism rather than
  volatilization because substances less volatile than PCB were not found at the end of the experiment.
                                                                  Unclassified
                                                     SECURITY CLASSIFICATION OF THIS PAGEfHTien Data Entered)

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PREFACE

   This report was prepared by Thomas F. Jenkins, Research Chemist; Daniel C. Leggett, Research
Chemist; Louise V. Parker, Microbiologist; Dr. Joseph L. Oliphant, Research Physical Scientist;
and Brian T. Foley, Physical Science Aid, of the Earth Sciences Branch, Research Division, and
C. James Martel, Environmental Engineer, and Carl J. Diener, Civil Engineering Technician, of the
Civil Engineering Research Branch, Experimental Engineering Division, U.S. Army Cold Regions
Research and Engineering Laboratory (CRREL), Hanover, New Hampshire.
   The authors gratefully acknowledge the assistance of Patricia Butler, Stephen Mueller, Susan
Ossoff and Lisa Campbell of CRREL for providing analytical assistance, Antonio J. Palazzo and
and John M. Graham for assistance in harvesting and vegetation sampling on the CRREL overland
flow system, and Dr. Robert Smith of the Civil Engineering Department, University of California
at Davis, for cooperation in the field study conducted at the Davis overland flow site.
   This project was funded under Interagency Agreement USEPA AD96-F-1402-0 by the U.S.
Environmental Protection Agency, Bert Bledsoe, Project Officer, R.S. Kerr Environmental Re-
search Laboratory (RSKERL). The authors acknowledge the support and encouragement of Mr.
Bledsoe and Dr. Ray Thacker, EPA Headquarters, throughout this effort.  Although the research
described in this report has been  funded by the EPA, it has not been subjected to the Agency's
required peer and policy review and therefore does not necessarily  reflect the views of the Agency.
   This report was technically reviewed by Dr. Robert Smith, Department of Civil Engineering,
University of California at Davis, Dr. Carl Enfield and Dr. William Dunlap of RSKERL, and Sher-
wood Reed of CRREL.
   The contents of this report are not to be used for advertising or promotional purposes. Citation
of brand names does not constitute an official endorsement or approval of the use of such commer-
cial products.
                                         in

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CONTENTS

                                                                                Page
Abstract	    i
Preface	   iii
Summary  	   vi
Introduction 	    1
   Overland flow 	    1
   Occurrence of organics in wastewater	    2
   Properties of organics 	    3
   Microbial degradation of organic chemicals	    4
   Organics removal by land treatment systems	    4
   Objectives 	    5
Experimental methods	    5
   Site description, Hanover 	    5
   Determining average detention times	    7
   Addition of organics to wastewater 	    8
   Field experiment at Davis	    8
   Water sampling at Hanover	    9
   Water analysis 	    9
   Analytical precision	  11
   Soil and plant sampling and analysis	  13
Results	,	  14
   Organics removal at Hanover	  14
   Organics removal at Davis	  17
   Accumulation organics in soils and plants 	  18
Discussion	  19
   Removal from solution	  19
   Effect of temperature on removal rates	  25
   Model validation using data from the Davis site	  26
   Final removal processes	  26
Summary  and conclusions 	  28
Literature cited	  28
Appendix  A, Experimental overland flow data, Hanover 	  31
Appendix  B. Downslope removal characteristics of selected chemicals at CRREL and at
            Davis  	  45
ILLUSTRATIONS

Figure
  1.     CRREL overland flow prototype	   6
  2.     Diagram of CRREL overland flow system	   6
  3.     Example of C curve used to determine detention time  	   7
  4.     Davis, California, overland flow system	   9
  5.     Division of organics studied into classes by type of analysis 	  10
  6.     Rate coefficients vs average water temperature	  16
  7.     Comparison of ranked order of removal rate coefficients at CRREL and Davis  ...  18
  8.     Illustration of the two-film theory	  20
  9.     Removal rate coefficients v&KOVf	  23

                                          iv

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TABLES

Table                                                                             Page
  1.    Occurrence of organic chemicals in household products  	   2
  2.    Application rates of primary wastewater and average detention times of waste-
        water on the slopes 	   6
  3.    Quantities of organics used to prepare stock solution 	   8
  4.    Volatile organics studied using purge and trap GC/MS/SIM 	  10
  5.    Neutrals analyzed by GC-ECD on 0V-17 and their retention times 	  11
  6.    Precision of neutral, less volatile organics analysis	  12
  7.    Precision of volatiles analysis	  12
  8.    Precision of phenols analysis	  12
  9.    Summary of water analyses for applied wastewater	  14
 10.    Summary of average runoff concentrations for each substance following overland
        flow treatment	  15
 11.    Water volumes applied to overland flow and volume of runoff	  15
 12.    Summary of average removals for each substance by overland flow	  15
 13.    Summary of experimental rate coefficients 	  17
 14.    Results of water analyses for Davis field experiment	  18
 15.    Concentration of PCB 1242 and pentachlorophenol in soil samples  	  19
 16.    Concentration of PCB in plant samples	  19
 17.    Physical properties and experimental removal rate coefficients at 20C for the
        organic chemicals studied	  22
 18.    Experimental and predicted values for the removal rate coefficient k on CRREL
        system using eq 16	  24
 19.    Comparison of experimental removal rate coefficients at 20 and 2.5C	  25
 20.    Experimental versus predicted removal rate coefficients for the Davis site 	  26

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 SUMMARY

    Overland flow is one of the three modes of wastewater land treatment.  In this mode, waste-
 water is applied to the top of a gently sloping, grassy terrace, flows downslope over the surface in
 a thin sheet, and is renovated by physical, biological and chemical processes. The remaining run-
 off is collected at the base of the slope for discharge. While much is now known about the per-
 formance of this type of treatment system for removing nitrogen, phosphorus, solids, oxygen de-
 mand and bacteria, little information has been reported on its ability to remove trace levels of
 toxic organics.
    This study was conducted on an outdoor, prototype overland flow system in Hanover, New
 Hampshire. The overland flow system is 30.5 m long by 8.8 m wide and is divided into three  test
 sections.  During construction the  site was graded to a 5% slope, and a rubber liner was emplaced
 and covered with 15 cm of silt loam soil. The soil was compacted and seeded with a mixture  of
 grasses.
    For this study, municipal wastewater was given primary treatment, spiked with a number of
 organic substances, and applied to two test sections, four days per week, seven hours per day  from
 2 June to 11 December 1981. Three application rates were tested, and the detention time of
 wastewater on the slope was determined for each rate using the centroid of the C curve obtained
 using a sodium chloride tracer.
    About once a week, samples of the applied wastewater, runoff and surface water from a num-
 ber of downslope locations were analyzed for up to 13 organics. Analysis of the most volatile
 components was conducted by purge and trap followed by gas chromatography mass spectrom-
 etry using selective ion  monitoring. Analysis of the less volatile components was obtained by
 sequential extraction from solution using the microextraction method. First the neutrals were
 extracted using hexane  after the pH was adjusted to  12.  The water was then adjusted to pH 2,
 and the phenols were extracted using a second aliquot of hexane. The hexane extracts were an-
 alyzed using electron capture gas chromatography and high-performance liquid chromatography.
   The analytical precision was estimated periodically. For the volatiles the relative precision
 was about 15%.  For most of the  less volatile neutrals and phenols, we estimate the precision at
 10% and 15%, respectively.
   Soil and plant samples  were collected several times during the study and extracted with hexane-
 acetone. The extracts were analyzed in a similar manner to the water solutions.
   The mean concentrations of these 13 organics in the applied wastewater ranged from 11 to
 113 /ng/L with an average  of about 50 ;Ug/L. At a hydraulic loading rate of 0.4 cm/hi (0.12
 m3/hrm of width) in the  summer, greater than 94% removal was found for all of the substances
 tested. At higher application rates, runoff concentrations increased and percent removals declined.
 Later, when the 0.4-cm/hr rate was reestablished in the fall, percent removals did not approach
 the values obtained in the summer, indicating that temperature affects the removal process.
   The rate of removal was found to follow first-order kinetics, and the removal rate coefficients
were obtained from plots  of In C/C0 vs residence time, where C0 and Care concentrations  at zero

                                          vi

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time and other times, respectively. Removal rate constants varied somewhat from day to day, but
the ranked order of the removal rate coefficients for different substances was rather consistent.
Substances with the highest rate coefficients seemed to have a high octanol-water partition coef-
ficient Kow or a moderate Kow and a high Henry's constant. From this result we conclude that
the two major mechanisms responsible for removing organics from solution were sorption on the
surface soil organic matter and volatilization.
   The removal rate coefficients were determined at average water temperatures ranging from
25.7 to 2.5C. The magnitude of the rate coefficient declined as water temperatures decreased,
probably due to decreased molecular diffusivity as the viscosity of the solution increased.  Since
the number of individual determinations differed for each substance and the distribution of these
determinations varied with water temperature, values of the rate coefficient at 20C were obtained
by linear least-squares techniques for the rate coefficient vs water temperature.
   Assuming that sorption and volatilization were controlling the rate of removal from solution,
we developed a relationship including both processes, using the two-film theory for each interface.
This relationship describes the rate of loss for a specific substance as a function of its molecular
weight M, its Henry's constant H and its octanol-water partition coefficient, the detention time
of water on the slope, the average water temperature and the average depth. The magnitudes
of the four coefficients for this model were obtained by multiple regression of the experimental
rate coefficient at 20C vsM, Hand Kovf for each substance. The resulting equation predicts that
sorption is more dominant than volatilization for removing organics from solution by overland
flow,  even for the most volatile substances tested.
   The effect of temperature on these two removal mechanisms was also assessed. The major
effects of decreased temperature are thought to be a reduction in the molecular diffusivity due to
increased viscosity and a decrease in the Henry's  constant. No information on the dependence  of
Kov/ on temperature is available. An equation is given to predict the removal rates at temperatures
other than 20C.
   The model seems to fit  the experimental data for the CRREL system quite well. The model
was tested by conducting a similar study at the overland flow system in Davis, California. The
ranked order of removal rate coefficients from solution for individual substances was very similar
to that found at CRREL. The rate constants obtained experimentally at Davis were compared
with those predicted from  the model for the water temperature and depth measured on the Davis
system. In general the agreement between experimental and predicted values was good except  for
the most volatile substances.
   The analysis of the plants and soils collected periodically on the CRREL system indicated that
only PCB  and, to a much smaller extent, pentachlorophenol were building up in the soil and were
being taken up into the plants. Thus some additional removal mechanisms, probably microbial
degradation and volatilization, must be  operating once these organics are sorbed on the soil organic
matter.  The fact that substances less volatile than PCB were not found to build up suggests that
the rate of biodegradation  is fast enough so that it doesn't limit treatment efficiency.  In other
words, mass transport to the soil surface, not secondary removal, limits the rate.
                                          Vll

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ASSESSMENT  OF THE  TREATABILITY  OF
TOXIC  ORGANICS BY  OVERLAND FLOW
T.F.  Jenkins,  D.C.  Leggett,  L.V. Parker, J.L. Oliphant,
C.J.  Martel, B.T. Foley and C.J. Diener
INTRODUCTION

   There are three major forms of wastewater treat-
ment by application to the land.  These are rapid
infiltration, slow rate and overland flow (EPA 1981).
The choice of which form of land treatment is best
suited for a given locations is dictated by the soil
characteristics, mainly its permeability. Overland
flow is best suited, but not limited, to areas with
gently sloping terrain having heavy soils of low per-
meability.

Overland flow
   In overland flow, wastewater is applied to the top
of vegetated, gently sloping terrain, flows downslope
in a thin sheet, and is renovated by physical, chem-
ical and biological mechanisms. The runoff is col-
lected at the base of the slope and discharged to a
receiving stream in the same fashion as the effluent
from a conventional wastewater treatment plant.
   Overland flow has been used successfully to treat
municipal wastewater in Melbourne, Australia, since
1930 (McPherson 1979).  Even so, little was known
about the mechanisms governing the removal of
specific pollutants until the 1970s.  Thomas et al.
(1974) found that suspended matter and oxygen-
demanding substances could be removed from raw
wastewater to such a degree that  secondary treat-
ment standards could be met.  The mechanisms re-
sponsible for this reduction were postulated to be
sedimentation, filtration and microbial degradation.
Recently Martel et al. (1980) and Peters et al. (1981)
determined the temperature limits of this process.
   Because of the concern over eutrophication in
surface waters, these studies also investigated the
ability of overland flow systems to remove nitrogen
and phosphorus. Thomas et al. (1974) found that
up to 90% of the applied nitrogen and 50% of the
applied phosphorus could be removed. Hoeppel et
al. (1974) obtained similar results and postulated
that a significant portion of this removal was due to
microbial nitrification and denitrification occurring
in the soil, although they did not consider losses by
volatilization. Jenkins et al. (1978) found that nitro-
gen removal remained high until the soil temperature
was reduced to about 14C. Below this point am-
monia-nitrogen removal was significantly reduced.
Peters et al. (1981) obtained a similar result, but
the magnitude of the  reduction was less because
they used a lower-strength wastewater. Peters et al.
also reported that 9% of the nitrogen removal was
due to volatilization.  Jenkins et al. (1978) also found
that ammonia-nitrogen was much easier to remove
than nitrate.  Since many types of pretreatment result
in some oxidation of ammonia to nitrate, pretreat-
ment should be kept to  a minimum.  The major mech-
anisms for removing nitrogen appear to be plant  up-
take, microbial nitrification and denitrification, im-
mobilization in soil and volatilization of ammonia,
although there is some disagreement about their  rela-
tive importance.
   Overknd flow by itself was not particularly effec-
tive in removing phosphorus.  However, removal
could be increased to about 90% by adding alum
prior to application on the land (Thomas et al. 1976,
Peters et al. 1981). There is some doubt, however,

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whether overland flow should be considered for areas
in which the discharge would affect a phosphorus-
limited stream.
   The ability of overland flow systems to remove
heavy metals has also been studied.  Hoeppel et al.
(1974) found removal efficiencies ranging from 75%
to 95% for six heavy metals on a small-scale, indoor
prototype, with most of the removal occurring in
the first meter of the slope.  Peters et al. (1981)
obtained similar results on a full-scale test system
where four heavy metals were studied; the removal
efficiencies ranged from 85% to 94%. These heavy
metals accumulated over time in the soil biomass
and were taken up in plants, particularly upslope
near the point of application.  While there is some
concern over translocation of these metals in the
food chain, Evans et al. (1979) found that this was
                      not observable, even when cattle were allowed to
                      forage directly on an overland flow slope.
                         These studies have greatly increased our under-
                      standing of the treatability of many types  of pol-
                      lutants by overland flow, but little information has
                      been provided on the ability of overland flow to re-
                      move toxic organics.  In an earlier study (Jenkins
                      et al. 1981) we found that volatile organics were
                      removed effectively by overland flow, with treat-
                      ment efficiencies ranging from 80% to  100%, depend-
                      ing on the application rate.  It was suggested that the
                      mechanism for this removal was volatilization.

                      Occurrence of organics in wastewater
                         The average American uses about  160 L of water
                      per day (Hathaway 1980). This water is used for
                      toilet flushing, bathing, cooking, laundering, washing
                      dishes and cleaning. The wastewater generated from
               Table 1. Occurrence of organic chemicals in household products. (After Hathaway
               1980.)
                   Product
Classes of organics
              Deodorizers
              Disinfectants
              Pesticides
              Laundry products
               and soaps
             Medicinal ointments
             Paints
  Aromatics
  Haloaromatics
  Haloaliphatics
  PAH
  Halophenols

  Haloaromatics
  Halophenols
  Haloaliphatics

  Haloaromatics
  Haloaliphatics
  Halomethanes
  Phthalates

  Aromatics
  Nitroaromatics
  PAH
  Phthalates
  Halophenols

  Aromatics
  PAH
  Haloethers
  Halophenols

  Haloethers
  Halophenols
  Aromatics
  Product      Classes of organics
Medicines
                                                        Preservatives
                                                        Cleaners
                                                        Cosmetics
Electrical
 appliances
Aromatics
Halomethanes
Halophenols
PAH

Aromatics
PAH
Haloaromatics
Haloethers
Halophenols

Aromatics
Haloaromatics
Haloaliphatics
PAH
Halophenols

Haloethers
Aromatics
Phthalates
Nitroaromatics
Halomethanes
Haloaliphatics
PAH

PCBs
             Polishes
 Nitroaromatics
 Phthalates
 Haloaliphatics
 Haloaromatics

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this use contains a number of types of "natural"
organic matter derived from human waste, including
urea, proteins, humic materials, carbohydrates,
tannins, lignins and fatty acids  (Rebhun and Manka
1971). These classes of organics are of little con-
cern from a toxicity standpoint, but as a group
they create a major portion of the oxygen demand
on receiving streams.
   Additionally, in nearly all of these uses, various
synthetic organic chemicals are dissolved and become
associated with the waste stream.  These include a
wide variety of synthetic organics that are compon-
ents of cleaners, cosmetics, deodorizers, disinfect-
ants, pesticides, soaps and detergents, paints, pol-
ishes, preservatives and medicines (Hathaway 1980).
Thus, even wastewater with no industrial component
contains low levels of a number of synthetic organ-
ics, many listed on the EPA Priority Pollutant List
(Budde and  Eichelberger 1979).  Some examples of
the various classes of organics and their  presence in
household products are given in Table 1. Wastewaters
also having a significant industrial component may
periodically contain nearly any of the chemicals on
the EPA Priority Pollutant List. While these sub-
stances will generally be  present at very low concen-
trations, many are difficult to degrade biologically
and are thought to be rather potent carcinogens.  In
addition, the occurrence of these substances in waste-
water can cause problems in some types of conven-
tional treatment because of their toxicity  to micro-
organisms (Anthony and Breimhurst 1981).

Properties of organics
   The organic priority pollutants, unlike  most in-
organic substances, are all  volatile to some degree.
Vapor pressures at 20C range  from as high as 18,600
Pa (139.5 ton) for chloroform to as low as 0.05 Pa
(4xlO~4 torr) for pentachlorophenol. The solubil-
ities of these organics in water  also vary widely but
in general are much lower than the inorganics of
major concern from a treatment standpoint.  Chloro-
form, for example, has a water solubility of about
9300  mg/L at 25C, while phenanthrene's solubility
at this temperature is only 1.29 mg/L. For those
organics with very low solubility, a single  spill could
contaminate the waste stream for long periods as
the substance slowly dissolves.
   The proportion of a volatile substance present in
the vapor phase at equilibrium  with a water solution
is a function of both its vapor pressure and its water
solubility. Numerically this equilibrium value is
often expressed as the Henry's  law constant, which
can be calculated in a variety of units. In  any of
these  forms the higher the value,  the higher the pro-
portion of the substance in the vapor  phase.  For
example, chloroform has a Henry's law constant of
340 Pa m3/mole (3.4x 10~3 atm m3/mole) at 20C,
while pentachlorophenol has a value of 0.21 Pa m3/
mole (2.1xlO~6 atm m3/mole).  This means that at
equilibrium, in solutions of equal concentration, over
1000 times as much chloroform (on a molar basis) as
pentachlorophenol would be present in the vapor
phase. When water solutions of these substances are
exposed to the open atmosphere, as occurs in overland
flow, equilibrium will never be achieved, because of
removal by wind and gas  diffusion.  However, the re-
moval rates of volatile substances from water solutions
can be expressed as functions of the Henry's law con-
stant (Liss and Slater 1974). Thus, in this case, chloro-
form should be volatilized from water solution much
faster than pentachlorophenol.  As a rule the higher
the vapor pressure and the lower the water solubility,
Jhe higher the Henry's law constant and the higher the
removal rate by volatilization.
   Another important property  of organic chemicals
in water solution is their tendency to associate with
organic surfaces such as are  present on suspended
particulates and soil organic matter. At equilibrium
the relative concentration of the specific organic in
water solution compared to that on the organic sur-
face is characterized by a partition coefficient.  This
coefficient differs significantly from one organic chem-
ical to another.   Researchers have found it useful to
simulate this value using octancl as a model for  soil
organic matter (Karickhoff  1981).  Thus, knowing the
octanol-water partition coefficient and the amount of
organic carbon present, one can  compare the relative
sorptive properties of several organic chemicals on
soils and sediments. Numerically octanol-water par-
tition coefficients vary over a wide range and are con-
veniently expressed on a log basis (log Kovf).  Chloro-
form, for example, has a \ogKOVf of 1.96 at about
20C, while phenanthrene has a  log^ow of 4.5. Thus,
for equal concentrations of chloroform and phenan-
threne in water solution at equilibrium, nearly 500
times as much phenanthrene as chloroform would
be sorbed  on  a given amount of  organic surface.
   In overland flow systems, organic chemicals in
solution are exposed to a large amount of organic
surface as  suspended particulates, soil organic matter
and vegetation.   The water flows past these surfaces
rapidly, however, with linear velocities in the range
of 0.1-1 .Ocm/s. Schwarzenbach and Westall (1981)
have used  soil columns to show that equilibrium was
not achieved  between water and soil at linear veloc-
ities of 10~2 cm/s and greater. Thus, in overland
flow, water flows over these surfaces much too fast
for equilibrium to be achieved.  Nevertheless the
relative rate of removal from solution due to sorp-
tion for various organics may be a function of their

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  octanol-water partition coefficient. If this is true,
  phenanthrene should be removed much faster than
  chloroform by this mechanism.

 Microbial degradation of organic chemicals
    Organics vary in their rate of microbial degrada-
 tion.  Some persist in nature and may be stable in-
 definitely, while others are degraded to some extent
 under most environmental conditions. Among the
 most persistent are certain pesticides and PCBs
 (Alexander 1973). While degradation of most organ-
 ics is aerobic, some are degraded both aerobically
 and anerobically (Liu et al. 1981) and others only
 under anaerobic conditions (Bouwer et al. 1981b,
 McCormicket al. 1981). Where degradation occurs
 aerobically and anerobically, the rate is generally
 faster under aerobic  conditions (Delaune et al. 1980,
 Liu et al. 1981). Microorganisms commonly present
 in soils and water are capable of degrading many or-
 ganics and using the  organic compounds as sole
 sources of carbon. However, concentrations of trace
 organic chemicals in wastewater at land treatment
 systems will generally be too low to support micro-
 bial growth. In this instance the microbes may min-
 eralize (Rubin et al.  1982, Subba-Rao et al. 1982)
 or alter (Herbes and  Schwall 1978, Liu et al. 1981,
 McCormick et al. 1981) the chemicals but in such
 small amounts that they derive little benefit.
   Incorporation of a substituent in a  molecule can
 often have dramatic  effects on its potential for and
 its rate of degradation. The type of substituent, the
 placement of the substituent in the molecule, and
 the number of substituents are important. Other
 structural features, such as multiple branching, the
 presence of two methyl groups on a single carbon,
 or the presence of a quaternary carbon near the end
 of an alkyl chain, can be a significant deterrent to
 degradation (Alexander 1973). Polycyclic aromatic
 hydrocarbons with more than three rings appear to
 be very resistant to degradation (Herbes and Schwall
 1978, Sherrill and Sayler 1980).
   While a component  may have the potential for
 degradation, it is the environmental conditions that
 will dictate its rate. The  required types of microor-
 ganisms must be present, as well as sufficient nutri-
 ents to maintain the population. Both the concen-
 tration of organisms (Paris et al.  1981) and the con-
 centration of the compound to be degraded (Rubin
et al. 1982,  Subba-Rao et al. 1982) are critical. The
physical and chemical properties of a compound,
such as solubility, volatility and hydrophobicity,
determine its availability  in solution (Kobayashi and
Rittman 1982).  Compounds with low water solu-
bility degrade at slower rates than more soluble
substances (Alexander  1973, Wilson et al. 1981).
 Temperature is significant since microbial activity
 increases exponentially over the 0-20C range.
    In an overland flow system the water has a rela-
 tively short detention time on the slope, generally
 from a half to two hours (Martel et al. 1982). This
 is probably too short for significant degradation to
 occur in solution.  We studied degradation rates of
 toluene and chloroform in wastewater and found that
 it is slow compared to-the detention times for overland
 flow (Jenkins et al. 1981).  The surface to which the
 water is exposed, however, is largely organic (Peters
 et al. 1981), and significant sorption should occur.
 Once this takes place and the organics are immobil-
 ized on the soil surface, degradation seems much more
 likely. Herbes (1981) found that organic chemicals
 degraded faster in soils and sediment than in water.
 Since wastewater is applied to many systems only
 eight hours per day, even if the soil temporarily be-
 comes anaerobic, the site has sixteen hours to re-
 aerate between applications.  During these periods
 the organics are exposed to a nutrient-rich environ-
 ment with a high level of microbial activity.

 Organics removal by land treatment systems
    Except for our previous study of volatile organics
 (Jenkins et al. 1981) there is almost no information
 on the removal of organic chemicals in overland flow
 systems. We found excellent removal of several chlor-
 inated aliphatics, toluene, benzene and chlorobenzene,
 which we tentatively attributed to volatilization. We
 recognize, however, that the data available do not
 rule out sorption followed by biodegradation. Some
 information is available on organic removal in other
 types of land treatment systems as well as for deep
 well injection.  At the slow rate system in Muskegon,
 Michigan, most of the 60 or so organics detectable
 in the influent were removed  to below detection
 limits in the effluent (Demirjian 1979). Of those
 still detectable, over 75% removal was  observed. At
 a prototype slow rate system in Hanover, New Hamp-
 shire, Jenkins and Palazzo (1981) found  greater than
 98% removal of several volatile organics,  some having
 been applied for as long as seven years. Some of this
 removal was shown to be due to volatilization during
 sprinkler application.
   In some rapid infiltration tests, on the other hand,
 poor removals and small retardation factors were
 observed when organics were applied to soil columns
 containing  a sandy soil with low organic carbon con-
 tent (Wilson et al. 1981).  In this study, large per-
 centages of very volatile substances volatilized from
 the soil columns, but the water was not allowed to
pond on the surface as it does in operating rapid in-
filtration  systems. In another soil column experiment

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with soil from the Flushing Meadows site, Bouwer
et al. (1981 a) found attenuation of some organics
during rapid infiltration and attributed this removal
to biodegradation.  Other substances, such as chlor-
oform, were not attenuated significantly. In a field
experiment at the Phoenix 23rd Ave. site, Tomson
et al. (1981) found 70-100% removals of organics,
depending on the class, using the same wastewater
as Bouwer. The depth of sampling for Tomson's
field study was 18.2 m, however, compared to 2.5
m for Bouwer's column study.
   Organic contaminant movement during high-rate
groundwater recharge was studied by Roberts et al.
(1980). Some compounds, such as naphthalene,
were attenuated, apparently due to biodegradation.
The movement of all substances was retarded to
some extent by sorption.
   The transport of organic chemicals in the sub-
soil has been reviewed by McCarty et al. (1981)
and Schwarzenbach and Westall (1981). The move-
ment of specific chemicals was related to their oc-
tanol-water partition coefficients and the percentage
of soil organic matter, conclusions similar to those
reported earlier by  Lambert et al. (1965).
   In summary these results indicate that in the
absence of biodegradation and to some extent vol-
atilization, little attenuation of organic chemicals
should occur in rapid infiltration systems, although
the movement will  be retarded depending on the
soil organic matter  content and the respective
octanol-water partition coefficients. Whether or
not biodegradation is significant in these systems
seems to depend on the depth to groundwater and
the rate of biodegradation relative to the rate of
movement in the soil.  The rate of biodegradation
seems very hard to  predict; as was stated by Wilson
et al. (1981), "biodegradation studies only indicate
a potential for degradation, which may or may not
be realized in the field at a particular place and time."
   In slow rate systems, on the  other hand, the re-
moval of organics is significantly improved.  Because
the rate of application is much lower and significant
water loss occurs by evapotranspiration, the rate
of movement to groundwater is much slower, allow-
ing more time for degradation.  Volatilization of
the most volatile organics is significant during spray
application and  probably also from the soil surface
during drying periods. Some volatilization has also
been indicated in rapid infiltration systems (Bouwer
et al. 1981, Wilson et al.  1981), but to a smaller ex-
tent than in slow rate systems.

Objectives
   The major objectives of this  research project
were:
   1) To determine the treatability of a number of
toxic organics by overland flow land treatment as a
function of detention time on the slope.
   2) To determine the removal kinetics associated
with each of these substances.
   3) To identify the major removal mechanisms for
the various substances and compare their relative
importance.
   4) To evaluate the effect of temperature on the
treatment efficiency.
   5) To determine if these substances accumulate
in the soil and are incorporated into plant materials
grown on the slope.
   6) To develop a mathematical relationship to pre-
dict the treatability of a wide variety of organic
chemicals as a function of their individual physical
properties.
EXPERIMENTAL METHODS

Site description, Hanover
   The major portion of this study was conducted
on an outdoor prototype overland flow system at
CRRELin Hanover, New Hampshire (Fig. 1).  The
system was constructed in 1975; wastewater has been
applied since the summer of 1976.
   The overland flow prototype is 30.5 m long by
8.8 m wide and is divided into three test sections,
each 1.9 m wide (Fig. 2). During construction the
site was graded to a 5% slope, underlain with a rub-
ber membrane, and covered with about 15 cm of
silt loam soil. The soil was compacted to a bulk
density of 1.4 g/cm3 and seeded with a mixture of
K-31 tall fescue, Pennlate orchardgrass, reed canary-
grass and perrenial ryegrass (Martel et al. 1980).
When this  study was begun in June 1981, the domin-
ant plants  were reed canary grass, quackgrass and
Kentucky  bluegrass, with lesser amounts of tall fescue,
orchardgrass and barnyardgrass (Palazzo 1982).
   Municipal wastewater from a small housing area
was given primary treatment and stored in a concrete,
subsurface storage tank (Jenkins et al. 1981).  While
the wastewater composition varied considerably from
day to day, typical values for total organic carbon (TOC),
biochemical oxygen demand (BOD), total suspended
solids, total nitrogen, pH and specific conductance
were 55 jug/L, 85 mg/L, 110 mg/L, 25 mg/L, 7.2, and
500 jxmhos/cm, respectively. This  primary wastewater
was applied to two overland flow prototypes (sections
A and B) from 2 June-11 December 1981 on  a four
day per week, seven hour per day basis.  Section C
was not used for this experiment. Water not lost by
evapotranspiration was collected at the base of the
slope in galvanized steel tanks, its volume was

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                                Figure 1.  CRREL overland flow prototype.
Runoff
                                   . Diagram of CRREL overland flow system.
              Table 2. Application rates of primary wastewater and average detention times of
              wastewater on the slopes.
                      Dates
 Hydraulic     	Detention time fminj	
loading rate    Using maximum   Using centroid
  (cm/hr)     Slope A  Slope B  Slope A  Slope B
              2 June-4 August              0.40
              5 August-16 October          0.80
              19 October-21 October        1.20
              28 October-11 December      0.40
               50
               35
85
50
30
85
60
46
119
 67
 36
108

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measured by pumping through a water meter, and
it was discharged to the municipal Hanover sewer.
The hydraulic loading rate was varied during the
experiment from 0.40 cm/hi to 1.20 cm/hr (Table
2) (0.12-0.50 m3/hrm of width).

Determining average detention times
   The average detention time of wastewater on the
slope at each application rate was determined at
hydraulic steady state by use of a sodium chloride
tracer. A pulse of tracer was added to the waste-
water as a "slug addition" to the distribution cham-
ber in the constant head weirbox, and the tracer
concentration in the runoff leaving the slope was
measured as a function of time (Martel et al. 1982).
The curve of tracer concentration vs time is known
in a reactor engineering as the C curve (Levenspiel
1972).  An example of this type of curve is shown
in Figure 3.  In a recent report Martel et al. (1982)
introducted the concept of a detention time to
correlate reaction rate data for overland flow sys-
tems. They assumed that the average detention
time of water on the slope was at the maximum of
the C curve. Figure 3 shows that the  C curve is_some-
what asymmetric.  The average detention time t is
at the "center  of gravity" of the area  under the C
curve, and because of the asymmetry, it is somewhat
greater than that of the C curve maximum.
   To measure t accurately, the entire C curve would
be needed and its center of gravity determined. The
C curves obtained for the overland flow slopes had
long tails, so it was impractical to obtain the entire
curve. Also, there was the possibility that tracer
was lost on the slope. This makes it difficult to
determine the area under the C curve properly, espec-
ially under the long, slowly decreasing tail. There-
fore, the following expedient was used to estimate
t more realistically than by using the C curve maxi-
mum.  It was assumed that diffusion and backmixing
on the slope could be modeled as a series of well-
stirred reactors. With this model an equation for the
C curve of the form
                                            0)
           fr(/v-i)
can be obtained (Levenspiel 1972). In this equation,
TV is the number of mixed tanks in series and t is
time.  The term r(/V-l) is the gamma function or
generalized factorial of TV-1.  A nonlinear least-
squares regression analysis was used to adjust the
parameters TV and fin eq 1 to obtain the closest fit
possible to the experimental data. The_best fit for
the data in Figure 3 was obtained with t = 35.5 and
TV= 17.7^ In this case, as well as in all the  others
studied, t is longer than the C curve maximum shown
in Figure 3. The higher the value of TV, the less back-
mixing and diffusion  is taking place on the slope.
Figure 3 shows that while eq 1 does a reasonably
good job of fitting the main part of the experimental
C curve, it does not fit the  tail of the curve well. The
tail is caused by dead spaces on the slope, and a much
more  complex model that takes this into account
would be required to fit the tail data.
   Using this approach we calculated t for each test
section at each application rate (Table 2).  The value
of t calculated from the peak of the C curve is also
                                               40           60
                                                   Time  (min)
                                                                                     100
                       Figure 3.  Example of C curve used to determine detention time.

-------
given for comparison.  The detention times calculated
from both sets of data were always considerably
shorter for section A than for section B. Winter
frost action had caused channeling on slope A, re-
sulting in a short circuit and a shorter detention time.
For this reason, most of the data in this report were
collected on section B.

Addition of organics to wastewater
   A stock solution  of trace organics was prepared
by diluting the quantities of each substance given in
Table 3  to 3 Lwith  1-butanol.  Approximately 20
mL of this solution was added to the wastewater
storage tank each day, and the tank was stirred for
one hour prior to application. The primary waste-
water was spiked with these organics with each ap-
plication, whether samples were collected or not.
Since the storage tank holds approximately 5000 L
of wastewater, the amount of each substance added
brought the  concentration  in the storage tank to the
values shown in Table 3. From 28 October through
the end  of the study, 0.5 mL of nitrobenzene was
also mixed with the  spike solution and added on a
daily basis to the storage tank, resulting in an esti-
mated concentration of 120 Mg/L. This was done to
determine if the poor removal efficiencies during
this period were due to the accumulation of sub-
stances applied since June or to seasonal effects.
   As in an earlier study (Jenkins et al. 1981), tol-
uene was present at  detectable levels on a daily basis
in the primary wastewater used in this study. The
source of toluene in  the waste stream is unknown.
Another substance that was not intentionally added
was also observed in the wastewater, but it was found
to originate from our stock solution. This  substance
was subsequently found to have originated as an im-
purity in the bromoform and was identified as di-
bromochloromethane.

Field experiment at Davis
   To confirm the results from the CRREL experi-
ments, a field study was conducted at the Davis,
California, overland flow system on 10 December
1981. The experiment was run in the test area used
by researchers of the University of California at Davis
to study the performance of the system using primary
wastewater. The air temperature at the time of the
studywasl6C(61F).
   The experiment at Davis was conducted on one
overland flow section measuring 25.6 m wide by 41.5
m long (Fig. 4).  The soil at Davis is Clear Lake clay,
and the  site was graded to a 2% slope. The dominant
plant  species is tall fescue.  The application rate used
for the study was 64.4 L/min, or 0.16 m3/hrm of
width.
   For the Davis experiment the organic stock solu-
tion described earlier was amended with nitrobenzene,
benzene and toluene. Approximately 120 mL of this
stock was  dissolved in one gallon of methanol, and
the resulting solution was pumped into the wastewater
distribution line with a peristaltic pump at a rate of
10 mL/min. Wastewater spiked with these organics
was applied to the system for over two hours before
samples were collected. Wastewater, runoff and sur-
face water samples were then carefully collected in a
manner  similar to that used at the  Hanover site, ex-
cept that the stainless steel tubing was not used.
   The samples were immediately cooled in an ice
chest  and shipped cold to CRREL. The volatiles were
analyzed and the other substances extracted within
                      Table 3.  Quantities of organics used to prepare stock solution.
Substance
Chloroform
Bromoform
Chlorobenzene
m-Nitrotoluene
Naphthalene
Phenanthrene
PCB 1242
2-Chloroethylvinylether
Diethylphthalate
o-Chlorophenol
Pentachlorophenol
2,4 Dinitrophenol
Class
Haloform
Haloform
Haloaromatic
Nitroaromatic
PAH
PAH
PCB
Haloether
Phthalate ester
Halophenol
Halophenol
Nitrophenol
Mass added
(g)
30.0
78.0
75.0
75.5
75.0
75.0
75.0
75.0
75.0
86.0
85.5
78.5
tion in storage tank
(W/L)
40
104
100
101
100
100
100
100
100
115
114
105

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                            Figure 4. Davis, California, overland flow system.
26 hours after the samples were collected; the meth-
ods for doing this will be described later.
   The samples were analyzed for BOD, TOC, total
N and total suspended solids by Dr. Robert Smith
of the University of California at Davis using stan-
dard procedures.

Water sampling at Hanover
   Samples of the applied wastewater, of the runoff
from  the base  of the slope, and from the surface at
various distances downslope were collected once
hydraulic steady state was achieved.  Hydraulic
steady state was defined as the point when the run-
off rate had stabilized, usually within 90 minutes.
   Three types of water samples were collected for
analysis.  The" first was used for analyzing for volatile
organics and was collected from the soil surface by
placing a screw-cap test tube on the slope and allow-
ing it  to fill directly (Jenkins et al. 1981).  The tube
was filled to capacity, with care not to leave a head-
space, and was sealed with a teflon-lined cap. The
second sample was used for extraction and analysis
of the remaining less-volatile organics. This sample
was collected in a 300-mL all-glass BOD bottle by
using  the screw-cap, glass test tubes.  The test tubes
and BOD bottles were carefully cleaned with Baker
Resi-Analyzed acetone before each sample was col-
lected. A third sample was collected occasionally in
a manner similar to the second, but the sample was
stored in a 1-L Nalgene bottle.  This sample was used
to analyze for  BOD, suspended solids, TOC and
nitrogen, and was collected by placing a 0.75-m
length of 0.5-in. o.d. stainless steel tubing on the
soil surface, elevating the downslope end slightly,
and allowing the water to completely fill the Nalgene
bottle.
   Water temperature, air temperature and prevailing
weather conditions were recorded each time samples
were collected. The average water depths at each
sampling location were estimated by measuring and
averaging the depths at three random points on the
cross section.

Water analysis
   The toxic organics were divided into four groups
for analytical purposes (Fig. 5).  These are the vola-
tiles, the neutral electron-capturing substances, the
neutral noncapturing substances and the electron-
capturing phenols.  The volatiles were analyzed using
a Hewlett-Packard 5992 gas chromatograph-mass
spectrometer (GS/MS) equipped with an HP 7675A
purge-and-trap sampler (Jenkins et al. 1981). A 60-
mL sample was purged with helium at 20 mL/min
for 20 minutes at room temperature. The eluted
volatiles were collected on  a Tenax tube trap. This
tube was subsequently heated to 200C for five min-
utes and the desorbed compounds directed onto a
Porapak Q column maintained at 90C. The column
was then programmed from 90 to 210C at 6/min
with a helium carrier flow  of 10 mL/min.  Substances
eluting from the GC column were analyzed using
selective ion monitoring (SIM) mass spectroscopy.
The substances analyzed in this manner, their reten-
tion times, and the ions used for each substance are

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                          Test Tube
                              C/MS/SIM
                            Chloroform
                            Toluene
                            Chlorobenzene
                            Bromoform
Hexane
                               GC-ECD
                         Dibromochloromethane
                         Bromoform
                         M-Nitrotoluene
                         Nitrobenzene
                         Diethylphthalate
                         RGB 1242
                        Figure 5. Division oforganics studied into classes by type of
                        analysis.
                          Table 4. Volatile organics studied using purge and trap
                          GC/MS/SIM.
                            Volatile organic
     Ion monitored   GC retention time
         (m/e)*	(min)
Chloroform
Benzene
Toluene
Tetrachloroethylene
Chlorobenzene
Bromoform
85
78
91
166
112
173
13.7
15.3
19.3
19.0
21.6
24!0
                          *Mass to charge ratio.
 given in Table 4.  An internal standard of either
 benzene or tetrachloroethylene was added to each
 sample prior to analysis to allow normalization based
 on stripping efficiency and spectrometer perform-
 ance.  Quantitative data were obtained for each sam-
 ple by comparing the results for each substance nor-
 malized to the internal standard with the similar re-
 sult obtained when 1.0 pL of the stock solution was
 added to the 60 mL of well water and analyzed in an
 identical manner.
   The remaining classes of toxic organics were an-
 alyzed by either gas chromatography (GC) or high-
 performance liquid chromatography (HPLC) after
 solvent extraction  by the microextraction technique
 (Rhoades and Nulton 1980).  The extraction pro-
 cedure was as follows.  Each 300-mL BOD bottle
 was emptied into an acetone-rinsed, 500-ml glass
separatory funnel containing 93 g of NaCl (Fisher
Reagent Grade). The funnel was shaken to dissolve
the salt, and the pH was adjusted to 12 with 5N
                NaOH. A 10-ml portion of hexane (Baker Resi-An-
                alyzed Grade) was then added to each BOD bottle,
                the bottles were swirled to rinse the glass walls, and
                the contents were emptied into the separatory funnel.
                A sample of 300 mL of well water was treated in a
                similar manner to serve as an analytical blank.
                Another 300-mL sample of well water, to which
                1.0 juL of the organic stock solution was added, was
                also treated in this manner to serve as the quantita-
                tive analytical standard.
                   The separatory funnels were then shaken on a
                wrist-action shaker for 30 minutes, the phases allowed
                to  separate, and the water phases drained into ace-
                tone-washed, 400-mL breakers. The hexane solution
                and any emulsion present were drained into a 20-mL
                scintillation vial, and the vial was placed  in a freezer
                overnight.
                   The separatory funnels were then rinsed with tap
                water and acetone and drained before returning the
                water solution.  The pH was adjusted to 2 with a
                                                    10

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 5N H2S04 solution, and 5 mL of hexane was added
 to each. The separatory funnels were then shaken
 again for 30 minutes and the phases separated. The
 water was discarded and the hexane solutions saved
 in 20-mL scintillation vials for phenols analysis and
 placed in a freezer overnight.
   Emulsions in the hexane phases the following
 morning were broken  by forcing the solution through
 acetone-washed glass wool packed in a disposable
 Pasteur pipette. The resulting hexane solution was
 dried by adding a small amount of anhydrous sodium
 sulfate and was saved  for analysis.
   The first hexane extract corresponds to the neu-
 tral fraction and was analyzed in  two separate runs.
 The first analysis was  conducted by GC-ECD on a
 Perkin Elmer Sigma 2 or Sigma 3 gas chromatograph.
 A 2-jj.L subsample of the dried hexane extract was
 injected onto an 8% OV17 column, the column tem-
 perature programmed from 50 to 250C  at 10/min,
 and the eluted  components analyzed on an electron
 capture detector (BCD). The injector and detector
 temperatures were maintained at 200 and 300C,
 respectively, and the column flow rate was 25 mL/
 min of 5% methane in argon. The substances ana-
 lyzed in this manner and their GC retention times
 under these conditions are given in  Table 5.
   Quantitative results were obtained by measuring
 the peak height associated with each substance.
 Peak heights obtained from the analysis of the blank
 sample  were subtracted on an individual basis. A
 measurable blank was found often for  diethylphtha-
 late and periodically for PCB.  The  peak height for
 each substance in the  standard was used to obtain a
 response factor in units of mm per unit of concen-
 tration to enable the peak heights to be converted
 to concentrations in the water.
Table 5.  Neutrals analyzed by GC-ECD on OV-17
and their retention times.
      Substance
GC retention time (min)
Dibromochloromethane
Bromoform
Nitrobenzene
m-Nitrotoluene
Diethylphthalate
PCB#1*
PCB #2*
PCB #3*
PCB #4*
PCB #5*
          6.6
          8.7
         13.1
         14.7
         19.9
         22.6
         24.1
         25.7
         27.2
         29.3
Five peaks were summed for PCB 1242 analysis.
   The first hexane extract was also analyzed on a
 Perkin Elmer Series 3/LC-65T HPLC for naphthalene
 and phenanthrene by injecting a 50-/uL sample into
 an LC-8 reverse-phase HPLC column (Supelco) eluted
 with 85% methanol and 15% water. The flow rate
 was 2.3 mL/min, and the eluted compounds were
 determined on a UV detector operated at 270 nm.
 The retention times for naphthalene and phenanthrene
 under these conditions were 3.5 and 4.0 minutes, re-
 spectively. The corresponding peak heights for these
 substances were measured for the spiked sample for
 each day's samples, and a response factor was ob-
 tained in units of mm/unit of concentration.  The
 peak heights for  these two substances in each sample,
 minus any contribution from the blank, were con-
 verted to concentration using these response factors.
 The response for 2-chloroethylvinyl ether was too
 small to be determined accurately by either GC-ECD
 or HPLC, so the results  for this substance are not
 available.
   Phenols proved to be the most difficult of the
 various organic fractions to analyze. Initially the
 second hexane extract, corresponding to water ex-
 traction at pH 2, was analyzed by GC-ECD using an
 SP 1240 DA column (Rhoades and Nulton 1980).
 The conditions used for analyses were as follows:
injector temperature, 235C; detector temperature,
 350C; column temperature, 175C; and flow rate,
 20 mL/min of 5% methane in argon. Retention times
 of 2,4-dinitrophenol and pentachlorophenol obtained
in this'way were 4.6 and 7.6 minutes, respectively.
O-chlorophenol could not be analyzed using these
conditions because of its poor response on the BCD.
This technique gave an excellent analysis for penta-
chlorophenol, but the results for 2,4-dinitrophenol
were marginal because of an interfering peak that
could not  be separated sufficiently. For this reason
and to measure o-chlorophenol we  also  tried an HPLC
method for the phenols, but we were unable to sep-
arate o-chlorophenol and dinitrophenol; hence all
data reported were obtained by GC-ECD.
   The analyses of BOD, suspended solids, total ni-
trogen and pH were conducted according to standard
methods and are described in more detail by Jenkins
and Palazzo (1981). The total organic carbon anal-
ysis was performed on an Oceanography International
Corporation 0524 B Total Carbon System according
to the manufacturer's directions. This method is
based on the persulfate oxidation method of Menzel
and Vaccaro (1964).

Analytical precision
   Tests were run approximately once a month to
estimate the analytical precision for each substance
                                                  11

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                                         Table 6.  Precision of neutral, less volatile organics analysis.
Sample Number of Bromoform m-Nitro -toluene Nitrobenzene
Date
used replicates
1 7 Julyf Wastewater 5
1 8 Aug.f Wastewater 4
9 Oct.** Wastewater 4
4 Nov.** V2 slope 5
1 Dec.f Runoff 5
* X is the mean (Mg/L), S
t Replicate sample.
** Split sample.
Date

27 Julyf
25 Aug.f
30 Dec.**
X* S
121.5 4.
24.5 0.
32.7 2.
is th standard deviation G/g/L),
Sample Number of
used replicates
Wastewater
Wastewater
Wastewater
6
6
4
RSD X
S RSD X
60 10.8 18.0
60 4.6 7.6
1 3.4 78.0 0.6 0.8
15 0.6 69.6 3.1 4.5 65.5
3 7.0 35.1 3.2 9.1 54.9
S RSD
3.3 5.1
4.0 7.3
Diethylphthalate
X
75.0
75.0
86.2
38.7
70.0
and RSD is the relative standard deviation (%).
Table 7. Precision of volatiles analysis.
Chloroform Benzene Toluene
X* S RSD
29.0 2.6 9.0
30.0 2.3 7.7
30.0 3.5 11.7
X S RSD
55 4.0 7.2
X S
10.0 1.0
50.0 7.6
50.0 3.6
RSD
9.9
15.2
7.2
S
7.0
6.7
2.1
6.1
1.1
RSD
9.3
8.9
2.4
15.8
1.6
PCB 1242 Naphthalene
X
40.0
40.0
58.0
14.3
8.4
Chlorobenzene
X
72.3
60.0
65.0
S
10.9
8.6
4.1
RSD
14.9
14.3
6.3
S RSD X S RSD
4.2 10.5
3.6 9.0
9.0 15.5 75.7 3.7 4.9
4.2 29.2 6.6 0.47 7.1
0.6 7.1 9.2 1.0 10.8
Bromoform
X S RSD
58.4 10.5 18.0
55.0 10.0 18.4
60.0 4.0 6.6
* X is the mean (/jg/L), S is the standard deviation (jiig/L), and RSD is the relative standard deviation (%).
f Replicate sample.
** Split sample.

                                                   Table 8. Precision of phenols analysis.
Date
17
4
1
Julyf
Nov.**
Dec.f
used replicates
Wastewater
Vi slope
Runoff
5
5
4
X
59.
76,
49,
*
.0
.6
.1
S
4.3
10.4
6.4
RSD
7,
13,
13,
.3
.6
.0
X
8.31
25.9
8.6
S
0.96
7.3
0.73
RSD
11.5
28.1
8.5
                             *  X is the mean (jug/L), S is the standard deviation (jug/L), and RSD is the relative standard
                               deviation (%).
                             f  Replicate sample.
                             **Split sample.

-------
using the three analytical methods. These tests
were conducted on separate days than the analysis
of authentic samples because of the time required
to conduct both the purge-and-trap analysis for
volatiles and the sequential extraction procedure
for the other types of substances.
   Determinations for both "split samples" and
"replicate samples" were obtained for estimating
the precision of the analysis alone vs the precision
also reflecting sample collection and sample vari-
ability over time.  The results obtained are presented
in Tables 6-8.  In general the estimates of precision
obtained from split samples were about the same
as from replicates. Thus most of the imprecision
seems to  be associated with the analytical methods
rather than with sampling.
   For the neutral, less volatile organics (Table 6),
the analytical precision is estimated to be 10%
for all substances except PCS at all concentrations
and phenanthrene at low levels.  The consistent,
relatively large imprecision associated with PCB was
because the response was divided among five sep-
arate, rather small peaks and because of the diffi-
culty in establishing the true baseline on a tempera-
ture-programmed BCD analysis. For low levels of
PCB and  phenanthrene we estimate the  analytical
precision to be 20% and 15%, respectively.
   For the volatiles analysis we estimate the chloro-
form and benzene data to be precise to 10%, tol-
uene and chlorobenzene to 15% and bromoform to
20% (Table 7). The precision for these substances
seems to  be related to the retention time on the
Porapak column and may be a result of peak-broad-
ening effects for the later-eluting substances such
as bromoform.
   Although we had one large value for  pentachlor-
ophenol, we estimate the overall analytical precision
for the two phenols to be about 15% (Table 8).
It is surprising that the precision is nearly as good
as for the less volatile neutrals, because two sequen-
tial extracts are required while only one is required
for the neutrals.

Soil and plant sampling and analysis
   Grass samples from the overland flow prototypes
were collected for organics analysis at the three
normal harvests on 19 June, 4 August and 5 October
1981.  Additional grass samples were taken for
analysis on 23 July and 2 September. The grass
samples were frozen in hexane- and acetone-rinsed,
glass canning jars and stored for later analysis.
   For analysis the grass samples were thawed, air-
dried for several days at room temperature, and
ground to pass through a 20-mesh sieve.  After care-
ful mixing, a 5-g subsample was  removed, placed in
a screw-cap test tube, and extracted by shaking with
25 mL of 50% hexane, 50% acetone solution (Tom-
son et al. 1981) for 30 minutes on a wrist-action
shaker.  The test tubes were then centrifuged at 1000
rpm for 30 minutes, and 10 mL of solution was re-
moved with a 10-mL pipette.  The extracts were
placed in 20-mL scintillation vials and dried with
anhydrous sodium sulfate.
   This extract was analyzed directly for electron-
capturing neutrals by the same GC method described
in the water analysis section.  Then the remaining
extract was placed in a 500-mL separatory funnel,
extracted with 300 mL of distilled water containing
93 g of NaCl, and adjusted to  pH 12 with aqueous
5N NaOH.  A 10-mL portion of hexane was added,
and the separatory funnel was shaken for 30 min-
utes on a wrist-action shaker.  The funnels were then
allowed to stand while the  two phases separated.
The green color due to chlorophyll remained largely
in the organic phase.  The water solution was removed
and the organic phase retained.
   The separatory funnels were washed with tap
water and acetone and drained, and the water phase
was returned.  The pH was adjusted to 2 with 5N
H2S04, 10 mL of hexane was added, and the funnels
were shaken for 30 minutes as before. The funnels
were then allowed to stand while the phases sepa-
rated, and the organic phase was retained for phenols
analysis.  The phenol fraction  was concentrated using
a Kuderna-Danish evaporator and analyzed as de-
scribed in the water analysis section. The plant ex-
tracts were analyzed using standards carefully pre-
pared by dissolving the pure substances in hexane.
   Soil samples from sections  A and B of the over-
land flow prototypes were  collected on 23 July, 2
September and 18 October. Soil samples from sec-
tion C, the untreated section,  were also collected to
be used as an analytical blank. Soil samples were
kept frozen in glass canning jars  until analyzed.
   For analysis the samples were thawed and air-
dried for several days at room temperature.  The
soil was ground with  a mortar and pestle and mixed
carefully. A 5-g subsample of each  soil was placed
in a screw-cap test tube and shaken on a wrist-action
shaker for 30 minutes with 25 mL of a 50% hexane,
50% acetone solution (Tomson et al. 1981). The
test tubes were then placed in a  centrifuge at 1000
rpm for 30 minutes.  A 15-mL portion of the clear
supernatant was carefully removed with a glass pi-
pette, placed in a 20-mL scintillation vial, and dried
with anhydrous sodium sulfate.  A 10-mL portion
of the dried extract was then placed in a Kuderna-
Danish evaporator and the volume reduced to about
1.5 mL.  This concentrated sample was then analyzed
in a manner  similar to that described for the less
volatile organics in the water analysis section.
                                                   13

-------
RESULTS

Organics removal at Hanover
   Results of the analysis of individual water samples
are presented in Appendix A. The maximum, min-
imum and mean values for each organic substance
in the applied wastewater are presented in Table 9.
These data show that the applied concentrations
varied considerably from day to day, probably be-
cause of varying degrees of volatilization and be-
cause of sorption on suspended matter and on the
walls of the storage tank. The extent of these proc-
esses depends on the amount of suspended matter
and the length of time between when the wastewater
was spiked and when it was applied. In addition,
no attempt was made to ensure that the same volume
of wastewater was present in the tank from day to
day, and hence the volume in which these organics
were diluted probably varied significantly.  In gen-
eral, though, the concentrations of these substances
ranged from about 20 to 70 Mg/L. The sum of these
trace organics generally amounted to less than 1
mg/L.
   Three hydraulic loading rates were tested during
this study, 0.4, 0.8 and 1.2 cm/hr. Table 10 presents
the average runoff concentrations for each loading
rate. Two values are presented for the 0.4-cm/hr
rate, one for June-August and the second for Octo-
ber-December. In nearly every case, runoff concen-
trations increased with increasing loading rate. The
most striking example is diethylphthalate, where
the average runoff concentrations were 4.2, 21.5
and 68.3 jug/L at 0.4, 0.8 and 1.2 cm/hr, respectively.
   In overland flow, comparing the changes in con-
centration alone is not sufficient for calculating the
           percent removal because significant water loss occurs
           by evapotranspiration.  Table 11 presents the total
           amount of water applied to section B at each appli-
           cation rate, the total volume of water measured in
           the runoff, and the percent lost by evapotranspira-
           tion. At the 0.4-cm/hr rate, about 54.6% of the
           water was removed by evapotranspiration during the
           summer.  For the 0.8-cm/hr rate, only about 28.6%
           was lost.  The 1.2-cm/hr rate was only studied over
           a period of three  days, and a slight increase in vol-
           ume was noted, mainly a result of nearly 2 cm of
           rain over the period. When the 0.4-cm/hr rate was
           reestablished in the late fall, the water loss was only
           28.4%, because there was less plant transpiration
           and evaporation than during the July-August period.
              The average applied and runoff concentrations
           and volumes were combined, and the mass removals
           were calculated (Table 12). At the 0.4-cm/hr loading
           rate in the summer, more than 94% of the mass was
           removed for each of the organics tested. Even at this
           loading rate, though, consistent differences from sub-
           stance to substance were observed on a daily basis.
           When the hydraulic loading rate was increased, re-
           moval decreased significantly for many of the sub-
           stances, with the worst removal for 2,4-dinitrophenol
           at 1.2 cm/hr.  On the other hand, the removal of
           naphthalene was still greater than 90%, even at the
           highest loading rate tested.
              To determine the rate of removal for each sub-
           stance on a daily basis, samples, collected downslope
           were analyzed and the concentrations plotted as In
           C/C0 vs residence time (Jenkins et al. 1981). The
           residence time of each sample collected downslope
           was estimated from downslope distance. For exam-
           ple, at the 0.4-cm/hr rate the total residence time of
                        Table 9. Summary of water analyses for applied wastewater.
                           Substance
 Applied concentration (jjg/L)
Maximum   Minimum   Mean
                                                                             N
                     Chloroform                  58         17
                     Toluene                      64          2
                     Chlorobenzene               110         23
                     Bromoform                 125         20
                     Dibromochloromethane       17          7
                     m-Nitrotoluene              115         20
                     Diethylphthalate             109         29
                     PCB 1242                    69         19
                     Naphthalene                 148         32
                     Phenanthrene                 89         20
                     Pentachlorophenol            83         13
                     2,4-Dinitrophenol            255         18
                     Nitrobenzene                315         48
33
19
58
68
11
50
63
37
63
45
39
79
113
9
8
9
20
11
20
19
21
14
13
15
13
5
                                                  14

-------
Table 10.  Summary of average runoff concentrations (jug/L) for each substance follow-
ing overland flow treatment.

                                    Average runoff concentration
0.4 cm/hr 0.4 cm/hr
Substance
Chloroform
Toluene
Chlorobenzene
Bromoform
Dibromochloromethane
m-Nitrotoluene
Diethylphthalate
PCB 1242
Naphthalene
Phenanthrene
Pentachlorophenol
2,4-Dinitrophenol
Nitrobenzene
*Less than detectable level.
1 June-4 Aug 28
2.3
0.4
0.4
2.2
-
0.5
4.2
1.4
99
>99
98
>98
>99
96
98
>99
>99
99
94
-
0.4 cm/hr
Oct-11 Dec 5
95
-
97
94
97
86
77
92
99
98
94
79
81
0.8 cm/hr
Aug-16 Oct
96
>99
>99
89
94
87
76
95
97
99
97
92
-
1.2 cm/hr
19-21 Oct
__

-
73
84
57
15
64
92
-
44
9
-
                                      15

-------
water applied to section B was found to be about
119 min from chloride tracer experiments. For a
sample collected at half slope, the residence time is
therefore estimated to be 59.5 min, at quarter slope
it is 29.8 min, and so on. This procedure for esti-
mating residence times for samples collected at var-
ious points on the slope was tested by conducting a
chloride tracer experiment, measuring the chloride
concentration with time in both the runoff and water
collected at half slope, and obtaining the residence
times from the centroid of the C curves as described
earlier.  The values determined for full slope and
half slope were 35.5 and 16.5 min, respectively, in-
dicating that the method used for estimating resi-
dence times is valid.
   When the concentrations for each substance were
plotted in this way (In C/C0 vs residence time), a
relationship, which generally appeared to be linear,
was obtained for all the substances tested in this
study. Examples are shown in Appendix B. When
the best-fit straight lines were obtained by least-squares
techniques, an intercept very near zero was found in
all cases, with correlation coefficients generally ranging
from 0.94 to 0.99. Thus these empirical relationships
can be described by
      In    - = -kt
(2)
where k is the slope of the best-fit straight line and
C0 is the value of the concentration C at t=0; in our
case C0 is the applied concentration.  Equation 2 is
the integrated form of the first-order rate  law
      dC
      - = -kC
      dt
(3)
where k is the first-order rate coefficient (min"1).
                k
              (min"')
                    0.06
                    0.04
                    0.02
                            Diethylphthalote
                            k(20C) = 0.022
                                        I     I      I     I     I      I     I     I     I
                                        8         12         16         20
                                            Average Water Temperature (C)
                                                                                 24     28
                                          a. Diethylphthalate.
                   0.06 
                   004
                k
              (min"1)     _
                   0.02	
                                       8          12          16        20
                                           Average Water Temperature (C)
                      24
                                28
                                           b. m-Nitrotoluene.
                         Figure 6.  Rate coefficients vs average water temperature.

                                                    16

-------
   Experimental values of k were determined in this
way for each substance each day samples were an-
alyzed; the values are presented in Appendix Table
A2 along with the average water temperatures for
that day.  Depending on the substance, between 5
and 21 individual determinations of k were obtained
at average water temperatures ranging from 25.7C
on 9 July to 2.5C on 2 December.  When the ex-
perimental rate coefficients were plotted vs runoff
temperature, the type of relationship shown in Fig-
ure 6 was obtained. In all cases the value of k de-
creased as runoff temperatures declined in the fall
and early winter. Since the number of determina-
tions for each  substance differed as well as the dis-
tribution of these determinations with respect to
runoff temperature, it would not be meaningful
to compare the k values for each substance by sim-
ply averaging all the values obtained. Instead, for
most of the substances, we obtained the best-fit
straight line from the plot of the individual k val-
ues vs average  water temperature and solved these
equations for  the k value at 20C.  These values are
summarized in Table 13 along with the maximum
and minimum values and the number of determin-
ations. For a  few of the volatile substances, such
as chloroform, toluene and chlorobenzene, insuf-
ficient data were available to obtain the k value
for 20C in this way. For these substances the
k (20C) values were estimated by averaging the
experimental  values obtained for the summer
months (June-September).  Values of k (20C)
obtained in this way for other substances such as
m-nitrotoluene and diethylphthalate compared fa-
vorably with values obtained from the best-fit lines
of k vs average temperature.
   The substance with the highest k (20C) value
was phenanthrene, followed by toluene, chloroben-
zene and naphthalane, with removal rate coefficients
ranging from 0.077 to 0.056 min"1. The substances
that were removed the slowest were nitrobenzene,
dinitrophenol and diethylphthalate, with k (20C)
values ranging from 0.018 to 0.022.

Organics removal at Davis
   To determine if the same behavior would be found
on a full-scale system, a field test was conducted at
the Davis, California, overland flow system as de-
scribed in the experimental section. The results of
the water analyses for this test are presented in Table
14. Except for diethylphthalate the removals were
greater than 90% by mass.
   The relationships of In C/CQ vs residence time
for the various samples at Davis were linear for most
of the substances (Appendix Figs. B9 and BIO).
This indicates that the removal processes at Davis are
also governed by first-order kinetics, and the removal
rate coefficients can be obtained from the slope of the
best-fit line. (Only data obtained from samples col-
lected as far downslope as 75  ft were used to calcu-
late rate  coefficients. Samples collected farther down-
slope were obtained before the full detention time
on the slope was achieved.) The order of the rate
coefficients at Davis  (ranked from  fastest to slowest)
is very similar to that at CRREL (Fig. 7).
                           Table 13. Summary of experimental rate coefficients.
                                              First-order rate coefficients (mirT1)
Substance
Chloroform**
Toluene**
Chlorobenzene* *
Bromoform
Dibromochloromethane
m-Nitrotoluene
Diethylphthalate
PCB 1242
Naphthalene
Phenanthrene
Pentachlorophenol
2,4-Dinitrophenol
Nitrobenzene
Maximum
0.047
0.127
0.105
0.045
0.062
0.062
0.031
0.061
0.084
0.131
0.052
0.029
0.019
Minimum
0.017
0.024
0.030
0.017
0.021
0.007
0.006
0.013
0.029
0.027
0.009
0.003
0.003
k(20C)*
0.030
0.070
0.064
0.032
0.053
0.030
0.022
0.035
0.056
0.077
0.036
0.019
0.018
Nf
9
8
9
17
11
20
19
21
15
14
15
12
5
                    * The value of k at 20 C from linear best fit of experimental k values vs
                      average water temperature, except when indicated otherwise.
                    f The number of individual determinations.
                    'The value of k (20 C) was obtained by averaging experimental k values
                      obtained from June-September 1981.
                                                   17

-------
                        Table 14.  Results of water analyses for Davis field experiment.*
Concentration
(ng/L)
Substance
Chloroform
Toluene
Benzene
Chlorobenzene
Bromoform
Dibromochloromethane
m-Nitrotoluene
Diethylphthalate
PCB 1242
Naphthalene
Phenanthrene
Pentachlorophenol
2,4-Dinitrophenol
Nitrobenzene
Applied
51.1
70.7
78.6
88.9
187
24.7
144
107
98.9
179
149
315
238
118
Runoff
1.8
0.7
1.5
0.9
4.8
0.3
8.6
54.2
3.5
2.7
1.2
6.1
15.6
13.3
Mass
(mgl
Applied
592
820
911
1031
2168
286
1669
1240
1146
2075
1727
3654
2761
1368
Runoff
18.8
7.4
15.5
8.7
49.1
2.6
87.9
554.0
35.8
27.2
12.5
61.0
156.0
13.6
Removal
Removal rate coefficient
(% by mass) (min'1 )
96.8
99.1
98.3
99.2
97.7
99.1
94.7
55.3
96.9
98.7
99.3
98.3
94.6
90.1
0.012
0.018
0.015
0.018
0.017
0.018
0.011
0.003
0.020
0.020
0.031
0.013
0.009
0.008
          The data from the Davis system were obtained only once (10 December 1981), so it is not possible to
          assess the statistical significance of the rate coefficient data.
  14
  12
  10
S  8
                             J	L
                 4     6      8     10
                  Removal Order (CRREL)
                                           12
                                                 14
  Figure 7. Comparison of ranked order of removal
  rate coefficients at CRREL and Davis.
    At Davis we added benzene in addition to the
  substances tested at CRREL. The results indicated
  its rate of removal was lower than toluene, dibro-
  mochloromethane and naphthalene and very similar
  to that of pentachlorophenol.

  Accumulation of organics in soils and plants
    As described earlier, soil samples collected from
the Hanover site were analyzed for organics as well.
Of those added, only PCB 1242 consistently accumu-
lated in the soil at levels above the background. In
a few instances pentachlorophenol (PCP) was also
detected above background levels. All of the other
substances were present at concentrations below a
detection limit of about 0.2 //g/g.  The results for
PCB and PCP are presented in Table 15.
   The soil from sections A and B had detectable
levels of PCB in all cases, with values ranging from
0.37 to 4.87 jug/g.  While there is little consistency
from location to location, there is a clear tendency
toward larger accumulations with time. Of the sam-
ples collected on or before 2 September, no values
over 1.21 ^g/g were found.  For the  samples collected
on 12 October, a number of samples had values greater
than 3  ;ug/g. Soil samples from section C (the control
area), on the other hand, showed no detectable PCB.
No application of wastewater  containing these organ-
ics was made to section C, so these analyses serve as
an analytical blank.
   Samples of plant tissue from the two treatment
sections (A and B) and the control section (C) were
analyzed to determine to what extent these sub-
stances had accumulated. Only PCB was found at
measurable concentrations, although analytical dif-
ficulties prevented measurement for dinitrophenol
and pentachlorophenol.  For the treatment areas,
concentrations of PCB ranged from <0.04 to 0.85
^g/g on an air-dried plant material basis (Table 16).
                                                    18

-------
                          Table 15. Concentration of PCB 1242 and pentachloro-
                          phenol (PCP) in soil samples.

                                                            Concentration (ng/g)
Sample
Slope B (upper)
Slope B (lower)
Slope A (lower)
Slope C (upper)
Slope C (lower)
Slope B (lower)
Slope A (upper)
Slope B( 1/8 slope)
Slope B( 1/4 slope)
Slope B (1/2 slope)
Slope B (3/4 slope)
Slope A (1/8 slope)
Slope A (1/4 slope)
Slope A (1/2 slope)
Slope A (3/4 slope)
Slope C
Date collected
23 July 81
23 July 8 1
23 July 81
23 July 81
23 July 81
2 Sept 81
2 Sept 8 1
12Oct81
12Oct81
12Oct81
12Oct 81
12Oct81
12Oct81
12Oct81
12Oct81
12Oct 81
PCB
0.37
1.19
0.54

-------
                                                Bulk Gas Phase
                                              (completely mixed)
                               Gas Film
                                                                  Gas/Liquid Interface
                                                     Liquid Film
                                              Bulk Liquid Phase
                                              (completely mixed)
                                Figure 8.  Illustration of the two-film theory.
   Two theoretical approaches have been taken in
 dealing with the transfer of volatile substances
 across the air/water interface (volatilization). These
 are the two-film theory developed by Whitman
 (1923) and the penetration theory. Of these the
 two-film theory has received the greatest attention
 and has been the most successful in matching exper-
 imental results on transfer of gases across the air/
 water interface (Billing 1977, Smith et al. 1981,
 Rathbun and Tai 1981). In this theory, two ficti-
 tious films are assumed to exist at the gas/liquid in-
 terface, one gas and the other  liquid (Fig. 8). These
 films are assumed to be stagnant and to exert all the
 resistance to transfer across the interface.  The bulk
 phases above and below these  films are assumed to
 be well mixed. Equilibrium is assumed to exist at
 the interface, and diffusion across the liquid and
 gas films controls the rate of mass transport.
   Since all the resistance to transfer is assumed to
 occur in the films, the total resistance Rj. is the sum
 of the resistances of the liquid and gas phases:
                                             (4)
where RL is the resistance across the liquid film and
RG is the resistance across the gas film.  Calculating
the total mass transfer thus requires summing the two
individual resistances, which can be considered to be
reciprocals of their conductivities (Mackay et al.
1979):

                             K
                             A
                                             (5)
where KL and KG are the conductivity terms and
are the liquid-phase and gas-phase transfer coeffic-
ients, respectively. Thus the total resistance Kj to
mass transfer can be expressed as
                                             (6)
Using Liss and Slater's (1974) values for air/sea ex-
change of C02 and H2O vapor and assuming that in-
dividual phase transport coefficients are proportional
to the reciprocal of the square root of the molecular
weight (A/-1/2), Billing (1977) developed a relation-
ship for the total mass transfer coefficient for vol-
atilization (^vol) in units of cm/min:
                      221.1
              1.042
                H
+ lOO.OJM1/2
                                             (7)
where H is the Henry's law constant (in dimensionless
units). The half-lives for a series of volatile chloro-
carbons in solution calculated with this equation
matched experimental values obtained in a laboratory
test quite  well (Dilling 1977). But, as pointed out
by Billing, the match was rather fortuitous since the
transport  coefficients are a function of turbulence in
both air and water phases, which were simulated only
by mechanical stirring in the lab but are produced
by wind and wave action in the ocean.
   Experimentally determined half-lives were com-
pared with those obtained using eq 7 for a number
of volatile substances on the CRREL overland flow
slope (Jenkins et al. 1981). The results did not match
the calculated values but were longer by a factor of
about 2-3 for most substances tested.  This was ex-
plained by incomplete mixing, since the Reynolds
numbers for this system ranged from 100 to 400,
indicating relatively nonturbulent conditions.
   Since all of the substances tested in the previous
study were quite volatile (as measured by their Henry's
constants), the removal rates  of much less volatile
substances were unknown. Experimental results
                                                    20

-------
from the current study for much less volatile sub-
stances such as phenanthrene, PCB and pentachloro-
phenol indicate removal rate coefficients very sim-
ilar to those for some of the most volatile substances
such as toluene, chloroform and chlorobenzene.
Since the Henry's constant for these less volatile
substances are one to three  orders of magnitude
lower, their removal is not predictable using the
volatilization model alone.
   Studies conducted on other types of land treat-
ment systems, particularly rapid infiltration, show
that the movement of organics through soils is re-
tarded by sorption on soil organic matter (Wilson
et al. 1981).  In rapid infiltration the transport of
these substances through the soil has been found to
be predictable, assuming that equilibrium is achieved
with the soil organic  matter. In rapid infiltration
the downward velocity of water will generally be
less than 10~3 cm/s,  a value at which Schwarzen-
bach and Westall (1981) found excellent agreement
between partition coefficients  obtained from col-
umn studies and batch experiments. At velocities
above 10~2 cm/s, however,  Schwarzenbach found
that transport became affected by slow sorption
kinetics. For overland flow the average velocity of
water across the surface and in contact with soil
organic matter is on the order of 0.1-1.0 cm/s,
which is 10-100 times greater than the cutoff point
for equilibrium given by Schwarzenbach.  Thus the
movement is much too fast for equilibrium to be
established.
   The amount of organic matter at  the surface of
an overland flow system, however, is probably much
greater than for the other types of land treatment.
Peters et al. (1981) found the surface layer of soil
at their site had a Kjeldahl-N concentration as high
as 20,000 /ig/g after three years of operation. If
this is mainly organic-N and there is  a ratio of about
20 between organic-C and organic-N, the organic
carbon content is about 20%.  This large accumula-
tion of organic matter on the surface is consistent
with visual evidence from the CRREL system and
other systems that have been in operation for at
least several months and may be similar in character
to the organic slime that develops on an operational
trickling filter. Thus, while  the time for sorption is
rather short compared to other systems, the surface
encountered by the solution in an overland flow
system is largely organic in nature.
   The substances studied on the CRREL system
were ordered according to the magnitude of their
experimental first-order rate coefficients k (20C)exp
and tabulated along with literature values for the
molecular weight M,  the octanol-water partition
coefficient Kow and  the Henry's constant H (Table
17). Table 17 shows that, in general, substances
having low removal rate coefficients had relatively
low values of both KQW and//, while substances
with larger rate coefficients had either a high Kovf,
or a moderate KOVJ and a high H.  When the removal
rate coefficients are plotted as a function of log Kow
(Fig. 9), a good linear relationship is obtained for
many of the substances tested. Compared to this re-
lationship, the experimental rate coefficients for
toluene and chlorobenzene, and to a lesser extent
chloroform, are too high. This result is consistent
with additional removal by volatilization for these
substances. The experimental rate coefficients for
PCB and PCP, on the other hand, are too low, a re-
sult expected because these two substances were
found to accumulate on the soil, and resolubilization
should be  possible. This implies that the rate of re-
moval may be predictable using these two mechan-
isms:  sorption on organic surfaces and volatilization.
The overall removal rate coefficient kT  could there-
fore be expressed as the sum of two components:
                                            (8)
where ksolb and kvol are the rate coefficients for
volatilization and sorption, respectively.  The rate co-
efficient k is related to the transfer coefficient K^. by
                K
                  vol
K.
                          sorb
                                            (9)
where d is the solution depth in cm and Kvol and
^sorb are the transfer coefficients for volatilization
and sorption, respectively. In the CRREL experi-
ment the average solution depth on the slope was
about 1.2 cm.
   We attempted to model the loss rate observed ex-
perimentally versus that predicted using volatilization
and sorption. To do this we assumed that the total
removal rate coefficient was the sum of the volatili-
zation and sorption terms, as described in eq 8.
Solving for the volatilization portion by combining
eq 7 and 9, we have
             1
 221.1
      vvol
                 1.042
                   H
     .0),
                                            (10)
+ 100.0 Af1/2
Rearranging this equation we have

             1          2.21 \H
                 (0.01042+/OM1/2
                                            (H)
Since the values of the constants 2.211 and 0.01042
are only appropriate for the well-stirred condition
at the air/sea interface and the experimental system
                                                   21

-------
             Table 17.  Physical properties and experimental removal rate coefficients at 20C for the organic chemicals studied.
                                                                                              H
Substance
Phenanthrene
Toluene
Chlorobenzene
Naphthalene
Bibromochloromethane
Pentachlorophenol
PCB 1242
m-Nitrotoluene
Bromoform
Chloroform
2,4-Binitrophenol
Biethylphthalate
Nitrobenzene
Benzene
* At 25C.
M
178 2
92
113
128 2
208
266 1
261t 3
137
253
119
184
222
123
78

Value
.88X104
490
692
.34X103
t
.32X105
.8xl05
282
189ft
93.3
34.7
162*
70.8
135

f We were unable to locate values for H and K"ow for
$ Average M assuming an
** Calculated from H= 16
ft Calculated from In fcow
average chlorine content of
.04 P-M/T-S.
= 7.494_in s

Source Value
Hansch and Leo 1979
Hansch and Leo 1979
Hansch and Leo 1979
Hansch and Leo 1979

Hansch and Leo 1979
Veithetal. 1979
Hansch and Leo 1979
Mackay etal. 1980
Hansch and Leo 1979
Hansch and Leo 1979
McBuffie 1981
Hansch and Leo 1979
Hansch and Leo 1979

this substance.
3.2 (Safe and Hutzinger 1973).

(10s atmos-m3/mole}
3.93*
515
267
36
t
0.21
30*
5.3**
63
314
0.001 it
0.056**
1.9**
435




Source
Mackay etal. 1979
Leighton and Calo 1981
Leighton and Calo 1981
McCarty 1980

McCarty 1980
Westcott et al. 1981
Billing 1977
McCarty 1980
Leighton and Calo 1981
Billing 1977
Billing 1977
Billing 1977
Leighton and Calo 1981




K(^L/ Javrt
C^ y
0.077
0.070
0.064
0.056
0.053
0.036
0.035
0.030
0.032
0.030
0.019
0.022
0.018
***




(mole/m3); Mackay et al. (1980) Chemosphere, 9: 701.
it  Estimated fromW= 16.04 P-M/T-S using S of 2,4-dinitrophenol andP of 2,4-dinitrotoluene.
*** Not studied on the CRREL system during this period.

-------
                      0.080
                      0060
                   k
                (20C)
                      0.040
                      0.020
                                                                             () Volatiles
                                                                             (o) Others
                                                                             (A) PCB.PCP

                                                                               I	
                                                       Log Kow
                               Figure 9. Removal rate coefficients {20C) vs Kn
 used by Billing (1977), the equation was generalized
 as:
if   -  _JL
 vo1   d
                         H
                                            (12)
where Bl  and B2 are coefficients specific to an over-
land flow system.
   From a kinetic point of view, sorption is analo-
gous to volatilization in that interphase transport
occurs across a water/soil interface.  The same types
of assumptions can be made about transport across
this interface as were made for the two-film theory
for transfer across the air/water interface. That is,
two stagnant films can be assumed to be present on
either side of the interface, with the resistance to
sorption being the sum of the individual resistances
of the separate  films. Again  equilibrium is assumed
to be present only right at the interface, and trans-
port across the  interface is controlled by diffusive
properties. The equilibrium  at the interface can be
assumed to be proportional to the octanol-water
partition coefficient^ow, since this constant has
been shown to be proportional to  the actual parti-
tion coefficient for water and soil  organic matter
(Karickhoff et al. 1979). For all these substances
except PCB and PCP, soil analysis  indicated that the
substances were not accumulating with time.  Thus,
for these substances the  back reaction, desorption,
should not be important and the kinetic approach
should be  valid.
   If we assume that the sorption  term has a form
similar to  the volatilization term, then
                                                                 orb
                                                                                               (13)
                                                          By combining eqs 8, 12 and 13 we can express the
                                                          total rate coefficient as
                                                                          H
                                                                                               (14)
                                                    Using a value of 1.2 cm for d and the values for M,
                                                    //, Kov/ and /c(20C)exp  from Table 17 for each sub-
                                                    stance, we subjected eq 14 to a multiple regression
                                                    analysis to determine the best values for the coeffi-
                                                    cients Bl,B2,B3 and54. When this was done, using
                                                    nine of the substances in Table 17, the following
                                                    equation was obtained:
                                                         JtT(20) =
                                                                   10.2563
H
                                                                              (5.86xlO-4+#)
                                                                 0.7309
                                                                                             I.   (15)
                                                   The residual root mean square for lack of fit was
                                                   3.3xlO-3
                                                      The total predicted values for &(20C) and the
                                                   volatilization and sorption components, as well as
                                                   the experimental values for A:(20C), are  given in
                                                   23

-------
                   Table 18.  Experimental and predicted values for the removal rate coefficient
                   k on CRREL system using eq 16.
k(20 Cj*
Substance
Phenanthrene
Toluene**
Chlorobenzene**
Naphthalene
Dibromochloromethane
Pentachloro phenol
PCB 1242
m-Nitrotoluene
Bromoform
Chloroform**
2,4-Dinitrophenol
Diethylphthalate
Nitrobenzene
Experimental
0.077
0.070
0.064
0.056
0.053
0.036
0.035
0.030
0.032
0.030
0.019
0.022
0.018

Total
0.046
0.067
0.062
0.057
tt
0.037
0.042
0.034
0.027
0.036
0.008
0.020
0.017
Predictedf
Volatilization
0.001
0.020
0.016
0.007
tt
<0.001
0.004
0.002
0.007
0.016
< 0.001
< 0.001
<0.001

Sorption
0.045
0.047
0.046
0.050
tt
0.037
0.038
0.032
0.020
0.020
0.008
0.020
0.016
                  *Values obtained from best fit line or plot of individual experimental k values for various
                  average water temperatures.
                  (Predictions from eq 15 and values in Table  17.
                  "Experimental values for these substances were obtained by averaging fe values obtained
                   from June-September.
                  ftData not available for prediction.
 Table 18. The four substances not used to obtain
 the coefficients for this model were PCB, dibromo-
 chloromethane, phenanthrene and dinitrophenol.
 Dibromochloromethane could not be used since we
 did not find values of H andKOVf in the literature.
 The experimental value for PCB was not used since
 it was found to accumulate in fairly large amounts
 on the soil with time, so the back reaction (desorp-
 tion) may be reducing the rate coefficient measured.
 The values of phenanthrene and dinitrophenol were
 used initially, but most  of the residual sums of squares
 due to lack of fit in the  original tests were for these
 substances.  For phenanthrene the predicted value
 was much lower than measured, possibly because an
 additional mechanism was operating for this substance.
 For example, Mill et al.  (1981) found that some poly-
 nuclear aromatics undergo rapid photolysis in water.
 This additional mechanism could account for the
 larger-than-predicted experimental rate coefficient
 for this substance. Dinitrophenol was also found to
 be removed much faster than predicted. This sub-
 stance, however, is a fairly strong acid with a pKa of
4.09. Thus, in neutral solution, it will exist predom-
inantly in the dissociated form. Removal of this type
of substance is not considered in this simple model,
and hence it was not used to obtain the coefficients
for eq 15.
   In general the fit is excellent for most of the sub-
stances (Table 18). The low experimental values ob-
tained for PCB may be a result of accumulation on
the soil organic matter.  The low experimental value
for chloroform may be due to some additional pro-
duction of chloroform on the slope, from reaction of
residual chlorine or hypochlorite with organic matter,
or from degradation of larger chlorinated organics on
the slope. When the total predicted value from eq 15
is divided into its two components, sorption and vol-
atilization, sorption predominates, even for the most
volatile substances (Table  18). For toluene, the sub-
stance with the highest Henry's constant tested, 70%
of the total predicted removal from solution is due
to sorption and only 30%  due to volatilization.
Equation 15 predicts that  chloroform has the high-
est percentage of its total removal rate due to vol-
atilization (44%) of all of the substances tested.
These results are contrary  to the conclusion postu-
lated in an earlier experiment where only very vola-
tile substances were studied (Jenkins et al. 1981).
However, the values in Table 18 refer only to direct
loss from the moving solution. Subsequent volatiliza-
tion of substances originally sorbed probably  removes
a significant amount of very volatile substances such
as toluene and chloroform.
                                                    24

-------
   From eq 15 volatilization also accounts for greater
than 9% of the predicted removal rate for chloroben-
zene, bromoform, naphthalene and PCB.  Direct
volatilization from solution is predicted to be insig-
nificant for the remaining substances, which all have
//values less than 10~5 atmos-m3/mole.
   Equation 15 also predicts a higher rate of sorp-
tion for naphthalene than for pentachlorophenol
(PCP), even though the Kow for PCP is over 50 times
greater. This is due to naphthalene's much lower
molecular weight, which increases its molecular dif-
fusivity relative to PCP. In fact, naphthalene had a
significantly higher experimental fc(20C) value than
PCP (Table 18).

Effect of temperature on removal rates
   The model developed in the previous section (eq
15) described the rate of removal of an organic sub-
stance from solution as a function of the Henry's
law constant, the octanol-water partition coefficient
and the molecular weight. Changes in water temper-
ature can be expected to affect this removal rate in
several ways. The value of// strongly depends on
temperature, as illustrated by toluene, which has an
//of 5.15x 10~3  atmos-m3/mole at 20C but only
2.02x 10-3 atmos-m3/mole at 0C (Leighton and
Calo 1981).  Thus the magnitude of volatilization is
expected to decrease  as temperature declines.
   Information on the magnitude of Kow as a func-
tion of temperature is generally not available for
these substances. Some preliminary information
gathered in this laboratory indicates that Kov/ may
increase by as much as 50% in going from 20 to 0C.
This is a further indication that mass transport and/
or biodegradation, rather than equilibrium, controls
the removal rates, since rates decreased with temper-
ature.
   Both the volatilization and sorption terms were
developed using the two-film theory of interphase
transport. From Pick's Law, diffusion is proportion-
al to molecular diffusivity D. The effect of temper-
ature on values of diffusivity can be estimated from
eq !6(Thibodeaux 1979):
     D@T,=D@T
fc
l\Tl
(16)
where T't and T2 are the various temperatures (/T)
and jUj and ;U2 are the values of viscosity of water
as these temperatures. If we assume some value for
diffusivity at 20C, we can calculate the diffusivity
at 2.5C using eq 16 and thereby determine the
relative  change in the magnitude of diffusion one
would expect. From this effect alone, the removal
rate constant at 2.5C should be only about 57%
ofthatat20C.
   Experimental removal rate coefficients were ob-
tained at an average water temperature of 2.5C on
2 December; these values and the fc(20C) values
are presented in Table 19.  Values of k(2.5) were
lower than  fc(20C) values for all substances tested,
with the ratio of /t(2.50)/fc(20) for chloroform,
toluene  and chlorobenzene were 0.70, 0.31 and
0.47, respectively. The mean value of these three
substances is 0.49, a value comparable to that for
the less  volatile substances.  Based on these results,
eq 15 can be modified to predict removal rates  at
temperatures other than 20C:
              /r2-i.ooi9\
              \ 293  M2  /
                                           (17)
                       Table 19. Comparison of experimental removal rate coefficients
                       at 20 and 2.5C.
                                                    Rate coefficients (min'1)
Substance
Phenanthrene
Toluene
Chlorobenzene
Naphthalene
Dibromochloromethane
Pentachlorophenol
m-Nitrotoluene
PCB 1242
Bromoform
Chloroform
2,4-Dinitrophenol
Diethylphthalate
Nitrobenzene
k(20C)
0.077
0.070
0.064
0.056
0.053
0.036
0.030
0.035
0.032
0.030
0.019
0.022
0.018
k(2.5C)
0.027
0.022
0.030
0.029
0.021
0.027
0.012
0.013
0.016
0.021
0.010
0.006
0.007
k{2.5)/k(20)
0.35
0.31
0.47
0.52
0.40
0.75
0.39
0.37
0.50
0.70
0.53
0.27
0.39
                                                  25

-------
where T2, /u2 and H2 are the runoff temperature
(K), viscosity at T2, and Henry's law constant at
r2, respectively, and 293 and 1.0019 are the temper-
ature and viscosity of water at 20C.

Model validation using data from the Davis site
   To test the relationships developed on the CRREL
system, an experiment was conducted at the Davis,
California, overland flow site on 10 December 1981.
The average  water depth on the Davis site was esti-
mated at 2.3 cm by making a number of measure-
ments at various locations.  The average water tem-
perature was 16.5C on the day of the study, and the
average  detention time was estimated to be 240 min-
utes. The detention time was harder to  determine
than at  the CRREL site because  of a much longer
detention time and higher background chloride  con-
centrations.
   The predicted removal rate coefficients for the
13 substances studied at CRREL plus benzene are
given in Table 20, along with experimental values.
The values were predicted using eq 17 for a total
slope detention time  of 240 minutes and an estimated
water depth of 2.3 cm.  The viscosity of water at
16.5C was estimated to be 1.095 N-s/m, and the
Henry's law  constants for toluene, benzene, chloro-
benzene and chloroform were estimated at 4.42x 10~3,
3.71xlO-3,  2.32xlO-3 and2.66x!Q-3 atmos-m/
mole, respectively, using the best-fit relationships
developed by Leighton and Calo (1981). Values of
H for the other substances  were estimated to be 75%
of their values at 20C. Values of KOVi were assumed
to be the same at 16.5C as for 20C.
   The experimental rate coefficients are quite sim-
ilar to those predicted using eq 17 and the coeffic-
ients for B1,B2, B3 and 54 obtained on the CRREL
system. As found at CRREL, the experimental
values for phenanthrene, bromoform and 2,4-dini-
trophenol are somewhat higher than predicted.  All
the other values are either the same or slightly lower
than predicted, with the largest deviations found
for the most volatile substances.
   The low results for those substances that are pre-
dicted to volatilize may be because the water is much
deeper at Davis than at CRREL.  The increased water
depth probably decreases the surface area of the
air/water interface  available for gas transfer, since
much of this surface area in the shallower CRREL
system seems to be associated with plant debris and
surface irregularities, which are mostly submerged
at the Davis system. Lower rates of volatilization
may also be attributed to decreased turbulence
associated with the longer detention  time on the
Davis system.  The increased depth, on the other
hand, should not significantly affect  the surface
area of the water/soil-organic-matter interface, and
the actual rate coefficients for those  substances pre-
dicted to be removed predominantly by sorption
are close to the predicted rate coefficients

Final removal processes
   The kinetic relationships described above only
represent removal from the moving solution.  Vola-
tilization is a terminal removal process, at least with
respect to the overland flow system.  The propor-
tion of removal due to direct volatilization from
                       Table 20.  Experimental versus predicted removal rate coeffic-
                       ients for the Davis site.

                                               Rate coefficient (min'1) at 16.5"C
Substance
Phenanthrene
Toluene
Chlorobenzene
Naphthalene
Dibromochloromethane
Benzene
Pentachlorophenol
m-Nitrotoiuene
PCB 1242
Bromoform
Chloroform
2,4-Dinitrophenol
Diethylphthalate
Nitrobenzene
Experimental
0.031
0.018
0.018
0.020
0.018
0.015
0.013
0.011
0.020
0.017
0.012
0.009
0.003
0.008
Predicted
0.022
0.032
0.029
0.026
*
0.024
0.018
0.015
0.020
0.012
0.017
0.004
0.009
0.008
                      *Data not available.
                                                   26

-------
solution, however, appears to be small, even for the
most volatile substances (Table 18).  Thus, the bulk
of the initial removal from solution seems to be due
to sorption.
   Sorption, however, is not an infinite sink for these
organics. In overland flow the solution comes in
contact with only a relatively small surface area, be-
cause movement occurs rapidly with little penetra-
tion into the soil. Thus, if these substances accumu-
late on the  surface with time, desorption may reduce
the net removal rate. This may have been what hap-
pened with PCB.  If these substances are applied long
enough, removal should cease when the rate of de-
sorption equals the rate of sorption.
   To determine if these substances would accumu-
late with time, soil samples were collected periodi-
cally at the CRREL site.  Except for PCB, and to a
lesser degree PCP, the  substances did not accumu-
late. For most of these substances, then, some addi-
tional removal mechanism or mechanisms must be
operating once the substances are sorbed; the most
likely mechanisms are biodegradation and volatiliza-
tion from the soil surface. Because pentachlorophenol,
which has a lower H than PCB, accumulated to a
much lesser degree than PCB, processes other than
volatilization must be  removing some of the pre-
viously sorbed organics from the soil. In fact, of
the twelve substances tested, eight had H values sim-
ilar to or less than that of PCB, and none were found
to accumulate significantly.
   Biodegradation is difficult to model at these levels
of trace organics. Biofilm models have been devel-
oped for treating primary substrates of bacterial
metabolism (Williamson and McCarty 1976).  Rubin
et al. (1982) and Subba-Rao et al. (1982) found
that the kinetics of mineralization, the extent of
assimilation, and the sensitivity of mineralizing pop-
ulations to  several organic compounds (phenol, ben-
zene, benzylamine, aniline and  2,4-dichlorophenoxy-
late) are different at trace levels than at higher con-
centrations, both in freshwater and sewage.  They
found, for example, that the rate of phenol miner-
alization was a linear function of concentration at
levels below 1 ppm, fell off between 1 and 100 ppm,
and was again high at levels above 100 ppm. They
attributed this to the activity of two kinds of organ-
isms: oligotrophs, which are active at lower concen-
trations, and eutrophs, which are active at higher
concentrations.  Oligotrophic organisms are able to
live under conditions of very low carbon flux (less
than 1  ppm/day) and require a  lower minimum sub-
strate concentration than eutrophs, although their
maximum growth rate is also lower (Kobayashi and
Rittmann 1982). Rubin and his coworkers found
from 14C labeling that these oligotrophs assimilated
little or none of the carbon. This co-metabolic type
 of metabolism may occur because oligotrophs fre-
 quently possess several inducible enzyme systems
 and are able to shift metabolic pathways and use
 mixed substrates (Kobayashi and Rittman 1982).
   Because of the low concentrations of organics
 added to the wastewater in this study, degradation
 by oligotrophs seems plausible. Rubin et al. (1982)
 also found that mineralization was enhanced in
 waters with higher nutrient status.  Specifically they
 found greater activity in sewage than in lake water.
 Finally oligotrophs apparently prefer an attached
 rather than a free-living existence and are usually
 found living in biofilms (Kobayashi and Rittmann
 1982).  All of these factors lend credence to the
 idea of biodegradation  by organisms associated with
 the nutrient-rich organic layer covering  the overland
 flow slope following initial sorption from the moving
 water.
   A biofilm  model, similar to that of Williamson
 and McCarty (1976), is analogous to the two-film
 approach adopted here, with the rate of metabolism
 high enough to assure essentially no background at
 some distance into the  film.  This assumption was
 possibly violated only for PCB in the present case.
 If biodegradation accounts for all the secondary re-
 moval observed following sorption, the maximum
 biodegradation rate coefficient would only have to
 be 0,0167 min"1, or one-third of the maximum
 observed removal rate, because wastewater was only
 applied 8 hours per day.
   Another possible secondary removal  mechanism
 is plant uptake. Analysis of plant tops for PCB
following wastewater application yielded the results
shown in Table 16.  None of the other trace organics
added was found, with the possible exception of
pentachlorophenol, which could not be determined
because of analytical interferences.  This was not
surprising, since no detectable residues remained in
the soil either.
   Uptake and translocation of PCBs have also been
observed in other plant-soil systems (Mrozek et al.
1982). However, the relative amounts translocated
are apparently species-specific (Strek 1980), and
negative results have also been reported  (Davis et al.
1981). The preferential uptake of the PCB isomers
with lower molecular weights (Mrozek et al. 1982)
is expected because of their higher water solubility.
In this study we observed enhancement  of the heav-
ier isomers, suggesting some metabolic alteration of
the lighter isomers by the plants or soil (Strek  1980).
However, the low rate of accumulation in the edible
plant parts suggests that there is no problem with
food chain transfer, since biomagnification factors
(concentrations in plant tissue compared to concen-
tration in water) were close to 1.
                                                  27

-------
 SUMMARY AND CONCLUSIONS

   1.  Overland flow was found to be an effective
 process for the removal of trace levels of a variety
 of organic priority pollutants from municipal waste-
 water. The extent of removal was found to be a
 function of the application rate or the average deten-
 tion time of a wastewater on the overland flow slope.
   2.  The rate of removal of these substances from
 the moving solution followed first-order kinetics for
 all the substances tested, while the first-order rate
 coefficients obtained varied significantly from one
 substance to another.
   3.  The magnitudes of the rate coefficients ob-
 tained for 13 substances were consistent with two
 transport-limited, competing, first-order processes:
 sorption on soil organic matter and volatilization.
 Equations were developed for each process at 20C
 using the two-film resistance theory and the coeffic-
 ients  obtained by multiple regression analysis using
 the experimental values from the CRREL system.
 The resulting model allows the prediction of removal
 rate coefficients for a specific organic substance
 using its molecular weight, its octanol-water partition
 coefficient and its Henry's law constant.
   4. Of the 13 substances tested, PCB, and to a
 lesser extent pentachlorophenol, accumulated on
 the slope. Thus, if sorption accounts for most of
 the removal from solution, some additional mech-
 anisms must be operating once these substances are
 sorbed on the soil surface. These mechanisms are
 thought to be biodegradation and volatilization.
   5. Except for PCB, none of these organics was
 detectable in the grass collected from the site.
   6. The removal rate coefficients depended on
 temperature. The model was extended to allow pre-
 dictions at water temperatures other than 20C.
   7. The model developed with data from the
 CRREL system was tested at the Davis, California,
 municipal overland flow site. The experimental rate
 coefficients obtained for 13 substances were very
 similar to those predicted.
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                                                  29

-------
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                                                 30

-------
         APPENDIX A. EXPERIMENTAL OVERLAND FLOW DATA, HANOVER.
                Table Al.  Results for 23 June 1981  through 10 December 1981.
The types of analysis are: a) purge and trap GC/MS/SIM, b) solvent extraction (pH 12) GC/ECD, c) solvent
extraction (pH 12) HPLC/UV, d) solvent extraction (pH 2) GC/ECD. The concentration data are for the
indicated fractions of the distance down the slope.


                   EXPERIMENT: OVERLAND  FLOW - SLOPE  B
                        DATE: 23 JUNE  1981
                        APLICATION RATE:        6 U/1n>     u.i le/hr)    u.124  c*3/hr- of u1dth>
                        AIR TEMPERATURE:
                        WEATHER:  Partly  sunnyi breezy* rain  night before
                                                    CONCENTRATION
  SUBSTANCE                TYPE OF JNAL  APR   1/8     1/4    1/2    3/4    RUNOFF

 Chloroforn (ng/L)               a
 Toluene (ng/l)                  a
 Chlorobenzene (ng/l)            a
 Benzene       (ng/l)            a
 Bromolorm (ng/l)                a
 Bromoforn  (ng/L)               b
 2-Chloroethylvlnyl ether (ng/l)  b
 Unknown (ng/l)                  b
 D1broochloronethane (ng/L)      b
 Nitrobenzene  (ng/l)             b
 -Nltrotoluene  (ng/L)            b       ?7.i    16.c     9.b    2.6             i/L)                              111                    29             2
 VSS  (9/l)                               95                    14             2
 oH   (pH units)
 Time (minutes)                            1    10-b    21.2   "2.5             85
 Tenoeraturr  (C)                          If    20.u      22     23             22
 Jcoth (Ave-cn)                                  0.7     0.8    0.5
 ,/oLunu  (I)                              '5                                  I)97
 Steaoy State  Rate  (l/mln)
                                                31

-------
                        EXPERIMENT: OVERLAND FLOU - SLOPE B
                             DATE:  2b JUNE 19cl
                             APLICATION RATE:        6 
                             AIR  TEMPERATURE: 22 c
                             HEATHER: Cloudy, no ulnd* drizzle
                       0.4 tc/hr>
                                TYPE OF ANAL  APP
                                                   1/8
                                                           CONCENTRATION
                                                           1/4     1/2
                                              3/hr-n of width)
    Chloroform (nq/l)                a
    Toluene (ng/l)                   a
    Chlorooenzene (ng/L)             a
    Benzene       (ng/l>             a
    Bromoform (nq/l)                 a
    Bromoform  (ng/l)                b
    Z-ChloroethyLvlnyI ether  (ng/l)  b
    Unknown (ng/I)                   b
    01bronochLoromethane  (ng/l)      b
    Nitrobenzene (ng/L)              b
    m-Nllrotoluene  (ng/l)            b
    Olethylphthalate  (ng/l)          b
    PCB 1242  (ng/l)                 b
    Naphthalene lng/l)              c
    Phenanthrene (ng/l)              c
    31n1trophenoI (ng/l)             d
    PentachlorophenoI  (nc/l)         d
    Total-N Imq/l)
    10D log/I)'
    TOC (q/l)
    TSS (ng/l)
    ViS (ni|/l>
    n -<  (p H units)
    Time (minutes)
    Temper atu re ( C)
    }eoth (Ave-cm)
    volume ( I)
    : t e a d y Sin to ^ate  (l/jr1n)
57.3    43.2     33.0    16.1
52.1    52.1     51.1    39.D
56.2    52.5     33.2    15.3
61.1    40.J     19. /
61.6    44.1     IB.8
          88
          72
                 21
                 1=
 O.C     10.6    21.2    42.5
  Ifl       1H      19      2C
         1.1     l.u     u.i
I-52C'
                     EXPERIMENT: OVERLAND  FLOU    SLOPE B
                          DATE: 30 June  1981
                          APLICATION  RATE:         6 (l/n1n>       O.i  
                          AIR TEMPERATURE:  25  c
                          yEATHER: Sunny*  slight breeze* no rain  for  several  days
                                      u.124 (i3/hr-n of  width)
 SUBSTANCE
                             TYPE OF  ANAL   APP
                                                  1/8
                                                          CONCENTRATION
                                                          1/4      1/2
                                                                           3/4
Chloroform  (ng/l)
Toluene  (ng/L)
ChLorobenzene  (ng/l)
Benzene        
52.8
38.5
71.2
37.4
?4.9
24.9
24.0
19.8
71.2
30.7
23.4
4.8

-------
                     EXPERIMENT:  OVERLAND FLOW   SLOPE 3
                          GATE :  2 July 19 HI
                          (.PLICATION RATE:         6 u/mi
                          AH  TEIPERATIRE:  27 c
                          lEATHER:  Partly sunny* breezy
  SU3STAMCE
                             TYPE  OF ANAL  APP
 Chloroform  (no/L)
 Toluene  (ng/ I)
 Chlorobenzene  (ng/l)
 3enzene        (nq/l)
 Bronofortf  (ng/l)
 iromoform   (n^/l)
 ") 1 bromoch I orome t h ane  lny/l)
 nitrobenzene  (nq/l)
 TI-N1 t ro t o L uene  (ng/l)
 'Jlethylphthalate  (ng/l)
 PCB  1242   (ng/l)
 Naph thalene (ng/l)
 Phenanthrene  (ng/L)
 01n1trophenol  (ng/l)
 Pentachlorophenol  (ng/L)
 Total-N  (mg/l)
 300  (mg/l>
 TOC  (mg/l)
 TSS  (mg/l)
 VSS ,(mg/l )
 PH   (pH  units)
 Time  (minutes)
 Temperature (-C)
 Oepth  (Ave-cfl)
 Volume (I)
 Steady State  Rate  (l/mln)
 60.5
 33.1
                                                 1/8
 15.t
 30.3
                        O.i  tcm/hr)
                                                         CONCENTRATION
                                                         1/1     1/2
 21.b     13.1     11.M
 28.7     24.1     21.9
 28.1     18.9     14.u
                  5.7
                  6.7
         17.6
          1.6
86
75
7.3
0.0
18

42
36
7.2
14.9
20
1.7
32
29
7.2
29.8
23
1.6
9
a
7.0
59.5
26
1.0
                                       0.121  (n*3/hr-m of uldth)
                                  O.D
                                  2.1
                 i.8
                 l.D
                                            5
                                            3
                                          i .u
                                          119
                                           27
                    EXPERIMENT: OVERLAND FLOU
                         DATE: 7 July i9i
                         APLICATION RATE:
                         AIR TEMPERATURE: 29 c
                         WEATHER: Sunny* breezy
 SUBSTANCE
                            TYPE OF ANAL  APP
Chloroform 
D1n1trophenoI (ng/L>
Pentachlorophenol (ng/l)
Total-N (ig/l>
BOD (g/l)
TOC (>g/l)
TSS (g/l)
VSS dg/l)
pH  (pH units)
T1ae (aVnutes)
Tenperature (C)
Depth (Ave-CB)
Voluie  (I)
Stedy  State  Rate (l/n1n>
 108
  91
 u . 0
  19
2340
   6
  11.
  37
 7.5
14. 1
  21
                                                        CONCENTRATION
                                                        1/1     1/2
21.0    12.7     9.1
37.1    10.3    28.3
29.9    25.9    12.9
36.7    21.2     B.6
34.0    15.8     6.4
  26
  24
 7.5
29.8
  23
 2.0
                 0.7
                 5.3
                 5.3
                 0.6
                 0.3
  10
   9
 7.3
59.5
  26
 1.2
                                                3/h r-m  of  width)
 7.7
 119
  26

1046
 i . 3
                                                  33

-------
                     EXPERIMENT: OVERLAND FLOU    SLOPE  B
                          DATE: 9 July 1931
                          OPLICATIOV RATE:         6  u/m
                          SIR TEMPERATURE: 32 c
                          JEftTHER: Sunnyr slight  breeze
                                     0.1 (cm/hr)     0.121  (*3/hr-l of iildt'h)
 SUPSTANCE
                             TYPE OF ANAL
                                           APP
Chloroform  (nq/l)
Toluene  (nu/l)
Z h Lo robenz ene  (n>J/l)
J enz ene        (nu/l>
Iro-nofori1 tn"/L)
J rOTio f o rm   (m/L)
Jiororriocnlororneth.ine  (nq/L
Jitrobenzene  (n-j/l)
T-IJI t ro to luene  (nu/l)
Jictnvlphthalate  
' C :- 1212  < n i / I >
J ii p T t n a 11' ! e  (nq/l)
Jhenffnthrrne  tnn/l)
Tinitrpphrnol  
^entachlnropnenol  (ni/l)
r o t a I - '1  < T i. / I )
!OD < rg/l)
TOC (-0/1)
F 'j 3 ( n = / I )
J3o (-sg/l)
i H  (u H  units)
T-He (minutes)
TemDerature  (C)
'Jtoth (Aup-c^)
Volume  (I)
iteaax  r.tjte  Sate  (l/jiin)
                                                  1/B
                                                          CONCENTRATION
                                                          1/1     1/2
43. <:
&2.b
37.7
118. H
>8.a
31.4
70.0
25.2
9
B1
7. jl
C.O
21

Ib.j
11. -J
1 J.O
67. C
22.2
61.7
11.0
19.3
tr
35
7.3
11.3
23
1.2
15.1
11.2
11.7
50.3
11. 2
11.5
27.0
20.6
23
21
7.3
29. B
21
1.2
1.0
K.4
2.3
6.7
1.0
17.3
3.9

11
10
7.1
59.5
27
1 .1

ChIDrobenzene  (ng/l)
3enzene        (nq/l)
3ronoform  (ng/l)
Jromotorm   (ng/L)
~l i bromo ch lorome t h ane  (ng/l)
Nitrobenzene  (ng/l)
n-N1trotoLuene  (ng/l)
OlethyLphthalate  (ng/l)
=CB 1212   (ng/l)
Naphthalene  (ng/l)
a hen an t h r me  (nq/l)
J initrophenoI  (13/L)
^ent ach lorophcno I  (ng/L)
rpta L-N  (Tg/l)
JOD (ng/I>
TOC lng/l)
TSS (g/l)
y^S (ng/L)
3H  (pH units)
Time (minutes)
Temperature  (C)
3epth  (Ave-cn)
t/olume (I)
Steady State Rate  (l/n-in)
TYPE OF ANAL  APP
     a       32. /
     a       36.5
     a       26.3
b
b       5 D 
b       40.
b       39.
1/8

 15.u
 12.B
 10.B
                                                          CONCENTRATION
1/1
 13.b
 10.b
                                                                  1/2
                                                                          3/1
                                  7.5
                                   
-------
                       EXPERIMENT:  OVERLAND FLOU - SLOPE B
                            DATE:  it July 1981
                            APLICATION RATE:         6 (l/m1n>
                            AIR TEMPERATURE:  26 c
                            WEATHER: Sunnyi. breezy* dry
                                       0.4  
   Bromoforn  (ng/l)
   DIbronochloromethane  (ng/l)
   Nitrobenzene (ng/l)
   m-N1t rotoluene  (ng/l)
   Dlethylphthalate  (ng/l)
   PCS 1242  (ng/l)
   Naphthalene (ng/l)
   Phenanthrene (ng/l)
   D1n1trophenol (ng/l)
   Pentachloropheno I (ng/l)
   Total-N (mg/l)
   SOD (ng/l)
   TOC (mg/l)
   TSS (g/l)
   VSS (mg/l)
   pH  (pH units)
   Time (minutes)
   Temperature (C)
   Depth  (Ave-cm)
   Volume  (I)
   Steady  State Rate (l/m1n)
                 219
                 It2
                2520
                   h
                                                   1/8
                                                           CONCENTRATION
                                                           1/4     1/2
                41.6     30.0     29.3     11.-.
                63.5     51.0     35.1     15.1
                55,?     35.2     26.B     11.i
                        11.9    29. H     ">9.b
                          19      15       ?r
                         1.2     1.3      C.5
                                     923
                                     3.2
                    EXPERIMENT: OVERLAND FLOM   SLOPE B
                         DATE: 21 July 1981
                         APLICATION RATE:        6 
                         AIR TEMPERATURE: 29 c
                         yEATHER: Humldt breezyi partly sunnyt
                                    0.4 (cm/hr)
 SUBSTANCE
Chloroform (ng/l)
Toluene (ng/l)
Chlorobenzene (ng/l)
Benzene       (ng/l)
Broioforn (ng/l)
Broaoform  (ng/l)
01brOHOChloronethane (ng/l)
Nitrobenzene (ng/l)
m-N1trotoluene (ng/l)
Olethylphthalste (ng/l)
PCB 1242  (ng/l)
Naphthalene (ng/l)
Phenanthrene (ng/l>
D1n1trophenol (ng/l)
PejitachlorophenoL (ng/l)
Total-N (mg/l)
BOD (g/l)
TOC Og/ll
TSS (g/l)
VSS (g/l)
pH  (pH un1t>>
T1e dlnutet)
TeHperature (C)
Depth  (Ave-cm)
Volume  (I)
Steady  State Rate (l/mln)
TYPE OF ANAL  APP

     a       58.1
     a
     a      109.5
              0.0
               19
             2340
                6
1/8

 22.B

 23.0
 1'4.9
   20
  1.7
CONCENTRATION
1/4     1/2

 16.1
                             16.4
 29.8
   20
  1.5
rain yesterday
         3/4
   3.9
                                      2.2
  59.5
    21
   1.0
0.124 (m3/hr-m of uldth)



RUNOFF

   3.9

   0.5
   119
    21
                                 195i
                                  5.7
                                                    35

-------
                     EXPERIMENT:  OVERLAND  FLOU  - SLOPE  e
                          DATE:  23  July  1981
                          APLICATION  RATE:         6  (i/in>
                          AIR  TEHPERATURE:  23  c
                          WEATHER:  Dry*  partly  sunnyt  very  ylndy
                                            5.4 (cm/hr)
                                                           0.12<)  (B*3/hr-m  of  uldth)
  SUBSTANCE
Chlorofora  (ng/l)
ToLuene  
BroBofora   (ng/L)
DlbroBochloroBethane  
Nitrobenzene  (ng/l)
B-N1trotoluene  (ng/l)
DlethylphthaUte  (ng/l)
PCB  1242   (ng/l)
Naphthalene  (ng/l)
Phenanthrene  (ng/l)
D1n1trophenol  (ng/l)
Pentaehlorophcnol (ng/l)
Total-N  (BO/l)
BOD  (ig/l)
TOC  (g/l)
TSS  (g/l)
VSS  (Bg/l)
pH   (pH  unite)
T1e  (Minutes)
Teaperature  (C)
Depth  (Ave-ci)
Voluae (I)
Study Stat Rat* 
OF
a
a
a
a
a
b
b
b
b
b
b
c
c
d
d








ANAL APP
17.1
9.S
2 2'. 7


49.8


49.2
46.1
36.4


128
13.4
26.3
B1.7
263
130
0,0
IB

2520
1/B
9.5
3.3
12.2


27.5


27.2
41. z
25.3.


102
11. B
17.3
56.1
83
62
14.9
18
z.u

CONCENTRATION
174 1/2
b.8 1.8
2.* Cd
J.t 0.2


27.3 11. a


27.0 11.2
36.1 17.4
24.3 14.4


57.9
1.6
20..0 11.7
50.7 30.1
12
11
29.8 59.5
IB IB
u.7 0.8

3/4 RUNOFF
1.2
(a
Cd





Cd




39.9
0.5
6.4 5.4
22.1 20.5
3
3
89. J 119
20

97?
                                                                 0.4  (cn/hr)     0.12
     AIR  TEMPERATURE:
     UfATHER:
                                    CONCENTRATION
        TYPE OF ANAL  APP    1/8     1/4      1/2      3/4     RUNOFF
Chloroform  (ng/L)
Toluene  (ng/l)
Chlorobenzene  (ng/l)
Benzene        (ng/l)
BroBoform (ng/L)
BrOBOform   (ng/l)
Dlbronochloronethane (ng/L)
Nitrobenzene (ng/L)
m-N1trotoluene (ng/L)
Dlethylphthalate (ng/l)
PCB 1242  (ng/l)
Naphthalene (ng/l)
Phenanthrene (ng/l)
D1n1trophenol  (ng/L)
Pentachlorophenol (n0/l)
Total-N  (iig/l)
BOD (Bg/L)
TOC (Bg/l)
TSS (Bg/l)
VSS (Bg/l)
pH  IpH units)
Tlae (Blnutes)
TeBperature (C)
Depth (Ave-CB)
VolUBe (I)
Steady state Rat* (l/Bln>
                     20.3      k.S
                     13.1      1.1
                     50.2     11.4
bS.O    61.2
40.0    24.4
        27.1
        10.7
75.7
  70

 6.9
 0.0
  18

2520
   6
7.1
7.5
 IB
5.B
2.b
                             44.0    43.9
                               38      3B
 6.9
15.0
  18
                                             38.3
                                             22.4
                                              6.7
                                              2.b
                                              7.0
                                             30.0
                                               19
                                                     11.B

                                                     42.8
                7.3
               45.0
                 19
                                         1.5
                                          Cd
                                        0.1?
                       15.?
                        5.5
                         Cd
                         Cd
                                         6.9
                                          60
                                          20

                                        1645
                                         b.l
                                                 36

-------
                     EXPERIMENT:  OVERLAND  FLOU  - SLOPE  B
                          DATE: 13  August  1981
                          APLICATION  RATE:        12  
                                                                 0.8  (o/hr)
                                                         v
                          AIR  TEMPERATURE:  20  C
                          UEATHER:  Cloudy,  slight  breeze  fro.  south
  SUBSTANCE
                             TYPE  OF  ANAL   APP
                                                 1/8
                                                         CONCENTRATION
                                                         1/4
                                                                 1/2
                                                                         3/4
 Chloroform  (ng/l>
 Toluene  (ng/l)
 Chlorobenzene  (ng/l>
 Benzene        (ng/l)
 Broioforn  (ng/l>
 Broaoforn   (ng/l)
 DlbronochloroBethane  (ng/l)
 Nitrobenzene  (ng/l)
 S-N1trotoluene  (ng/L)
 Dlethylphthalate  (ng/l)
 PCB  12*2   (ng/l)
 Naphthalene (ng/l)
 Phenanthrene  (ng/l)
 DInltrophenol  (ng/l)
 Pentachlorophenol  (ng/l)
 Total-N  
 pH   (pH  units)
 T1 e  (Blnutes)
 Tenoerature (C)
 Depth  (Ave-cn)
 Voluie  (I)
 Steady  State  Rate  (l/>1n>
                                                                                0.248  (>*3/hr-> of  uldth)
b
b
b
b
b
b
c
C
d
d








13.3


42. B
10.7
68. B
23.9
29.3



113
82
79
61
0.0
13

26.8


26.4
33.7
47.0
20.2
17.0


21.3
81
66
35
32
8.4
19
1.9
24.5


24.3
29.5
34.4
5.8
7.7


21.0
70
48
26
23
16.8
19
1.4
12.8


12.6
19.6
15.2
g/l>
TOC (ng/l)
TSS (.8/D
VSS (g/l)
pH  (pH units)
T1ne (Minutes)
Temperature (C)
Depth  (Ave-cn)
Voluie  (I)
Str  State Rate  (l/iln)
  61
  S3
 0.0
  17
5133
  12
                                                        CONCENTRATION
                                                        1/4     1/2
                                                                        3/4
                                                                               RUNOFF
        12.3
 46
 42
35
27
                         9.2
20.2    12.1    14.9     9.1
31.4    19.2    21.6    13.9
18.8    13.6    10.9     3.8
8.4    16.8    33.5
 IS      IS      19
2.2     1.4     0.8
                        7.6
                        9.7
                        2.5
              50.3
                19
               1.1
                       5.4
                       1.5
                       1.0
67
20
                               3076
                                8.5
                                                   37

-------
                     EXPERIMENT:  OVERLAND FLOU   SLOPE D
                          DATE:  3  September 1981
                          APL1CATION  RATE:        12 (l/1n>
                          AIR TEMPERATURE:  20 C
                          UEATHER:  Cloudyt  slight breeze
 SUBSTANCE
Chloroforn  
Bronoforn   (ng/l)
OlbroBochloronethane (ng/L)
Nitrobenzene  (ng/l)
-N1trotoluene  fng/L)
Dlethylphthalate  (ng/l)
PCB 1242   (ng/l)
Naphthalene  (ng/l)
Phenanthrene  (ng/l)
D1n1trophenol  (ng/L)
Pentachlorophenol  (ng/L)
Total-N  lug/I)
BOD dg/l>
TOC (>g/L)
TSS (g/l)
VSS (>g/l)
PH  (pH units)
T1e (Minutes)
Temperature (C>
Depth (Ave-ci)
Volune (I)
Steady State Rate  (l/i1n)
                          TYPE  OF  ANAL   APP

                                a        22.6
                                3         1.4
                                a        37.0
                                                  1/fi
                                                          CONCENTRATION
                                                          1/4      1/2
        30.1      7.7
          1.5       
                           AIR TEMPERATURE:  14 c
                           UEATHER: Cloudy *  cool  breezyt  rain
                                                              0.8 (CB/hr)
                                                                             0.248 f**3/hr-  of  width)
                              TYPE OF ANAL  APP
                                                  1/8
                                                         CONCENTR ATION
                                                         1/4     1/2
Chlorofor* (ng/L )                a
Toluene ( ng/l )                   a
Chlorobenzene  (ng/ll             a
Benzene                    a
Rronof or*  (ng/ll                ,.a
aronof orm   (ng/l >                b
2-Chloroethylvlnyl  ether  (ng/l)  b
Unknown (ng/ I >                   b
DlbronochLoronethane  (ng/L)      b
Nltrobenzene(ng/L)              b
m-Nltrotoluene  (ng/L)            b
OlethyLphthalate  (ng/l)          b
PCB 1242  (na/l)                 b
Naphthalene (ng/l )               c
Phenanthrene  (ng/l)              c
D1n1 trophenol  (ng/L )             d
Pentachlorophenol  (ng/L)         d
Total-N (Bg/l)
riOD (mq/l)
TOC 
-------
                    EXPERIMENT: OVERLAID FLOU   SLOPE A
                         DATE: 29 September 1981
                         APLICATION RATE:        6  u/min>
                         AIR TEMPERATURE:  10 c
                         yEATHER: Breezxi  1ndx> rain last nloht
                        u.f-  (cm/hr)
 SUBSTANCE
                            TYPE OF ANAL  APP
Chloroform 
Chlorobenzene (ng/l)
Benzene       (ng/l>
Broaoform (ng/L)
Bromoform  (ng/l)
Olbromochloronethane (ng/l)
Nitrobenzene  (ng/l)
m-N'11rotoluene (ng/l)
Olethxlphthalate (ng/l)
PCB 12A2  (ng/l)
Naphthalene (ng/l)
Phenanthrene  (ng/l)
01n1trophenol (ng/l)
Pentachlorophenol  (ng/l)
Total-N (ms/l)
BOO (mg/l)
TOC (mg/l)
TSS (mg/l)
VSS (mg/l)
pH  (pH units)
Tine (Minutes)
Temperature (C>
Depth (Ave-cm)
Volume (L)
Steadx State  Rate  (l/m1n>
  0.0
   16
                                                1/8
                                                        CONCENTRATION
                                                        1/1      1/2
 21.1     11.2    10.1     1.9
  1.7      0.6     0.5    S.CR
 71.5     32.0    19.9     5.3
5.75
11.5
 1.8
23.0
12.5
 1.0
31.5
  12
 O.E.
                                       0.218 (m**3/hr
                              R J N 0 - F

                                 2.7
                                  
-------
E X'EKIIEMT: OVERLAND




SUtiSTANCC
ChLorofom tno/L)
Toluene (ng/L)
Ch 1 D rob en? ene (nq/L)
benzene ( na /I )
dronoform ( n j/l )
3 romo f orm (nq/L)
i) 1 bromo ch loromet h ane (ng/
m-N1 t rot o luene (nu/L>
Illethylpn thalate (ng/l)
PCB 1242 (ng/l)
Naphthalene (ng/L)
Phenanthrene (ng/l)
0 1 n1 1 roph eno L (ng/L)
Pent achlorophenol (ng/l)
Total-N (nig/1)
300 (mg/l>
IOC (Jig/L)
TSS (ng/l)
VSS 
TOC fg/l>
TSS (g/L)
VSS (pg/l)
PH (pH units)
Time (minutes)
Temperature ( C )
Jept h ( Ave-cm )
Volume (I)
b
b
b
b
c
c
d
rt








Steady State Rate (L/ii1n)
: 18 (l/"1n> 1.2 (c./hr) 0.372 (n3/hr-i of uldth)
: 7.1 C
CONCENTRATION
APP 1/8 1/4 1/2 3/1 RUNOFF



81.6 61.3 15.7 29.1 20.7
53. b 53.2 26.6 18.3 o.7
1088 832 576 499 397
10.9 7.5 1.8 2.8 1.6

56.0 59.2 38.2 26.5 22.5
86.0 103.1 79.0 69.3 68.3
21. 1 21. r 13. b 8.2 7.3
51.1 33.9 21.3 10.2 3.8
81.0 21.0 28.1 23.0 24. b

76 69 10 33 25 19
?9.b 28.1 21. b 21. b 16.6 16.2
41 49 17 17 11 7
37 42 15 15 1C 7

0.0 3.B 7.3 15.0 22.5 30
12. b 12. u 12. u 11.6 10.2 10.5
1.5 1.5 1.1 !.)
72C1 9971
jo 30.7
40

-------
                      EXPERIMENT: OVERLAND FLOW   SLOPF e
                           DATE:  2^ octooer 1951
                           iPLICATION RATE:        6 U/nin>       ?.t
                           AIR TEMPERATURE: 5.f C
                           WEATHER: C loudy  rai nea Last several  days
   SUBSTANCE
                              TYPE OF ANAL
                                            AP?
 Chloroform  (ng/l)
 T o Luene  < ng/I)
 Chlorobenzene  (nq/L)
 Benzene        (ng/I )
 3rooform  (ng/L)
 Bromoform   (ng/L)
 Olbrofflocnloromethane  (ng/L)
 Nitrobenzene  (ng/L)
 n-NltrotoLuene  (ng/L)
 OlethyLphthalate  (ng/L)
 PCB  1212   (ng/L)
 Naphtha Lene (ng/L)
 Phenanthrene  (ng/L)
 DlnltrophenoL  (ng/L)
 PentachLorophenoL  (ng/L)
 Total-N  
                                                         CONCENTRATION
                                                         1/1     1/2
b
b
0
b
b
b
c
c
0
d
63.8
8.=
75
19.1
73.5
18.9
32.1
29.2
17.5
16.0
31. b
3.9
60.6
10.5
68.1
12.7
18.8
9.6

11.1
21.6
2.0
51.0
30.9
51.5
10.0
11.9
1.0
37. D
7.b
12.3
0.87
17.5
26.0
51.1
7.9
3.0
1.7
23.9
4 .El
6.1
0.11
36.9
17.5
32.0
1.0
l.t
o.a
22.1
2.2
 0.0    11.
  13      13
         i  u
2566
   6
21.0
11.a
57.0
  11
                                      0.121  (**3/hr- of  yldth)
81.0     108
  11    10.2
 1.1
        1379
         1.8
                                                     41

-------
                    EXPERIMENT: OVERLAND FLOU - SLOPE B
                         DATE: 13 Noveiber 1981
                         JIPLICATION RATE:        & d/in>
                         AIR TEMPERATURE: 6 c
                         VEATHER:
0.4 (en/he)
               0.124 (*3/hr- of width)
 SUBSTANCE
                            TYPE OF ANAL  APP   1/8
                                                        CONCENTRATION
                                                        1/4     1/2
                                                                        3/4    RUNOFF
Chloroform (ng/l)
Toluene 
BroMofori fng/L)
BroMofori  (ng/l)
Dlbroaochloroaethane (ng/l)
Nitrobenzene (ng/l)
-N1trotoluene (ng/l)
Dlethylphthalate (ng/l)
PCS 1242  (ng/l)
Naphthalene (ng/l)
Phenanthre.ne (ng/l)
D1n1trophenoI (ng/l)
Pentachlorophenol (ng/l)
Total-N (g/l)
300 (g/l)
TOC (ig/l)
TSS (iig/l)
VSS (>g/l)
pH  (pH units)
T1e (Minutes)
Tenperature (C)
Depth (Ave-cB)
Volume (I)
Steady State Rate (L/
  SUBSTANCE
Chloroforn  (ng/l)
Toluene  (ng/l)
Chlorobenzene  (ng/l)
Benzene        (ng/l}
BroBoforn (ng/L>
BrOBOfom   (ng/l)
Dlbronochloronethan
Nitrobenzene  (ng/l)
B-N1trotoluene (ng/l)
Dlethylphthalate  (ng/l)
PCB 1242  (ng/l)
Naphthalene  (ng/l)
Phenanthrene  (ng/l)
D1n1trophenol  (ng/l)
Pentachlorophenol  (ng/l)
Total-N  (ig/l)
BOD (ng/l)
TOC (g/l>
TSS (g/l*
VS'S (ng/l)
pH  (pH units)
T1 ne (o 1nutes)
Tenpera t lire  (C)
Depth  (Ave-cn)
Volume (I)
Steady State Rate  (l/
(ng/l)
>
i/l)
ig/l)
EXPERIMENT:
DATE: 2
APLICAT
AIR TEM
HEATHER
TYPE
1
I
; (ng/l)
t>
;/l)

ig/l)
b 56.2
b 7.3
b 48. 3
b 39.8
b 75.6
b 19.6
c 32.6
c 19. b
d
d 36.1
73
26.1
4.9
41
(1.0
10
2279
6
OVERLAND FLOU
4 November 1981
ION RATE:
PERATURE: -i c
OF ANAL
a
a
a
a
a
b
b
b
b
b
b
c
c
d
d
APP
99.6
13.2
60.3
48.3
69.3
25.4
64.1
28.3
17.5
18. D
0.0
9
2520
6
40.7
4.9
48.2
39.1
61.4
18.4
17.2
8. 2
23.4
20
17.1
13
11
13.5
9
1.3
SLOPE B
6 (l/
1/8
58.2
6.8
52.2
38.5
61.4
14.7
24.2
5.5
14. 2
10.8
13.5
7
1.6
33.8 23.1 13.9
3.3 1.9 u.91
44.3 44.5 41.2
32.b 31.U 25.7
54.? 41. B 31.4
b.2 3.4 3.0
10.4 4.1 
CONCENTRATION
1/4 1/2 3/4
52.9 22.2 20.0
5.9 2.0 1.7
49.5 39.3 35.0
34.5 23.5 20.0
57.7 46.7 41.2
6.9 5.8 4.6
19.8 5.7 
-------
EXPERIMENT: OVERLAND FLOU
     DATE: 2 December 1981
     SPLICATION RATE:
     AIR TEHPEtATURE: 3 C
6 (L/1n>
               0.4 (ci/hr)
                              0.124  (3/hr-ii  of  width)
WEATHER
SUBSTANCE TYPE
Ch loroform ( ng/L )
T o Lu ene ( ng/ L )
Chlorobenzene (ng/L)
'Benzene (ng/L)
Bromoform (na/L)
3romof orm ( ng/L >
Jlbromochloromethane (ng/L)
n-NltrotoLuene (ng/L)
JlethyLphthaLate (ng/L)
PCB 1242 (ng/L)
Japhtha Lene ( no/ L )
Phenanthrene (ng/l)
01nltropher>oL (nq/l)
PentschlorophenoL (ng/L)
Total-N (,7iy/L)
D 0 D ( " 3 / L )
TOC (ng/L )
F S S ( -n q / L)
V S S (ng/l)
nH (pri units)
Time (nlnutes )
To*ocrdture (C)
) ent n ( A v e-c n )
V o L j T e ( 1 J
EXPERIMENT:
OF ANAL
a
a
a
a
a
b
b
b
b
b
b
c
c
d
d









OVERLAND
APP
31.3
2.0
40.0


105
14.1
68.4
64.8
78. 1
37.1
72.8
37.3
68.0
37.7

80
44.2
43
4?
6.0
0.0
7

C793
FLOU -
CONCENTRATION
1/8 1/4 1/2
16.0 11.6 8.91
0.93 0.67 0.32
17.8 11.1 4.76


52.7 37.0 27.6
6.4 5.1 3.1
53.3 50.2 44.0
44. > 38.8 30.4
68.3 67. J 56.1
15.0 b.6 -t.7
24.1 14. J D.72
7.0 ^.34 1.66
86.0 45.0 29.7
32.0 27.7 13.6

37 29 24
31.? 25.3 23.2
29 12 13
23 1C 11
6.9 6.9 6.9
13.5 27.0 54.0
5.5 4.5 0.5
1.' 1.0 1.7
SLOPE DA
last night
3/4 RUNOFF
4.75 2.42
0.27
2.49 1.35


19.8 14.0
2.1 1.1
29.6 31.2
17.6 18.1
3R.7 45.2
5.3 6.5
0.79 2.37
1.26 1.09
36.3 2S.1
12.0 5.6

21 19
20.2 20.1
B 7
7 7
6.7 6.9
31.0 103
0 0
0.9
2149
6.2
DATE: 10 December 1981
APLICATION RATE:
AIR TEN
yEATHER
SUBSTANCE TTPE
Chlorofom (ng/l)
Toluene (ng/l)
Benzene (ngyi)

2-Chloroethylvlnyl ether (ng/l)
Unknown (ng/L)
Dlbr.oaochloroBethane (ng/l)
Nitrobenzene (ng/l)
-N1 trotoluen* (no/I)
Dlethylphthalate (ng/L)
PCB 1242 (ng/l)
Naphthalene (ng/l)
Phenanthrene (ng/l)
01n1 trophenol (ng/l)
Pent achloropheno I (ng/L)
Total-N (ig/l)
BOD (g/l)
TOC dig/I)
TSS (ng/l)
VSS (ng/l)
->H (pH- onlt s )
T1ne (nlnutes)
TeBperature (C)
leptli (Ave-cn)
VoLuap (I )
Steady State Rate (l/nln)
PERATURE
OF ANAL
a
a
a
a
a
b
b
b
b
b
b
b
b
f
c
d
d











: 16 c
APP
51.1
70.7
88.9
78. b
134
187

118
144
107
179
149









21.3



64 (l/iln) (c>;

CONCENTRATION
1/8 1/4 1/2
32.8 29.7 10.1
23.3 18.1 D.59
31.6 25.7 7.74
36.0 30. j 10.3
55.5 48.1 24.5


33.5 41.2 36.7
38.1 45.1 31. u
88 65.9 74.7
49. B 38.6 10.7
23.3 15.2 2.U









16.4 15.6 13.1
2.5 z. 3 z.5


rhr) u.16 (*
3/4 RUNOFF
1.84
11.72
0.85
1.52
3.5


24.3 13.3
19.0 o.b
69.8 54.2
6.1 2.66
l.b 1.22









13.3 12. b
1.5


                                                                   3/hr- of width)
                               43

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Table A2. Experimental first-order rate coefficients, CRREL site.
                                   exp
                                      (min~ )
Date
23 June
25 June
30 June
2 July
7 July
9 July
14 July
16 July
21 July
23 July
28 July
13 Aug
18 Aug
3 Sept
24 Sept
29 Sept
14Oct
21 Oct
29Oct
3 Nov
13 Nov
24 Nov
2 Dec
/t(20C)
A verage
water
temp. (C)
21
19.3
22
23.7
23.7
25.7
18.7
19.7
20.3
18.7
19.0
19.3
18.7
18
15
13.5
14.8
11.6
10.2
11.4
6.7
5
2.5

Chloro-
form

_
_
_
__
_
0.022
0.023
0.022
0.023
0.038
_
__
0.047
_
0.045
0.017
_
_
_
_
_
0.021
0.030
Toluene
_
-
_
_
_
_
0.042
0.032
_
0.047
0.114
_
_
0.064
_
0.127
0.066
_
_
_
_
_
0.024
0.070
Chloro-
benzene
_
-
-
-

-
0.030
0.032
0.043
0.080
0.093
_
_
0.091
_
0.105
0.041
_
_
_
_
_
0.030
0.064
Bromo-
form
_
-
_
_
_
_
0.036
0.026
0.024
0.023
0.035
0.029
0.018
0.045
0.035
0.045
0.022
0.039
0.030
0.027
0.018
0.020
0.017
0.032
Dibromo-
chloro-
methane

_
0.050
_
_-
_
_
_
_

_
.
_
0.051
0.048
0.062
0.029
0.054
0.039
0.035
0.028
0.027
0.021
0.053
Nitro-
benzene

_
_
_

_
_
_
_
_
_
_
_
_
_
_
_
_
0.019
0.008
0.003
0.008
0.008
0.018
m-Nitro
toluene
0.040
0.021
0.035
0.033
0.037
0.062
0.043
_
_
0.023
-
0.027
0.018
0.035
0.027
0.025
0.011
0.029
0.026
0.012
0.007
0.013
0.012
0.030
Diethyl-
phthalate

0.017
_
0.024
0.030
0.031
0.028
_
_
0.017
0.025
0.014
0.020
0.021
0.014
0.012
0.008
0.010
0.017
0.009
0.011
0.008
0.006
0.022
PCS
0.030
0.026
0.042
0.024
0.031
0.045
0.034
_
_
0.015
0.030
0.052
0.044
0.061
0.031
0.036
0.026
0.037
0.032
0.015
0.020
0.020
0.013
0.035
Naph-
thalene
0.054
0.038
0.039
_
0.071
0.051
_
_
_
_
0.061
0.084
_
0.069
0.043
_
_
0.071
0.039
0.040
0.037
0.042
0.029
0.056

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    APPENDIX B. DOWNSLOPE REMOVAL CHARACTERISTICS OF SELECTED CHEMICALS AT CRREL AND
    AT DAVIS.
        o-
 In (C/C0)
       -2
       -3
       -4
       -5
       -6
1          I
       Chloroform
        2 Dec '81
        k= 0.021
                  30       60
                       Time (min)
                                     90
                                              120
                         In (%,
                                                                     120
Figure Bl.  Downslope removal characteristics, for chloro-
form at CRREL.
                        Figure B2. Downslope removal characteristics for PCB1242
                        at CRREL.
In (c/Cl
       -2
       -3
       -4
       -5
       -6
                             	1	
                              Pentachlorophenol
                                 9 Jul'81
                                 k = 0.043
                  30
                           60
                       Timelnun)
                                    90
                                              120
Figure B3. Downslope removal characteristics for penta-
chlorophenolat CRREL.
                                                    In (c/(
                                                   60
                                               Time (min)
                                                                                                 120
                        Figure B4.  Downslope removal characteristics[for bromo-
                        form at CRREL.
                                                 45

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 In (C/C0
                                    Phengnthrene
                                      24 Sep'81
                                       = 0068
In (c/(
                    30         60
                          Time (min)
                                                  120
                             60
                         Time (min)
                                                                                                           120
Figure B5.  Downslope removal characteristics for phenan-
threne at CRREL.
Figure B6. Downslope removal characteristics for chloro-
benzene at CRREL.
 In (%,
        -3
        -4
        -5
        -6
                   30
                                  	1	

                                   m- Nitrotoluene
                                      18 Aug '81
                                      k = O.OI8
                              60
                         Time (min)
                                        90
                                                  120
In (C/C|
                              60
                         Tim* (min)
120
Figure B7. Downslope removal characteristics for m-nitro-
toluene at CRREL.
Figure B8.  Downslope removal characteristics for nitroben-
zene at CRREL.
                                                      46

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In (c/c
                                       120
                                    Time (min)
                                                      180
                                                                     240
     Figure B9. Downslope removal characteristics for PCB 1242 at Davis.
                        60
                                       120
                                    Time (min)
                                                      180
240
     Figure BIO. Downslope removal characteristics for toluene at Davis.
                                   47

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A facsimile catalog card in Library of Congress MARC
format is reproduced below.
Jenkins, T.F.
  Assessment of the treatability of toxic organics
by overland flow / by T.F. Jenkins, B.C. Leggett,
L.V. Parker, J.L. Oliphant, C.J. Martel, B.T. Foley
and C.J. Diener.  Hanover, N.H.: Cold Regions Re-
search and Engineering Laboratory; Springfield, Va.:
available from National Technical Information Ser-
vice, 1983.
  vii, 59 p., illus.; 28 cm. ( CRREL Report 83-3. )
  Bibliography:  p. 28.
  1. Land treatment.  2. Organic compounds.
3. Oveland flow.  4. Wastewater treatment.
I. Leggett, D.C.  II. Parker, L.V.  III. Oliphant,
J.L.  IV. Martel, C.J.  V. Foley, B.T.  VI. Diener,
C.J.  VII. United States. Army. Corps of Engineers.
VIII. Cold Regions Research and Engineering Laboratory,
Hanover, N.H.  IX. Series:  CRREL Report 83-3.

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