Characteristics of Composts Moisture Holding and Water Quality

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					                                                CENTER FOR TRANSPORTATION RESEARCH
                                                  THE UNIVERSITY OF TEXAS AT AUSTIN

                                                               Project Summary Report 0-4403-S
    Center for
                                              Project 0-4403: Characteristics of Compost Enhanced Topsoils: Moisture
    Transportation Research
          The University of Texas at Austin                   Holding and Water Quality Improvement
                                                Authors: Christine J. Kirchhoff, Joseph Malina, Jr., and Michael Barrett
                                                                             August 2003

                                 Characteristics of Composts: Moisture Holding
                                        and Water Quality Improvement
                Introduction                              rights-of-way, the effectiveness       composted materials;
                                                          of various classifications of        • Application rates of compost
                   Composted manures, com-

                                                          compost in retaining moisture,         alone as well as compost
                post-amended soils, and erosion           in removing constituents of            manufactured topsoil (CMT)
                control compost (CMT and                  highway runoff, and in overall         to slopes, medians, and
                ECC) were applied to highway              improvement of water quality           other green areas in highway
                rights-of-way as a means to               in receiving waters has not been       rights-of-way;
                beneficially dispose of excess             defined in detail. The objectives     • Water-holding capacity and
                manure produced in parts of               of this research project are to        pollutant attenuation charac-
                Texas. These efforts demon-               establish the moisture holding         teristics of CMT
                strated that the application of           capacity of different classes of       The moisture-holding capac-
                composted manures was suc-                compost-amended soils and the       ity and the physical, chemical
                cessful in establishing vegeta-           ability of the compost mixtures     and microbiological character-
                tion and controlling erosion on           to retain pollutants commonly       istics of composted manures

                highway embankments. TxDOT                found in highway stormwater         (dairy cattle, poultry litter, and
                reports that composted manures            runoff.                             feedlot) and composted biosol-
                have been used beneficially,                                                  ids were determined. Compost
                usually with excellent results            What We Did…                        manufactured topsoil (CMT)
                in all fourteen TxDOT districts                                               that contained 75% composted
                                                             A comprehensive literature
                in which compost was applied.                                                 manures or composted biosolids
                                                          review was conducted to iden-
                However, in spite of the ap-                                                  mixed with 25% either sandy
                parent successful application                                                 soil or clay soil, and erosion
                                                           • Constituents and composi-
                of compost to slopes and other                                                control compost (ECC) that con-
                                                             tion of various types of
                vegetated areas of highway                                                    tained 50% composted manure
                                                                                              or composted biosolids and 50%
                                                                                              wood chips were evaluated.
                                                                                                 The characteristics of the

                                                                                              leachate produced during “first-
                                                                                              flush” and “extended” column
                                                                                              studies were analyzed to assess
                                                                                              the degree to which stormwater
                                                                                              runoff would leach nutrients,
                                                                                              metals and other constituents
                                                                                              from the CMT and ECC. The
                                                                                              capacity of the CMT and ECC
                                                                                              to retain pollutants in highway
                                                                                              stormwater runoff also was de-
                                      Figure 1: Overall experimental setup                    termined. The onset of runoff

                 Project Summary Report 0-4403-S                              –1–
                                          gravel (0.125 to 0.5 in. diameter). A       and to provide drainage of the leachate.
                                          50 mil filter fabric separated the 3 in.     A channel that was 3 ft wide and 1 ft
                                          layer of soil, CMT, or ECC, from the        long allowed for collection of surface
                                          pea gravel (Figure 2). A spray nozzle       runoff and leachate. The slope of the
                                          was positioned above each column.           channel could be varied from 2:1 to 8:1
                                             The types of CMT, ECC and soils          (horizontal to vertical).
                                          used in the column studies are pre-            Tap water was applied to the channel
                                          sented in Table 1, which also illustrates   that was positioned at the desired slope
                                          the experimental matrix. Duplicate          until the test sample was saturated with
                                          columns were operated for each of the       water. Leachate was allowed to drain
                                          CMT and ECC. Two columns, one               freely from the soil, CMT, or ECC for
                                          each for the sandy soil and the clay        24 hours. The erosion control test was
                                          soil, were used as controls.                begun after waiting 24 hours by apply-
                                             The application rate was approxi-        ing a volume of water to the sample in
                                          mately 3.45 in. of simulated rainfall.      the erosion control channel to simulate
                                          The “extended” column studies con-          the 2 year, 3 hour design storm (ap-
Figure 2: Details of columns with         sisted of applying a volume of deion-       proximately 2.64 in.)
 gravel layers and spray nozzles          ized water to each column to simulate
                                          one year of rainfall in Austin, TX. The     What We Found…
and peak rate of runoff from CMT and      collected leachate was analyzed for            The proposed requirements of
ECC were monitored in channel stud-       total suspended solids, total dissolved     TxDOT Specification Item 161 are
ies at slopes of 2:1, 3:1, 5:1, and 8:1   solids, copper, zinc, total nitrogen,       consistent with compost specifications
(horizontal:vertical).                    ammonia nitrogen, nitrites, nitrates,       applied in some 50 states. Composted
                                          total and dissolved phosphorus, fecal       biosolids met all the limits specified
Leachate Studies                          coliform, and fecal enterococci.            in the TxDOT Specification Item 161.
   Sixteen columns were fabricated                                                    However, the composted dairy cattle
for use in the “first flush” and “ex-       Channel Studies
                                             The channels were constructed of         manure, composted poultry litter, and
tended” leachate studies (Figure 1).                                                  the composted feedlot manure failed
The columns consist of 12 in. long,       galvanized sheet metal and are 3 ft
                                          wide by 9 ft long and 0.5 ft deep (Fig-     to meet the specifications in at least
8 in. diameter acrylic cylinders. Each                                                one category.
column contained a 3 in. base layer of    ure 3). The soil bed was 3 ft wide by 8
                                          ft long. A layer of gravel was placed          Addition of compost to sandy soil
washed gravel (0.5 to 1.5 in. diameter)                                               and to sandy clay loam increased the
overlaid by a 3 in. layer of washed pea   to support the CMT or ECC or the soil
                                                                                      pore size, the range of pore sizes, and

                     Table 1: Matrix for Evaluating Characteristics of Leachate from Compost-
                     Manufactured Topsoil Using De-Ionized Water and Actual Highway Runoff
                                     Compost-Manufactured           Erosion Control       Controls
                                        Topsoil (CMT)
                      Type of 25% compost 25% compost 50% compost                      100%      100%
                                    +             +             +                      sandy      clay
                      Compost 75% sandy soil 75% clay soil 50% wood chips               soil      soil
                                                                                         X         X
                     Dairy                X              X                 X
                     Poultry              X              X                 X
                     Feedlot              X              X                 X
                     Biosolids            X              X                 X

   Project Summary Report 0-4403-S                           –2–
                                    (a)                                            (b)
            Figure 3: (a) Channel illustrating effluent launder, and (b) Channel in wooden support
           and frame to adjust slope. Effluent flow measurement device is located in the white box.

the porosity of the CMT. The bulk          from application of the same compost          the TxDOT Specification 161 organic
density of the CMT and ECC decreased       or CMT or ECC under field conditions           content of 25% to 65%. The organic
compared with the soil controls. The       where water passing through the com-          bulking material also would provide a
water-holding capacity of the sandy        post-amended soils would infiltrate            source of carbon which upon aerobic
CMT increased but the water-holding        into the underlying soil and be taken         decomposition will be converted to
capacity of the clay CMT decreased         up by plants and/or undergo chemical          carbon dioxide and tend to reduce the
compared to the soil controls.             and biological transformations in the         pH to less than 8.5.
   The water-holding capacity of the       soil, resulting in lower concentrations           Increasing the amount of organic
compost-amended soils increased com-       that would reach surface and ground           bulking material in composting poultry
pared to the soil controls. The gains in   water sources.                                litter would have a similar effect on the
water-holding capacity occurred only          The highest peak runoff occurred           pH of the final product.
with compost amendment of sandy            in the erosion control studies at the             Composted feedlot manure is not
soils. The available water capacity        steepest slope (2:1) for the clay control     suitable for use in CMT or in ECC
appeared to increase with compost          and the dairy clay CMT blend. The             because the composted feedlot manure
amendment of sandy soils but appeared      peak runoff rate generally decreased          exceeded the specified maximum pH
to decrease with compost amendment         with decreasing slope for the control,        and salt limit, had a low maturity, and
of clay soils.                             CMT, and ECC. The onset of runoff             exhibited phytotoxicity that would in-
   The leachate collected in the “ex-      for CMT and ECC at all slopes was             hibit the establishment of vegetation on
tended” column studies approximate         delayed. ECC blends appeared to delay         rights-of-way of new highways.
concentrations of constituents in the      runoff more than CMT blends. The                  Clay or sandy clay are the soils of
leachate over time after numerous          clay CMT blends delayed the onset of          choice to be blended with composted
applications of water. Total nitrogen      runoff compared to clay soil alone at         manures and biosolids in Compost
concentrations decrease in total nitro-    a 3:1 slope. The onset of runoff was          Manufactured Topsoils. The clay
gen in the leachate over time for all      delayed 8 to 15 minutes, and the peak         CMTs are more efficient in the removal
CMT and ECC blends. Phosphorus             runoff flow rate was reduced from 0.5          of total nitrogen, phosphorus, total sus-
concentrations decreased over time for     to 0.4 gpm or less. ECC blends delayed        pended solids, and heavy metals than
all CMT and ECC mixtures. The total        the onset of runoff at a 3:1 slope by 15      sand CMTs.
phosphorous concentration after 12         minutes or more.                                  The maximum slope for the ap-
months of equivalent rainfall was less                                                   plication of Compost Manufactured
than 2 mg/L for clay CMT blends and        The Researchers                               Topsoil or Erosion Control Compost is
<10 mg/L for sand CMT blends and           Recommend...                                  3:1 (horizontal:vertical). Runoff delay
ECC blends. Concentrations of copper                                                     and reduction in the peak flow rate are
and zinc also decreased over time. Clay       Wood chips, yard trimmings, or             enhanced at slopes below 3:1.
CMT retained more copper than sand         similar materials should be incorpo-
CMT, but the reverse was true for zinc.    rated as organic bulking agents when
The concentrations of constituents in      composting dairy cattle manure in
the leachate observed in the laboratory    order to increase the organic matter
are more concentrated than the leachate    content of the finished compost to meet

   Project Summary Report 0-4403-S                          –3–
      For More Details...
     Research Supervisor:    Joseph Malina, Ph.D., P.E., (512) 471-4614
     TxDOT Project Director: Barrie Cogburn, P.E., (512) 416-3086

     The research is documented in the following reports:

     0-4403-1 A Review and Evaluation of Literature Pertaining to Compost Characteristics and to the
            Application of Compost Alone and Mixed with Different Soils July 2002
     0-4403-2 Characteristics of Composts: Moisture Holding and Water Quality Improvement August 2003

     To obtain copies of a report: CTR Library, Center for Transportation Research,
                                (512) 232-3138, email:

                                                            TxDOT Implementation Status
                                                                   February 2004
       The research investigated the moisture holding and water quality characteristics of compost. The research
    revealed that the application of compost manufactured topsoil and erosion control compost to TxDOT ROW
    is effective in enhancing the growth of vegetation, controlling erosion, and attenuating the transport of
    constituents of runoff. The research results will be used to promote, demonstrate, and implement the use of
    compost in highway projects.
       For more information, contact: Sharon Barta, P.E., RTI Research Engineer, at (512) 465-7403 or email:
                                                               Your Involvement Is Welcome!
         This research was performed in cooperation with the Texas Department of Transportation and the U. S.
Department of Transportation, Federal Highway Administration. The contents of this report reflect the views of the
authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily
reflect the official view or policies of the FHWA or TxDOT. This report does not constitute a standard, specification,
or regulation, nor is it intended for construction, bidding, or permit purposes. Trade names were used solely for
information and not for product endorsement. The engineer in charge was Dr. Joseph Malina, P.E. (Texas No. 30998).

                                          The University of Texas at Austin
                                          Center for Transportation Research Library
 Center for                               3208 Red River #115
 Transportation Research
      The University of Texas at Austin
                                          Austin, TX 78705-2650

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