EPA-530/SW-21D-73-009
                  GAINESVILLE  COMPOST  PLANT

 FINAL REPORT ON A SOLID WASTE MANAGEMENT DEMONSTRATION

                  VOLUME lj GENERAL REPORT

               VOLUME  II, TECHNICAL EVALUATION
        This final report  (SW-21d)  on work performed under
Federal  solid waste management demonstration grant no.  D01-UI-00030,,
      to the Gainesville Municipal Waste Conversion Authority3
 was prepared jointly  by the GAINESVILLE MUNICIPAL WASTE CONVERSION
        AUTHORITY, INC., and ENVIRONMENTAL ENGINEERING, INC.,
          and is reproduoed as received from the grantee.
               U.S. ENVIRONMENTAL PROTECTION AGENCY
                              1973

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BIBLIOGRAPHIC DATA !• Report No. 2.
SHEET EPA-530/SW-21D-73-009
4. Title and Subtitle
Gainesville Compost Plant; Final Report on a Solid Waste
Management Demonstration. Volumes I and II.
7. Author(s) Gainesville Municipal Waste Conversion Authority,
Inc., and Environmental Engineering, Inc.
9. Performing Organization Name and Address
Gainesville Municipal Waste Conversion Authority £ ^ c- ;
Gainesville, Florida 32601
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
Office of Solid Waste Management Programs
Washington, B.C. 20460
3. Recipient's Accession No.
5- Report Date i
1973
6.
8. Performing Organization Kept.
No.
10. Project/Task/Work Unit No.
1 10S@(8OQ{ /Grant No.
D01-UI-00030
13. Type of Report & Period
Covered
Final
14.
15. Supplementary Notes
 16. Abstracts

  This report  summarizes a technical and economic evaluation of the Gainesville,
  Florida, Compost Plant which  operated from 1968 to  1971.   The plant had  a capacity
  of 150  tons  of municipal solid waste per day.  Paper was  hand separated  and iron
  was electromagnetically separated.  Raw or digested sewage sludges were  mixed with
  the solid waste prior to the  6-day aerobic digestion process.  The compost product
  was not marketable, which upset  the anticipated economic  picture.  The local citizens
  became  disenchanted with the  ability of the plant to meet their solid waste disposal
  needs and the  plant was subsequently closed.  The project's interim reports referenced
  as Nos. 4, 5,  and 6 have not  been published and are not available to the public.  The
  information  in those reports  has been summarized in this  final report.
 17. Key Words and Document Analysis.  17a. Descriptors

  *Refuse disposal, *Composts, Sludge disposal, Magnetic separators, Grinding,  Baling,
  Equipment,  Sampling, Bacteria,  Costs
 17b. Identifiers /Open-Ended Terms
17c. COSATI Field/Group
13B
18. Availability Statement

            Release  to public
FORM NTIS-35 (REV. 3-72)
                                  19. Security Class (This
                                    Report)
                                  	UNCLASSIFIED
                                                        20. Security Class (This
                                                           Page
                                                        	UNCLASSIFIED
21. No. of Pages
                                                       22. Price ,



                                                       USCOMM/OC 14952-P72
            T

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This report has been reviewed by the U.S. Environmental
Protection Agency and approved for publication.  Approval
does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection
Agency, nor does mention of commercial products constitute
endorsement or recommendation for use by the U.S. Government.
An environmental protection publication (SW~21d) in the
solid waste management series.
                          -ii-

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                           CONCLUSIONS





1.  A decision to utilize any composting system as a means of



    waste treatment must depend on assured markets for compost



    and salvage materials.



2.  The plant as originally designed was inadequate in the follow-



    ing respects:



    a.   Belt widths of all conveyors were too narrow.



    b.   No dust control system and inadequate floor drainage.



    c.   The receiving area under roof was too small.



    d.   The receiving area should not have a ramp approach.



    e.   The welding shop was poorly ventilated and the resulting



        fumes were a hazard to workers on the control console.



    f.   The electric motors on both primary grinders were too



        small (600 h.p. is the minimum requirement).



    g.   The refuse receiving and compost discharging activities



        both being located in the same area caused congestion.



    h.   Inadequate space for curing compost.



    i.   The picking platform was located too close to the



        primary shredder resulting in hazards from dust, noise,



        and projectiles.



    j.   The feed mechanism of the Williams primary shredder was



        too low resulting in some refuse being projected out of



        the feed hopper.
                              -111-

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    k.  Facilities for mixing refuse with sewage sludge were
        inadequate.
3.  Refuse can be composted with sewage sludge without any
    unmanageable problems.
4.  The potential for composting quantities of refuse and sewage
    sludge derived from equivalent populations was shown.
5.  Windrow curing of digested compost is necessary to insure
    compost stability in contemporary uses.
6.  Storage of compost in large piles does not bring about curing.
7.  Three days of digestion is probably sufficient time to kill
    most pathogenic microorganisms in waste which was subjected
    to the heat normally generated in the digesters.
8.  Projected costs to make compost saleable to the small consumer
    show a poor economic outlook.
9.  The present state-of-the-art of solid waste analysis is
    inadequate for effective process control and evaluation.
    a.  There is no satisfactory method for the determination of
        putrescible matter in solid wastes.
    b.  There is no method which is conclusive and convenient
        for the determination of the public health quality of
        compost or solid waste.
    c.  Elaborate instrumentation is neither necessary nor
                              -iv-

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         desirable for process control and evaluation of composting



         on an industrial scale.



10.  The cost of composting is competitive with incineration.



11.  Composting has a rightful place in contemporary solid waste



     management, but its full potential has yet to be manifested.
                                -v-

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                         RECOMMENDATIONS





1.  Land reclamation by the application of large quantities of



    crude grade compost should be investigated for the ultimate



    disposal of compost.



2.  The investigation of composting should be continued with



    particular emphasis on salvage of waste components and other



    aspects of resource recycling and the supplementation of



    refuse with additional organic wastes.



3.  Equipment should be developed for mixing of refuse and sewage



    sludge to assure maximum utilization of sludge.



4.  The design and construction of future compost plants should



    take into consideration all means to overcome the shortcomings



    in plant design and operation manifested by this demonstration.
                              -vi-

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                       TABLE OF CONTENTS

                                                             Page No.
  I.   Introduction                                               1
 II.   Objectives                                                 6
III.   Plant Design                                               7
         A.  Design Factors                                      7
         B.  Time Schedule                                       9
 IV.   Detailed Description of Plant                             10
         A.  Site                                               10
         B.  Buildings                                          10
         C.  Receiving System                                   13
               1.   Truck Scale                                  13
               2.   Receiving Hopper and Apron Conveyor          19
               3.   Control Console                              19
               4.   Oscillating Conveyor                         23
               5.   Sorting Conveyor                             24
               6.   Sorting Platform                             24
         D.   Paper Salvage System                                26
               1.   Collector Conveyor System                    26
               2.   Baler                                         27
         E.   Grinding  System                                    29
               1.   Crusher Disintegrator                        29
               2.   Ballistic Separator                          31
               3.   Oscillating Conveyor                          34
               4.   Primary Grinder                               35
               5.   Electromagnet                                 36
               6.   Secondary Grinder                             36
                               -vi i-

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                                                                    Page No.




       F.  Sludge Handling System                                     37



             1.  Mixing Screws                                        37



             2.  Sludge Tank                                          39



             3.  Sludge Pump                                          39



             4.  Automatic Moisture Sensor                            43



             5.  Aeration System                                      43



             6.  Transfer Belt                                        44



       G.  Digester System                                            44



             1.  Electromagnet                                        44



             2.  Tripper Belt Conveyor                                44



             3.  Tripper with Shuttle Conveyor (Early Version)        47



             4.  Tripper with Shuttle Conveyor (Late Version)         49



             5.  Digester Tanks                                       49



             6.  Air System                                           51



             7.  Agi Loader                                           52



             8.  Transfer Car                                         55



       H.  Finishing System                                           56



             1.  Discharge Conveyor System                            56



             2.  Final Grind Mills                                    57



             3.  Stockpiling                                          59



       I.  Machinery and Equipment Specifications                     59



V.  Construction and Costs of Plant                                   65



       A.  Construction                                               65



       B.  Cost of Plant and Equipment                                65
                              -viii-

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                                                           Page No.
  VI.  Training and Early Operation                          68
         A.  Preliminary Equipment Testing                   68
         B.  Personnel                                       68
         C.  Personnel Requirements                          69
 VII.  Performance of Equipment                              71
VIII.  Operational Procedures and Data                       84
         A.  Procedures for Receiving Daily Refuse           84
         B.  Materials Data                                  84
  IX.  Operating Costs                                       87
   X.  Paper and Compost Sales                               92
                                -ix-

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                        I.   INTRODUCTION


        Refuse  disposal has  become an acute problem in the United

States  in recent years.  The  present per capita generation of

refuse  is about five pounds per  day.*  The urban sprawl  has made

the  availability of low cost  sanitary fill sites limited.   Incin-

eration has been relied on  heavily in urban areas for many years,

but  creates severe  air pollution problems and has a high operat-

ing  cost. These disposal problems,  together with the demand for

increased agricultural production suggest the desirability of

adopting  a refuse reclamation procedure as a partial solution to

both problems.  High-rate composting in municipal plants offers

the  most  potential  return of  the reclamation systems now available.

        Composting has  been  practiced in Europe and Asia  for centuries,

In both areas  intensive  cultivation  is  practiced, which  requires

the  maintenance of  soil  quality  by adding as much organic matter to

the  soil  as is possible.  Thus,  a ready market for compost exists.

In this country, with  extensive  cultivation practice and a well

established regime  of  chemical fertilization,  compost has  not found

any  appreciable market.

        To date, most municipal composting operatins in the United

States  have ended in failure.  The primary reason for this failure
       *Note from the publisher, the U.S. Environmental Protection
Agency:  According to the 1968 national survey of community solid
waste practices, conducted by the Federal solid waste management
program, 5.3 pounds per person per day was the figure for wastes
collected.  The amount generated per capita was calculated to be
over 10 pounds per day from residential, commercial, institutional,
and industrial sources.

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has been the attempt by the composters to approach composting as a
profit-making operation without adequate support from the muni-
cipality in the form of dumping fees.  Sufficient background has
been developed to indicate that, with the current market for
compost, this approach is totally impractical.  Still, composting
does offer the potential of a nuisance-free, medium cost refuse
disposal system for municipal use, provided that the facilities
are properly designed and operated, and that financing is adequate.
       Few municipal and public health officials or consulting
engineers will recommend composting as a means of municipal refuse
disposal for many of the reasons just stated.  It is desirable,
then, to establish municipal scale composting facilities in suffi-
cient numbers to obtain reliable technical and economic data on
the construction and operating costs.  These data will permit
adequate public appraisal of this system of refuse disposal.  Pilot
plant operation will not suffice because, in the case of most pilot
plants, no binding contract or responsibility for maintaining a
day-to-day disposal facility exists.  Thus, if mechanical diffi-
culties or market depressions occur, the plant can be "temporarily"
turned off and the refuse diverted to other locations until either
the facility is operable or the market improves.  For general
acceptance of refuse composting in the United States it will be
necessary for compost operators to provide a continuous nuisance-
free municipal service.  This can best be accomplished through the
construction and operation of demonstration compost plants.
                              -2-

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       The Metro Waste Conversion System was developed as a new



approach  to the solid waste  disposal problem, treating solid waste



as a natural resource to be  recycled into channels of commerce,



agriculture, and trade.  The system was  first developed as a



pilot plant in Largo, Florida, which had a daily capacity of about



40 tons per day.  The operation of this  plant for two years sug-



gested technical and economic feasibility of composting on a



larger scale.  The plant at  Gainesville  was built on the basis of



experience gained in Largo and was intended to broadly demonstrate



technical and economic feasibility by satisfactory and continuous



operation.  Another plant of the Largo type was constructed in



Houston, Texas, and put into operation in January, 1967.  It has



a daily input capacity of 360 tons.



       Prior to the construction of the  Gainesville plant, the



local communities had been using poorly  managed methods for the



ultimate disposal of solid wastes.  The  City of Gainesville burned



yard trash and tree trimmings at a dump  and buried refuse and



garbage in a landfill.  The  County of Alachua intermittently



used the city landfill or their own designated dumps.  The Univ-



ersity of Florida managed their wastes by means of a transfer



station and a three acre sanitary landfill, which was rapidly



being filled to capacity.  Thus, there was a strong local need



for an alternative and more  satisfactory process for the ultimate



disposal of solid wastes.
                              -3-

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       In addition, the University of Florida, Departments o£



Environmental Engineering and Soils was interested in cooperating



with the then proposed compost plant in furtherance of their



teaching and research obligations.  The Soils Department relied



on the plant as a source of compost for their research on soil



amendments.  The Environmental Engineering Department assigned



an entomology student to a. fly and pest control study at the



plant.  In addition, classes made frequent field trips to the



plant.



       To be an eligible recipient of Federal funds, the Gaines-



ville Municipal Waste Conversion Authority, Inc. was formed under



a not-for-profit certificate of incorporation issued by the Sec-



retary of State of Florida.  Purposes of the Authority as set



forth in its Certificate of Incorporation include the disposal



of garbage, trash and sewage wasted generated in the City of



Gainesville, other communities, and educational and other public



institutions, and to pursue a program on continuing testing,



experimenting and study to develop the most efficient, sanitary



and nuisance-free methods, processes, equipment, procedures and



techniques to accomplish effective, sanitary composting processes



of municipal waste and producing a compost end product of maxi-



mum benefit and value for agricultural and horticultural uses



and applications; also, to carry on testing, experimenting and



study programs to demonstrate effective and satisfactory methods,



standards and principles for efficient operation of compost plants,
                               -4-

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        The Gainesville  Municipal Waste  Conversion Authority was



 governed by a board of  seven trustees.   One trustee represented



 each of the three  Public Participants in the program -  the  City



 of Gainesville,  the County of Alachua,  and the University of



 Florida.   A fourth trustee was  designated by the  first  three



 trustees  to represent the Public Participants in  general.   The



 three remaining  trustees represented Metropolitan Waste Conver-



 sion Corporation,  whose process  was  demonstrated.



        Two-thirds  of the plant  construction costs were  derived



 from the  U.  S. Public Health Service.   The remaining one-third of



 construction costs were derived from the  sale of  first  mortgage



 revenue bonds  in the amount of  $530,000.   These bonds yielding



 6  1/2 percent  interest  were sold through  Francis  I.  duPont  and



 Company.   The bonds mature at the rate  of $25,000  per year  from



 1970  - 1990.  Funds to  repay the principal and interest were derived



 from the  sale of compost and salvaged materials.   Salvaged paper



 provided  the most  funds.   It was sold in  the Jacksonville area



 for  a price ranging from $9  - 19 per ton.   It was  initially



 anticipated that the sale  of ferrous metals consisting mainly of



 tin cans would yield appreciable money.    This did not materialize,



however, because no local market exists.   Shipment of ferrous



metals  to  Birmingham, Alabama, the closest market, prohibited



economic metal recycling.  The sale of  compost yielded  some money,



but it was much less than anticipated.
                             -5-

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                        II.  OBJECTIVES





       The primary objective was to demonstrate the reliability,



suitability and technical and economic feasibility of the Metro-



politan system, as an example of a high-rate composting system,



for the treatment of refuse and raw domestic sewage sludge,



       Other objectives were:



       1.  To demonstrate effective occupational health, sanita-



tion, and pest control practices suitable for composting processes



in particular and solid waste management in general.



       2.  To demonstrate the production of a compost product



which is nuisance-free and meets or exceeds public health require-



ments, even though it was derived from refuse supplemented with



raw sewage sludge.



       3.  To demonstrate the quality of equipment utilized in the



Metropolitan composting system including effectiveness, efficiency,



economy, and required maintenance.



       4.  To demonstrate the capability of a high-rate composting



plant for treating refuse supplemented with raw sewage sludge in



the same proportion that both wastes are produced by a municipality.



       5.  To provide an effective teaching and research facility



to be used by the University of Florida.



       6.  To provide compost of various qualities for research



into its effect on soils and plants.

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                        III.  PLANT DESIGN





A.  DESIGN FACTORS



       The design of the Gainesville plant was based on experience



obtained at the Metropolitan Waste Conversion Corporation pilot



plant located at Largo, Florida.  The design of a large commercial



plant located in Houston, Texas was also based on the Largo pilot



plant.  The construction of the Houston plant preceeded the Gaines-



ville plant and the additional experience gained in building the



former facility was passed on to the latter one.  Composting is



accomplished in batch loaded, forceably aerated, mechanically



agitated digesters to encourage high-rate waste stabilization.



Tne system is designed to accept all refuse normally collected by



municipalities with the exception of bulky and demolition wastes.



There are provisions for removing salvage materials and non-



compostable materials from the waste stream and for further pro-



cessing of them.  The compostable fraction of waste is shredded



in two stages, moistened with water, sewage sludge or other appro-



priate liquid waste and subsequently digested to a partially stable,



nuisance-free material commonly called compost, which may be used



as a soil conditioner.  The system incorporates modern, efficient



materials-handling processes throughout.  The Gainesville plant



was designed to compost refuse and sewage sludge derived from a



community having a population of about 70,000.
                              -7-

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       Based on these general objectives, specific design criteria
were adopted as follows:
       1.  Overall capacity:  150 tons per day.
       2.  Operating capacity:  20 tons per hour.
       3.  Paper extraction:  hand separated and mechanically
           baled.
       4.  Metal extraction:  combination of hand sort, ballistic
           and electromagnetic separation.
       5.  Digester particle size:  approximately one inch by one
           inch.
       6.  Moisture control:  electronic sensing and pump control.
       7.  Digestion period:  six days.
       8.  Digester agitation schedule:  variable, one to three
           times during digestion.
       9.  Digester aeration schedule:  complete flexibility as
           to length of cycle and duration of aeration per cycle.
      10.  Digester temperature and gas content:  measuring and
           recording equipment adequate for evaluation, processing
           and research purposes.
      11.  Final grind particle size:  typical size 1/4", adequate
           for both application in basic "raw" condition and for
           further processing in blending, enriching and granulating
           processes.
      12.  Curing period:  8 weeks or longer in conical shaped piles.
                              -8-

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B.  TIME SCHEDULE



       Approximately eight months were required from the time of



notice of the grant award for completing the organization of the



Authority, selecting a project director, completing the financing



of the non-grant portion of the cost of the plant, completing



the detailed designing of the plant, taking construction bids, and



the letting of contracts.  Construction was begun about March 1,



1967.  It took approximately 12 months for construction, shake-



down and testing of the plant.  While the plant was still in the



course of design, Metropolitan completed the construction of the



Houston plant and placed this plant in regular commercial operation.



After observing this plant in operation, considerable important



information was developed from actual experience and observation



and, where the plant layout and detailed design of the Gainesville



project could benefit, advantage of this additional experience and



knowledge was taken.
                              -9-

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              IV.  DETAILED DESCRIPTION OF PLANT





A.  SITE



       The plant is located on a 5-acre tract of land which was



provided by the City of Gainesville.  This tract is a part of the



sewage treatment plant site of the City, and is located immediately



across a small stream from the sewage treatment plant itself.  A



substantial expansion of the sewage treatment plant has been com-



pleted recently, and a sludge line has been constructed from the



sewage treatment plant for pumping thickened sludge to the compost



plant for disposal in the composting process.  (Figure 1, Vicinity



iMap)





B.  BUILDINGS



       The plant consists of three separate buildings.  A small



building, 72 ft. x 32 ft., houses the office, a two room labora-



tory, and a general-purpose classroom-conference-meeting room.



(Figure 2, Office Building)



       The main plant building, about 30,000 square feet, contains



most of the plant equipment, including that for receiving, pro-



cessing j, digesting and final grinding of the composted refuse.



The Bulk Storage Building is 90 feet long by 76 feet wide by 20



feet high, with a sloping shed roof.  This building covers the



compost truck loading area, and also an area where some compost



can be stockpiled for curing, and where some finished compost



can be stored.
                             -10-

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P16. 1

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    FIGURE 2



Office Building
       -12-

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       All buildings are essentially standard, industrial-type



steel buildings.  The office-laboratory building has an attrac-



tive masonry front.  Figure 3 shows the floorplan and dimensions



of the office building.  Figure 4 shows the dimensions and layout



of the main plant building.  Figures 5 and 6 (original and



revised) show the flow of material through the plant, including



all the various handling and processing systems.





C.  RECEIVING SYSTEM



       1.  Truck Scale (Figure 7)



       The scale is a Toledo Model 2781 motor truck scale of



50-ton capacity having a 60' x 10' platform and the following



equipment:



             a.  Electronic dial and weight printer with nine



             banks of selective numbering devices.



             b.  Card reader to receive pre-punched plastic truck



             identification cards and giving a signal of 4 digits



             for truck identification and 5 digits for tare



             weight to the weight printer and adding machine.



             c.  Adding machine equipped to provide in one opera-



             tion the gross weight, subtract tare weight to give



             net weight,  and having the capability of maintain-



             ing accumulated net subtotals, and to total and



             clear at the will of the operator.   The adding



             machine can be operated together with the card reader



             and the weight printer.





                             -13-

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                                                 RECEIVING HOPPER -
                                                OSCILLATING
                                                      CONVEYOR
                                                  BALER
                                 PICKING TABLE
               WILLIAMS  -'
                PRIMARY'SHREDDER
                               \
SLUDGE TANK
 SLUDGE  PUMP
    WILLIAMS
     SECONDARY
       SHREDDER
>              -
\  \y\>  IN.
   MIXING  SCREWS

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 RECEIVING  HOPPER
OSCILLATING
      CONVEYOR


 BALER
                                           AERATION  BLOWER
                                  •0SGESTER
                                                      FIGS-, e

                                                  FLOW  DIAGRAM  TOR
                                                    RUBBISH  PLANT

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 FIGURE 7




Truck Scale

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        2.   Receiving Hopper and Apron Conveyor (Figures 8 and 9)



        Refuse is  dumped into the receiving hopper which is 66'  long,



 12'  wide  and 12'  -  6" deep.   The capacity of the  hopper is about



 60 tons of refuse.   An apron conveyor located at  the bottom of



 this hopper carries refuse into the oscillating conveyor.   The



 apron conveyor consists of a series of overlapping or interlocking



 apron pans which  make up the bottom of the receiving hopper.  These



 same are  attached successively to three steel chains which are



 driven by a 2 HP  U.  S.  Electrical Motors Varidrive,  giving a var-



 iable conveyor speed of approximately 2 feet to 20 feet per minute.



 The  apron  conveyor  is controlled from the control console.   The



 conveyor,  Model No.  74-6,  was  manufactured by Gulf Machinery



 Company, Safety Harbor,  Florida,  using Link-Belt  Company components.



 The  apron  conveyor  is designed to move the entire receiving hopper



 load.   Speed of the  apron  conveyor can be controlled to drop  up



 to about 20  tons per hour  into the oscillating conveyor.



        5.   Control  Console (Figure 10)



       A control center is stationed on a high platform to  regulate



 the  flow of refuse material  through the plant.  This  control  plat"



 form  is so  located that  the  operator can  oversee  the  entire system.



 The platform is 13'   - 10"  above the plant floor and  is  approxi-



mately 14' x 15' square.   The platform was manufactured on the



site from drawings supplied by Metropolitan.
                             -19-

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             FIGURE 8
Receiving Hopper and Apron Conveyor

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   FIGURE 10
Control Console
       -22-

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       The Control Console consists of a 30' high column on which



a control panel is fastened.  This panel contains start-and-stop



switches for the following equipment:  Apron Conveyor, Oscillating



Conveyor, Sorting Belt, Primary Grinder, Ballistic Separator, Sec-



ondary Grinder, Intermediate Conveyor, two Screw Conveyors, Moyno



Pump, Transfer Conveyor and Tripper Conveyor.  The Sorting Belt



and Apron Conveyors are also equipped with a fast-and-slow speed



switch.  All switches are plainly marked, using red lights to



indicate when the machinery is in operation.  The manufacturer



was McCleery Engineering and Manufacturing Company, Inc., Downers



Grove, Illinois.



       4.  Oscillating Conveyor



       The Oscillating Conveyor receives refuse from the Apron



Conveyor and feeds it to the Sorting Belt Conveyor.  An oscil-



lating conveyor serves to break or loosen packed refuse, and to



move the refuse in a smooth, continuous, uniform flow.  In effect,



it "meters" the amount fed to the sorting conveyor at a material



flow rate of up to 20 tons per hour.  This is accomplished by the



upward and forward oscillating motion of a metal trough mounted



on inclined reactor legs.  A constant stroke eccentric drive pro-



vides a powerful surge-proof conveying action.   The stroke is about



7/8" and the cycle rate is about 200 per minute.   The Oscillating



Conveyor is 20'  long x 5' wide and 18" deep, and is powered by a
                             -23-

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 10  h.p.  motor.   It is  controlled from the  Control Console to



 insure  that  the  proper amount  of refuse  is fed onto the Sorting



 Belt.   This  conveyor is a  coil-mounted type, manufactured by



 Link-Belt  Company,  Chicago.



        5.  Sorting Conveyor



        The refuse  is fed by the  Oscillating Conveyor onto the



 Sorting Conveyor at a  rate of  up to  20 tons per hour.   The Sorting



 Conveyor is  a belt  conveyor 83 feet  long and 5  feet wide,  which



 rises from below the floor level to  the  sorting platform,  at a



 height  of  15 feet.   It is  powered by a 5 h.p. U.  S.  Electrical



 Motors  Co. varidrive giving a  variable conveyor speed ranging  from



 approximately 10 feet  per  minute to  30 feet per minute.   This  unit



 is  also  controlled  from the Control  Console.  The  Sorting Belt,



 Model No.  74-23, was manufactured by Gulf Machinery Company, Safety



 Harbor,  Florida, using Link-Belt  Company components,  and was assem-



 bled at  the Gainesville  site.



       6.  Sorting  Platform (Figure  11)



       The refuse is elevated  to  the Sorting Platform where normally



 six sorters stand on the platform, three on each side of the sorting



 belt.  Drop-out chutes are built  into  the platforms.  As the refuse



passes by on the conveyor belt the sorters manually  remove salvage



 grade waste paper and cardboard,  which are dropped down the chutes.



Textiles and non-ferrous metals can also be removed manually.



Normally, salvageable paper items will total about 4% to 8% of the



input total,  and textiles and non-ferrous items from 1/2% to 1%.





                             -24-

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Paper and cardboard are dropped into separate collector-conveyor
systems which hold about one bale each, and feed automatically
into the baler.  Textiles and non-ferrous metals are sorted into
separate containers.  At the last station, materials which are
non-salvageable and non-compostable (including such items as rubber
hose, tires, broken furniture, mattresses, rugs, large plastic
items, large bulky items, large tree branches, stumps, etc.) are
also manually removed and dropped through chutes into a dump truck,
to be taken to a landfill.  These materials may comprise 10% to
14% of the incoming refuse.  The platform was manufactured by Gulf
Machinery Company, Safety Harbor, Florida, from drawings by Metro-
politan, and was assembled at the plant site.

D.  PAPER SALVAGE SYSTEM
       1.  Collector Conveyor System
       The sorting platform is divided by the sorting belt into
two separate sides.  Each side has three dropout chutes.   These
are arranged in pairs on opposite sides of the platform,  the first
pair feeding the first collector-conveyor, the second pair feeding
the second colleetor-conveyor, and the third pair feeds the non-
compostables directly into a truck.  Normally, one collector-
conveyor will be used for newsprint and other white papers, and
the other for cardboard, corrugated and other kraft type papers.
                              -26-

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       The collector-conveyors run underneath the sorting platform
at right angles to the sorting belt.  These conveyors are about
4 feet below the chutes, creating storage for about 1 1/2 bales
of newsprint or about 1 bale of cardboard.  A common belt con-
veyor  (Baler Conveyor) connects the 2 cross-conveyors with the
baler.  By allowing one collector-conveyor to stand idle while
the other is feeding the baler, only one baler is needed to bale
the two different types of salvage paper. The two collector-
conveyors and the baler conveyor were all manufactured by Gulf
Machinery Company, Safety Harbor, Florida.  The cardboard collector
is Model No. 74-47, the newspaper collector is Model No. 74-42.
Both conveyors are 48 inches wide by 16 feet long.  The Baler
Conveyor is 36 inches wide by 15 feet long, and is Model No. 74-43.
All three conveyors are driven by 1 HP electric motors and have
a belt speed of about 80 feet per minute.
       2.  Baler  (Figure 12)
       The baler for the plant was manufactured by the Maren
Engineering Corporation of South Holland, Illinois.  Its baling
chamber is 60" long by 30" wide by 42" high.   The operating
pressure of 1500 P.S.I, can compress a bale of mixed paper up
to 1,000 Ibs per bale.  The total length of the baler is 18 feet
long and its weight is approximately 7,000 Ibs.
                             -27-

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FIGURE 12



 Baler
     -28-

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E.  GRINDING SYSTEM



       The original plant design included a Model CDM-4824-HD



Crusher Disintegrator made by Centriblast Corporation, a subsidiary



of Joy Manufacturing Company, along with a Ballistic Separator.



This combination did not work in a satisfactory manner; a change



was made in June of 1969.  The change consisted of replacing the



above mentioned items with a new Williams Hammermill, fed by an



additional Oscillating Conveyor, in combination with an electromagnet.



       1.  Crusher-Disintegrator   (Figure 13)



       Prior to the replacement of the Centriblast machine with



the Williams Hammermill, refuse was handled in the following



manner:  After the refuse has passed the sorting area and most of



the salvageable cardboard, paper and other materials have been



manually removed, the remaining refuse is fed directly into a



crusher-disintegrator.



       In the operation of the machine, refuse is force-fed into



the crushing section by "live" top and bottom sections of the feed



hopper.  This system consists of converging upper and lower apron



conveyors, each driven by a 7 1/2 HP gear-motor.  The upper gear-



motor also drives a set of slow-revolving star wheels.  The feed



end is large enough to receive fairly bulky items.  The largest



article handled to date without causing a jam or a major breakdown



was a heavy cardboard box about 30 inches high by 36 inches wide.



Incoming refuse is forced toward the disintegrator section, and is



crushed into a flattened mass about 4 inches thick which passes



through the small discharge opening.






                              -29-

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      FIGURE 13



Crasner--Disintegrator
          -30-

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       At the discharge end the refuse mass is gripped by a slowly



revolving "star" shaft with equally spaced star- shaped rings or



wheels.  Parallel to this shaft is a high speed "disintegrator"



shaft with heavy-duty impactors spaced to rotate between the star



rings on the star shaft.  This shaft is driven by a 300 h.p.



electric motor, and rotates at up to 1,000 RPM.  The shafts are



so arranged that the impactors and star wheels comb through each



other. Both star wheels and impactors make point penetration of



the refuse.  The star acts as an anvil for a secondary tearing



action.  In addition, the close clearance between the impactors



and the star wheel shaft provides a third disintegration effect,



a shearing action.



       The particle size varies with the type of material being



fed into the machine, but for general refuse the average size



discharged is about 3 inches by 3 inches.



       2.  Ballistic Separator  (Figure 14)



       The refuse at this point has passed through the Grinder-



Disintegrator and is discharged at high velocity into the Ballistic



Separator.  The principal of the Ballistic Separator is separation



by momentum of individual materials.  The more dense particles



[mostly metal) will be thrown farther than the lighter particles



(such as paper and compostable material).  The metals and other



neavier materials are ballistically separated on to an upper



discharge belt conveyor which conveys the material to the can con-



veyor.

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     FIGURE 14



Ballistic Separator
       -32 ^

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       The lighter materials that fall nearer the Grinder-



Disintegrator are caught in a hopper which discharges into a



slinger.  This slinger is a high speed belt which accelerates the



heavier materials and gives this heavier material velocity to



provide a second step for ballistic separation, again separating



any heavier materials which are conveyed to the can conveyor.



The speed and angle of slope of the belt was adjusted on the "cut



and try" method to attain optimum separation.  All materials that



are not thrown onto the upper discharge belt conveyor by ballistic



force fall on to the lower discharge belt conveyor and are con-



veyed to the secondary grinder.



       Located at strategic points in the sides of the ballistic



separator are two air inlets and two suction ports where two



blowers using variable speed drives supply air to the inlets and



two blowers (also variable speed) supply suction for the suction



ports.  Paper, plastics and other very light materials are removed



with this air system and blown into a burner, giving efficient



disposal and providing a useful source of heat for processing.



       The ballistic separator is made of 1/4 inch mild steel plate



with abrasive resistant wear plates bolted to the inside wearing



surfaces.  There are two upper access doors near the top of the



separator which are used for ease of maintenance on the Grinder-



Disintegrator.   One large walk-through door is located lower on



the separator just above the lower discharge belt which was used
                              -33-

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for cleaning purposes; also, six glass shop portholes are used in
the sides of the separator for viewing the operation of the sepa-
rator.  This unit was manufactured by Dan B. Vincent, Inc., Tampa,
Florida.  The upper discharge belt was manufactured by Gulf
Machinery Company, Safety Harbor, Florida, their model No. 74-25.
It is driven by a 1 h.p. electric motor (1800 RPM), is 30 inches
wide by 23 feet long, and conveys approximately 0.4 tons per hour
of metal from the ballistic separator to the can conveyor at about
106 feet per minute.
       The slinger is a 30 inch wide high-speed belt traveling at
from 1500 to 3500 feet per minute, and is driven by a 7 1/2 h.p.
motor on a sliding variable-speed motor base having a three-to-one
ratio variable-type motor belt pulley.  It was manufactured by
Stephens-Adamson Corporation, Aurora, Illinois, and modified by
Dan B. Vincent, Inc., Tampa, Florida, to fit the ballistic sepa-
rator.
       Items 1 and 2 described above were removed because of
unsatisfactory service and new equipment installed in its place.
This equipment is described in Items 3 through 5 as follows.

       3.  Oscillating Conveyor
       In the new revised design the primary grinder was offset
to the right of the picking belt with a Link-Belt Type C extra
heavy duty coilmount Oscillating Conveyor receiving the sorted
refuse from the picking belt and feeding the material in a more
                             -34-

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 uniform flow into the new primary grinder.  This conveyor is 12'
 long,  62" wide and 18"  deep.  The unit was complete with a 14,000
 pound  double-arm, positive action 1" stroke drive assembly and run
 with a 10 HP 1200 RPM motor.
        Because of the blow back of material onto the conveyor from
 the  velocity of the hammers in the primary grinder, the sides of
 the  oscillator were raised an additional four feet above the 18"
 depth.   A hood was also installed over the conveyor in order to
 help control dirt and dust.
        4.  Primary Grinder
        The new grinder  is a Williams Model #460, Type K Shredder,
 manufactured by the Williams Patent Crusher Company, St. Louis,
 Missouri.  This machine is very similar to the Williams secondary
 mill in use  since the plant was constructed.  It was selected
 over other mills  because of its past superior performance in
 grinding heterogeneous  materials.  This mill is 91 1/2" long,
 143" wide and 57" high, with a 60" x 54" feed opening.  It weighs
 approximately 33,500 Ibs.  Accessibility into the mill to change
 hammers  is facilitated  by a hydraulic system for opening the cover
 assembly.  This grinder has 30-100 Ib hammers mounted on four
 banks around the  shaft.  The mill is also equipped with double
 cage-bar grates with space openings varying from 4 1/2" x 8" to
 12" x 8".  The  larger size openings will allow large pieces of
metal to escape.  The refuse is reduced to about 4" to 6" particle
                             -35-

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size in preparation for entering the secondary mill.  The shredder
is run by direct drive with a 400 HP U.S. Electric Motor whidi
runs at about 900 RPM.  The rated capacity of this mill is 35 tons
per hour.  The starting equipment for this motor is manufactured
by Square D Company and is similar to the equipment used for
starting the secondary grinder motor.
       5.  Electromagnet
       This unit replaced the Ballistic Separator as a means of
separating ferrous metal from the waste stream.  It is a Model
SE-555 Eriez Electromagnet including a rectifier.  The magnet is
a center pole type, weighing approximately 8500 Ibs.  Overall di-
mensions are 70" x 115" x 38".
       6.  Secondary Grinder
       Since the primary grinder was offset from the original
production line, the Intermediate Belt was also offset.  So beyond
the new magnet an additional conveyor was installed to feed directly
into the secondary grinder.
       The purpose of the secondary grinder is to further reduce
particle size which in turn increases material density, and so
increases digester capacity.  This is accomplished with a hammer
mill type grinder manufactured by Williams Patent Crusher Company
of St. Louis, Missouri.  The model used is a GA-70, with a rated
capacity of 20 tons per hour.  Overall size is 68" wide, 132"
                             -36-

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 long, and  58" high, weighing 19,500 Ibs.  This is also run with a
 direct drive, 400 HP, 1200 RPM U.S. Electric Motor.  The unit
 reduces the material by impact from a set of 30-50 Ib. hammers
 striking the material against breaker plates until it is fine
 enough to pass through the openings of the grates located in the
 lower section of the grinder.  Grate openings can be varied to
 control particle size.  The openings in this grinder are 10 1/2"
 x 3", which reduces particle size to 1" to 2" pieces.

 F.  SLUDGE HANDLING SYSTEM
       1.  Mixing Screws  (Figure 15)
       After the refuse has been discharged from the bottom of
 the secondary grinder, it falls into the mixing screws where two
 counter-rotating ribbon-type screws, placed side by side in a
 common trough, blend the material with the sludge as it is moved
 down the trough.  At this point in the process, the material is
 otherwise too dry for composting and it has been found advanta-
 geous to introduce moisture (which can be either water or sewage
 sludge).  The twin screws mix together the liquid and dry refuse.
The moisture content of the material entering the digesters should
be 50 to 65 percent.  Since mixed refuse normally ranges from 20
to 25 percent moisture, additional liquid must be added to the
shredded refuse prior to composting.   Sludge from the adjacent
City Sewage Treatment Plant is normally used as the moistening
agent.
                             -37-

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  FIGURE 15




Mixing Screws
       -38-

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        The mixing screw and trough were manufactured by Gulf
Machinery Company,  Safety Harbor,  Florida, Model No. 74-29.  The
screws  are 16  inches  in diameter,  and the trough measures  34 inches
wide by 12 feet  long.   Each screw  is  driven by a 3 HP Electric
Motor giving a speed  of 45  RPM.
        2.  Sludge Tank (Figures  16, 17, and 18)
        Sludge  from  the City Sewage Treatment Plant,  adjacent to
the compost  plant,  is  pumped by  the City into a concrete sludge
storage tank,  located near  the grinding and sorting  building of
the compost  plant.  The Sludge Tank is 18 feet by 18 feet  square
by 16 feet deep,  with walls 1 foot thick.  It has a  sloping bottom
to a center  trough, at one  end of  which is the outlet pipe for
the sludge pump.  Use  of the sludge storage tank permits the
compost plant  to  use  sludge at a uniform rate, and at the  same
time it gives  flexibility for maximum surge supply when the plant
is operating at full capacity or none when no refuse is  processed.
The City Sewage Treatment Plant  is able to furnish digested sludge
at about 1.5 percent solids content,  raw sludge at about the same
solids  content, or raw sludge thickened to almost 6 percent solids.
        3.  Sludge Pump
        A "Moyno"  brand "Progressing cavity" pump is used to convey
sludge  from  the tank to the mixing screws.  The pump is manufac-
tured by Robbins Myers, Inc., pump division, Springfield, Ohio,
Model No.  SWG8.   The pump is driven by a 3 HP U.S. Electric
Motors  "Varidrive" unit with a 4 to 1 variable ratio.  This gives
                               -39-

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 FIGURE 16




Sludge Tank
     -40-

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                                                2
                                                h
                                                u)

                                            it
-41-

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-42-

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 an output  ranging  from 10  gallons per minute at  105 RPM to  50
 gallons per minute at  420  RPM.  The original design called  for
 the varidrive unit being controlled by a Honeywell Automatic
 Moisture Sensing device.
       4.   Automatic Moisture Sensor
       The moisture sensing device uses electrical conductivity
 between two electronic sensing electrodes.  These are two metal
 shoes, 1 1/4 inches wide x 4 1/4 inches on center, which are
 mounted on a pivoted arm riding on the surface of the ground
 refuse.  The electrodes comprise one leg of an A.C. bridge  circuit.
 This signal is used to control the variable-speed drive on  the
 Moyno Pump which meters sludge from the tank to  the mixing  screws
 beneath the secondary  grinder.  The pump can also be manually
 controlled, on or  off,  from the Control Console.  The input signal
 from the probes passes  through a recorder which maintains a con-
 tinuous record of  the moisture content of the raw refuse.  The
 entire moisture  control system failed to work properly and it was
 abandoned  in favor of manual control.
       5.  Aeration System
       The  city sewage  sludge in the Sludge Storage Tank is
 aerated by  a positive pressure blower located at the side of the
 sludge tank.  This air  is supplied through nozzles in a pipe
manifold at the bottom of the tank.   This positive pressure
                             -43-

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blower is manufactured by Sutorbilt Corporation, Compton, Calif-



ornia, Model No. 3H.  It is rated at 42 CFM at 2.5 PSI, operates



at 1670 RPM, and is powered by a 3 HP electric motor.



       6.  Transfer Belt



       After having been mixed with sludge, the ground refuse



drops onto a 30" x 26' long conveyor, which conveys it under an



electromagnetic separator and onto a tripper belt where it is



emptied into the digestion tank.  The conveyor was manufactured



by Gulf Machinery Company, Safety Harbor, Florida.  It is driven



by a 2 HP motor which moves the belt at a speed of about 250



feet per minute.







G.  DIGESTER SYSTEM



       1.  Electromagnet  (Figure 19)



       An electromagnet is located at the south end of the diges-



tion tanks just over the end of the Tripper Belt.  This magnet



removes most of the ferrous metals from the ground refuse prior



to its being deposited in the digestion tanks.  The magnet is an



Eriez SE-1300 run with a 3 HP motor.  It has a 30" wide belt.



       2.  Tripper Belt Conveyor   (Figure  20)



       After the refuse passes under the magnetic separator and



the ferrous metal has been removed, it is then carried by the



Tripper Belt Conveyor to the Tripper which unloads the ground
                              .44,

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  FIGURE 19




Electromagnet
      -45-

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      FIGURE 20
Tripper Belt Conveyor
           -46-

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and moistened refuse into the digester tanks  (Metro-Waste Patent



No. 3,323,896).  The tripper belt is 360 feet long by 22 inches



wide.  It moves approximately 450 feet per minute, and is driven



by a 7 1/2 HP gearmotor.  The tripper belt travels the full usable



length of the digester tanks.



       5.  Tripper with Shuttle Conveyor (Early Version)  (Figure  21)



       This companion to the Tripper is positioned at 90° to the



tripper belt conveyor and is designed to discharge the refuse



evenly into the digesters by moving the discharge end to any posi-



tion over either digester.  This is done by manually winching the



shuttle back and forth as required, using a cable-operated winch



system.  The refuse is conveyed on the tripper belt, which carries



it to the tripper, which discharges it onto the shuttle conveyor



belt.  This transfer is accomplished by means of a movable tripper



device which elevates the loaded belt and then passes it succes-



sively over two large reversing idlers.  The material is then



carried by the shuttle conveyor to desired area in the digester



tanks.  The shuttle conveyor was manufactured by Gulf Machinery



Company, Safety Harbor, Florida, Model No. 74-40.  It is powered



by a 1 HP electric motor.  The belt speed is approximately 475



feet per minute.  Due to the length of the Tripper Belt Conveyor,



it is at times possible to load and unload the Digester Tanks at



the same time.
                             -47-

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          FIGURE 21
Tripper with Shuttle Conveyor
               -48-

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        4.  Tripper with Shuttle Conveyor  (Late Version)
        Problems were  encountered with the shuttle on the original
 tripper.  As mentioned,  this shuttle  was positioned 90° to the
 tripper belt and when it was extended to its full length, the
 weight  of the  shuttle was so great it tended to tip the tripper
 off the track.  The shuttle was replaced with one of lighter
 weight  materials.  It was mounted so  as to swivel a full 180°.
        5.  Digester Tanks   (Figure 22)
        There are two  digester tanks 330* long by 20' wide by 9'
 deep in which  the ground refuse is composted.  The walls are con-
 structed of concrete  blocks.  The floor consists of perforated
 plates  made from 20 gal  galvanized steel.  The face of the plate
 is 7 inches wide with a  I 3/8 inch deep channel lock to hold
 each plate in position.  Each panel has rows of staggered air
 slots 1 1/4 inch long on 1 3/4 inch centers, (rows are 3/4" apart)
 and the slots  are extruded to a height of 1/8 inch to 3/16 inch,
 the extrusion being at an angle to partially shield the slot from
 foreign material.  These extrusions provide a total opening in
 the plate of about 14%.  This perforated floor is also rated to
 support a possible loading of 6,000 pounds per square foot.
       River gravel about 1/4" diameter covers the perforated
plates  to a depth of 3" to 4" over the entire floor surface of
the tank.   The perforated floor and rock help to diffuse air
                             -49-

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                                                 ill
                                                 VP
          Qi

          i-i
          '0
          p

          &
-50-

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evenly along the bottoms of the digesters from where  it rises
somewhat uniformly through the composting refuse.  Air is forced
through the air slots on a timed cycle.  The refuse is distri-
buted to the full depth of the tank on top of the gravel for
its digestion.
       6.  Air System
       Air is blown through a system of ducts to a plenum under
the perforated floor by a low pressure centrifugal fan.  There
is one fan for each of the two digesters.  These fans are rated
at 5,000 GEM at a static pressure of 9.0 inches of water.  They
are powered by 15 HP electric motors.  Each motor is controlled
by a timing device which provides five basic time ranges with a
cycle change every 15 minutes.  Each digester is divided laterally
into two sections.  Air is forced alternately into one section
and then the next.  The timing of the aeration cycle is adjusted
to keep an oxygen residual in the refuse ranging from 5-10
percent.  Each digester section is divided into eight 20 ft sub-
sections each served by two air inlets from the main duct work.
Air into one subsection is more or less prevented from moving
into another one by concrete block beneath the perforated floor.
This tends to balance the air supply throughout each digester
section.  The fans were manufactured by Peerless Electric Division
                                -51-

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of H. K. Porter Company, Inc. of Warren, Ohio.  The floor plates
were manufactured by Pennington Manufacturing Company, Addison,
Illinois.
       7.  Agi-Loader  (Figure 23)
       The Agi-Loader has two functions:  1)  to agitate the
composting refuse in the digester tanks, and 2) to unload the
material from the tanks.   The Agi-Loader was designed by Metro-
Waste (Patent No. 3,294,491), and manufactured by Gulf Machinery
Company, Safety Harbor, Florida, Model No. 71-11.  The machine
has two basic parts:  1)  an apron conveyor 19 feet wide by 19
feet long, and 2) a shuttle belt conveyor with folding ends.
The shuttle belt is 24 inches wide by 24 feet long.  It is
driven by a 1 1/2 HP motor and has a belt speed of 260 feet per
minute.  The apron conveyor is driven by a 7 1/2 HP electric
motor and has a constant speed of 25 feet per minute.   Both con-
veyors are mounted on a framework which rolls on rails mounted
on top of the digester tank walls.  The Agi-Loader has two
independent drives to move it on the rails.  The forward feed
drive is used for slowly moving the machine when the apron con-
veyor is agitating or unloading compost.  This drive is a
Boston "Ratiotrol" unit,  manufactured by Boston Gear Works,
Quincy, Massachusetts, Series E. Model SCR.  It consists of a
1 HP B.C. electric motor which is variable in speed but constant
in torque output.  The motor uses a rheostat type control for the
                             -52-

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 FIGURE 23




Agi-Loader

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speed variation.  The 1 HP motor drives a 3600-1 ratio gear reducer.



The working rail speed of the Agi-Loader is from 0.30 inches per



minute to 9.04 inches per minute.



       A second Agi-Loader drive is called the "quick return"



drive.  It is used to move the machine to the end of the digester



tank.  The quick return drive gives a rail speed of 60 feet per



minute and is driven by a 2 HP gear motor.  The apron conveyor



is pivoted at the drive end or top, while the bottom can be raised



or lowered using a cable-operated winch, driven by a 5 HP gear



motor.  During agitation, the apron conveyor is lowered into the



digester until it just clears the gravel at the bottom.  The Agi-



Loader moves slowly forward against the compost with the apron



conveyor lifting the compost out of the digester and carrying it



to the top end of the conveyor where it falls back into the tank.



During agitation the unloading shuttle conveyor is rolled out of



the way so the compost can fall directly back into the tank.



       Agitation aids digestion in several ways:  it breaks up



any air channels in the mass; it relieves a settling or packing



condition which hinders aeration from the floor plenums, it pro-



vides additional mechanical aeration of the composting mass,



and it disperses microorganisms more uniformly through the di-



gesting mass.



       To unload the digester tank using the Agi-Loader, the



same process is used as in agitating except the shuttle conveyor
                             -54-

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is rolled forward to catch the compost falling from the top



end of the apron conveyor.  The shuttle unloading belt then



conveys the compost to the tripper belt where it is carried to



the digester unloading belt.



       The digester tank can be filled at the same time it is



being emptied using the same tripper-belt provided the tripper



is located "upstream" of the Agi-Loader on the tripper belt.



       Unfortunately, in practice, the Agi-Loader could not



unload the digesters as fast as it was designed to do.  This



forced it to be used solely for unloading the digesters.



       8.  Transfer Car



       With an interest in economy, only one Agi-Loader is used



for both digester tanks.  The Agi-Loader can be transferred from



one digester tank to the other by using a Transfer Car System



at the unloading end of the digesters.  The transfer car is a



platform which travels on rails between the digester tanks and is



itself equipped with rails on which the Agi-Loader is positioned



during the transfer operation.



       To move the Agi-Loader from one digester tank to the other,



the apron conveyor must first be raised out of the digester tank.



Then the Agi-Loader is driven on to the transfer car, which moves



by lowering the apron conveyor into the composting material.  The



transfer car is driven by a 3 HP gear motor and has a rail speed



of about 45 feet per minute.
                             -55-

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H.  FINISHING SYSTEM
       1.  Discharge Conveyor System
       After the refuse has been digested, it is discharged
from the tripper conveyor onto the Discharge Unloading Belt.
This belt runs from the tripper conveyor belt underneath the
transfer car rails and discharges onto the Final Grind Feed
Belt.  The Discharge Unloading Belt was manufactured by Gulf
Machinery Company, Safety Harbor, Florida, Model No. 74-34.
It is 24" wide by 35" long and is driven by a 2 HP motor giving
a final belt speed of 250 feet per minute.
       The Final Grind Feed Belt elevates the compost to the
Grinder Feed Screw.  This belt is 24 inches wide by 49 feet
long, and is driven by a 3 HP motor and has a belt speed of
about 250 feet per minute.  The Belt and Grinder Feed Screw
were both manufactured by Gulf Machinery Company, Safety Harbor,
Florida.  The Belt Model No. is 74-35, and the Screw Model No.
is 74-36.  The Grinder Feed Screw is 16 inches in diameter and
24 feet long and is driven by a 3 HP motor at 90 RPM.
       From the Final Grind Screw the compost drops into two
identical Grinder Metering Screws.  Each of these is 12 inches
in diameter and 71/2 feet long, and is driven by a 1 HP motor
giving the screws a speed of 110 RPM.  They were manufactured by
Gulf Machinery Company, Safety Harbor, Florida, Model No. 74-37.
                             -56-

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       Although each final grind mill is rated at 10 tons per



hour, an overflow screw conveyor is provided at the end of the



final grind screw to return the possible overage to the Final



Grind Feed Belt.



       2.  Final Grind Mills   (Figure 24)



       These mills are fed at the top, and the compost is dropped



into a set of fast turning horizontal swing hammers or blades,



which are turned by a vertical main center shaft.  The material



is forced between the hammers and stationary screens which are



3 feet in diameter with 9/16 inch perforation on 3/4 inch centers,



providing an open area of 51 percent, which creates a shearing



action.  These mills are made by Dan B. Vincent, Inc., Tampa,



Florida.  They are about 36 inches in diameter by 30 inch screen



height, and weigh about 8,000 pounds.  They are powered by 150



HP motors, with a shaft speed of about 960 RPM.  As the compost



becomes fine enough, it is discharged through the circular screen



at the periphery.  The regrind mills are in a vertical position



and the discharge is at the bottom.  The finely ground material



is carried by the Grinder Discharge Screw Conveyor to the Stock-



pile Conveyor.  The Grinder Discharge Screw is 24 inches in



diameter by 20 feet long, is driven by a 5 HP motor, and rotates



at about 26 RPM.  It was manufactured by Gulf Machinery, Safety



Harbor, Florida, Model No.  74-28.
                              -57-

-------
    FIGURE 24



Final Grind Mills
      -58-

-------
       5.  Stockpiling   (Figure 25)
       From the Grinder Discharge Screw, the compost drops onto
the Stockpile Conveyor.  This Conveyor is 18 inches wide by 80
feet long, and elevates the compost to about 35 feet above the
ground at the rear of the Bulk Storage Building.  As a pile is
formed under the end of the belt, the end-loader can carry the
compost into the storage building for stockpiling or for out-
loading.  There is a concrete loading ramp in the building for
ease of truck loading.
       The use of the final grinders was discontinued during
the last quarter of 1969 for a number of reasons.  A hole was
cut in the final grind feed screw to let the compost fall to the
ground before it got to the final grinders.  The compost was then
moved to storage areas with the end-loader.

I.  MACHINERY AND EQUIPMENT SPECIFICATIONS
       Appendix A gives a complete breakdown on each piece
of equipment and its specifications.  This shows the equipment
only that was in operation at the close of the grant period.
                             -59-

-------
 FIGURE 25



Stockpiling
      -60-

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    -------
                V.  CONSTRUCTION AND COSTS OF PLANT





A.  CONSTRUCTION



       Construction of the plant began on March 27, 1967, following



a period of approximately three months for receiving bids and re-



working part of the plans.  Construction covered the following



phases:



       1.  Site preparation



       2.  Office building foundations and construction



       3.  Plant building foundations



       4.  Erection of main building



       5.  Construction of digesters



       6.  Plumbing and sheet metal work



       7.  Machinery foundations



       8.  Installation of plant machinery and equipment



       9.  Electrical installations



      10.  Sewage sludge handling facilities



      11.  Scale installation



      12.  Final grading and road installation




B.  COST OF PLANT AND EQUIPMENT



       The plant as originally designed had several changes



before the final grant period came to an end - (December 31, 1969).



The costs outlined below include only the equipment and buildings



as finally used at the end of the operating period.
                              -65-

    -------
1.   Land, land improvements,  and site preparation, including

    site clearing, grading, black top paving, drain tile,

    fence, etc.                               $105,162

2.   Buildings:

    a.  Office and Laboratory                   23,124
    b.  Plant Buildings                        107,455
    c.  Bulk Storage Building                   13,400

3.   Machinery and Equipment:

    a.  Receiving System:
        1.  Truck Scale                         21,972
        2.  Receiving Ramp, Drive               48,640
        3.  Apron Conveyor                      30,745
        4.  Oscillating Conveyor                10,192
        5.  Picking Belt                        13,236
        6.  Picking Platform and Control Tower  25,878

    b.  Paper Salvage System:
        1.  Baler                                8,006
        2.  Conveyor                            10,667

    c.  Grinding System:
        1.  Williams Hammermill (#460-Type K)   30,351
        2.  Oscillating Conveyor                 6,220
        3.  Electromagnet                        7,600
        4.  Transfer Conveyor                   15,039
        5.  Williams Hammermill (GA-70)         21,062

    d.  Sludge Handling System:
        1.  Mixing Screws                        2,981
        2.  Sludge Tank                         12,200
        3.  Sludge Pump                          2,140
        4.  Sludge Blower                          378

    e.  Digester System:
        1.  Tripper Belt Conveyer               13,815
        2.  Tripper - unloading conveyor         3,139
        3.  Digesters and air system            40,535
        4.  Agi-Loader and Transfer Car         39,664
        5.  Conveyors                           13,833
                       -66-

    -------
     £.  Finishing System:
         1.  Final Grinders                          24,992
         2.  Conveyors and Miscellaneous             19,184
         3.  Stockpile Conveyor                       5,242
 4.  Electrical, Plumbing, Heating and
     Air Conditioning                               169,388

 5.  Erection and Installation of Machinery
     and Equipment:

     a.  Supplies and services                       70,910
     b.  Labor and Payroll Expenses                 134,202
     c.  Supervision and Sundry Expenses             58,000

 6.  Front-End Loader                                18,282

 7.  Fork Lift                                        7,106

 8.  Station Wagon                                    3,472

 9.  Tools                                            7,239

10.  Supplies - Baling Wire                           2,355

11.  Office and Laboratory

     a.  Office Equipment and Furnishings             3,155
     b.  Office Supplies                              2,080
     c.  Laboratory Equipment                        11,391
     d.  Laboratory Supplies                          2,939

12.  Consultants

     a.  Engineering, Design and Inspection          67,809
     b.  Technical                                   13,902

13.  General and Administrative Expense              47,150
                                 Total Cost      $1,296,232
                           -67-

    -------
                 VI.   TRAINING AND EARLY OPERATION





A.  PRELIMINARY EQUIPMENT TESTING



       As construction work neared completion and each piece of



machinery was completely installed, it was started up and run. for



a period of time without any load.  This was to insure proper



functioning of all components, including bearings, gears, belts,



mounting, power, etc.  After this initial testing, small quanti-



ties of refuse were brought into the plant, not only to test the



machinery under load, but also to train personnel in the proper



operation of the equipment.  The quantity of refuse for pro-



cessing increased each month from January to March.  By April



1, 1968, most of the problems had been resolved except in the



area of the primary grinder, so it was decided to have the City



deliver their full capacity.  The County started their deliveries



on April 9, 1968 and the University of Florida started delivery



of their solid waste on June 1, 1968.



B.  PERSONNEL TRAINING



       Probably the most critical part of the plant start-up



was in personnel training.  This was one of the reasons for a



prolonged shakedown period.  The plant superintendent had an



extensive training period of approximately six months at Metro-



Waste's Houston, Texas Plant.  He returned to Gainesville in time



for final assembly of machinery and components.
                              -68-

    -------
C.  PERSONNEL REQUIREMENTS
       The original estimate of the number of personnel required
to operate the plant was quite accurate.  The original estimate
of 25 persons was increased to 26, including supervisors and
management-level personnel.  Table A shows personnel positions
and salaries or wages required to operate the plant when it is
processing 150-160 tons of refuse per day.
                             -69-

    -------
                             TABLE A
                 PERSONNEL POSITIONS AND SALARIES


I.  Management and Supervisory (48 hours/week)

      Position                           Monthly Salary*

Project Director                           $1,200.00
Secretary - clerk                             350.00
Clerk                                         110.00
Plant Superintendent                          850.00
Maintenance Foreman                           770.00
Electrician                                   715.00
                       TOTAL               $3,995.00

Average Day**                                 160.00
II.  Hourly Personnel

       Position            Number of Employees         Hourly Wages

Maintenance                        2                       3.15
Welders                            2                       2.95
Front End Loader                   1                       2.00
Console Operator                   1                       1.85
Sorters                            6                   1.60-1.70
Balers                             2                   1.70-2.10
Baler Helper                       1                       1.60
Tripper                            1                       1.70
Finishing Operator                 2                       1.70
Clean-up                           2                       1.60	
                       TOTAL      20                  $1.60 - 3.15

Average Day**                     20                     $355.50

*  Does not include - Insurance, Workmen's Compensation,  etc.  Workers
are provided 2 weeks paid vacations and 6 holidays each year.

** Calculated using 25 days per month, 9 hours per day.
                              -70-

    -------
                VII.  PERFORMANCE OF EQUIPMENT

       Table A summarizes the performance of all major equipment
used at the Gainesville Compost Plant or in conjunction with its
operation.  Most items of equipment as originally installed in
the plant did not perform in a fully satisfactory manner.  Although
this performance was discouraging to project personnel and others
served by the plant, it was not unexpected.  The State of the Art
of composting processes in particular and solid waste handling in
general would indicate this.  Table A shows the corrective action
taken to alleviate the various problems.  This information is use-
ful to persons contemplating the use of specific items which were
evaluated during the course of this demonstration.  In addition,
careful study of this equipment performance report will illucidate
general principles regarding any equipment which might be used for
solid waste processing.
                             -71-

    -------
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    -------
                            VIII.   OPERATIONAL PROCEDURES AND DATA


         A.  PROCEDURES FOR RECEIVING DAILY REFUSE

                Twenty-two city and five county refuse trucks began their

         deliveries at approximately 7 a.m.  each day and continued until

         5:00 p.m. to 5:30 p.m. except on Wednesdays and Saturdays.  On

         Wednesday six city commercial trucks were used and on Saturday

         usually about three were used.   Usually the county did not de-

         liver on Saturdays.  The University of Florida used two trucks

         to deliver one through three loads each day including Saturday.

         The following compilation describes the trucks and wastes.
TRUCK        NUMBER     KIND OF      SIZE OF  REFUSE
OWNERSHIP    OF TRUCKS  TRUCKS       TRUCKS   TYPE
AVERAGE
WASTE DENSITY
lb/yd3
City

City

City

City
City

University

University

County
County
1

3

2

1
15

1

1

4
1
Dump Meter

Dump Meter

Dump Meter

Dump Meter
Rear Loader
Compaction
Compaction

Compaction

Compaction
Open Dump
15 yd.

20 yd.

30 yd.

20 yd.
20 yd.

40 yd.

65 yd.

-
-
Commercial , Industrial
and apartments
Commercial, Industrial
and apartments
Commercial, Industrial
and apartments
Mixed Domestic
Mixed Domestic

Mixed Domestic and
Hospital
Mixed Domestic and
Hospital
Mixed Domestic
Mixed Domestic
322

322

322

322
322

378

378

-
-
         B.  MATERIALS DATA

                The number of trucks and quantity of refuse received  on a

         monthly basis is shown in Table A for the years of 1968 and 1969.

         The quantity of salvaged materials, non-compostables, and compost

         produced is shown in Table B.


                                        -84-

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    -------
                       IX.  OPERATING COSTS





       The operating costs presented in this report include only



the actual cost of operation.   They do not include depreciation.



Because of the prolonged shakedown and the inefficient operation



of the primary grinder during the first year of operation (1968)



costs are given only for the second year (1969).   Costs are



divided into various categories representing the steps in the



total process.  Table A shows the monthly total costs and cost per



ton of processed refuse for the various categories of the total



process during the calendar year of 1969.  Table B shows the



operating costs of major pieces of equipment.



       The "General Administration" category consists of office



expense including salaries of Project Director and Clerk-Secretary.



Consultants fees are not included as these would not be a part of



the operating costs of a conventional compost plant.
                             -87-

    -------
                               TABLE A
                      OPERATING COSTS -  DEPARTMENTS
DSPAJRTWZNT
DELIVERY & RECEIVING:
Tons Processed
Total Cost
Cost/Ton
SALVAGES
Tons Processed
1 Total Co:st
1 Cost/Ton
!
1 GRINDING:
i Tons Processed j
i Total Coat
I Cost/Ton
IKON-COMPOS TABLES:
\ Tons Processed
Total Cost
Cost/ Ton
,
! DIGEST I NG &
1 SLUMS HA.VDLI.VGj
jj Tons Processed
Total Cost
} Gos t/Ton
JFINXSHING: (Rewind insr)
| Tons Processed
Total Cost
Cos t/Ton
YARDS & STORAGES
| Total Cost
F
GENERAL ADM IN IS TRAT TON :
f Total Cost
t
! GENERAL PLANT -
j SUPERVISION •
] Total Cost
jj
! TOTAL OPERATING COST
i Cost/Ton
JANUARY

2,972.4
$ 1,111.26
.38
225.5
$ 1,799.46
7.90
2,233.5
$ 1,777.15
.80
662.0
I 3,581.07
5.40

2,084.9
$ 995.54
.48
1,561.1
$ 1,799.92
1.15
$ 426.30
$ 2,551.32

$ 6,966.42
$21,008.94
7.07
FEBRUARY

2,723.2
1 705.42
.26
215.1
$1,603.29
7.45
2,023.9
1 3,307.02
1.64
620.3
$ 3,260.86
5.21

1,887.8
$1,317.48
.70
1,347.5
$ 1,790.25
1.33
$ 283.74
$2,706.51

$ 7,515.60
$22,490.16
8.26
MARCH

2,917.6
$ 1,382.81
,65
185.0
$ 1,575.14
8.51
2,306.8
$3,383.60
1.47
571.1
$ 3,121.22
5.47

2,161.5
$ 1,726.74
.80
1.4//1.5
$ 2,840.20
1.97
$ 872.29
$ 3,431.13

$ 3,220.92
$?2,109.05
7.5*
APRIL

1,317.6
$ 1,538.89
1,17
173.1
$ 1 , 444 * *-' *
8.33
825.8
$ 2,917,33
3.53
384.4
$ 2,454.20
6.38

759.9
$ 1,040.69
1.37
907.9
$ 1,920.48
2.12
$ 948.79
$ 3,832.02

S 3,630.08
519,726.56
14.97
GENERAL PLANT SUPERVISION:  Includes such items as social security costs,
workmen's compensation, group insurance, and general insurance.

                                    A - 1
                                    -88-

    -------
                               TABLE A  (can't)

                      OPERATING COSTS - DEPARTMENTS
DEPARTMENT
DELIVERY § RECEIVING:
Tons Processed
Total Cost
Cost/Ton
SALVAGE:
Tons Processed
Total Cost
Cost/Ton
GRINDING:
Tons Processed
Total Cost
Cost/Ton
WN-OOMPOSTABLES:
Tons Processed
Total Cost
Cost/Ton
HGESTING §
SLUDGE HANDLING
Tons Processed
Total Cost
Cost/Ton
:INISHING: (Regrinding)
Tons Processed
Total Cost
Cost/Ton
fARDS AND STORAGE:
Total Cost
JENERAL ADMINISTRATION:
Total Cost
JENERAL PLANT -
SUPERVISION:*
Total Cost
TOTAL OPERATING COST
Cost/Ton
MAY
2,042.0
$ 686.74
.34
175.5
$ 1,718.70
9.79
1,407.5
$ 2,953.52
2.10
458.9
$ 2,210.36
4.82
1,407.6
$ 1,308.60
.93
1,150.0
$ 1,565.27
1.36
$ 444.50
$ 2,538.11
\
$ 4,237.10
$ 17,762.90
8.70
JUNE**
1,023.1
$ 885.82
.87
76.5
. $ 1,128.77
14.75
730.2
$ 2,148.54
2.94
216.4
$ 1,943.72
8.98
730.2
$ 1,674.12
2.29
1,494.6
$ 1,344.92
.90
$ 902.95
$ 2,624.79
$ 4,504.69
$ 17,158.32
16.77
JULY
3,239.9
$ 1,104.39
.34
250.2
$ 2,309.93
9.23
2,658.9
$ 2,945.74
1.11
482.9
$ 2,069.63
4.29
2,506.8
$ 1,572.96
.63
1,500.0
$ 3,064.80
2.04
$ ' 651.33
$ 2,577.27
$ 5,152.73
$ 21,448.78
6.62
AUGUST
3,376.1
$ 1,323.83
.39
272.5
$ 1,753.19
6.43
2,604.8
$ 3,893.16
1.49
498.8
$ 3,330.54
6.68
2,604.8
$ 1,567.53
.60
1,613.2
$ 2,663.83
1.65
$ 628.81
$ 2,632.54
$ 4,323.89
$ 22,116.32
6.551
* Includes such items as social security costs, workmen's compensation, group
  insurance and general insurance.

** High June costs due to low intake tonnage and shut-down to change over to
   new primary grinder.
                                      A -  2

                                     -89-

    -------
           TABLE A  (can't)



OPERATING COSTS - DEPARTMENTS
DEPARTMENT
DELIVERY § RECEIVING:
Tons Processed
Total Cost
Cost/Ton
SALVAGE:
Tons Processed
Total Cost
Cost/Ton
GRINDING:
Tons Processed
Total Cost
Cost/Ton
M3N-COMPOSTABLES:
Tons Processed
Toral Cost
j Cost/Ton
DIGESTING §
1 SLUDGE HANDLING:
Tons Processed
Total Cost
Cost/Ton
FINISHING: (Regrinding)
Tons Processed
Total Cost
Cost/Ton
YARDS AND STORAGE:
Total Cost
GENERAL ADMINISTRATION:
Total Cost
GENERAL PLANT
SUPERVISION:
Total Cost
TOTAL OPERATING COST
Cost/Ton
SEPTEMBER
4,067.7
$ 1,549.27
.38
238.1
$ 1,895.48
7.96
3,324.0
$ 3,606.20
1.08
505.6
$ 3,734.32
7.39
3,324.0
$ 1,231.12
.37
2,283.6
$ 2,842.34
1.24
$ 439.97
$ 2,051.54
$ 4,738.96
$ 22,089.20
5.43
OCTOBER
3,498.4
$ 1,839.17
.53
162.1
$ 1,403.61
8.66
2,833.9
$ 5,016.04
1.77
502.4
$ 2,874.01
5.72
2,833.9
$ 6,712.11
2.37
2,059.8
$ 3,634.04
1.76
$ 1,444.40
$ 3,080.46
$ 6,814.11
$ 32,817.95
9.38
NOVEMBER
3,003.4
$ 1,453.67
.48
147.1
$ 1,214.20
8.25
2,369.8
$ 5,743.60
2.42
486.5
$ 2,710.14
5.57
2,369.8
$ 2,707.10
1.14
3,176.0
$ 2,221.93
.70
$ 2,322.05
$ 2,278.01
$ 4,779.61
$25,430.31
8.47
DECEMBER
3,891.1
$ 1,885.45
.48
131.6
$ 1,476.51
11.22
3,193.9
$ 3,850.12
1.21
565.6
$ 3,494.55
6.18
3,193.9
$ 2,652.67
.83
4,264.1
$ 2,677.29
.63
$ 1,124.06
$ 3,179.72
$ 5,756.90
$26,097.27
6.70
                A - 3




                -90-

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    -------
                  X.  PAPER AND CCMPOST SALES

A.  PAPER
       Recycling and marketing of paper was a successful operation
during the first 1 2/3 years of plant operation.  A lot of good
quality newsprint and corrugated paper has been received at the
plant and as a result a good market developed with the gypsum aind
roofing industry.  Bales were made up with a mixture of newsprint
and corrugated with a higher percentage of the latter.  This is
more desirable for the two industries mentioned due to the higher
content of long fibers.  An average price of about $17.50 per ton
was received during this period.  However, from September on to
the end of 1970, the market was depressed due to tight money and
a slow down in the construction industry.  The last price re-
ceived was $19.00 per ton and tonnage purchased was cut back
considerably.  Table A shows paper and compost sales during 1968
and 1969.
B.  CCMPOST
       Most of the compost sales have been in the citrus industry
in bulk form.  This has not been an encouraging picture as only
10% of the compost produced has been sold.  Citrus sales were made
primarily to 32 different grove managers, in amounts ranging from
13 tons to a high of 400 tons, with tonnage per acre varying from
1 1/2 to 38.  The average application was about 3 tons per acre.
                             -92-

    -------


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Transportation, no doubt, was a factor in limiting the amount of
compost sold.  Hauling distances ranged from 90 to 170 miles from
the plant at a cost of from $14.00 to $16.00 per ton delivered
and spread on the groves.  Of the total Customers, four repeated
applications in three consecutive years.  Claims were made by these
growers that:  1) they had an improvement in the cover crop grown,
2) that the juice content of the product grown had increased, 3)
that the yield of fruit per acre had increased, and 4) that it took
less time for fruit to reach maturity.
       A good percentage of the compost produced was donated to
the public participants, mainly the University of Florida, and some
to the City of Gainesville in the development of public parks.
The University has used the compost as a soil builder, mixing it
with sandy soil and amending it with nitrogen, to be used on the
ground where new building projects have been completed.
       Other areas of compost application have been for pine tree
seedlings, truck gardening, and making potting soil blends.  One
such application with pine tree seedlings was carried on with St.
Regis Paper Company in north Florida, where applications were
made in various quantities from 3 to 20 tons per acre.  Their ex-
perience indicated that 10 tons to the acre gave them the best
results with the survival rate of seedlings in the test plots
exceeding those in the control plots.
                             -94-

    -------
       Much research needs to be carried on in developing markets



for compost.  It is planned that as the plant continues to operate,



studies and experiments will be carried on where large quantities



of compost can be utilized.  Two such projects that are planned for



Florida are land reclamation and organic fanning.  Work is already



under way in which 100 acres of virtually sterile soil, due to a



strip mining operation, will be saturated with compost to try



and improve and make the soil productive again.  The other project



is approximately 400 acres of unproductive, sandy farm soil which



will be applied with various tonnages of compost.  The compost



will be plowed into the soil, left to decompose and crops planted



after a year.  It is hoped that the results of these, tests will



develop a future market for compost produced.  At the same time



the theory of total reutilization of solid waste will become a



reality.
                             -95-

    -------
TECHNICAL EVALUATION
    -96-

    -------
                           TABLE OF CONTENTS





                         TECHNICAL EVALUATION



                                                              Page No.



A.  INTRODUCTION                                                 99



B.  FACILITIES AM) EQUIPMENT                                    100



    1.  Laboratory                                              100



    2.  Process Control and Special Studies Equipment           103



    3.  Moisture Sensor                                         103



    4.  Temperature Sensor Probes                               104



    5.  Mobile Instrument Console                               105



C.  METHODS OF SAMPLING                                         107



D.  METHODS FOR CHEMICAL ANALYSES                               108



    1.  Carbon                                                  109



    2.  Nitrogen                                                110



    3.  Phosphorus                                              110



    4.  Potassium                                               111



    5.  Moisture                                                111



    6.  Hydrogen-Ion Concentration                              112



    7.  Volatile Solids                                         112



    8.  Chemical Oxygen Demand                                  113



    9.  Biochemical Oxygen Demand                               113



   10.  Putrescible Matter                                      115



E.  BACTERIOLOGICAL ANALYSES                                    118
                                 -97-

    -------
E.  BACTERIOLOGICAL ANALYSES
      (Continued)
                                                             Page No.
    1.  Coliform Bacteria                                    "
    2.  Salmonella                                             119

    3.  Extrinsic Bacteria                                     119

F.  OCCUPATIONAL HEALTH STUDIES                                123

    1.  Physical Examinations                                  124

    2.  Noise Levels                                           124

    3.  Intestinal Parasites                                   124

    4.  Airborne Particulate Matter                            125

G.  ARTHROPOD AND RODENT CONTROL METHODS                       126

H.  RESULTS                                                    127

    1.  Composition of Refuse as Received at The Plant         127

    2 .  Compos ition of Material Removed by Magnets
    3.  Bulk Density of Refuse as Placed in Digester           133

    4.  Moisture Content of Refuse and Compost                 134

    5.  Sewage Sludge Utilization                              137

    6.  Effect of Sewage Sludge on Refuse Decomposition        145

    7.  Decomposition of Refuse in the Digester                153

    8.  Curing of Compost                                      172

    9.  Bulk Density of Compost in Storage Pile                190

   10 .  Process Evaluation - Miscellaneous                     191

   11.  Arthropod and Rodent Control                           196

   12.  Public Health Aspects of Composting                    218

REFERENCES                                                     237
                                 -98-

    -------
                     TECHNICAL EVALUATION

A.  INTRODUCTION
       The principal objective of the technical program of the
Gainesville Demonstration Project is to provide the technical sip-
port required to demonstrate the satisfactory performance of the
Metro composting system for the treatment of solid wastes from
medium-sized cities.  The specific objectives are to:
       1)  determine what is accomplished by the composting
           process; and
       2)  evaluate the public health aspects of the process.
When these objectives were achieved, recommendations in the form of
revised operating parameters were made to improve the process.  If
the operating parameters were revised, their effect on improving the
process was subsequently evaluated.  Data resulting from the fulfill-
ment of these objectives could be used by:
       1)  the U. S. Public Health Service to evaluate the
           utility of composting as a treatment process to
           partially alleviate the nation-wide solid waste
           problem;
       2)  plant operators in the selection of process control
           parameters to attain more efficient treatment; and
       3)  technical personnel in control and research work
           on solid wastes.
                             -99-

    -------
       During the course of this demonstration project,  the Metro



composting process, as an example of a high-rate composting system,



was evaluated for its utility in the treatment of solid municipal



wastes .



B.  FACILITIES AND EQUIPMENT



       The facilities for conducting the chemical and microbiological



studies associated with this evaluation program include a combination



chemistry and bacteriological laboratory and special in-plant equip-



ment for monitoring several of the factors which influence the compost-



ing process and the quality of the final product.



       1.  Laboratory



             A combination chemistry-bacteriological laboratory is



located on site in the compost plant office building.  This laboratory



has about 360 sq. ft. of floor space and is fully equipped for most of



the chemical analyses and all routine bacteriological studies necessary



for the demonstration and quality control program.  Figure 1 shows a



floor plan of the laboratory and the location of the major pieces of



equipment.  A description of the major laboratory equipment is pre-



sented in Table 1.



             The staffing of the laboratory varied during the dura-



tion of the project.  Initially, it was supervised by a part-time



professional biologist.  He was assisted by a full-time technician



and three part-time graduate students, one each to work on the chemical,
                                 -&0-

    -------
           Item
         TABLE 1

MAJOR LABORATORY EQUIPMENT


              Manufacturer
 1.  Drying Oven

 2.  Analytical blance

 3.  Water Still

 4.  Water bath

 5.  Steam Generator

 6.  Glassware washer

 7.  pH Meter

 8.  Kjeldahl Unit

 9.  Moisture Balance

10.  Induction Furnace

11.  Klett Industrial
      Photometer

12.  Autoclave

13.  Incubators (2)

14.  Mikro-Samplmill



15.  BOD Incubator

16.  Andersen Air Sampler
          Pulverizing Machinery
           Div. Metals Disinte-
           grating Co., Inc.
          Andersen Samplers and
           Consulting Service
Model No.
Precision Thelco
Mettler
Barns te ad
Precision
Amsco
Heinicke
Sargent
Labconco
Ohaus
Leco
t
Klett
Scanlan Morris
Precision Thelco
27
H-15
EMH-5
66634
LB20
HW200S
PL (No. 30008)
20701
6010
521-000

900-3
A-422
4
                              -101-

    -------
                                            VENT
-102-

    -------
bacteriological, and arthropod and rodent control aspects.  Staffing



of the technical evaluation program was continually enlarged until



it included a full-time director who was a professional microbiolegist,



a full-time graduate engineer, a full-time technician, and two half-



time technicians.



       2.  Process Control and Special Studies Equipment



             The compost plant is equipped so that the moisture



content of the ground raw refuse and the temperature of each batch



of compost in the digester tanks are continuously monitored.  In



addition to the continuous monitoring equipment, a special mobile



instrument package was developed by Honeywell, Inc., to measure the



temperature, dew point, 0- content, and CO- content at several levels



anywhere in the digester tank, and also to measure the volume of air



entering a segment of the digester tank.



       3.  Moisture Sensor



             The moisture content of the ground refuse was measured



as a function of the conductivity between two sensing electrodes in



an A.C. bridge circuit.  The signal generated by this circuit is cali-



brated in terms of moisture content and is recorded on a circular



chart recorder.



             The sensing electrodes consist of two metal shoes 1 1/4



inches wide and 4 1/4 inches on center.  These sensors are on a pivoted



arm that rides on the surface of the ground refuse as it is conveyed
                           -103-

    -------
from the mixing screws following the secondary  grinder to the



digester tanks.  The electric signal from these electrodes acti-



vates a variable speed pump which supplies either water or sewage



sludge to the refuse in the mixing screws in order to maintain a



pre-selected moisture content in the ground refuse.  A limit switch



is connected in the circuit so that if no compost is on the conveyor



belt (i.e., the electrodes pivot down to the surface of the conveyor



belt) the pump will not operate.



             The specific components of this system were itemized in



a previous report^ * .



       4.  Temperature Sensor Probes



             As described in a previous section of this report, the



composting process is a batch-type operation with each batch consisting



of the refuse from one day's operation.  This batch is placed in the



digester tank where it remains for a six-day digestion period.  During



the digestion period, except for the short period when the compost is



agitated, the temperature of each batch is continuously monitored



with a copper-constative thermo-couple sensing probe, 24 inches long,



which is inserted horizontally into the pile through an opening in



the digester wall.  The probe is withdrawn when the batch is agitated



and then reinserted immediately upon completion of this operation.



             There are four such temperature probes in each digester,



located at the quarter points of the digester length.  The temperatures
                             -104-

    -------
recorded at the eight locations are recorded on an eight point



strip chart recorder.



             The specific components of this system were itemized



in a previous report^ '.



       5.  Mobile Instrument Console




             A new and unique instrument package has been developed




for the Authority by Honeywell, Inc.  This is a Mobile Instrument




Console package, shown in Figure 2 , which can travel the length of




the west digester tank.  It is equipped with one probe to measure




temperature at five levels, and dew point, CL, and CO,, at four levels




in the compost pile.  A second probe measures temperature only at




five levels.  A third component of the package is a pressure-sensing




unit which can be connected by means of snap-lock fittings to any




of sixteen pitot tubes permanently placed in every other air duct




which supplies air to the west digester tank.  There is also a tap




next to each pitot tube for sampling for dew point and the CL and




CO- content of the air being supplied to the digester tanks.




             The two probes are constructed of 3/4" diameter fiberglas




tubing and have a pointed wooden plug in the bottom end.  Both probes




have thermo-couples at 6", 24", 48", 72", and 90" from the tip of the




probe, and one has gas sampling ports 32", 48", 64",  and 90" from



the tip.
                               -105-

    -------
                                   FIGURE 2
20 Point Strip
  Recorder A --,
            20  Point  Strip
           r~ Recorder  B
   Mobile  Instrument
        Console
1. Compost Temperature
    Recorder A

2. C>2 Analyzer

3. Compost Data Recorder B

4. Suction Pump On-Off
   Switch with Indicator
   Light.

5. C02 Analyzer
6. Inlet Air Volume

7. Signal Transducer for
   converting signal from
   C>2 analyzer.

8. Signal Transducer for
   converting signal from
   dew probe and ambient
   temperature thermo-
   couples .

9. Signal Transducer for
   converting signal from
   C02 analyzer.

        FIGURE 2
Mobile Instrument Console
      Digester Sensing Probes
                                    -106-

    -------
             The instrumentation is arranged so that both probes can
be used to measure temperature concurrently.  The temperature from
each of the ten points is recorded on a 20-point strip chart recorder,
Recorder A.
             The other variables, i.e., inlet air volume, CCL, CL,
dew point temperature, and also ambient temperature, are measured
and recorded on a second 20-point strip chart recorder, Recorder B,
which has a stepping switch to operate solenoid values to route the
sampled gas stream to the appropriate analytical instrument.
             The specific components of the unit are listed in a pre-
vious report *• * .  The cost of this instrument was $15,600 of which
about $12,400 was for hardware and the remainder for developmental
work and fabrication.
C.  METHODS OF SAMPLING
       Sampling of raw ground refuse and compost, particularly for
chemical analyses, was done by compositing grab samples early in the
technical evaluation program.  This led to erratic and misleading
results.  For example, frequently the content of carbon was higher
in raw refuse than in compost.  This is contrary to fact inasmuch as
carbon is expected to diminish as a result of composting.  The
erratic results were therefore attributable to sampling errors,
which in turn are attributable to the extreme heterogeneity of urban
solid waste.
                            -107-

    -------
       An alternative sampling procedure was developed which circum-

                                                           3
vented the problems of grab sampling.  Approximately 0.5 yd  of waste


was mixed as much as possible without reducing particle sizes.  This


usually was done with a shovel or fork.  One half of the waste was


prepared for analysis.  A portion of the remainder was placed in a


bag made of 16 mesh Fiberglas screen.  The bag had an approximate


capacity of 1.5 ft .  The bag was then placed in the digester within


the production quantity of waste for treatment.  Treatment time and


conditions were varied according to need.  The bag of waste was re-


trieved from the digester and prepared for analysis.


       Samples before and after treatment were prepared for analysis


by passing the waste twice through a riffle sampler (also known as


a Jones sampler or sample splitter), having a top opening of 8 x 10 in.


and a chute width of 0.75 in.  The sample thus reduced in size was


dried to constant weight in an 75°C oven.  The sample was ground in


a Mikro-Samplmill to pass a screen having holes of 0.125 in. in diameter.


Subsequently, the sample was reground to pass a screen having rectan-


gular slots of 0.02 in. in width.


D.  METHODS FOR CHEMICAL ANALYSES


       It was anticipated that chemical analyses would be performed


according to the official A.O.A.C. procedures which are commonly used


in the inorganic fertilizer industry.  Subsequently,  the A.P.^.A.


procedures^ •> were used as a basis from which modifications might
                           -108- '-''

    -------
be made.  It was recognized from the onset of this demonstration


that many methods of analyses might have to be modified because


of the pioneering nature of this work.  The following chemical


analyses were performed on compost and refuse during this demon-


stration:  total carbon, total Kjeldahl nitrogen, phosphorus,


potassium, moisture, pH, volatile solids, chemical oxygen demand,


and biochemical oxygen demand.


       1.  Carbon


             The induction furnace combustion method which is a


semi-micro method was used for the estimation of total carbon.  The

           f7")
APWA method^ } was used with the following modifications:


       a)  add a small amount of Alundum to the platinum


           crucible before putting in samples,


       b)  use 1.0 N NaOH in place of 0.4N NaOH absorbing


           solution,


       c)  digest precipitate in water bath at 70°C instead


           of at room temperature,


       d)  use medium porosity glass frit filtering crucibles


           in place of Gooch crucibles, and


       e)  dry precipitate overnight at 75°C instead of 1 hour


           at 105°C.


Toward the end of the demonstration,  Ascarite in small absorption


tubes was used to collect CCL in place of the more cumbersome Ba CO,
                               -109-

    -------
precipitation method.  The results were the same, but the procedure



was simplified.  Analytical precision depends greatly on particle



size of the sample.  Precision ranged 40 +_ 4.7 percent when satrapies



were ground dry in a Waring Blender.  Precision ranged 40 +_ 1.0



percent when samples were ground on the Mikro-Samplmill to pass a



screen having holes of 0.125 in. in diameter.



       2.  Nitrogen



             The K j eldahl-Wi If art h-Gunning method was used for the



determination of organic and ammoniacal nitrogen.  A chromium reduction



procedure for the determination of total nitrogen including nitrate



nitrogen was evaluated.  The effect was an insignificant increase in



nitrogen and therefore the chromium reduction procedure was abandoned


                              T71
in favor of the APWA procedure^ '.  Typical analytical precision of



the analysis of ground compost was 0.38 +_ 0.025 percent; of ground raw



refuse - 0.48 +_ 0.030.



       3.  Phosphorus

                            C7~)

             The APWA method^ J  failed to give good results because



25 ml of concentrated sulfuric acid did not completely digest the



organic matter and color development was not reproducable.  Addition



of mercuric oxide to the acid helped to digest the organic matter,



but this resulted in a precipitate which interfered with the color-



metric determination.



             Complete digestion of organic matter was accomplished



by the following combinations of reagents:  1)  25 ml concentrated
                              -no-

    -------
FLSCL, 15 ml concentrated HNO- as required, and 2)  25 ml concentrated



H2SO. and 2.0 g ICS-CL.  However, when color was developed with molyb-



date and done by the APWA method^- ' , and with  S2C12 by the Standard


                 f 81
Methods procedure^ ' , it was not very reproducable.


                                  T9")
             The Quimonciac Method*- J was very satisfactory for the



determination of phosphate (as orthophosphate) in compost and refuse.



In the evaluation of this method the average of 9 determinations was



0.424 +_ 0.019 percent phosphate.  Recovery of phosphate added to compost



averaged 94.4 percent.



       4.  Potassium
             The A.O.A.C. sodium tetraphenylboron method1- J was satis-



factory for the determination of potassium.  However, it was used on



a very limited basis.



       5.  Moisture



             Moisture in refuse and compost was determined by both


                                        f 71
the oven drying and the infrared methods v } ,  Samples which were to



be analyzed were never subjected to temperatures exceeding 75°C.



Data reported on a dry weight basis was calculated from moisture



values obtained from oven drying subsamples to constant weight at



103°C.



             An Ohaus moisture balance was used for the determination



of moisture in samples taken for process control purposes.  Moisture



values obtained with this instrument were quite reproducible (+ 0.5%),

    -------
and they correlated well with the oven drying procedure.  The heat



intensity at which samples were dried was not critical.  Drying was



rapid and the sample weights equilibrated after 20 minutes when the



power ranged from 105 - 140 watts.  Distance between sample and



the lamp was set at 2 in.  At 80 watts, drying time was prolonged



to 45 inin.  At 160 watts, drying time was reduced to 15 min., but



the sample was scorched.



       6.  Hydrogen-Ion Concentration



             Hydrogen-ion concentrations (pH) were determined by


               f 71
the APWA method^ J .  However, it is not necessary to use CCL-free
                                                           L*


distilled water for suspending the samples if the water is used



within 2 weeks after it has been distilled.  Furthermore, most raw



refuse and compost has considerable buffering capacity.



             For routine work, particularly in the field, pH indicator



paper was usefull and convenient.



       7.  Volatile Solids



             Volatile solids in samples of raw refuse and compost were


                             f 71
determined by the APWA method1- J .  Although there was no reason to



suspect the method for its determination, volatile solids data were



never reliable as an indicator of loss of putrescible matter as a



result of composting.  It would appear that volatile solids data are



an excellent indicator of putrescible matter loss because they approx-



imate organic matter loss.  Apparently, the lack of reliability is



attributable to sampling errors.

    -------
       8.  Chemical Oxygen Demand



             The determination of chemical oxygen demand (COD)  of



solid materials is similar to that of liquids except that a wetting



agent is required to obtain a reasonably uniform suspension of solids



for subsequent sampling and dilution.  The most accurate and precise



results were obtained when using Aquarex (DuPont) as a wetting agent.



A 1.8% solution of this material is made up with distilled water.  A



0.5 g sample of ground compost or refuse is weighed and placed in an



800 ml beaker with a magnetic stirring bar.  Samples were ground with



a Mikro-Samplmill to pass a screen having holes of 0.125 in. in di-



ameter.  One-hundred ml of the 1.8% solution of Aquarex is added and



the mixture is stirred until all the compost is wetted.  This usually



occurs in a minute or so.  Four-hundred ml of distilled water is added



and stirring is continued.  A 10 ml Mohr pipet with the tip enlarged



is used to take the sample.  The sample (10.0 ml) is placed into the



COD flask.  From this point the procedure is the same as that found


                   (81
in Standard Methods^- }.  An equivalent quantity of Aquarex is used



in the blank.  Therefore, subtraction of the COD value of the blank



from the COD value of the sample containing the wetting agent gives



the COD value of the sample only.



       9.  Biochemical Oxygen Demand



             The determination of biochemical oxygen demand (BOD)



of solid materials is similar to that of liquids.  Just as in the
                              -HIS-

    -------
COD determination the solids must be uniformly suspended in a



liquid for accurate sampling and dilution.



             The oven dried waste (5.00 g) is homogenized for 5



minutes with 495 ml of BOD dilution water in a Waring blender.  Raw



ground refuse and compost can be satisfactorily homogenized with the



Waring blender.  It is not necessary to fine grind these materials.



This suspension was subsequently diluted in the same manner as a



liquid waste.  Following this preparation, the analytical procedure



is similar to that described in Standard Methods'- '.  Fresh sewage



is used as seed after storage for 24 - 48 hrs. at 20°C.  It is



filtered through Whatman No. 12 paper to remove suspended solids.



The seed is used at a concentration of 10 ml per liter of suspended



waste.  This high concentration is always desirable, but it is neces-



sary if the waste had been dried previous to analysis.



             The BOD test has many disadvantages even when used for



the analysis of liquids.  The disadvantages are compounded when the



test is used for the analysis of solids.  Among these are the long



incubation period, poor precision, and the fairly involved procedure.



However, the BOD test proved to be the most reliable one for determin-



ing the reduction of putrescible matter resulting from composting.



             The advantage of the BOD test is that it is a measure of



the carbon which is available for biological utilization.  This is



important because composting is a biological degradation process.

    -------
Consequently, the BOD value of raw solid waste is an approximation



of the carbon compounds which could be decomposed by composting.



Also, the BOD value of composted waste is an approximation of



further decomposition potential.  It is this decomposition potential



which leads to odors when an immature compost becomes wet.  The



difference between BOD values before and after composting is a



measure of what was accomplished during composting.



             It appears, therefore, that there is a need for a



method for the determination of carbonaceous matter which can be



utilized by biological systems.



       10.  Putrescible Matter



             One of the more vexing problems facing researchers in



solid waste treatment is the lack of methods for the determination



of biological stability of waste, i.e., its content of putrescible



matter.  Process evaluation at the Gainesville plant and elsewhere



depends on knowing the stability of the waste at various stages of



treatment.  With this knowledge it is possible to determine the



efficiencies of various processes.



             Waste stability at Gainesville was determined by the



following tests:  the standard BOD, the Hach modification of the



BOD, the COD, volatile solids,  and C/N ratio.  None of these tests



was fully satisfactory for various reasons.  This shortcoming usually



necessitated making all analyses on each sample.
                            -115-

    -------
             A reportedly rapid, simple, and inexpensive method for



the determination of the completion of composting was evaluated for


                    fl21
applicability.  Jamr  ' and others developed the method to determine



the quantity of the putrescible matter in organic wastes.  Their



method is based on the principle that volatile acids are produced



during the anaerobic decomposition of fresh raw organic matter.  On



the other hand, stable organic matter subjected to anaerobic conditions



fails to yield appreciable quantities of acid because the acid pre-



cursors have been decomposed previously.  Generally, their method



involves the incubation of a 5.0 g sample in a screw cap tube at 55°C.



The pH of the sample is determined at 0, 24, 48, and 72 hours.  The



completion of composting is indicated by a pH of 7.5 after the sample



has been held anaerobically for 24 hours at 55°C.  The 48 and 72 hour



analyses are confirmatory.



             The test was modified somewhat for application to solid



wastes which were encountered at the Gainesville plant.  Samples were



ground on a Mikro-Samplmill to pass a 0.2 mm screen.  About 2.5 g of



sample were placed in 20 x 100 mm screw top test tubes.  Water was



added to the tubes to saturate and cover the waste.  No further modifi-



cations were necessary.  The pH of the samples were determined by a



meter.



             It can be expected that samples representing wasteJP which



had received increasing treatment, would under test produce progressively



less acid.  This was not always borne out.  Sampling errors were shown
                              -116-

    -------
to be the cause of this inconsistency.  A sample of stable compost was



tested by this method to give base line data.  Putrescible matter at



two concentrations was added to the stable compost and the mixture was



tested again.  The pH which developed on incubation of the samples



containing the high concentration of putrescible matter was lower than



that of samples containing the low concentration of putrescible matter.



Also, the pH which developed on incubation of the latter samples was



lower than that developed in unamended samples.



              Details on the development of this test for the deter-



mination of putrescible matter in compost and refuse were reported



previously^ '.  The work showed that putrescible matter in solid waste



can be roughly quantitated on the basis of acid production following



anaerobic incubation.  Results were available at 24 hours, but verifi-



cation at 120 hours was desirable.  This method was developed late in



the Gainesville Demonstration Project and, therefore, was not used



routinely in the evaluation of the Metro process.  It appears to have



the greatest potential of any evaluated on this Project.  Further develop-



ment leading to minor modifications is necessary.  What is more important,



however, is the repetitive use of the method to establish its reliability.



              Variation in subsamples has a profound adverse effect which



might be offset by use of much more subsample.  Determination of pH by



the use of a meter was cumbersome and much more precise than necessary.



The use of pH indicator paper would be more convenient and would result
                               -117-

    -------
in less sample disturbance.  The use of inoculum (seed) would probably



increase the precision of the test because it is expected that the



indigenous microbial population will vary widely among sample types.



E.  BACTERIOLOGICAL ANALYSES



        Certain bacteriological analyses were made of raw refuse and



compost to determine the public health quality of these materials.



Selection of these analyses was arbitrary because standard methods



for the bacteriological examination of refuse and compost do not exist.



Examination for coliform bacteria was accomplished because it is common



practice in wastewater technology.  Examination for members of the



Salmonella genus of bacteria was also accomplished because of the poten-



tial this group has for being carried through the food chain of man and



animals.



        1.  Coliform Bacteria



              The State of Florida, Department of Health and Rehabili-



tative Services, required the daily examination of refuse and compost



for both total coliforms and fecal coliforms.  Samples were taken three



or four times each day and composited to represent the entire day.



Samples of the material were taken after primary grinding and after



final grinding.  After considerable experience, the sampling frequency



was reduced to twice weekly and the analysis for total coliforms was



dropped.



              Membrane filtration techniques for the detection of



coliforms were unsuccessful because of the particulate nature of the
                               -118-

    -------
                                                  f QA

 sample.  The multiple tube fermentation technique1- } was satisfactory



 and was used for this purpose on the Gainesville project for about



 two years.  Log dilutions were made from 5.0 g of moist solid material.



 Transfers of each dilution were made to lactose broth and the con-



 firmed test was carried out.  Details of the procedure were previ-


                (2 31
 ously described ^ ' J .  Numbers of coliforms, the coliform index,



 was expressed as the most probable number (MPN) on a dry weight basis.



       2.  Salmonella



             The State of Florida, Department of Health and Rehabila-



 tative Services, also required the daily analysis of raw refuse and



 compost for Salmonella.  The same samples taken for coliform analysis



 were used for Salmonella analysis.  Figure 3  shows the screening pro-



 cedure .



       3"  Extrinsic Bacteria



             The analyses of raw refuse and compost for coliforms and



 Salmonella did not satisfactorily indicate the public health quality



 of these materials.  An. alternative procedure was developed.



             Raw ground refuse was inoculated with a known number of



 various pathogenic and heat tolerant bacteria.  The ground refuse



was placed in a Fiberglas bag and treated in the digester.  After



 treatment, a quantity of the same refuse was recovered and assayed



a second time.   The numbers of organisms before and after treatment



were compared to determine the effect of composting on the growth
                              -119-

    -------
                       FIGURE 3  FLOW SHEET FOR SALWELLA SCREENING
                                         Each 10 gram Subsample
                                                     \
                                         Plant j.nto-25 ml. teirathionale broth
                                                     |    Incubate 48 hours at 37°C
                                            Streak two_ plates of brilliant green  agar
                                                     i     Incubate 24 hours at 37°C
Pink or colorless colonies -
pick to TSI slants
(stab and streak)
   I   Incubate 24 hours at 37°C
                            Green colonies  -
                            discard as lactose fermenters
Butt acid yellow
Slant alkaline (red)
and/or H2S+ blackening) -

Inoculate  1,  Urea agar
           2.  Phenylalanine agar
           3.  Simmons citrate agar
    Incubate 24 hours at 37°C
                            Butt and slant acid  (yellow)-
                            Discard as lactose fermenter
Urea - (no red color)
Citrate + blue
Phenylalanine - no green
  color with test reagent
Possible Salmqnellaj,
re-inoculate TSI slant
Urea+ (red)
Citrate +  (blue)
Phenylalanine
(blue to green
pigment and grape like
odor)
discard as
Pseudomonas
                             eruginosa
      Incubate 8-24 hours at 37°C
Proceed with testing for Somatic,
"0" antigens with polyvalent "0"
antiserum
     ^
Citrate +_
Phenylalanine
+ (green with test
    reagent) -
discard as
Providence
Urea+ (red)
Citrate +  (blue)
Phenylalanine +_
discard as Protei
Poly "0" positive
(good agglutination)
Test witn "0" groups Al
                                Poly "0" negative
                                (no agglutination)
                                discard as non Salmonella
Probably Salmonella
         "0"  i,roup positive  -
         Probably Salmonella
                          All groups negative-
                          Test for washing "Vi"
                          antiserum
                                     "Vi" positive
                                     Boil for 10 minutes to
                                     destroy "Vi" antigen
                                     then test again for
                                     ;'Q" Croups A-l
                   Negative -
                   discard as non-Salmonella
                   after re-testing biochemical
                   and serolo^ic properties
                                     Vi negative
                                     Discard after
                                     repeating biochemical
                                     and serological tests
                                     as non-Salmonella

    -------
or survival of these extrinsic microorganisms.  This procedure
yielded information on the effects of composting on a specific,
known microorganism.
             The test organisms were Escherichia coli, three species
of Salmonella, and Bacillus stearothermophilus (American Type
Culture Collection No. 7953).  E. coli is likely to indicate con-
tamination of intestinal origin, the Salmonellae are important patho-
gens in the food chain of man and animals, and B_. stearothermophilus
is an extremely heat tolerant species of bacteria.  All organisms
were grown on Bacto-Tryptone Glucose Extract Agar (TGEA) to obtain
inocula.  The organisms were washed off the surface of the agar with
a sterile buffer consisting of 1.0 g each of KH-PO. and KJffO. in
1000 ml of distilled water.  This suspension was diluted 1 part by
volume into 100 parts of tap water and then mixed thoroughly with
about one cubic foot of raw ground refuse.  Inoculated refuse (10.0 g)
was assayed to determine the initial number of test organisms.  The
remaining refuse was placed in Fiberglas bags for treatment in the
digesters.  The 10 g sample was added to 500 ml of buffer and was
homogenized in a Waring blender for 5 minutes.  Dilutions of this
suspension were made and plated on either TGEA to count E_. coli and
B_. s tearo thermophilus or on Bacto  Brilliant Green Agar to count
Salmonellae.  Plate counts were made in the same manner from compost
which had been digested in the Fiberglas bag.

    -------
             There were several variations made to obtain additional
information on the growth of these extrinsic microorganisms in a
composting environment.  In addition to composting the seeded refuse,
refuse inoculated with these pure cultures of Salmonellae, was incu-
bated in the laboratory to determine the effect of lower temperatures
on the survival of these organisms in the presence of ground refuse.
This was done by incubating approximately 50 g of seeded refuse at
99°F (37°C) in a loosely covered beaker.  Counts of Salmonellae were
made before and after incubation.
             In another variation, refuse seeded with S_. paratyphi
was subdivided into two quantities.  One quantity was placed along
the wall of a digester where temperatures are known to be lower than
most of the contents of the digester.  The temperature rose from 93°F
to only 108°F in one day.  Another quantity of refuse was placed deep
in the digester where temperatures are known to go higher.  The temp-
erature of this refuse rose from 93°F to 131°F in one day.  After a
sample of the first quantity was taken for a plate count determination,
it was returned to its original location in the digester for further
treatment.  The temperature rose from 108°F to 126°F in three additional
days.
             In a third variation, both spores and vegetative cells of
B. stearothermophilus were used to seed refuse.  The spores of any
organism are expected to be considerably more heat resistant than cells
                             -122-'

    -------
of the same organism.  To obtain spores, a culture was allowed to
age on TGEA.  The spores were washed off the agar with buffer.  The
buffer suspension was pasteurized at 176°F for 10 minutes to kill
any vegetative cells which might not have sporulated.  The refuse
was then seeded and assayed by plate count in the usual manner.
             In a fourth variation, a culture tube containing a
buffer suspension of vegetative cells of B_. stearothermophilus was
placed in the digester for one day.  A plate count was made before
and after treatment in the usual manner.
             During this work, refuse was being moistened with raw
sewage sludge except during the one experiment in which refuse seeded
with E. coli was composted for 12 days.  Bags containing seeded refuse
were placed in the digesters at levels ranging from 65 - 80 inches
above the bottom.  The probable temperature ranges at this level at
varying days of treatment are as follows:  day 1 - 110-130°F, day 2 -
130-140°F, day 3 - 140-160°F, and day 4 and beyond - 140-160°F.
F.  OCCUPATIONAL HEALTH STUDIES
       Bacteriological analyses described in the previous section
were made principally to show the public health quality of the pro-
duct.  That work delineated potential hazards to the compost consuner.
Studies described in this section were made primarily to define
potential and actual hazards to plant personnel.

    -------
        1.  Physical Examinations
             All plant personnel and most administrative personnel
were given periodic physical examinations to detect clinical mani-
festations resulting from their activities associated with the compost-
ing of  urban solid waste.  It was planned to give the first examina-
tion prior to any exposure to solid waste, and then periodically at
intervals of 6 months.  In addition to general physical examinations,
the health of workers was further judged on the basis of the following:
Mantoux and histoplasmin skin tests, hematocrit, hemoglobin, and VDRL
blood tests, chest x-rays, stool examinations for intestinal parasites,
and urinalyses for hydrogen ion concentration (pH), specific gravity,
glucose, acetone, protein, and occult blood.
             Dr. George Little, a local physician, conducted these
clinical studies.
        2.  Noise levels
             Various operations in the processing of refuse fox compost-
ing generate considerable noise.  Two noise level surveys were conducted
to determine whether noise was a hazard.  A type 1555-A Sound-Survey
Meter (General Radio Company) was used for this purpose.
        3.  Intestinal parasites
             The presence of viable parasites in compost would indicate
insufficient treatment.  Accordingly, samples of raw refuse and compost
were examined for parasites.

    -------
             Samples were collected and sent to the Division of
Research and Development, Bureau of Solid Waste Management, Cincin-
nati, Ohio, for analysis.  No attempt was made to cool or otherwise
preserve the samples during shipment.  Samples were prepared for
examination by shaking in the presence of physiological saline and
glass beads.  Next, samples were either examined directly with a low
power microscope or prepared further and then examined microscopically.
When further preparation was required, the biological material was
separated from debris by either the brine gravity flotation method
or Willis*-  * or the formalin ether sedimentation method of Ritchie^  '.
       4.  Airborne Particulate Matter
             The air in dusty areas of the plant was sampled for parti-
culate matter as an indicator of potential public health hazards.  Parti-
culate matter was determined with both a standard high volume sampler
for total particulates and with an Andersen sampler to determine particle
size distribution.
             An 8 x 10" Fiberglas filter was used in the high volume
sampler which is 99% effective in removing particles ranging in size
from 0.1 micron and larger.   The flow rate of air thorugh the instru-
ment was 39.2 cubic ft. per minute.  The instrument was placed in
the plant midway between the primary and secondary grinders.  It was
operated for 4 3/4 hrs. in the afternoon of October 17, 1969.
                             -125-

    -------
             Particle size distribution (weights of particles of
various sizes) was determined at two locations in the plant with the
Andersen sampler.  Two determinations were made on September 8, 1969,
at the operators platform.  Duration of sampling was one hour in the
morning and 30 minutes in the afternoon.  One determination was made
on September 9, 1969, at the picking table.  The duration of that
sampling was one hour.  Particle weights were determined by weighing
the glass collection plates before and after exposure and by sub-
tracting the two values.
G.  ARTHROPOD AND RODENT CONTROL METHODS
       The control of arthropod and rodent pests depended both
on the application of existing technology and on the development
of new technology.  Rats and roaches were readily controlled by
poison baits and commonly used sprays.  The control of flies depended
on a study of their habits as they relate to solid waste and compost.
A successful fly control procedure was developed on the basis of this
study.
       The procedures for the control of rodents and roaches were
presented as follows:
             Rodents:  The sealing of the holes around the water pipes
entering the washroom reduced the rodent population, so that rats and
mice are rarely observed in the Compost Plant.  Liquid and dry Pival
baits are available for the control of rats, but good housekeeping is
the best control.

                             -124*

    -------
             Roaches:   Roaches are normally controlled with a monthly
application of a 2.0$ Diazinon spray.  The best control of roaches is
by good housekeeping.
       These procedures should interest not only operators of compost
plants, but also operators and administrators of solid waste manage-
ment programs.
       The procedures developed for the control of flies are pre-
sented in another section of this report.  The methods and results
are presented together for purposes of continuity.
H.  RESULTS
       1.  Composition of Refuse as Received At the Plant
             Knowledge of the composition of refuse received at
a compost plant is important to both plant design and operation.
It is particularly important in planning salvage operations.
             Refuse was analyzed for major constitutents to deter-
mine variation within given days, variation between given days, and
variation between seasons.  Analyses were made on January 24, July 8,
August 21, and every day during the period of September 10 - 16, 1970.
Samples for the first two dates were taken at the plant receiving
platform.  The final sample of about 2 yd  was comprised of four sub-
samples taken throughout the day to represent the composition of refuse
for those two days.  Samples for the remaining analyses were taken at
the oscillating conveyor ahead of the picking platform.  Refuse located

    -------
at the last two feet of the output end of the conveyor was collected
at designated times throughout the day.  This procedure led to un-
biased sampling.  Samples were sorted by hand into ten major constit-
uents with further subdivision of paper and metal because of their
salvage potential.  All constituents were weighed and reported as
percentages of the total refuse sample on a wet weight basis.
             Table 2 shows the composition of refuse received at the
plant on August 21, 1969, at designated sample times and the day's
average.  The data show typical variations throughout the day.  Table 2
shows the daily averaged composition of refuse during the period
September 10 - 16, 1969, and the weekly average.  Table 2 shows a
summary of refuse composition on the designated sampling dates.  The
data collected in September show that there is great variation of
each refuse constituent throughout each day.  Detailed results represent-
ing designated times of each of the 6 sampling days were presented in
a previous report^ * .   There was less variation noted between days.
Paper constitutes about 50 percent of the total refuse.  Salvageable
paper constitutes about 23 percent of the total refuse.  Food waste
(garbage) averaged about 5 percent, and garden wastes averaged about
13 percent.  Ferrous metals comprised 7.5 percent and non-ferrous metals
(mainly aluminum) comprised 0.6 percent of the refuse.  All data result-
ing from this study represent waste generation by the local community
inasmuch as all the waste, with one exception, is delivered to the

    -------
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compost plant.  Demolition wastes and bulky wastes such as automobiles
and appliances were taken directly to landfills.
       2.  Composition of Material Removed by Magnets
             The composition of the material removed by the magnets
is important information for use in metal salvage considerations.  At
the time of this study (March 19, 1969)  two electromagnets were used
to remove ferrous metals.  They are located after the secondary grinder
and after the digesters.  A sample of the material removed by each
magnet was collected, weighed, dried, and burned to determine its compo-
sition.  The compost leaving the final grinder was also examined for
the amount of metal present.
             The samples taken at the magnets were burned with an
acetylene torch to approximate conditions in a metal salvage incin-
erator and to simulate metal which would meet market requirements.
The metal and ash were then separated and weighed.  The following
compilation shows the composition of material removed by the magnets:
Composition of Material, % of Total
Magnet
Location
After Secondary
Grinder
After Digesters
Moisture Volatile
Solids
3.8 6.6
8.7 13.5
Metal Ash
88.5 1.1
68.2 9.6
Sample
Size
Ibs.
10.4
3.9

    -------
             A sample of final grind compost (5.7 Ibs.) was spread

out on a flat surface and a hand magnet was used to take out the small

amount of remaining ferrous metal.  The nonferrous metal (mainly alum-

inum) was removed by hand picking.  The sample contained 43.8 percent

moisture, 0.14 percent ferrous metal, and 0.06 percent nonferrous

metal.  These results show that the two magnets are removing almost

all of the ferrous metal and that the first magnet is removing cleaner

metal than the second one.  The indication is that the material taken

at the magnet after the secondary grinder has definite salvage poten-

tial if a profitable market can be found.

       3.  Bulk Density of Refuse as Placed in Digester

             The bulk density of the refuse as placed in the digester

is a valuable parameter which may be used to determine digester size

and to design refuse handling equipment.

             Records were kept for a three day period beginning Monday,

March 10, 1969, of the refuse received, paper salvaged, non-compostables

removed at the sorting platform, material removed by the magnet after

the secondary grinder, and compostables to the digester:

     	ITEM	TONS	PERCENT	

     Refuse Received             481.5               100.00
     Paper Salvaged               40.5                 8.41
     Non-Compostables Removed    102.5                21.29
       At Sorting Platform       (74.9)              (15.56)
       At Magnets                (27.6)               (5.73)
     Compostables to Digester    338.5                70.30

    -------
             At the time the records were made, water was being added
at the secondary grinder in lieu of sewage sludge.  The amount of
water added was 740 gallons per hour.  The estimated total amount of
water added was based on the number of hours (19.4) that the conveyor
belt operated.  The amount of water added over the three day period
was, therefore, estimated to be 59.8 tons.
             The dimensions of ground refuse mass in the digester
were 20.0 ft. x 7.16 ft. x 223.5 ft.  The volume was 1185 cubic yards.
             The moisture content of a grab sample of the material as
placed was 44 percent.  The total weight of the refuse plus water
placed in the digester was 398.3 tons.
             The resulting bulk density is only an approximation because
of the difficulty of determining the amount of water added and of measur-
ing the height of the uneven surface of the refuse in the digester.  An
error analysis made of the data indicates that the bulk density value
is 670+60 lb/yd3.
       4.  Moisture Content of Refuse and Compost
             Refuse moisture contents were determined periodically at
several points in the composting process.  This information is useful
for process control and for research.
             Moisture analyses were made on samples of refuse just
before secondary grinding on refuse as placed in the digesters, and
on compost immediately after final grinding.  Data derived from the

    -------
 first sampling point gave an excellent estimate of the moisture
 content of refuse as it is received at the plant and hence the
 amount of sewage sludge that may be added.  Some error was intro-
 duced by the prior separation of the noncompostable fraction.
 However, grinding prior to sampling greatly enhances the homo-
 geneity of the sample resulting in reasonably precise determina-
 tions.
             Samples of about 500 g were collected for the deter-
 mination of moisture in refuse just prior to secondary grinding.
 Samples of refuse and compost from other sources usually ranged
 from 10 - 100 g.  All samples were dried at 75°C to constant weight.
 Normally two days were required to dry the sample.  Table 3  shows
 a summary of all moisture analyses made during the period of May -
 October, 1969.  Moisture contents are reported as a percent of the
 wet weight.  The increased moisture of the refuse as placed in the
 digester in October is a result of more sewage sludge addition.
             Data for three months has been gathered on moisture
 content of the refuse samples taken before the secondary grinder.
 Rainfall data were compared with refuse moisture data.  The follow-
 ing compilation shows the effect of rainfall on the moisture content
 and weight of refuse received at the plant.
               Total   % Moisture    Tons    Tons   Rainfall
Month - 1969   Tons	   Liquid   Solid   Inches
August
September
October
3376
4068
3718
28.5
30.0
23.6
960
1219
877
2416
2849
2841
9.5
11.5
1.2
                             -135-

    -------
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    -------
             The refuse total for October was adjusted upward 220 tons
from the actual 3498 tons received to correct for two days when the
plant was not operated.  August was a low tonnage month mainly because
of the decrease in enrollment at the University.  In September, the
students returned and a record 4068 tons of refuse was processed.
Even after adjusting the tonnage for October, the refuse for the
month is about 350 tons less than that for September.  The data show
that the difference between the total refuse weights for September
and October is mainly due to the difference in moisture contents.
The refuse solids calculated for the two months agreed quite closely.
These data indicate that the actual refuse production for the months
of September and October was about the same, even though the wet
weights alone showed considerable difference.  This difference was
attributable to rainfall.  A plot (not shown) of percent moisture of
the compostable refuse versus inches of rain per month for the three
months of data collected to date indicates a linear relationship.
       •>•  Sewage Sludge Utilization
             The treatment of raw sewage sludge in conjunction with
composting refuse would be highly desirable in that it has the poten-
tial for greatly reducing waste treatment costs.
             The digestion of sewage sludge by conventional processes
is costly and inefficient.  The cost of sludge treatment and disposal
by conventional means approaches 50 percent of the total cost of
treating sewage.  By contrast,  the treatment of sewage sludge by
                             -137"

    -------
composting along with refuse adds very little to the cost of refuse
composting.  Also, sludge contains nutrients, particularly nitrogen,
which might enhance waste decomposition and enrich the compost pro-
duct.  Finally, the refuse as it is received contains insufficient
moisture for good decomposition to occur.  This necessitates adding
water.  Sludge might replace water for this purpose.
             Digested sewage sludge has been treated intermittently
at the Gainesville compost plant during the period from June, 1968
to April, 1969.  During that time the feasibility of composting
refuse-sludge mixtures was shown.  The sludge supplement did not
hinder refuse decomposition.  It did reduce the numbers of coliform
bacteria which survived the composting process.  Tests over an ex-
tended period of time indicated that the probability of survival of
pathogens during digestion was very low.
             Up to April, 1969, sludge had merely been disposed of
by composting after it had been digested at the sewage treatment
plant.  The feasibility and safety of treating raw sewage sludge had
been indicated.  Therefore, the treatment of raw sludge by composting
was initiated on April 28, 1969.  Ideally, the compost plant should
have the capability for treating the entire quantity of sludge and
solid waste produced by a given population.  This would eliminate
the need for sludge digestion at the sewage treatment plant.  The
resulting savings would offset operating costs at the compost plant.
                             -138-

    -------
Several problems had to be solved before this goal could be achieved.
The first raw sludge to be treated had a solids content of only 1.5%
(98.5% water).  It would not be possible to consume all of the city's
sludge if its moisture content were that high.  The result would be
a refuse-sludge blend far too wet to handle and compost by the exist-
ing process.  Table 4 shows that because of this restriction only 10%
of the total raw sludge produced by the City was treated by composting
during May, 1969.
             Another obstacle to sludge addition was the narrow con-
veyor belt on the tripper which is used to place ground refuse in the
digester.  The conveyor would bind occasionally and stop when the refuse
moisture content approached 60%.  This stopped the entire operation
of the plant.  A wider conveyor belt was installed on October 4, 1969,
and there has been no more difficulty.
             A two inch plastic pipe was installed to carry sludge
from the sludge reservoir to the mixing screws.  This proved to be
undependable because of periodic breaks in the pipe and separation
of the pipe joints.  To insure a more dependable system, the plastic
pipe was replaced by a four inch galvanized steel pipe on October 20.
             The City installed a six inch cast iron pipeline to
carry sludge from the sewage treatment plant to the sludge reservoir
at the compost plant.  The new pipeline was first used on October 21,
and it has worked well since then.  Prior to that date,  sludge was
trucked to the compost plant.
                               139

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             A Moyno pump  is used  to transfer sludge  from the sludge
reservoir to the mixing  screws.  It is the only means for controlling
the ratio of sludge to refuse.   It is not practical to adjust the
flow of refuse for this  purpose.   Although the pump speed can be
varied, a convenient means to keep the sludge-refuse  ratio constant
by varying the pump speed has not  been developed.  Consequently, the
only existing means for  controlling this ratio is to  turn the pump
on or off.  This is only marginally satisfactory and  a better means
for regulating the sludge-refuse ratio is urgently needed.
             Attempts are being made to compost the entire output of
sludge from the City.  Starting on October 15, 1969,  a thick sludge
having a solids content  ranging from 5-8% has been  received.  The
thick sludge was obtained by withdrawing it from the bottom of the
sewage plant digesters after it had settled.  Using sludge of this
thickness, it should be  possible to compost the entire sludge output
of the sewage treatment  plant.  The system existing at the termination
of the project was somewhat expedient.  A digester was used to thicken
sludge by settling.  During this process the sludge was partially
treated.  This was a temporary measure pending the completion of
construction at the sewage treatment plant.  Nevertheless, it now
appears feasible to compost the entire sludge output from the City.
             The addition to the sewage treatment plant recently has
been completed.   The existing plant (trickling filter) has a design

    -------
capacity of 5.0 MGD.  The addition (contact stabilization)  has an



additional design capacity of 4.5 MGD.   The addition to the sewage



treatment plant does not include sludge digestion tanks because it



is expected that the compost plant will have the capability for



treating the majority of the sludge produced.  A 30 foot diameter



picket type sludge thickener is included in the sewage treatment



plant addition and is expected to dewater sludge to a solids content



of 4 to 6 percent.



             Records maintained by sewage treatment plant personnel



show that during the period of May through September, 1969, about



1.33 million gallons of raw sludge were withdrawn each month.  The



contributing population was about 52,000.  Sludge solids analyses of



raw sludge delivered to the compost plant have averaged about 1.5%.



Based on these figures, the sludge solids production of the City



appears to be about 85 tons per month.



             The compost plant is currently used for treating all



the refuse from the City, University, and County near the City.  The



contributing population is estimated as follows:



             City of Gainesville          =  52,000



             university of Florida        =  11,100



             Alachua County (near City)   =   6,400



                  Total                      69,500
                              -142-

    -------
             The average amount of refuse received was 3500 tons

per month based on data for July through December.  The October

receipts have been adjusted to allow for a few days when plant

modifications were being made and no refuse could be accepted.

An estimate of the degree of sludge thickening required if all of

the City's sludge is to be composted can be made on the basis of

typical amounts of refuse and sewage sludge produced and their

moisture contents.  The following theoretical compilation is based

on raw sewage sludge production of 1.33 MG per month at a solids

content of 1.5% and refuse production of 3500 tons per month with

3000 tons per month of compostables at 30% moisture.


           SLUDGE SOLIDS REQUIRED TO COMPOST ALL SLUDGE
       Sewage Sludge
Sludge Plus Refuse
Ratio of Sludge To
Compostable Refuse
% Solids
4
5
6
7
8
Total Thousand
Gallons Per Month
500
402
334
286
250
% Moisture
57.2
53.5
50.5
48.2
46.2
Gal /Ton
167
134
111
96
84
             This estimate shows that 134 gallons of sludge per ton of

compostable refuse would be required to dispose of all the sludge,

provided the solids content is 5%.  Thicker sludge would require less
                             -143-

    -------
volume and may be necessary during period of heavy rainfall.  The
two digesters at the sewage treatment plant (0.5 MG each)  could
serve as additional sludge storage reservoirs during periods when
the refuse is wet.
             An estimate of the sewage sludge treated at the compost
plant during October, 1968, was made based on records of volume and
percent solids:

         Amount of Sludge Composted During October, 1969
Period
1st to 14th
15th to 31st
WIOLE MDNTH
Gallons
102,780
138,080
240,860
Tons
435
586

* Solids
1.5
5.8

Tons Solids
6.5
34.0
40.5
The 40.5 tons of sludge solids estimated amounts of 47.5% of the
85 tons produced by the City each month.  The calculations show that
most of the sludge was treated during "the last half of the month when
thicker sludge was being treated.  An estimated 100,000 gallons of
water was added in place of sewage sludge during October because of
sludge handling modifications.  The combined amount of sludge and
water used for the month was, therefore, 340,000 gallons.
             Data from the period in October when thick sludge was
added indicate that the compost plant can take all the sludge from
the City.  During the week of October 27 through 31, a total of

    -------
73,000 gallons of thick sludge (about 6 to 8% solids) was mixed



with 610 tons of compostable refuse resulting in a sludge-refuse



ratio of 120 gallons per ton.  These results and the previous



theoretical calculations indicate that a strong potential exists



for consuming all of the sludge produced by the City.



       6.  Effect of Sewage Sludge on Refuse Decomposition



             The incorporation of raw sewage sludge into compost-



ing refuse may be a successful method for sludge disposal.  Addi-



tionally, the cost of this type of sludge disposal is expected to



be very low as compared with conventional methods.  Thus, the cost



of composting might be credited with the savings realized by this



type of combined treatment.



             This important aspect of composting was studied to deter-



mine its technical and economic feasibility.  The use of digested



sewage sludge as the moistening agent for ground refuse was initiated



on June 5, 1968.  City water had been used prior to that date.  When



experience from plant operation showed that sludge could be used and



laboratory studies showed high probability for pathogen destruction



raw sewage sludge was used for moistening.  This practice was started



on April 28, 1969.  This presented an opportunity to compare the effect



of the two moistening agents on refuse decomposition.  This was done



by comparing C/N ratio reduction of water-moistened refuse with that



of sludge-moistened refuse.  Table 5  suggests that the reduction of
                             -]kS-

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                            -146-

    -------
C/N ratio was approximately 60 percent greater when sludge had been



used as compared with water.  However, this difference is not con-



vincingly significant because of the limited analytical precision.



This work was based on the analysis of compost samples which did



not necessarily represent comparable samples of raw refuse.  After



the development of the Fiberglas bag technique, the same sample could



be analyzed before and after composting.



             Experiments were designed to determine the effect of



sewage sludge on the decomposition of refuse and on the quality of



the compost product.  Raw refuse and compost was analyzed for carbon,



nitrogen (hence the C/N ratio), COD, BOD, and volatile solids.  A



greater reduction of C/N ratio and the other three parameters mani-



fested by the sludge amended compost than in the unamended compost



was evidence that sludge enchanced the composting process.  In each



experiment a quantity (usually 1/4 - 1/2 yd ) of raw ground refuse



was mixed with a shovel or fork.  A sample of this refuse was analyzed.



Other samples were put into Fiberglas bags which were placed in the



digester within the production quantity of refuse.  Sewage sludge in



varying quantities and concentrations was added to still other samples.



These were analyzed before and after composting.



             A total of 8 experiments incorporating 44 treatments and



replications were made to determine the effects of sludge supplements



on refuse composting.   Detailed results were reported previously^- '•'.

    -------
Analyses for C/N ratio, COD, BOD, and volatile solids were never



consistent in showing that sludge stimulated waste decomposition.



The BOD test was the most reliable for this purpose, whereas the



volatile solids test was least reliable.  There were no indications



from these four tests that sludge could not be treated by composting.



Some experiments showed that high concentrations of sludge added



significant quantities of putrescible matter to raw waste.  Further-



more, putrescible matter in the sludge supplemented compost was



frequently higher than that in the unsupplemented compost indicating



that sludge burdened the composting process.  The highest concentra-



tion of sludge which was evaluated was 0.64 kg sludge (2.3 percent



solids) per kg of refuse, which is equivalent to 154 gallons per ton.



Even at this high concentration of sludge there were no indications



that the process was seriously hindered.



             Sewage sludge also has the potential for enriching the



compost product with nutritional elements.  Nitrogen is the most



important element which might be added by sludge supplements.  The



addition of sludge did, in fact, raise the nitrogen content of the



refuse-sludge mixture.  The nitrogen content of unsupplemented refuse



typically ranged rom 0.4 - 0.7 percent; that of supplemented refuse



typically ranged from 0.4 - 1.1 percent.  There is evidence that



nitrogen was lost during the composting of sludge supplemented refuse.



It can be expected that nitrogen in the form of ammonium compounds

    -------
would be lost during the thermophilic stage of composting.  The

mechanism of this loss was not studied, but analysis of refuse

heavily supplemented with sludge before and after composting fre-

quently showed a loss of nitrogen ranging from 0.1 - 0.3 percent.

             The addition of sewage sludge to refuse had an unex-

pected effect on the coliform populations in the composting refuse.

Table   (Section H-12) shows that when water was used to moisten raw

ground refuse the coliform population in the resulting compost re-

mained stationary or increased relative to the original population.
                                                        ' ' •<"
By contrast, when sewage sludge was used the coliform population in

the resulting compost decreased except possibly during the sampling

period of October 2, through December 31, 1968.  Because the usual

standard deviation of the MPN method for the determination of coliform

indices is no better than one logarithmic unit, even this apparent

increase may not be real.  The extent of coliform reduction when

sludge was added can be equated approximately to the amount of sludge

being added.  For example, during the June 5 - June 26, 1968, sampling

period when sludge was added at the rate of 77.2 gal per ton of refuse,

the coliform population was reduced by four logarithmic units.  During

January and February  of 1969, when sludge was added for the most part

at the rate of 27.2 gal per ton of refuse, the coliform population was

reduced by only two logarithmic units.  In the conduct of this work

there was no assurance that the same refuse was assayed before and

    -------
after composting.  Thus, the data can be expected to vary widely.
In spite of this, the large number of assays made strongly suggests
that sludge supplements do indeed reduce coliform numbers.
             Compost derived from sludge supplemented refuse was
darker than that derived from water moistened refuse.  The difference
in color usually was subtile and, therefore, was not noticeable until
the compost had been finely ground for chemical analysis.  Color
observations were made on matched samples prepared for composting in
the Fiberglas bags.  Untreated control samples, including those which
received sludge and composted controls which were moistened with water,
were light grey and were indistinguishable on the basis of color.  When
sludge was added at varying quantities the darkness of color in the
compost was directly related to the quantity of sludge added to the
refuse.  Thus, the dark color resulted from the composting of sludge-
supplemented waste and not from the sludge itself.  In the 7 of 8
experiments designed to determine the effects of sludge on composting
by the Fiberglas bag method of sampling, there were color differences
among the samples which were attributable to sludge.  Experience in
the practice of composting indicates that as compost becomes pro-
gressively stabilized it becomes darker.
             Still another effect of sludge on composting was rioted.
Limited data suggest that there is a greater loss of weight resulting
from the composting of sludge supplemented refuse than from composting
                             -150*

    -------
water moistened refuse.  In some early work ground refuse in Fiberglas
bags was weighed before and after composting to determine weight losses.
Weight losses of water moistened and sludge moistened compost were
determined in separate experiments according to how the production refuse
was moistened.  Experimental variation was so great that no conclusions
could be drawn.  In subsequent work weight losses of closely matched
samples were compared.  In the only experiment when this was done, water
moistened refuse lost 2.8 percent weight as a result of digestion for
6 days and windrow curing for 30 days.  Sludge moistened refuse which
received identical treatment lost 9.3 percent weight.  It must be empha-
sized that although this experiment was carefully controlled, the result-
ing data are only single determinations.
             Sludge as contrasted with water as the moistening agent
caused several other pronounced effects on the digestion of refuse as
follows:  1) temperatures rose more rapidly, 2) temperatures were more
uniform throughout the digester, and 3) oxygen consumption was much
greater.  These results were presented in detail in a previous report*- ' .
In review, however, when sludge was used for moistening, the temperatures
in the digesters leveled off between the second and fourth days.  When
no sludge was used temperatures did not level off until the fifth or
sixth days.  Uniformity of temperatures at the various levels in the
digester was demonstrated by the narrow range of 162-172°F on the third
day sludge was added.   Typically, temperatures ranged from 140-165°F
                             -151-

    -------
on the third day when no sludge was added.  These ranges do not



include temperatures at the bottom 6 inches of the digester which



typically are approximately 100°F, regardless of whether water or



sludge had been added.  The high oxygen demand of sludge was also



manifested.  When no sludge was added the typical oxygen residual



in the digesters ranged from 16 - 19 percent.  When thick sludge



was added this residual concentration was about 9 percent even



though the aeration period was extended from 16 to 28 minutes per



hour.



             In conclusion, there was no experimental evidence to



show that raw sewage sludge could not be used as a moistening agent



for refuse which is to be composted.  It will be necessary, however,



to furnish additional air to the digesters when large amounts of



sludge are added.  An operational problem which is correctable  was



occasionally experienced in the plant.  If the plant operator becomes



careless and fails to turn off the sludge pump when no refuse is being



processed sludge is spilled about the plant.  This gives rise to



various public health problems such as odors and flies.  The same



carelessness when water is being used leads to no serious problems.



It was not conclusively demonstrated that sewage sludge enhanced



or stimulated the decomposition of refuse.  However, evidence from



a wide variety of experiments and observations suggests that there



was some stimulation as well as enhanced killing of coliform bacteria.
                             -152-

    -------
It is doubtful whether the stimulation of refuse decomposition can
be substantiated on an industrial scale.  Attaining the necessary
controls would be impractical if not impossible.  Controlled laboratory
work would be more definite and efficient.
       7.  Decomposition of Refuse in the Digester
             The scope of this investigation was centered around
characterizing refuse decomposition in the digesters.  The objective
was to optimize the digestion process.  In the operation of the plant
process variables such as detention time and aeration rates were
selected arbitrarily, for the most part.  Therefore, it is likely
that they could be improved.  The effects of process variables on
digestion were determined on the basis of heat production (measured  ,
as temperatures), CCL concentration and oxygen concentration.
             A series of two experiments was designed to show the
effect of refuse particle size on the rate of decomposition.  A
series of 6 experiments was designed to show the effects of adding
sewage sludge and of aerating the refuse at four different rates.
The first two experiments, one of which sludge was used and the
other without sludge, were somewhat preliminary.  The other four
experiments, in which the aeration rates were tested, were more con-
clusive.  One of the aeration experiments also provided valuable in-
formation on sludge digestion.

    -------
       a)  Decomposition Rate as A Function of Particle Size:  The



rate of decomposition was compared in both coursely and finely ground



refuse.  Rates were judged on the basis of temperature development in



the digesters.  Finely ground refuse was obtained by shredding it



with both the primary and secondary grinders.   Coursely ground refuse



was obtained by shredding it with only the secondary grinder.  Water



was used to moisten both types of refuse.  Temperatures of the finely



ground refuse rose from 120°F to values ranging from 167°F to 183°F



after six days of digestion.  Temperatures of the coursely ground



refuse rose from about 115°F to the range of 153°F to 164°F after six



days.  Thus, it was indicated that finely ground refuse decomposed



in the digesters at a considerably higher rate.  However, other factors



such as moisture content, refuse composition,  and air supply may have



influenced the results.  The opportunity to use the combination of



grinders never occurred again, and these important experiments were



not repeated.




       b)  No Sewage Sludge - July 7:  The refuse under test was among



the first to be ground with the new primary grinder.  The particle size



of the material as placed in the digester was  quite small compared with



that of previous operations.  The test area was located at the north end



of the east digester. Water addition resulted in an initial moisture con-



tent of about 501. The refuse was held in the  digester for 22 days for the

    -------
experiment.  A Hays Model 621.31:30 Orsat gas analyzer was used for
the determination of oxygen and carbon dioxide.  The Minneapolis-
Honeywell instrument console was unreliable for gas analyses, but it
was satisfactorily used for the determination and recording of tempera-
tures.  These instruments were used in this entire series of experiments.
In the normal operation of the digesters, the aeration blowers run inter-
mittently.  This causes considerable fluctuation in digester gas content.
To minimize these fluctuations, the gas analyses were made just before
the blower turned on.
             Figure 4 shows that the temperature and CO- curves paral-
leled each other fairly well whereas the oxygen curve opposed the other
two.  This was as expected because heat and C02 are products of decompo-
sition and oxygen is a reactant.  Note that the elevations at which the
temperatures were taken do not necessarily correspond with the elevations
at which gas samples were taken.  HoweVer, three of the four curves cor-
respond very closely.
             About 4-5 days were required before temperatures leveled
off.  From 0-2 days, temperatures at all levels were within 15°F of
each other; after that time they diverged rapidly.  In the beginning,
temperatures at the 25 in. and 48 in. levels were higher than that at
the 66 in. level.  Between the third and fourth days, the temperatures
at these levels reversed and after then they were invariably cooler
with increasing depth.  This indicates the decomposition started sooner

    -------
  200
  180
  160
  140
4J
M
0)
  120
  100
   20
   15
 jjio
 4J
 0)
 y  5
 u  D
 01
 04
   20

 a)

 o
 0)
 a  5
 v
                             FIGURE i 4
:EMPERATURE,  OXYGEN,  AND CARBCMDIOXIDE  IN DIGESTER - JULY 7,  1969
                                                                        66" Above Bottom
                                Begun July  7,  1969
                                Initial  Refuse Height  =7.0  Ft.
                                No  Sewage Sludge Added
                                                          23" Above  Bottom
                                                          35"
                                                          47"
                                                          66"
                                                                       66" Above Bottom
                                  10    12     14   16
                               -156-  Time in Days
                                             18
                                                   20
22

    -------
near the bottom of the digester than at the top.  Oxygen consumption
and C0~ production tended to verify this.  Subsequently, heat was
transferred upwards.
             The digesters are forcibly aerated and it is possible
and desirable to keep the oxygen content at a uniformly high level.
However, somewhere between days 9 and 10 the oxygen content of the gas
in the refuse dropped.  This happened when refuse was removed from an
area in the digester adjacent to the test area.  This allowed the air
to pass freely through the empty digester rather than through the test
waste.  On day 11, the air duct valves were closed where there was no
waste and the oxygen level in the test area began to increase to
previous values.  The temperature rose from a maximum of 183°F at
11 days to 196°F at 12.5 days due to the large increase in air supply.
On or about day 19, some more waste was removed near the test area.
This caused temperatures to rise again.
             This experiment strongly suggests that it would be desir-
able to agitate the waste during its digestion.  Agitation would tend
to equalize temperatures and concentrations of oxygen and carbon dioxide.
A logical first time to agitate may be at four days, or the first time
that temperatures at various levels begin to differ widely.  That aera-
tion had a cooling effect was shown by the rapidly rising temperatures
at all levels when the aeration rate was reduced.
             Oxygen and C02 concentrations were determined frequently
for a period of two hours to determine their ranges as a function of
                              157

    -------
the aeration cycle.  Knowledge of these ranges is useful in interpre-
ting Figures 4-11,  which consist of data taken just prior to turning
on the blowers.  Determinations were made at the 5.5 ft. level.  Gas
concentrations were determined only in the north half of the east
digester.  One blower serves both the north and south digester halves.
The aeration period was 18 min/hr. for the north half and 20 min/hr.
for the south half.  Figure 5 shows that the oxygen ranged from 31
to 9% by Volume during the aeration cycle.  Carbon dioxide levels
ranged from 8% to 13%.  The gas composition data show that some air
was going to the north half while the south half was being aerated.
This was evidently the result of one of the air duct valves not: being
completely closed.  The additional air to the north half resulted in
less variation in the gas composition than would be expected under
normal conditions.  The results also show that the refuse in the di-
gester still has a significant oxygen demand after 21 days.
             Figure 6 shows the moisture content at 10, 15, and 22 days
in the digester.  Samples were inspected for physical appearance on
the twenty-second day of test.  Those taken from the upper third of the
digester appeared more decomposed than any other samples.  This is the
region of highest temperature during most of the detention period and
the lowest moisture content near the end of detention.  The available
data neither support nor discount a possible correlation between these
two conditions.
                                158

    -------
                                        FIGURE  5




             OXYGEN AND CARBON  DIOXIDE LEVELS IN DIGESTER - JULY 28,  1969

             Readings Hade at 5.5 Ft.  Klevation after 21 Days in Digester
 o
•p

0>
o
 O
o
o
1)
O
ft.
     20
     15
     10
            Off
     20
     15  *
  10  •
                                  North On
            Off
                                                           South On
                  18
                            38 U2         60        78

                                 Time in Minutes
                               98  102
                               120
             Off
                  IS
                  South  On
Ilorth On
Off
South On
                            33  1*2         60         78

                                 Time in Minutes
                              98  102
                                                                                120
60.
   50
a

    -------
             c)  Raw sewage sludge - August 1;  This is the first

experiment in which raw sewage sludge was used as the moistening

agent.  The test area was at the north end of the east digester.

The quantity of sludge added was approximately 50 gallons per ton

of refuse moistened.  Sludge solids were estimated to be 1.5 per-

cent.  The initial moisture was 43%.  Air volumes were determined

by the air flow meter on the instrument console.  Air was regulated

by the digester duct valves to approximately 4.5 ft  per hour per

ft  of refuse.

             The moisture in the upper third of the digester at

7 days ranged from 43% to 57%.  Figure 7 shows that the temperature

rose at about the same rate as in the previous experiment when no

sludge was added.  Maximum temperatures achieved were about the same

prior to the disturbance experienced during the first test.  Appar-

ently the quantity of sludge added was too small to produce a notice-

able effect.

             The compost was removed from the digester after twelve

(12) days and the moisture content and pH at various elevations

measured:

       Elevation in Inches        % Moisture        pH

                87
                75
                63
                51
                39
                27
                15
                 3
28.1
43.8
44.7
49.1
52.0
43.7
38.8
23.2
6.5
4.8
5.1
4.9
5.1
5.2
6.0
6.9

    -------
          TEMPERATURE, OXYGEN, AND CARBON DIOXIDE  IN DIGESTER  - AUG.  1,  1969
 180
 160
3140
 120
                                     Begun August 1,  1969
                                     Initial Refuse Height =7.3 Feet
                                     Raw Sewage Sludge Added
                                                                               70"  Above
                                                                               47"     Bottom
                                                                               22"
                                                                               8"
 100
  20
  15
                                                               10
                                      Time in Days
                                        FIGURE  7
11
                                                                              70" Above Bottom
                                                                              52"
                                                                              40"
                                                                              27"
12

    -------
             These data further suggest that decomposition is not
uniform in the digester and that there is a need for periodically
mixing the refuse.  Moisture contents of waste near the top and
bottom of the digester were below the generally recognized range
for good composting (40 - 651).  It should be noted that generally
the pH varied inversely with moisture content.
       d)  Effect of Aeration Rate - August 20, September 4 and 16:
             The effect of aeration rate on the composting process
was studied by varying the air supply and observing the temperature
and gas results during the usual 8 day digester detention time.  The
study was made in the north half of the west digester.  The first
step was to determine the output of the aeration blower with the
digester full of refuse.  The air flow meter of the instrument console
was used as the basis for regulating the valves on the air supply ducts
to obtain a uniform air supply along the digester.  The air supply was
about 3800 cubic feet per minute (cfm) for the north digester half or
about 540 cfm for each of the seven 20.67 feet long tanks.  At the time
the study was made, the blower ran 16 minutes per hour on the north
half of the digester.
             The third experiment was started on August 20 with an
almost normal air supply of 600 cfm per tank.  The initial refuse
height was 6.7 feet.  Therefore, the resulting aeration rate was
3.52 ft^ per hour per ft^ refuse.  Raw sewage sludge was added to
                             -162-

    -------
give an initial moisture content of 49%.  Samples taken from an
elevation of five feet at 3 and 8 days contained 44% and 43% moisture,
respectively.
             Figure 8 shows that the maximum temperature reached was
165°F; this occurred at 5 days.  As usual, the oxygen and carbon
dioxide concentrations were determined just before the aeration blower
turned on.  Oxygen concentrations were usually in excess of 15% while
carbon dioxide was usually less than 5%.
             By adjusting the air duct valves, an excessive lair flow
amounting to 1.5 times normal was fed to the refuse for the fourth
experiment which was begun on September 4.  The initial refuse height
was 7.2 feet and the air flow was 990 cfm per tank.  The resulting
                         3                3
aeration rate was 5.32 ft  per hour per ft  of refuse.
             The initial moisture content was 491.  At 8 days the
moisture content was 52% at the 2 ft. and 8 ft. elevations.  The mois-
ture data show that an increase in aeration rate does not dry out the
refuse.  Evidently, moisture produced by the composting process will
replace any that is driven off provided the initial moisture is high
enought and the aeration rate is not too high.
             Figure 9 shows that temperature at the 66 and 49 inch
levels in particular rose rapidly and leveled off at about 1.5 days.
Temperatures at other levels rose as expected.  Oxygen and CO- concen-
trations stabilized in about a day as compared with 2-4 days in pre-
vious experiments.
                               -143-

    -------
        180
                 TEMPERATURE, OXYGEN, AND CARBON DIOXIDE  IN DIGESTER  - AUG.  20,  1969
        160
     ofa  140
—     0)
      (0
      M
      
    -------
                                     FIGURE (9
       TEMPERATURE,  OXYGEN,  AND CARBON DIOXIDE  IN DIGESTER - SEPT.  4,  1969

      180  r
      160
D
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£
13
140
      120
      100
 o,
      20
      15
 ffl    10
                                                       83" Above Bottom
                                                       32"

                                                       66"  *
                                                       49"  °
                                                       14"
                                         Begun  September 4,  1969
                                         Raw Sewage  Sludge Added
                                         Initial  Refuse  Height  =  7.2 Feet
                                         Aeration Rate =5.32 Ft^ Air Per Hour
                                                             Ft-* Refuse
                                                               O  56" Above Bottom
                                  TIME IN DAYS

                                       -1687-

    -------
             The fifth experiment was begun September 16 and had
an air supply of 0.5 normal.  The initial refuse height was 6.3 ft.
with an airflow of 310 cfm per tank.  An aeration rate of 1..90 ft
per hour per ft  of refuse resulted.  The moisture content at the
beginning was 46%.
             Figure 10 shows that temperature development was; slow
but reached 167°F at 4.5 days.  Oxygen and carbon dioxide levels
were maintained well.
             On comparing the results of the three runs, several
things became evident.  The oxygen demand of the refuse-sewage sludge
mix appears to be satisfied with all three of the aeration rates.
It should be noted that the raw sludge used in these experiments was
added at a rate of from 30 to 50 gallons per ton of refuse moistened
and contained only 1.5% solids.  It is estimated that addition of 110
gallons per ton of a 6% solids sludge would be required to consume all
of the sludge produced by the City.  The oxygen demand of this thick
sludge would be considerably more than that of the dilute sludge used
during these experiments.
             Even though the sludge used in these experiments was
dilute, there were suggestions that sludge as contrasted with water
caused temperatures to rise at a faster rate and level off more quickly.
In experiment 3 (Figure 8) temperatures leveled off between the second
and third days; in experiment S (Figure 10) temperatures leveled off

    -------
                                           FIGURE W
            TEMPERATURE, OXYGEN AND CARBON DIOXIDE IN DIGESTER - SEPT 16, 1969
   180
   160
CM
o
 0)
 H
 3
 4-)
   140
EH  120
   100
                                                          63 in.Above Gravel
                                             45  m.
                                             29  in.

                                             15  in.
                                                           4 in.
Begun Sept. 16, 1969
Raw Sludge Added
Initial Refuse Height
Aeration Rate = 1.90
                                                           1 in.
                                      6.3 Feet
                                       Air Per Hour
                                       Refuse
                                     42 in.Above Gravel
                                     30 in.
                                     18 in.
                                     6 in.
                        345
                        Time  in Days

    -------
between the third and fourth days.  Sludge was used for both experi-
ments.  By contrast, in experiment 1 (Figure 4) when no sludge was
used, temperatures did not level off before days 5 and 6.  This
stimulated rise in temperature correlates well with the earlier
findings that sludge stimulates decomposition.  An exception occur-
red in experiment 2 (Figure 7) in which sludge was added but tempera-
tures did not level off until days 5 or 6.  However, in experiment 2
some unknown influence profoundly slowed and then increased the
temperature rise.  It is doubtful that the moistening agent would
do this.
             The 1.5 normal aeration rate resulted in faster tempera-
ture development at some levels than the normal and 0.5 normal rates.
The 1.5 normal aeration rate also made temperatures more uniform
throughout the mass than did the others.  The faster development and
increased uniformity of temperature resulting from the increased
aeration rate indicate conditions for better decomposition.  Whereas
it is not possible to increase the air supply without changing the
blower setup; it is possible to extend the aeration period.  (This
was done in the next experiment;)
             One interesting result of the temperature observations
was that little temperature rise was noted at the levels from the
bottom up to four inches.  (See Figures 9 and 10.)  This again in-
dicates the need for mixing the refuse sufficiently during the

    -------
digestion process.  It is expected that decomposition would progress



very slowly at these low temperatures.  Also, temperatures below



122°P C50°C) are seldom considered high enough to kill pathogens



within a practical length, of time.



             On the other hand, temperatures attained throughout most



of the digester after 2-3 days are far too high for optimum microbial



activity.  Temperatures above 131°F (55°C) limit microbial activity



to only the thermophilic types.  The optimum temperature range for



growth of thermophiles is 131° - 140°F (55° - 60°C).  The maximum



temperature at which growth occurs is 167°F (75°C).  Very frequently



digesters operate near this temperature.  This is not to say that



the digesters should be operated at lower temperatures.  High tempera-



tures certainly favor rapid decomposition.  Thus, it is strongly in-



dicated that decomposition above 167°F is not a result of microbial



activity.



       e)  Effect of Extending Aeration Time - October 27:  The three



previous experiments on refuse aeration have indicated that a higher



aeration rate produced conditions for better decomposition.  Those



experiments were conducted when dilute sewage sludge was added.  The



addition of thick sludge was started on a regular basis in mid-October.



The aeration period for the digesters was extended in anticipation of



the increased oxygen demand of the thick sludge.  It was extended from



16 minutes per hour to 28 minutes per hour in the test half of the



digester.

    -------
       An experiment designed to determine the effect of the extended
aeration time on refuse decomposition was begun October 27.  The study
was to have run for an 8 day period.  Unfortunately, the refuse was
removed accidentally after 3 days and much of the value of the experi-
ment was lost.  However, those data that were collected were meaningful.
       Thick sewage sludge was added to the refuse under study at a
rate of 110 gallons per ton.  Sludge solids ranged from 6 to 7%.  The
initial moisture content was about 551.  Air supply to the section of
the digester containing the refuse under study was 610 cfm for 28
minutes per hour.  The initial refuse height was 7.0 feet.  The result-
ing aeration rate was 5.9 ft  per hour per ft2* of refuse.
       Figure 11 shows that temperatures rose quickly and that they
were uniform throughout most of the depth.  Temperatures were still
increasing at all levels when the probe was withdrawn after 3 days.
Refuse temperatures at 20 inches and above exceeded 160°F on the third
day.  These extraordinary temperatures gave a strong indication that
decomposition was accelerated by the increased air supply and/or by
the thick sludge.
       The high oxygen demand of the refuse-thick sludge mixture was
shown by the results of the gas measurements.  Oxygen levels dropped
sharply during the first 3 hours in the digester.  The oxgyen con-
centration at the 75 inch elevation was 3.5% after 3 hours.  The high
concentration of sludge was evidently responsible for the rapid oxygen
uptake.  Oxygen concentrations recovered somewhat after the initial
drop but they were far lower than normal despite the high aeration
                            -170-

    -------
        180  1
160 '
"\
    I
    1
    s
        120 '
        100
         20 '
                                                 FIGURE  5,1

                 TEMPERATURE, OXYGEN, AND CARBON DIOXIDE IN DIGESTER - OCTOBER 27,  1969
                                                  O 68" Above Bottom
                                                  A 54,.

                                                  • 36"

                                                  B 20"    "      "
                                            Begun October 27,  1969
                                            Raw Sewage  Sludge  Added
                                            Initial  Refuse Height = 7.0 Ft.
                                            Aeration Rate = 5.9 Ft-* Air Per Hour
                                                                 Ft3 Refuse
                                                  O 75" Above Bottom

                                                  A 56"

                                                  • 38"     "      "
                                                 O  75" Above Bottom

                                                 A  56"

                                                 •  38"
                                             TIM; IN DAYS
                                                 1-11

    -------
rate.  In all previous experiments, the oxygen concentrations ranged
from 16 - 19% after the initial drop.  In this experiment, the average
oxygen concentration was about 9%.
             Carbon dioxide production was high during the first 3
hours.  A 002 concentration of 19% was measured at the 75 inch ele-
vation after 3 hours.  On the third day, C09 concentrations at all
                                           &
measured elevations dropped to about 8%.
             This experiment shows the advisability of extending the
aeration period for the treatment of the thick sewage sludge supple-
ment.  It appears that oxygen levels would have been quite low in the
digester if the previous aeration period had been retained and thick
sludge added.  Anaerobic conditions might have developed and produced
foul odors.
       8.  Curing of Compost
             Although the mechanical methods of composting are
considered accelerated methods, the effluents from these systems are
not sufficiently decomposed to be used directly for most agricultural
purposes.  A curing period is required during which time the waste
decomposes to a relatively stable product.
             Compost was cured in large storage piles at the Gaines-
ville Compost Plant principally because of a space shortage.  It has
been observed that whenever these large piles were disturbed, a strong
sour odor evolved.  The odor was indicative of acid accumulations which
develop under anaerobic conditions of decomposition.  Anaerobic
                             -172r

    -------
decomposition is slow and inefficient, and curing must proceed for
a long time before the compost is suitable for agricultural uses.
             One of the large curing piles was observed for indica-
tions of decomposition.  Samples were taken from several locations
within the pile and analyzed for moisture, pH, and BOD.  Just prior
to sampling, a large quantity of compost was removed, thus exposing
a cross section of the pile.  Samples were taken from this newly
exposed surface.
             Figure 12 is a diagramatic sketch of the curing pile.
The results of the analyses and the estimated age of the compost
are given for each layer.  The uppermost layer was a dry crust of
about 6 inches deep; all other layers were approximately 7 ft. deep.
The second layer was comprised of normal compost at the top and
charred compost at the bottom.  The charred material resulted from
spontaneous combustion sometime before sampling.  The zone of 12
month old compost was comprised of some of the first compost pro-
duced at the plant.  Temperatures of the various zones were not
taken.  However, it was noticed that they were high and almost
uniform except at the uppermost layer which was cool.  The moisture
content of most layers was too low for curing.  Similarly, the acid
conditions in the bottom half of the pile were unfavorable for cur-
ing and were strongly indicative of anaerobic conditions.  That
curing had progressed further at the top of the pile than at the

    -------
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bottom is not indicated by the BOD data.  Furthermore, BOD values
in the range of 40 - 75 mg/g are typical of compost treated only
by digestion.  Thus, it appeared that most of the compost had not
cured despite the long storage time and the high temperature of
the pile.  It follows, therefore, that uncured compost should de-
compose when subjectied to favorable conditions.
             To test this hypothesis, some old anaerobic compost was
tested for stability by an established practical method.  It is known
that unstable compost will decompose when it is moistened and sub-
jected to aerobic conditions.  The course of decomposition can be
followed by observing the temperature of the pile which can be ex-
pected to rise at first, and then fall as the compost is either stabi-
lized or dried.  Some old unstable compost was windrowed to attain
satisfactory conditions for decomposition.  Six cubic yards of the
most cured compost available (judged to be about 1 year old) was
spread in a thin layer to cool.  It rained on the second and third
days raising the moisture content to 47.7 percent.  On the fifth day,
the compost was formed into a cone shaped pile and temperatures were
measured in numerous locations.  Temperatures ranged from about 115 -
122°F (46 - 50°C).  The probe was then placed in its permanent position
of 2 - 3 feet below the apex in the center of the pile.
             Temperature data are given in Figure 13. The probe stabi-
lized shortly before noon during the first day of curing and the timing
                             -175*-:

    -------
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    -------
of the experiment was begun.  Each daily interval in Figure 2 repre-
sents the noon temperature and the midpoint between each day indicates
the midnight temperature.  During the first 4 days the temperature
rose continually, but the rate of increase was slightly higher during
the day than at night.  Thereafter, temperatures rose during the day
and dropped during the night.  These diurnal fluctuations obviously
resulted from ambient influences.  The waste decomposed at a rapid
rate for the first 4 days, at a lesser rate to approximately 11 days,
and then at a declining rate.
             On the nineteenth day, the moisture had dropped to 26.2
percent.  The waste was remoistened to 42.8 percent, aerated by lifting
it with the front-end loader and dropping it repeatedly, and shaped into
a pile.  Within minutes, the temperature started to rise and within 48
hours it surpassed the previous maximum.  These temperature data clearly
show that old anaerobic compost was not cured, and that it was decom-
posable when subsequently subjected to suitable conditions.  These
findings suggested further work to determine the extent of curing of
freshly digested compost treated under aerobic conditions.
             Two experiments were conducted to determine the extent of
treatment attained during the windrow curing of fresh compost.  Water
had been used to moisten the waste in the normal operation of the plant
at the time the work was done.  The windrows constructed for this work
were not turned or otherwise aerated.
                              -177-

    -------
             In experiment 1, effluent compost was contained in
Fiberglas bags which were deposited within a pile of compost con-
structed for exclusive experimental use.  The pile consisted of
effluent compost of the same age as the sample.  It was sufficiently
large so as to simulate actual production conditions in a windrow.
A subsample was prepared for immediate analysis.   Three other sub-
samples were placed about 18 inches beneath the surface where they
remained hot and moist.  Samples were removed from the pile after
6, 15, and 94 days of curing.  Experiment 2 was refined somewhat
to provide comparative data on raw waste, waste composted in the
digester for 10 days and waste cured in a pile for 3 months.  All
three subsamples were derived from the same well-mixed batch of
waste.
             Table 6 clearly indicates that plant effluent was
highly unstable and that it continued to decompose during curing.
At 3 months when experiment 2 was terminated, triplicate samples
contained 29.4, 31.7 and 35.3 percent moisture.  Further decompo-
sition may have been inhibited by drying.
             It must be emphasized that the Fiberglas bags were
placed near the surface of the curing windrows and, therefore, were
subjected  to optimum conditions for decomposition in an unturned
windrow.  When both of the most cured samples were removed from the
windrows, it was observed that only a layer of compost extending from

    -------
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2 inches below the surface to about 20 inches deep was warm and
moist.  The compost at the very surface and below 20 inches was
cool, dry, and looked poorly decomposed.  Therefore, the extent
of curing observed in these experiments represents something near
the maximum attainable, after 90 days of treatment in aerobic
windrows.
             This preliminary work did show the unstable nature of
effluent compost.  Further work was conducted to quantify decompo-
sition in the digester and in subsequent curing in windrows.  The
objective of this work was to quantify the amount of decomposition
accomplished in the digester and during subsequent windrow curing.
The second objective was to compare the rates of curing in a well-
managed windrow with that in an unmanaged windrow.  The comparison
was made because production compost was cured in windrows during
one period of time.  But, because turning and moistening equipment
was not available for production purposes, the windrows were riot
cared for.  This work should demonstrate the results of managing
windrows.
             The experimental plan was to follow refuse degradation
from the time the refuse was put into the digester until it had been
treated in a windrow for a period of two months.  The temperature,
oxygen and CO- concentrations in the refuse were monitored through
much of the study along with the physical and chemical parameters.
                                 180

    -------
             A sample of the raw refuse was taken  as it entered
the digester.  Part of the sample was analyzed and the rest was put
into 6 Fiberglas bags and placed in the digester.  The samples in
the bags were removed as required for analysis after 3 and 8 days
in the digester and after 1 and 2 months of windrow curing.
             Two windrows were constructed to represent two sets
of curing conditions.  One of the windrows was turned and moistened
as required.  The other was not turned or moistened.
             Figure 8 shows the temperatures, oxygen and CO- concen-
trations, and aeration rates in the digester.  This part of the work
coincided with the normal aeration rate study (Section H-7) and is
described therein.
             Table 7 shows the chemical analyses of the samples of
raw and digested waste.  The carbon content of the refuse dropped
211, whereas the nitrogen content dropped 13%.  The resulting C/N
ratio reduction was about 9% for the 8 days in the digester.  The
net BOD reduction was 10% after 3 days and 55% after 8 days.  COD
and volatile solids values also dropped during the 8 day digestion
period.
             The original plan of the experiment was to follow the
same refuse through the digester and windrow curing.  Unfortunately,
an equipment breakdown delayed the removal of the refuse under study.
The experimental plan was to have the refuse in the digester only for
                             -181-

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the typical 8 day detention time.  The refuse sample bags were
removed at 8 days and put into 2 windrows built with ground re-
fuse that had just come out of the digester after 10 days deten-
tion.
             Windrow #1 was made with compost as received from
the digester and had an initial moisture content of 30%.  Windrow
#2 was first moistened to 50% before being built.  Both windrows
were about 5 feet high.  Two of the original digester sample bags
were placed in each windrow at an elevation of four feet.  The
samples were not ground after treatment in the digester.  A sample
of the compost from each windrow was taken as it was made.  A zero-
time sample was analyzed and two sample bags were filled and placed
in each windrow at four feet elevation.
             Table 7 shows that the BOD reduction for this material
after one month in the windrow was 27% for windrow #1, but only 1.5%
for windrow #2.  After two months the BOD reduction was 66% for win-
drow #2.  The COD and volatile solids results for windrow #2 both
show reductions after 2 months.  Moisture was maintained well in the
windrow #2 sanple for 2 months.  The sample in windrow #1 lost moisture
after the first month and dropped to 33.8% at 2 months.
             Table 8 shows the results of analyses made of the material
from which the two windrows were built.  By contrast,  Table 7 shows
the analytical results of samples contained in Fiberglas bags.
                            -183-

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             The need for sufficient moisture content for curing in
a windrow to occur is indicated by the results in windrows #1 and #2.
Windrow #1 had only 30% moisture when constructed and 28% one month
later.  After two months the moisture had increased to 38%.  The BOD
reduction was less than 1% during the first month and only 7% at the
end of two months.  Windrow #2 moisture was about 50% during the
same time and produced a BOD reduction of 60% for the first month
and 80% by the end of two months.  Moisture content was evidently the
reason for the difference in the BOD reduction.
             Temperature, oxygen, and carbon dioxide were measured
in the windrows during the curing process.  The results are shown
in Figure 14.  The temperature and gas were measured in the center
of the windrows at elevations of 1, 2, 3, and 4 feet.
             Temperatures were generally higher in windrow #1 through-
out the period of observation.  This fact can be attributed directly
to the moisture content of each windrow.  After a rapid temperature
rise at all levels, windrow #1 cooled to temperatures ranging from
125°F to 145°F at 20 days.  These same temperatures were maintained
up to the latest readings made at 47 days.  The hottest part of the
windrow during this period was the lower half.
             The initial temperature build up in windrow #2 was less
than  that in windrow #1.   However, after 20 days, the temperature
in windrow #2 ranged from 125°F to 141°F which was about the same

    -------
                                       FIGURE
        TEMPERATURE,  OXYGEN,  AND CARBON DIOXIDE  IN  TWO  WINDROWS  - Aug.  28,  1969.
             Windrow #1
160
                        Windrow #2
                  Initial Moisture = 50%
                  Turned at 33 Days
       Initial Moisture = 30%
                                          4 Ft. Above Ground
   0    10    20    30    40
50    60    0    10

    Time in Days
20    30    40     50    60

    -------
as in windrow #1.  The interesting thing is that the upper part
of windrow #2 was the wannest at 20 days while the lower part of
windrow #1 was the warmest  at 20 days.
             Oxygen levels were consistently higher in windrow #1
than in windrow #2.  Windrow #1 was mostly aerobic while windrow
#2 was mostly anaerobic.
             Rainfall was 4.2 inches during the one week period
following the construction of the windrows.  This heavy rain appar-
ently penetrated the windrows.  The dry windrow (#1) was not moistened
much by the rain.  Water was observed flowing from the base of the wet
windrow (#2) after the rains.  It was felt that the turning of windrow
#2 to restore aerobic conditions would require too much time to be
practical.  The sample bags and temperature and gas probes would have
to be removed and replaced each time the windrow was turned.  The con-
ditions in windrow #2 where the sample bags were located were aerobic
and it was decided to leave the windrow as it was.  The windrow was
turned once at 33 days, but no improvement in oxygen content was noti-
ced.
             Foul odors conmon to anaerobic compost were observed upon
sampling the gas in windrow #2.  Nevertheless, Table 8 shows that decom-
position was much more extensive when the waste contained 50% moisture
as compared with 30% moisture.   This is shown by reductions in C/N
ratios, BOD and volatile solids values.  The significance of higher
                            -187-

    -------
temperatures resulting from the decomposition of refuse containing
only 30% moisture is not understood.  Better decomposition at the
higher moisture content is also shown by the greater oxygen demand.
It would appear that this curing experiment came very close to
anaerobic decomposition.  Apparently the best decomposition will
occur when the initial moisture content is less than 50% and/or the
windrow is turned frequently.
             When it became known that compost was not being oared
in large storage piles, a site was acquired for the curing of compost
in windrows.  The windrows were constructed by dumping compost from
the end of a moving truck.  This compost had been digested for 6 -
8 days.  Either water or digested sewage sludge had been used as
moistening agents prior to digestion.  The resulting windrows were
about 5 feet high and about 7 feet wide at the base.  No attempt was
made to turn or moisten these windrows.  No attempt was made to con-
duct a controlled study of these windrows because this was done pre-
viously on special experimental windrows conveniently located near
the laboratory.  However, they were observed periodically for about
1.5 years to estimate the results of unmanaged windrowing.
             Flies or rodents were never seen at the windrow site
although there was a distinct green compost odor after each hearvy
rain.
             A sample of compost was taken from within a 3 month
old windrow about 2 feet below the top surface.  It had the following
                             -188-

    -------
analysis:  carbon - 31.1%, nitrogen - 0.595%, C/N ratio - 52.3,

BOD - 58.9 mg/g, COD - 7724 mg/g, volatile solids - 68.7%, moisture

content - 48.4%.  These values are typical of compost which had

been digested for 8 days.  Thus, it appears that after 3 months of

unmanaged windrowing the compost had not cured much.  Temperatures

of curing compost were taken at various elevations in a 3 month old

and a 2 week old windrow.  The following compilation shows the results:


                TEMPERATURES AT STIPULATED ELEVATIONS, °F


       Elevation, Ft.           3 Month Windrow        2 Week Windrow

            1                          172                  180
            2                          167                  176
            3                          158                  176
            4                          140                  167


Temperatures in the 2 week windrow are about the same as those devel-

oped in the digester.  Even after three months the temperatures re-

mained sufficiently high to either kill or prohibit the growth of

pathogenic microorganisms.

             Subsequently, a windrow estimated to be 9 - 10 months

old was observed.  At a point 6 inches below the top surface, the

temperature was 99°F.  At a point 18 inches below the surface, the

temperature was 102°F.   The ambient temperature was 84°F.  The

compost at the surface of the windrow was very dry and had a distinct

grey color.   A very profuse growth of a yellow to cream colored fungus
                             -189-

    -------
peimeated the compost from 1/2 in. to a depth of about 6 in.  below
the entire surface.  Below this there was no more visible fungal
growth and the compost was very wet and dark.  A pleasant odor of
leaf mold was emitted when the surface of the windrow was disturbed.
             Windrows of 14 - 15 months old were deminished to only
1 1/2 feet high from their original height of about 5 feet.  The
color of the compost was dark black.  It had a faint earth-like odor.
Most windrows of this age were covered with a very heavy plant growth
thought to be Bermuda grass.
             From these observations, it appears that partially di-
gested compost can be cured in unmanaged windrows, if time and space
permit.  The only apparent nuisance was an odor of green compost after
heavy rains.  It must be recognized that results noted here may not
occur in other climates.
       9.  Bulk Density of Compost in Storage Pile
             Digested, reground compost was stored in large piles
for a period of time.  Some of the piles were as high as 35 feet and
it is likely that the compost at the bottom is highly compacted.
Information on the bulk density of compacted compost may be useful
to those considering the transporting of compost.
             Samples were taken March 10, 1969, from the lower part
of the storage pile.  Three samples were carefully collected in the
form of chunks and put in thin plastic bags.  The weight and volume
of the samples were calculated.
                             -190*

    -------
             The volume measurement was made with the compost chunk
in the plastic bag.  A 3500 ml. beaker was filled to the point of
over flowing.  The excess air was removed from the sample bag with a
vacuum pump and the bag immersed in the beaker causing an amount of
water equal to the volume of the sample to be displaced from the
beaker.
             The sample was removed, the beaker was again filled to
the point of overflowing, and the amount of water required noted.
The results follow:
Sample
Number
1
2
3
Weight,
grams
215.7
702.4
620.0
Volume
ml.
465
1406
1139
Bulk Density
Ib/yd3
780
836
920
             The average value of bulk density was 845 lb/yd^.   The
  bulk density values varied about +_ 9 percent so the resulting value
  is only approximate.  The moisture content within the storage piles
  has ranged from 30-45 percent.  Somewhat greater bulk density
  would be expected in the lower part of the storage pile because of
  compaction.
       10.  Process Evaluation - Miscellaneous
             Generally, the objective of evaluating the composting
  process was to determine what was accomplished.   When it was  shown
  that some part of the process was poor,  an alternative was  selected,
  and then it was evaluated.   The use of windrows  for curing  compost
                            -191-

    -------
in place of the original storage pile is an example of the accom-
plishments of process evaluation.  Various minor aspects of the
composting process were evaluated.
     a)  Effect of Refluxing on Waste Decomposition:  Several
investigators have shown that the seeding of refuse with special
microbial cultures or various natural inocula such as animal
manures failed to enhance the decomposition of refuse.  The return
of some freshly composted waste to a similar raw refuse might pro-
vide a population of microorganisms more specifically adapted to
the waste being treated than a population from another source.
Accordingly, decomposition might be enhanced or accelerated.  This
hypothesis was tested in one experiment.
           Approximately eight cubic feet of freshly ground raw
refuse was placed on a concrete slab and made as homogeneous as
possible by mixing with hand tools.  About one-half of a cubic
foot was subsampled and prepared for analysis to characterize raw
refuse.  A Fiberglas bag was filled with approximately one cubic
foot of raw waste and it was placed in the digester.  Refuse which
had been composted for 10 days was blended with the remaining raw
refuse on the concrete slab.  The mixture contained approximately
80 percent raw refuse and 20 percent compost.  A subsample was
taken for analysis to characterize the blend before further treat-
ment.  Two other Fiberglas bags were each filled with approximately

    -------
one cubic foot of blend and were placed in the digester adjacent
to the bag of raw refuse.  The three bags were left in the digester
for 13 days.  Detailed results reported previously1- ' were very in-
conclusive.  There is little to indicate that refluxing enhanced
the decomposition of refuse.
     b)  Nitrogen Leaching from Compost Piles:  The leaching of
nitrogen compounds from piles of compost to the soil may result in
serious pollution of ground water.  This is known to be a problem
in animal feed lots, for example.  Nitrogen compounds leaching from
the source to the underlying soil are converted to nitrate compounds
vfaich are very mobile in the soil.  Nitrates which are not assimu-
lated by living plants rapidly descend to the water table.  Water
thus contaminated and consumed by infants may give rise to the
disease known as infant methemoglobinemia, which can be fatal.
           The soil underneath the bulk storage pile was found to
be almost black in color suggesting a type of soil or possibly ground
water contamination.  Compost had been stored in this pile for about
1.5 years.  Soil samples were taken from two locations near the pile
and from two other places located at least 100 yards from the pile.
One sample was taken from each of the four locations about 2 feet
below the surface.  Samples were analyzed in triplicate for Kjeldahl
nitrogen by the same method used for refuse and compost.  The follow-
ing compilation shows the average Kjeldahl nitrogen contents of each
of four soil samples:
                            193

    -------
                       KJELDAHL NITROGEN, %


     Near Storage Pile                   100 Yards from Pile

          .0407                                  .0382
          .0534                                  .0153

           Although this was not an exhaustive study of contamin-

ation from compost piles, it does suggest a potential for nitrate

contamination of ground water from improperly stored compost.  It

is likely that compost stored in windrows would absorb more rain

water and thus reduce the leaching of nitrogen from compost.

     c)  Total Bacterial Counts:  Numbers of bacteria in refuse

as a function of treatment time might indicate the rate of refuse

decomposition.  It can be expected that the number of bacteria

will increase with time of treatment.

           Bacterial counts were made on raw ground refuse and

periodically on the same refuse as it was being composted.  Counts

were made of the bacterial population which decompose refuse rather

than those which are pathogenic as was done in another section of

this report.  Approximately one cubic foot of raw ground refuse

was obtained for this study.  Two grams of this refuse was commi*-

nuted with 200 ml of phosphate buffer in a Waring blender for 5

minutes.  The buffer consisted of 1 g each of K2HPO, and KH-PO.

per 1000 ml of distilled water.  The suspension was diluted and

plated on Bacto Tryptone Glucose Extract Agar (TGEA).  This agar
                           -194-

    -------
is not selective and therefore a great number of bacterial types

will grow on it  The agar plates were put into a 99°F (37°C) incu-

bator for 24 hours after which the colonies were counted.

           The original quantity of refuse was placed in a Fiberglas

bag which in turn was placed in the digester about 2 ft. below the

surface of the refuse.  The refuse was sampled periodically, plated

as described above, and returned to the digester for further treat-

ment.  Plates made from raw refuse and refuse composted for one-

half and one day were put in a 99°F incubator.  Plates made from

subsequent samples were placed in a 122°F (50°C) incubator.  These

temperatures generally correspond with those in the digester as

refuse digestion progresses.  Thus, the general mesophilic popu-

lation was determined on the untreated refuse and that which was

composted for one day.  The general thermophilic population was

determined on refuse which had been composted for more than one

day.  The following compilation shows that the general bacterial

population decreased with increased duration of composting.

               BACTERIAL POPULATION OF COMPOSTING REFUSE
IXiration of Composting, Days     Numbers of Bacteria per g, dry wt.

             0                             3.4 x 10?
             0.5                           2.5 x 107
             1                             1.7 x 107
             3.5                           1.8 x 106
             4                             2.6 x 105
             5                             2.9 x 105
             6                             2.0 x 105
             7.5                           2.0 x 104
                               195

    -------
             The significance of these results is not known.  Further
work is needed before it can be concluded that the number of bacteria
does actually decrease with the duration of composting.  It is possible
that the high temperatures developed in the digesters may have reduced
the numbers of organisms which were decomposing refuse.  It is gen-
erally known that a temperature of 131°F (55°C) restricts life to only
a few forms of thermophilic bacteria and fungi.  Temperatures in ex-
cess of 131°F greatly deminishes the activity of these thermophiles.
Biological activity above approximately 140°F  (60°C) is not known.
Nevertheless, composting is frequently accomplished at 160-180°F  (72-
82°C).  This implies a conversion from a biological process to a
chemical auto-oxidation process.
       11.  Arthropod and Rodent Control
             Control programs for arthropods and rodents are greatly
dependent on the animal's behavior and ecology.  Based on an sinimal's
habits, seasonal population changes, and life cycles, a practical
method of control may be devised.  Such a study was undertaken to deter-
mine these and other ecological characteristics of the fly population
associated with the Gainesville Compost Plant.  The fly population
was selected for this investigation because flies are present in
large numbers and are a short flight away from neighboring homes.  Ro-
dents and other arthropods are insignificant in numbers and are easily
controlled with pesticides.
                             -196-

    -------
       a)  Immature Flies;  Fly larvae are present in incoming refuse
in considerable numbers during the warmer months.  Many of these larvae
migrate from the refuse stored in the receiving area and cause annoy-
ance to workers, particularly those in the maintenance shop located
next to the receiving area.  Other larvae reach protected areas in which
they transform into adults.  A larval sampling program was conducted
from January - November, 1969.  The objective of this program was to
develop procedures for reducing the larvae population and the ensuing
adult flies.  To accomplish this objective, larvae which were brought
to the plant were identified as to species and the larval population
was characterized as to species composition.  In addition, a population
factor was developed.  This factor is a mathematical expression which
might be used for the estimation of the size of the incoming larval
population.  It is based on sampling a known fraction of the incoming
population in a one-foot-square box-like container.  The work described
in this report shows how the total incoming larval population was deter-
mined and how the population factor was used to estimate this population.
Table 9  shows larval types and counts from incoming refuse during the
period of January - November, 1969.
             In order to determine the credibility and value of the
population factor, it was necessary to establish the percentage of the
total population that was trapped in the larval sampling program and
the reliability of this procedure.  Visual observations indicated that

    -------
                            TABLE 9
              FLY TARVAE FOUND IN INCOMING REFUSE
                                      Species
                                           Percent Examined
Week Of:
Jan.


Feb.



March




April



May



June

July



Aug.




Sept.



Oct.



Nov.


12
19
26
2
9
16
23
2
9
16
23
30
6
13
20
27
4
11
18
25
1
8
6**
13
20
27
3
10
17
24
31
7
14
21
28
5
12
19
26
2
9
16
No.
Caught
0
4
2
0
0
1
0
0
0
0
12
130
102
78
131
285
614
1297
592
1629
2004
4554
3945
4387
4500
4482
3366
5669
5749
3534
4350
6116
4156
2621
1611
3597
3371
1638
620
212
173
18
No.
Examined
0
2
0
0
0
1
0
0
0
0
1
48
21
55
10
34
99
503
195
1013
330
697
1119
1543
703
1148
247
1041
2269
308
986
899
146
553
232
212
160
250
89
43
17
12
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                                    100.0
                                    100.0
** Plant
closed for repair June 15-30.
                     -198
                                             100.0
91.5
90.5
96.5
100.0
91.0
95.0
97.5
94.5
96.0
96.5
97.0
63.4
93.5
96.5
96.6
96.0
98.4
99.2
98.7
98.3
97.8
94.0
98.8
92.5
99.0
97.5
94.7
97.8
93.0
100.0
100.0
4.2
4.7
1.8


1.0
.4

.1
.9
.1
.4
.1

.9
1.2
.1
.1

.2
.1
1.3
.2


.7
.4
1.1
2.3







2.0
1.2
.6
1.0
7.5
6.0
1.6
1.9
1.2
.7
.1
.7
.5

1.3
.3
4.7


2.8




4.2
4.7
1.8

6.4
3.0

2.0
1.8
1.5
1.5
28.2
.3
1.8
1.5
.8
.2
.1

.2
.8
1.3
.2
.4
.5
.7
1.6






3.2
1.0
2.2
1.5
.9
.6
.3
.4
.1


.4
.4
.5
.6
.8
1.3
2.4
.3
1.7
.5
.7
.4
1.1
4.7



    -------
the majority of larvae escaping from the refuse were confined to the
partially enclosed area under the apron conveyor.  By sweeping this
area daily, it was possible to collect and estimate the number of
larvae migrating into this region each day.  The number of larvae was
calculated by taking a random sample from the sweepings, counting the
number per sample, and computing the total number of larvae collected
on the basis of the sample size and the amount of sweepings.  The
precision of this method was 6.00 +_0.2 larvae per gram when 20.0 Kg
of sweepings were sampled.  This means that this counting procedure
was quite precise.  Table 10  shows the calculated number of larvae
collected daily by sweeping under the apron conveyor, and also the
number of larvae trapped in the larval sampling program for that same
day.  These values are then compared to determine the ratio of number
trapped to the total number of larvae present.  These ratios are re-
corded as percent trapped in Table 10 .  The mean of these ratios was
used to determine the population factor.  This factor could be multi-
plied by the number of larvae trapped per day in the larval sampling
program to estimate the total number of larvae escaping under the
apron conveyor for that day.  A mean of the percent trapped of 0.996%
was calculated and recorded in Table 10 .  A standard deviation of
+0.284 indicates this factor is reasonably reliable.
             Larval migration from a pile of refuse could be expected
to occur randomly in all directions.  However, the construction of the

    -------
              TABLE 10



DETERMINATION OF POPULATION ESTIMATOR

Sweepings
(Kg)
19.05
27.0
1.80
18.4
10.7
14.5
9.82
17.4
16.3
22.2

Sample
(Gm)
976
1894
200
642
1076
1009
673
862
611
885

Larvae/
Sample
1741
2676
1500
3842
6855
4873
1993
1758
1796
3979
Number
Larvae
Collected
34,100
38,200
13,500
109,500
67,980
70,250
29,100
35,731
45,851
97,600
Number
Larvae
Trapped
487
452
114
986
297
602
238
411
490
1294

Percent
Trapped
1.41
1.17
0.84
0.89
0.44
0.86
0.82
1.15
1.07
1.31
                                              I = 0.996 ± .284

    -------
receiving area and the practice of refuse handling influenced larval
migration.  Refuse is depoisted toward the east wall for storage during
peak loading and is progressively removed from west to east by the
front-end loader.  Therefore, larvae migrating to the west are scraped
into the receiving hopper and they do not survive.  Likewise, north-
erly migration results in no survival since the ramp and paved areas
provide no protective areas for pupation.  Migration in an easterly
direction provides protection and larvae occur in large numbers along
the east wall of the receiving building.  A wooden retaining wall,
which is approximately three feet from the outer wall of the building,
provides harborage to these migrating larvae.  This area consequently
produces many adult flies.  It was difficult to sample and the number
of larvae present was an approximation based on visual observations
and numbers collected under the apron conveyor.  This factor was esti-
mated to be one-third of those under the apron conveyor for a given day.
             From Table 10, it appears that in the larval sampling pro-
gram approximately one percent of the larvae migrating into the apron
conveyor area were trapped.  Combining this factor with that calculated
for the number of larvae migrating under the east wall of the receiving
area, a population factor of 133 was obtained.  This factor, when
multiplied by the daily larval catch, should give some approximation
of the number of larvae migrating from the refuse into the protected
areas of the plant.  For example, Table 9  shows that 6, 116 larvae

    -------
were trapped the week of September 7.  Multiplication by 133 gives
an approximation of 813,400 larvae entering the plant during that one
week period.
        It appears that refuse should be cleared from the receiving
area as quickly as possible to minimize the number of larvae which
could otherwise migrate from it.  It is expected that the number of
larvae migrating from refuse is dependent in part on the length of
time a pile of refuse remains in the receiving area.  This hypothesis
was tested by comparing the number of larvae collected under the apron
conveyor during plant working hours with the number collected in the
same area during off hours.  This area was swept at the end of each
working day and again just prior to the next working period.  The
number of larvae was calculated as previously described.  Table 11
gives these results.  The number of larvae collected during off hours
when compared to the total number of larvae per day reveals that a
reduction of more than one-third of the total larval population could
be accomplished by clearing the receiving area of refuse at the end
of each day.
        Quite often refuse must remain in the receiving area and on
the approach ramp for several days.  When this occurs the number of
migrating larvae increases considerably.  These larvae migrate from
the refuse falling from the ramp to the pavement below.  On several
occasions the number of larvae was so great that the pavement appeared
white.  On one such occasion, the pavement was swept clean and the
larvae collected twelve hours later.   Their number was estimated
to be 60,000 larvae per day migrating from the ramp (east)  alone.
                             -202-

    -------
                                TABLE 11

            DETERMINATION OF NUMBER OF LARVAE ENTERING PLANT
                            DURING OFF HOURS
Sweepings
(Kg)
7.22
2.95
11.35
3.18
7.95
1.85
16.8
0.65
16.3
3.35
19.06
2.57
Sample
(Gm)
725
351
666
343
360
313
722
140
611
283
602
282
Larvae
Per
Sample
3400
3612
2508
2971
794
1961
1318
995
1456
2914
1992
2834
Time*
Interval
D
N
D
N
D
N
D
N
D
N
D
N
Number
Larvae
Collected
36,180
31,800
42,700
27,550
17,500
11,600
30,700
4,620
44,400
34,500
63,200
25,800
Total
Daily
Catch

67,980

70,250

29,100

35,320

78,900

88,900
Night Catch
Total Daily Catch
(%)

46.8

39.2

39.8

13.0

43.7

29.1
* D =  7:00 am  -  6:15 pm
  N =  6:15 pm  -  7:00 am
                                                            I = 35.7 ± 12.4
                                     -2S03-

    -------
        The majority of larvae that migrate from the refuse are third
instars and thus would require little external influence to develop
into adults.  This was demonstrated by a series of hatching studies.
Larvae were placed into empty cups and other cups containing 25 gm
of refuse debris.  Both types contained 100 larvae each.  The cups
were covered with cloth, secured with a rubber band, and placed under
the apron conveyor.  Adult flies emerged in 8 - 10 days.  Nine repli-
cations of each test gave a mean of 65.31 adult emergence from the
cups with nothing added, and a mean of 88.8% adult emergence from the
cups with debris.  These data indicate that a minimum of 65% of the
larvae which escape into the plant will emerge as adults and that if
these larvae migrate to the large amount of debris present under the
apron conveyor as many as 88.8% may be expected to emerge as adults.
Thus, it is concluded that refuse should be cleared from the receiving
area as quickly as possible.  To do otherwise will encourage a fly
problem.
        b)  Adult House Flies:  It was initially assumed that the
adult house fly population associated with the Compost Plant could
be estimated by sampling the fly population above the digesters.
A one-year study was initiated in January, 1969, to test the assump-
tion.  The methods and some results were given in the last interim
report^6).
                            -20k-

    -------
        The survey showed that the fly population of the plant cannot
be estimated from the  fly population of the digesters.  Figure 15
shows that the numbers of house flies do not always correlate with
ambient temperatures.  A sharp increase is recorded for the week of
May 4.  This may be partially attributed to the high moisture content
of the compost that week.  The plant was closed for repair the last
three weeks of June and no samples could be taken.  Upon resumption
of operations, a sharp reduction was observed in numbers of flies
caught.  These low numbers continued well until the latter part of
September when the daily catch began to increase.  It is assumed
that the low catch during the summer is due to high temperatures
in the digester building where the air temperature often approached
110°F.  Table 12 gives the average air temperature recorded on a
hydrothermograph placed above the digesters for several one week
periods.  These data demonstrate more clearly the increasing fly
population with decreasing average hourly temperature.
        A large number of house flies was observed around the
receiving area during the period of high indoor temperatures.  This
further demonstrates the unreliability of this sampling procedure
during the summer months for estimating the total adult house fly
population.  However, the procedure does show population trends in
the digester building.  It may be useful in studies of fly breeding
in the digester.
                            -205-

    -------
+AVERAGE WEEKLY LOW AMBIENT  TEMPERATURE  (F°)
                                                                    1^


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        AVERAGE NO.  PEE YLK RIBBON
                           -206-

    -------
                                TABLE  12

          EFFECT OF TEMPERATURE ON NUMBER OF ADULT HOUSE FLIES
                        IN THE DIGESTER BUILDING
Air Temperature Of Digester Building
Average Average Average Hourly
Week Of: Daily High Daily Low Temperature
Average
No. Flies
Per Ribbon
August 17
September 21
October 19
November 16
106.4
99.4
99.1
92.7
93.6
90.3
88.8
75.6
98.8
94.9
94.1
83.5
9.0
9.9
13.0
77.3
                                  -207-

    -------
        c)  Adult Fly Control:  An evaluation of several adult fly
control procedures was undertaken during the summer of 1969.  During
the summer months, the majority of adult flies were observed around
the receiving area and along the conveyor belt system, with relatively
few observed above the digesters and other areas of the plant.  Sweep
net catches in these areas indicated the vast amjority of these flies
were Phaenicia species.  They were considered a nuisance to plant
workers, in particular the pickers.
        During, and 30 days prior to, this investigation, the plant's
fly and roach control programs were suspended so that insecticide
residuals would exert little or no effect on the tests.  Six fly con-
trol procedures were evaluated.  Another procedure was discussed but
not evaluated.  Effectiveness of the control procedures was determined
by comparing fly counts made during the treatment period with counts
made during a prior period of no treatment.  The duration of pre-
treatment control sampling was 7 days; subsequent control durations
were 3 days.  Treatment periods were alternated with control periods.
        A 2' x 2' x 3' screen cone trap was chosen to sample the popu-
lations.  This method gave 24 hour sampling and therefore was not sub-
ject to hourly variations.  Fish heads were used to bait the traps
because they were readily available and they attract most species of
flies associated with refuse in this geographical area.  Each trap was
baited daily with one fish head which had "aged" for 24 hours at room
                             -208-

    -------
temperature.  Due to the operation of equipment during normal plant
operations, traps could not be placed in the receiving area or along
the conveyor belts.  However, the area behind the receiving building
proved suitable and two traps were placed in this area.  Counting of
flies was facilitated by placing the trap in a large plastic bag and
killing the flies with ethyl acetate.  The daily catch was recorded
as a sum of the catches of the two traps.
        Treatments and treatment procedures are described as follows:
            Sugar Bait:  A 0.5% D.D.V.P. sugar bait, obtained
commercially under the name Fly Bait, was applied at a rate of 400
grams per day.  This bait was distributed along the conveyor belt
system and under the apron conveyor  for seven days.
            Remove Larvae:  The number of adult flies could be re-
duced by removing or killing the larvae which escape into the plant
before they metamorphose to adults.  The area under the apron con-
veyor was cleaned and swept daily to remove the larvae which had
entered this area.  This area was chosen because the majority of
larvae enter the plant here and it is relatively easy to clean.  The
other main entrance for larvae, the east wall of the receiving area,
was not cleaned because this area was not accessible.  This method
of control has some advantages.  Because no pesticides are employed,
there are no dangers involved in working with poisons and there is no
problem of insect resistance.  Because the transformation of larvae
                              -209-

    -------
to adults takes approximately ten days under the existing conditions,



the area would not need to be cleaned every day to reduce adult: popu-



lations.  It may be assumed that a weekly cleaning would be just as



effective as daily cleaning.



            Malt Bait:  A 25% malt solution containing 1.0% D.D.V.P.



was included in this study because malt bait was reported in the



literature as being very effective at a Florida dump for the control



of Phaenicia.  Fifty ml were applied daily at four locations along the



conveyor belts for a one-week period.  This bait has several dis-



advantages:  (1) it is not available commercially, but must be pre-



pared by the user; (2) it must be stored under refrigeration; (3) it



costs more than sugar bait; and (4) its syrupy consistency makes it



inconvenient to work with.



            Fogging;   Fogging is not a highly recommended procedure



for effective control of adult flies.  However, because personnel at



tne Compost Plant at Johnson City, Tennessee, included fogging in



their fly control program, this method was investigated.  Fogging has



several disadvantages:  (1) it leaves no residue, thus killing only



a percentage of the adult flies present at the time of fogging;  (2) a



high concentration of insecticide is necessary to kill adult flies,



5% for fogs as compared to 1 - 21 for liquids; (3) initial cost of



fogger; and  (4) the necessity of trained personnel.



        It was observed that the adult blowflies, Phaenicia, left



the plant buildings at dusk and roosted in the grass immediately
                                -210-

    -------
surrounding the plant during the night.  Because  the  flies were con-
centrated in this relatively small area, it was concluded that fogging
the area at night would give the greatest chance  of success.  A 5.0%
Fenthion in No. 2 fuel oil solution was distributed by a portable hot
air swing fogger for three successive nights.
            Residual Spray-Dimethoate:  Because dimethoate is a widely
used insecticide for the control of adult and immature house flies,
it was chosen for this investigation.  A 10% dimethoate solution was
applied once with a hand sprayer at a rate of 2 gm/M  to the grassy
areas surrounding the plant used as roosting sites for Phaenicia.
            Residual Spray-Rabon:  Rabon is an effective larvacide
for house flies.  A 10% Rabon solution was applied at a rate of
2 gm/M^ in the same manner as described for dimethoate.
            Kill Larvae:  Killing larvae to reduce the number of
adult flies could best be accomplished by the application of a
chemical larvacide.  Due to the large amounts of  falling debris under
the apron conveyor, the application of a larvacide wouldjbe ineffec-
tive and, therefore, was not attempted in this study.
        Table 13 shows the effectiveness of each  control procedure.
The fly count reduction attributable to each treatment is obtained
by comparing the mean daily count during treatment with the mean
daily count during the previous control period.   In addition to the
usual pretreatment control, post treatment counts were used for the
evaluation of the fogging and sprays to determine residual effects.
The results follow:
                                 -211-

    -------
                              TABLE 13


                          ADULT FLY COUOTS*
Day Control
1 2343
2 2796
3 2268
4 979
5 1050
6 3456
7 824
8
9 X = 1959
10
11
12
13
14

Sugar Bait1 Day
1
2
3
4
5
6
7
, 1178 8
875 9
285 10
596 11
1041 12
490 13
107 . 14
X = 653
Control Sweepin;
1197
2316
1954
856
X = 1822 1055
908
667
! 353
1061
1775
1493
1437
1315
988
X = 1083
0.51 D.D.V.P. in sugar, daily


Area under apron conveyor swept daily
                            /

Number of flies caught per day

    -------
                        TABLE 13  (CONTINUED)
Day Control
1 1711
2 1397
3 . 'J985
4 % - 1698
5
6
7
8
9
10

Malt Bait?



360
514
641
1245
1467
597
1017
X= 831
Day
1
2
3
4
5
6
7
8
9
10

Control Fog^
1967
1949
1826
X" = 1914 . 561
661
561
627 X = 594
1581
1601
1811
X" = 1405
-1.0% D.D.V.P. in 25% Malt solution, daily
5.0% Fenthion in No. 2 fuel oil, days 4-6

    -------
                          TABLE 13  (CONTINUED)
Day Control
1 1437
2 1719
3 2241
4 X = 1799
5
6
7
8
9
10
11
12
13
14
15

Dimethoateb



28
13
37
18
64
49 X = 46*
112
287
170
393
811
1256
X = 287
Day
1
2
3
4
5
6
7
8
9
10






  Dimethoate @ 2 gms./M^, one application on day 4


  Rabon @ 2 gms./M » one application on day 4

*
  Mean of one week after treatment
                                                       Control         Rabon^


                                                        1677


                                                        1170


                                                        1410


                                                    X  = 1419           1056


                                                                        653


                                                                       1251


                                                                        734


                                                                 f-      949


                                                                        781


                                                                       1090


                                                                   3C  = 931

    -------
             Sugar Bait:   This  treatment  reduced the  adult  fly popu-
 lation by 66.7 percent.   The cost of one daily application was  about
 $0.50  plus 0.1 man-hour.
             Remove Larvae:  This  procedure  reduced the adult  fly
 population by 40.5 percent.  About 4 man-hours per week were  required.
             Malt  Bait:  This treatment reduced the population by 51
 percent.   The cost of one daily application was about  $0.70 plus 0.1
 man-hour.
             Fogging:  This treatment reduced the population by  69
 percent.   The cost of one fogging was about $5.00  plus one man-hour.
 The post treatment  counts show that  the residual effect of fogging
 is minimal  after  1  day.
             Residual Spray-Dimethoate:  Dimethoate reduced the popu-
 lation by  97.5 percent.   The post  treatment counts showed  a residual
 effect for more than 10 days after the single  application.  The  cost
 of one application was about $7.00 plus 0.5 man-hour.
             Residual Spray-Rabon:  This larvacide  reduced  the popu-
 lation by  34.4 percent.   The cost  of Rabon  treatment was approximately
 the same as  for dimethoate.
        The  study of adult fly control is not  complete.  Nevertheless
 it does show that adult flies can  be  controlled around waste treat-
ment facilities.   Furthermore,  the study emphasized the need for
background knowledge, both general and specific for the given plant,
 as a basis for fly control.  Spraying with  dimethoate  resulted in
                                -215-

    -------
the best fly control.  The need for good housekeeping programs
was also shown.  Although sweeping resulted in only 40 percent
reduction it must be emphasized that only a portion of the plant
was swept.  Therefore, good housekeeping practice is probably
more beneficial than these data indicate.
       d)  Other Fly Studies:  An investigation was undertaken to
determine the influence of moisture and extent of waste decompo-
sition on house fly breeding.  In this study compost of various
ages was tested at different moisture contents to determine the
effects on rearing house flies.  The compost used was taken from
the digesters between 12-24 inches from the surface.  The de-
sired moistures were obtained by adding tap water.  Fifty grams
(dry weight) of compost was placed in a one quart waxed cup with
100 eggs or 100 larvae (48 hours old).  The cup was then covered
with a piece of cloth which was secured by a rubber band.  CSMA
rearing medium at 66 percent moisture was used as a control.
             Table 14 shows the number of pupae formed.  Forty-
eight hour larvae will survive in compost of all ages and moisture
contents tested.  House fly eggs survived best in 60 - 75% moisture.
The age of the compost also influenced survival.  The final grind
reduced survival considerably but still showed 8.5% survival in the
finished product.  Further tests are planned in this area.  Another
test is planned in which the amount of sludge will be varied to
determine influence in breeding in the digesters and in the laboratory.

    -------
                                            TABLE 14


                  INFLUENCE OF MOISTURE AND AGE OF COMPOST ON HOUSE FLY SURVIVAL
•** Average Number of Pupae per 100 Larvae
3
-J
3
~!
~J . ;
3
1
1
T
"
1
1
-]
(48 Hours Old)
Time Composted — Percent Moisture
(Days) 30 45 60 75 90
0
1
3
5
10
10 */
0
1
3
5
10
10 I/
82.
59.
84.
76.
81.
82.
Average
0
0
0
0
0.
0
5 78.0
3 81.3
3 79.3
0 80.6
6 79.6
8 86.6
Number of
0.8
0
0
0
0
0
8-1.8
58.6
80.3
84.6
86.6
89.0
Pupae
16.5
1.3
21.2
3.1
3.1
0.3
81.6
33.5
86.3
91.6
90.3
90.5
per 100
43.3
13.8
40.8
39.0
25.1
8.5
67.0
50.3
80.. 1
70.1
58.5
80.3
Eggs
5.6
0
0.8
0.6
0.3
0
Control
99.1
92.5
90.1
92.6
92.6
92.6
80.6
87.6
78.6
69.8
80.5
88.3
            I/  Length of  time in digester tanks

J
 *           2_/  After passing through final grind (Finished Product)
                                                •w-

    -------
             A single test was performed to determine if larvae
entering the plant in the refuse could survive the grinding process.
Third instar larvae were passed through the grinder and some living
larvae were recovered.  During this period the primary grinder was
not in operation and only the secondary grinder was in use.  This
experiment cannot be interpreted quantitatively, but it does show
that some larvae will survive  the grinding process.  These larvae
may proceed to the digesters where they may develop if conditions
are suitable.
       12.  Public Health Aspects of Composting
             The objective of the public health evaluation was to
delineate possible health hazards associated with high-rate compost-
ing processes.  Potential health hazards are created by pathogenic
microorganisms in refuse and compost and those in aerosolized form
in work areas.  Potential health hazards also are created by arthro-
pods and rodents which are attracted to wastes and are vectors of
diseases afflicting man and animals.  Control of arthropods and ro-
dents was reported in Section H-ll.  Additional hazards include non-
viable aerosolized matter which could cause lung diseases and noise
which could damage the hearing of plant personnel.  Methods for the
assesment of public health hazards were presented in Sections E and F.
       a)  Microbiolpgica.1 Evaluation:  The purpose of the microbio-
logical evaluation was to determine whether microorganisms associated

    -------
with refuse and compost constitute health hazards, real or potential.
Health hazards to the consumer are inferred by the detection of certain
microorganisms "which indicate the presence of pathogens in the compost
product.  Health hazards to plant personnel are manifested by physical
examinations and by the detection of pathogenic microorganisms in the
air breathed by workers.  The public health quality of compost was
evaluated by periodic examination for fecal colif orms, Salmonellae,
and by special die-off studies.
             Fecal coliform  bacteria were used as indicators of
pathogenic microorganisms.  The assumption was that the destruction
of coliforms by composting would also indicate the destruction of
pathogens.  Consequently, the numbers of fecal coliforms in compost
was compared with the numbers of the same organism in raw refuse.
Table 15 shears the average fecal coliform indices in refuse and compost
over an extensive period of time.  Coliform bacteria readily survived
in composting refuse.  The length of treatment by composting varied
from 3-10 days.  As discussed in Section H-6 the survival of coliforms
was more dependent on the moistening agent than on the length of treat-
ment.  When water was used to moisten raw ground refuse, the coliform
population in the resulting compost remained stationary or increased
relative to the original population.  By contrast, when sewage sludge
was used, the coliform population in the resulting compost decreased
for the most part.

    -------
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             Regardless of the effect of the moistening agent
the coliform bacteria survived the composting process.  This might
indicate that pathogenic microorganisms also survive composting,
although this possibility was discounted in subsequent work.
             Salmonella bacteria were also used as indicators
of pathogen destruction.  Indication of the destruction of patho-
gens is based on the same principle as that in the coliform method
except that the Salmonellae  were not determined quantitatively.
Samples of raw refuse and compost were examined for the presence of
Salmonella .  A total of 144 samples of raw refuse, 101 samples of
plant effluent compost, and 2 samples of old stockpiled compost
were examined for the presence of Salmonella .  This organism was
found in three samples of raw refuse and in two samples of compost
which was cured for an estimated duration of 1 year.  It was never
found in samples of compost which was subjected to digestion only.
Digested sewage sludge was used for moistening refuse when Salmonella
was detected in two samples of refuse.  Raw sewage sludge was used
when Salmonella was detected in one sample of refuse.  No sludge
had been added to refuse when it was processed a year prior to sampl-
ing for Salmonella in the resulting old compost.  The finding of
Salmonella in this old compost is inexplicable.
             The meaningful use of Salmonella as an indicator of
pathogen destruction by the stipulated method is very doubtful
                               -22Z-

    -------
inasmuch as it was seldom found in raw refuse.  Thus, the failure to
find Salmonella in effluent compost does not indicate that it was
killed during the composting process.  Its use in another method
whereby refuse is intentionally seeded with Salmonella could be mean-
ingful .
         Composting,  besides accomplishing a satisfactory amount of
 waste stabilization, must also accomplish waste sanitation.   'This  is
 particularly important when refuse is  amended with raw sewage sludge.
 The destruction of pathogenic microorganisms would indicate  that waste
 has been sanitized.   However,  it is extremely difficult to detect
 pathogenic organisms in solid wastes because of their presence in  very
 small numbers and because the presence of other microorganisms in
 vast numbers obscures the pathogens.  The detection of pathogens in
 compost would show  that they survived the composting process or
 that they were reintroduced.  Failure to detect pathogens in compost,
 on the other hand does not necessarily show that they were killed.
 Failure could mean  that either  the particular sample contained no
 pathogens or if  it  did, they might have been  overgrown by other
 microorganisms during the duration of the test  procedure.  This
 suggested the use of an assay procedure  for the detection of micro-
 organisms which  might indicate  the presence  of  pathogenic micro-
 organisms.  The  selected  assay  procedures will  detect  the indicator
 organisms  in the presence of large numbers  of extraneous  organisms.
                                -122-

    -------
However, it is questionable whether the indicator organisms truly
indicate the presence of pathogenic organisms.  Furthermore, the
detection of coliforms and Salmonella as indicators had doubtful
meaning as discussed above.
        Table 16 shows the plate counts before and after treatment for
the various organisms tested.  In general, the results show that high-
rate  composting has a pronounced adverse effect on the pathogenic bacteria
evaluated under this study.  Escherichia coli, a non-pathogenic bacterium,
survived 12 days of composting.  In only one experiment, in which E_. coli
was exposed for 4 days, was there any evidence that its population was
decreased.  The precision of this counting procedure is usually one
order of magnitude.  Thus, a population reduction in 12 days from
        8              8
3.1 x 10   to  1.0 x 10  is not significant.  It is interesting to note
that whereas the population of E_. coli remained stationary in 3 of 4
experiments, previous work showed that the numbers of coliforms were
reduced when refuse was supplemented with sewage sludge.  The coTitorm
bacteria consists of a group of species of Escherichia, including E_. coli
and Aerobacter.  Apparently, the reduction of coliforms is attributable
to the reduction of species other than E_. coli which remains approxi-
mately stationary.
        Salmonella typhimurium was killed in one day when exposed to
composting refuse.  When incubated in the laboratory at 99°F in the
                              -223-

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                                                   -225-

    -------
presence of ground refuse the population remained stationary.  S_.
paratyphi was killed in one day if a temperature of approximately 131°F
is attained.
        Bacillus stearothermophilus is one of the most heat tolerant
organisms known to exist.  It is frequently used to test the operation
of autoclaves and other sterilizing equipment.  Vegetative cells of
this organism were readily killed in one day in a composting environ-
ment, although a population of spores were not completely reduced in
two days.
        On the basis of these data it appears that high rate composting
is likely to kill pathogenic organisms in two days.  It must be realized
that both the temperature and the duration of time that organisms are
exposed to heat are important factors in producing thermal death.
Therefore, refuse which is not heated adequately will harbor living
pathogens.  It was not an objective of this work to develop all in-
clusive time and temperature relationships for thermal death since this
has been investigated by others.  However, it does appear that high rate
composting sanitizes refuse more quickly than windrow composing.
        b)  Airborne Particulate Matter:  The air in dusty areas of
the plant was sampled for particulate matter as an indicator of poten-
tial public health hazards.  Particulate matter was determined with
both a standard high volume sampler for total particulates and
with an Andersen Sampler for particle size distribution.  Both viable
and non-viable particulate matter was determined with the Andersen
Sampler.
                             -226-

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        An  8 x 10" Fiberglas filter was used in the high volume sampler


which is 99% effective  in removing particles ranging in size from 0.1


micron and  larger.  The flow rate of air through the instrument was


39.2 cubic  ft. per minute.  The instrument was placed in the plant


midway between the primary and secondary grinders.  It was operated

for 4 3/4 hrs. in the afternoon of October 17, 1969.  Total particulate
                                                       •z
matter was  3793 micrograms per cubic meter of air  (yg/m ).  This value

is extremely high as compared with acceptable ambient air values

reported in Air Quality Criteria for Particulate Matter (issued February,

1969, by the National Air Pollution Control Administration).  Adverse

health effects were noted when the annual mean level of particulate

matter exceeded 80 yg/m , visibility reduction to about 5 miles was

observed at 150 ug/m , and adverse effects on materials were observed

at an annual mean exceeding 60 yg/m .


        Air was sampled for viable particles with a Model 0604 Ander-


sen Sampler (Andersen Samplers and Consulting Service, 1074 Ash

Avenue, Provo, Utah, 84601).  The sampler was used at various areas

in the compost plant where suspended dust was obvious.  The sampler

separated microorganisms into six categories according to size and

aerodynamic properties.  The microorganisms were impinged on the

surfaces of agar contained in six Petri dishes.  Tryptone-Glucose-

Extract Agar was used for the detection of general airborne micro-

organisms, Potato Dextrose Agar for fungi, and Brain-Heart Infusion
                               -227-

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Agar for pathogenic bacteria.  The agar-impinged organisms were
incubated for 18 - 24 hours until small colonies developed, at
which time they were counted.
             Numbers of viable particles collected from the air in
various areas on the plant premises are reported in Table 17. The
data clearly show that two areas in the plant contain large numbers
of aerosolized microorganisms at the time of sampling.  By comparison,
the laboratory air was relatively clean.  The data indicate the pre-
sence of broad groups of microorganisms such as bacteria and fungi,
but do not indicate pathogenicity.  According to the manufacturer of
sampler, any particle 5 microns or less in diameter can penetrate the
lungs and is therefore hazardous.
             Particle size distribution (weights of particles of various
sizes) was determined at two locations in the plant with the Anderson
sampler.  Two determinations were made on September 9, 1969, at the
operators platform.  Duration of sampling was one hour in the morning
and 30 minutes in the afternoon.  One determination was made on
September 9, 1969, at the picking table.  The duration of that
sampling was one hour.  Particle weights were determined by weighing
the glass collection plates before and after exposure and by sub-
tracting the two values.
Table 18 shows that both plant areas are extremely dusty.  It
is generally recognized that particles having a diameter of 5y or less
can penetrate the lungs.  Lung penetrability increases as particle
                              -228-

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Agar  for pathogenic bacteria.  The  agar-impinged organisms were
incubated  for  18  -  24 hours until small colonies developed,  at
which time they were counted.
        Numbers of  viable particles collected from the  air in
various areas  on  the plant premises are reported in Table 17.  The
data  clearly show that two areas in the plant contain large  numbers
of aerosolized microorganisms at the time of  sampling.  By comparison,
the laboratory air  was relatively clean.  The data indicate  the pre-
sence of broad groups of microorganisms such  as  bacteria and fungi,
but do not indicate pathogenicity.  According to the manufacturer of
sampler, any particle 5 microns or  less in diameter can penetrate the
lungs and  is therefore hazardous.
        Particle  size distribution  (weights of particles of  various
sizes) was  determined at two locations in the plant with the Anderson
sampler.   Two  determinations were made on September 8,  1969, at the
operators platform.  Duration of sampling was one  hour  in the morning
and 30 minutes in the afternoon.  One determination was made on
September  9, 1969,  at the picking table.  The duration  of that
sampling was one  hour.  Particle weights were determined by weighing
the glass collection plates before  and after exposure and by sub-
tracting the two  values.
        Table 18  shows that both plant areas are extremely dusty.  It
is generally recognized that particles having a diameter of  5y or less
can penetrate the lungs.  Lung penetrability increases as particle
                              -229 -

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size decreases from 5y.  Thus, particles collected on stages 3-6
are especially hazardous to exposed personnel.  All values exceed the
air quality criteria set by the National Air Pollution Control Admin-
istration  (NAPCA).  Most values greatly exceed these criteria.
        Even though only a few analyses were made, one can readily see
that the atmosphere near the grinders and the picking table is very
dusty.  Thus, even though the reported values might be 2 - 3 tijnes
higher than typical values, a definite hazard is still manifested.
Data showing particulate matter in ambient air greatly exceed the
NAPCA air quality criteria for maximum tolerable levels.  Therefore,
it is concluded that the atmosphere surrounding the primary and
secondary grinders, the operator's platform, and the picking table
is a potential hazard to the health and well-being of exposed
personnel.
        c)  Parasitological Analysis of Compost;  The presence in
compost of viable eggs and mature forms of intestinal parasites
would be evidence of insufficiently sanitized compost.  Samples of
sewage sludge, ground refuse, and compost were examined for intestinal
parasites.  Samples were taken in October, 1968, and in January, March,
and October, 1968.  They were sent to the Division of Research and
Development, Solid Waste Office for examination.
              As expected, sewage sludge either raw or digested
contained intestinal parasites.  Raw ground refuse was never found
to contain eggs or mature forms, but one sample of digested refuse
                              -232-

    -------
which was not moistened with sludge did contain rhabditiform larvae
of hookworm or Strongyloides.  Two ova of Hymenolepsis diminuta were
found in one sample of digested refuse which had been supplemented
with digested sludge.  It must be emphasized that the analytical
methods used in the performance of this work could not be distinguished
between living and dead parasites.  However, it is possible to distin-
guish between intact and decomposed organisms.  It was assumed, there-
fore, that the intact organisms survived composting and decomposed
organisms did not.
             It was strongly indicated that the curing of compost in
windrows killed intestinal parasites.  Ova of Ascaris lumbricoides and
Hymenolepsis diminuta and hookworms or Strongyloides larvae were found
in compost which had cured in windrows for up to 3 months.  However,
none of the windrows were turned or otherwise managed.  Those parasites
that apparently survived 3 months of curing were found in compost which
was collected within 3 inches of the surface.  Although it is not known
what effect windrow turning would have on parasite survival, it is
likely that survival time would be reduced.
       d)  Physical Examinations:  All plant workmen and most admin-
istrative personnel were given periodic physical examinations to deter-
mine clinical manifestations associated with exposure to solid wastes.
The plan was to have each person examined before any exposure to
solid wastes and then periodically thereafter.  Comparison of the
                               -233-

    -------
findings before and after exposure might reveal certain health
hazards.  However, rapid personnel turnover and inherent short-
comings of clinical studies made it difficult to make a good
comparison.
             Seventeen employees were given complete physical exam-
inations.  Twelve employees were reexamined about one year la.ter.
No changes were noted in their general state of health. Thirty
Mantoux skin tests were given; three were positive indicating that
they were exposed to tuberculosis.  One of the positive reactors
gave a positive reaction prior to any exposure to solid wastes.  It
is not known whether the other two positive reactors were previously
positive.  All of the seventeen histoplasmin skin tests were negative.
             The accident record attributable to solid waste handl-
ing has been good with two individual exceptions.  Table 1$ shows the
frequency and types of injuries.
       e)  Noise;  Sound level determinations were made on two occa-
sions in the vicinity of all pieces of heavy equipment in the plant.
The surveys were made when the Jay Centriblast shredder was in use
and then again after it was replaced with a Williams shredder.  Detail-
ed results were given in two previous reports ^ '  .  In summary, the
most hazardous piece of machinery regarding noise is the primary
shredder.  The hazard results not only from the high level of noise
generated, but also from the close location of the laborers to this
                              -234-

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                               TABLE 19

                        SUMMARY OF WORK INJURIES
Date of
Injury
6/25/68

11/5/68
11/19/68

7/24/69

8/8/69
10/1/69
Time
Lost
158 days

39 days
3 days

1 day

1 day
1 day
Age of
Employee
40

21
47

17

33
19
Job
Classification
Maintenance

Grinder Oper-
ator
Welder

Salvage Labor-
er
Laborer
Truck Driver
Type of
Injury
Fractured bone
in arm
Cut tendons in
foot
Fractured bone
in toe
Twisted knee

Sprained ankel
Cut hand
            Nineteen minor injuries such as cuts and bruises
No lost time.

            Total days lost because of injury     -    203
            Total work days, approximate          - 41,600
            Percent of work time lost, approximate- 0.48
                               -235-

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source of noise.  These laborers are exposed to sound levels  of



100 - 102 dbA.  The maximum exposure time to this intensity allowed



by the Safety and Health Standards for the Walsh - Healey Act is



1.5 - 2.0 hours per day.  Because these laborers are exposed  for



longer periods of time, they were issued ear plugs for their  protec-



tion.
                             -236-

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                                  REFERENCES
 1.  1967 Interim report.  Gainesville [Florida] Municipal Waste Conversion
       Authority, Inc.   (The information in references 1, 2, and 3 is
       published in:  Gainesville compost plant; an interim report.
       Cincinnati, U.S. Department of Health, Education, and Welfare, 1969.
       345 p.)

 2.  Interim report, January-April 1968.  Gainesville Municipal Waste
       Conversion Authority, Inc.

 3.  Interim report, May-August 1968.  Gainesville Municipal Waste Conversion
       Authority, Inc.

 4.  Interim report, September-December 1968.  Gainesville Municipal Waste
       Conversion Authority, Inc.  Unpublished data.

 5.  Interim report, January-April 1969.  Gainesville Municipal Waste
       Conversion Authority, Inc.  Unpublished data.

 6.  Interim report, May-December 1969.  Gainesville Municipal Waste
       Conversion Authority, Inc.  Unpublished data.

 7.  Tentative methods of analysis of refuse and compost; appendix A.  In
       American Public Works Association.  Municipal refuse disposal.  2d
       ed.  Chicago, Public Administration Service, 1966.  p.375-399.

 8.  American Public Health Association, American Water Works Association,
       and Water Pollution Control Federation.  Standard methods for the
       examination of water and wastewater; including bottom sediments and
       sludges.  12th ed.  New York, American Public Health Association,
       Inc., 1965.  769 p.

 9.  Official methods of analysis.  10th ed.  Washington, Association of
       Official Agricultural Chemists, 1965.  957 p.

10.  Willis, H. H.  A simple levitation method for the detection of
       hookworm ova.  Medical Journal of Australia, 2:375-376, 1921.

11.  Ritchie, L. S.   An ether sedimentation technique for routine stool
       examination.   Bulletin of the U.S. Army Medical Department, 8:326-
       330,  1948.

12.  Jann, G. J., D. H. Howard, and A. J. Salle.  Determination of
       completion of composting.  Applied Microbiology, 7:271-275, 1959.
                                   -237 =

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