INTERNATIONAL

"FULL SCALE PILOT RESULTS: COMPOSTING WASTEWATER SLUDGES USING AGITATED-BED SYSTEM"

by Geoffrey A Kuter, Ph.D.; Lewis M. Naylor, Ph.D.;

and Paul Gormsen, P.E.

presented at

WATER POLLUTION CONTROL FEDERATION ANALYTICAL TECHNIQUES/RESIDUALS MANAGEMENT

SPECIALTY CONFERENCE ATLANTA, GEORGIA

APRIL 1988

International Process Systems Lebanon,Connecticut 06249 (203)642-6670

Fuu SCALE PILOT RESULTS: COMPOSTING WASTEWATER SLUDGES USING AGITATED-BED SYSTEM

GEOFFREY KUTER, LEWIS NAYLOR, AND PAUL GORMSEN

Since the pioneering work done at Beltsville in the early 1970's, composting has become widely accepted for treating municipal wastewater sludges in this country. In 1987, over 100 composting facilities were in operation in the United States. Whereas early facilities most often employed the Beltsville aerated static pile, about half of the new facilities under construction are in- vessel types ( 1 ). Vessel composting systems have generally been recognized as offering considerable advantages in process control and in automated operations. However these systems all too often have been plagued with mechanical complications and associated operational difficulties.

This paper reports on studies performed to document the composting of municipal wastewater sludges in a vessel system that has been in operation since January 1986 processing animal manures for the bagged compost market. The quantitative data collected during these full scale pilot studies with a variety of sludges is being used to design composting facilities for a number of communities in the Northeast that are considering vessel composting systems. In addition, observations made during these studies provide a basis for direct comparison with other types of composting systems in operation in this country.

MATERIALS AND METHODS - The composting facilities used in the pilot studies are located at Earthgro Inc., Lebanon, CT. The composting technology used is the proprietary property of International Process Systems (IPS) Inc. The IPS system is a forced air, agitated bed, vessel system.

Two facilities used in these studies consist of four, rectangular concrete bays 6 ft wide, 6 ft deep and 180 ft in length. Materials to be composted are mixed with appropriate bulking agents and loaded using a small front end loader in one end of each bay. The composting mass is moved down the length of the bay by a mechanical agitator that travels along steel rails mounted on the concrete bay walls. As the agitator moves through the mass the compost is agitated and and conveyed 10 to 12 feet down the bay. After 15 to 18 passes the material will have travelled the 180 ft distance and is discharged from the bays as finished compost. With each pass of the machine a space is provided at the input end of each bay for a new charge of material.

Operation of the agitator is automatic and an operator has not

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been agitator is transferred from bay to bay by a motorized trolley.

required to be present while the unit is in operation. The

Forced aeration is provided by a series of blowers mounted along the bays. Each bay has five distinct aeration zones, each zone aerated by a single 3 hp blower. Air is delivered upward through perforated piping set in a gravel base. Each blower provides between 600 to 900 cfm of air equal to about 10 cfh per ton of sludge solids. Blowers were regulated during the study by timers adjusted by manual measurements of compost temperature. Timers typically were operated at less than 50 % time on.

Because each bay is a separate composting vessel, the pilot studies were performed in one bay without disturbing on going composting of animal manures. During the pilot studies studies the agitator was operated through the bay once per day, 5 or 6 days p,er week and compost retained in the vessel for 18 to 21 days.

Two distinct studies were carried out with municipal waste water sludges. The first was performed in the fall of 1986 using the first composting facility. This study utilized dewatered sludges generated from five communities in eastern Connecticut: Norwich, Windham, New London, Killingly, and Groton. The sludge from the city of Norwich was anaerobically digested. All other municipalities provided a mixture of primary and waste activated sludge. The sludges were delivered by each participating community over a period of about 30 days. Sludge was delivered sequentially from each community and care was taken to process each contribution separately.

The second, nearly identical facility at the same site. This study was performed with a Zimpro sludge from the City of Springfield, Massachusetts.

second study was performed in the fall of 1987 in a

The procedures used in both studies were identical. However in the second study, a larger agitating machine was used and thus a greater quantity of material loaded into the bay each day.

The sludges were dumped directly from delivery trucks (municipally owned dump trucks or private roll-off containers) into the enclosed mixing area of the facility. In order to prepare an appropriate mixture for composting, the sludges were mixed with a bulking agent. For the great majority of the project sawdust was used exclusively. However, toward the end of the first study, sludge was mixed with leaves and chipped waste brush.

Sludge and bulking agent were mixed using a small front-end loader with a cubic yard bucket. From the mixing area the sludge/ bulking agent mixture, hereafter referred to as the input mixture, was loaded directly into one of the four bays of the facility.

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Each truckload of sludge was sampled and samples were pooled and one or two bulk samples were generated for laboratory analysis. Samples of the input mixture and the output compost were taken daily and bulk samples created in a similar manner. All bulk samples were analyzed for % dry solids (% DS), % volatile solids (% VS), pH, total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3- N), phosphorus, potassium, and various heavy metals at a private state certified laboratory (Eastern Aquanalysis, Brooklyn, CI'. In addition, samples of sludge, input mixture and output compost were analyzed for % DS on site (constant weight at 110 C).

The total wet weight of sludge in each delivery was known from the weight receipts provided from the haulers. The quantities (cubic yards) of bulking agent used were determined by counting the number of buckets used. Bulk density of the bulking agent, input mixture and output compost was also determined periodically by filling and weighing a cubic foot box. Care was taken to measure the quantities of input mixture placed in the bay and the quantity of the output compost over the course of the demonstration. A materials balance was determined using the dry solids and bulk density measurements, and the volumes and the wet weights.

Temperatures in the compost in the bay were measured periodically. Measurements were taken with a three - foot long thermocouple probe at two depths; six inches to one foot and three feet from the compost surface. On the basis of the temperature data, adjustments were made to the timers that regulated the blowers that provide aeration from the floor of the bay.

Sludges from five Connecticut towns

A total of 131 wet tons of wastewater sludge was delivered to the facility for composting. Results of the laboratory analyses of the sludge samples are presented in Table 1. There was considerable variation among the sludge delivered from the five communities. volatile solids went from 68 % in the digested Norwich sludge to 83 % in the Windham sludge. All sludges were slightly acidic to neutral; pH ranged from 5.6 to 7 .3 . The nitrogen content (TKN) ranged from 5.6 to 9.2 % ; the ammonia nitrogen was relatively low in all samples and accounted for less than 25 % of the total nitrogen content.

For example, the

The concentrations of metals varied quite widely among the communities. With the exception of copper and mercury, the Windham samples had the highest levels of metals. The levels of cadmium and lead in particular are well above those generally recommended to qualify f o r land application and skew mean values upward. The Groton sludge was, in general, the cleanest.

Sawdust was used as a bulking agent for most of the trial (118 wet tons of sludge). The quantities of sludge provided by each

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municipality and the amounts of sawdust used are summarized in Table 2. The amount of sawdust per ton of sludge was changed over the course of the study. The ratio of sludge to bulking agent (w:w) ranged from 1 : 0.6 to 1 : 1.3.

Due to different quantities of sawdust used and to the variation in the dryness of the sludges and sawdust, the input mixtures also varied in their % dry solids (Table 2 ) . For example, the mixture prepared from the sludge obtained from New London was only 31 % dry solids in contrast to the mixtures prepared from sludge from Groton and Windham (39 % dry solids).

The results of laboratory analyses of the input mixtures are given in Table 3. Dry solids results presented in Tables 2 and 3 differ slightly. The values in Table 2 are means of daily samples whereas those given in Table 3 are from single composite samples. As expected, after mixing with the sawdust there was a marked increase in volatile solids and a decrease in nitrogen, phosphorus, and metals in comparison with the sludge (Table 1).

Table 2 gives the results of the laboratory analyses of the samples of output compost. The variable that showed the most consistent change during composting was the percent dry solids which increased from a mead of 35 to 53 %. The expected decrease in the volatile solids was less pronounced. In addition, there was an increase in pH for samples from all but one of the five communities. The concentration of total nitrogen, and in particular ammonia nitrogen, decreased. However, the concentrations of phosphorus, potassium and various metals did increase as would be expected with composting. The concentration of metals is relatively slight in relation to the dilution obtained 'with the addition of the bulking agent and metals are considerably lower in the output compost than in the sludge. There is considerable mixing and movement of the compost within the bay by the agitating machinery and thus direct comparison of input and output town by town does not always follow the overall trends noted above.

Table 4 gives a summary materials balance obtained with the sludge from all five communities. Values are either totals or means of those presented in Table 2. For example, a total of 118.2 wet tons of sludge was mixed with 90.4 wet tons of sawdust to produce a mixture of 208.6 tons. The mean % dry solids of the sludge was 17.0 . The input mixture averaged 35 % dry solids and the output compost averaged 50.4.

Losses in the wet weight, dry weight and cubic yards of input mixture are also given i~ Table 4 . The loss of 73.3 tons wet weight was equal to 35.2 % of the total input mixture. The volume reduction was equal to 28.7 % of the input.

The data shown in Table 4 include a very wide variation in operating conditions and includes both anaerobically digested and non-digested sludges. Input mixtures with a dry solids of 31.3 % were included along with those entered at 38.8 %. Output compost

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at 43.6 and 45 % dry solids were averaged with those at 51.8 66 % dry solids.

and

In comparison, data presented in Table 5 summarizes results obtained with two only towns (Killingly and Groton) and include significantly less variation. The sludges were nearly equal in dry solids and averaged 17.8 %. Approximately one ton of sawdust was used per wet ton of sludge to produce an input mixture of 36.5 % dry solids. During this period an output compost with a mean of 58.9 X dry solids was obtained.

Daily Inputs and Outputs

The data in Table 4 summarizes results obtained with sludge from all five towns over the first 33 days when compost was loaded into the bay. input mixture are given in Table 6. A mean of 6.3 wet tons (11.5 cubic yards) of input mixture was loaded into the bay each time. The input mixture consisted of an average of 3.6 wet tons (.6 dry tons) of sludge and 2.7 tons of sawdust. A mean of 4.7 tons (8.2 yards) of compost were generated each day.

These same data expressed per daily load of

The sludge in Figure 1. Again these data are based on the total of 118 wet tons of sludge obtained from all five towns. For each wet ton of sludge .8 tons of sawdust was consumed and a total of 1.3 tons of output compost generated.

data in Table 6 are further expressed per wet ton of

In comparison, sludge from Killingly and Groton was mixed with sawdust at a rate of 1.1 ton sawdust to 1.0 wet ton of sludge. During this portion of the demonstration 2.7 wet tons of sludge were loaded into the bay per day. A daily mean of 3.4 wet tons of compost was produced each day. this amount was thus equal to about 1.3 tons per ton of sludge input.

Bulkinq Agent; Leaves and Chips

At the end of the demonstration one load of anaerobically digested sludge obtained from the city of Norwich was mixed with leaves and chips derived from waste brush and trimmings. This was a very heterogenous mixture as the leaves were partially compacted and difficult to handle. In addition, the chips were old and contained noticeable quantities of soil.

Table 7 shows the results obtained with sludge mixed with the leaf and chip mixture. % dry solids) was mixed with 6 . 3 tons of chips and 2.0 tons of leaves to yield an input mixture of 32.1 % dry solids. An output compost with a mean of 54 X dry solids was obtained. During this portion of the demonstration a mean of 3.6 wet tons of sludge was processed per day.

A total of 12.6 wet tons of sludge (17

Temperature

Temperatures in the compost were routinely monitored to regulate

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blowers which provided aeration. Attempts were made to insure that temperatures in excess of 55 C would be obtained and timers regulated to provide minimal aeration. Figures 2, 3, and 4 show temperatures measured on three consecutive days when the entire bay was filled with compost containing sludge. The two lines in each figure show measurements taken down the center of the bay at two depths; At both places temperature increased markedly over the first 90 feet down the bay.

within the top foot and three feet from the top.

Since the compost was moved ten feet each day, each ten foot distance is roughly equal to one day of retention. Thus the data also show an increase in temperature with the first 9 days of retention. all three days it is apparent that temperature at the three foot depth were held above 55 C for a distance of about more than 60 feet and thus a retention period of at least six days.

On

The differences between the two lines in each figure is indicative of the variation in temperature within the compost. Due to the movement of air up from the floor of the bay, generally higher temperatures were typically observed near the surface. Reversals in this pattern reflect short periods when the blowers supplying air to a portion of the bay were turned off. It should be noted that the compost was thoroughly mixed by the agitating machine and that temperatures immediately after the passage of the machine did not show the typical gradient, but were more nearly equal to the mean of the two positions.

Zimpro Sludge

Laboratory data collected in the second study with a Zimpro sludge are summarized in Table 8. The sludge (a mean of 24 % dry solids) was mixed with sawdust to yield an input mixture of 41 % dry solids. After about 20 days composting the dry solids content was increased to 56 % with the volatile solids reduced from 89 to 81 %. As was noted in the previous study, the pH increased (from 7.6 to 8 ) and the nitrogen decreased (2.5 to 2.2 %). Concentrations of metals (not shown) also increased during composting but were lower in the output than in the sludge.

A total of 16 wet tons of sludge (3 .8 dry tons) were delivered for this part of the study. As shown in the materials balance (Table 9) sawdust was mixed at a ratio of 1:0.6 (w:w) to produce an input mixture of 25 wet tons (10.3 dry tons). There was a 39 % reduction in wet weight, loss of volume after composting.

16 % loss of dry weight and 34 %

Measurements made during the first few days of the study indicated a rapid increase in temperature and temperatures in excess of 55 C within 72 hours after the bays were loaded. During the last five days temperatures were reduced and held near ambient by increasing aeration rates.

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DISCUSSION

Results of these studies document the performance of the composting system with a variety of municipal wastewater sludges. Sludge was mixed with sawdust at different ratios producing an input mix which ranged widely in % dry solids (Table 2 ) . Not surprisingly, the dryness of the output compost also varied. However, the dryness of the output was generally correlated with the quantity of bulking agent and the production of a dryer input mixture. For example, in the five town study, the driest output (58.9 % dry solids) was obtained with sludges from Killingly and Groton (Table 5) which were mixed with sawdust at a ratio of 1.1 ton of sawdust to each wet ton of sludge to produce an input mixture of almost 40 % dry solids.

Variations in the % dry solids of the output compost generated from the.different communities (Table 2 ) may also reflect changes in operation of the blowers and experience gained over the course of the demonstration. Thus it is nearly impossible to attribute variations in dryness of the output compost to differences among the sludges.

In general the results obtained with the Zimpro sludge were similar to those observed with the other sludges. For example, the percent losses in wet weight, dry solids and volume given in Table 4 and Table 9 were comparable despite the differences in sludge characteristics.

Weight losses observed during the composting process were a function of both moisture loss and destruction of volatile solids. The losses in moisture, reflected in the increased % dry solids, greatly exceed the losses of solids. The change in volume is likely due to shredding action associated with the daily agitation and the increasing production of smaller particles accompanying the destruction of solids.

When dry solids (and ideally at 40 %) dry output compost (60 % dry solids or days. At the onset of the demonstration the ratio of sludge and bulking agent was not adequate to produce an input mix that was consistently greater than 35 % dry solids. Failure to maintain adequate dry solids content in the input mix resulted in production of output compost at less than 50 % dry solids (Table 2 ) . Toward the end of the project (sludge from Killingly and Groton) a 1:l s1udge:bulking agent ratio was used and an output compost near 60 % dry solids generated (Table 5).

the dryness of the input mix was maintained above 36 %

greater can be expected with a retention time of 20-24

In addition to the sawdust, leaves and chips were found to be suitable bulking agents and thus could replace or supplement the use of sawdust (Table 7). Because of difficulty in handling, leaves were found to be problematic in mixing accurately with the sludge to produce a uniform input mixture. Thus it is recommended that they be shredded prior to use.

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The a unique feature of this system and appears to be an important feature facilitating the composting process. Bulking agent and sludge were mixed using a small front-end loader prior to loading the bays. Due to the daily agitation, balls of sludge and bulking agent were quickly broken up and compaction of the compost was minimal. The mixing also minimized the establishment of temperature and moisture gradients with the compost depth that result from the movement of air.

daily mixing of the compost by the agitation machinery is

Studies of other vessel composting systems without regular compost agitation have reported problems with poor air movement and compaction. In such systems, mechanical mixing of sludge and bulking agent are necessary to alleviate these problems ( 2 ).

Results of. the demonstration indicate that between 2.5 and 3.6 wet tons of sludge (0.6 dry tons) were processed on a daily basis in the single bay. These results were obtained with sludges at a mean of 17 W dry solids. Greater quantities of sludge may be handled if the W dry solids is increased or if a drier bulking agent is used. For example, during the study with the zimpro sludge (24 W dry solids) approximately 4 wet tons of sludge were loaded per bay per day.

Temperatures in excess of 55 C were maintained throughout a section least three consecutive days (Figs. 2, 3, and 4 ) . This data indicates that the compost would be subjected to temperatures adequate for reducing pathogens for at least six consecutive days and thus E.P.A. requirements for pathogen reduction can be readily met. Temperatures greatly in excess of 55 C have been found to reduce microbial populations and activity; thus holding compost at such temperatures for prolonged periods may inhibit drying and stabilization ( 2, 3, 4 ).

of the compost more than 60 feet in length for at

The system provides five separate aeration zones within each bay with independent control of each of the blowers. Because of this design airflow through the compost can be easily regulated both to meet demands for pathogen reduction and obtain high rates of drying at different stages during the composting. For example the system can be easily operated to maintain temperatures in excess of 55 C at either the beginning or the end of the composting period.

In addition, the system of multiple bays allows for operational flexibility. and the hydraulic retention time is easily controlled by the operation of the agitator. the agitator can be run through one or more bays twice during a day and other bays can be skipped. In this manner materials can be held within the bays for varying periods of time according to needs for increased drying, stabilization or even pathogen reduction.

The rate of flow of materials through the bays

For example,

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ACKNOWLEDGMENTS

We thank Randy May and Warren Herzig from the Connecticut Department of Environmental Protection for their encouragement and advice. This work would not have been possible without the assistance of Grant Weaver, Norwich; Chris Hoffman, Windham; Jim McDermott, New London; Paul Trahan, Killingly; and Carl Almquist, Groton, in supplying sludge and paying for laboratory costs. The contributions of Dr. Doug Bourgatti, City of Springfield, for supplying the Zimpro sludge are also appreciated. Lastly the contributions of the management and various personnel at Earthgro Inc. are greatfully acknowledged for allowing the use of their composting facilities.

LITERATURE CITED

1. Goldstein, N., 1987. Facilities composting municipal sludge in the U. S. BIOCYCLE, 28 (10): 24.

2 . Kuter, G. A., Hoitink, H.A. J., and L.A. Rossman, 1985. Effects of aeration and temperature on composting of municipal sludge in a full-scale vessel system. JWPCF 57: 309.

3. McKinley, V. L., and J. R. Vestal. 1984. Biokinetic analyses of adaptation and succession: Microbial activity in composting municipal sewage sludge. Appl. Environ. Microbiol. 47: 933.

4 . Finstein, M. S. et al. 1983. Composting ecosystem management f o r waste treatment. Biotechnol. 1: 347.

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TABLE 1. RESULTS OF LABORATORY ANALYSES OF SLUDGE SAMPLES

PPM (MG/KG)

SAMPLES %DS %VS pH %TKN %NH3-N P K CD CR CU PB HG NI ZN ~~

NORWICH 14.5 68.1 6.8 5.6 0.80 544 900 2.8 5 527 28 1.6 50 933

WINDHAM 14.7 83.2 5.6 8.1 1.10 805 2964 81 51 587 1421 ND 148 2671

NEW LON. 15.9 77.3 5.8 7.2 0.55 711 1168 7.9 32 891 160 1.9 66 1005

KILLING. 15.9 62.0 7.3 8.4 1.88 3488 2316 5.8 29 579 58 ND 29 284

GROTON 15.8 86.0 5.4 9.2 2.07 3223 915 ND ND 61 ND ND 31 61

MEAN 15.4 75.3 6.2 7.7 1.28 1754 1653 20 24 53 333 0.7 65 991

TABU 2. SUMMARY OF DATA OBTAINED DURING COMPOSTING OF MUNICIPAL SLUDGE

SLUDGE SAWDUST INPUT MIX OUTPUT COMPOST SOURCE TONS WDS CU.YRDS. TONS W DS WDS

NORWICH

WINDHAM

NEW LONDON

KILLINGLY

GROTON

45.02

28.00

12.70

18.61

13.91

TOTALS/ MEANS

118.24

15.5

19.0

15.0

18.5

17.0 -

17.0

69.75 27.9 33.3 43.6

41.00 16.4 38.7 45.8

25.50 10.2 31.3 45.0

43.00 17.2 34.2 51.8

46.75 18.7 38.8 66.0

226.0 90.4 35.3 50.4

TABLE 3. RESULTS OF LABORATORY ANALYSES: SAMPLES OF INPUT MIXTURE AND OUTPUT COMPOST

PPM (MG/KG)

SAMPLES %DS %VS pH %TKN %NH3-N P K CD CR CU PB HG NI ZN

INPUT MIXTURE:

NORWICH 34.6 71.6 6.8 2.0 0.16 208 2561 0.3 12 83 9 ND 9 196

WINDHAM 35.9 73.4 6.8 2.4 0.52 379 3165 21 19 182 512 ND 56 801

NEW LON. 34.7 84.1 6.7 2.3 0.47 801 1681 6.7 11 224 90 ND 2 105

KILLING. 35.8 86.0 7.2 1.7 0.68 1703 1250 ND ND 13 ND 0.11 ND 8

GROTON 34.6 86.9 7.1 1.7 0.04 168 1511 ND ND 9 ND ND 6 15 ~~

MEAN 35.1 80.4 6.9 2.0 0.37 610 2034 5.6 8 102 122 .02 15 225

OUTPUT COMPOST:

NORWICH 61.9 47.9 7.6 1.3 0.22 1520 2756 0.6 2.2 21 3.4 0.1 5.6 22

WINDHAM 45.2 76.4 8.0 1.5 0.04 581 1735 8.4 9.9 74 159 ND 20.0 313

NEW LON. 42.2 89.0 7.4 2.6 0.03 72 1984 9.2 31 244 122 ND 61.0 289

KILLING. 48.6 85.1 7.0 1.4 0.02 405 2452 6.0 9.0 233 90 ND 45.0 321

GROTON 66.9 80.5 7.6 2.4 0.03 2481 3810 3.3 12 129 35 0.4 12.0 361

MEAN 53.0 75.8 7.5 1.8 0.07 1150 2547 5.5 12.8 140 80 0.1 28.7 261

TABLE 4. MATERIALS BALANCE BASED ON TOTAL QUANTITIES OF SLUDGE AND COMPOST FROM FIVE MUNICIPALITIES

WET TONS % DRY SOLIDS DRY TONS CUBIC YARDS

INPUTS:

SLUDGE 118.2 17.0 20.1 150

SAWDUST 90.4 59.0 53.3 226

INPUT MIXTURE 208.6 35.0 73.4 376

OUTPUT COMPOST 135.3 50.4 68.2 271

LOSS 73.3

% OF INPUT 35.2

- - 5.2 105

7.1 28

TABLE 5. COMF'OSTING RESULTS WITH SLUDGE OBTAINED FROM THE TOWNS OF KILLINGLY AND GROTON

WET TONS % DRY SOLIDS DRY TONS CUBIC YARDS -~ ~

INPUT :

SLUDGE 32.5 17.8 5.8 42

SAWDUST 35.9 53.8 19.3 90

INPUT MIXTURE 68.4 36.5 25.1 132

OUTPUT COMPOST 40.2 58.9 23.7 83

TABLE 6. MEAN DAILY QUANTITIES OF MATERIALS HANDLED PER BAY

WET TONS DRY TONS CUBIC YARDS

SLUDGE 3.6 0.6 4.7

SAWDUST 2.7 1.6 6.8

INPUT MIX 6.3 2.2 11.5

OUTPUT COMPOST 4.7 2.1 8.2

TABLE 7. QUANTITIES OF SLUDGE, WOOD CHIPS AND LEAVES USED IN COMPOSTING DEMONSTRATION

WET TONS % DRY SOLIDS DRY TONS CUBIC YARDS

INPUTS :

SLUDGE 12.6 16.5 2.1 16

CHIPS 6.3 62.0 3.9 18

LEAVES 2.0 16.0 0.7 16

- - - - INPUT MIXTURE 20.9 32.1 6.7 38.5

OUTPUT COMPOST 11.8 53.5 6.3 27.3

TABLE 8. ANALYSIS OF ZIMPRO SLUDGE, INPUT MIXTURE AND OUTPUT COMPOST USED IN COMPOSTING DEMONSTRATION

% DRY SOLIDS W VOLATILE SOLIDS PH X TKN

SLUDGE 24 76 5.7 4.7

INPUT MIXTURE 41 89 7.6 2.5

OUTPUT COMPOST 56 81 8.0 2.2

TABLE 9. MATERIALS BALANCE OBTAINED WITH ZIMPRO SLUDGE

WET TONS % DRY SOLIDS DRY TONS CUBIC YARDS

INPUT:

SLUDGE

SAWDUST

INPUT MIXTURE ------------

OUTPUT COMPOST

LOSS -------------

% OF INPUT

16

9

25

15

lo --

40

24 3.8

56 8.3

1.7 ---

16

20

36

56 --

37

19 --

34

FIGURE 1. DAILY FLOW OF MATERIALS PER BAY

SLUDCE

1 .O WET TONS

L

\

4

OUTPUT COMPOST

1.3 WET TONS

2.3 CUBIC YARDS

SAWDUST

0.8 WET TONS

1.9 CUBIC YARDS

J -

INPUT MIXTURE

1.8 WET TONS

3.2 CUBIC YARDS

I ‘ V

TEMPERATURE N TOP in. TO 1 L t .

o--.I------o TEMPERATURE AT 3 ft. FROM TOP I I I I 1 I I I 1 I I I I 1 I I I I 10 20 30 4 0 50 60 70 80 90 180 110 120 13@ 140 150 160 170 180

DISTANCE (FEET)

FIG. 3

MUNICIPAL SEWAGE SLUDGE COMPOST TEMPERATURES

0- -- 0 TEMPERATURE IN TOP 6 in. TO 1 ft. 0-0 TEMPERATURE AT 3 ft. FROM TOP

0 10 20 30 4 0 50 60 70 80 90 100 110 120 130 140 150 160 170 180

(11 /12 / 8 6 )

,*-4

DISTANCE (FEET)

30-

FIG. 2 MUNICIPAL SEWAGE SLUDGE COMPOST TEMPERATURES (11/11/80)

O - - - O TEMPERATURE IN TOP 6 in. TO 1 ft.

0-0 TEMPERATURE AT 3 ft. FROM TOP 25 1 I I I 1 1 I I I 1 1 I I I 1 I 1 I

0 10 20 30 4 0 50 60 70 80 90 100 110 120 130 140 150 160 170 188 DISTANCE (FEET)