EFFECTS OF ADDITIVES ON SOLIDIFICATION OF API SEPARATOR SLUDGE ADAM FASCHAN, MARTY TITTLEBAUM, FRANK CARTLEDGE, and HARVILL EATON Louisiana State University, Hazardous Waste Research Center, Baton Roudge, LA 70803, U.S.A.

(Received February 1990) Abstract. API separator sludge was solidified with various combinations of binders and absorbent soil

additives. The binders utilized were Type I Portland Cement, Type C Flyash, and a 1:1 combination of the two. The soil additives used were bentonite, diatomite, Fuller's earth, and two brands of chemically altered bentonites, or organoclays. The effectiveness of the solidification materials was based on their effect on the physical and leaching characteristics of the sludge. It was determined the Portland cement and combination binders provided the sludge with adequate physical and strength characteristics. It was also determined the affinity of each additive for water had an important influence on the physical characteristics of the solidified sludge. The results of the leaching procedure indicated the binders alone reduced the leachability of organic constituents from the sludge by 1/5 to 1/10. It appeared the use of the additives with the binders may have further reduced the leachability of constituents from sludge, with the incorporation of the organoclay additives further reducing leachability by up to 1/2. Also, it appeared the absorbing capacity of the additives was directly related to their ability to reduce the leachability of organic constituents from the sludge.

1. Introduction

Approximately 300 million tons of hazardous wastes are produced annually in the United States (Sommerville, 1986). In 1984 several amendments were added to the existing Resource Conservation and Recovery Act (RCRA) which implemented new provisions governing the disposal of these wastes. These provisions called for the ban of all liquid hazardous wastes from land disposal. Also, the amendments required the Environmental Protection Agency (EPA) to reach decisions on banning the land disposal of all listed hazardous wastes. This has resulted in a search for alternate treatment technologies to dispose of these wastes. From this ongoing search, the effective solidification of certain wastes prior to land disposal has become a possible economical solution. Solidification has been shown to be effective in treating wastes containing certain heavy metals. However, solidification technology has run into difficulties when trying to solidify organic wastes. The solidification of organic wastes often produces materials with poor strength characteristics. The solidified organic wastes which exhibit good strength characteristics often leach high concentrations of organics into the surrounding environment. Although some commercial processes claim successful solidification of organic wastes, it appears little data is available on the performance of materials used to solidify them. The information that is available must often be judged on the basis of the manufacturer's claims rather than the evaluation of an impartial referee (Tittlebaum et al., 1985). Since many of the hazardous wastes presently produced contain organic compounds, Environmental Monitoring and Assessment 18: 145-161,1991.

146

ADAM FASCHAN

E T AL.

research is needed to determine if these materials can be effectivelysolidified. The research that has been performed has concentrated on solidifying pure organic compounds or synthetic wastes. This is because the complex composition of most real waste streams produces leachates which are difficult and time consuming to analyze for the wide range of organic compounds they contain. A solution is the use of analytical methods such as the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) analyses to assess the relative magnitude of organic compounds in the leachates of the wastes. The applicability of using these tests to evaluate the leachability of solidified organic wastes is discussed by Faschan et al., (1990). The solidification of organic wastes often utilize binder materials such as Portland cement or flyash. However, absorbent soil materials are commonly used as additives in solidification processes. These materials can absorb wastes and can be successfully incorporated in the structure of binders like cement (Wiles, 1987). The possible result of this phenomenon is the organics absorbed onto these compounds may be microencapsulated by the binder which may reduce their leachability. The purpose of this research was to determine if a complex organic waste, API separator sludge, could be effectively solidified and if the use of various absorbent soil additives could increase the effectiveness of its solidification. The binders used in this research were Type I Portland Cement, and Type C Flyash. The absorbent soil additives used were bentonite, diatomite and Fuller's earth. Also, two types of specially treated bentonite or organoclays were utilized as absorbent soil additives. The criteria for evaluating the performance of the solidified sludge samples were unconfined compressive strength as estimated by a pocket penetrometer and leachability testing. The leachates of the samples were analyzed for COD and TOC content. 2. Methods

The waste solidified in this research was an API separator sludge. The phase characteristics of the sludge were approximately 7% light oil, 83% water and soluble organics, and 10% solids and heavy oils. Before centrifugation most of the light oil in the sludge was in a emulsified state. The waste was solidified by different combinations of binders and additives. The binders used were Type I Ordinary Portland Cement, Type C Flyash, and a 1:1 combination of these two materials. The additives utilized included bentonite, diatomite, Fuller's earth (FE), and two brands of organoclays, Organo-B, and Organo-S. The organoclays consisted of bentonite treated with various organic alkylammonium compounds to increase their capacity to absorb organics (Sheriff et al., 1987). All the materials were obtained from commercial sources. The combinations of the binders and additives used to solidify the API separator sludge are shown in Table I. Each combination in this table consisted of a 1:1 ratio of waste to binder by weight. 50 g of binder and 50 g of sludge were used in each sample. The combination binder consisted of a mixture of 25 g of cement and 25 g of flyash. The water content for each binder was a ratio of 0.5 water to binder by weight in addition to the water

EFFECTS

OF

ADDITIVES

ON

SOLIDIFICATION

OF

API

SEPARATOR

147

SLUDGE

contained in the sludge. The additives used in the table are expressed as a weight percent o f the waste in each sample. F o r example, ratio 1 for bentonite under the T y p e I Cement column, represents a sample consisting o f 50 g o f cement, 25 m L o f water, 50 g o f sludge, and 10 g o f bentonite. The additive ratios shown in the table were based on the results o f preliminary mixes. SAMPLE PREPARATION A representative sample o f the sludge was obtained a n d mixed with each additive by h a n d for 2 min in a specimen cup. The binder was then c o m b i n e d with 25 m L o f deionized water and was mixed for 2 min by h a n d in a specimen cup. The two mixes were c o m b i n e d and mixed for three minutes by hand. The final mixture was placed in a specimen cup, capped, sealed with parafilm, and allowed to set for 7 days + 1 hour. Once the material reached its seven d a y strength it was strength tested with a pocket penetrometer, crushed, leached, and filtered. PENETROMETER TEST After each sample was allowed to set for 7 days, it was tested with a pocket penetrometer. The p e n e t r o m e t e r used was a H u m b o l t Pocket Penetrometer with readings in the range o f 0-4.5 tsf, or 0-62.5 psi. After the penetrometer test, each solidified block was crushed with a ceramic m o r t a r a n d pedestal and passed through a 9.5 m m sieve onto a l u m i n u m foil. The material was then placed into a one gallon high density polyethylene ( H D P E ) container with four times its weight of distilled-deionized water for the leaching procedure. LEACHING PROCEDURE The leaching procedure utilized was a modified version o f the Toxicity Characteristic Leaching Procedure ( T C L P ) ( F e d e r a l Register, 1986). The modifications included using TABLE I Combinations of binders and additives used to solidify the API separator sludge Bindersa Type I cement

Type C f l y a s h

Combinationb

Additive ratiosc Additives

1

2

3

1

2

3

Bentonite Diatomite FE Organo-B Organo-S

20% 20% 20% 20% 20%

30% 30% 30% 30% 30%

40% 40% 40% 40% 40%

20% 20% 20% 20% 20%

30% 40% 30% 40% 30% 40% 30% 40% 30% 40%

1

2

20% 20% 20% 20% 20%

30% 40% 30% 40% 30% 40% 30% 40% 30% 40%

Water was added to each binder at a ratio of 0.5 water to binder. bThis binder consists of a 1:1 mixture of Type C Flyash and Type I Cement. cThe additive ratios are reported as weight percentages of the sludge in each sample.

3

148

ADAM

FASCHAN

ET AL.

distilled-deionized water as the leaching fluid and using a leaching period of 2 hr___5 min. Also, 1-gallon HDPE containers were used as the leaching containers instead of glass containers. The leachate of the samples were filtered through 0.7 ~m glass fiber filters utilizing maximum pressures of 50 psi in a zero headspace apparatus as designated by the TCLP procedure. In addition to the solidified sludge samples prepared in Table I, several control samples were tested with the leaching procedure to determine whether the various additives and binders used would have an effect on the results. A sludge control sample was utilized which consisting of 50 g of the raw sludge leached in four times its weight of distilleddeionized water. Also, samples containing the binders without the sludge or additives were prepared by mixing 50 g of each binder with 25 ml of deionized water. Samples containing the sludge and binders without additives (sludge-binder samples) were prepared by mixing 50 g of each binder with 25 ml of deionized water, and then 50 g of sludge. These samples were allowed to set for 7 days and then were ground, leached, and filtered. Finally, 20 g samples of the additives were leached in four times their weight of distilled-deionized water. However, it was impossible to obtain leachate from the bentonite additive using this procedure, so the control for this sample consisted of 5 g of additive in 80 times its weight of water. The leachates of all the samples were tested for their relative concentrations of organic compounds by Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) analyses. COD ANALYSIS The COD method used in this research was Procedure 508 B in Standard Methods: For the Examination of Water and Wastewater (1985). The procedure is a closed reflux method utilizing potassium dichromate (K2Cr207) as the chemical oxidant. However, a few changes were made to the procedure. Instead of preparing the digestion solution according to the procedure, premade vials of the solution were obtained from Hach Corporation. These vials contained digestion solutions for samples with CODs in the range of 0-150 mg 02 1-t or 0-1500 mg 02 1-t. Two milliliter portions of each leachate sample were placed into the vials. The vials used depended on the suspected organic concentration in each leachate. Due to the premade digestion solutions, the concentration of the solutions used for the titration and standardization procedures were also altered. The standardization and titration solutions were 0.25 N potassium dichromate and 0.125 N ferrous ammonium sulfate (Fe(NH4)2(SO4)2), respectively for the high range vials and 0.025 N potassium dichromate and 0.0125 N ferrous ammonium sulfate, respectively, for the low range vials. The solutions were made according to Standard Methods (1980) Procedure 508 A. Duplicate analyses were performed on each leachate sample to obtain a average COD value. TOC ANALYSIS The method used in this research was the Combustion-Infrared Method, Standard Methods (1985) Procedure 505 A. An Oceanographic International Model 524B total

EFFECTS

OF ADDITIVES

ON SOLIDIFICATION

OF API SEPARATOR

SLUDGE

149

carbon analyzer was used to analyze the samples. The carrier gas for the total (TC) and inorganic (IC) carbon determinations were oxygen and nitrogen, respectively. Standardization curves for the IC and TC determinations were prepared according to the manufacturer's instructions. Daily performance of the machine was checked by analyzing a 100 mg C 1-J standard for its total carbon and inorganic carbon cotent. If the value of the standard varied by more than 10% from the standardization curves, the packing in the filament of the machine was changed and any residues in the combustion chamber were eliminated. 30 microliter samples were used to determine the total carbon content and 60 #1 samples to determine the inorganic carbon content for each of the leachate samples. Samples of each leachate were injected until the integrated area for three consecutive analyses were within approximately 10% of each other. 3. Results

The results from this research consisted of three types of observations. These observations were physical observations made during the preparation and testing of the samples, results of the penetrometer tests on the samples, and the COD and TOC results of the leachates from the samples. PHYSICALCHARACTERISTICS Physical observations yielded information on differences in the characteristics of samples solidified with different binders. Such observations included determining the presence of watery or muddy layers in the solidified sludge samples and estimating the strength development and volume increase of the waste due to solidification. Differences were observed between the samples incorporating different binders. As expected, all the samples containing solely binders formed monolithic solidified blocks. However, when crushed, the sample containing flyash seemed somewhat wet and unhydrated. Also, the sludge binder sample or the samples containing the binders and sludge without additives formed monolithic solidified blocks, but again the sludge-flyash sample had a lesser strength than the other samples (Table II). In addition, as a general rule the solidified samples using the cement and combination binders with additives formed strong monolithic endproducts, while most of the samples made using the flyash binder formed wet muddy unhardened endproducts. Differences in physical properties were also exhibited by samples using different additives to solidify the waste. The samples incorporating the bentonite, diatomite, and FE additives and the cement and combination binders formed strong monolithic endproducts. The samples incorporating the Organo-B and Organo-S additives exhibited slightly different qualities. The organ0clay substances seemed to cause the largest volume increases of all the samples, approximately double the original sludge volume. In addition, the samples using additions of 20% Organo-B, 20% Organo-S, and 30% Organo-S had porous wet muddy layers on their surfaces after seven days. The layers appeared to be made mostly of the organoclay additives. Meanwhile, the samples using higher additive

150

ADAM

FASCHAN

ET AL.

ratios o f organoclay additives formed very strong endproducts when mixed with the sludge and the cement and combination binders. It should also be noted that the bentonite, diatomite, and FE additives appeared to absorb most of the liquid from the sludge by forming cohesive muds when mixed with it. Meanwhile, the organoclay additives formed a material with a foamy consistency when mixed with the sludge leaving clear water at the bottom of the mixing container. The penetrometer results listed in Table II reinforced the physical differences observed between samples utilizing different binders. Table II illustrates that all the samples incorporating the cement and combination binders had strengths in excess of 62.5 psi, while none of the flyash samples had strengths greater than 50 psi. It should also be noted that the strengths o f the cement and combination binders appeared much higher than 62.5 psi when they were crushed. 9LEACHABILITY RESULTS The results of leaching procedure essentially consisted of the results of solidified samples consisting of additives, binders, and sludge and five types of control samples. The previously described control samples consisted of the raw sludge and sludge control samples, the sludge-binder samples, samples containing only the binders, and samples containing only the additives. The different controls were performed for different reasons. The raw sludge (not exposed to the leaching procedure) and sludge control sample were utilized to determine how the leaching procedure affected the leachability of the sludge. The sludge-binder samples were used to determine the ability of the binders alone to reduce the leachability of the sludge. The binder and additive samples were used to determine if organic compounds from these materials were contributing to the C O D TABLE II Sample penetrometer values (all values in psi) Binders

ControP

Type C f l y a s h

Combination

samples Type I OPC

Additive ratiosb Additives Cement Flyash Combination Sludge Bentonite Diatomite FE Organo-B Organo-S

1

>62.5 >62.5 >62.5 2>62.5 3>62.5

2

>62.5r >62.5 >62.5 >62.5 >62.5 >62.5

3

>62.5 >62.5 >62.5 >62.5 >62.5

1

0.0 17.4 20.8 41.7 48.6

2

41.7r 6.9 0.0 24.3 34.7 41.7

aSamples consist of 25 ml of water and 50 g binder. bAdditive ratios as displayed in Table I. cSamples consist of 25 ml water, 50 g binder, and 50 g sludge.

3

13.9 27.8 6.9 38.2 41.7

1

2

>62.5c >62.5 >62.5 >62.5 2>62.5 >62.5 >62.5 >62.5 >62.5 3>62.5 >62.5

3

>62.5 >62.5 >62.5 >62.5 3>62.5

>62.5 >62.5 >62.5 -

EFFECTS OF ADDITIVES ON SOLIDIFICATION OF API SEPARATOR SLUDGE

151

and TOC results of the solidified sludge samples or the samples containing binders, additives and sludge. The solidified sludge samples could then be compared to the binder values, additive values, sludge-binder, and sludge control values to determine if a particular binder-additive combination affected the leachability of the sludge. Table III displays the COD and TOC values of the leachates from the control samples. As can be seen in Table III the sludge control sample yielded a COD of 914 mg 021 -~, and a TOC of 128 mg C 1-I. These values are an order of magnitude lower than the COD and TOC values of the raw sludge, which were > 30000 mg 02 1-1 and 3, 395 mg C 1-~, respectively. Many of the other control samples were expected to exhibit very low COD and TOC values. However, only the cement binder was as low as expected with a COD of 8.2 mg 021 -l, and a TOC of 10.6 mg C I-L The COD and TOC values of the combination binder, and the bentonite, FE, and Organo-S additive samples all had slightly higher COD and TOC values in the range of 50 mg 1-t. Meanwhile, the flyash sample had even higher COD and TOC values of 363 mg 021-~ and 113 mg C 1-~, respectively. The COD and TOC values for the Diatomite and Organo-B additives were much larger than expected, and significantly larger than the values for the sludge control sample. The COD and TOC results for the leachates from the solidified sludge samples and the sludge-binder samples are displayed in Figures 4 and 5, respectively. The values of the sludge-binder samples and the sludge control samples are compared in Figure 1. The COD value for the sludge control sample was 914 mg 02 1-1, while the values for the sludge-cement, sludge-flyash, and sludge-combination samples were 60.0, 198.5, and 72.5 mg 021 -l, respectively. Likewise the TOC value for the sludge control sample was 128 mg C 1-~, while the values for the sludge-cement, sludge-flyash, and sludge-combination samples were 24.0, 28.8, and 27.5 mg C l-l, respectively. The comparison of these values in Figure 1 indicate that the sludge-binder values are about 1/5 to 1/10 of the sludge control sample values.

TABLE III COD and TOC values for control samples (COD values in mg O z 1-1,TOC values in mg C l-t) Control samples~'

TOC values

COD values

Raw sludgeb Sludge Cement Flyash Combination Bentonite Diatomite FE Organo-B Organo-S

3395.4 128. I 10.6 112.8 44.8 50.5 472.5 48.8 393.5 50.7

>30000.0 914.0 8.2 363.0 48.0 67.5 1673.5 94.5 1388.0 48.5

Samples passed through the leaching procedure containing only the materials mentioned. b Not passed through the leaching procedure.

152

A D A M FASCHAN ET AL.

Comparison of Sludge Control and Sludge-Binder Sample COD Values 1000 900 800

Valueof Sludge /

70O

i

600 500 400 300 200 IO0 0

Control Sample = 914.0

Cement

Flyash

Combination

Sludge-Binder Samples Comparison of Sludge and Sludge-Binder Sample TOC Values

J

130 120 110 100 90 80 70 60 50 40 30 20 10 0

Valueof Sludge / Control Sample = 128.0

Cement

Flyash

ComblnaLion

Sludge-Binder Samples Fig. 1. Comparison of sludge control and sludge-binder samples.

The differences between the COD and TOC values for the solidified sludge samples containing various additives, and the values of the samples containing just the additives are illustrated in Figures 2 and 3. It is obvious in these figures that the COD and TOC values for the bentonite, FE, and Organo-S additives are of the same magnitude as the values for the solidified sludge samples that use these additives. However, the COD and TOC values for the Organo-B and diatomite additives are an order of magnitude larger

EFFECTS OF ADDITIVES ON SOLIDIFICATION OF API SEPARATOR SLUDGE

153

(a) Comparison of Bentonite COD Results (13) Comparison of"DiatsmlLe COO Results 150 Valueof Bentonite 1600 Ylf

i O0

~

~50 "I ~ ] ~

- 67.5

1400 1200 Valueof Diatomi 1000 Sample-167:5.5

800

~

lll

l _ [] Cement Jl 9 Flyash

g 600

o 20%Bent30XBent40%Bent

o ~ ~lB. 20~gDlat50~Dlat40%Dial

Samples (C)

Samples

Comparisonof FE COD Results

(d) Comparison or Orgamo-8 COD ResulLs

14001

200 /

I Jl ~9I t~ ~ I~

o~

9

I

J [/1 ~

/

1200 1000 Valueof ~gano~

I

' ~ 100~

l

~ Cement

.... Flyash oo,o.,,on

oo,n.,,oo e,:Oo

Value ofFuller's EarthIu800 i]Sample-1588.0 i Samplr :~600 Cement ~ [] Cement ~ 400 Flya~

~ ~

9 Flyash 200 9 Combination | ~

2oR FE 30% FE 40~r FIE Samples

(e)

Combination

. ~

-- . r , -

o 2o~o~-B3o~o~o-e4o%o~g-B Samples

Comparison of Orgonu-S Results

200

i

I00

[] Cement 9 Flyash 9 Combination

i

20% 0rg-S 50% 0rg-S 40% 0ro-S Samples Fig. 2. Comparison of additive COD values with COD values of solidified sludge samples utilizing the additives. than the values of the solidified sludge samples that use these additives. The relationship between the sludge control sample, sludge-binder samples and the rest of the solidified sludge samples are illustrated in Figures 4 and 5. As a general rule almost all the COD and TOC values for the samples containing the bentonite, diatomite, FE, and organoclay additives were in the same range as their corresponding sludge-binder samples with most having slightly lower values. The figures also indicated

154

ADAM

FASCHAN

ET AL.

(a) Cemparlson of Bentonite TO(; Results (b) Comparison of Olatsmite TO(: Results

]/11 ~ ~L Sample- 50.5

j 3o1 #,

20 I0 O

[]

~

400 -]

t v'~176176 ~,~,e-,~ I 300 ~~ 250 ~ 1

200 ~[ Cement 150 -J Flyash 100 ~ Combination 5 0 0 t ~

20~Bea;~l~t 4~Oea

2r

Samples (c)

/

[] Cement 9 Flyash 9 Combination ~ ~OXDiat 4~Oiat Samples

Comparisonof FE TO(: Results

50 n

((1) Comparison of 9rgino-6 TOC Results

400

40

j 3o

,ller's Earth

350 1

~.8

30O 1

/ f

-

= 2501 ~::;'; ~'3~ B

=~

~ 2001

,o

|

9 Flyash 9

Lion

,~~,, "~~ 0

20~ FE 30~ FE 40~ FE Samples

(e) 60

50 40

20~ O'g-B 30~ 0/r

40~ Org-B

Samples Comparisonor Orgeno-S TOC Results Valueof Organo-S

Sample- 50.7

H fJ fJ

20 l0

Z

I'1

Cement

~'/ ,r

[Z~

~'~

9 Flyash

9 Combination

20~ Organo-S30X Organo-S40X Organo-$ Samples

Fig. 3. Comparison of additive TOC values with TOC values of solidified sludge samples utilizing the additives.

that most of these samples had values less than 1/5 to 1/10 of the sludge control samples. The solidified sludge samples using flyash as the binder showed some substantially lower values with the samples incorporating 20% and 40% Organo-B, and 20%, 30% and 40% Organo-S having COD values of 93.0, 124.5, 96.0, 87.5, and 126.5 mg 021-1, respectively, and TOC values of 12.6, 16.8, 17.2, 15.0, and 25.0 mg C l-l, respectively (Figures 4 and 5).

EFFECTS OF ADDITIVES ON SOLIDIFICATION OF API SEPARATOR SLUDGE

(a)

Coment Samples

9oo 8oo 700 600 ~, SO0 a

155

Valueof Sludge Control Sample= 914.0

400

Valueof Sludge-Cement 300 Sample= 60.0 200 100 0 ~7--- v = - - ,~"

I l.;,.i

(b) 900

l

800 9 700 9 600 1 SO0 1 400

a

rz--

Y,

I

[ ] Patio 1 9 Patio 2

9 Ratio3

Flyemh Samples Valueof Sludge Control Sample- g 14,0

Valueof Sludge-Flyash Sample 198.5

200

o 300 I00 " ~ L ~ i ~ i i ~ i ~ i ~ 0.

(c)

[] Ratio 1 m Patio 2 9 Patio 3

Combination Samples 900 800

Value0f Sludge Control Sample- 914.0

700 600 500

a 8 400 300 200 !00

Value of Sludge~ombinatlon

Sample= 72.5

17",1~Lio 1 Ratio2

0

PaUo3 Bentonite Diatomite

FE

~ g a n o - B ~gano-S

Samples

Fig. 4. Comparison of the bentonite, diatomite, FE, and organoclay solidifiedsludge sample COD values with the sludge control and sludge-binder sample COD values. 4. Discussion

The results indicate several aspects concerning the effectiveness o f the various binders a n d additives used to solidify the waste. These aspects deal with the physical a n d leaching characteristics o f the samples. PHYSICAL CHARACTERISTICS T h e p e n e t r o m e t e r results in T a b l e II i n d i c a t e d t h a t the solidified s a m p l e s t h a t

156

ADAM

ET AL.

CementSam~es

(a)130 12o 11o ioo 90

i 80

FASCHAN

Valueof Sludge Control Sample= 126.0 Valueof Sludge-Cement

5O r-A Ratio 1 9 Ratio2 9 Ratio3

3O 20 10 0

F iy~,h 5omplas

(b)13 o .

120' II0"

Valueof Sludge Control Sample- 128.0

100"

~

90" 80. 70 60" 50"

~ 30

l

Valueof Sludge-Flyash Sample - 28,8

40 9 171 Ratio I 9 Ratio 2 9 Ratio 3

20' 10"

(C) ,~^

i

I :.,,=l

Comblnotion $oinolos

! I~ Ratio t 9 Ratio2 9 Ratio3

l

I

Fig. 5. Comparison of the bentonite, diatomite, FE, and organoclay solidified sludge sample TOC values with the sludge control and sludge-binder sample TOC values.

incorporated the cement and combination binders with the separator sludge all had seven day unconfined compressive strengths greater than 62.5 psi. Also, it appeared when grinding these samples that their strength may have been much higher. Since 50 psi is the maximum stress solidified materials may be expected to experience in the landfill environment (Stegemann, 1987), these samples had more than adequate strengths to maintain their structural integrity when landfilled. Also, this indicated that even smaller amounts of these materials could have been used to solidify the sludge and provide strengths in excess of 50 psi. Meanwhile, Table II showed the samples using the flyash did

EFFECTS

OF ADDITIVES

ON SOLIDIFICATION

OF API SEPARATOR

SLUDGE

157

not develop strengths greater than 50 psi. This may have been due to the tendency of flyash hydration to proceed slower than cement hydration since the samples using the flyash binder seemed wet and unhydrated. From physical observation of the solidified sludge samples it was apparent that the amount of water absorbed by some of the additives affected the performance of the samples that contained them. It was obvious in the sludge-binder samples that the water added to the samples, in addition to the water available in the sludge, was much more than that needed for binder hydration. This was evidenced by the presence of a water layer on the surface of these samples seven days after their preparation. However, most of the solidified sludge samples incorporating the different additives did not have a water layer on their surfaces. This indicated that a certain degree of water in each sample may have been absorbed by the different additives. Also, as already stated the bentonite, diatomite, and FE additives when added to the API separator sludge, appeared to absorb the majority of the liquid in the sludge by forming cohesive mud-like materials, while the organoclay additives left water at the bottom of the mixing containers. This seems likely due to the organophilic and hydrophobic nature of the organoclays (Sheriffet al., 1987). It was also noted that the samples using the bentonite, diatomite, and FE additives formed strong monolithic solidified blocks, while samples containing the lower additive ratios of the organoclays, 20% Organo-B and 20% and 30% Organo-S, developed a muddy porous layer on their surface after seven days. It appeared in these samples that the volume of water unabsorbed from the sludge was large, which when combined with the 25 ml of water to each sample was in excess of that needed for binder hydration. This could have caused water to bleed to the surface of these samples carrying the organoclay additives with it. However, the samples containing higher additive ratios of the organoclay materials absorbed more water from the sludge and did not develop muddy surface layers. Thus, it appeared the relative affinity of additives for water had a definite effect on the physical characteristics of the samples and should be an important consideration when solidifying such wastes. LEACHABILITYCHARACTERISTICS Before the leachability of the various solidified sludge samples could be assessed it appeared the influences of the testing procedures on their leaching results had to be evaluated. It appeared the results were affected by the influence of the leaching procedure on sludge leachability and the inability of the COD and TOC analyses to differentiate between different organic compounds. The comparison between the raw sludge and sludge control sample values was used to determine how the leaching procedure affected the release and passage of organic material from the sludge into the filtered leachate samples. The differences between the COD and TOC values for the raw sludge and the sludge control sample were high. The raw sludge had COD and TOC values o f > 30 000 mg 021-~and 3395 mg C 1-~, respectively, compared to COD and TOC values of 914 mg 021 -~ and 128 mg C 1-~, respectively, for the sludge control sample. The large reduction in COD and TOC values between these samples could have been due to several factors. However, it appeared the major influence may have been

158

ADAM

FASCHAN

ET AL.

the absorption of the oils in the sludge by the filters used in the leaching procedure. Attempts to filter the raw sludge were abandoned and the COD and TOC results for the raw sludge are from an unfiltered sample. Meanwhile, the sludge control sample or the sludge sample passed through the leaching procedure was filtered despite some difficulty caused by filter clogging. The rest of the samples were filtered with little difficulty. It became apparent that the high COD and TOC values for the additives and binders would make the results of the solidified sludge samples difficult to interpret. Most of the binders and additives utilized were inorganic in nature and were expected to exhibit low COD and TOC values. However, the flyash binder, and the diatomite, and Organo-B additives exhibited very high values, and the other additives and binders except cement exhibited values high enough to suggest significant effects on the results of the solidified sludge samples. This is best illustrated by Figures 2 and 3 where many of the additive samples exhibit COD and TOC values larger than the solidified sludge samples that utilize them. Also, the COD values reported in Table III for the flyash and combination binders of 363 mg 021-1 and 48.0 mg 021-1, respectively, and TOC values of 112.8 mg C 1-~and 44.8 mg C l-l, respectively, were equal to or larger than the values for many of the solidified sludge samples. It was suspected that the organoclay additives might have high values, since the surface of these materials contained organic alkylammonium compounds that may be susceptible to desorption (Sheriff et al., 1987). However, there was no other explanation for the values for the rest of the compounds except that since they were commercial earthen compounds they might contain a certain degree of organic contamination. The significant COD and TOC values of the additives and binders made it difficult to determine what portion of the COD and TOC values of each solidified sludge sample was due to organic materials from the sludge and what portion was due to the organics from the additives and the binders. For example, the sample incorporating the sludge, the flyash binder, and 20% bentonite had a COD value of 104 mg O21-1(Figure 4). The COD values for the flyash, sludge control, and bentonite samples were 363, 914, and 67.5 mg 021 -l, respectively (Table III). The total COD value of the leachate from the sample might be expected to be over 1300 mg 021-1. The value of 104 mg 021-1 represented a reduction in the leachability of these materials, but it is difficult to determine what proportion of this reduction was due to the containment of the sludge by solidification. Despite the probable contribution of organic materials to the solidified sludge sample leachates by the additive and binder materials, it appeared that some degree of waste containment could be estimated for the solidified sludge samples. This was done by comparing the COD and TOC values of their leachates with those of the sludge control and sludge-binder samples. For instance, due to the organics contributed to sludge-binder sample by the binder the COD of this sample before leaching would be expected to be larger than the COD of sludge control sample before leaching. Thus, sludge-binder samples with values lower than the sludge control sample should indicate a decrease in the leachability of organic constituents from the sludge. Likewise a favorable comparison between the sludge-binder and solidified sludge samples may indicate that use of the additives in the solidified sludge samples may have further reduced sludge leachability.

EFFECTS

OF ADDITIVES

ON SOLIDIFICATION

OF API SEPARATOR

SLUDGE

159

It was shown in Figure 1 that COD and TOC values for the sludge-binder samples were an order of magnitude lower than for the sludge control values. These results indicated that the binders by themselves provided a solidification matrix that may have reduced the leachability of organic constituents from the API separator sludge by 1/5 to 1/10. The solidified sludge samples incorporating the additives could be compared favorably to sludge-binder samples. As can be seen in Figures 4 and 5 the COD and TOC values of these samples were either slightly higher or slightly lower than their corresponding sludge-binder values and 1/5 to 1/10 that of the sludge control values. Since part of the COD and TOC values from each sample was probably due to organic material from the additives, this indicated that these samples had an equal or lesser leachability of organics from the sludge than their corresponding sludge-binder samples and a leachability 1/5 to 1/10 that of the sludge control sample. Of particular note were the COD and TOC values of several of the samples using the organoclay additives and the flyash binder which were almost half that of the sludge-flyash sample (Figures 4 and 5). This indicated that these samples may have reduced the leachability of constitutents from the sludge by more than half of the value of the sludge-flyash sample. Another difference was exhibited between the COD and TOC values for Organo-B and the diatomite additives and the values of the solidified sludge samples incorporating these materials. There was an order of magnitude difference between the values for these additives, and the corresponding solidified sludge samples that incorporated them (Figures 2 and 3). It was suspected that the high COD and TOC values for the diatomite and Organo-B additives were a result of the desorption of organic materials already present on the surface of these materials. As already stated, for the Organo-B additive, the materials desorbed from its surface were most likely the alkylammonium compounds. If this were true, then the COD and TOC results for the solidified sludge samples incorporating these additives indicated that these additives may have been encapsulated by the binders in the samples greatly reducing the desorption of the organic materials from their surface. The importance of this observation is that it may indicate that organic materials from the sludge that absorbed onto the surface of these additives may have also been encapsulated by the binders and thus were prevented from releasing into the leachates from these solidified sludge samples. This would support the premise that certain additives could promote the adsorption of contaminants to a selected solid phase in the solidified samples (Wiles, 1987). It would also indicate that the containment of the sludge in the sample using these additives might be directly related to the ability of each additive to absorb the materials in the sludge. In addition, since the chemical composition of the bentonite, FE, and Organo-S additives were quite similar to the compositions of the Organo-B, and diatomite additives, it is suspected that these additives might have similar abilities. However, this was not indicated in the test results due to the low COD and TOC values for these additives.

160

ADAM FASCHAN ET AL.

5. Conclusions

This research indicated that API separator sludge could be solidified into a material with good physical characteristics without utilizing excessive amounts of binder materials. The use of Type I Portland Cement and a 1:1 combination of Portland cement and Type C Flyash when used with various additives and mixed with the sludge in a 1:1 ratio provided samples with strengths greater than 62.5 psi. Also, it appeared that smaller amounts of these binders could have been used to provide samples with strengths in excess of 50 psi. The research also showed that Type C Flyash by itself could not provide samples with adequate physical properties, probably due to slower hydration reactions occurring in the flyash. Another important observation was that the incorporation of absorbent additives with the binders affected the water available for hydration. It appeared the relative affinity of additives for water should be addressed when determining the overall water contents to be utilized for solidified samples in order to obtain the desired physical and strength characteristics. The ability of the various materials to contain the separator sludge was difficult to determine due to the liminations of the COD and TOC analyses (Faschan et al., 1990). However, it appeared that the use of the binder materials alone reduced the leachability of organic constituents from the separator sludge to 1/5 to 1/10 of its original value. It also appeared that the incorporation of the bentonite, diatomite, FE, and organoclay additives provided equal or greater containment of the sludge than the binders alone. The organoclay additives when used with the flyash binder appeared to reduce the leachability of constituents from the sludge by as much as 1/2 of the samples using the binder alone. Finally, it did appear from the low leachability of organics already absorbed on the surfaces of the diatomite and Organo-B additives that the absorbing capacity of the soil additives may be directly related to their ability to reduce the leachability of solidified organic wastes. Several recommendations for further research have come from this work. The first would be to perform absorption studies on various additives prior to solidification to determine the relationship between their absorption of organic compounds and the leachability of these compounds from the solidified sample. Also, other methods of determining the leachability of organic wastes from solidified samples should be investigated. A possible method may be to test the leachates for specific organic compounds suspected to readily leach from the solidified waste. References Alther, G. R., Evans, J. C., and Pancoski, S. E.: 1989, 'Organically Modified Clays for Stabilization of Organic Hazardous Wastes', Superfund "88 Proceedings of the 9th National Conference, 440-445, Faschan, A., Tittlebaum, M., Cartledge, F., and Eaton, H.: 1990, 'Use of the COD and TOC Analyses for Determining the Leachability of a Solidified Organic Waste', to be submitted for publishing. Federal Register: 1986, 'Toxicity Characteristic Leaching Procedure (TCLP)', Vol. 51, No. 216: 40643-40652. Sheriff, T.S., Sollars, C.J., Montgomery, D., and Perry, R.: 1987, 'Modified Clays for Organic Waste Disposal', Environ Technol Lett, $, 501-514. Somerville, R.B.: 1986, 'Encapsulation Solidification of Hazardous Wastes', "1986 AIChE Symposium"

EFFECTS OF ADDITIVES ON SOLIDIFICATION OF API SEPARATOR SLUDGE

161

Hazardous Waste Management', 12 pp. Standard Methods: For the Examination of Water and Wastewater, 15th Edition: 1980, APHA, AWWA, WPCF, Washington DC. Standard Methods: For the Examination of Water and Wastewater, 16th Edition: 1985, APHA, AWWA, WPCF, Washington DC. Stegemann, J.: 1987, 'Results of A Cooperative Study of Twelve Test Methods for Solidified Waste Characterization', Environment Canada, Wastewater Technology Centre, Burlington, Ontario, 14 pp. Thompson, D, W., Malone, P. G., and Jones, L. W.: 1979, 'Survey of Available Stabilization Technology', Toxic and Hazardous Waste Disposal, Vol. 1, R. B. Pojasek, Ed., Ann Arbor Science Publishers Inc., Ann Arbor, Michigan, pp. 9-22. Tittlebaum, M.E., Seals, R. K., Cartledge, F. K., and Engels, S.: 1985, 'State of the Art on Stabilization of Hazardous Organic Liquid Wastes and Sludges', Crit Rev Environ Control 15, 2, 179-211. Wiles, C. C.: 1987, 'A Review of Solidification/Stabilization Technology', J Hazard Mater 14, 5-21.