Mine Spoil Reclamation with Sewage Sludge Stabilized with Cement Kiln Dust and Flue Gas Desulfurization Byproduct (N-Viro Soil Process)1

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MINE SPOIL RECLAMATION WITH SEWAGE SLUDGE STABILIZED WITH CEMENT KILN DUST AND FLUE GAS DESULFURIZATION BYPRODUCT (N-VIRO SOIL PROCESS)1

Dr. Terry J. Logan2

Abstract. The N-Viro Soil, patented USEPA PFRP , process stabilizes dewatered sewage sludge with alkaline admixtures to produce a dry granular product with physical and chemical properties that are ideal for reclamation of acid mine spoil. N-Viro Soil was developed to use cement kiln dust (CKD) as the alkaline admixture, but recent tests have shown that, among other reagents, flue gas desulfurization byproduct (FGD) can be just as effective. Results are presented here on physical-chemical properties of CKD and FGD produced N-Viro Soil, and use of the CKD product in a greenhouse study to reclaim abandoned mine spoil (pH< 3); plans for a large field study with a FGD product on reclamation of acidic mine spoil are discussed. CKD and FGD derived N-Viro Soil had similar physical and chemical properties with the CKD providing more K to the final product than FGD. N-Viro Soil was as effective as lime and fertilizer in above-ground growth of grass on acidic minespoil, and gave significantly greater root growth.

Additional Key Words: acid, organic waste, alkaline

Introduction 2Professor of Soil Chemistry, Agronomy Department, The Ohio Research in recent years has State University, Columbus, OH shown that organic wastes such as 43210 sewage sludge, sludge compost, livestock manure and others can be used to enhance reclamation of 1992; Hossner and Hons, 1992). drastically disturbed lands, These materials primarily provide particularly acidic mine spoils in the nutrients and organic matter, and eastern U.S. (Sapper, 1992; Logan, have to be supplemented with lime applications for reclamation of acid 1Paper presented at the 1992 spoil. A new patented process, the National Meeting of the American N-Viro Soil technology, which is Society for Surface Mining and classified by U.S. EPA as a Process Reclamation, Duluth, Minnesota, to Further Reduce Pathogens June 14-18, 1992. (PFRP), uses alkaline admixtures to

220 pasteurize and stabilize dewatered physical and chemical properties of sewage sludge (Burnham et al., N-Viro Soil produced with cement 1990). The process results in a dry, kiln dust (CKD) and with FGD, and granular product that contains use of the CKD product in a limestone, nutrients and organic greenhouse study to reclaim matter (Logan, 1990). The abandoned mine spoil (pH < 3); combination of "soil-like" physical plans for a large field study with a properties and lime, nutrients, and FGD product on reclamation of organic matter make N-Viro Soil an acidic mine spoil are discussed. excellent material for use in reclamation of acidic mine spoils. Of The N-Viro Process equal significance is the recent finding that one of the alkaline materials that can be used in the N- The N-Viro Process is Viro Soil process is flue gas summarized in Figure 1. The basis desulfurization byproduct (FGD), of the process is to destroy produced by electrical generators in pathogens through a combination of the scrubbing of S02 from high the following stresses: 1) alkaline sulfur coal. The potential, then, is to pH; 2) accelerated drying; 3) high combine two waste materials, temperature; 4) high ammonia; 5) sewage sludge and FGD, into an salts; 6) indigenous microflora. Raw environmentally acceptable and primary, activated sludge, or valuable product. digested sludge with solids content of 18-40% is used. Sludge, CKD, This paper will other alkaline reagents, and other briefly review the N-Viro Soil additives are mixed with a pug mill process, summarize important or screw blender.

Dewatered Sludge pH increases to 12

Temp rises to 52-62 OC N-Viro ) Soil • Moisture decreases to Cement Jess than 50% Kiln Dust NH3 is released Pathogens are destroyed

Beneficial microbes regrow

Figure 1. Basic reactions in the N-Viro process.

221 If the alkaline reagent contains alternative has no ambient air enough lime (Cao, Ca(OH)2 or temperature requirements. other strong alkali) to give a pH rise to > 12, and an exothermic reaction The N-Viro Soil process is an necessary to achieve desired EPA-approved PFRP process. Not temperatures (52-62 De), no other only does it rapidly destroy additive is needed. CaO is added to pathogenic bacteria and viruses, but supplement the free lime content of effectively kills Ascaris ova, the most the alkaline reagent if it is not "hot" resistant of sludge pathogens. enough. The ratio of alkaline Ascaris eggs are reduced to < 1 per reagent to sludge solids varies 5 g sludge within 6 hours. primarily with the solids content of the sludge, with a higher ratio being An important characteristic of used for sludges with lower solids N-Viro Soil is its ability to reduce content. With proper mixing speeds, sludge odors rapidly and to maintain the resultant product is a granular, a stable, odor-free product with easy-to-handle soil-like material that prolonged storage. Initial odor is further processed by one of two control is achieved by the large methods (alternative 1 or alternative surface area provided by the fine 2). grained alkaline reagent, the rapid drying which occurs with Alternative 1 windrowing, and pathogen kill. Long term odor control is maintained by The sludge/alkaline reagent the continued degradation and mixture is air dried while the pH stabilization of organic sludge solids remains above 12.0 for at least by the remaining heterothrophic soil seven days. The N-Viro Soil must be microorganisms. held for at least 30 days and until solids content is at least 65% by Characteristics of N-Viro Soil weight. Ambient air temperatures during the first seven days of General characteristics of N- processing must be above 5 De. Viro Soil are summarized in Table 1. Of significance for reclamation are Alternative 2 its high CaC03 equivalency, soil- like physical properties, and The sludge/alkaline reagent relatively balanced nutrient content. mixture is heated while the pH Logan et al. (1989) have shown that exceeds 12.0 using exothermic about 20% of the total Kjeldahl N reactions from the alkali, if required. (TKN) is mineralizable in the year of Temperatures must be 52 De application. In addition, Bennett throughout the mixture. The material (1989) showed that, even when the must be stored in such a way (e.g., pH of the material was reduced to 5 in a bin) so as to maintain uniform by acid pretreatment, EPTOX (a minimum temperatures for at least procedure developed by EPA to 12 hours. Following this heat pulse, identify hazardous wastes) the N-Viro Soil is air dried (while pH leachable metals (EPA, 1978) were remains above 12.0 for at least three greatly reduced compared to metal days) by windrowing until the solids leaching from the sludge itself. N- content is > 50% by weight. This Viro Soil has a high initial pH that is

222 Table 1. General characteristics of N-Viro Soil (Logan, 1990).

Characteristic Units Value

CKD content % bywt. 35-75 Solids content %by wt. 50-75 Material > 2 mm % bywt. 32 Mean granule size mm 0.66 Bulk density g/cm3 0.7-1.0 Volatile solids % bywt. 9.3 pH (1 :1 water) 11-12 CaC03 equivalent % bywt. 50-80 Organic-C % bywt. 12.2 Total Kjeldahl N (TKN) %by wt. 1-1.5 NH3-N mg/kg 200 N03-N mg/kg 50 p %by wt. 0.39 K %by wt. 1.0 Ca % bywt. 20 Mg % bywt. 1.0 Na % bywt. 0.2 controlled by the residual strong alkali (Ca(OH)2) in the material; Calcareous soil Ca(OH)2 is more water soluble than 12 • Acid Soll CaC03 and will control the water pH. Overall pH buffering is 11 controlled by CaC03, and we have found that soil pH drops rapidly ::c 1 (Figure 2). Soil reaction can be C. predicted accurately by adjusting -0 lime requirement for CaC03 en equivalency. use of N-Viro Soil for Abandoned Mine Spoil 5;-1-...-.-,r-r-.--.--.-....-..-~~ Reclamation 0 2 4 6 8 10 12 Time (days) Methods and Materials Figure 2. Change in soil pH with N- A greenhouse study was Viro Soil. conducted to evaluate the use of N- Viro Soil to revegetate acidic project in Perry County. The material abandoned mine spoil from eastern had a 1 :1 N-viro Soil:H20 pH of 2.9; Ohio (Prezotto and Logan, Bray P1 available P (Olsen and unpublished data). Mine spoil was Sommers, 1982) of < 2 kg/ha; collected from the Moxahala Creek exchangeable Ca, Mg and K of 210, abandoned mine reclamation

223 147 and 44 kg/ha, respectively; CEC treatment were prepared by mixing was 18 cmolc/kg and Ca, Mg and K the spoil with the amendments and base saturation percentages were 3, placing 9 kg of each mix in pots. 3 and 0.3, respectively. The N-Viro Pots were wet until saturated, Soil used in the study was made allowed to drain freely, covered with from City of Toledo waste activated plastic film and incubated for a sludge and CKD was the alkaline week. After incubation, the pots reagent. Characteristics of this were seeded with a reclamation material are summarized in Table 2. mixture of annual ryegrass, orchard The experimental design consisted grass and birdsfoot trefoil. After 89, of N-Viro Soil at rates of 50, 100 and 155 and 182 days, the plants were 200 mt/ha dry weight equivalent; harvested, dried and weighed. The and NPK fertilizer and CaC03 at roots were separated from the soil rates equivalent to that in the N-Viro by washing, dried and weighed. Soil, assuming that 20, 50 and Plant material was digested and 100% of the TKN, P and K in the N- analyzed for N, P, K, Ca, Mg, Al, Cu, Viro Soil are available and that the Fe, Zn, Na, and Mn. Samples of the material contains a CaC03 content soil were analyzed for pH, organic- of 88% (Table 2). N, P and K were C, TKN, and total P, K, Ca and Mg. applied as Ca(N03)2, Ca(H2P04)2, Selected results will be presented. and KCI. Four replicates of each

Table 2. Characteristics of the N-Viro Soil used in the reclamation study. All concentrations are on a dry weight basis.

Parameter Units Value

Water content % bywt. 50.1 pH (1 :1 H20) 12.5 CaC03 equivalent % 88.4 TKN % bywt. 0.5 Total p % bywt. 0.24 K % bywt. 0.89 Ca % bywt. 33.4 Mg % bywt. 11.1 Cd mg/kg 4.8 Cu mg/kg 49.9 Ni mg/kg 478 Zn mg/kg 262 Cr mg/kg 599 Pb mg/kg 1350 Mn mg/kg 166

mixture was placed in a plastic bag In a separate component of and wet to 20% H20 by wt. The the study, 1 kg of each treated spoil sealed bags (opened periodically

224 for air exchange) were placed in the N-Viro Soil and LF gave similar greenhouse next to the pots, above-ground biomass responses incubated, and samples removed at as predicted, but N-Viro Soil at 200 intervals of 1, 4, 8, 16 and 24 weeks. mt/ha gave greater root biomass This was done to study changes in than LF. soil solution chemistry for interpretation of the growth results. Chemical composition of the The samples were water saturated above-ground biomass is presented for 24 hours and the soil solution in Figure 4 for the 89 day cutting. was then removed by centrifugation and filtration. The filtrate was analyzed for pH, EC, total C, total organic C, Cl, S04, N03, P04, Ca, 11111 Nitrogen Mg, and K. All analyses were made with standard procedures (Page et i rl Phosphorus >, al., 1982) and on duplicate samples. .0 !Ill Potassium Selected results will be presented. -'*C 4 Results and Discussion .!!-.. C Above-ground and root --"' C biomass are presented in Figure 3 "0 for N-Viro Soil and lime and fertilizer 0 (LF) equivalents.

c:, .. NV-50 NV-100 NV-200 LF-50 LF-100 LF-200 Ill Plant biomass (89 days) Ill Root biomass (182 days c:,

- c:, ..."' 0 c:, Ill Aluminum -... "' c:, -Ol T" II Boron Ol - ...- c:, Iii Zinc - c:, Ol j ,ct - .. .. E -C c:, 0 U) == .: >, .. - c:, c.,. - c:, -~

Figure 3. Plant and root biomass on Figure 4. Chemical composition of acidic mine spoil with N-Viro Soil plant biomass on minespoil with N- (NV) or lime and fertilizer (F). Viro Soil and lime/fertilizer.

225 The results for the 155 and 182 day 15 cuttings were generally similar and Ill LF-50 D NV-50 are not presented. Nutrient levels 14 were similar for the N-Viro Soil and ...... -4r ...... LF-100 ·······,&······ NV-100 LF treatments and there were no 13 ----•--· LF-200 ----€>--· NV-200 significant differences between the two sources. This suggests that the 12 eA ...... , e·--·-e.. -- assumptions made as to nutrient :c ···4...... -- ... availability in the N-Viro Soil are Q. 11 '··,.a 'O reasqnable. Aluminum levels were 0 ...... _ ..... Q. ·· higher with N-Viro Soil than with LF, ti) 10 ·,. particularly at the highest rate. This ...... ·...... could have been due to the very 9 ...... ll, ·- hi.gh initial pH of the amended spoil --s-····...::····::-···,,...... e with the 200 mt/ha N-Viro Soil 8 treatment (see below); Al solubility I·· 0 , I·, .. -1--- ..... ::oao~lfl,oa, increases at alkaline pH due to the 7 • formation of Al(OH)4- in solution. 0 5 10 15 20 25 Zinc and B concentrations were also Time (weeks) higher with N-Viro Soil; significant amounts of Zn were added with the Figure 5. Changes in soil solution N-Viro Soil (Table 2), and, although pH in acidic mine spoil with N-Viro B content of the N-Viro Soil was not Soil (NV) and lime/fertilizer (LF). determined, it was probably high enough to increase the levels A major difference in soil relative to the unamended spoil.· solution composition between the None of the levels of trace metals LF and N-Viro Soil treatments was studied were considered to be in dissolved organic C (DOC) excessive (Adriano, 1986). content (Figure 6). Levels in the LF treatments were < 5 mg/L, typical of Analysis of the soil solution concentrations found in mineral showed that all of the lime ground water environments. Initial treatments raised pH in the range of DOC in the N-Viro Soil treatments 7.5 (Figure 5) while the N-Viro Soil ranged from 200 to 600 mg/L, treatments gave initial pHs that generally declining with time, ranged from 11 to 12.5, decreasing presumably as a result of microbial to about 8.5-9 with time. This decomposition. There are several suggests that there was an excess consequences of this finding. On a of CaC03 in the lime treatments to positive note, movement of DOC into buffer pH, while the decrease in pH the subsoil of mine spoil with the N-Viro Soil confirms the environments could increase rapid neutralization of the Ca(OH)2 biological activity and help to alkalinity with eventual buffering by stimulate root growth as was CaC03. The rate of pH decline was observed in this study (Figure 3). slower than observed for soils DOC could also complex potentially (Figure 2), probably because of the toxic trace metals. On the other low exchange capacity and coarse hand, high levels of DOC stimulate particle size of the spoil. denitrification and this could result in reduced available N levels. In fact,

226 these technologies is the lime Ill LF-50 ---&-- NV-50 injection multistage burner (LIMB) ...... LF-100 -·-a-.. NV-100 process. It has been used in a full LF-200 --0-· NV-200 scale demonstration at a coal-fired, 0 ····•··· o~~~~~~~~~~~~~ 105 megawatt boiler at Ohio cu Edison's Edgewater plant. The ::J'. , 0------~ \ \ process involves injection of lime as -~ , , \ E o , ' a finely atomized mist into the upper - Q. (0 ,. ,.© ' ' (.) part of a suspension-fired boiler e ' \ where it reacts with S02 at .~ \ C O \ temperatures ranging from 2,000 to cu O" [!) \ 2,300 150 250 l:' ...... ·,. \ OF. About to dry tons 0 .-·- \ of FGD are produced daily at this [3•'"'' -El '·,. (!) ~ ~ plant. Nationwide projections for ~ Q '·.. 0 o. .. production of FGD as power plants U) N t,...... A.. .. !!l ...... 1::]- .... ___ , ... adopt these technologies are in the C ~"'--...... '"··[:] millions of dry tons annually. Of •f:E------A .. . concern is how to efficiently utilize 0 - - I ' ' this byproduct in an environmentally 0 5 ' 10 15 20 25 acceptable manner. As part of a Time (weeks) larger project, funded by the Ohio Coal Development Board, Dravo Figure 6. Changes in soil solution Lime Company, and DOE, dissolved organic C in acidic mine investigating beneficial reuse of spoil with N-Viro Soil (NV) or FGD, exploratory research was lime/fertilizer (LF). conducted to determine if the LIMB FGD could be utilized as an nitrate-N levels in the N-Viro Soil alternative alkaline reagent in the treatments were < 1 mg/L compared production of N-Viro Soil. to concentrations of 100-600 mg/L with the fertilizer treatments. Samples of LIM~ FGD were Nevertheless, N levels in plant tested by N-Viro Energy Systems, tissue (Figure 4) were similar for the Inc. and were shown to produce the two treatments. heat and pH rise specified in the N- Viro Soil process. Analysis of the N-Viro Soil Produced From resulting product is summarized in .EQQ Table 3. Values are generally in the range observed for other N-Viro Soil Flue gas desulfurization materials (Table 1). Samples of the (FGD) byproducts are produced as a N-Viro Soil and the LIMB FGD were result of new technologies for extracted with water (20:1 H20 to removal of S02 emissions from solid, 18 hr) and the N-Viro Soil was burning of high-S eastern coals. The also subjected to the EPTOX various technologies result in leaching extraction with pH 5 acetic materials of varying chemical acid used for the analysis of composition and physical potentially hazardous wastes. characteristics, but generally consist Analyses were performed by ICP in of physical and chemical mixtures of the Agronomy Department, Ohio fly ash, gypsum and unreacted lime Ag ri cultural Research and (CaO) or limestone (CaC03). One of

227 Table 3. Analysis of N-Viro Soil using Toledo sludge and FGD as the alkaline reagent.

Parameter Units Value

Solids % bywt. 54.1 Bulk density g/cm3 1.32 CaC03 Equivalent % 29 TKN %by wt. 0.57 NH3-N % bywt. 0.26 Total p % bywt. 0.78 K % bywt. 0.09 Ca %by wt. 14.7 Mg %by wt. 0.59 B %by wt. 150 Cd %by wt. 3.6 Cu % bywt. 130 Pb % bywt. 73 Mn % bywt. 180 Ni %by wt. 161 Zn %by wt. 490 Analyses performed by Brookside Labs, New Knoxville, OH.

associated with these materials, while the N-Viro Soil contained Development Center, Wooster, more K, Na, P, Ni, Cu, Zn and F, all Ohio. Results are given in Table 4. normally found in sewage sludges. Concentrations in the EPTOX and water extracts of N-Viro Soil were The results of these analyses similar in most cases; major suggest that the LIMB FGD- differences were in Mg and Si which produced N-Viro Soil can be safely were much higher in the EPTOX used as a soil amendment, and extract. The final EPTOX extract pH several field studies have been of 7.41 is not that different from planned for 1992 to test this water and resulted from material. In the first study, the neutralization of the acetic acid by material described here will be used the residual alkalinity in the N-Viro to revegetate previously mined Soil. The free acetate ligand would · areas in eastern Ohio at a rate of have mobilized some metals, about 1oo mVha. Observations on enough to account for the observed plant growth will be made. In the differences. There were few major second, more comprehensive study, differences in water extractable N-Viro Soil produced with Toledo elements between the LIMB FGD sludge and and FGD to be specified and N-Viro Soil, and these were later will be used to reclaim an predictable. The LIMB FGD abandoned mine spoil site near contained more total S and sulfate, Dover, .Ohio in conjunction with the and B, elements normally Ohio Department of Natural

228 Table 4. Leachate analysis of lime injection multistage burner (LIMB) flue gas desulfurization (FGD) byproduct and N-Viro Soil made from Toledo sludge and LIMB FGD as the alkaline reagent.

Parameter EPTOX (pH 5) Water Extract

N-Viro Soil N-Viro Soil LIMB FGD pH 7.41 10.65 10.63

Total analysis (mg/L)

Al 0.23 0.08 0.13 Ca 3767 1140 1735 Mg 110 0.03 nd Fe 2.18 0.03 nd K 9.99 5.04 2.31 Mn 2.17 nd nd Na 6.95 3.91 1.53 p 2.50 1.07 nd s 544 206 624 Ba 0.33 0.54 0.26 Co 0.03 nd nd Ni 0.96 1.22 nd Sr 3.51 1.77 2.44 V 0.08 nd nd As nd nd nd Cd nd nd nd Cr nd nd nd Cu 0.73 1.73 nd Hg nd nd nd Pb nd nd nd Se nd nd nd Si 12.29 0.46 0.19 Zn 0.66 0.19 nd B 2.75 0.32 3.66 Be nd nd nd u 0.02 nd 0.06 Mo 0.16 0.10 0.10 Sb nd nb 0.27 F 12.0 3.5 Cl 28.4 66.9 S04 27.7 1577

229 Resources Abandoned Mine FGD study was conducted in Reclamation Program. N-Viro Soil cooperation with Mr. Joel Beeghly, will be applied at a rate of Dravo Lime Company, Pittsburgh, approximately 200 mt/ha to paired PA, and Mr. Kyle Grathwol, National N-Viro Tech, Inc., Fremont, OH. Dr. watersheds of approximately 1-ha Richard Stehower, OARDC, size; another set of paired Wooster, OH, performed the watersheds will receive lime and leaching studies. Funds for the LIMB fertilizer as amendments for study were provided by the Clean comparison. The watersheds will be Coal Development Office, Ohio instrumented with flumes and Department of Development, DOE subsurface monitoring equipment to Morgantown Energy Technology monitor and sample surface and Center, and EPRI. ground water for chemical analysis. Vegetative growth will also be References monitored. Smaller, replicated plots will receive similar treatments and a Adriano, D. C. 1986. Trace elements portable rainfall simulator will be in the terrestrial environment. used to determine changes in Springer-Verlag, New York, NY. erodibility of the reclaimed surface following treatment and Bennett, G.F. 1989. Effects of revegetation. cement kiln dust on the mobility of heavy metals in treatment of summary wastewater treatment plant sludge. Final Report. Thomas Edison A new sewage sludge Program. Ohio Dept. Dev., stabilization process, the N-Viro Soil Columbus. 90 pages. process, has been shown to produce a dry, granular, "soil-like" Burnham, J.C., N. Hatfield, G.F. material that has properties that are Bennett and T.J. Logan. 1990. Use ideal for mine spoil reclamation. In of quicklime and cement or lime kiln addition, recent work has shown that dust for municipal sludge coal scrubber waste, FGD, can be pasteurization and stabilization with used in the N-Viro Soil process as the N-Viro Soil process. Symp. on an alternative alkaline reagent, Innovation and Uses for Lime. producing a material that has ASTM. promise for reuse in the electricity gen.eration industry for coal mine Hossner, L.A. and F.M. Hons. 1992. reclamation. Reclamation of mine tailings. Adv. Soil Sci. 17:311-350. Acknowledgments Logan, T.J. 1990. Chemistry and The greenhouse study was bioavailability of metals and conducted by Dr. Maria Prezotto, nutrients in cement kiln dust- ESALQ, University of Sao Paulo, stabilized sewage sludge. Proc. Piricicaba, Brazil, while she was a Specialty Conf. on Sludge visiting scientist in Dr. Logan's Management. Water Pollution laboratory. Funds were provided by Control Fed., Alexandria, VA. the Ohio Edison Program. The LIMB

230 Logan, T. J. 1992. Reclamation of Page, A.L., R.H. Miller and D.R. chemically degraded land. Adv. Soil Keeney. 1982. Methods of Soil Sci. 17:13-35. Analysis, Part 2. Chemical and Microbiological Properties. Soil Sci. Logan, T. J., B. Harrison and M. D. Soc. Am., Madison, WI. Che. 1989. Agronomic effectiveness of cement kiln dust-stabilized Sopper, W.E. 1992. Reclamation of sludge. Final Report. Thomas mine land using municipal sludge. Edison Program. Ohio Dept. Dev., Adv. Soil Sci. 17:351-432. Columbus. 3 pages. U.S. Environmental Protection Olsen, S.E. and L.E. Sommers. Agency. 1978. Hazardous waste, 1982. Phosphorus. pg. 403-430. ln proposed guidelines and A.L. Page et al. (ed.) Methods of Soil regulations and proposal on Analysis, Part 2. Chemical and identification and listing. Federal Microbiological Properties. Soil Sci. Register. Vol. 43, No. 243. Soc. Am., Madison, WI.

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