Use of attapulgitic clay for stabilization of pollution parameters in sewage sludge

Use of attapulgitic clay for stabilization of pollution parameters in sewage sludge 2012

Use of attapulgitic clay for stabilization of pollution parameters in sewage sludge 21016

,

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SS : Suspended Solids: ( ) TDS: Total Dissolved Solids: WHO: World Health Organization: XRD: X-Ray Diffraction Biosolids: Coliforms: Enterococci: Fecal Coliforms: Listeria: Salmonela: Sewage sludge: Sludge: ( ) Treatment VIII

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. -4. XRD, As 38%, Cu 64%, Hg 100%, Mo 52%, Pb 50%, Se (Fecal Coliforms) (E. Coli). ph. XI

ABSTRACT The use of mineral-based materials is an emerging new application in the treatment of sewage sludge with the aim of fulfilling the quality requirements for heavy metals, organic compounds and pathogens. In this way, sewage sludge from municipal waste water treatment plants can be beneficially reused providing a long-term sustainable waste management solution. The treatment technology has to be effective and affordable. This MSc Thesis presents a laboratory scale application of attapulgitic clay for treatment of sewage sludge from the municipal wastewater treatment plant of Kamari, Thera. The study objectives were to assess the effectiveness of two attapulgitic clay samples with different grain size distribution, mixed in two different proportions with the sludge material. Geochemical parameters were thoroughly studied before and after treatment of the sludge with the attapulgitic clay by measuring the total parameters prescribed by the Council Decision 2003/33/EC. Leached concentrations of all parameters were determined by applying the L/S=10 leaching procedure according to EN 12457-4. Furthermore the sludge samples were studied by X ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Lastly, the sludge samples were measured for their possible radioactive content. The mineralogical phases in the sludge sample, identified by XRD, were quartz, calcite, illite and natron. Several grains containing the elements Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, and Al were identified by SEM. Analytical results of treated sludge collected one month after the application of attapulgitic clay showed a significant reduction of water leachable fraction for several parameters: As 38%, Cu 64%, Hg 100%, Mo 52%, Pb 50%, Se 51%, Zn 38%, phenols 80%. With respect to pathogens, a significant reduction up to 99.9% for E. coli and fecal coliforms was observed. Mixing also reduced the moisture content of treated material and preserved ph values under certain conditions. It is proposed that the method is further applied in a pilot scale field experiment combined with aerobic digestion and composting in order to further reduce the organic component and pathogens in sludge. Overall, the developed laboratory scale method using attapulgitic clay as an additive is a promising sludge treatment technique at a competitive cost under present market conditions. XII

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1.3: T (South Aegean Active Volcanic Arc SAAVA). http: //www.oasp.gr/node 1.3.1. - - Budetta et al., 1984; Heiken et McCoy, 1984). ; Druitt et al., 1989; Fytikas et al.,1990; Barberi et Carapezza,1994)..., 5

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: EN 14899, Characterization of waste, Sampling of waste materials - Framework for the preparation and application of a Sampling Plan. CEN/TR 15310-1, Characterization of waste, Sampling of waste materials Part 1: Guidance on selection and application of criteria for sampling under various conditions. CEN/TR 15310-2, Characterization of waste, Sampling of waste materials Part 2: Guidance on sampling techniques. CEN/TR 15310-3, Characterization of waste, Sampling of waste materials Part 3: Guidance on procedures for sub-sampling in the field. CEN/TR 15310-4, Characterization of waste, Sampling of waste materials Part 4: Guidance on procedures for sample packaging, storage, preservation, transport and delivery. CEN/TR 15310-5, Characterization of waste, Sampling of waste materials Part 5: Guidance on the process of defining the Sampling Plan. ALB KLEIN D- 2002) (.3.1). 3.1: -EPA, 2002. - - - 34

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- SLU BLANK SL5F SL5C SL10F SL10C (mg/kg) (SLU) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) 05/10/2011 16/12/2011 16/12/2011 16/12/2011 16/12/2011 16/12/2011 Cl - 5400 3700 3670 4060 3070 3460 SO 4 5500 5640 5120 6130 4630 5360 TDS (20 ) 3200 3700 3400 3700 2800 3200 - BLANK SL5F(mg/kg) SL5C(mg/kg) SL10F(mg/kg) SL10C(mg/kg) (SLU) (mg/kg) F - 27 37 12 29 26 Cl - 3700 3650 3990 3050 3350 SO 4 4800 5100 5700 4600 4600 TDS 19000 15000 22000 14000 16000 5.6 <0.10 6,6 1.1 7.8 DOC 5300 3100 6500 3400 3900 4.4 4.5 5,6 mg/kg SLU SL10F (1,1 mg/kg SL5F <0,10 mg/kg C, 47

- DOC mg/kg SLU 3100 mg/kg SL5F, 34 10F mg/kg SL10C. 4.2.. C 4.6 4.7 4 5 BLANK SL5F SL5C SL10F SL10C (SLU) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) 0.16 0.29 0.15 0.18 0.098 <0,03 0.055 0.036 0.12 0.035 1.4 0.89 1.2 0.62 0.51 0.051 <0.002 0.0038 <0.002 0.10 0.11 0.12 0.11 0.048 0.29 0.36 0.52 0.64 0.45 0.060 <0,03 0.060 <0,03 0.032 0.18 0.10 0.16 0.089 0.11 (Zn) 1.6 1.1 1.6 1.0 1.0, 33/2003. 48

- 4.7. Mamais et al., 2009). 4.9). 86/278. BLANK SLU (mg/kg) SLU (mg/kg) SL5F (mg/kg) SL5C (mg/kg) SL10F (mg/kg) SL10C (mg/kg) 14 10 6 10 12 11 124 103 117 113 116 110 1,0 0,6 0,9 1,0 1,1 0,8 25 20 68 72 94 111 268 214 252 245 242 232 <1 2 <1 <1 1 <1 6 4 5 5 5 5 19 14 156 209 248 357 59 50 51 51 51 50 <3 <3 <3 <3 4 <3 491 397 448 437 432 413 49

- L/S = 10 l/kg 2 100 1 10 50 0,2 10 10 10 0,7 50 (Se) 0,5 L/S = Liquid / Solid : 0 (Cd) 20-40 1000-1750 300-400 750-1200 2500-4000 16-25 -. 4.3. SLU., 10%. 50

- DOC SL5F) SL10C) As (39%), Cu (64%), Hg (100%), Mo (52%), Pb (50%), Zn (38%). Hg> Cu> Mo> Pb> Se> As> Zn. 4.3. 120% 100% % 80% 60% 40% 20% 0% As Cu Hg Mo Pb Se Zn F Phenol DOC SL5C 6% 14% 93% 0% 0% 11% 0% 56% 0% 0% SL5F 0% 36% 96% 0% 50% 44% 38% 0% 100% 42% SL10C 39% 64% 100% 52% 50% 45% 38% 4% 0% 26% SL10F 0% 56% 96% 0% 50% 51% 38% 0% 80% 36% C F) (Fuerhacker and Haile, 2011). ph (Basta et al., 2005).. 4.4. coliforms, fecal coliforms glucuronidase positive E.coli, enterococci, Salmonella spp Listeria monocytogenes 51

- 4.10 4.4. 6. SLU SLU SL5F (cfu/g) SL10F (cfu/g) SL5C (cfu/g) SL10C (cfu/g) (cfu/g) (cfu/g) Coliforms 8,10E+06 9,40E+06 6,80E+06 1,40E+06 3,50E+06 1,10E+06 Fecal coliforms 4,20E+06 2,90E+04 3,50E+04 6,50E+03 2,50E+05 4,90E+04 -glucuronidase positive E. coli 2,10E+05 2,20E+04 5,50E+04 5,20E+03 1,80E+05 3,50E+04 Enterococci 1,30E+05 4,60E+04 2,50E+04 1,90E+04 5,30E+05 5,50E+04 Salmonella spp Listeria monocytogenes >> >> >> >> >> >> % 100 90 80 70 60 50 40 30 20 10 0 Coliforms Fecal coliforms - glucuronidase positive E. coli Enterococci SLU final 0 99 90 65 SL5F 16 99 74 81 SL10F 83 100 98 85 SL5C 57 94 14 0 SL10C 86 99 83 58 : SLU. SLU). 52

- Coliforms SL10C Salmonella spp Listeria monocytogenes steria.. 4.5. XRD) (SEM). 4.1. SEM S P SEM Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, Ca, Al, P, Cl, Mg, K, Si, Na. Ba, Cl, Mg, Na) 53

- (a) (b) (c) (d) 4.1: SEM a) Fe-Zn- Pb b) Pb-S-P c) Pb- S d) Fr-Cr-Ni-Cu 4.6. -. 5 ) - -40) - (Supian et al, 1997). 54

- isotope A'(Bq/kg) 235U/226Ra 6,253 0,3224 Pb-212 14,685 0,7398 Pb214/Ra224 13,126 0,6566 Rn219 6,129 0,3066 Se75 5,367 0,2723 Pa234 8,043 0,4023 Pb214 8,343 0,4178 Ac228/Ra223 26,086 1,3050 Pb214/Bi211 17,879 0,8945 Sb75/Ac228 19,712 0,9860 Be7 19,240 0,9625 Bi214 6,745 0,3475 Cs137 7,957 0,3981 Bi214 12,984 0,6495 Pb214/Bi214 107,414 5,3728 Ac228 19,421 0,9743 Ac228 22,920 1,1472 Th234 135,639 6,7847 K40 217,340 10,8716 Tl208 3,644 1,9093 SLU. K40 55

5. -

- 1.5 - -, 5.1.. 57

5.1... DOC, Hg, Cu, Mo, Pb, Se, As Zn - -, 58

59

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WWPR2012 full paper 4 fullpaper

WWPR2012 full paper A LABORATORY SCALE STUDY ON SEWAGE SLUDGE TREATMENT BY ATTAPULGITIC CLAY A. Argyraki, Assistant Professor, Faculty of Geology and Geoenvironment, University of Athens, A. E. Gidaropoulou, Graduate Environmental Geology student, Faculty of Geology and Geoenvironment, University of Athens, V. Zotiadis, Environmental Consultant, Edafomichaniki S.A., G. Kacandes, R&D Manager, Geohellas S.A. Contact: A. E. Gidaropoulou, National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, Panepistimiopolis Zographou 15784, Athens, Greece, tel: 2107274314, email: katrin.bg@hotmail.com EXECUTIVE SUMMARY The use of mineral based materials is an emerging new application in the treatment of sewage sludge with the aim of fulfilling the quality requirements for heavy metals, organic compounds and pathogens. In this way, it can be beneficially reused providing a land application of restricted amounts as a long term sustainable waste management solution for sludge from municipal waste water treatment plants. The treatment technology has to be effective and affordable. This study presents a laboratory scale application of attapulgitic clay for treatment of sewage sludge from the municipal wastewater treatment plant of Kamari, Thera. The study objectives were to assess the effectiveness of two attapulgitic clay samples with different grain size distribution, mixed in two different proportions with the sludge material. Geochemical parameters were thoroughly studied before and after treatment of the sludge with the attapulgitic clay by measuring the total parameters prescribed by the Council Decision 2003/33/EC. Leached concentrations of all parameters were determined by applying the L/S=10 leaching procedure according to EN 12457 4. Furthermore the sludge samples were studied by X ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The only mineralogical phase in the sludge sample, identified by XRD, was calcite. Several grains containing the elements Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, and Al were identified by SEM. Analytical results of treated sludge collected one month after the application of attapulgitic clay showed a significant reduction of water leachable fraction for several parameters: As 38%, Cu 64%, Hg 100%, Mo 52%, Pb 50%, Se 51%, Zn 38%, phenols 80%. With respect to pathogens, a significant reduction up to 99.9% for E. coli and fecal coliforms was observed. Mixing also reduced the moisture content of treated material. It is proposed that the method is further applied in a pilot scale field experiment combined with aerobic digestion and composting in order to further reduce the organic component and pathogens in sludge. Overall, the developed laboratory scale method using attapulgitic clay as an additive is a promising sludge treatment technique at a competitive cost under present market conditions. 90

WWPR2012 full paper 1 INTRODUCTION 1.1 Background The implementation of EU Directive 271/91/EC in Greece resulted in the operation of many wastewater treatment plants serving about 75% of the overall population. However, the quantity of sewage sludge has also increased and unfortunately is still being landfilled (Kalderis et al., 2010). Due to the increasingly stringent controls on sludge disposal the safe handling of sewage sludge in an economically and environmentally acceptable way presents an important challenge to wastewater authorities. Pollutants in sewage sludge include inorganic contaminants (e.g., metals and trace elements); organic contaminants (OCs) (e.g., polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins/ furans (PCDD/Fs), pharmaceuticals and personal care products (PPCPs), polyaromatic hydrocarbons (PAHs) and surfactants); pathogens (e.g., bacteria, viruses and parasites); and even radioactive contaminants from natural and human made sources (Fuerhacker and Haile, 2011). Several methods utilizing mineral based materials have been used in the treatment of sewage sludge (Qiao and Ho, 1997; Zorpas et al. 2000; Kalderis et al., 2010, Qu et al., 2010). The aim of such treatment technologies is finding the most effective mixing proportions at an affordable cost. Effectiveness is assessed in respect to reduction in leached inorganic and organic contaminants, pathogens and odor. A laboratory scale environmental application of modified attapulgite clay for COD removal from sewage sludge is described in the literature by Qu et al. (2010). Also one of the main commercial uses of attapulgite is elimination of odors in cat litter (Galan, 1996). Attapulgitic clay has also been successfully applied recently for the stabilization of toxic elements in contaminated land (Zotiadis at al., 2011). The fact that sludge may contain significant amounts of heavy metals (Zorpas et al., 2001; Wang et al. 2005) provides evidence that attapulgitic clay might be an effective amendment for sludge treatment. 1.2 Research objectives This study presents a laboratory scale application of attapulgitic clay for treatment of sewage sludge from the municipal wastewater treatment plant of Kamari, Thera. The study objectives were to assess the effectiveness of two modified attapulgitic clay samples with different grain size distribution, mixed in two different proportions with sludge material. 2 METHODOLOGY 2.1 Attapulgitic clay 2:1 layers, demonstrating a variable dioctahedral to trioctahedral character expressed by the following general chemical formula Mg5Si8O20(OH)2(OH2)4 2O (Galan, 1996; Gionis et al 2006). The presence of micropores and together with its fine particle size and fibrous habit are responsible for its high specific surface area and its sorption properties. The attapulgitic clay used to immobilize contaminants in this study originated from the Pefkaki deposit at Grevena, Greece (Kastritis et al, 2003). Two types of heat treated material were tested, differing in their grain size distribution; a fine grained sample (F) with particle size distribution ( m) of d10=1.8, d50= 8.9, d90= 24.8 and a coarse grained sample (C) with 90% of grains in the 20/50 mesh size. The two tested samples had also different physicochemical characteristics as presented in Table 1. 2.2 Sludge material Sludge material for the lab scale experiments originated from a plant of secondary treatment of sewage sludge located in Kamari, Thera Island. The plant accepts slurry material from 5 areas that lie in close proximity and more specifically from the municipalities of Episkopi Gonia, ExoGonia, 91

WWPR2012 full paper Vothonas and Messaria. The international airport of Thera is also served. Approximately 600 tonnes of waste is treated each year, a quantity that is indicative of the population which reaches 14000 people. TABLE 1 Physicochemical properties of attapulgitic clay samples used as sludge amendment. Sample F Sample C Moisture Content (105oC), % 19.0 7.0 ph (5% Suspension) 8.0 7.2 Apparent Bulk Density (g/cm3) 0.37 0.69 Surface Area, N2 BET (m2/g) 220 220 CEC (meq/100g) 25 25 Liquid Limit (%) 105.2 Plasticity Limit (%) 71.3 USCS Elastic Silt (MH) Poorly graded sand (SP) Mineralogy Attapulgite, Saponite, Attapulgite, Saponite, Serpentine, Quartz, Serpentine, Quartz Pyroxene 2.3 Sampling and treatment of sludge Sampling of sewage sludge material was conducted in September 2011 at the Kamari treatment plant. Collection of sludge took place at the point where the material is produced, namely at the point where the material is being rejected by the filter press and disposed into a container. Grab samples were collected using sampling equipment appropriate to the type of sewage sludge (solid) and the analytes of interest. To avoid or minimize contamination from sampling equipment, plastic equipment was used to collect samples for analyses of metals and anions, and stainless steel equipment was used to collect samples for analyses of all the organics (US EPA, 2002). A total quantity of 60 kg of waste material was collected into 5 Kg polypropylene containers. The samples were stored at 4 o C and were transported to the laboratory for treatment and analysis. Twenty four hours after collection the sludge was weighted and placed into 5 orthogonal polypropylene flower pots of dimensions 25 x 25 x 50 cm, each containing 12 kg of material. Attapulgitic clay was added into four of the sludge containing pots; the material in the fifth pot was left untreated in order to provide a reference sample (SLU). Mixing proportions of each of the fine and coarse grained attapulgitic clay samples were 5% and 10% on a dry weight basis. Sample codes of treated samples (SL5F, SL10F, SL5C and SL10C) denote the mixing proportion and the type of attapulgitic clay used (F for fine grained, C for coarse grained). The amended material was homogenized manually and the pots were kept in open air conditions protected from rain and direct sunlight for a period of 4 weeks. Mixing and homogenization of sludge was repeated on a weekly basis during this period and the ph of the material was monitored weekly. A final set of samples was removed from the pots at the end of the 4 weeks period to study the final geochemical and microbiological characteristics of sludge. 92

WWPR2012 full paper 2.4 Analytical procedures Aliquots of untreated and treated sludge samples were subjected to the L/S=10 leaching procedure with deionized water according to EN 12457 4 (2002). Chemical analysis was performed in parallel in the Laboratory of Economic Geology and Geochemistry, University of Athens and an accredited external laboratory. Appropriate analytical techniques were used for the determination of the total parameters prescribed by the Council Decision 2003/33/EC. Microbiological analysis was also performed on sludge before and after treatment to determine the following parameters: Coliforms, Fecal coliforms, glucuronidase positive E. coli, Enterococci, Salmonella spp, Listeria monocytogenes. This analysis was performed in the external accredited laboratory. Furthermore the sludge samples were studied by X ray diffraction (XRD) using a Siemens D 5005 diffractometer with Cu K radiation and scanning electron microscopy (SEM) using a JEOL JSM 5600 system at the Laboratory of Economic Geology and Geochemistry, University of Athens. 3 RESULTS AND DISCUSSION The only mineralogical phase in the untreated sludge sample, identified by XRD, was calcite. Several heavy metal bearing phases were identified by SEM in back scattered electron mode. Metals in these phases are associated with S and P within the organic matrix of sludge (Figure 1). In general SEM analysis revealed grains containing the following elements: Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, Ca, Al, P, Cl, S. A slight increase in sludge ph was observed during the experimental time period of 4 weeks (Figure 2). However, this increase is probably not related to the addition of attapulgitic clay since it was also observed in the untreated reference sample SLU. FIGURE 1 Microphotographs of SEM back scattered emission showing heavy metal bearing grains (light areas) within the organic matrix of sludge. (a) Fe Zn Pb phase, (b) Pb S P phase, (c) Pb S phase, (d) Fr Cr Ni Cu phase. 93

WWPR2012 full paper FIGURE 2 Change of ph in attapulgite treated sludge samples over a 4 weeks observation period. The effectiveness of attapulgitic clay treatment was assessed by comparing the analytical results of leached solutions of treated and untreated sludge (reference sample SLU). The results showed a significant reduction of water leachable fraction for several parameters (Figure 3). Overall the best results were achieved with the 10% mixing proportion of clay. The fine grained material performed better in removing phenol and DOC content in the leachate (100% and 42% reduction respectively in sample SL5F) but the coarse grained material (SL10C) achieved better reduction percentages for metal and metalloid parameters: As (39%), Cu (64%), Hg (100%), Mo (52%), Pb (50%), Zn (38%). The order of metal and metalloid uptake by attapulgitic clay was Hg> Cu> Mo>Pb> Se> As> Zn. These results indicate that treating the sludge with attapulgitic clay might have positive effects in reducing the mobility and thus bioavailability of toxic elements in the instance of sludge land application. However, heavy metal content of sewage sludge as reported in most research works is variable and hardly comparable (Fuerhacker and Haile, 2011). Furthermore, the fate and transport, the mobility, bioavailability and eco toxicity of potentially harmful elements in sludge amended soils depends on several factors including ph, cation exchange capacity, organic matter content, soil structure and texture (Basta et al, 2005). All of the above calls for further work in order to explore the speciation of potentially harmful elements in sludge and understand the processes controlling adsorption by attapulgitic clay. With respect to pathogens, results at the end of the experimental period in the untreated and treated samples were compared to pathogen concentrations in the initial sludge sample (Figure 4). A significant reduction in Coliforms, up to 86% was observed for sample SL10C. Samples treated with 10% fine grained attapulgitic clay achieved the best reduction in pathogens overall. It is noted that Salmonella spp and Listeria monocytogenes were absent even in the initial sample. Mixing also reduced the moisture content of treated material (Table 2). Agricultural land application is often proposed as a reasonable use of sewage sludge. Apart from its beneficial use as a fertiliser sludge land application may be used for the reclamation of degraded soils by improving soil physical properties such as porosity, aggregate stability, bulk density and water retention (Fuerhacker and Haile, 2011). In arid areas such as Thera this use is considered beneficial, provided that all risks are thoroughly assessed beforehand. Thus, the next step in this research is to test the method in a pilot scale experiment. It is proposed that the technique is applied in a small scale field experiment in combination with conventional sludge treatment methods such as composting. Break up of organic matter through the composting process increases the exchangeable fraction of metals and helps natural minerals to adsorb and immobilise them (Qiao and Ho, 1997; Stylianou et al., 2008). In this way it is anticipated that the effectiveness of mixing with attapulgitic clay will be maximised. 94

WWPR2012 full paper FIGURE 3 Reduction (%) in water leachable fraction of selected sludge parameters that showed lower concentration after treatment with different proportions of coarse (C) and fine (F) attapulgitic clay. FIGURE 4 Reduction (%) in microbiological parameters of sludge after treatment with different proportions of coarse (C) and fine (F) attapulgitic clay. TABLE 2 Change in moisture content during the 4 weeks experimental period. SAMPLE Initial Moisture (%) Final Moisture (%) Reduction (%) SLU 80.0 76.0 5 SL10F 77.2 72.5 6 SL5C 78.1 67.8 13 SL10C 78.3 65.9 16 SL5C 78.0 69.5 11 95

WWPR2012 full paper 4 CONCLUSIONS Research results indicate that the use of attapulgitic clay has a positive potential for the treatment of sewage sludge. The laboratory scale experiment showed that mixing with 10% attapulgitic clay significantly reduced the leachable concentrations of several parameters and that it is mostly effective for removal of phenol, DOC, Hg, Cu, Mo, Pb, Se, As and Zn. Treatment was also effective in the reduction of pathogen concentrations in sludge after the 4 weeks observation period. It is proposed that the method is further tested in a pilot scale field experiment combined with composting in order to further reduce the organic component and pathogens in sludge. Overall, the developed laboratory scale method using attapulgitic clay as an additive is a promising sludge treatment technique at a competitive cost under present market conditions. 5 ACKNOWLEDGEMENTS This research is financially supported partially by DEYA Thera. The authors would like to thank Mr N. Kabourakis, Mr I. Labrakis and Ms F. Karamolegou for providing background information on sewage sludge treatment plants of Thera Island and their help during sampling. REFERENCES Basta, N.T., Ryan, J.A., Chaney, R.L. (2005) Trace element chemistry in residual-treated soil: key concepts and metal bioavailability. Environ Qual, 34, 49 63. EN 12457-4 (2002) Characterisation of waste- Leaching- compliance test for leaching of granular waste materials and sludges- Part 4: One stage batch test at a liquid to solid ratio of 10 l/kg for materials with particle size below 10 mm. European Committee for Standardization. Fuerhacker, M., Haile, T. M. (2011) Treatment and reuse of sludge. In: D.Barcelo and M.Petrovic (eds.) Waste Water Treatment and Reuse in the Mediterranean Region, HdbEnvChem, 14, 63-92. Galan, E. (1996) Properties and applications of palygorskite-sepiolite clays. Clay Minerals, 31, 443-453. Gionis, V., Kacandes, G.H., Kastritis, I.D., Chryssikos, G.D. (2006) On the structure of palygorskite by mid-and near-infrared spectroscopy. American Mineralogist, 91, 1125-1133. Kalderis, D., Aivalioti, M., Gidarakos, E. (2010) Options for sustainable sewage sludge management in small wastewater treatment plants on islands: The case of Crete. Desalination, 260, 211-217. Kastritis, I.D., Mposkos, E. and Kacandes, G.H. (2003) The palygorskite and Mg-Fe smectite clay deposits of the Ventzia basin, Western Macedonia, Greece. Mineral Exploration and Sustainable Development, Proceedings of the 7th SGA Meeting, D. Eliopoulos et al., eds., Millpress, Rotterdam, 891-894. Qiao, L., Ho, G. (1997) The effects of clay amendment on composting of digested sludge, Wat. Res., 31, 1056-1064. Qu, S., Zhang, P., Wang, Y. (2010) Experiment with modified attapulgite clay on the treatment of domestic sewage. International conference on challenges in Environmental Science and Computer Engineering, DOI 10.1109/CESCE.2010.98, 196-199. Stylianou, M.A., Inglezakis, V.J., Moustakas, K.G., Loizidou, M.D. (2008) Improvement of the quality of sewage sludge compost by adding natural clinoptilolite, Desalination, 224, 240-249. US-EPA (2002) RCRA waste sampling draft technical guidance: Planning, Implementation, and Assessment. Technical report EPA530-D-02-002, Office of Solid Waste, Washington, DC 20460. 96

WWPR2012 full paper Wang, C., Hu, X., chen, M., Wu, Y. (2005) Total concentrations and fractions of Cd, Cr, Pb, Cu,m Ni and Zn in sewage sludge from municipal and industrial wastewater treatment plants. Journal of Hazardous Materials, B119, 245 249. Zorpas, A, Vlyssides, A., Zorpas, G., Karlis, P., Arapoglou, D. (2001) Impact of thermal treatment on metal in sewage sludge from the Psittalias wastewater treatment plant, Athens, Greece. Journal of Hazardous Materials, B82, 291-298. Zorpas, A., Constantinides, T., Vlyssides, A. G., Haralambous, I., Loizidou, M. (2000) Heavy metal uptake by natural zeolite and metals partitioning in sewage sludge compost. Bioresource Technology, 72, 113-119. Zotiadis, V., Argyraki, A. and Theologou, E. (2011) A Pilot Scale Application of Attapulgitic Clay for Stabilization of Toxic Elements in Contaminated Soil. Journal of Geotechnical and Geoenvironmental Engineering DOI: 10.1061/(ASCE)GT.1943-5606.0000620 (in press). 97

4 fullpaper A LABORATORY SCALE STUDY ON SEWAGE SLUDGE TREATMENT BY ATTAPULGITIC CLAY A. Argyraki, Assistant Professor, Faculty of Geology and Geoenvironment, University of Athens,argyraki@geol.uoa.gr A.E. Gidaropoulou, Post Graduate Environmental Geology student, Faculty of Geology and Geoenvironment, University of Athens, Athens, Greece, katrin.bg@hotmail.com, V. Zotiadis, Environmental Consultant, Edafomichaniki S.A., vzotiad@edafomichaniki.gr EXECUTIVE SUMMARY G. Kacandes, R&D Manager, Geohellas S.A., The use of mineral-based materials is an emerging new application in the treatment of sewage sludge with the aim of fulfilling the quality requirements for heavy metals, organic compounds and pathogens. In this way, it can be beneficially reused providing a land application of restricted amounts as a long-term sustainable waste management solution for sludge from municipal waste water treatment plants. The treatment technology has to be effective and affordable. This study presents a laboratory scale application of attapulgitic clay for treatment of sewage sludge from the municipal wastewater treatment plant of Kamari, Thera. The study objectives were to assess the effectiveness of two attapulgitic clay samples with different grain size distribution, mixed in two different proportions with the sludge material. Geochemical parameters were thoroughly studied before and after treatment of the sludge with the attapulgitic clay by measuring the total parameters prescribed by the Council Decision 2003/33/EC. Leached concentrations of all parameters were determined by applying the L/S=10 leaching procedure according to EN 12457-4. Furthermore the sludge samples were studied by X ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The only mineralogical phase in the sludge sample, identified by XRD, was calcite. Several grains containing the elements Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, and Al were identified by SEM. Analytical results of treated sludge collected one month after the application of attapulgitic clay showed a significant reduction of water leachable fraction for several parameters: As 38%, Cu 64%, Hg 100%, Mo 52%, Pb 50%, Se 51%, Zn 38%, phenols 80%. With respect to pathogens, a significant reduction up to 99.9% for E. coli and fecal coliforms was observed. Mixing also reduced the moisture content of treated material. It is proposed that the method is further applied in a pilot scale field experiment combined with aerobic digestion and composting in order to further reduce the organic component and pathogens in sludge. Overall, the developed laboratory scale method using attapulgitic clay as an additive is a promising sludge treatment technique at a competitive cost under present market conditions. Keywords:Attapulgitic clay, leaching experiments, stabilization, Santorini Greece, sewage sludge. 98

4 fullpaper 1. INTRODUCTION 1.1 Background The increasingly stringent control on safe handling and disposal of sewage sludge in an economically and environmentally acceptable way presents an important challenge to wastewater authorities. Pollutants in sewage sludge include inorganic contaminants (e.g., metals and trace elements); organic contaminants (OCs) (e.g., polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins/ furans (PCDD/Fs), pharmaceuticals and personal care products (PPCPs), polyaromatic hydrocarbons (PAHs) and surfactants); pathogens (e.g., bacteria, viruses and parasites); and even radioactive contaminants from natural and human-made sources (Fuerhacker and Haile, 2011). In Greece, the implementation of EU Directive 271/91/EC resulted in the operation of many wastewater treatment plants serving about 75% of the overall population. However, the quantity of sewage sludge has also increased and a large proportion of sludge is still being landfilled (Kalderis et al., 2010). Several methods utilizing mineral-based materials have been used in the treatment of sewage sludge (Qiao and Ho, 1997; Zorpas et al. 2000; Kalderis et al., 2010, Qu et al., 2010). The aim of such treatment technologies is finding the most effective mixing proportions at an affordable cost. Effectiveness is assessed in respect to reduction in leached inorganic and organic contaminants, pathogens and odor. The effectiveness of attapulgitic clay for environmental uses is based on its specific layers, demonstrating a variable dioctahedral to trioctahedral character expressed by the its fine particle size and fibrous habit are responsible for its high specific surface area and its sorption properties. Attapulgitic clay has been successfully applied recently for the stabilization of toxic elements in contaminated land (Zotiadis at al., 2012). The fact that sludge may contain significant amounts of heavy metals (Zorpas et al., 2001; Wang et al. 2005) provides evidence that attapulgitic clay might be an effective amendment for sludge treatment. To the best of our knowledge only one laboratory scale environmental application of modified attapulgite clay for COD removal from sewage sludge is reported in the literature by Qu et al. (2010). One of the main commercial uses of attapulgite is elimination of odors in cat litter (Galan, 1996). 1.2 Research objectives This paper presents a laboratory scale application of attapulgitic clay for treatment of sewage sludge from a municipal wastewater treatment plant in Santorini Island, Greece. The study objectives were to assess the effectiveness of attapulgitic clay in reducing (a) water leachable concentrations of potentially toxic elements and chemical compounds, (b) pathogen concentrations and (c) odor (not quantified). 2.METHODS 2.1 Attapulgitic clay The attapulgitic clay used to immobilize contaminants in this study originated from the Pefkaki deposit at Grevena, Greece (Kastritis et al, 2003). Two types of heat treated material were tested, differing in their grain size distribution; a fine grained sample (F) with particle d a coarse grained sample (C) with 99

4 fullpaper 90% of grains in the 20/50 mesh size. The two tested samples had also different physicochemical characteristics as presented in Table 1. 2.2 Sludge material Sludge material for the laboratory scale experiments originated from a plant of secondary treatment of sewage sludge located in Santorini Island, Greece. The plant accepts slurry material from 5 areas that lie in close proximity and more specifically from the municipalities of Episkopi-Gonia, ExoGonia, Vothonas and Messaria. The international airport of Thera is also served. Approximately 600 tonnes of waste is treated each year, a quantity that is indicative of the population which reaches 14000 people. TABLE 1.Physicochemical properties of attapulgitic clay samples used as sludge amendment. Sample F Sample C Moisture Content (105 o C), % 19.0 7.0 ph (5% Suspension) 8.0 7.2 Apparent Bulk Density (g/cm 3 ) 0.37 0.69 Surface Area, N2-BET (m 2 /g) 220 220 CEC (meq/100g) 25 25 Liquid Limit (%) 105.2 - Plasticity Limit (%) 71.3 - USCS Elastic Silt (MH) Poorly graded sand (SP) Mineralogy Attapulgite, Saponite, Serpentine, Quartz Attapulgite, Saponite, Serpentine, Quartz, Pyroxene 2.3 Sampling and treatment of sludge Sampling of sewage sludge was conducted in September 2011. Collection of sludge took place at the point where the material is produced, i.e. the rejection point by the filter press into a disposal container. Grab samples were collected using sampling equipment appropriate to the type of sewage sludge (solid) and the analytes of interest. To avoid or minimize contamination from sampling equipment, plastic equipment was used to collect samples for analyses of metals and anions, and stainless steel equipment was used to collect samples for analyses of all the organics (US-EPA, 2002). A total quantity of 60 kg of waste material was collected into 5 Kg polypropylene containers. The samples were stored at 4 o C and were transported to the laboratory for treatment and analysis. Twenty four hours after collection the sludge was weighted and placed into 5 orthogonal polypropylene flower pots of dimensions 25 x 25 x 50 cm, each containing 12 kg of material. Attapulgitic clay was added into four of the sludge containing pots; the material in the fifth pot was left untreated in order to provide a reference sample (SLU). Mixing proportions of each of the fine and coarse grained attapulgitic clay samples were 5% and 10% on a dry weight basis. Sample codes of treated samples (SL5F, SL10F, SL5C and SL10C) denote the mixing proportion and the type of attapulgitic clay used (F for fine grained, C for coarse grained). The amended material was homogenized manually and the pots were kept in open air conditions protected from rain and direct sunlight for a period of 4 weeks. Mixing and homogenization of sludge was repeated on a weekly basis during this period and the ph of the material was monitored weekly. A final set of samples was removed from the pots at the end of the 4 weeks period to study the final geochemical and microbiological characteristics of sludge. 100

4 fullpaper 2.4 Analytical procedures Aliquots of untreated and treated sludge samples were subjected to the Liquid/Solid =10 leaching procedure with deionized water according to EN 12457-4 (2002). Chemical analysis was performed in parallel in the Laboratory of Economic Geology and Geochemistry, University of Athens and an accredited external laboratory. Appropriate analytical techniques were used for the determination of the total parameters prescribed by the Council Decision 2003/33/EC. Microbiological analysis was also performed on sludge before and after -glucuronidase positive E. coli, Enterococci, Salmonella spp, Listeria monocytogenes. This analysis was performed in the external accredited laboratory. Furthermore the sludge samples were studied by X ray diffraction (XRD) using a Siemens D- radiation and scanning electron microscopy (SEM) using a JEOL JSM-5600 system at the Laboratory of Economic Geology and Geochemistry, University of Athens. 3. RESULTS AND DISCUSSION The only mineralogical phase in the untreated sludge sample, identified by XRD, was calcite. Several heavy metal bearing phases were identified by SEM in back scattered electron mode. Metals in these phases were associated with S and P within the organic matrix of sludge (Figure 1). In general SEM analysis revealed grains containing the following elements: Fe, Mn, Pb, Cu, Zn, Cr, Ti, Ba, Ca, Al, P, Cl, S. A slight increase in sludge ph was observed during the experimental time period of 4 weeks (Figure 2). However, this increase is probably not related to the addition of attapulgitic clay since it was also observed in the untreated reference sample SLU. The effectiveness of attapulgitic clay treatment was assessed by comparing the analytical results of leached solutions of treated and untreated sludge (reference sample SLU). The results showed a significant reduction of water leachable fraction for several parameters (Figure 3). Overall the best results were achieved with the 10% mixing proportion of clay. The fine grained material performed better in removing phenol and DOC content in the leachate (100% and 42% reduction respectively in sample SL5F) but the coarse grained material (SL10C) achieved better reduction percentages for metal and metalloid parameters: As (39%), Cu (64%), Hg (100%), Mo (52%), Pb (50%), Zn (38%). The order of metal and metalloid uptake by attapulgitic clay was Hg> Cu> Mo>Pb> Se> As> Zn. These results indicate that treating the sludge with attapulgitic clay might have positive effects in reducing the mobility and thus bioavailability of toxic elements in the instance of sludge land application. 101

4 fullpaper (a) (b) (c) (d) FIGURE 1. Microphotographs of SEM back scattered emission showing heavy metal bearing grains (light areas) within the organic matrix of sludge. (a) Fe-Zn-Pb phase, (b) Pb-S-P phase, (c) Pb-S phase, (d) Fe-Cr-Ni-Cu phase. FIGURE 2.Change of ph in attapulgite treated sludge samples over a 4 weeks observation period. However, heavy metal content of sewage sludge as reported in most research works is variable and hardly comparable (Fuerhacker and Haile, 2011). Furthermore, the fate and transport, the mobility, bioavailability and eco-toxicity of potentially harmful elements in sludge-amended soils depends on several factors including ph, cation exchange capacity, organic matter content, soil structure and texture (Basta et al, 2005). All of the above calls for further work in order to explore the speciation of potentially harmful elements in sludge and understand the processes controlling adsorption by attapulgitic clay. With respect to pathogens, results at the end of the experimental period in the untreated and treated samples were compared to pathogen concentrations in the initial sludge sample (Figure 4). A significant reduction in Coliforms, up to 86% was observed for sample SL10C. 102

4 fullpaper Samples treated with 10% fine grained attapulgitic clay achieved the best reduction in pathogens overall. It is noted that Salmonella spp and Listeria monocytogenes were absent even in the initial sample. Mixing also reduced the moisture content of treated material (Table 2). Agricultural land application is often proposed as a reasonable use of sewage sludge. Apart from its beneficial use as a fertiliser sludge land application may be used for the reclamation of degraded soils by improving soil physical properties such as porosity, aggregate stability, bulk density and water retention (Fuerhacker and Haile, 2011). In arid areas such as Santorini Island this use is considered beneficial, provided that all risks are thoroughly assessed beforehand. Thus, the next step in this research is to test the method in a pilot scale experiment. It is proposed that the technique is applied in a small scale field experiment in combination with conventional sludge treatment methods such as composting. Break-up of organic matter through the composting process increases the exchangeable fraction of metals and helps natural minerals to adsorb and immobilise them (Qiao and Ho, 1997; Stylianou et al., 2008). In this way it is anticipated that the effectiveness of mixing with attapulgitic clay will be maximised. FIGURE 3. Reduction (%) in water leachable fraction of selected sludge parameters that showed lower concentration after treatment with different proportions of coarse (C) and fine (F) attapulgitic clay. TABLE 2.Change in moisture content during the 4 weeks experimental period. SAMPLE Initial Moisture Final Moisture Reduction (%) (%) (%) SLU 80.0 76.0 5 SL10F 77.2 72.5 6 SL5F 78.1 67.8 13 SL10C 78.3 65.9 16 SL5C 78.0 69.5 11 103

4 fullpaper FIGURE 4.Reduction (%) in microbiological parameters of sludge after treatment with different proportions of coarse (C) and fine (F) attapulgitic clay. 4. CONCLUSIONS Research results indicated that the use of attapulgitic clay has a positive potential for the treatment of sewage sludge. The laboratory scale experiment showed that mixing with 10% attapulgitic clay significantly reduced the leachable concentrations of several parameters and that it is mostly effective for removal of phenol, DOC, Hg, Cu, Mo, Pb, Se, As and Zn. Treatment was also effective in the reduction of pathogen concentrations in sludge after the 4 weeks observation period. It is proposed that the method is further tested in a pilot scale field experiment combined with composting in order to further reduce the organic component and pathogens in sludge. Overall, the developed laboratory scale method using attapulgitic clay as an additive is a promising sludge treatment technique at a competitive cost under present market conditions. 5. ACKNOWLEDGEMENTS This research is financially supported partially by the Municipality and DEYA of Santorini Island. The Major of Thera Mr. N. Zorzos is acknowledged for his interest in this research. The authors would also like to thank Mr N. Kabourakis, Mr I. Labrakis and Ms F. Karamolegou for providing background information on sewage sludge treatment plants of Thera Island and their help during sampling. REFERENCES Basta N.T., Ryan J.A. And Chaney R.L., 2005.Trace element compost by adding natural clinoptilolite, Desalination, 224: 240-249. EN 12457-4, 2002.Characterisation of waste- Leaching- compliance test for leaching of granular waste materials and sludges- Part 4: One stage batch test at a liquid to solid ratio of 10 l/kg for materials with particle size below 10 mm, European Committee for Standardization. Fuerhacker M. And Haile T. M., 2011.Treatment and reuse of sludge. Waste Water Treatment and Reuse in the Mediterranean Region.In: D.Barcelo and M.Petrovic (ed.), HdbEnvChem, 14: 63-92. Galan E., 1996. Properties and applications of palygorskite-sepiolite clays, Clay Minerals, 31: 443-453. 104

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