INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 5, No 1, Copyright by the authors - Licensee IPA- Under Creative Commons license 3.

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1 INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 5, No 1, 2014 Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0 Research article ISSN Uptake of heavy metals by natural zeolite during agitated pile composting of water hyacinth composting Jiwan Singh * and Ajay S. Kalamdhad Department of Civil Engineering, Indian Institute of Technology Guwahati (IITG), Guwahati Assam (India) *Corresponding author jiwansingh95@gmail.com Tel: , Fax: doi: /ijes ABSTRACT The studies were carried out on heavy metal bioavailability and leachability during water hyacinth composting mixed with cattle manure, sawdust and natural zeolite. The water hyacinth, cattle manure and sawdust were taken in the 6:3:1 ratio with 5, 10 and 15% natural zeolite and composted for 30 days. The concentrations of nutrients and total heavy metals were increased during the process. Due to addition of natural zeolite initial ph of the compost mixture was increased slightly in comparison to control, resulting a decrease in bioavailability and toxicity characteristics leaching procedure (TCLP) extractable metal concentration in the final compost. Water solubility of Ni, Pb and Cd, and diethylene triamine penta acetic acid (DTPA) extractablity of Pb and Cd were not found during the composting process. Addition of natural zeolite significantly reduced the bioavailability and leachability of heavy metals during water hyacinth composting process. Keywords: Composting, heavy metals, bioavailability, leachability, natural zeolite treatment 1. Introduction Water hyacinth (Eichhornia crassipes) is a free floating and most commonly used plant in constructed wetlands because of its fast growth rate and accumulation capacity for several heavy metals (Malik, 2007; Rai, 2009; Singh and Kalamdhad, 2012a). Composting is the most economical ways for the treatment and final disposal of water hyacinth since it combines material recycling and biomass disposal (Villasenor et al., 2011; Singh and Kalamdhad, 2012a). However, the major disadvantage of water hyacinth composting is the high concentration of heavy metals in the final compost (Singh and Kalamdhad, 2012a; 2013a) due to accumulation of heavy metals in their body parts. Heavy metals uptake through plants and successive accumulation along the food chain is a potential danger to animal and human health (Wong and Selvam, 2006). The evaluation of bioavailability and leachability of heavy metals during the composting process gives more considerable information about toxicity rather that total metal concentration (Nair et al., 2008). Before deciding compost suitability for land application, must be assess bioavailability (water solubility and plant availability) and leachability of specific metals. The water soluble fraction of metal is most eagerly bioavailable in compost applied to soils. Water soluble metals are positively more biologically dynamic, resulting the highest potential of contaminating food chain, surface water and ground water (Hsu and Lo, 2001). It has been considered that DTPA-extractable fraction of metals represent plant available metals (Fang Received on March 2014 Published on July

2 and Wong, 1999; Fuentes et al., 2006). Leachability of metals can be defined as the ratio of the amount of a heavy metal released from TCLP to its total concentration; it is commonly used to assess the leachability of heavy metals in the compost and amended soil (Chiang et al., 2007). Application of natural zeolite for immobilization of heavy metals in the water hyacinth compost is one of the ways for improvement of the physical and chemical properties of the compost. Zeolite can be used as a bulking material in composting process. It improves the composting process and the biodegradability of the organic matter due to its ability to increase the porosity of the substrate (Zorpas et al., 2000). On other hand, natural zeolite has been used widely for reducing mobility and bioavailability heavy metals in sewage sludge composting due to its sorption and exchangeable properties towards the heavy metals (Zorpas et al., 2000; Sprynskyy et al., 2007). Natural zeolite has the ability to uptake of heavy metals which are in easily available fractions, and exchange of sodium and potassium (Zorpas et al., 2000; Singh and Kalamdhad, 2012b). A limited literatures are available on bioavailability and leachability of heavy metals during water hyacinth composting (Singh and Kalamdhad, 2012a and 2013a). But there is no information available on bioavailability and leachability of heavy metals during water hyacinth composting mixed with natural zeolite. Therefore the aim of the present study was to examine the bioavailability and leachability of the heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during composting of water hyacinth mixed with cattle manure, sawdust and natural zeolite. 2 Materials and Methods 2.1 Feedstock materials Water hyacinth, cattle manure (cow dung) and sawdust was used for preparation of different waste mixtures. Water hyacinth was collected from the Amingoan industrial area near Indian Institute of Technology Guwahati campus, Assam, India. Cattle manure was collected from dairy farm near the campus. Sawdust was purchased from nearby saw mill. Natural zeolite (powder form) was purchased from G. M. chemicals Pvt. Ltd., Gujarat, India. Singh and Kalamdhad (2012a, 2013a) suggested that mixture of 90 kg water hyacinth, 45 kg cattle manure and 15 kg sawdust was best combination for reduction of bioavailability of heavy metals during water hyacinth composting, therefore in this study same combination was used with 0, 5, 10 and 15% natural zeolite (clinoptilolite). The composition of waste materials in control and zeolite treatments is given in table 1. Table 1: Composition of waste materials Waste materials (kg) Treatments Water hyacinth (kg) Cattle manure (kg) Sawdust (kg) Natural zeolite (%) Control

3 Zeolite Zeolite Zeolite Before starting composting process, the maximum particle size in the mixed waste was restricted to 1 cm in order to provide better aeration and moisture control. The initial characterizations of water hyacinth, cattle manure and sawdust are explained elsewhere (Singh and Kalamdhad, 2013a). Some initial characterizations of natural zeolite are given as follows: ph-8.85±0.05, EC (ds/m)-1.58±0.03, moisture content (%)-3.75±0.15, volatile solids (%)-11.73±0.03, nutrients in mg/kg (Na-7100±100, K-1850±100, Ca-6575±0.08 and Mg-1175±125). The heavy metals concentration of natural zeolite is given in table 2. Figure1 shows Scanning electron microscopy of natural zeolite. 2.2 Design of agitated pile composting Four different waste combinations were prepared into trapezoidal piles (length 2100 mm, base width 350 mm, top width 100 mm and height 250 mm, having length to base width (L/W) ratio of 6). Composting period for agitated pile composting was decided 30 days (Singh and Kalamdhad, 2012a, 2013c). Agitated piles contained approximately 150 kg of different waste combinations and it was manually turned on 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 th day. The samples from the piles were collected after turning at 0, 6, 12, 18, 24 and 30 th day during the composting process. Table 2: Heavy metals concentration of natural zeolite (mean ± SD, n=3) Heavy metals Total metals (mg/kg dry matter) Water soluble metals (mg/kg dry matter) DTPA extractable metals (mg/kg dry matter) TCLP extractable metals (mg/kg dry matter) Zn 6.61± ± ± ±0.74 Cu 1.15± ± ± ±0.10 Mn 4.60± ± ± ±0.03 Fe 8.10±0.26 ND 1.05± ±0.05 Ni ND ND ND ND 3

4 Pb 0.72±0.07 ND ND 0.02±0.00 Cd ND ND ND ND Cr 0.08±0.00 ND ND ND Note: SD-standard deviation, ND-not detected 2.3 Experimental analysis The temperature was monitored using digital thermometer during the composting process. Each sample was analyzed for the following parameters: ph, electrical conductivity (EC) (1:10 w/v waste: water extract) and organic matter (Singh and Kalamdhad, 2012a). Flame photometer (Systronic 128) was used for analysis of Na, K and Ca concentration and atomic absorption spectrometer (AAS) (Varian Spectra 55B) was used for analysis of Mg, Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr concentration after the digestion of 0.2 g sample with 10 ml of H2SO4 and HClO4 (5:1) mixture in block digestion system (Pelican Equipments Chennai- India) for 2 hrs at 300 o C. Water-soluble and DTPA extractable heavy metals were determined according to Singh and Kalamdhad (2013b). The standard toxicity characteristic leaching procedure (TCLP) method according to EPA Method 1311, 1992 was applied to the solid samples in order to determine the potential leachability of heavy metals. According to this method, 5 g solid sample (size less than 9.5 mm) with 100 ml of acetic acid at ph 4.93 ± 0.05 (ph was adjusted by 1 N NaOH) (sample: solution ratio =1:20) was taken in 125 ml reagent bottle and kept at room temperature for 18 h in a shaker at 30±2 rpm. The suspensions were centrifuged for five minutes at 10,000 rpm, and then it was filtered through Whatman no. 42 filter paper and stored in a plastic reagent bottle at 4 o C for analysis of selected heavy metals. All the results reported are the means of three replicates. Repeated measures treated with analysis of variance (ANOVA) was made using Statistica software. The objective of the statistical analysis was to determine any significant differences among the parameters analyzed for different trials. Extraction efficiency of DTPA extractable heavy metals was calculated using following Eq. (Singh and Kalamdhad, 2013a) C DTPA Extraction Efficiency (%) = 100 C Total (1) where, CDTPA: concentration of DTPA extractable heavy metal; CTotal: concentration of total heavy metals. 4

5 Figure 1: Scanning Electron Microscopy of natural zeolite Figure 2: Variation of temperature during pile composting with zeolite 5

6 Results and discussion 3.1 Physico-chemical analysis Figure 2 shows the changes in temperature profiles in control and all zeolite treatments during the composting process. The temperature was observed in the range of o C in control and zeolite treatments during the thermophilic phase as results of the extreme microbial activity (Chiang et al. 2007). The thermophilic phase was started slightly later in zeolite treatments in comparison to control but highest thermophilic temperature was similar as control except zeolite 3. It could be explained as microbes takes slight more time for acclimatization with zeolite compost mixture than control. Addition of zeolites might be reduced the self heating property of composting process due to the bulking effect, which increased the transport of mass and energy to the atmosphere. A similar effect also reported by Villasenor et al. (2011). Figure 3a shows the significant variation in ph values from 6.38 to 7.85 during the composting process (F =18.1, p < 0.001). The initial ph values of compost mixture were increased a little in all zeolite treatments in comparison to control. The ph decreased slightly in the beginning of the composting process may be due to acid formation during the decomposition of organic matter, a similar results also observed by (Zorpas et al., 2000). The ph in initial feed mixtures of zeolite higher than control but at end of composting ph reduced and became similar as control. It might be due to buffering capacity of composting process (Garg and Gupta, 2011). Figure 3b shows the significant reduction in moisture content in control and all zeolite treatments during the process (F = 92.8, p < 0.05). The higher reduction of moisture content was observed in control (55.25%) followed by zeolite 1 (52.38%), zeolite 2 (50.66%) and zeolite 3 (47.18%) treatments. Lower reduction of moisture content in all zeolite treatments might be due to moisture retained by zeolite (Villasenor et al., 2011). Figure 3c shows the significant reduction in organic matter in control and all zeolite treatments during the process (F = 25.4, p < 0.001). The higher reduction of organic matter was observed in zeolite 1 (47.4%) followed by zeolite 2 (43.5%), zeolite 3 (31.2%) and control (23.0%). It could be explained as the biodegradation of organic matter was progressed by the addition of zeolite (Villasenor et al., 2011). Lower organic matter was observed in all zeolite treatments compared to the control during composting period. Zeolite has the ability to increase the porosity of the composting materials due to its bulking property, consequently enhanced the biodegradability of the organic matter (Zorpas et al., 2000). Measurement of EC during the composting process reflects the salinity of the composting products and high EC will hinder plant rooting (Singh and Kalamdhad, 2013a). The EC was increased from 3.13 to 3.35 ds/m, 3.39 to 3.52 ds/m and 3.40 to 3.57 ds/m in zeolite 1, 2 and 3 treatments; however it was reduced in control from 6.42 to 4.71dS/m during the composting process (Figure 3d). An increase in EC during composting process also reported by other researcher (Zorpas and Loizidou, 2008; Chiang et al., 2007). The EC value was lower in the all zeolite treatments in comparison to control due to the unique properties of natural zeolite (Chiang et al., 2007). The significant variation in EC was observed in control and all zeolite treatments during the process (F = 165.1, p < 0.05). Figure 4 illustrates the significant variation in concentration of the nutrients as Na (F =4.12, p < 0.001), K (F = 7.27, p < 0.001), Ca (F = 29.47, p < 0.001) and Mg (F = 19.77, p < 0.001) which increased significantly in control and zeolite treatments throughout the composting 6

7 process. The concentration of Na, K, Ca and Mg was increased during composting process due to the net loss of dry mass. Similar results also reported by Singh and Kalamdhad (2013a and 2013b). Figure 3: Variation of physico-chemical parameters (a) ph (b) moisture content (c) organic matter and (d) electrical conductivity (EC) during the composting process (bars denoted as ± standard deviation) Figure 4: Variation of nutrients (Na, K, Ca and Mg) during composting process (bars denoted as ± standard deviation) 7

8 Figure 5 illustrates the variation in total concentration of metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) in control and all zeolite treatment during 30 days of composting period. The total concentration of metals was increased due to reduction of organic matter and release of CO2 during the mineralization processes (Zorpas et al., 2000, Singh and Kalamdhad, 2012a and 2013a, 2013c). The total concentration of heavy metals obtained after strong acid digestion is indicator of pollution but unable to provide useful information of bioavailability of heavy metals in the compost and compost amended soil (Cai et al., 2007). The variation in Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr concentrations in control and zeolite amended compost were significant (F = 7.36, p < for Zn, F = 42.72, p < 0.05 for Cu, F = 45.15, p < 0.05 for Mn, F = 50.59, p < 0.05 for Fe, F = 42.31, p < 0.05 for Ni, F = 8.96, p < for Pb, F = 26.49, p < for Cd, F = 4.37, p < for Cr). Figure 5: Variation of total metals concentration (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during the composting process (bars denoted as ± standard deviation) 3.2 Bioavailability of heavy metals during composting process Water solubility of heavy metals The water soluble fraction of heavy metals in the compost was lower as compared to their total concentration which is most toxic fraction in the compost to plants (Fang and Wong, 1999). Table 3 shows the changes in water-soluble Zn, Cu, Mn, Fe and Cr concentration in contol and all zeolite treatments during the composting process. The water solubility of metals (percentage of total metal) was reduced in the ranges: % for Zn, % for Cu, % for Mn and % for Cr in control and all zeolite treatments. Higher reduction of water soluble concentration of Zn was observed in control followed by zeolite 1, 8

9 2 and 3 treatments. Higher water soluble concentration of Cu and Mn was reduced in zeolite 1 and 2 treatments respectively during the process. Higher reduction of water soluble concentration of Fe was observed in zeolite 2 (70.50%) followed by zeolite 1 (65.64%), zeolite 3 (47.76% of total Fe), however its concentration was increased in control during the process. Water soluble concentration of Cr was reduced 100% of total Cr in zeolite 1 and 2 treatments. It was reduced about 75.99% and 61.12% of total Cr in control and zeolite 3 treatment respectively. Water soluble concentration of Ni, Pb and Cd were not detected in all treatments during the composting process. Addition of zeolite caused a significant reduction in water soluble Cu, Mn, Fe and Cr contents during the composting process. Similar results reported by Stylianou et al. (2007) during the sewage sludge composting with natural zeolite. Furthermore, the water soluble concentration heavy metals reduced during the process could be explained as higher reduction of organic matter and the formation of organo-metallic complexes (Fang and Wong, 1999; Singh and Kalamdhad, 2013c). Stylianou et al. (2007) reported that the organic matter in soluble and insoluble forms plays important role in water soluble metals reduction. Decomposition of organic matter during composting process enhanced the conversion of stable form metals into exchangeable form, as results of binding with natural zeolite through ion exchange process (Stylianou et al., 2007). The variation in water soluble Zn, Cu, Mn, Fe and Cr concentrations in control and zeolite treated compost were significant (F = 39.69, p < for Zn, F = 27.04, p < for Cu, F = 23.18, p < 0.05 for Mn, F = 58.55, p < 0.05 for Fe, F = 23.75, p < for Cr). Table 3: Changes in water soluble metals concentration during composting process (mean ± SD, n=3) Water soluble metals concentration Days Zn (mg/kg) Cu (mg/kg) Control Zeolite 1 Zeolite 2 Zeolite 3 Control Zeolite 1 Zeolite 2 Zeolite ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.13 9

10 ± ± ± ± ± ± ± ±0.22 Days Mn (mg/kg) Fe (mg/kg) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±2.10 Days Cr (mg/kg) Ni, Pb and Cd (mg/kg) ± ± ± ±0.05 ND ND ND ND ± ± ± ±0.05 ND ND ND ND ± ± ± ±0.11 ND ND ND ND ± ± ± ±0.03 ND ND ND ND ± ± ± ±0.03 ND ND ND ND ±0.04 ND ND 0.38±0.08 ND ND ND ND Mean values in columns are statistically different (ANOVA; P < 0.05), ND- not detected Plant availability of heavy metals (extraction with DTPA) The DTPA extractable heavy metals represent a supplemental approach to check the bioavailability of metals in compost and soil (Bragato et al., 1998; Singh and Kalamdhad, 2013a). The DTPA extraction efficiency of metals were reduced in the ranges: % for Zn, % for Cu, % for Mn, % for Ni and % for Cr 10

11 (Figure 6) in control and all zeolite treatments. The maximum DTPA extraction efficiency of Cu and Mn were reduced in control when compared with zeolite treatments. The maximum DTPA extraction efficiency of Zn and Cr were reduced in all zeolite treatments in comparison to the control. Higher reduction of DTPA extraction efficiency of Ni was observed in zeolite 2 treatment followed by zeolite 1 treatment and control. Higher extraction efficiency of Fe was reduced in zeolite 1 (65.0%) followed by zeolite 2 (62.2%) and Zeolite 3 treatments (43.2%); however it was enhanced in control during the composting process. Figure 6: Variation of DTPA extractable metals (Zn, Cu, Mn, Fe, Ni and Cr) during the composting process The reduction of DTPA extractability of Zn, Cu, Ni and Cr was also observed by Chiang et al. (2007) during the sewage sludge composting with natural zeolite. DTPA extractable heavy metal reduction attributed to mechanism of ion-exchange processes, where processes metal cations exchanged with mainly Na, K and Ca during the composting process (Erdem et al., 2004; Zorpas et al., 2000). Furthermore, reduction in DTPA extractable metals at the end of the composting process might be due to transformation of organic matter leads to the formation of metal-humus complexes, which make the metals insoluble and therefore less easily extractable (Garcia et al., 1995). DTPA extractable concentration of Pb and Cd were not detected in all treatments during the composting process. The variation in DTPA extractable Zn, Cu, Mn, Fe, Ni and Cr concentrations in control and zeolite treated compost were significant (F = 67.5, p < 0.05 for Zn, F = 11.97, p < for Cu, F = 87.9, p < 0.05 for Mn, F = 5.24, p < for Fe, F = 29.08, p < for Ni, F = 12.24, p < 0.05 for Cr). 11

12 4. Leachability of heavy metals during composting process The TCLP extraction is an acetic acid digestion at ph of 4.93 to dissolve carbonates and few soluble oxides of organic matter and as a result these fractions of metals from organic matter along with the soluble and exchangeable fractions (Nair et al., 2008). The threshold limits for heavy metals contamination was given by US EPA in mg/kg are as follow: Cd-20, Cr-100 and Pb-100 (USEPA, 1992). However in the present study these metal concentrations (mg/kg) were in the range of , and for Cd, Cr and Pb respectively. The TCLP concentration of metals were reduced in the ranges: % for Zn, % for Cu, % for Mn, % for Fe, % for Ni, % for Pb, % for Cd and % for Cr in control and all zeolite treatments (Figure 7). Figure 7: Variation of TCLP extractable Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr during the composting process (bars denoted as ± standard deviation) The TCLP concentration of Mn, Fe, Ni, Cd and Cr were reduced significantly in all zeolite treatments in comparison to the control. The higher reduction in TCLP concentration of Zn was observed in zeolite 1 followed by zeolite 2, control and zeolite 3 treatments. The higher reduction in TCLP concentration of Cu and Pb were observed in zeolite 1 followed by control, zeolite 2 and 3 treatments during the composting process. The TCLP concentrations of the selected metals were completely in compliance with the EPA regulatory thresholds. Moirou et al. (2001) studied stabilization of Pb, Zn, and Cd-contaminated soils by natural zeolite, and reported that TCLP extractability of metals reduced moderately about 38% for Pb, 33% for Zn and 32% for Cd. However in the present study reduction of these metals was observed 12

13 about 53% for Pb, 61.4% for Zn and 82.8% for Cd at the end of composting process. The reduction could be attributed as the higher degradation of organic matter due to zeolite addition resulting formation of humic substances, which had a capacity to complex with metals, resulting formation of insoluble organometallic complexes (Wong and Fang, 2000; Villasenor et al., 2011). The initial ph values were enhanced slightly by zeolite addition, which reduced the solubility of heavy metals, consequentially reduction in TCLP extractability of heavy metals (Singh and Kalamdhad, 2013c). The variation in leachable Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr concentrations in control and zeolite treatments were significant (F = 5.45, p < for Zn, F = 9.50, p < for Cu, F = 5.56, p < for Mn, F = 7.97, p < for Fe, F = 39.89, p < for Ni, F = 7.33, p < for Pb, F = 19.4, p < for Cd, F = 3.45, p = for Cr). 5. Conclusion Addition of the natural zeolite (clinoptilolite) during water hyacinth composting process led to the increased Na, Ca and K concentration, and reduced significantly water solubility, DTPA and TCLP extractability of heavy metals. TCLP test proved that the all selected heavy metals concentrations in control and zeolite treated compost were below the threshold limits. The maximum reduction of bioavailability and leachability of heavy metals were observed in zeolite 1 and 2 treatments, which indicated optimum percentage of zeolite could enhance organic matter degradation; therefore it decreased the toxicity of the heavy metals during water hyacinth composting with cattle manure and sawdust. Acknowledgement The authors gratefully acknowledge the financial support of the Department of Science and Technology (DST), Government of India. 6. References 1. Bragato, G., Leita, L., Figliolia, A. and Nobili M., (1998), Effects of sewage sludge pretreatment on microbial biomass and bioavailability of heavy metals. Soil and Tillage Research, 46, pp Cai, Q.Y., Mo, C., Wu, Q.T., Zeng, Q.Y. and Katsoyiannis, A., (2007), Concentration and speciation of heavy metals in six different sewage sludge-composts. Journal of Hazardous Materials, 147, pp Chiang, K.Y., Huang, H.J. and Chang, C.N., (2007), Enhancement of heavy metal stabilization by different amendments during sewage sludge composting process. Journal Environmental Engineering and Management, 17 (4), pp Erdem, E., Karapinar, N. and Donat, R., (2004), The removal of heavy metal cations by natural zeolites. Journal of Colloidal Inteface Science, 280, pp Fang, M. and Wong, J.W.C., (1999), Effects of lime amendment on availability of heavy metals and maturation in sewage sludge composting. Environmental Pollution, 106, pp

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