RESEARCH ARTICLE

Effect of lime on speciation of heavy metals duringcomposting of water hyacinth

Jiwan SINGH (✉), Ajay S. KALAMDHAD

Department of Civil Engineering, Indian Institute of Technology Guwahati (IITG), Guwahati-781039 Assam, India

© Higher Education Press and Springer-Verlag Berlin Heidelberg 2014

Abstract Composting is attractive and inexpensivemethod for treatment and biomass disposal of waterhyacinth. However, the major disadvantage of waterhyacinth composting is the high content of heavy metalsin the final compost. Addition of lime sludge significantlyreduced most bioavailable fractions (exchangeable andcarbonate) of heavy metals. Studies were carried oncomposting of water hyacinth (Eichhornia crassipes)with cattle manure and sawdust (6:3:1 ratio) and effectsof addition of lime (1%, 2% and 3%) on heavy metalspeciation were evaluated during 30 days of compostingperiod. The Tessier sequential extraction method wasemployed to investigate the changes in speciation of heavymetals such as Zinc (Zn), Copper (Cu), Manganese (Mn),Iron (Fe), Lead (Pb), Nickel (Ni), Cadmium (Cd) andChromium (Cr) during water hyacinth composting. Effectsof physicochemical parameters such as temperature, pHand organic matter on speciation of heavy metals were alsostudied during the process. Results showed that, the totalmetal content was increased during the compostingprocess. The higher reduction in bioavailability factor(BF) of Cu, Fe, Ni, Cd and Cr was observed in lime 2treatment about 62.1%, 64.4%, 71.9%, 62.1% and 58.9%respectively; however higher reduction in BF of Zn and Pbwas observed in lime 1 treatment during the compostingprocess. Reducible and oxidizable fractions of Ni, Pb andCd were not observed during the process. Addition of limewas very effective for reduction of bioavailability of heavymetals during composting of water hyacinth with cattlemanure and sawdust.

Keywords composting, lime, heavy metals, bioavailabil-ity factor, speciation

1 Introduction

Water hyacinth is a free floating aquatic plant. It has beenwidely used in constructed wetland and phytoremediationbecause of its fast growth rate and large uptake ofcontaminants such as heavy metals from the water bodies[1,2]. The land application of water hyacinth compost as asoil conditioner is most inexpensive technique for thetreatment and final disposal of water hyacinth because itcombines material recycling and biomass disposal at thesame time [3]. Unfortunately, the presence of high contentsof heavy metals often hampers agricultural land applica-tion of the composted water hyacinth. Uptake of heavymetals by plants and subsequent accumulation along thefood chain is a potential threat to animal and human health[4,5]. Some heavy metals such as Cu, Fe, Mn, Ni and Znare essential elements required for normal growth andmetabolism of plants [6], but these metals can easily lead topoisoning when their large fractions are present inexchangeable and carbonate forms. These forms are mostbioavailable factions for the plants [4]. The Cr, Pb and Cdare not essential for plants, thus even very less quantity ofthese metals is toxic for plants and humans.The total metal concentration is useful as an overall

pollution indicator, but it does not provide usefulinformation about their chemical form. Sequential extrac-tion of heavy metals in the compost is a useful techniquefor determining the chemical speciation [7]. Evaluation ofthe chemical speciation of heavy metals during compostingprocess facilitates to assess their appropriateness for landapplication. Speciation of heavy metals involve thefractionation of its total content into exchangeable,carbonate bound, reducible (Fe–Mn oxides bound),oxidizable (organic bound) and residual forms. Theexchangeable and carbonate bound fractions are mobilefractions and easily bioavailable. The oxidizable andreducible forms will be leached out only under extremeconditions while the residual fraction is almost inert [4].

Received March 24, 2014; accepted April 1, 2014

E-mail: jiwansingh95@gmail.com

Front. Environ. Sci. Eng.DOI 10.1007/s11783-014-0704-7

The method developed by Tessier et al. [8] is the onewidely used for this purpose.Many researchers have carried out work on the

improvement of the composting process to diminish thebioavailability of heavy metals to the plants using variousalkaline materials such as lime, coal fly ash etc [4,9–11].Liming, as a general means for raising soil pH, could alsominimize uptake of metals by plants in acid soils [12]. InIndia, about 0.75 million tones lime sludge generated peryear during acetylene gas production and expected toincrease annually due to very limited utilization of thislime sludge [13]. Therefore, the present study focused onthe utilization of waste lime for immobilization of mostavailable fractions (exchangeable and carbonate bound) ofheavy metal during water hyacinth composting. Avery fewliteratures are available on speciation of heavy metalsduring water hyacinth composting [3]. Although someauthors studied speciation of heavy metals during sewagesludge composting with lime [4,11] but there is noliterature available on speciation of heavy metals duringwater hyacinth composting mixed with lime. Hence, theaim of current study was at evaluating the effect of lime onspeciation of Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr during thecomposting of water hyacinth process.

2 Materials and methods

2.1 Feedstock materials

Water hyacinth, cattle manure (cow dung) and sawdustwere used for preparation of different waste mixtures.Water hyacinth was collected from the Amingoanindustrial area near Indian Institute of TechnologyGuwahati (IITG) campus, Assam, Indian. Cattle manurewas obtained from dairy farm near the campus. Sawdustwas purchased from nearby saw mill. Lime was collectedfrom Assam Air Products Pvt. Ltd., Guwahti, Assam-India. Waste lime is produced during acetylene gasproduction by calcium carbide in semisolid condition,expressed in Eq. (1) [14].

CaC2 þ 2H2O↕ ↓C2H2 þ Ca OHð Þ2Calcium  carbideð Þ Acetylene  gasð Þ Lime  sludgeð Þ (1)

Collected lime sludge contains about 60-70% moisturecontent and it was not in uniform size. Therefore, it wasdried in oven and ground to make powder form. Cattlemanure and sawdust were mixed manually, and thenpowder form of lime was mixed with the mixture of cattlemanure and sawdust. Shredded water hyacinth (about 1cm) was mixed with mixture of cattle manure, sawdust andlime. Sawdust was used as bulking agent and for makingcomposting materials as free flow, resulting proper aerationduring composting process. Singh and Kalamdhad [3]suggested that mixture of 90 kg water hyacinth, 45 kg

cattle manure and 15 kg sawdust was best combination forreduction of bioavailability of heavy metals during waterhyacinth composting, therefore in this study samecombination was used with 0, 1%, 2%and 3% lime. Priorto composting, the maximum particle size of the wastemixture was restricted to 1 cm in order to provide betteraeration and moisture control. The waste compositions ofdifferent treatments are given as follow: control (waterhyacinth 90 kg + cattle manure 45 kg + sawdust 15 kg),lime 1 treatment (control + 1% lime), lime 2 treatment(control + 2% lime) and lime 3 treatment (control + 3%lime). Initial characterizations of lime are given as follows:pH-12.5 � 0.06, electrical conductivity (EC) (dS$m–1)-8.5� 0.13, moisture content (%)-55 � 0.32, volatile solids(%)-0.62 � 0.22, nutrients in mg/kg (Sodium-1.4 � 0.05,Potassium-1.2 � 0.03, Calcium-65650 � 350 andMagnisium-4.7 � 1.27), and heavy metals in mg$kg–1

(Zn-2.14 � 0.43, Cu-0.66 � 0.02, Mn-7.23 � 0.23, Fe-3.0� 0.06, and Ni-0.2 � 0.007).

2.2 Agitated pile composting

Four different waste combinations were formed intotrapezoidal piles (length 2100 mm, base width 350 mm,top width 100 mm and height 550 mm, having length tobase width (LW–1) ratio of 6). Composting period of total30 days was decided for agitated pile composting [3].Agitated piles contained approximately 150 kg of differentwaste combinations and it was manually turned at everythird day during 30 days of composting period. Thesamples were collected from the piles after turning at 0,6th, 12th, 18th, 24th and 30th day. Samples were dried at105°C in oven for 24 h and moisture content wascalculated, dried samples were ground to pass to 0.22mm sieves and stored for further analysis.

2.3 Experimental analysis

A digital thermometer was used for temperature monitor-ing throughout the composting period. Prepared Sampleswere analyzed for the following parameters: pH (1:10 w/vwaste: water extract), moisture content and total organiccarbon (TOC) [15]. The atomic absorption spectrometer(AAS) (Varian Spectra 55B) was used for analysis of Zn,Cu, Mn, Fe, Ni, Pb, Cd and Cr concentration afterdigestion of 0.2 g sample with 10 mL mixture of H2SO4

and HClO4 (5:1) in block digestion system (PelicanEquipments Chennai-India) for 2 h at 300°C.Sequential extraction method developed by Tessier et al.

[8] for heavy metal speciation was followed, according tothis method metal bound with five fractions: exchangeable(F1), carbonate (F2), reducible (F3), oxidizable (F4) andresidual (F5) fraction. The detail methodology of sequen-tial extraction was followed as Singh and Kalamdhad [3].The sum of total concentration of F1, F2, F3 and F4 for oneheavy metal represents its total concentration of mobile

2 Front. Environ. Sci. Eng.

fractions (FA) in mg$kg–1 (dry matter). Furthermore, FT isdefined as the sum of FA and F5 fractions of the heavymetal, in mg$kg–1 (dry matter); the bioavailability factors(BF) of one heavy metal define as the ratio of FA to FT.All the results reported are the means of three replicates.

Repeated measures treated with analysis of variance(ANOVA) was made using Statistica software. Theobjective of the statistical analysis was to determine theany significant differences among the parameters analyzedfor different proportion.

3 Results and discussion

3.1 Physico-chemical analysis

Figure 1 shows the variation of temperature in control andlime added composting process. The reaction temperatureduring composting process was increased rapidly up to thethermophilic phase (about 57°C) as a result of the intensemicrobial activity. Longer thermophilic stage wasobserved with lime added composting process in compar-ison to control. Very quick development of thermophilicstage was observed in lime 2 treatment. Subsequently, thetemperature decreased significantly after attending thermo-philic stage. Addition of lime neutralizes the releaseorganic acids during the process and provides anappropriate amount of Ca, which would improve themetabolic activity during composting process [9]. The

moisture content of the compost was reduced significantly(F = 115.3, p < 0.05) from 83.9% to 37.6%, 86.8% to43.2%, 83.8% to 40.2% and 82.4% to 38.3% in control,lime 1, lime 2 and lime 3 trearment respectively duringcomposting process (Fig. 1). Lower reduction of moisturewas observed in lime amended compost in comparison tocontrol due to its better moisture holding capacityconsequently provide optimum condition for microbialgrowth [10]. Due to addition of lime, initial pH of thecompost mixtures was higher than control compostmixture but it decreased gradually thereafter to nearlyneutral. Initially maximum pH values were observed about6.4, 7.6, 8.8 and 10.4 in control, limes 1, 2 and 3 treatmentsrespectively, however in the final compost pH values werein the range of 7.3–7.7 (Fig. 1). Similar trends of pHchange were also observed by other researchers [4,9]. ThepH strongly influences the solution chemistry of heavymetals: hydrolysis, complexation by organic and or/inorganic ligands, redox reaction, precipitation, thespeciation and biosorption availability of the heavy metals[16]. The variation in pH in control and lime amendedcompost was significant (F = 28.1, p < 0.001). Figure 1demonstrates that the TOC was reduced significantly (F =50, p < 0.05) from 43.5% to 33.5%, 37.7% to 24.43%,36.9% to 22.73% and 39.8% to 26% in control, limes 1, 2,and 3 respectively. Higher reduction of TOC was observedin lime 2 treatment might be due to loss of carbon in theform of carbon dioxide as a metabolic end product [3,17].The percent decrease in TOC content was in the order of

Fig. 1 Variation of temperature, moisture content, pH, and total organic carbon during composting process

Jiwan SINGH et al. Effect of lime on speciation of heavy metals during composting of water hyacinth 3

lime 2> lime 1> lime 3> control. The pH, TOC andbioavailability of heavy metal are critical factors for theheavy metal accumulation by both plants and animals [18].

3.2 Concentration and speciation of heavy metals

Figure 2 illustrates the variation in total concentration ofmetals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) in control andlime added compost during 30 days of composting period.Total metal contents increased with the composting perioddue to the reduction of the compost mass. The similarresults were also reported by Wong and Selvam [4] duringsewage sludge composting with lime. The variation in Zn,Cu, Mn, Fe, Ni, Pb, Cd and Cr concentrations in controland lime amended compost were significant (F = 34.8, p< 0.001 for Zn, F = 179.02, p < 0.05 for Cu, F = 21.94, p< 0.001 for Mn, F = 9.14, p < 0.001 for Fe, F = 30.13, p< 0.001 for Ni, F = 45.24, p < 0.05 for Pb, F = 27.5, p <0.001 for Cd, F = 8.46, p < 0.001 for Cr). The present

study reveals that the toxicity of heavy metals does notrelated to its total concentration in water hyacinth compost,but it depends on different forms in which these metals arepresent.

3.2.1 Speciation of Zn, Cu, Mn, Fe and Ni

Speciation of Zn, Cu, Mn, Fe and Ni in control is given inFig. 3 and speciation of these metals in limes 1, 2, and 3treatments are given in Tables 1 and 2. The F1, F2, F3 andF4 fractions of Zn were reduced in the control and limeamended compost. Higher reduction of F1 (69.7%) and F3(36.5%) fractions was observed in control but higherreduction of F2 (61.3%) and F4 (60.2%) fractions wasobserved in lime 1 treatment. The F5 fraction of Zn wasenhanced in control and lime amended compost. The orderof different fractions of Zn in the final compost of controlwas: F5> F4> F3> F2> F1, but in the lime amendedcompost order was: F5> F3> F4> F2> F1. In the lime

Fig. 2 Variation of total heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) concentration during the composting process

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amended compost F4 fraction was transformed into F3 andF5 fractions. The Zn was mainly present in residualfraction in the control and lime amended compost buthigher percentage was found in lime amended compost.These results confirm that mobile fractions of Zn wereconverted into stable fraction due to lime addition. Wongand Selvam [4] also observed that the Zn was found in the

residual fraction in the lime amended sewage sludgecompost. The reduction of F1, F2, F3 and F4 fractions incontrol and all lime treatments might be due to cationexchange and complexation by organic ligands and theformation of Zn complex with humic substances formed atthe end of composting process. Humic substances containvarious organic functional groups that can adsorb metal

Table 1 Speciation of heavy metals in lime 1 treatment during 30 days of composting period

Days Zn (mg$kg–1 dry matter) Cu (mg$kg–1 dry matter)

F1 F2 F3 F 4 F5 F1 F2 F3 F 4 F5

0 5.19�0.013 6.41�0.41 26.30�0.7 31.0�0.47 44.0�0.68 4.68�0.03 1.88�0.03 0.90�0.10 20.65�4.5 21.65�5.7

30 3.88�0.025 4.50�3.4 40.30�3.4 23.33�0.58 136.45�2.25 2.60�0.10 1.40�0.10 0.80�0.20 15.38�0.02 66.85�15.9

Days Mn (mg$kg–1 dry matter) Fe (mg$kg–1 dry matter)

F1 F2 F3 F 4 F5 F1 F2 F3 F 4 F5

0 36.1�0.68 106.3�0.7 86.9�2.4 78.7�0.39 50.5�4.05 27.7�0.7 21.7�0.7 2789.5�3.5 6260.9�141 1671.0�139

30 30.0�0.38 93.4�0.03 244.2�0.9 45.4�0.30 194.1�4.6 16.3�0.7 9.6�0.4 2123.0�3.0 3725.0�20 8785.0�475

Days Ni (mg$kg–1dry matter) Pb (mg$kg–1 dry matter)

F1 F2 F3 F 4 F5 F1 F2 F3 F 4 F5

0 2.98�0.03 3.25�0.05 ND ND 166.9�6.4 22.9�2.9 9.9�0.4 ND ND 708�2

30 1.43�0.03 2.18�0.08 ND ND 228.9�50.4 11.2�0.7 6.7�0.3 ND ND 1016�21

Days Cd (mg$kg–1dry matter) Cr (mg$kg–1 dry matter)

F1 F2 F3 F 4 F5 F1 F2 F3 F 4 F5

0 0.73�0.03 0.84�0.01 ND ND 45.9�0.4 5.45�0.15 1.33�0.03 1.55�0.05 15.85�0.45 115.8�0.25

30 0.46�0.01 0.58�0.02 ND ND 64.9�4.4 3.65�0.15 1.05�0.05 1.45�0.2 8.85�0.45 160.5�5.95

Note: Mean value followed by different letters in columns is statistically different (ANOVA; P< 0.05); ND- not detected

Table 2 Speciation of heavy metals in lime 2 and 3 treatments during 30 days of composting period

heavy metals(mg$kg–1 drymatter)

days lime 2 lime 3

F1 F2 F3 F 4 F5 F1 F2 F3 F 4 F5

Zn 0 7.61�0.49 7.56�1.06 42.07�0.47 24.66�0.64 40.28�0.28 4.46�1.05 3.83�0.48 36.26�0.66 19.28�0.04 59.1�0.04

30 3.02�0.02 4.11�0.51 54.55�0.75 21.62�0.22 109.0�3.0 2.73�0.06 2.48�0.03 42.39�0.02 16.33�0.53 105.4�0.53

Cu 0 6.26�0.05 3.65�0.05 0.65�0.05 15.69�0.5 23.0�0.07 2.82�0.07 2.17�0.07 0.65�0.15 13.48�0.02 24.65�0.7

30 1.99�0.01 1.14�0.07 0.88�0.20 12.41�0.8 64.8�0.04 2.02�0.04 1.67�0.04 1.25�0.05 13.97�0.08 84.57�2.1

Mn 0 13.0�0.2 126.2�0.9 194.2�2.1 58.7�0.6 36.5�5.5 9.4�0.2 92.0�0.5 280.1�6.0 49.2�1.1 56.8�3.8

30 33.2�0.8 97.7�0.7 285.1�2.9 43.1�0.4 189.0�6 22.1�0.27 72.0�3.0 251.7�1.7 33.9�0.8 202.0�48

Fe 0 27.4�0.3 26.9�1.3 2788�20 4477�21 1655�445 21.9�3.3 21.6�0.5 2061.0�2 3569.5�5.5 6791�259

30 13.1�0.5 11.9�0.7 1929�4.5 3741�3.8 13925�625 14.1�0.4 11.1�0.5 1819.5�23 2426.4�1.4 18101�101

Ni 0 2.58�0.03 3.25�0.7 ND ND 210.8�50.8 4.09�0.04 3.48�0.22 ND ND 193�1.3

30 1.15�0.2 1.20�0.06 ND ND 337.8�12.3 3.36�0.05 2.40�0.05 ND ND 300�21.5

Pb 0 24.9�0.4 10.8�1.4 ND ND 803�3 20.6�1.1 12.7�0.4 ND ND 737.5�7.5

30 16.0�0.6 7.5�0.03 ND ND 1153�8 12.9�0.2 8.9�0.2 ND ND 1004.5�10.5

Cd 0 0.94�0.02 1.25�0.25 ND ND 40.85�0.7 0.93�0.03 0.98�0.03 ND ND 44.9�4.6

30 0.48�0.03 0.79�0.07 ND ND 64.8�0.8 0.48�0.03 0.76�0.06 ND ND 66.2�2.4

Cr 0 3.75�0.05 2.29�0.47 1.75�0.05 11.0�2.0 97.9�0.4 4.08�0.13 1.53�0.03 1.50�0.1 7.40�0.05 127.8�0.3

30 1.80�0.05 1.18�0.03 1.15�0.05 7.0�0.20 157.5�26.5 3.15�0.05 1.57�0.04 1.15�0.05 6.07�0.03 164.3�18.3

Mean value followed by different letters in columns is statistically different (ANOVA; P < 0.05); ND- not detected

Jiwan SINGH et al. Effect of lime on speciation of heavy metals during composting of water hyacinth 5

ions through ionic force [19,20]. Furthermore, reduction ofbioavailable fractions were reduced might be due toprecipitation of Zn with hydroxides, carbonates, phos-phates, sulfides and several other anions [19].The BF of Zn was decreased from 0.75 to 0.48, 0.61 to

0.35, 0.67 to 0.43 and 0.52 to 0.38 in control and limes 1, 2and 3 treatments respectively (Fig. 4). The higherreduction of BF was observed in lime 1 treatment(43.4%) followed by lime 2 treatment (35.1%), control(33.7%) and lime 3 treatment (27.3%) during thecomposting process. The variation in F1, F2, F3, F4 andF5 fractions of Zn in control and all lime treatments weresignificant (F = 28.89, p < 0.001 for F1, F = 47.78, p <0.001 for F2, F = 139.77, p < 0.05 for F3, F = 73.23, p <0.05 for F4, F = 17.76, p < 0.001 for F5).The F1, F2, F3 and F4 fractions of Cu were reduced in

the control and lime amended compost. Higher reductionof F1 (77%) and F3 (75%) fractions (percentage of totalfraction) was observed in control but higher reduction of

F2 (80.5%) and F4 (58.6%) fractions was observed inlimes 2 and 1 treatment, respectively. The F5 fraction of Cuwas enhanced in control and lime amended compost. TheBF of Cu was decreased from 0.63 to 0.28, 0.57 to 0.23,0.53 to 0.20 and 0.44 to 0.18 in control and limes 1, 2 and 3treatments respectively (Fig. 4). The higher reduction ofBF was observed in lime 2 treatment (62.1%) followed bylime 1(59%), lime 3 (58.2%) and control (55.5%) duringthe composting process. The higher reduction in BF of Cuwas observed in lime added compost which could beexplained as, the conversion of easily available fractionsinto residual fraction and formation of Cu ion complexwith two or more organic functional groups mainlycarboxylic, carbonyl and phenolic, so that the ion isimmobilized in a rigid inner-sphere complex [21]. Thecomplex formation of Cu with humic substances generallyhigher than Zn due to water solubility of humic substances,which have a high content of carboxyl groups, and thestability constant humic complexes depend on the nature of

Fig. 3 Speciation of heavy metals in control during the composting process

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organics, ion strength and pH in environment [22]. Thegroups of –OH and –COOH supplied by cattle manureincreased the binding sites and combined with Cu to forminsoluble and immobile complexes, thus the concentrationof most bioavailable fractions (F1 and F2 fractions) of Cudecreased and the potential environmental risk wasdrastically reduced [16]. Furthermore, the decrease of F1and F2 fractions of Cu in agreement with increase of humicsubstances formed during composting process [16]. Thevariation in F1, F2, F3, F4 and F5 fractions of Cu in controland all lime treatments were significant (F = 104.94, p <0.05 for F1, F = 36.22, p < 0.001 for F2, F = 11.84, p <0.001 for F3, F = 59.69, p < 0.001 for F4, F = 83.25, p <0.05 for F5).The F1 fraction of Mn was reduced about 63.8 and

50.9% of total fraction in control and lime 1 treatmentrespectively; however this fraction was increased in lime 2and 3 treatments. The F2 and F4 fractions of Mn werereduced in all lime treatments; however these fractionswere increased in the control. The F3 fraction of Mn wasreduced about 38.1, 2.9 and 36.1% of total fraction incontrol, lime 2 and 3 treatments respectively. The F5

fraction of Mn was increased in the control and all limetreatments during the composting process. The F2 and F4fractions of Mn decreased in all lime treated compost;however these fractions were increased in control. Wongand Selvam [4] reported that initially Mn was dominatedby the F5 fraction but when the composting progressed, theF3 fraction increased and became the largest fraction.However in the present study F3 fraction was predomi-nated throughout the composting process. The BF of Mnwas decreased from 0.65 to 0.47, 0.86 to 0.68, 0.91 to 0.71and 0.88 to 0.65 in control and limes 1, 2 and 3 treatmentsrespectively (Fig. 4). The higher reduction of BF wasobserved in control (27.2%) followed by lime 3 treatment(26%), lime 2 treatment (22.6%) and lime 1 treatment(20.8%) during the composting process. The oxidationprocess and the formation of organo-metallic complexesduring composting could reduce the BF of Mn [9]. Limeaddition increases the pH, resulting decrease in bioavail-ability of Mn by precipitate formation [3]. The variation inF1, F2, F3, F4 and F5 fractions of Mn in control and alllime treatments were significant (F = 90.71, p < 0.05 forF1, F = 437, p < 0.05 for F2, F = 38.27, p < 0.001 for F3,

Fig. 4 Changes in bioavailability factor (BF) of heavy metals in control and lime treated composting process

Jiwan SINGH et al. Effect of lime on speciation of heavy metals during composting of water hyacinth 7

F = 205.1, p < 0.05 for F4, F = 74.34, p < 0.001 for F5).The F1, F2, F3 and F4 fractions of Fe were reduced in

the control and lime treatments during the compostingprocess. Higher reduction of F1 and F2 fractions wasobserved about 75 and 84% of the total fractionrespectively in lime1 treatment. Higher reduction of F3and F4 fractions was observed about 68.1 and 64.5% of thetotal fraction respectively in lime 1 treatment. The F5fraction of Fe was enhanced in control and lime amendedcompost. An extremely significant decrease in F1 fractionwas observed in all lime treatments, which suggest thataddition of lime could prevent the mobility of Fe. The BFof Fe was decreased from 0.82 to 0.67, 0.85 to 0.40, 0.82 to0.29 and 0.46 to 0.19 in the control and lime 1, 2 and 3treatments respectively. The higher reduction of BF wasobserved in lime 2 treatment (64.4%) followed by lime 3(58.1%), lime 1 (52.6%) and control (18.8%) during thecomposting process (Fig. 4). It has been observed thathigher reduction in BF of Fe was observed in limetreatments as compared to control could be due to humicsubstances formed a complex compound with Fe [3]. Thevariation in F1, F2, F3, F4 and F5 fractions of Fe in controland all lime treatments were significant (F = 41.73, p <0.001 for F1, F = 186, p < 0.05 for F2, F = 1988, p <0.05 for F3, F = 1199.9, p < 0.05 for F4, F = 37, p <0.001 for F5).The F1 and F2 fractions of Ni were reduced in the

control and lime treatments but the higher reduction ofthese fractions was observed about 69% and 63% of thetotal fraction in lime 2 treatment respectively. The F5fraction of Ni was enhanced in control and lime treatmentduring the composting process. The F1 fractions contributeabout 5% of the total fraction in final compost of control;however this fraction contribute < 1.5% of total fractionin lime treated compost. The F2 fractions contribute about1.5% of the total fraction in final compost of control,however this fraction contribute < 1% of the total fractionin lime treated compost. Wong and Selvam [4] reportedthat both F1 and F2 fractions contribute about 2% of thetotal Ni content. The F5 fraction of Ni was about 92% oftotal fraction in the final compost of control as compared to98% in the lime treated compost. The BF of Ni wasdecreased from 0.12 to 0.064, 0.04 to 0.016, 0.027 to 0.007and 0.038 to 0.02 in control and lime 1, 2 and 3 treatmentsrespectively (Fig. 4). The highest reduction of BF wasobserved in lime 2 treatment (71.9%) followed by lime 1(56.9%), control (52.6%) and lime 3(46.6%) during thecomposting process. A significant decrease in BF wasobserved in lime 2 treatment, which suggested that theaddition of lime could prevent the bioavailability of Niduring the process. The significant decreases in BF of Nimight be due to alkaline stabilization process [3]. Asignificant decrease of BF in lime 2 treatment confirmedthat the addition of lime and cattle manure in anappropriate proportion could effectively prevent theavailability of Ni for plant uptake [3]. Su and Wong [23]

reported that the F5 fraction contributes 52% of the total Nicontent; followed by F3 fraction in sewage sludge;whereas, in present study F5 fraction contributed about90% – 98%. The variations in F1, F2 and F5 fractions of Niin control and all lime treatments were significant (F =18.78, p < 0.001 for F1, F = 15, p < 0.001 for F2, F =9.6, p < 0.001 for F5).

3.2.2 Speciation of Pb, Cd and Cr

Speciation of Pb, Cd and Cr in control is given in Fig. 3and speciation of these metals in lime 1, 2, and 3 treatmentsare given in Tables 1 and 2. The F1 and F2 fractions of Pbwere reduced in the control and lime treated compost butthe higher reduction of these fractions was observed about55.2 and 56.8% respectively in control. Wong and Selvam[4] reported that there is no marked difference in F1 and F2fractions from initial to final composting process. The F5fraction of Pb was increased in all lime treatments;however this fraction was reduced in control about 2.5%of total fraction during the composting process. The BF ofPb was decreased from 0.056 to 0.025, 0.044 to 0.017,0.042 to 0.020 and 0.043 to 0.021 in control and lime 1, 2and 3 treatments respectively (Fig. 4). The higherreduction of BF was observed in lime 1 treatment(61.0%) followed by control (55.6%), lime 2 (51%) andlime 3 (48.7%) during the composting process. Thedecrease in Pb mobility during sewage sludge compostingwas also observed by Qiao and Ho [21]. Development ofslightly alkaline medium by lime addition can reducemobility of Pb by forming Pb-organic matter complex, buthigher alkaline conditions can have a reverse effect on Pbstability due to the amphoteric nature of Pb [19]. Thevariations in F1, F2 and F5 fractions of Pb in control andall lime treatments were significant (F = 29.94, p < 0.001for F1, F = 13.25, p < 0.001 for F2, F = 58.76, p < 0.001for F5).The F1 and F2 fractions of Cd were reduced in the

control and lime treatments. The higher reduction of thesefractions was observed about 66.6% and 58.8% of totalfraction respectively in lime 2 treatment during thecomposting process. The F1 and F2 fractions were reducedand F5 fraction was increased might be due to formation ofstrong chemical bond between Cd and degraded organicmatter [24]. A similar observation was also reported duringcomposting of sewage sludge by Hanc et al. [25], the F5fraction of Cd was enhanced in all lime treatments;however, this fraction was reduced in control (about 1.3%of total fraction) during the composting process. The BF ofCd was decreased from 0.060 to 0.053, 0.033 to 0.016,0.051 to 0.019 and 0.041 to 0.018 in control and limes 1, 2and 3 treatments respectively (Fig. 4). The higherreduction of BF was observed in lime 2 treatment(62.1%) followed by lime 3 (51.3%), lime 1 (48.5%) andcontrol (10.5%) during the composting process. Thedecrease in BF of Cd might be due to maintaining neutral

8 Front. Environ. Sci. Eng.

pH (7 to 7.6) in lime treatments throughout the compostingprocess. An enormously significant decrease in BF of Cdwas observed in all lime treatments, which suggest that theaddition of lime could prevent the mobility of Cd.Furthermore, Cd was directly bound with two or moreorganic functional groups mainly carboxylic, carbonyl andphenolic, so that it immobilized in a rigid inner-spherecomplex [26]. Lime amendment was proficient in reducingbioavailability of Cd during water hyacinth compostingdue to formation of less soluble carbonate salts andformation metal of hydroxide. Metal hydroxide might beadsorbed on charged colloids such as degraded organicmatter, which consequently reduced the metal solubility[27]. The variations in F1, F2 and F5 fractions of Cd incontrol and all lime treatments were significant (F = 70.5,p < 0.05 for F1, F = 13.55, p < 0.001 for F2, F = 8.73, p< 0.001 for F5).The F1, F2, F3 and F4 fractions of Cr were reduced in

the control and lime treatments. Higher reduction of F1, F2and F3 fractions was observed about 67.9%, 65.7% and54.6% of the total fraction in lime 2 treatment; however,the maximum reduction of F4 fraction was observed about42.2% of total fraction in control during the compostingprocess. The F5 fraction of Cr was enhanced in control andlime amended compost. The BF of Cr was decreased from0.29 to 0.18, 0.17 to 0.09, 0.16 to 0.07 and 0.10 to 0.07 incontrol and lime 1, 2 and 3 treatments respectively (Fig. 4).The higher reduction of BF was observed in lime 2treatment (58.9%) followed by lime 1 treatment (50.5%),control (36.3%) and lime 3 treatment (33.5%) during thecomposting process. Significant reduction in BF wasobserved in all lime treatments in comparison to control. Itcould be explained that F1 and F2 fractions may boundwith various organic functional groups present in thehumic substances, while F3 and F4 fractions might beconverted into F5 fraction during the process. Furthermore,the maximum reduction of BF was observed in lime 2treatment might be due to addition of appropriateproportion of lime and cattle manure, reduced the Crbioavailability during the process. The F5 fraction of Crwas dominant throughout composting process. Smith [28]also reported that Cr was mainly present in F5 fraction. Thevariation in F1, F2, F3, F4 and F5 fractions of Cr in controland all lime treatments were significant (F = 29.29, p <0.001 for F1, F = 56.64, p < 0.05 for F2, F = 20.36, p <0.001 for F3, F = 16.20, p < 0.001 for F4, F = 12.66, p <0.001 for F5).

4 Conclusions

Speciation of heavy metals during composting process wasaffected by lime addition due to change in physico-chemical properties of the compost such as organic matterdecomposition and pH. The bioavailability factor (BF) ofZn, Cu, Fe, Ni, Pb, Cd and Cr was reduced extremely

significant in lime treatments in comparison to control.This study suggests that the addition of lime could notprevent the bioavailability of Mn. Most of the selectedheavy metals were converted from mobile fractions(exchangeable, carbonate, reducible and oxidizable frac-tions) to most stable fraction (residual fraction) due to limeaddition. The order of BF of different metals in the waterhyacinth compost was: Mn (0.70)> Fe (0.67)> Zn (0.48)>Cu (0.28)> Cr (0.18)> Ni (0.06)> Cd (0.05)> Pb (0.03).The order of BF indicates that toxicity of metals does notdepend on its total metal concentration. The totalconcentration of Pb was higher than Zn, Cu, Mn, Ni, Cdand Cr but its BF was lowest among the all eight metals.The total concentration of Cu was much less than Pb andNi but its BF about was five times of Ni and ten times ofPb. The maximum reduction in BF of heavy metals wereobserved in lime 2 treatment, which indicated optimumpercentage of lime and cattle manure could enhanceorganic matter degradation and buffering against reductionin pH; resulting reduction in toxicity of the metals duringthe composting process. Therefore, this study concludedthat the application of lime sludge was successful forreducing bioavailability of heavy metals during waterhyacinth composting mixed with cattle manure andsawdust.

Acknowledgements This research was supported by the Department ofScience and Technology (DST), Government of India.

References

1. Malik A. Environmental challenge vis a vis opportunity: the case of

water hyacinth. Environment International, 2007, 33(1): 122–138

2. Rai P K. Heavy metal phytoremediation from aquatic ecosystems

with special reference to macrophytes. Critical Reviews in

Environmental Science and Technology, 2009, 39(9): 697–753

3. Singh J, Kalamdhad A S. Concentration and speciation of heavy

metals during water hyacinth composting. Bioresource Technology,

2012, 124: 169–179

4. Wong J W C, Selvam A. Speciation of heavy metals during co-

composting of sewage sludge with lime. Chemosphere, 2006, 63(6):

980–986

5. Iwegbue CMA, Emuh F N, Isirimah N O, Egun A C. Fractionation,

characterization and speciation of heavy metals in composts and

compost-amended soils. African Journal of Biotechnology, 2007, 6

(2): 67–78

6. Singh J, Kalamdhad A S. Effects of heavy metals on soil, plants,

human health and aquatic life. International Journal of Research

Chemistry and Environment, 2011, 1(2): 15–21

7. Walter I, Martínez F, Cala V. Heavy metal speciation and phytotoxic

effects of three representative sewage sludges for agricultural uses.

Environmental Pollution, 2006, 139(3): 507–514

8. Tessier A, Campbell P G C, Bisson M. Sequential extraction

procedures for the speciation of particulate trace metals. Analytical

Chemistry, 1979, 51(7): 844–851

Jiwan SINGH et al. Effect of lime on speciation of heavy metals during composting of water hyacinth 9

9. Fang M, Wong J W C. Effects of lime amendment on availability of

heavy metals and maturation in sewage sludge composting.

Environmental Pollution, 1999, 106(1): 83–89

10. Chiang K Y, Huang H J, Chang C N. Enhancement of heavy metal

stabilization by different amendments during sewage sludge

composting process. Journal of Environmental Economics and

Management, 2007, 17(4): 249–256

11. Wang X, Chen L, Xia S, Zhao J. Changes of Cu, Zn, and Ni

chemical speciation in sewage sludge co-composted with sodium

sulfide and lime. Journal of Environmental Sciences (China), 2008,

20(2): 156–160

12. Wong J W C, Fang M. Effects of lime addition on sewage sludge

composting process. Water Research, 2000, 34(15): 3691–3698

13. Central Pollution Control Board (CPCB) India, Assessment of

utilization of industrial solid wastes in cement manufacturing, 2006

14. Carreiro L G, Burke A A, Dubois L. Co-generation of acetylene and

hydrogen for a carbide-based fuel system. Fuel Processing

Technology, 2010, 91(9): 1028–1032

15. Kalamdhad A S, Singh Y K, Ali M, Khwairakpam M, Kazmi A A.

Rotary drum composting of vegetable waste and tree leaves.

Bioresource Technology, 2009, 100(24): 6442–6450

16. Singh J, Kalamdhad A S. Bioavailability and leachability of heavy

metals during water hyacinth composting. Chemical Speciation and

Bioavailability, 2013a, 25(1): 1–14

17. Zheng G D, Gao D, Chen T B, Luo W. Stabilization of nickel and

chromium in sewage sludge during aerobic composting. Journal of

Hazardous Materials, 2007, 142(1–2): 216–221

18. Li L, Xu Z, Wu J, Tian G. Bioaccumulation of heavy metals in the

earthworm Eisenia fetida in relation to bioavailable metal

concentrations in pig manure. Bioresource Technology, 2010, 101

(10): 3430–3436

19. Kumpiene J, Lagerkvist A, Maurice C. Stabilization of As, Cr, Cu,

Pb and Zn in soil using amendments—a review. Waste Management

(New York), 2008, 28(1): 215–225

20. Cai Q Y, Mo C H, Wu Q T, Zeng Q Y, Katsoyiannis A.

Concentration and speciation of heavy metals in six different sewage

sludge-composts. Journal of Hazardous Materials, 2007, 147(3):

1063–1072

21. Qiao L, Ho G. The effects of clay amendment and composting on

metal speciation in digested sludge. Water Research, 1997, 31(5):

951–964

22. Liu S, Wang X, Lu L, Diao S, Zhang J. Competitive complexation of

copper and zinc by sequentially extracted humic substances from

manure compost. Agricultural Sciences in China, 2008, 7(10):

1253–1259

23. Su D C, Wong J W C. Chemical speciation and phytoavailability of

Zn, Cu, Ni and Cd in soil amended with fly ash-stabilized sewage

sludge. Environment International, 2004, 29(7): 895–900

24. Haroun M, Idris A, Syed Omar S R. A study of heavy metals and

their fate in the composting of tannery sludge. Waste Management

(New York), 2007, 27(11): 1541–1550

25. Hanc A, Tlustos P, Szakova J, Habart J. Changes in cadmium

mobility during composting and after soil application. Waste

Management (New York), 2009, 29(8): 2282–2288

26. Singh J, Kalamdhad A S. Effect of rotary drum on speciation of

heavy metals during water hyacinth composting. Environmental

Engineering Research, 2013b, 18(3): 177–189

27. Singh J, Kalamdhad A S. Effects of lime on bioavailability and

leachability of heavy metals during agitated pile composting of

water hyacinth. Bioresource Technology, 2013c, 138: 148–155

28. Smith S R. A critical review of the bioavailability and impacts

of heavy metals in municipal solid waste composts compared to

sewage sludge. Environment International, 2009, 35(1): 142–

156

10 Front. Environ. Sci. Eng.