Volume 13, Issue 4, 132442 (1-6)


International Journal of Recycling Organic Waste in Agriculture (IJROWA)


https://dx.doi.org/10.57647/ijrowa-3kgw-nr28


Vermicomposting: a technology for vermiremediation of heavy metals from sewage sludge and animal dung

Deepak Kumar Bhartiya1

, Gorakh Nath2
, Keshav Singh3,∗


1Department of Zoology, Government Degree College, Dhadha Bujurg, Hata, Kushinagar, U.P., India. 2Department of Zoology, S.V.M. Mahila, P.G. College, Gorakhpur, U.P., India.

3Vermibiotechnology Laboratory, Department of Zoology, D.D.U. Gorakhpur University, Gorakhpur, U.P., India.

∗Corresponding author: [email protected]


Original Research

Received:

12 Apr 2023

Revised:

11 Aug 2023

Accepted:

13 Dec 2023

Published online: 20 May 2024

© The Author(s) 2024

Abstract:

Purpose: The present study to investigate the earthworm Eisenia fetida was a chief organism for accumulation of heavy metals (Pb, Cr, and Cd) in their body tissue from sewage sludge with different combinations of animal dung and converted into rich organic vermicompost which plays a beneficial role for environment, animals and human health.

Method: Animal dung and sewage sludge were collected from Gorakhpur city and earthworm E. fetida an epigeic species collected from Vermibiotechnology Laboratory, Department of Zoology, D. D. U. Gorakhpur University, Gorakhpur. Analysis of heavy metals in different animal dung, sewage sludge, final vermicompost, and earthworm bodies were measured by Shimadzu AA- 7000 atomic absorption spectrometer.

Results: There was a significant (P < 0.05) reduction of Pb, Cr, and Cd concentration observed in different

animal dung such as cow, buffalo and goat dung with sewage sludge in ratios of 1:1, 1:2, and 1:3 before and after vermicomposting. Cr was significantly decreased in cow dung (CD) and goat dung (GD) and Cd in cow dung (CD) and cow dung with sewage sludge (CD+ SS, 1:1) the at BDL level whereas the concentration of Pb significantly decreased by 76.470% in the combination of GD+ SS (1:1). The Cr and Cd were significantly increased in the body of E. fetida 3.384% and 11.801%, respectively, in the combination of CD+ SS (1:3) whereas Pb significantly increase by 23.018% in the combination of BD+SS (1:3).

Conclusion: E. fetida is a suitable species for the accumulation of heavy metals such as Pb, Cr, and Cd in different vermibeds during vermicomposting and plays an important role in the remediation of heavy metals from animal dung with sewage sludge. Vermibiotechnology is a useful technique for the management of heavy metals.

Keywords: Vermiremediation; Eisenia fetida; Sewage sludge; Heavy metals; Vermicomposting



  1. ‌Introduction


    The production of sewage sludge is parallel to the increas- ing rate of population in India. It is a serious problem for society and it causes environmental hazards (Kaviraj and Sharma, 2003; Suthar, 2006; Yadav and Garg, 2011; Jatav et al., 2021). Cow, buffalo, sheep, goat, and horse excreta cause odor and pollution problems (Gupta, 2005; Garg et al., 2006; Nath et al., 2009). Animal dung and sewage sludge contain heavy metals that cause ill effects on soil as well as human health (Prajapati and Singh, 2013; Rusanescu et al., 2022). Heavy metals are generally re- ferred to as those metals which possess a specific density

    of more than 5 g/cm3 and adversely affect the environment and living organisms (Jarup, 2003). The safe value of Lead is 0.03 mg/kg, Chromium is 0.01 mg/kg and according to the FAO/WHO, the recommended tolerable daily Cd up- take is 0.01 to 0.035 mg/d (WHO, 1985, 1993). The toxic metals, persistent organic compounds, pathogenic bacteria, and parasite eggs, could pollute the soil and groundwater (Dume et al., 2022). High exposure to lead causes severe damage to the brain and kidneys, anemia, increased blood pressure, miscarriage in pregnant women, and reduced fer- tility in males (Cleveland et al., 2008). Ahmed et al. (2016) reported that chromium eventually accumulates in crops from contaminated soils and imparts health risks to humans


    and animals, through the food chain. Cadmium is primarily toxic to the kidney and it causes damage to the proximal tubules and failure of the tubular reabsorption leading to renal dysfunction (Lee et al., 2006).

    ‌Vermicomposting of sewage sludge with animal dung by Eisenia fetida is an ecological method of sewage sludge management (Spurgeon and Hopkin, 1999; Iwai et al., 2013). The worms break down these organic wastes and modify them into nutrient- rich organic manure i.e. vermi- compost. E. fetida is often used in vermicomposting as it reduces the C/N ratio, the pathogenic load of various wastes but increases the total Kjeldahl nitrogen (TKN) and total phosphorus (TP), hence obtaining good quality fertilizer for soil (Li et al., 2011; Iwai et al., 2013; Panday et al., 2014). Earthworm E. fetida biochemically degrades sewage sludge and homogenizes the material through the muscular actions of the intestine and releases nutrient- rich vermicompost for plants (Yadav et al., 2012; Purdea et al., 2019) by accumulat- ing heavy metals in their body during the vermicomposting (Suleiman et al., 2017; Singh and Bhartiya, 2021). The aim of the present study was to investigate the accumulation of heavy metals in earthworm E. fetida in vermicomposting of animal dung with sewage sludge and converted rich organic vermicompost which is ecologically sound and culturally most acceptable for agriculture.


  2. Materials and methods

    Collection of animal dung, earthworm, and sewage sludge (SS)-

    Dung of cow, buffalo, and goat dung and sewage sludge were collected from different parts of Gorakhpur city. These wastes were exposed to sunlight for 5 to 10 days for the removal of various harmful and noxious gases. E. fetida is an epigeic species used for this experiment collected from Vermibiotechnology Laboratory, Department of Zoology, D.D.U., Gorakhpur University, Gorakhpur. In the laboratory

    condition, the temperature was 20 ◦C to 30 ◦C and the mois- ture was maintained up to 40% to 60% for proper growth

    and survival of earthworms (Bhartiya and Singh, 2011; Nath and Singh, 2016).


    Experimental setup for vermicomposting

    Vermicomposting of different combinations of animal (cow, buffalo, and goat) dung with sewage sludge in 1:1, 1:2, and 1:3 ratios was used for the preparation of vermibeds which

    was conducted on the cemented earth surface. The size of each vermibed is (3 m length × 1 m width × 12 cm depth). 2 kg of cultured E. fetida inoculated in each bed and covered with jute pockets for proper moisture maintenance up to 40 to 50 days. Each vermibed manually turned over

    up to 5 weeks after a one- week interval. After 60 days, tea granules like vermicompost appeared on the upper surface of each bed. The prepared vermicompost and earthworms were used for chemical analysis and heavy metals Pb, Cr, and Cd concentrations (Bhartiya and Singh, 2012b; Nath and Singh, 2016).

    Analysis of heavy metals in initial feed mixture, final vermicompost, and earthworm body

    Heavy metal content of the initial feed mixture (IFM) and final vermicompost (FVC) was measured by the method of Maboeta and Rensburg (2003). 1 g of IFM and FVC is required for the preparation of samples. These samples were digested by adding nitric acid (1:1) placing on a hot

    plate and heating it for 4 hours at 90 ◦C to 100 ◦C and keep watching that the sample did not dry up after digestion sam-

    ple was poured into a 100 mL flask filter through Whatman No 41 paper.

    The heavy metals in the earthworm’s body tissue are di- gested using the method of Katz and Jenneis (1983). Earth- worms dried, ground, and burned to ash at high temper- atures. The ash was placed in a test tube with about 10 mL to 15 mL of 55% nitric acid (HNO3) added to it. The solution was left for 12 hrs at room temperature. The solu-

    tion heated at 40 ◦C to 60 ◦C for 2 hours and followed by 120 ◦C to 130 ◦C for one hour and 1 mL of 70% perchloric acid (HClO4) was added to it. The solution was allowed

    to cool and 5 mL of distilled water was added thereafter. The solution was again heated up to 130 ◦C until white fumes emitted. The solution was allowed to cool and fil- tered through the Whatman No 41 filter paper. This solution

    allowed for the analysis of heavy metals of the initial feed mixture, final vermicompost, and earthworm body by Shi- madzu AA- 7000 atomic absorption spectrometer (Najah et al., 2015).

    Calculation of heavy metals concentration in vermicom- post and earthworm body

    %decrease HMCs in VC = (IFM − FVC) × 100 mg/kg

    IFM

    %increase HMCs in earthworm body =

    (EfBFV − EfBC)

    EfBC × 100 mg/kg

    HMCs = heavy metals concentration IFM = initial feed mixture

    FVC = final vermicompost

    EfBC = earthworm Eisenia fetida body (control)

    EfBFV = earthworm Eisenia fetida body in final vermicom- post

    Statistical analysis

    All the data are mean ± SD of 6 replicates. Students ‘t’ test was applied to determine the significant (P < 0.05) differ-

    ‌ence between combinations of cow, buffalo, and goat dung with sewage sludge (SS) of initial, final vermicompost, be- fore inoculation and final earthworm E. fetida body (Sokal and Rohlf, 1973).

  3. Results and discussion

    Data emerging from results show there was a significant reduction of Pb, Cr, and Cd observed in prepared vermi- compost of different animal dung and sewage sludge in the ratios 1:1, 1:2, and 1:3. Chromium (Cr) was significantly decreased in cow dung (CD) and goat dung (GD) and cad- mium (Cd) in CD, CD+SS (1:1), BD and GD at BDL level.


    The Lead (Pb) was significantly decreased by 76.470% (0.527 ± 0.004 mg/kg to 0.124 ± 0.003 mg/kg) in the goat dung with sewage sludge GD+SS 1:1 ratio (Table 1 and Fig. 1), whereas Pb accumulated and significantly increased

    (5.248 ± 0.007 mg/kg to 6.456 ± 0.009 mg/kg) 23.018% in earthworm Eisenia fetida body in the combination of buf- falo dung with sewage sludge (BD+SS, 1:3). The Cr and Cd

    were significantly increased in the E. fetida body 3.384% (11.435 ± 0.012 mg/kg to 11.822 ± 0.009 mg/kg) and

    11.801% (3.347 ± 0.008 mg/kg to 3.742 ± 0.010 mg/kg), re-

    spectively, in the combination of buffalo dung with sewage

    sludge (BD+ SS) in ratio 1:3 (Table 2 and Fig. 2). Khwairak- pam and Bhargava (2009) reported that the combination of metal decreased during vermicomposting with all worm with Eudrilus eugeinae, Perionyx excavates and Eisenia fetida slightly more in case of lead.

    Eisenia fetida had a significant degree of accumulation of Cr, Pb, and Zn compared to Eudrilus eugeniae, and the bioaccumulation factor was higher in the case of E. fetida (Parseh et al., 2021). The bioaccumulation of metals in the body of E. fetida and E. andrei was thus Cd > Zn > Cu > Ni > Pb (Rorat et al., 2016). The metallothioneins (MTs)—


    ‌Figure 1. Concentration of heavy metals (mg/kg) in combi- nation of different animal dung with sewage sludge in initial feed mixture and vermicompost.

    small, cysteine- rich proteins of Lumbricus rubellus and common red earthworm (Eisenia fetida) that bind d10 metal ions (Zn(II), Cd(II), or Cu(I)) in clusters. Three MT homo- logues are known for one of which, wMT- 2, is strongly induced by exposure of worms to cadmium (Kowald et al., 2016). Earthworms have the ability to accumulate heavy metals, including Cu, Cd, Pb, and Zn by earthworm occurs through two pathways, which include absorption following dermal contact and adsorption through the intestinal tissues (Nirola et al., 2016; Wang et al., 2018; Lanno et al., 2019; Srut et al., 2019).

    ‌There was a significant increase of heavy metals in the body of inoculated earthworm Eisenia fetida after vermicompost- ing in a combination of animal dung with biological wastes during vermic- activity (Shahmansouri et al., 2005; Jordao et al., 2006; Bhartiya and Singh, 2012a, 2012b; Singh and Bhartiya, 2020a). Significant changes of fraction distribu- tion and bioavailability of these metals (Zn, Pb, Fe, Mn, Cr, Co, and Cu) occurred during earthworm activity (De- vliegher and Verstraete, 1996). A significant concentration of Cd accumulation was reported in the earthworm body of Eisenia fetida (Conder et al., 2002; Shahmansouri et al., 2005; Singh et al., 2014; Singh and Bhartiya, 2020b).



    ‌Figure 2. Concentration of heavy metals (mg/kg) of earth- worm Eisenia fetida body in different of combination animal dung with sewage sludge after vermicomposting.


    ‌Table 1. Concentration of heavy metals (mg/kg) in a combination of different animal dung with sewage sludge and vermicompost.


    Particulars Ratio Heavy metal concentration in mg/kg


    Pb

    IFM

    FVC

    % Decrease

    Cr

    IFM

    FVC

    % Decrease

    Cd

    IFM

    FVC

    % Decrease

    SS

    -

    2.196±0.010

    -

    -

    0.794±0.006

    -

    -

    0.538±0.009

    -

    -

    CD

    -

    0.331±0.005

    0.105±0.003*

    68.278

    0.199±0.004

    BDL*

    100

    0.045±0.005

    BDL*

    100

    CD+SS

    1:1

    0.530±0.003

    0.297±0.005*

    43.963

    0.356±0.005

    0.085±0.003*

    76.123

    0.209±0.005

    BDL*

    100


    1:2

    0.905±0.005

    0.340±0.004*

    62.431

    0.467±0.004

    0.162±0.004*

    65.310

    0.381±0.004

    0.112±0.006*

    70.603


    1:3

    1.560±0.008

    0.890±0.004*

    42.948

    0.598±0.004

    0.178±0.006*

    70.234

    0.390±0.005

    0.129±0.005*

    66.923

    BD

    -

    0.452±0.004

    0.119±0.005*

    73.672

    0.236±0.003

    0.092±0.004*

    61.016

    0.062±0.004

    BDL*

    100

    BD+SS

    1:1

    0.702±0.006

    0.255±0.004*

    63.675

    0.367±0.005

    0.156±0.005*

    57.493

    0.173±0.003

    0.043±0.004*

    75.144


    1:2

    1.025±0.006

    0.368±0.006*

    64.097

    0.402±0.003

    0.189±0.003*

    52.985

    0.210±0.004

    0.085±0.005*

    59.523


    1:3

    1.614±0.008

    0.795±0.005*

    50.743

    0.678±0.003

    0.308±0.004*

    54.572

    0.295±0.007

    0.106±0.004*

    64.067

    GD

    -

    0.149±0.004

    0.055±0.002*

    63.087

    0.127±0.004

    BDL*

    100

    0.196±0.004

    BDL*

    100

    GD+SS

    1:1

    0.527±0.004

    0.124±0.003*

    76.470

    0.250±0.005

    0.084±0.006*

    66.400

    0.309±0.003

    0.068±0.003*

    77.993


    1:2

    0.851±0.004

    0.209±0.005*

    64.027

    0.603±0.003

    0.196±0.005*

    67.495

    0.371±0.006

    0.096±0.004*

    74.123


    1:3

    1.272±0.009

    0.423±0.006*

    66.745

    0.675±0.003

    0.205±0.008*

    69.629

    0.467±0.006

    0.145±0.005*

    68.950

    * Significant P < 0.05 “t” test between animal dung, sewage sludge, and final vermicompost · Each value is the Mean ±SD of six replicates BDL-Below detectible limit i·e· 0.0001 mg/kg

    SS-sewage sludge, IFM- initial feed mixture, FVC- final vermicompost, CD-cow dung, BD-buffalo dung, GD-goat dung


    ‌Table 2. Concentration of heavy metals (mg/kg) of earthworm Eisenia fetida body in different combinations of animal dung with sewage sludge after vermicomposting.


    Particulars Ratios



    Heavy metal concentration

    in earthworm Eisenia fetida body (mg/kg)




    Pb



    Cr


    Cd




    IFM

    FVC

    % Decrease

    IFM

    FVC % Decrease

    IFM

    FVC

    % Decrease

    CD

    -

    5.248±0.007

    5.445±0.006*

    3.753

    11.435±0.012

    11.552±0.008*

    1.023

    3.347±0.008

    3.552±0.005*

    6.124

    CD+SS

    1:1

    5.248±0.007

    5.406±0.004*

    3.010

    11.435±0.012

    11.659±0.006*

    1.958

    3.347±0.008

    3.565±0.005*

    6.513


    1:2

    5.248±0.007

    5.619±0.003*

    7.069

    11.435±0.012

    11.806±0.006*

    3.244

    3.347±0.008

    3.704±0.004*

    10.666


    1:3

    5.248±0.007

    6.040±0.008*

    15.091

    11.435±0.012

    11.822±0.009*

    3.384

    3.347±0.008

    3.742±0.010*

    11.801

    BD

    -

    5.248±0.007

    5.662±0.004*

    7.888

    11.435±0.012

    11.588±0.004*

    1.337

    3.347±0.008

    3.411±0.007*

    .912

    BD+SS

    1:1

    5.248±0.007

    5.769±0.005*

    9.927

    11.435±0.012

    11.592±0.005*

    1.372

    3.347±0.008

    3.463±0.006*

    3.465


    1:2

    5.248±0.007

    6.045±0.003*

    15.186

    11.435±0.012

    11.685±0.006*

    2.186

    3.347±0.008

    3.475±0.005*

    3.824


    1:3

    5.248±0.007

    6.456±0.009*

    23.018

    11.435±0.012

    11.762±0.006*

    2.859

    3.347±0.008

    3.650±0.008*

    9.052

    GD

    -

    5.248±0.007

    5.450±0.003*

    3.849

    11.435±0.012

    11.505±0.007*

    0.612

    3.347±0.008

    3.501±0.004*

    4.601

    GD+SS

    1:1

    5.248±0.007

    5.601±0.004*

    6.726

    11.435±0.012

    11.560±0.005*

    1.093

    3.347±0.008

    3.545±0.006*

    5.915


    1:2

    5.248±0.007

    5.670±0.005*

    8.041

    11.435±0.012

    11.723±0.008*

    2.518

    3.347±0.008

    3.673±0.005*

    9.740


    1:3

    5.248±0.007

    6.186±0.005*

    17.873

    11.435±0.012

    11.775±0.009*

    2.973

    3.347±0.008

    3.705±0.007*

    10.696

    * Significant P<0.05 “t” test between earthworm body of each vermibeds before inoculation and after vermicomposting Each value is the Mean ±SD of six replicates

    SS-sewage sludge, EfBC- earthworm Eisenia fetida body (control)

    EfBFV- earthworm Eisenia fetida body in final vermicomposting, CD-cow dung, BD-buffalo dung, GD-goat dung


  4. Conclusion

Eisenia fetida accumulated heavy metals in their body tissues from different combinations of cow, buffalo, and goat dung with sewage sludge in the ratios 1:1, 1:2, and 1:3. There was a significant decrease in the concentration of Pb, Cr, and Cd in different animal dung with sewage sludge during vermicomposting. Cr and Cd were significantly decreased in cow dung (CD) and goat dung (GD) at the BDL level whereas the Pb concentration significantly decreased (89.261%) in the combination of GD+SS (1:1).

E. fetida was a suitable species for the accumulation of Pb, Cr, and Cd from different waste during vermicomposting. The result of the study showed that earthworms play an important role in the remediation of heavy metals from sewage sludge with different combinations of animal dung.


Acknowledgment

The authors are thankful to Dr Jaswinder Singh, Associate Professor, Post Graduate Department of Zoology, Khalsa College, Amritsar, Punjab, India for technical support.



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References

Author contribution

All authors are contributed in experiment as well as paper drafting and writing.


Availability of data and materials

The data that support the findings of this study are available from the corresponding author upon reasonable request.


Conflict of interests

The authors declare that they have no known com- peting financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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