Eisenia fetida and biochar synergistically alleviate the heavy metals content during valorization of biosolids via enhancing vermicompost quality

Muhammad Bilal Khan; Xiaoqiang Cui; Ghulam Jilani; Ugit Lazzat; Afsheen Zehra; Yasir Hamid; Bilal Hussain; Lin Tang; Xiaoe Yang; Zhenli He

doi:10.1016/j.scitotenv.2019.05.370

Eisenia fetida and biochar synergistically alleviate the heavy metals content during valorization of biosolids via enhancing vermicompost quality

Sci Total Environ. 2019 Sep 20:684:597-609. doi: 10.1016/j.scitotenv.2019.05.370. Epub 2019 May 28.

Authors

Affiliations

¹ Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
² Institute of Soil Science, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan.
³ Institute of Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
⁴ Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address: xeyang@zju.edu.cn.
⁵ Soil and Water Science Department, Indian River Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Fort Pierce, FL 34945, USA.

PMID: 31158623
DOI: 10.1016/j.scitotenv.2019.05.370

Abstract

Impact of different biochars supplemented (10% w/w) to promote vermicomposting of sewage sludge (SS) and kitchen waste (KW) mixture (SS + KW, 70:30) was studied on the growth, reproduction and survival of earthworms, and ultimately the quality of vermicompost. Four types of biochar used as secondary material for preincubation (16 days) and vermicomposting (30 days) were: pine tree biochar (PTB), poplar plant biochar (PPB), wetland plant biochar (WPB) and yard waste biochar (YWB). Preincubation and vermicomposting of biomass mixture were undertaken in 60 L and 2 L capacity round-shaped bioreactors, respectively. Samples of biomass undergoing degradation were drawn after every 2 days during preincubation and with 5 days interval during vermicomposting to analyze them for plant nutrients and heavy metals contents. Amendment of vermicompost substrate (SS + KW) with biochars; PTB, PPB, WPB and YWB increased the reproduction rate of earthworms (Eisenia fetida) by 44.6, 53.9, 29.3 and 38.8%, respectively as compared to control (no biochar, NB). There has been significant reduction in total content of Cd (0.2-5.1%), Cr (7.3-10.8%), Cu (3.1-7.4%), Mn (3.2-8.4%), Pb (9.0-45.9%) and Zn (1.1-5.7%) by the application of different biochars as compared to NB after vermicomposting. The SEM/EDS images also reflected reduced concentration of these heavy metals in the final vermicompost as compared to initial mixtures. Progressively, biochar amendments increased the concentration of all macronutrients, viz., TN (15.8-31.0%), TP (8.6-9.9%), TK (2.8-17.3%), Ca (4.1-9.9%) and Mg (0.8-12.2%); while, reduced the pH (1.9-2.3%), content of Na (6.6-22.3%), TOC (6.6-15.4%), OM (5.0-8.2%) and C:N ratio (2.6-18.9%). Earthworm body accumulation factor (BAF) of heavy metals was: Cd > Zn > Pb > Cu > Mn > Cr at the termination stage of experiment. In conclusion, amending the SS + KW mixture with 10% (w/w) PPB for vermicomposting rendered higher count of cocoons, growth rate and reproduction rate of earthworms, which ultimately produce nutrients-rich vermicompost lower in heavy metals.

Keywords: Bioaccumulation factor; Biochar; Earthworms; Kitchen waste; Nutrients-rich compost; Sewage sludge.

MeSH terms

Animals
Charcoal / analysis*
Charcoal / classification
Composting / methods*
Metals, Heavy / chemistry*
Oligochaeta / growth & development
Oligochaeta / physiology*
Sewage / analysis*
Soil / chemistry*
Soil Pollutants / chemistry*

Substances

Metals, Heavy
Sewage
Soil
Soil Pollutants
biochar
Charcoal