Bioaccumulation of heavy metals during composting and vermicomposting processes of sewage sludge

Abstract

Using of sewage sludge as an organic fertilizer is restricted by international standards because it contains heavy elements in addition to, pathogenic microorganisms. Therefore, this study aimed to use technology of both composting and vermicomposting to remove heavy elements from sewage sludge by using bio-accelerator (Trichoderma harzianum, Trichoderma viride and Phanerochaete chrysosporium,) and vermi worms (Eisenia fetida) individually or combined together. The results showed that the use of bio-accelerator and Eisenia fetida worms together had a significantly positive effect on reducting the concentration of heavy metals to the safe limit compared to the Egyptian code during the 12-week experiment period, where it decreased the available concentration of heavy metals (Lead, Nickel and Cadmium) from 6.429, 4.448 and 0.197 in the initial experiment to 0.213, 0.142 and 0.065 mg /kg in the final experiment, respectively. Also, total concentrations of heavy metals were reduced to 313.95, 210.40 and 10.85 for Pb, Ni and Cd (mg/ kg) initially; meanwhile, the final concentrations did not exceed either the Egyptian code limits or worldwide Standards. In addition, to improve quality (NPK) of organic fertilizers and safety represented the highest percentage of removal 72, 67 and 62% for Cd, Ni and Pb respectively. So, this technique for sewage sludge treatment is considered promising for production of quality organic fertilizer and safe environmentally.

A Systematic Review on Earthworms in Soil Bioremediation

“…Xiao et al [139] evaluated the influence of Bacillus megatherium on the remediation process of earthworms in Cd removal from artificially contaminated soils. In this study, the combined treatment (S + E + M) had a Cd content at the end of the experiment statistically lower than the soil treated with earthworms alone (S + E) (Figure 4), contradicting what was observed by El-Hassanin et al [138]. Microorganisms can enhance the metals' bioavailability in soil by altering pH, oxidation/reduction reactions and chelator ions [140].…”

“…Consequently, several authors have recently investigated the effectiveness of bioaugmentation combined with vermiremediation. El-Hassanin et al [138] investigated the remediation capacity of E. fetida and fungal bio-accelerators (Trichoderma harzianum, viride and Phanerochaete chrysosporium), alone or in combination; the substrate was composed of sewage sludge and rice straw in different percentages, contaminated with Cd, Ni and Pb. As can be seen from Figure 4, the use of E. fetida, individually or in combination, gave promising results; the highest percentage reductions for all analysed contaminants were found in treatment where the sewage sludge and rice straw ratio was 1:1 (S3 + E + M) where (Cd 72%, Ni 67%, Pb 62%).…”

The Impact of Using Different Types of Compost on the Growth and Yield of Corn

“…El-Hassanin et al [48] and Rékási et al [49] highlight limitations in using sewage sludge as a fertilizer due to the pathogenic microorganisms and heavy metals it contains, in line with international standards. However, they assert that with proper treatment and processing, sewage sludge can be transformed into a valuable and environmentally safe organic fertilizer.…”

Improving the Agronomic Value of Paddy Straw Using Trichoderma harzianum, Eisenia fetida and Cow Dung

“…Composting is one of the eco-friendly biological processes for recycling nutrients in agricultural Fermentation 2023, 9, 671 2 of 14 fields. It is a transformation process that changes agricultural wastes into a biodegradable stabilized and mineralized humus by microorganisms including bacteria and fungi [9], while vermicomposting is a process that converts biodegradable waste into organic manure with the help of mainly earthworms and microorganisms. Vermicomposting is a biochemical process that recycles nutrients in the soil and makes them available for plant growth.…”

“…The consortium of earthworms and lignocellulolytic microbiota plays an important role in solid waste degradation, as they decrease the composting period by altering the structure of solid waste with their enzymatic actions [9,18]. Microbial communities and enzyme activities can be used to describe the dynamics of the composting process, including the decomposition of organic matter, its stability and its maturity [19].…”