Determination of the performance of vermicomposting process applied to sewage sludge by monitoring of the compost quality and immune responses in three earthworm species: Eisenia fetida, Eisenia andrei and Dendrobaena veneta

Eisenia fetida-driven vermitechnology for the eco-friendly transformation of steel waste slag into organic amendment: An insight through microbial diversity and multi-model approach

The processing of steel waste slag from the black metallurgical sector seriously threatened the ecology. To counter these dangers, appropriate detoxification methods were required. Vermitechnology was one such strategy that could successfully convert this industrial waste into nutrient-rich products suitable for use in agriculture. This research primarily focuses on employing vermitechnology for the transformation of waste steel slag into vermicompost and to determine changes in microbial composition, nutrient cycling, and metal detoxification facilitated by earthworms (Eisenia fetida). Earthworm populations in steel waste vermibeds (sw-vermibeds) increased by 2.87-3.07 folds. T1(SW + CD-1:1) comparatively showed increased levels of nutrients such as nitrogen, phosphorus, and potassium. Microbial and enzymatic parameters were more pronounced in treatment T1. The findings of phospholipid fatty acid (PLFA) diversity demonstrate microbial diversity and fatty acid composition. Based on PLFA Sobol Sensitivity Analysis (SSA), PUFA and cyclo were the most sensitive inputs to the presence of heavy metal (HMs) concentrations in SW. In accordance with Taylor-based modelling, R-tree, and Mars were the most trusted regression models for predicting HMs toxicity on microbes. The bioavailable metal fractions of HMs (Fe, Ni, Cd, Cu, Pb, and Cr) decreased by 61-83%. The correlation was performed for 0 and 90 days for metal microbial interactions r (0 days), [BSR vs Fe, Cd, Cu, Ni = -0.99, -0.82, -0.43, -0.99] and r (90 days), [FDA vs Fe, Cu, Ni = -0.97, -0.47, -0.95]. Overall, the results indicated that T1(1:1 SW + CD) provided more favorable conditions for the development of microbes and Eisenia fetida. This research presents a new perspective to the world community on the transformation of harmful steel waste slag into advantageous biological resources by introducing a novel method of employing Eisenia fetida to remediate hazardous steel waste slag.

New insights into vermiremediation of sewage sludge: The effect of earthworms on micropollutants and vice versa

Vermicomposting represents an environmentally friendly method for the treatment of various types of biowastes, including sewage sludge (SS), as documented in numerous studies. However, there are few papers providing insights into the mechanisms and toxicity effects involved in SS vermicomposting to present a comprehensive overview of the process. In this work, the vermiremediation of SS containing various micropollutants, including pharmaceuticals, personal care products, endocrine disruptors, and per/polyfluoroalkyl substances, was studied. Two SSs originating from different wastewater treatment plants (WWTP1 and WWTP2) were mixed with a bulking agent, moistened straw, at ratios of 0, 25, 50, and 75% SS. Eisenia andrei earthworms were introduced into the mixtures, and after six weeks, the resulting materials were subjected to various types of chemical and toxicological analyses, including conventional assays (mortality, weight) as well as tissue- and cell-level assays, such as malondialdehyde production, cytotoxicity tests and gene expression assays. Through the vermiremediation process significant removal of diclofenac (90%), metoprolol (88%), telmisartan (62%), and triclosan (81%) was achieved. Although the concentrations of micropollutants were substantially different in the original SS samples, the micropollutants vermiaccumulated to a similar extent over the incubation period. The earthworms substantially eliminated the present bacterial populations, especially in the 75% SS treatments, in which the average declines were 90 and 79% for WWTP1 and WWTP2, respectively. To the best of our knowledge, this is the first study to investigate the vermiremediation of such a large group of micropollutants in real SS samples and provide a thorough evaluation of the effect of SS on earthworms at tissue and cellular level.

Vermicomposting as an effective approach to municipal sewage sludge management through optimization of the selected process variables

In most developing countries, municipal sewage sludge end-use practices appear unsustainable; rather, it poses environmental concerns. This study examined the potential of vermicomposting of municipal sewage sludge and its blend with other biowaste for agricultural application. Using a response surface methodology and the Box-Behnken design in Design Expert Software (Version 10.0.7), the current study optimized the moisture content (60-90%), turning frequency (1-3 turnings/week), and substrate mixing ratios (50:50 to 80:20 wt.%) to maximize the content of nitrogen, phosphorus, and potassium. As a result, an optimal moisture content (72%), substrate mixing ratio (72.34:27.6 wt.%), and turning frequency (2 per week), producing a promising-quality vermicompost with a maximum yield of nitrogen (2.76%), phosphorus (1.80%), and potassium (1.88%) is achieved. Thus, vermicomposting can effectively turn the concerning municipal sewage sludge into useful agricultural input for its sustainable management.

Environmental impacts and optimization simulation of aerobic anaerobic combination treatment technology for food waste with life cycle assessment

After the implementation of waste sorting policy in Shanghai, the amount of food waste (FW) separation and treatment demand has increased significantly. It is necessary to establish the life cycle assessment (LCA) to assess the environmental impacts of various treatment technologies comprehensively, thus provide support for sorting, recycling, treatment and disposal strategies of FW. In this study, a local FW treatment plant in Shanghai, using typically aerobic anaerobic combination treatment technology was selected to analyze the environmental impacts with LCA. The process mainly included pretreatment, power, aerobic composting, anaerobic digestion, and further process systems. LCA results showed that the environmental impacts mainly came from the power and aerobic composting systems on the fine particulate matter formation and eutrophication, and freshwater ecotoxicity and terrestrial acidification, respectively. Considering the carbon footprint, the aerobic composting system contributed 3.61E + 02 kg CO₂ eq and represented the largest source of carbon emission. The soil conditioner yielded both environmental benefits on eutrophication and terrestrial ecotoxicity, and ecological benefits of 75.33 million CNY per year being the major revenue for the treatment plant. It also suggested that the biogas generation capacity of anaerobic digestion could be increased to achieve electricity self-sufficiency, thus save about 7.12 million CNY per year in electricity costs, and avoid corresponding environmental impacts caused by coal-fired. In summary, the aerobic anaerobic combination treatment could be further optimized and applied in FW treatment to reduce the environmental impacts, and enhance resource recovery and secondary pollution control.

Efficacy of cow and buffalo dung on vermiremediation and phytoremediation of heavy metals via Fourier-transform infrared spectroscopy and comet assay

Heavy metal contamination raised significant concerns throughout the world. The current research aimed to evaluate the impact of organic manure (cow dung and buffalo dung) on vermiremediation and phytoremediation and to remediate heavy metals, i.e., cadmium, lead, and chromium, from artificial contaminated soil via both remediation techniques. The impact of livestock manure was evaluated for the first time which could be effective in in situ as well as ex situ studies. Eisenia fetida, Pheretima lignicola, and Spinacia oleracea were used for the remediation process. Results revealed that E. fetida tolerated lead at 280 mg, cadmium at 150 mg, and chromium at 860 mg compared to P. lignicola. The growth and reproduction of E. fetida were efficient in the cow dung manure compared to buffalo dung. Similarly, seed germination and growth of Spinacia oleracea were better in cow dung media compared to buffalo dung. Bioaccumulation factor showed that E. fetida showed a higher accumulation of heavy metals in their tissues when vermi + phytoremediation was jointly applied (9.50 mg/l of Pb, 24.166 of Cd, and 6.695 of Cr). Fourier-transform infrared spectroscopy indicated that heavy metals had no drastic effects on E. fetida and S. oleracea. Similarly, comet assay revealed that heavy metals had no genotoxic effect on the E. fetida and S. oleracea. It was concluded that both E. fetida and S. oleracea are appropriate for heavy metals remediation in cow dung manure.

Vermicomposting of textile mill sludge employing Eisenia fetida: Role of cow dung and tea waste amendments

Vermicomposting of textile mill sludge (TMS) with cow dung (CD) and tea waste (TW) as amendments was done in seven different combinations using Eisenia fetida for 90 days. Results revealed that pH decreased from 7.68-8.63 to 7.09-7.59. TOC content and C/N ratio reductions were in range of 15.71-20.08% and 39.33-50.05%, respectively (P < 0.05). The macronutrients in the form of TN, TP, and TK increased 0.38-0.64, 1.07-2.27, and 0.56-1.98 times respectively after end of bioconversion process (P < 0.05), among increases in ash content and EC. The biomass and cocoon production of E. fetida increased significantly (P < 0.05), while high mortality rate of earthworms was observed in treatments containing 50% or more TMS content. The bacterial population beneficial for degradation of organic matter increased significantly over initial substrates (0th day) (P < 0.05). Increased humification index in end-product indicated better maturity of vermicompost as observed in treatments containing higher proportions of amendments. The addition of amendments favored earthworm activity which significantly decreased the heavy metal concentration (Fe, Cu, Pb, Zn) in the end-product. The study concluded that sustainable utilization of TMS could be achieved for cleaner and enriched vermicompost production by addition of amendments CD and TW in proportions of 50% and above.

Earthworm Eisenia fetida potential for sewage sludge amended soil valorization by heavy metal remediation and soil quality improvement

Sewage sludge reuse in agriculture is increasing, however it can be an important route for contaminants to enter the environment. The aim of this study was to evaluate earthworm Eisenia fetida capability to reduce heavy metal content in the sewage sludge (SS) amended soil and increase soil fertility in terms of soil nutrients content. Adult earthworms were introduced into aged SS amended soil (0-200 Mg ha^-1) and left for 65 days. Earthworms have stabilized soil pH and accelerated organic matter mineralization. The concentrations of most heavy metals during the vermiremediation sharply decreased, K and Mg decreased to a moderate extent, whereas Ca content has increased. The highest removal efficiency was detected for Ni, Co and Mn (> 80%), bioconcentration factors were as follows Zn > Co > Cu > Ni > Mn > Cr. The content of major nutrients (S, P) was substantially higher compared to the initial values. The most efficient remediation and soil quality improvement was achieved under the doses of 25-50 Mg ha^-1. Higher (≥ 100 Mg ha^-1) doses might restrict this technique application because of earthworm mortality and retarded growth. Overall, the study shows that vermiremediation might be a sustainable technique for ecological stabilization of SS amended soil and converting to usable for agricultural needs.

Epigenetic regulations enhance adaptability and valorization efficiency in Eisenia fetida and Eudrilus eugeniae during vermicomposting of textile sludge: Insights on repair mechanisms of metal-induced genetic damage and oxidative stress

Genotoxicity-based assessments of vermitechnology for textile-sludge valorization have rarely been attempted. Therefore, waste sanitization and epigenetic stress-regulation efficiency of Eisenia fetida and Eudrilus eugeniae were evaluated in silk (DSPS) and cotton (CPWS) processing sludge-based vermibeds. Vermicomposting resulted in greater C, N, and P recovery than composting. Earthworm population reduced by 6-50% in DSPS/CPWS, while it significantly increased in cow dung (CD) mixed DSPS/CPWS. The Cr, Cd, Pb, and Zn accumulation efficiency of earthworms was higher in DSPS-based feedstocks than CPWS. However, metal-rich sludge elevated oxidative stress, causing greater inhibition of cell viability and DNA damage in Eudrilus than in Eisenia. Although histo-architecture of chloragogenous tissues was perturbed, earthworms combatted metal-induced lipid peroxidation via the activation of catalase, superoxide-dismutase, and reduced-glutathione. Correlation statistics revealed that genetic integrity in earthworms was restored through DNA-methyltransferase activity, especially in DSPS/CPWS + CD vermibeds. Overall, Eisenia was a healthier choice than Eudrilus for sustainable valorization of textile-sludge.

Earthworms as candidates for remediation of potentially toxic elements contaminated soils and mitigating the environmental and human health risks: A review

Global concerns towards potentially toxic elements (PTEs) are steadily increasing due to the significant threats that PTEs pose to human health and environmental quality. This calls for immediate, effective and efficient remediation solutions. Earthworms, the 'ecosystem engineers', can modify and improve soil health and enhance plant productivity. Recently, considerable attention has been paid to the potential of earthworms, alone or combined with other soil organisms and/or soil amendments, to remediate PTEs contaminated soils. However, the use of earthworms in the remediation of PTEs contaminated soil (i.e., vermiremediation) has not been thoroughly reviewed to date. Therefore, this review discusses and provides comprehensive insights into the suitability of earthworms as potential candidates for bioremediation of PTEs contaminated soils and mitigating environmental and human health risks. Specifically, we reviewed and discussed: i) the occurrence and abundance of earthworms in PTEs contaminated soils; ii) the influence of PTEs on earthworm communities in contaminated soils; iii) factors affecting earthworm PTEs accumulation and elimination, and iv) the dynamics and fate of PTEs in earthworm amended soils. The technical feasibility, knowledge gaps, and practical challenges have been worked out and critically discussed. Therefore, this review could provide a reference and guidance for bio-restoration of PTEs contaminated soils and shall also help developing innovative and applicable solutions for controlling PTEs bioavailability for the remediation of contaminated soils and the mitigation of the environment and human risks.

Effects of TiO2 and ZnO nanoparticles on vermicomposting of dewatered sludge: studies based on the humification and microbial profiles of vermicompost

Nanoparticles (NPs) are prevalent in dewatered sludge, and their presence increases the environmental risks associated with the subsequent sludge treatment process. However, until now, their potential effects on sludge vermicomposting have not been clarified. This study investigated the effects of NPs on sludge humification and microbial profiles during vermicomposting by comparing fresh dewatered sludge substrates with substrates mixed with 0 mg/kg NPs (control), 100 mg/kg TiO₂, 500 mg/kg TiO₂, 100 mg/kg ZnO, and 500 mg/kg ZnO. The results showed that addition of TiO₂ and ZnO NPs to sludge did not significantly affect the growth rate of earthworms and the superoxide dismutase activity in their guts during vermicomposting. Moreover, higher concentrations of the selected NPs promoted the humification index of sludge by 20.7-49.6%, through the formation of polysaccharides, aromatic substances, and organic acids in final vermicomposts. Compared with the control without NP addition, bacterial community diversity was enhanced in treatments with TiO₂ and ZnO NPs, and dominant genera differed according to the type and concentration of NPs. This study suggests that the presence of TiO₂ and ZnO NP residuals modify the microbial community of sludge, thus promoting sludge humification during vermicomposting.

Transfer of sulfidized silver from silver nanoparticles, in sewage sludge, to plants and primary consumers in agricultural soil environment

Consumer products containing silver nanoparticles (AgNPs) release silver (Ag) to the environment, particularly wastewater. Sewage sludge (SS), which contains numerous contaminants including Ag, is recycled by spreading on agricultural land. Although slight impacts and bioaccumulation of Ag sulfide (Ag₂S, the main species found in SS) in terrestrial organisms have been demonstrated, possible trophic transfer into plants and subsequently animal species has not been examined. Accordingly, the present study experimentally measured the transfer of Ag from AgNPs and sulfidized Ag into plants and primary consumers and compared their bioavailability. Nine plant cultivars were grown in soil mixed with SS containing Ag, which revealed that bioaccumulation of Ag by plants is species-dependent. Ryegrass (the plant species with the greatest accumulation - up to 0.2 mg kg^-1) was then cultivated on a larger scale to expose snails and locusts for several weeks. While locusts did not accumulate Ag after two weeks of exposure, snails exhibited Ag bioaccumulation after 5 weeks when soil was accessible. Sulfidized Ag derived from AgNPs were less available (bioaccumulation up to 2.5 mg kg^-1) than the Ag from the original AgNPs (bioaccumulation up to 15 mg kg^-1). This transfer potential of Ag could have consequences for food webs due to chronic exposure linked to SS spreading practices. This study shows that transformations of AgNPs in treatment plants attenuate but do not completely eliminate the risk of Ag to plant and animal species SS.

Effect of Vermicompost Amendment on the Accumulation and Chemical Forms of Trace Metals in Leafy Vegetables Grown in Contaminated Soils

(1) Background: Trace metal (TM) contamination of farmland soil in Taiwan occurs because factories dump wastewater into irrigation ditches. Since vermicompost affects the bioavailability of TMs, the objective of this study was to evaluate its effects on the accumulation of growth of TMs in leafy vegetables. (2) Methods: Two TM-contaminated soils and different types of pak choi and lettuce were used and amended with vermicompost. Besides soil properties, the study assessed vermicompost’s influence on the growth, accumulation, and chemical forms of TMs and on the health risks posed by oral intake. (3) Results: Vermicompost could increase the content of soil organic matter, available phosphorus, exchangeable magnesium, and exchangeable potassium, thus promoting the growth of leafy vegetables. The accumulation of four TMs in crops under vermicompost was reduced compared to the control, especially for the concentration of cadmium, which decreased by 60–75%. The vermicompost’s influence on changing the chemical form of TMs depended on the TM concentrations, type of TM, and crop species; moreover, blanching effectively reduced the concentrations of TMs in high-mobility chemical forms. Although vermicompost mostly reduced the amount of cadmium consumed via oral intake, cadmium still posed the highest health risk compared to the other three TMs.

Medium-term effects of Ag supplied directly or via sewage sludge to an agricultural soil on Eisenia fetida earthworm and soil microbial communities

The widespread use of silver nanoparticles (AgNPs) in consumer products that release Ag throughout their life cycle has raised potential environmental concerns. AgNPs primarily accumulate in soil through the spreading of sewage sludge (SS). In this study, the effects of direct exposure to AgNPs or indirect exposure via SS contaminated with AgNPs on the earthworm Eisenia fetida and soil microbial communities were compared, through 3 scenarios offering increasing exposure concentrations. The effects of Ag speciation were analyzed by spiking SS with AgNPs or AgNO₃ before application to soil. SS treatment strongly impacted Ag speciation due to the formation of Ag₂S species that remained sulfided after mixing in the soil. The life traits and expression of lysenin, superoxide dismutase, cd-metallothionein genes in earthworms were not impacted by Ag after 5 weeks of exposure, but direct exposure to Ag without SS led to bioaccumulation of Ag, suggesting transfer in the food chain. Ag exposure led to a decrease in potential carbon respiration only when directly added to the soil. The addition of SS had a greater effect on soil microbial diversity than the form of Ag, and the formation of Ag sulfides in SS reduced the impact of AgNPs on E. fetida and soil microorganisms compared with direct addition.

Species-specific Cd-detoxification mechanisms in lumbricid earthworms Eisenia andrei, Eisenia fetida and their hybrids

Hermaphroditic lumbricid Eisenia sp. earthworms are ubiquitous and highly resistant to a variety of environmental stressors, including heavy metals. Among the progeny of laboratory mated inter-specific pairs of Eisenia fetida (Ea) and Eisenia andrei (Ef) there are fertile Ha hybrids derived from Ea ova fertilized by Ef spermatozoa and very rare sterile Hf hybrids from Ef ova fertilized by Ea spermatozoa. The aim of the first part of the experiment was to compare the life traits and whole body accumulation of cadmium in adult earthworms from genetically defined Ea, Ef and their hybrids (Ha) exposed for four weeks to commercial soil either unpolluted (control) or cadmium-spiked leading to moderate (M) or high (H) soil pollution (M = 425 and H = 835 mg kg^-1 dry soil weight). Such exposure impaired cocoon production but not affected earthworm viability despite the massive Cd bioaccumulation in the whole earthworm bodies reaching at M and H groups 316-454, 203-338, 114-253, and 377-309 mg kg^-1 dry body weights of Ea, Ef1, Ef2, and Ha, respectively, surprisingly reaching maximum accumulation quantities in hybrids. The second part of the experiment aimed to investigate cadmium-related defense mechanisms at transcriptomic level in coelomocytes non-invasively extruded from coelomic cavities of the new sets of Ea, Ef, Ha, and Hf earthworms exposed to Cd in microcosms for 0 days (control), 2 days, and 7 days (M = 425 mg kg^-1). Expression level of stress-induced Cd-metallothionein (mt) and superoxide dismutase (sod) were gradually up-regulated, while the immune-connected lysenin (lys) was rapidly down-regulated; the expression of glutathione S-transferase (gst) and phytochelatin synthase (pcs) remained unaffected. Mt and sod gene up-regulation and lys gene down-regulation were especially pronounced in Ea-derived hybrids. In sum, capacity of cadmium bioaccumulation and detoxification mechanisms is more efficient in interspecific hybrids than in the pure Ea and Ef species.

Cryptic speciation and blurred species boundaries of the earthworm: A challenge for soil-based toxicological risk assessments

The toxicological risk assessment of chemicals is largely based on the Organization for Economic Co-operation and Development (OECD) guidelines. These internationally approved methodologies help shape policy and political strategy of environment and human health issues. Risk assessments which pertain to soil biota 'recruit' sentinel organisms, including the earthworm Eisenia fetida. Despite E. fetida being morphologically similar to Dendrobaena veneta, they are characterized by a several-fold difference in sensitivity to xenobiotics. Worms, sold as either as pure E. fetida stocks or E. fetida/D. veneta mixed cultures, were obtained from five commercial suppliers. The species identity of 25 earthworms was determined by sequencing the cytochrome c oxidase subunit 2 (COII). We revealed that only one of 25 worms was E. fetida, the remaining worms were all identified as D. veneta. This underlines the notion that E. fetida and D. veneta are easily mis-identified. The occurrence of cryptic speciation combined with the well-documented species-specific variation in toxicological responses highlights the pressing need to accurately classify earthworms to species level prior to any toxicological research. Only this will ensure the validity and reliability of risk assessments.

Earthworms and vermicompost: an eco-friendly approach for repaying nature's debt

The steady increase in the world's population has intensified the need for crop productivity, but the majority of the agricultural practices are associated with adverse effects on the environment. Such undesired environmental outcomes may be mitigated by utilizing biological agents as part of farming practice. The present review article summarizes the analyses of the current status of global agriculture and soil scenarios; a description of the role of earthworms and their products as better biofertilizer; and suggestions for the rejuvenation of such technology despite significant lapses and gaps in research and extension programs. By maintaining a close collaboration with farmers, we have recognized a shift in their attitude and renewed optimism toward nature-based green technology. Based on these relations, it is inferred that the application of earthworm-mediated vermitechnology increases sustainable development by strengthening the underlying economic, social and ecological framework.

Using Sewage Sludge Ash as an Efficient Adsorbent for Pb (II) and Cu (II) in Single and Binary Systems

Incineration of sewage sludge produces every year huge amounts of sewage sludge ash. Due to its porosity and composition, sewage sludge ash can be used as an adsorbent for heavy metal ions removal. The present paper discusses the efficiency and feasibility of its use as an adsorbent for Pb (II) and Cu (II) removal in single and binary systems. Sewage sludge ash dosage, pH influence, equilibrium and kinetic studies were examined. The results show that sewage sludge ash is an effective and environmentally friendly adsorbent. The maximum adsorption capacity was 25.0 mg/g for Pb (II) and 7.5 mg/g for Cu (II). The presence of the competitive metal led to lower adsorption rate. The study concludes that sewage sludge ash is a promising adsorbent for Pb (II) and Cu (II) removal from wastewater presenting both economic and environmental benefits.

Effects of elevated temperatures and cadmium exposure on stress biomarkers at different biological complexity levels in Eisenia fetida earthworms

Several ecotoxicological studies assessed metal toxicity upon soil biota and other communities but were mainly focused on the study of a single chemical and usually under optimal conditions of temperature. Meanwhile an increasing global warming is leading to new scenarios by combining different stress factors; chemical stress and thermal stress. Presently, this study aims to assess the joint effects produced by cadmium and elevated temperature on earthworms different levels of biological complexity. Eisenia fetida earthworms were maintained at 19 °C and 26 °C and simultaneously exposed to four Cd concentrations (1.25, 2.5, 25 and 125 mg Cd/Kg soil) for 14 (Short term exposure) and 56 days (reproduction test). Endpoints were addressed at different levels of biological complexity: reproductive impairment (cocoons and juvenile productions), Cd tissue accumulation, mortality of adults, weight loss and cytotoxic effects (coelomocyte viability). In the Short term exposure, increase in temperature produced a larger accumulation of Cd. Hence, earthworms exposed to 125 mg Cd/kg soil under heat stress (26 °C) showed a two fold higher Cd accumulation comparing to those at 19 °C. Earthworms exposed to moderate-high concentrations of Cd (2.5-125 mg Cd/kg) and maintained at 26 °C showed severe weight loss and high mortality rates. The neutral red uptake capacity of coelomocytes extruded from earthworms exposed to the highest Cd concentration decreased after 14 d at 19 °C, and more markedly at 26 °C. The reproduction impairment (decreased number of cocoons) was enhanced after exposure to concentrations higher than 2.5 mg Cd/kg at 26 °C, and after exposure to 125 mg Cd/kg at 19 °C. Earthworm reproduction capability is highly vulnerable to the effect of toxicants at elevated temperatures and sublethal concentrations.

Detoxification and eco-friendly recycling of brick kiln coal ash using Eisenia fetida: A clean approach through vermitechnology

Brick kiln coal ashes (BKCAs) are one of the major toxic byproducts of the rapidly growing construction industry in developing countries. However, eco-friendly recycling avenues for BKCAs are yet to be explored. The major objectives of the present research were to evaluate the viability of vermitechnology in transforming BKCAs into valuable products, and to examine the metal detoxification potential of Eisenia fetida BKCA-based feedstocks. BKCAs were mixed in large scale with cow dung (CD) in 1:1 and 2:1 ratios, for vermicomposting and aerobic composting; performance was assessed in comparison with CD. Vermiconverted-BKCA was then used as organic fertilizer for rice grown in poorly fertile soil. Acidic nature of BKCA feedstocks was neutralized by 30-86% in the vermireactors. Total N and available P concentrations significantly increased in the vermireactors supplemented with considerable mineralization of total organic C. Exorbitantly high K and S contents were pacified to a normal range after vermicomposting. Greater improvement in microbial biomass, respiration, fungal and bacterial growth was observed under vermicomposting against aerobic composting. Consequently, urease and phosphatase activity increased by 1-4 folds in the BKCA based vermibeds. Bioavailability of toxic metals reduced by 41-74% in the vermicomposted BKCAs. High metal accumulation by the earthworms resulted in substantial reduction of pollution load in the finished product. The field experiment demonstrated that vermiconverted-BKCA could be utilized as potential organic fertilizer for rice production, soil fertility rejuvenation, and metal detoxification. Overall, the study reveals that E. fetida could be used as an efficient contender for sanitization of toxic BKCAs.

Remediation of heavy metals and enhancement of fertilizing potential of a sewage sludge by the synergistic interaction of woodlice and earthworms

Woodlice and the earthworm alone or in combination were used to improve physical properties, nutrient release, and heavy metals stabilization during composting of sewage sludge. Chemical properties of raw sludge (IS) were compared to those of composted sludge (CS), sludge + earthworms (VS), sludge + woodlice (WS), and sludge + earthworms + woodlice (VWS) after 50 and 100 days of composting. Physical properties and heavy metals accumulation by the studied fauna was determined after 100 days of composting. Highest proportions of fine particles, porosity and water holding capacity were in the VWS treatment, electrical conductivity, ash content, inorganic N and the total concentrations of P, K, Ca and Mg increased, whereas the pH value, the organic C, C:N ratio and humic acids content decreased in following order: VWS > VC > WS > CS > IS. Total concentrations of Pb, Cd and Ni in composted sludge were lower whereas concentrations of Zn, Cu and Mn were higher than in raw sludge, and woodlice showed higher bioconcentration factor (BCFs) than earthworm for all heavy metals in all treatments. We concluded that woodlice and earthworms synergistically improved the physicochemical properties of the compost and enhanced its potential use as amendment in agricultural soils.

The effects of tetracycline concentrations on tetracycline resistance genes and their bacterial hosts in the gut passages of earthworms (Eisenia fetida) feeding on domestic sludge

Vermi-composting is considered to be a feasible method for reducing tetracycline resistance genes (TRGs) in the sludge. Nevertheless, the way different gut passages of earthworm might affect the fates of TRGs and whether this process is affected by tetracycline (TC) concentrations need to be further investigated. In this study, we examined the effects of TC concentrations on changes in TRGs and bacterial communities in gut passages of earthworm were determined by using quantitative PCR and Illumina high-throughput sequencing. TRGs and intI1 were mainly reduced in the hindgut under the TC concentrations ranging from 0 to 25 mg/kg, while they were enriched under higher TC stress exposure. Consequently, we suggest the TC limitation of 25 mg/kg in the domestic sludge (DS) for vermi-composting. Although the predominant genera were TC sensitive under TC stress, many bacterial hosts harboring multiple TRGs (especially those in the hindgut) should be paid further attention to. In the foregut, five genera with abundant tetracycline-resistant bacteria (TRB) were specialized taxa. Among these genera, Unclassified_Solirubrobacterales and Pirellulaceae were probably related to the digestion processes. Other unclassified taxa related to the TRGs were probably derived from the DS. Five genera with abundant TRB were shared in the gut passages, and three specialized genera in the hindgut. These genera could spread TRGs and intI1 to the environment. These results suggest that vermi-composting is a feasible approach for TRG control in the DS containing TC concentration that does not exceed 25 mg/kg. Fates of TRGs and intI1 widely differ in the gut passages, showing inevitable connections with bacterial communities.

Pre-Composting and Vermicomposting of Pineapple (Ananas Comosus) and Vegetable Waste

In the last few years, pineapple (Ananas comosus) has grown to be considered one of the most important fruits worldwide due to its high production and consumption. However, inadequate disposal of the waste it generates, which represents up to 67% of its total weight, can have environmental impacts. Therefore, this study focuses on the degradation of organic waste produced in the industrialized processing of pineapple waste (rinds, crowns and cores), which undergo a process of vermicomposting at a laboratory level. The methodology used included the pre-composting process and vermicomposting through Californian red worms using mixes tested in three different proportions of pineapple waste (PR) and load material (LM) made up of vegetable waste and eggshells. Testing revealed that the pre-composting process for this waste was feasible as a first stage of the degradation process; the characteristics of the pre-composted material allowed a favorable adaptation for both the worms and general degradation. It also showed efficiencies in the removal of organic carbon between 36.40% and 45.78%. Results also showed the total nitrogen content remained between 1.2% and 2.2% and the carbon/nitrogen relation (C/N) had values under 20 as required for high-quality vermicompost.

Heavy metals distribution and their bioavailability in earthworm assistant sludge treatment wetland

Sludge treatment wetlands (STWs) have been used for sludge treatment in recent years, however, heavy metals (HMs) are one of the limiting factors for the final sludge application, and the fate of HMs in STWs are still not well studied. Therefore, six STWs with two plant species and earthworm addition were investigated to evaluate their effects on HMs distribution and bioavailability. The results showed that plant uptake of HMs was insignificant with earthworm addition. Earthworm had the highest enrichment for Cd with bioaccumulation factors of 6.9-7.3. Moreover, earthworm had a positive effect to remove HMs in accumulated sludge. Meanwhile, the bioavailability of Cd in accumulated sludge was decreased by earthworm addition, with the acid-soluble fraction decreased from range 16.5-22.7% to range 7.2-10.1%. Furthermore, HMs mass balance in the STWs revealed that HMs were widely distributed in the accumulated sludge, leachate and others, while their (except Cd) accumulation in the plants and earthworm are less than 1%. The Cd toxicity in the accumulated sludge can be reduced by the addition of earthworm with enrichment of 3.6-8.2%. Overall, earthworm addition have positive effects on distribution and bioavailability of HMs in STWs.

Biotransformation of bakery industry sludge into valuable product using vermicomposting

The aim of present work was to evaluate periodic changes in bakery industry sludge during vermicomposting. Six different blends of cow dung (CD) and bakery industry sludge (BIS) containing 10 to 50% of BIS were assessed in this study. Changes in physico-chemical parameters were evaluated at 21 days interval up to 105 days. Earthworms significantly increased NPK content and EC, while decreased pH, TOC and C: N ratio of BIS. After vermicomposting, TKN, TAP and TK contents increased 2.0-3.5, 1.2-1.9 and 1.2-1.4 times, respectively as compared to initial blends. A significant reduction (65.4-83.5%) in C: N ratio was observed in all blends. The concentrations of metals were found to be higher in the vermicomposts as compared initial blends. It was inferred that bakery industry sludge spiked with cow dung can be biotransformed into valuable manure employing earthworms.

Sanitary and environmental aspects of sewage sludge management

Currently, sewage sludge management is a huge challenge in the field of environmental engineering. New effective solutions for the treatment of wastewater led to an improvement of the quality of the final effluent but considerably increased the volume of produced sewage sludge, which increases each year. Two points of view conflict regarding the recycling of those “wastes.” Primarily, dehydrated sewage sludge is considered a reservoir of nutrients and organic matter that can be used as a fertilizer in agriculture or as an organic amendment in the remediation of contaminated sites or to build “anthroposoils.” On the other hand, recycled sewage sludge is seen as a potential source of soil contamination by organic and inorganic pollutants and pathogens; potentially toxic elements (such as zinc, copper, cadmium, lead, silver, etc.); polycyclic aromatic hydrocarbons (PAH); polychlorobiphenyls (PCB); biocides and phytopharmaceuticals; pharmaceuticals, personal care products (PPCP), and residuals; synthetic hormones; microplastics; nanotechnology life cycle end products; and microorganisms such as Escherichia coli O157:H7 or Salmonella typhimurium.

This chapter will focus on these aspects, highlighting the health and ecotoxicological risks associated with the presence of such contaminants in sludge. The environmental dangers of sludge spreading on soils will be presented as well as their possible treatment scenarios to propose an acceptable reuse of sewage sludge in a circular economy.

Bioconversion of Scotch broom into a high-quality organic fertiliser: Vermicomposting as a sustainable option

Wild Scotch broom ( Cytisus scoparius (L.) Link) shrubs are widely distributed throughout the world and, in some countries, are considered to be a threat to other plant species. The use of plant biomass from Scotch broom as a fertiliser seems to be the optimum solution for its disposal because it contains considerable amounts of macronutrients. However, its direct application to soils may cause phytotoxicity due to the release of polyphenols, which could negatively affect crop growth. This study evaluated the efficiency of vermicomposting in processing this leguminous plant on an industrial scale. Vermicomposting substantially reduced the biomass of Scotch broom (by 84%), mainly as a result of the loss of volatile solids. Simultaneously, the initial population of earthworms ( Eisenia andrei) increased remarkably throughout the process, offering the possibility of obtaining earthworm protein for animal feed. A nutrient-rich and stabilised peat-like material without polyphenol-associated phytotoxicity was obtained after 42 days of vermicomposting. Lower values of microbial biomass and activity, indicative of stabilised materials, were recorded at the end of the trial. These findings suggest that vermicomposting is an environmentally sound management system for Scotch broom and could easily be scaled up for industrial application.

Bioavailability and bioaccumulation of heavy metals of several soils and sediments (from industrialized urban areas) for Eisenia fetida

Soils and sediments are susceptible to anthropogenic contamination with Metallic Trace Elements (MTEs) and it can present some risks to ecosystems and human health. The levels of Cd, Cu, Fe, Ni, Pb and Zn were assessed in soils (C, G, K, L) from Estarreja (Portugal) and sediments from a stormwater basin in Lyon (DJG), a harbour (LDB) and a Rhône river site (TRS) (France). An ecotoxicological study was performed with Eisenia fetida (E. fetida) to infer about potential transfer risks to the soil invertebrates. To assess risks associated with MTEs contamination, it is important to know their total concentrations, fractionation and the potential available fractions. CaCl₂, DTPA and NaOAc extractions were performed to assess the extractable and available MTEs fractions. The studied sediments were much more contaminated than the soils for all the MTEs analysed. The trace elements fraction linked with DTPA extraction shows higher values when compared with the NaOAc and the CaCl₂ pools. Low mortality effects were recorded in the tests with E. fetida. The MTEs levels in soils and sediments and the concentrations bioaccumulated in adult earthworms contributed to a reduction in the number of juveniles produced. E. fetida adults and juveniles accumulated ETMs as follows: Cd > Cu = Zn > Ni > Pb > Fe. Determined BAFs were mostly lower than 1 with some higher values for Cd, Cu and Zn. Calculated SET and ERITME indexes allowed to classify the samples from the most to the less toxic for E. fetida as: LDB > DJG > L > G > C > K > TRS. Despite this order of toxicity, the earthworms exposed to the sediment TRS presented the lowest reproduction rate. The combination of "chemical" measurements with the calculation of BAFs, but especially SET and ERITME indexes can be a useful tool in risk assessment.

Alleviation of heavy metal phytotoxicity in sewage sludge by vermicomposting with additive urban plant litter

The handling of sewage sludge (SS) and urban plant litter (UPL) has become an important concern. Immobilizing heavy metals (HMs) is regarded as a necessary process for recycling SS in agriculture and forestry. Here, HM removal and HM phytotoxicity in SS during vermicomposting with different additive UPLs was investigated. The results show that vermicomposting with additive UPL significantly reduced the content of HMs, and increased organic carbon content and the proportion of macroaggregates in SS. This process also significantly immobilized HMs by mainly transforming extractable and reducible HMs into residual products. The litters of Dracontomelon duperreanum and Bauhinia purpurea increased oxidizable HMs in SS and the accumulation capacity of HMs of earthworms during vermicomposting. The Cd content in vermicomposts with the B. purpurea litter addition was decreased by 31% relative to the initial SS. Maize in vermicomposts with UPL additions, especially with B. purpurea litter, exhibited significan5tly higher seed germination rates, seedling biomass, root activity, and a lower accumulation of HMs than in SS compost without UPL additions. These results suggest that vermicomposting with additive UPL can alleviate the phytotoxicity of HMs in SS and provides a new method for simultaneously recycling SS and UPL.

Earthworms are associated with subpopulations of Gammaproteobacteria irrespective of the total soil microbiota composition and stability

Soil represents one of the most complex microbial ecosystems on earth. It is well-known that invertebrates such as earthworms have a major impact on transformations of organic material in soil, while their effect on the soil microbiota remains largely unknown. The aim of our work was therefore to investigate the association of earthworms with temporal stability, composition and diversity in two soil microbiota experimental series. We found that earthworms were consistently associated with an increase in subgroups of Gammaproteobacteria, despite major differences in microbiota composition and temporal stability across the experimental series. Our results therefore suggest that earthworms can affect subpopulation dynamics in the soil microbiota, irrespective of the total microbiota composition. If the soil microbiota is comprised of independent microbiota components, this can contribute to our general understanding of the complexity of the soil microbiota.

The existence of fertile hybrids of closely related model earthworm species, Eisenia andrei and E. fetida

Lumbricid earthworms Eisenia andrei (Ea) and E. fetida (Ef) are simultaneous hermaphrodites with reciprocal insemination capable of self-fertilization while the existence of hybridization of these two species was still debatable. During the present investigation fertile hybrids of Ea and Ef were detected. Virgin specimens of Ea and Ef were laboratory crossed (Ea+Ef) and their progeny was doubly identified. 1 -identified by species-specific maternally derived haploid mitochondrial DNA sequences of the COI gene being either 'a' for worms hatched from Ea ova or 'f' for worms hatched from Ef ova. 2 -identified by the diploid maternal/paternal nuclear DNA sequences of 28s rRNA gene being either 'AA' for Ea, 'FF' for Ef, or AF/FA for their hybrids derived either from the 'aA' or 'fF' ova, respectively. Among offspring of Ea+Ef pairs in F1 generation there were mainly aAA and fFF earthworms resulted from the facilitated self-fertilization and some aAF hybrids from aA ova but none fFA hybrids from fF ova. In F2 generation resulting from aAF hybrids mated with aAA a new generations of aAA and aAF hybrids were noticed, while aAF hybrids mated with fFF gave fFF and both aAF and fFA hybrids. Hybrids intercrossed together produced plenty of cocoons but no hatchlings independently whether aAF+aAF or aAF+fFA were mated. These results indicated that Ea and Ef species, easy to maintain in laboratory and commonly used as convenient models in biomedicine and ecotoxicology, may also serve in studies on molecular basis of interspecific barriers and mechanisms of introgression and speciation. Hypothetically, their asymmetrical hybridization can be modified by some external factors.

Protective role of metallothionein during regeneration in Eisenia andrei exposed to cadmium

Lumbricid earthworms are often exposed to simultaneous action of various environmental stressors like soil contamination, temperature fluctuation or predators' attacks, which may induce extrusion of coelomocyte-containing coelomic fluid or loss of tail segments. If the injuries are not lethal, renewal of the immune-competent cells and soluble components of coelomic fluid and/or the regeneration of tail segments occurs. The aim of our investigations was to test the hypothesis that exposure of adult earthworms Eisenia andrei to cadmium-polluted soil at room temperature (RT) and/or low temperature (6°C) have adverse effects on restoration of experimentally depleted coelomocytes or on regeneration of amputated posterior segments. Intact control earthworms and their experimental counterparts subjected to electrostimulation-induced coelomocyte depletion or surgical amputation of posterior segments were maintained either in control soil or in soil spiked with cadmium chloride (500mg/kg air-dried soil) at RT or 6°C. Four weeks after the beginning of experiments, cadmium accumulation in earthworm bodies was significantly lower at 6°C than at room temperature. The numbers of restored cells and fluorophore contents were hardly affected by temperature or cadmium. However, cocoon production was reduced by cadmium and completely abolished at 6°C and regeneration of amputated posterior segments was inhibited in cold but was enhanced by cadmium exposure at RT. Independently on the temperature, the 4-week cadmium exposure of adult earthworms was connected with significantly upregulated expression of Cd-metallothionein (but not of catalase, lysenin and phytochelatin) in coelomocytes.