Bioremediation of aerobically treated distillery sludge mixed with cow dung by using an epigeic earthworm Eisenia fetida

Abstract

The potential of the epigeic earthworm Eisenia fetida to stabilize sludge (generated from a distillation unit of the sugar industry) mixed with cow dung, in different proportions i.e. 20% (T 1 ), 40% (T 2 ), 60% (T 3 ) and 80% (T 4 ) has been studied under laboratory conditions for 90 days. The ready vermicompost was evaluated for its' different physico-chemical parameters using standard methods. At the end of experiment, all vermibeds expressed a significant decrease in pH (7.8-19.2%) organic C (8.5-25.8%) content, and an increase in total N (130.4-170.7%), available P (22.2-120.8%), exchangeable K (104.9-159.5%), exchangeable Ca (49.1-118.1%), and exchangeable Mg (13.6-51.2%) content. Overall, earthworms could maximize decomposition and mineralization efficiency in bedding with lower proportions of distillery sludge. DTPA extractable metal reduction in substrate was recorded between the ranges of 12.5-38.8% for Zn, 5.9-30.4% for Fe, 4.7-38.2% for Mn and 4.5-42.1% for Cu. Maximum values for the mean individual live weight (809.69 ± 20.09 mg) and maximum individual growth rate (mg wt. worm )1 day )1 ) (5.81 ± 0.18) of earthworms was noted in T 1 treatment, whereas cocoon numbers (69.0 ± 7.94) and individual reproduction rate (cocoon worm )1 day )1 ) (0.046 ± 0.002) was highest in T 2 treatment. Earthworm mortality tended to increase with increasing proportion of distillery sludge, and maximum mortality in E. fetida was recorded for the T 4 (45.0 ± 5.0) treatment. Results indicate that vermicomposting might be useful for managing the energy and nutrient rich distillery sludge on a low-input basis. Products of this process can be used for sustainable land restoration practices. The feasibility of worms to mitigate the toxicity of metals also reduces the possibility of soil contamination, which has been reported in earlier studies during direct field application of industrial wastes.

The influence of earthworms on nutrient dynamics during the process of vermicomposting

“…N mineralisation is regulated by the availability of DON and NH 4 + , the activity of microorganisms and their relative requirements for C and N (Bardgett, 2005). Accordingly, previous studies have also shown a higher content of total K in the presence of earthworms in vermicomposting trials performed with either sewage sludge or cattle manure (Suthar, 2008;Garg, 2009, 2011). The total K content increased significantly with earthworm activity (F 1,16 = 444.06, P < 0.0001), and its content was dependent on the type of waste (F 1,16 = 15.96, P < 0.01) being up to 2.5 times higher in the cattle manure than in the sewage sludge (Table 2).…”

The potential reuse of soybean husk as feedstock of Eudrilus eugeniae in vermicomposting

“…When organic matter passes through the gut of earthworm, some phosphorous is converted to a more available form. The release of phosphorous in an available form is performed partly by earthworm gut phosphatase and further release of phosphorus might be attributed to the phosphorus solubilising microorganisms present in worm casts 47. Also, the gut of the earthworm usually produces a considerable amount of alkaline phosphatase, which is an essential enzyme excreted through cast deposition and involved in biogeochemical cycle of phosphorus in soils 48…”

Industrial wastes and sludges management by vermicomposting

“…Haimi and Hutha (1986) have reported that lower pH in vermicomposts might be due to the production of CO 2 and other organic acids by microbial activity during bioconversion of wastes substrates. Suthar (2008) has reported that the shift in pH could be due to microbial decomposition during the process of vermicomposting. Elvira et al (1998) have concluded that production of CO 2 and organic acids by microbial decomposition during vermicomposting lowers the pH of substrate.…”

“…Earthworm biomass production and reproduction performance was excellent in bedding which contained lower proportions of distillery sludge (20-40%). Suthar (2008) also reported the vermicomposting of aerobically treated distillery sludge mixed with cow dung in different proportions (20-80%) under laboratory conditions using Eisenia fetida. At the end of experiment, final product produced from all vermibeds showed a decrease in pH (7.8-19.2%), organic C (8.5-25.8%) content, and an increase in total N (130.4-170.7%), available P (22.2-120.8%), exchangeable K (104.9-159.5%), exchangeable Ca (49.1-118.1%), and exchangeable Mg (13.6-51.2%) content (Table 3).…”