Management of Secondary Sewage Sludge by Vermicomposting for Use as Soil Amendment
Shobha Ananda Reddy, S. Akila and Radha D. Kale | 2012
Laboratory study was carried out for efficient management of sewage sludge generated by municipal wastewater treatment plant. The experiment dealt with the stabilisation, through the action of epigeic earthworm, Eudrilus eugeniae, of mixtures containing sewage sludge, Eichhornia crassipies and Parthenium hysterophorus. Chemical analyses of secondary sewage sludge (collected from Hebbal treatment plant, Bangalore) were carried out to estimate the change in composition of various chemicals in sludge before and after vermicomposting. Combined effect of vermicomposting and addition of P. hysterophorus and E. crassipes resulted in conversion of sludge into a useful soil amendment in place of fertilizers to enhance the soil quality and increase the plant growth. A reduction in pH value is achieved after vermicomposting in all the three substrates used in the study. The study shows a significant increase in levels of Phosphorus in all the vermicomposted samples with highest of 0.34% by weight in the sample Sludge + P. hysterophorus while the value in plain sludge is only 0.17% by weight. This increased value promoted rapid and better germination in the germination studies carried out using Lycopersicon esculentum seeds.Effectiveness of vermicomposted samples as effective soil amendments was assessed through studies using tomato seeds. Aqueous vermicompost extracts of above material were used for this assessment. The results clearly indicated a maximum rate of 80% germination in case of sludge + P. hysterophorus and water samples while the least germination rate was observed in plain sludge sample. Subsequently the biomass value was maximum of 1.00g in case of the substrate sludge + P. hysterophorus.Serial dilution was carried out for the total microbial count, which was found to be nearly two-fold higher in vermicomposted sludge with E. crassipes and P.hysterophorus samples than in plain sludge, E.coli was absent in all the vermicomposted substrates.