Sewage sludge is reported to have a high nutrient content suitable for use as a fertilizer
additive however the substantial metal loading poses major constraints for its practical
use. Under this context, an effort was made to understand the effectiveness of
vermicomposting in possibly solving the issue of metal leaching from sewage sludge to
the water resources, if used as fertilizer supplements. For this purpose, sludge was
collected from a wastewater treatment plant and vermicomposting was applied for
selected duration of 15, 30, 45, 60 and 75 days. Various physicochemical parameters
before and after different duration of vermiconversion were evaluated. A temporal
variation in both total and water soluble fractions of copper and zinc were observed and
correlated with a change in pH. In addition, a biosorption test was done by using
monometallic solution and the results were interpreted to justify the objectives. The
results showed that 1:1 (sludge + cowdung) was more effective at reducing the Zn
concentration than 1:2 treatments while Cu reduction was not uniform. Biosorption tests
revealed the importance of pH in an effective adsorption. Dependence of pH on water
soluble fraction was not significant. Lower metal content of sewage sludge with respect to
various guidelines, % metal removal due to vermicomposting, high nutrient content, 1:1
treatment showing better metal removal and stabilization duration of just 75 days of
composting substantiate the possible use of sewage sludge amended cow manure as an
agricultural additive.
Sewage sludge is reported to have a high nutrient content suitable for use as a fertilizeradditive however the substantial metal loading poses major constraints for its practicaluse. Under this context, an effort was made to understand the effectiveness ofvermicomposting in possibly solving the issue of metal leaching from sewage sludge tothe water resources, if used as fertilizer supplements. For this purpose, sludge wascollected from a wastewater treatment plant and vermicomposting was applied forselected duration of 15, 30, 45, 60 and 75 days. Various physicochemical parametersbefore and after different duration of vermiconversion were evaluated. A temporalvariation in both total and water soluble fractions of copper and zinc were observed andcorrelated with a change in pH. In addition, a biosorption test was done by usingmonometallic solution and the results were interpreted to justify the objectives. Theresults showed that 1:1 (sludge + cowdung) was more effective at reducing the Znconcentration than 1:2 treatments while Cu reduction was not uniform. Biosorption testsrevealed the importance of pH in an effective adsorption. Dependence of pH on watersoluble fraction was not significant. Lower metal content of sewage sludge with respect tovarious guidelines, % metal removal due to vermicomposting, high nutrient content, 1:1treatment showing better metal removal and stabilization duration of just 75 days ofcomposting substantiate the possible use of sewage sludge amended cow manure as an
agricultural additive.
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