Biodegradación de desechos de curtiduría y lodo residual por composteo y vermicomposteo

CARDOSO-VIGUEROS, L. & RAMIREZ-CAMPEROS, E. Tannery wastes and sewage sludge biodegradation by composting and vermicomposting process. Hydraulic engineering in Mexico (in Spanish). Vol. XXI, no. 2, AprilJune, 2006, pp. 93-103. The tannery industry generates waste with high concentrations of toxic compounds and organic materials with a slow biodegradation characteristics. This work studies the biodegradation and reduction of contaminants of these wastes with a thermophilic and aerobic process, followed by additional vermicomposting step with Eisenia foetida. The sewage sludge has the following characteristics: 4.1 x 102 MPN/100 mL of Escherichia coli, 3.3 helminth eggs/g. The physicochemical characteristics are for sludge, pH 8.4, electric conductivity 13.88 dSm-1 and high chromium concentration of 3,240 mg/kg. For hair was pH 7.4, electrical conductivity 12.77 dSm-1. The composting piles that had a density (0.5-0.6 ton/m3) obtained better reductions in the volatile solids, (50%). The mixtures had a deficit in the Carbon/Nitrogen ratio and high density, increasing the composting period up to 8 months. The process removed 100% of Escherichia coli and 100% of helminth eggs. The chromium concentration decreased 562 mg/kg. The electric conductivity value decreased to 12.5 dSm-1. The values of nitrogen and phosphorus are similar to organic manure (2.0-3.59% N, 0.12-0.14% P). The percentage of growth of ornamental plants (Schefflera actinophylla and Dracaena sanderiana), with compost and vermicompost was higher than the control (1020%). The tannery solid wastes should not be stored due to its high salinity. They must be treated in order to remove all the contaminants such as chromium, sulfur and pathogens. The organic matter must be stabilized with a biological process like composting and vermicomposting for landfill disposal or greenhouse use.