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Management of sewage sludge by composting using fermented water hyacinth

Tello-Andrade, A. F., Jiménez-Moleón, M. C., Sánchez-Galván, G.
Environmental science and pollution research international 2015 v.22 no.19 pp. 14781-14792
Eichhornia crassipes, Paecilomyces, Penicillium, Rhizopus, Salmonella, United States Environmental Protection Agency, arsenic, cadmium, carbon, carbon nitrogen ratio, cation exchange capacity, chromium, coliform bacteria, composting, composts, copper, electrical conductivity, fungi, germination, heavy metals, lead, mercury, nickel, nitrogen content, nutrients, organic matter, particle size, pathogens, sewage sludge, temperature, thermophilic microorganisms, volatile fatty acids, zinc
The goal of the present research work was to assess the management of sewage sludge (SS) by composting using fermented water hyacinth (WHfₑᵣₘ) as an amendment. The water hyacinth was fermented, and a higher production of volatile fatty acids (VFAs) (782.67 mg L⁻¹) and soluble organic carbon (CSOL) (4788.34 mg L⁻¹) was obtained using a particle size of 7 mm compared to 50 mm. For composting, four treatments (10 kg fresh weight each) were evaluated: treatment A (100 % SS + 0 % WHfₑᵣₘ), treatment B (75 % SS + 25 % WHfₑᵣₘ), treatment C (50 % SS + 50 % WHfₑᵣₘ), and treatment D (25 % SS + 75 % WHfₑᵣₘ). The WHfₑᵣₘ added to SS, especially in treatments C (50 %) and D (75 %), increased the initial contents of organic matter (OM), organic carbon (CORG), CSOL, the C/N ratio, and the germination index (GI). The heavy metal content (HMC) (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) at the beginning was below the maximum allowed by USEPA regulations. All of the samples were free of Salmonella sp. from the beginning. The reduction of the CORG, CSOL, total Kjeldahl nitrogen (TKN), and C/N ratio indicated the degradation of the OM by day 198. The treatments with WHfₑᵣₘ (B, C, and D) yielded higher values of electrical conductivity, cation exchange capacity, and GI than SS at day 198. No significant differences were observed in GI among the treatments with WHfₑᵣₘ. The fecal coliforms were eliminated (<3 MPN g⁻¹) and the helminths were reduced to ≤5 eggs/2 g during the process. The competition for nutrients and the presence of suppressive fungi of the genera Penicillium, Rhizopus, Paecilomyces (penicillin producers), and Fusariella isolated from the compost may have promoted the elimination of pathogens since no thermophile temperatures were obtained. WHfₑᵣₘ as an amendment in the composting of SS improved the characteristics of the final product, especially when it was used in proportions of 25 and 50 %. An excellent product was obtained in terms of HMC, and the product was B class in terms of pathogens.