Evolution of organic matter and nitrogen during co-composting of olive mill wastewater with solid organic wastes |
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Authors: | C Paredes A Roig M P Bernal M A Sánchez-Monedero J Cegarra |
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Institution: | (1) Department of Soil and Water Conservation and Organic Waste Management, Centro de Edafología y Biología Aplicada del Segura, CSIC, PO Box 4195, 30080 Murcia, Spain e-mail: pbernal@natura.cebas.csis.es Tel.: +34-68-215717, Fax +34-68-266613, ES |
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Abstract: | Four olive mill wastewater (OMW) composts, prepared with three N-rich organic wastes and two different bulking agents, were
studied in a pilot plant using the Rutgers system. Organic matter (OM) losses during composting followed a first-order kinetic
equation in all the piles, the slowest being the OM mineralisation rate in the pile using maize straw (MS). The highest N
losses through NH3 volatilisation occurred in the mixtures which had a low initial C/N ratio and high pH values during the process. Such losses
were reduced considerably when MS was used as the bulking agent instead of cotton waste (CW). N fixation activity increased
during the bio-oxidative phase before falling during maturation. This N fixation capacity was higher in piles with a lower
NH4
+-N concentration. Only the composts prepared with OMW, CW and poultry manure or sewage sludge reached water-soluble organic
C (CW) and NH4
+-N concentrations and CW/Norg and NH4
+/NO3
– ratios within the established limits which indicate a good degree of compost maturity. Increases in the cation-exchange capacity,
the percentage of humic acid-like C and the polymerisation ratio revealed that the OM had been humified during composting.
The germination index indicated the reduction of phytotoxicity during composting.
Received: 14 June 1999 |
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Keywords: | Olive mill wastewater Composting Organic matter degradation Nitrogen fractions Humification |
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