THE EFFECT OF AGING ON ELEMENT PLANT AVAILABILITY AND BACTERIAL COUNTS OF MIXTURES OF WOOD ASH AND SEWAGE SLUDGE

Yudani Pousada-Ferradás, Socorro Seoane-Labandeira, Miguel Blanco, Avelino Núñez-Delgado

Abstract


This study investigated the chemical composition of a mixture of 70% wood ashes (a by-productof timber-industry) and 30% sewage sludge (% dry weight), immediately after preparation and afterstorage (42 days). The mixture had higher Mehlich 3 extractable Ca, Mg and K concentrations thaneither component alone, and low plant-available heavy metal concentrations, both immediately aftermixing and after storage for up to 6 weeks. The results support the view that mixtures of this type maybe useful for liming and fertilizing, given their neutralizing capacity and phyto nutrient concentrations.Furthermore, we compared the survival of Escherichia coli in a wood ash and sewage sludge mixture withtheir survival in mixtures of sewage sludge and two levels of quicklime. The time needed to eliminatemost bacteria was 29 days in the ash-sludge combination, while nine days were required for one of thequicklime-sludge mixtures, and counts were minimal for the quicklime-sludge mixture with a pH>12.

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