Chemical characterization of sludge for agricultural purposes

Jarne Casasús, Adrián
Usón Murillo, Asunción (dir.)

Universidad de Zaragoza, EPSHUES, 2014
Ciencias Agrarias y del Medio Natural department, Producción Vegetal area

Graduado en Ingeniería Agroalimentaria y del Medio Rural

Abstract: Sludge.production is increasing worldwide, and one of the main uses of sludge is the use on agricultural land as fertilizer, if they fulfil the legal requirements that limits the use of sludge in agriculture according to its heavy metal content. This study evaluates the main chemical parameters. (Phophorus fraction, Nitrogen, Carbon, CN ratio, pH, Electrical Conductivity, Aluminium, Arsenic, Calcium, Cadmium, Chromium, Copper, Iron, Potassium, Magnesium, Manganese, Sodium, Nickel, Lead, Sulphur, Silicon and Zinc) that allows to know its possible use in agriculture and its dosage. This study is done using sewage sludge samples from 5 different places in Finland and two different manure samples from cow farms in Finland, taking 6 samples per each place and analysing the previously mentioned parameters following the official analysis methods. After that it was carried out an statistical analysis of the data, and using this data a dosage is made according to the legal requirements and the agronomic properties (macronutrient content, NPK). According to the obtained results all sludge samples fulfils the legal requirements to be used in agriculture established in European, Spanish and Finnish legislation. The result show significant differences between chemical characterizations of both products. Regarding sewage sludge samples, the highest differences between each samples are found in phosphorus fractions, that’s varies from place to place, there are also differences in nitrogen content, electrical conductivity, pH, aluminium, calcium, chromium, magnesium, manganese, sodium, iron and sulphur content. In manure the differences between each sample are also found in phosphorus fractionation, pH, nitrogen content, CN ratio, copper, sodium, magnesium and potassium. Copper content is the most limiting factor for agricultural application, due to the limitation established by legislation. Using the maximum amount of sludge that can be legally used according to its copper content, there is enough phosphorus to compensate phosphorus crop requirements, in the other hand there is nitrogen and potassium deficit. Manure is not affected by legislation but its high nickel content could have negative effects in the plant and the soil. 7 The recommended application rate (for a rotation of maize, oilseed rape, hemp and fallow) for those sludge are between 16.000 and 24.000 kg ha-1 of sludge (depending on the copper content and humidity of the sludge sample) every cycle of four years. There would be needed an extra application of mineral fertilizer one year after sludge application and two year after sludge application in the order of 200-250 kg ha-1 of nitrogen and 100 kg ha-1 of potassium.

Free keyword(s): sludge ; chemical characterization ; agriculture
Tipo de Trabajo Académico: Trabajo Fin de Grado

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