Recuperação e caracterização de fósforo por meio das cinzas do lodo de uma ete municipal
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Data
2022-12-01
Autores
Garcia, João Batista Ferraz
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Universidade Estadual Paulista (Unesp)
Resumo
O fósforo é um elemento químico não encontrado pronto para uso na natureza, seu uso pela humanidade é feito após extração de rochas fosfáticas e posterior tratamentos físicos e químicos. Diversos estudos recentes comprovam a iminente possibilidade da sua escassez, assim urge-se a necessidade da reciclagem desse elemento primordial na produção de alimentos através da agricultura, pois o uso de fertilizantes fosfatados nas culturas consome cerca de 90% da produção mundial devido o elemento ser macronutriente essencial para as plantas. Diante dessa problemática o lodo de esgoto aparece como potencial matéria prima para recuperação de fósforo, uma vez que há uma quantidade considerável do elemento na matriz, que em muitos casos o lodo sequer é aproveitado na aplicação auxiliar de fertilização de culturas, sendo depositado em aterros sanitários pelas companhias de saneamento. A falta de interesse na reutilização na agricultura ocorre principalmente pela alta quantidade de patógenos, poluentes orgânicos, microplásticos e possivelmente metais tóxicos, sendo assim, são necessárias formas de tratamento para o aproveitamento do potencial de recuperação de fósforo, sendo uma delas a utilização das cinzas do lodo biológico incinerado/calcinado. Foi obtido nessa pesquisa alta taxa de conversão das frações NAIP (fósforo inorgânico não apatita) em AP (fósforo apatita), mais biodisponíveis às plantas, com uso de aditivo CaO de pureza comercial nos experimentos de calcinação do lodo seco. O teor de pentóxido de fósforo encontrado variou de 12 a 17%, inclusive superando diversas matérias-primas e fertilizantes à base de fósforo. As cinzas também demostraram estar com quantidades de metais tóxicos bem abaixo do preconizado pela legislação ambiental brasileira e internacional, sendo assim ela pode ser aplicada diretamente no solo para a fertilização de culturas ou ser avaliado métodos de extração e separação do conteúdo de P para a produção de fertilizantes.
Phosphorus is a chemical element not found ready for use in nature. Its use by humanity is made possible after extraction from phosphate rocks and subsequent physical and chemical treatments. Several recent studies have shown the imminent possibility of its scarcity. Henceforth it is urgent that we recycle this essential element in food production and in agriculture. Owing to that use of phosphate fertilizers in crops consumes about 90% of world production due to the element being an essential macronutrient for the plants. Faced with this ever-growing problem sewage sludge appears as a potential raw material for phosphorus recovery. There is a considerable amount of the element in the matrix and in many cases the sludge is not even used in the auxiliary application of crop fertilization. Which results in it being deposited in landfills by sanitation companies. The lack of interest of reuse in agriculture is mainly due to the high number of pathogens, organic pollutants, microplastics and possibly toxic metals. Therefore, forms of treatment are necessary to take advantage of the phosphorus recovery potential, one of which is the use of ash of incinerated/calcined biological sludge. In this research a high conversion rate of the NAIP (non-apatite inorganic phosphorus) fractions into AP (apatite phosphorus) which is more bioavailable to plants and was obtained with the use of commercial purity CaO additive in the dry sludge calcination experiments. Phosphorus pentoxide content found ranged from 12 to 17% even surpassing several phosphorus-based raw materials and fertilizers. Ash also showed to have amounts of toxic metals well below those recommended by Brazilian and international environmental legislation. This allows it to be applied directly to the soil for the fertilization of crops or evaluated for methods of extraction and separation of the P content for the production of fertilizers.
Phosphorus is a chemical element not found ready for use in nature. Its use by humanity is made possible after extraction from phosphate rocks and subsequent physical and chemical treatments. Several recent studies have shown the imminent possibility of its scarcity. Henceforth it is urgent that we recycle this essential element in food production and in agriculture. Owing to that use of phosphate fertilizers in crops consumes about 90% of world production due to the element being an essential macronutrient for the plants. Faced with this ever-growing problem sewage sludge appears as a potential raw material for phosphorus recovery. There is a considerable amount of the element in the matrix and in many cases the sludge is not even used in the auxiliary application of crop fertilization. Which results in it being deposited in landfills by sanitation companies. The lack of interest of reuse in agriculture is mainly due to the high number of pathogens, organic pollutants, microplastics and possibly toxic metals. Therefore, forms of treatment are necessary to take advantage of the phosphorus recovery potential, one of which is the use of ash of incinerated/calcined biological sludge. In this research a high conversion rate of the NAIP (non-apatite inorganic phosphorus) fractions into AP (apatite phosphorus) which is more bioavailable to plants and was obtained with the use of commercial purity CaO additive in the dry sludge calcination experiments. Phosphorus pentoxide content found ranged from 12 to 17% even surpassing several phosphorus-based raw materials and fertilizers. Ash also showed to have amounts of toxic metals well below those recommended by Brazilian and international environmental legislation. This allows it to be applied directly to the soil for the fertilization of crops or evaluated for methods of extraction and separation of the P content for the production of fertilizers.
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Palavras-chave
Saneamento, Cinzas lodo de esgoto, Fertilizantes, Compostos de fósforo, Reciclagem de fósforo