Development of technological alternatives for the use of ETA sludge as raw material for the production of controlled release fertilizers

Abstract

The characteristics of sludge from water treatment plants - ETAs - make their destination a challenge. The variability of composition, the low organic matter content and, mainly, the high content of aluminum salts limit considerably its application in agricultural soils, a solution already studied for sewage treatment plant sludge (STP). However, its mineral structure could, in principle, be the basis for the production of pellets that would act as soil conditioners or as adjuvants for controlled fertilizer release systems, thus enabling an alternative of high consumption in residue volume. Thus, technological routes that would immobilize the aluminum salts in non-soluble structures could, together with formulation technologies, enable conditions of agricultural use of this residue. Therefore, it is proposed to develop, from ETAs sludge representative of SABESP's production, a route for the production of zeolitic concentrates from reactions with KOH, which can be formulated as extruded fertilizer granules using starch plasticized with urea and thus composing a slow-release NK fertilizer. To avoid subsequent effects of immobilization precipitation of phostats (P), essential fertilizer applied concomitantly to NK, and to ensure better functionality of the product, it is proposed to adapt the formulation for joint transmission of acidulant microorganisms, particularly isolated with confirmed agronomic potential for the control of biological soil pathogens such as Fusarium oxysporum f. sp. Cubense and Sclerotium rolfsii. Standardized tests in laboratory, green house and field will be performed to evaluate the agronomic efficiency of fertilizers and the action of bioagent microorganisms. Thus, it is expected that the integration of different strategies will provide greater agronomic efficiency and competitiveness to the reuse of these residues and optimize the use of bioagent microorganisms in agriculture. (AU)