Sorção de fósforo de efluente doméstico tratado em lodo de ETA e aplicação do resíduo em solo cultivado com milho

Abstract

Although Brazil has presented advances in sanitation actions in recent years, it is a common practice for sanitation companies in the country to launch systemic waste from water treatment or sewage operations in springs near the generating sources. There are several environmental consequences due to the excessive levels of nutrients in these rich residues, such as phosphorus (P) and nitrogen (N). Eutrophication is notably one of the major consequences of the release of nutrient rich waste. Although it is one of the primary elements responsible for stimulating the overgrowth of algae in aquatic environments, P is indispensable to life and its sources are under imminent risk of scarcity. In this context, sewage sludge produced from wastewater treatment plants appears as a possible environmental ally, and it can minimize both eutrophication and the imminent risk of a shortage of phosphate sources. Sewage sludge is a residue rich in oxy-hydroxides of Al and Fe, which favor the adsorption mechanisms of P present in treated sewage effluents. In addition, there is the prospect of using the by-product resulting from the adsorption process as an agricultural biofertilizer. The objective of this study was to compare the uptake of P by maize crop (Zea mays) submitted to conventional soil treatment with P uptake by the crop submitted to two different hybrid treatments, which included: F1 treatment (fertilization with NPK); F2 treatment (fertilization with N, K, 50% of P and 50% of sewage sludge) and F3 treatment (fertilization with N, K and sewage sludge). The sludge samples used in the treatments F2 and F3 were previously used as a filter material in an up flow reactor in the tertiary treatment of the wastewater treatment plant of UFLA; The removal of P from the sludge occurred in the three tests. In the R1 test, the removal was total in 50% of the samples and partial in the others, whereas in the R2 and R3 tests, the removal was total in 100% of the samples. The macro and micronutrient leaf concentrations observed in the maize crop were satisfactory, when compared with other literature. Regarding the uptake of P, the results showed that the highest leaf concentration observed was F1: 1.86 g kg -1 , followed by treatments F2 and F3, which presented a contribution of 1.20 g kg -1 and 0.99 g kg -1 of P, respectively. It was also observed that the reuse of the sludge in the applied doses was enough for the analyzed plant material to reach considerable levels of lead (Pb), which should be monitored when the residue is used in the agricultural cultivation.