DISTRIBUIÇÃO DE ESPÉCIES METÁLICAS NA FRAÇÃO SÓLIDO-LÍQUIDO DE EFLUENTE DA SUINOCULTURA SUBMETIDO A BIODIGESTÃO ANAERÓBIA

Abstract

The industrial swine production is characterized by the significant amounts of effluent generation, when not managed properly can cause many environmental problems. The anaerobic biodigestion process is presented as an important and low cost treatment step for reduction of organic matter. The impact of anaerobic biodigestion on the bioavailability of cooper and zinc in swine manure was evaluated by sequential chemical speciation scheme, applying in raw and digested manure. In this study, was used the method proposed by the Community Bureau of Reference (BCR), plus two fractions, dividing the metals in: water soluble (step 1), exchangeable (step 2), reducible (step 3), oxidizable (step 4) and residual (step 5). The aim of this study was investigate the influence of feed organic load in biodigester capacity of organic matter degradation, biogas production, biogas quality and its influence on the metals distribution in swine wastewater, through the load organic progression to 0.5 (phase 1), 1.0 (phase 2) and 1.5 (phase 3) KgVS.m-3 respectively. The use of original and modified BCR method for speciation of metals in swine effluent were also studied. The evaluated biodigestion process was effective for swine wastewater treatment, achieving good efficiency to removed volatile solids in all stages of organic load progression (phase 1: 61.38%, phase 2: 55.18%, phase 3: 43.18%). The biogas production showed direct relationship with the increasing of organic load, reaching 0.14, 0.85 and 0.87 Nm³.KgVSadd, without any significant difference (p<0.05) in the percentage of methane in biogas, begin 73.72, 75.00 and 77.92 %, respectively in phases 1, 2 and 3. The cooper concentration in the swine effluent in digested manure for three phases (0.930, 0.759 and 1.070 mg Cu.g?¹) were lower than permitted by Brazilian legislation, 1.5 mgCu.g?¹.( CONAMA Resolution 375) to use as agricultural fertilizer. As for the zinc concentration during the three phases (6.578, 5.658 and 7.547 mgZn.g?¹) were higher than those permitted (2.8 mgCu.g?¹). The phases of load organic progression caused changes in the Cu and Zn distribution on different fractions in swine manure. There were a decrease of metals contained in most bioavailable fractions (steps 1, 2 and 3) and increasing in more environmental stable fraction (step 4), during phases 1 and 2. During phase 3, were observed few alterations in metals distributions. Use of modified BCR method showed no advantages over the original BCR by cooper and zinc speciation in swine manure.