Abstract

The present study aimed to assess the anaerobic digestion of sewage from cellulose industry mixed with doses of glycerin, in order to produce biofertilizer and biogas, for agriculture and energy purposes. Five anaerobic reactors were developed, which were fed with effluent and doses of glycerin (0, 5, 10, 15 and 20% v v^-1) and evaluated during the hydraulic retention time of 42 days. The physical and chemical parameters were evaluated every seven days: temperature; pH; turbidity; series of solids; total phosphorus (P_total); Kjeldahl nitrogen (N_total) and COD; as well as the levels of K, Ca, Mg, Cu, Zn, Fe, Mn and Cd, Pb and Cr; biogas production was evaluated daily. The anaerobic treatment produced biofertilizer with excellent nutritional conditions, with adequate levels of P, K, Ca, Mg, Mn, Fe and Zn. The addition of glycerin increased biogas production, with 15% and 5% of glycerin, respectively producing 0.54 and 0.40 mL L^-1 d^-1. The treatments of 15% and 5% of v v^-1 glycerin also exhibited greater removal of COD. However, the low levels of N have caused problems in the anaerobic process. Anaerobic digestion of the cellulose industry effluent with 5 and 15% of glycerin (v v^-1) provided increase in biogas production of 0.54 and 0.40 mL L^-1 d^-1, respectively. K, Ca, Mg, Zn, Fe and Mn at the final biodigestion remained with excellent levels for use in crops as biofertilizer.

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