Anaerobic co-digestion of industrial waste landfill leachate and glycerin in a continuous anaerobic bioreactor with a fixed-structured bed (ABFSB): Effects of volumetric organic loading rate and alkaline supplementation

Abstract

Anaerobic co-digestion from industrial waste landfill (IWL) leachate and glycerin was evaluated in a continuous anaerobic bioreactor with fixed-structured bed (ABFSB) under mesophilic conditions (30 ± 1 °C). The ABFSB reactor had a useful volume of 4.77 L. The support medium consisted of polyurethane (PU) foam arranged in an orderly manner. The substrate used corresponded to a mixture of 95% IWL leachate and 5% glycerin (v/v) and the inoculum consisted of flocculent anaerobic sludge. The ABFSB reactor was operated in two phases – the 1st phase (between the 49th and the 439th days of operation): started after the inoculum adaptation and the effect of the increase in the organic loading rate (OLR) was evaluated (2; 3.5; 7.1 and 11.6 gCOD L−1 d−1); the 2nd phase (between the 440th and 471st days of operation): the effect of the reduction in alkalinity supplementation via sodium bicarbonate (NaHCO3) was evaluated (0.56; 0.42; 0.28; 0.14 gNaHCO3 gCODinfluent−1 and non-supplementation). The OLR of 7.1 gCOD L−1 d−1 was the condition that presented the best results in the 1st phase for the parameters: maximum methane flow rate (MFR) (7.61 LNCH4 d−1), methane yield (MY) (0.30 LNCH4 gCODremoved−1), volumetric methane production rate (VMPR) (2.79 LNCH4 L−1 d−1), COD removal efficiencies (ERTCOD) and soluble COD (ERSCOD) higher than 90%. In the 2nd phase, the reactor was operated with an OLR of 7.1 gCOD L−1 d−1 and a hydraulic retention time (HRT) of 35.22 h and CODinfluent of 10.68 g L−1. The minimum alkalinity supplementation required was 0.28 gNaHCO3gCODinfluent−1, a condition in which the reactor showed stability and satisfactory performance for the parameters: MFR (9.48 LNCH4 d−1), MY (0.33 LNCH4 gCODremoved−1) and VMPR (3.18 LNCH4 L−1 d−1). It was concluded that the ABFSB reactor proved to be stable in the IWL leachate co-digestion and glycerin, when the alkalinity supplementation, effectively necessary, was met.