Biomethanation and anaerobic co-digestion via microbial communities of microalgal Hydrodictyon reticulatum biomass residues with sewage sludge

Abstract

The performance of co-digestion via the combination of microalgae residues and wasted activated sludge (WAS) was evaluated in batch and semi-continuous type anaerobic digestion (AD) reactors. Simultaneously, AD with WAS alone (R-1) and with the combination of raw microalgae and WAS (R-2) were conducted, respectively. In batch tests, compared with R1 (344 mL-CH4/g-VS), co-digestion of WAS with microalgae residues (R-3) achieved 40% higher methane yield (498 mL-CH4/g-VS), while R-2 exhibited the lowest value of 148 mL-CH4/g-VS. The semi-continuous type R-3 digester reduced higher volatile solids (VS; 39%) at an organic loading rate of 1.0 kg-VS/m(3)d, producing the methane yield of 292 mL/g-VSd. The R-3 semi-continuous type digester had the highest concentrations of both total bacteria and archaea, showing a ratio of 1: 1 among hydrogenotrophic and acetoclastic methanogens. The bacterial community was characterized as existence of the Lactobacillus genus as well as fermentative bacteria belonging to the Clostridia class syntrophically associated with hydrogenotrophic methanogens.