18 Mar Fermentative Substrates in Aerobic Granular Sludge
A. Elahinik
Industrial wastewaters often have unique properties and contain impurities that pose a significant challenge to their treatment. Lab-scale experiments were performed to provide answers on the feasibility of aerobic granular sludge (AGS) technology for the treatment of organically polluted industrial wastewater.
Glycerol is found in a variety of industrial effluents such as biodiesel and epoxy resin production facilities. However, little is known about the conversion and the impact of glycerol on AGS processes. Chapter 2 describes glycerol conversion in AGS capable of enhanced biological phosphorus removal (EBPR). Robust granules with good phosphorus removal capabilities were formed in an AGS sequencing batch reactor fed with glycerol as the sole carbon source. The interaction between the fermentative conversion of glycerol and product uptake by polyphosphate accumulating organisms (PAO) was studied using stoichiometric and microbial community analysis. The analysis of the biomass identified a community dominated by Actinobacteria (Tessaracoccus and Micropruina) and a typical PAO known as Ca. Accumulibacter. Glycerol uptake facilitator (glpF) and glycerol kinase (glpK), two proteins involved in the transport of glycerol into the cellular metabolism, were only observed in the genome of the Actinobacteria. The anaerobic conversion appeared to be a combination of substrate fermentation and product uptake-type reaction. Initially, glycerol fermentation led mainly to the production of 1,3-propanediol (1,3-PDO) which was not taken up under anaerobic conditions. Despite the aerobic conversion of 1,3-PDO, stable granulation was observed. Over time, 1,3-PDO production decreased and complete anaerobic COD uptake was observed. Overall, the results demonstrate that glycerol-containing effluents can effectively be treated by the AGS process via a collaboration between fermentative and polyphosphate accumulating organisms.
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