Odor Generation from Anaerobic Sludge: Role of Iron & Aluminum

This study was conducted to determine the effect of iron and aluminum on odor generation from anaerobically digested and dewatered sludge cakes. Blended primary and waste activated sludge samples obtained from 12 different wastewater utilities was batch digested in the laboratory for 30 days at 37°C, conditioned, dewatered and the organic sulfur odor generation potential measured. In addition to sulfur gas analysis, all sludge samples were analyzed for total and volatile solids, Fe and Al concentrations in thesolids, mono and divalent cations in solution and soluble biopolymer(proteins and polysaccharides). A correlation between iron and peak organic sulfur gas concentrationsin the headspace of incubation vials was found. Following anaerobic digestion, a significant increase in solution protein occurred and correlations between solution protein, ammonium production, percentile volatile solids reduction and iron content in sludge were observed. These data suggested that iron plays an important role in anaerobic digestion and in odor generation from dewateredsludge cake. Aluminum reduced the odor potential for sludges that were high in iron, suggesting that proteins associated with aluminum are resistant to degradation following shear.