Odor Generation from Anaerobic Sludge: Role of Iron & Aluminum

Abstract

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 o 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 the solids, mono and divalent cations in solution and soluble biopolymer (proteins and polysaccharides). A correlation between iron and peak organic sulfur gas concentrations in 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 dewatered sludge 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.

Role of Protein, Amino Acids, and Enzyme Activity on Odor Production from Anaerobically Digested and Dewatered Biosolids

“…The results also appeared to show that the protein was degraded slower when iron was added. These results are in contrast to Verma et al (2006) , who reported that higher concentrations of iron in the feed to the digesters were correlated to greater peak total VOSC concentrations. Additional research is needed to fully investigate the potential of iron addition to reduce odorant production.…”

The effect of iron and aluminium for phosphorus removal on anaerobic digestion and organic sulfur generation

“…However, as indicated in the recent WERF III odor study (Adams et al 2007), addition of aluminium during centrifugal dewatering for sludge conditioning resulted in much lower odor generation from the dewatered sludge cakes. doi: 10.2166/wst.2010.300 The importance of this is that when iron or aluminium salts are added for phosphorus removal in the activated sludge system, they can also influence both the efficiency of anaerobic digestion and also the odors that are generated from the dewatered sludge (Verma et al 2006;Adams et al 2007). Therefore, this study was undertaken to better understand the effects of iron and aluminium salts added to activated sludge for phosphorus removal on anaerobic digestion and odor generation potential.…”