Anaerobic digestion of excess activated sludge with ozone pretreatment

Abstract

Source minimization of excess sludge production by economical means can be considered an attractive option to deal with the problem of sludge disposal under strict disposal standards. In this paper long-term operational results for a process that combines the oxidative ozone pretreatment with anaerobic sludge digestion are described. The ozone pretreatment solubilized around 19% and 37% of the solids at 0.015 and 0.05 gO3/gTS ozone dose. The solubilization ratios during ozonation did not show any significant difference for the sludge concentrations ranging from 1.8-2.6%. The TVS concentrations after ozone treatment were observed to be about 3% lower than the feed sludge concentrations suggesting only partial mineralization during ozonation. The ozone pretreatment resulted in improved solid reduction efficiencies during anaerobic digestion leading to higher methane recovery. The TVS removal efficiencies during anaerobic digestion were observed to increase by a maximum of 35-90% depending on the applied ozone dose during ozone pretreatment. The improvement in TVS degradation efficiency at different applied ozone doses correlated well with the extent of solubilization during ozonation. Long-term data also suggested that biomass acclimation to ozonated sludge was necessary before higher degradation efficiencies could be achieved.

Effect of Ozonation and Sonication on Biochemical Methane Potential of Biosludge from Textile Mill Effluent

“…The increase of biodegradability with increasing ozone dosage was in accordance with the finding of Goel et al (2003) and Bougrier et al (2006). They found that CH 4 formation increased with increasing ozone dosage.…”

“…The anaerobic digestion has many advantages compare with other methods, namely (1) a relatively low cost, (2) consumes little energy and nutrition, and (3) anaerobic bacteria ability to transform almost all organic substances into methane (Heredia and Garcia 2005). Goel et al (2003) suggested that the anaerobic process was the most important method to reduce the amount of biosludge in the wastewater treatment system. Various researches on anaerobic process were currently focused on different techniques to increase biosludge biodegradability and hydrolisis through pretreatment (Dohanyos et al 2000;Goel et al 2003;Lissens et al 2004;Heredia and Garcia 2005;Bougrier et al 2006).…”

Interpreting the synergistic effect in combined ultrasonication–ozonation sewage sludge pre-treatment

“…In addition, ozone is able to convert refractory organic matters into biodegradable form (Volk et al, 1993;Nishijima et al, 2003). Most importantly sludge biodegradability is reported to be remarkably improved after ozonation (Weemaes et al, 2000;Goel et al, 2003).…”

Holistic sludge management through ozonation: A critical review

“…Several studies have shown that 5-26% of TS can be mineralised at ozone dosages of 18-50 mg O 3 /g TSS (Chu et al, 2009b;Goel et al, 2003). Included in this mineralized fraction are the inert or non-biodegradable solids .…”