Advanced thermal hydrolysis: optimization of a novel thermochemical process to aid sewage sludge treatment

Environ Sci Technol. 2012 Jun 5;46(11):6158-66. doi: 10.1021/es204203y. Epub 2012 May 8.

Abstract

The aim of this work was to study in depth the behavior and optimization of a novel process, called advanced thermal hydrolysis (ATH), to determine its utility as a pretreatment (sludge solubilization) or postreatment (organic matter removal) for anaerobic digestion (AD) in the sludge line of wastewater treatment plants (WWTPs). ATH is based on a thermal hydrolysis (TH) process plus hydrogen peroxide (H(2)O(2)) addition and takes advantage of a peroxidation/direct steam injection synergistic effect. On the basis of the response surface methodology (RSM) and a modified Doehlert design, an empirical second-order polynomial model was developed for the total yield of: (a) disintegration degree [DD (%)] (solubilization), (b) filtration constant [F(c) (cm(2)/min)] (dewaterability), and (c) organic matter removal (%). The variables considered were operation time (t), temperature reached after initial heating (T), and oxidant coefficient (n = oxygen(supplied)/oxygen(stoichiometric)). As the model predicts, in the case of the ATH process with high levels of oxidant, it is possible to achieve an organic matter removal of up to 92%, but the conditions required are prohibitive on an industrial scale. ATH operated at optimal conditions (oxygen amount 30% of stoichiometric, 115 °C and 24 min) gave promising results as a pretreatment, with similar solubilization and markedly better dewaterability levels in comparison to those obtained with TH at 170 °C. The empirical validation of the model was satisfactory.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Oxygen Demand Analysis
  • Carbon / analysis
  • Filtration
  • Hydrolysis
  • Organic Chemicals / isolation & purification
  • Sewage / analysis*
  • Solubility
  • Spain
  • Temperature*
  • Water / chemistry
  • Water Purification / methods*

Substances

  • Organic Chemicals
  • Sewage
  • Water
  • Carbon