A Fenton-like process for the enhanced activated sludge dewatering

The presence of high moisture content in sewage sludge aggravates the disposal costs and restricts its application. Sewage sludge is traditionally conditioned by dosing organic/inorganic chemicals. However, after the treatment, the moisture content and inorganic solid mass remain to be a high level. In this work, a Fenton-like dewatering process, i.e., a combination of sulfuric acid, hydrogen peroxide and ferric sulfate, was developed. Uniform design was used to optimize the composite conditions, and the effects of Fenton-like treatment on sludge dewatering were examined. The results show that, after the treatment of the Fenton-like reaction, the moisture content of sludge cake and the dry solid mass decreased from 80.0% to 66.1% and from 12.9 to 10.6 g/L, respectively. The mechanism for the enhanced dewatering performance was explored, and the degradation of abundant extracellular polymeric substances, the lysis of the sludge cells, and the release of bound water and typical metals within the sludge flocs were found to be mainly responsible for the enhanced dewatering performance. In addition, a surface thermodynamic analysis with the extended DLVO theory shows that the higher hydrophobicity and the less stable sludge flocs also contributed to the decrease in moisture content. Our results confirm that such a Fenton-like treatment exhibited excellent performance in enhancing sludge dewatering and metal leaching and is a promising pretreatment approach for sludge disposal. (C) 2015 Elsevier B.V. All rights reserved.