Sabrina Zanaboni

Wet oxidation of sewage sludge from municipal and industrial WWTPs

AbstractIn the last years, sewage sludge management turned out to be a topic of great interest due to the increasing sludge production and the high cost of sludge treatment and disposal. In this context, several methods are being studied for sewage sludge minimization: among them, wet oxidation (WO) was proposed as an effective hydrothermal oxidation based technology. The aim of this work, carried out within the European project “ROUTES,” was the assessment of the influence of sludge composition on process performance: for this purpose, seven different types of sewage sludge were submitted to WO tests at lab scale. Moreover, each operating condition (temperature, reaction time, and initial oxygen pressure) was varied so as to highlight the effect of process parameters on oxidation efficiency; this was essentially evaluated in terms of chemical oxygen demand (COD), volatile suspended solid (VSS) and total suspended solid (TSS) reduction. COD and VSS abatement varied in the ranges 44–85%, 71–99% depending o...

Sewage sludge minimisation by means of wet oxidation: process performance and economic sustainability

Today, several technologies and management strategies are proposed and applied in WWTPs to minimise sludge production and contamination and their techno-economic feasibility has to be carefully evaluated. In this work (which is being conducted within the European Union project ‘ROUTES’), based on bench results, a mass balance was drawn for a WWTP (500,000 PE), where it was supposed to install a wet oxidation (WO) stage for sludge minimisation. The design of treatment units and the estimation of capital and operation costs were then performed. Subsequently, a procedure for technical-economic assessment was developed. Basically, this procedure consists in the definition and ranking of several technical (e.g., reliability of the technology, complexity and integration with the existing facilities, amount of residues to be disposed of or recovered, etc.) and economic aspects. Preliminary results have shown WO to be a suitable solution for sludge minimisation.