Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems

Anaerobic digestion (AD) technology is commonly used to treat sewage sludge from activated systems, meanwhile alleviating the energy demand (and costs) for wastewater treatment. Most often, anaerobic run in single-stage systems under mesophilic conditions, as this temperature regime considered be more stable than thermophilic one. However, it known that conditions are advantageous over ones terms of methane production and digestate hygienisation, while unclear which one better concerning dewaterability. Temperature-phased (TPAD) a double-stage AD process combines above-mentioned regimes, by operating digester followed The aim study compare quality TPAD dewaterability, pathogenic safety lower calorific value (LCV) and, based on comparison, consider digested final disposal alternatives. research conducted lab-scale reactors treating waste-activated sludge. dewaterability tested two methods, namely, centrifugation mechanical pressing. experimental results show system most beneficial organic matter degradation efficiency (32.4% against 27.2 TAD 26.0 MAD), producing with high (8.1–9.8% worse 6.2–12.0% MAD) (coliforms Escherichia coli were not detected, Clostridium perfringens counted up 4.8–4.9 × 103, when was only 1.4–2.5 MAD 1.3–1.8 104), lowest LCV (19.2% 15.4% 15.8% respectively). Regarding disposal, after can applied directly agriculture; TPAD, fertilizer case where fermenter HRT assures safety. best being fuel preserving higher portion matter, transforming into biogas during AD.