Abstract Summary
Since the implementation of Directive 91/271/EEC, there has been an increase in sludge generation, which necessitates efficient management. The use of sludge for energy recovery and soil improvement is environmentally beneficial, if it does not harm human health or the environment. This use is regulated by Directive 86/278/EEC, with a proposed directive enhancing protection and requiring advanced treatments such as composting, thermal drying and pasteurisation. The Camellia® system is an advanced treatment that involves thermal pretreatment of thickened sludge followed by mesophilic post-anaerobic digestion. The process includes a pasteurization tank where the thickened sludge undergoes thermal treatment for a minimum of ten minutes at 80°C, or 20 minutes at 75°C, or 30 minutes at 70°C, followed by a mesophilic anaerobic digestion process with a Hydraulic Retention Time (HRT) of at least 12 days. Camellia® is included among the systems listed in the 4th draft of the Directive, as well as in the Andalusian Ordinance, to meet the parameters set forth for its application in agricultural soil with guarantees. Additionally, Camellia® can feature an innovative heating system that uses 100% renewable energy (thermal and electrical). An industrial-scale Camellia® system is being constructed at the Iscar WWTP. To study the influence of sludge pasteurization on methane production, biochemical methane potential (BMP) tests have been conducted with mixed sludge from the Iscar WWTP and sludge subjected to pasteurization processes. The results of the BMP tests indicate that methane production increases by 18-25% in the Iscar WWTP sludge that was subjected to pasteurization prior to anaerobic digestion in comparison with unpasteurized sludge. In addition to the increase in methane production, the Camellia® system is expected to result in a reduction in biosolid production, an increase in digester load, and the production of stabilized and sanitized sludge.
