Disinfection Of Sewage Sludge Research Articles

A LCA study to investigate resource-efficient strategies for managing post-consumer gypsum waste in Lombardy region (Italy)

This study aimed at evaluating environmental sustainable solutions for managing the gypsum waste in Lombardy region (Italy), based on the Life Cycle Assessment (LCA) methodology. Primary data and information related to gypsum waste flows, recovery technologies and end-market of recycled materials were gathered to depict the whole recycling chain and to build up a life cycle inventory dataset specific for the geographical context under study. The LCA analysis of the current scenario allowed to identify strength and weak points of the regional system: up to date, most impacts are related to the recovery of gypsum waste by mixing with other mineral construction and demolition waste, which appeared as the prevalent option. Different alternative scenarios were hence analyzed by considering that all the gypsum waste is recycled in dedicated plants and by analyzing different end-uses of the recycled material. The focus was placed on four major sectors for which the use of recycled gypsum is technically feasible: plasterboard manufacturing, cement industry, disinfection of sewage sludge, and agriculture. For each analyzed end-use scenario, the potential market demand in Lombardy region as well as the technical requirements of the recycled gypsum were evaluated as key points in the LCA. Results from the impact assessment were used to provide recommendations for the regional government to move towards a more resource-efficient waste management.

Coliform inactivation in sludge by copper sulphate

Studies were conducted to demonstrate the effectiveness of copper sulphate for disinfection of sewage sludge under anaerobic conditions. The effects of suspended solids and copper dosages on the survival of total coliforms in normal (neutral pH) and acidified sludges (pH 2.1–3.8) were studied. Results indicated that disinfection of sewage sludge by copper sulphate was feasible. Under anaerobic conditions, significant reductions (about 99%) of total coliform bacteria in normal sludge were achieved at a dosage of 40 mg Cu/g dry sludge mass, sludge suspended solids of < 3.0%, and a contact time of 24 h. The toxic effect of copper dosage was enhanced and the copper dosage and contact time reduced at lower pH (2.1–3.8). Sludge so treated would be suitable for land application insofar as its bacteriological quality is concerned, provided the high copper concentration could be reduced to acceptable levels. Whether this can be achieved in subsequent treatment of disinfected sludge by bacterial leaching will be determined in a future study. Key words: sludge disinfection, coliforms, copper sulphate, sludge disposal, bacterial leaching.

Stabilization and Disinfection of Sewage Sludge by Two-Stage Anaerobic Thermophilic/Mesophilic Digestion

The first equipment for two-stage anaerobic thermophilic/mesophilic digestion (55/35 °C) of sewage sludge constructed in Germany in 1987 was investigated during one year of large-scale operation. Stabilization efficiency of this process is higher compared to conventional mesophilic digestion at this plant. Disinfection of sewage sludge during thermophilic treatment in the first stage is up to the demands of German legislation.