• Biodegradability
• COD
• Pretreatment
• Soluble COD
• Sonication
• Total Organic Carbon
• Vegetable Tannery Wastewater
• Waste Activated Sludge

The tanning industry in Italy represents a significant contribution to the European economy. At the same time, it is well known that this industry generates significant amounts of contaminated wastewater. Vegetable Tannery wastewater contains high concentrations of organic matter (COD) with a significant percentage of recalcitrant organic compounds. Vegetable tannery wastewater shows several drawbacks due to the complexity of the chemical composition. Contaminants must to removed to avoid significant environmental impacts. In another hand, Activated sludge processes are key technologies in wastewater treatment. These biological processes produce massive amounts of waste activated sludge (WAS) or otherwise bio-solids. Mechanical, thermal, and/or chemical WAS conditioning techniques had been proposed to reduce the sludge charge. Among the WAS treatments; the pre-treatment with Sonication is one of the most innovative processes.
Primary attention is focused on the effect of high-frequency Sonication on reducing organic matter with or without using H2O2 and Aeration. The parameters affecting the removal of the organic matter (COD) and soluble COD (SCOD) and total nitrogen (TN) and total organic carbon (TOC) were also analyzed and compared. Particular attention is then made on how the presence of H2O2, affects the performance of the process, and how it affects the combined Sonication and biological processes.
In other words, the study focuses on the effect of Sono lysis on waste activated sludge solubilization and anaerobic biodegradability of vegetable tannery wastewater and primary sludge of a plant treating tannery wastewater, located in Santa Croce (Tuscany, Italy). The results obtained from a pilot scale study developed in the Tannery wastewater treatment plant (Cuoiodepur).
In the test carried out, the combination of a Sonication pre-treatment with using H2O2 showed satisfactory results regarding reduction COD and SCOD on vegetable tannery wastewater and primary sludge for recovery and reused in the tannery treatment cycle.
The Sonication pre-treatment was able to remove approx. 25% of COD, and SCOD in wastewater and more than 40% of reducing COD and 18% increment of SCOD in the primary sludge of vegetable tannery wastewater. Moreover, the effect of sonication with using H2O2 in total suspended solid (TSS) and volatile suspended solid (VSS) respectively was 35% and 30%. In another hand, the results showed 27% reduction of total organic carbon (TOC) in the primary sludge of vegetable tannery wastewater.