The sustainable recovery of the organic fraction of municipal solid waste by integrated ozonation and anaerobic digestion

The organic fraction of municipal solid waste is commonly handled via biological processes, which enable the production of materials with potential fertilizer properties. When the biological process occurs under anaerobic conditions, the recovery of energy from biogas is also obtained. However, the sustainable recovery of organic solid waste implies the effective utilization of the biological treatment products, namely compost and digestate, which is often limited by the presence of organic contaminants. They enter the biological processes along with the organic waste and, due to their recalcitrance to the biodegradation, end up in either compost or digestate, posing the issue of their safe use on soil. The present study proposes ozonation as a possible strategy to reduce the presence of organic contaminants in the digestate originating from the organic fraction of municipal solid waste. In this view, digestate samples were collected from full-scale reactors operated at hydraulic retention time of 11 and 41 days and ozonated at 0.11 and 0.16 gO3/gTS. Experimental results, including the evaluation of the eco-toxicological potential of differently treated substrates, showed that the integration of ozone and anaerobic digestion can be pursued for the sustainable recovery of organic solid waste, but the identification of the combined process lay-out requires the evaluation of the digestate biological stabilization level.