Anaerobic digestion is carried out to stabilize biosolids so that it is acceptable for land disposal. Although no precise definition A solution based on sludge and Olive oil mill effluent (OME) codigestion, coupled with a management plan, has been implemented, to treat and dispose safely, the mixed residues, into the natural forest and agricultural land.
The mixture of up to 25 % OME to the sludge improved anaerobic degradation of phenols and fats. High density fats compounds, presents in OME, enhanced aggregation, settling and acetoclastic activity of anaerobic sludge. The full scale unit, obtained by modification of a cold digester, allowed to set-up a low capital cost system. The system produced large quantity of biogas and electric energy.
Anaerobic degradation of the mixture improved fertilizing properties, making feasible land application of the digested mixture. Regional plan based in Geographical Information System (GIS) selected 800 ha of adequate land area for application near the WWTP. The experience is technically and economically successful. Main incomes are provided by energy use and OME charge. Sludge application in local agriculture does generate any income, but eliminated landfill costs and reduced transportation costs.