Feasibility of composting combinations of sewage sludge, olive mill waste and winery waste in a rotary drum reactor.

Representative samples of the following biowastes typically generated in Castilla La Mancha (Spain) were composted using a pilot-scale closed rotary drum composting reactor provided with adequate control systems: waste from the olive oil industry (olive mill waste; OMW), winery-distillery waste containing basically grape stalk and exhausted grape marc (WDW), and domestic sewage sludge. Composting these biowastes was only successful when using a bulking agent or if sufficient porosity was supported. OMW waste composting was not possible, probably because of its negligible porosity, which likely caused anaerobic conditions.

Enhancing the co-composting of olive mill wastes and sewage sludge by the addition of an industrial waste.

In this work, the effect of incorporating an acidic ferrous sulphate waste (SF) over co-composting process of sewage sludge and olive mill solid wastes in a 1:2 v/v wet basis was investigated. The SF used was an industrial by-product of titanium oxide synthesis and its addition resulted in a chemical stabilisation of the wastes at low pH. The optimum dose of SF to enhance the composting of the studied biowastes was a 20% v/v (wet basis) and the best moment for the addition turned out to be whenever the composting piles had achieved the thermophilic range.