STABILIZATION BY CO-COMPOSTING OF SOLIDS REMOVED FROM WASTEWATER TREATMENT PLANT OF A CHEESE FACTORY

A wastewater plant of a dairy industry generates 1.6 tons/month of settleable solids and 650 kg/week of floatable solids, which if not adequately disposed off, can cause serious soil contamination and vector attraction. A composting process for stabilizing residues with high fat content that generate unpleasant odors is presented. Laboratory experiments were carried out for determining the appropriate process parameters, and scaled-up for the in situ process. Laboratory tests with cattle manure showed a reduction in the production of malodorous gases in three weeks. The resulting compost complied with national and international standards, and can be used in 1: 3 compost: soil ratio for soil improvement. The waste stabilized in situ complied with most parameters established in the Mexican regulation (NOM-FF-109-SCFI-2007), excepting pH (9.6) and electrical conductivity (5 dS/m).