In the province of Vicenza (Italy) electric power is generated by burning methane produced from anaerobic digestion of agricultural waste and biomass. Pilot plant tests were run from the beginning of March to the end of June 1999 to verify the feasibility of treating the highly contaminated liquid effluents by means of semi-permeable membranes. The test program was brought to a successful end with the decision of the owner to proceed to the construction of a full-scale waste water treatment plant. Results of the experimental program are described and records of pilot plant runs are reported and commented. Significant details of full plant scale-up are also described.