Anaerobic Treatment of High Strength Dairy Processing Waste in an Upflow Anaerobic Sludge Blanket Reactor

Abstract

An upflow anaerobic sludge blanket (UASB) reactor was used to study the anaerobic digestion of whey permeate. The 25L reactor was capable of reducing a soluble organic load of 15 kg COD/m3. d by 95% while an increased load of 20 kg COD/m3.d resulted in 90% COD reduction. The methane production rate increased linearly with the loading rate up to a loading rate of 15 kg COD/m3.d beyond which there was no increase in methane yield. An analysis of the sludge granules revealed that the accumulation of inorganics in the granules was significant and the specific activity of the granules could be adversely affected by the concentration of calcium and magnesium salts, in particular the phosphate and carbonates. The concentration of methane in the biogas was approximately 52% for organic loads up to 15 kg COD/m3.d but beyond this value the methane concentration dropped to a low 41%. The yield of methane was 4.1 m3/m3.d for organic loading rates of up to 15 kg COD/m3.d.