Long-term, high-rate anaerobic biological treatment of whey wastewaters at psychrophilic temperatures [An article from: Bioresource Technology]

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Description:
Two laboratory-scale anaerobic hybrid reactors, R1 and R2, treated low- (1kg CODm^-^3) and high-strength (10kg CODm^-^3) whey-based wastewaters, respectively, in a 500-day trial. The chemical oxygen demand (COD) removal efficiencies of R1 averaged 70-80%, at organic loading rates of 0.5-1.3kg CODm^-^3day^-^1, between 20 and 12^oC. The COD removal efficiencies of R2 exceeded 90%, at organic loading rates up to 13.3kg CODm^-^3day^-^1, between 20 and 14^oC. Lowering the operating temperature of R2 to 12^oC resulted in a decrease in COD removal efficiency, to between 50% and 60%, and a disintegration of granular sludge. The decline in performance, and granule disintegration, was reversed by decreasing the organic loading rate of R2 to 6.6kgm^-^3day^-^1. Specific methanogenic activity profiles revealed mesophilic (37^oC) temperature optima for biomass in both reactors, even after 500days of psychrophilic operation, although the development of psychrotolerance in the biomass was noted.