BIOHYDROGEN FROM CHEESE WHEY TREATMENT IN AN AnSBBR: ACHIEVING PROCESS STABILITY
Brazilian Journal of Chemical Engineering
An AnSBBR (anaerobic sequencing batch reactor containing biomass immobilized on an inert support) with liquid phase recirculation, containing a 3.5 L working volume, treated 1.5 L of cheese whey wastewater in 3 and 4 h cycles at 30 °C to produce biohydrogen. From startup the bioreactor presented process instability. To overcome this problem the following measures were taken, however without success: adaptation of the biomass with uncontaminated easily degradable substrates, pH control at very
... H control at very low levels, and a different form of inoculation (natural fermentation of the feed medium). The problem was solved by cooling the feed medium to 4 °C to prevent acidification in the storage container, by eliminating nutrient supplementation to prevent possible formation of H 2 S by sulfate-reducing bacteria and by periodic washing of the support material to improve the food/microorganism ratio. Hence, stable hydrogen production could be achieved with minimal presence of methane (36% H 2 ; 62% CO 2 ; 2% CH 4 ) and the AnSBBR fed with cheese whey (influent concentration of 4070 mgCOD.L -1 and 3240 mgCarbohydrate.L -1 and applied volumetric organic loading of 14.6 gCOD.L -1 .d -1 ) presented improved productivity and yield indicators compared to pure lactose and other reactor configurations, reaching values of 420 NmLH 2 .L -1 .d -1 and 0.60 molH 2 .molCarbohydrate -1 in the steady-state phase (conversions of carbohydrates and COD were 98% and 30%, respectively).