Performance evaluation of full scale uasb reactor in treating stillage wastewater
Stillage, also termed as distillery wastewater, is the aqueous by-product from the distillation of ethanol following fermentation of carbohydrates. The pollution potential of stillage can exceed of 100 g/L as chemical oxygen demand (Wilkie et al.,2000). Upto 20 liters of stillage may be generated for each liter of ethanol produced (Haandel and Catunda, 1998). A medium-sized ethanol facility producing 1,000,000 L ethanol/yr generates stillage with a pollution level equivalent to the sewage of a city with a population of 500,000 (Lele et al., 1989). One of the methods that are used for treating ethanol distillery wastewater, is the application of upflow anaerobic sludge blanket(UASB)reactor. The same studies have been done by Alper et al. ,(2006). Results have shown that efficiency can enhance to 90 percent to eliminate initial pollutants from wastewater. UASB reactors belong to the group of high–rate anaerobic reactors with a sludge bed. Granular biomass with high methanogenic activity and excellent settling properties can be cultivated in these reactors (Buzzini et al., 2006). Startup and granulation are very important parts in operation of UASB reactor. In a study by Soto et al., (1997) was reported the influence of temperature on the granulation process during the startup of UASB reactor. Digesters treat a dilute synthetic wastewater at mesophilic (30Úc) and psychrophilic (20Úc) temperature. Results were shown that the granulation process is followed by a similar pattern and both temperature and complete granulation are achieved between 1 and 2 months after the start up (Ligero et al., 2002).