The Effect of Sulfate Concentration on COD Removal and Sludge Granulation in UASB Reactors

Four identical ۳۷.۵ Liter UASB reactors R۱, R۲, R۳ and R۴ were used to study the effect of sulfate concentration on granule formation. Diluted molasses with COD range ۱۰۰۰–۱۳۰۰ mg/l were used as feed and acclimated cow manure was used as seed. Concentration of sulfate ions in the four reactors were ۱۰۰, ۵۰۰, ۱۰۰۰ and ۱۵۰۰mg/l. Granules were observed in R۲ after ۳۳ days from startup time, while in  R۱ and R۳ granules appeared after ۴۵ days. No granules were formed in R۴. Sulfate reduction efficiencies were ۸۴, ۸۹, ۷۱.۵ and ۵۹.۴% while corresponding COD removal efficiencies were ۸۵, ۹۱, ۸۴ and ۷۷% for reactor R۱ to R۴ respectively. Temperature kept at ۳۰ºC allex periments and the best pH for granulation was found to be ۷.۰۰.

Keywords:

Sludge Granulation , Sulfate Concentration , UASB Reactor , COD/SO۴ Ratio