Development of bio-granules using selected mixed culture of decolorizing bacteria for the treatment of textile wastewater

Abstract

In this study, four dye-degrading bacteria, Bacillus pumilus strain ZK1, Bacillus cereus strain ZK2, Brevibacillus panacihumi strain ZB1, and Lysinibacillus fusiformis strain ZB2 were used for the development of granule. Sterile sludge was used as seeding agent in a sequencing batch reactor under intermittent facultative anaerobic–aerobic system followed by subsequent textile wastewater treatment. Physical and morphological characteristics of the granules were determined after 112 d of development time. The average size of the mature granules reached 3.3 ± 1 mm, with integrity coefficient of 25 ± 2, settling velocity of 56 ± 5 m h-1, and sludge volume index of 35 ± 5.5 mL g-1. Mixed liquor suspended solids and mixed liquor volatile suspended solids were 12.9 ± 0.8 and 11 ± 0.6 g L-1, respectively. The developed granules showed 61% of decolorization and 46% of COD removal at HRT of 24 h. The population distribution of the bacteria consortium in mature granules developed into subsequent ratio of 1:4:9:11 from initial inoculum ratio of 1:1:1:1 of B. pumilus strain ZK1, B. cereus strain ZK2, B. panacihumi strain ZB1, and L. fusiformis strain ZB2, respectively. The results obtained indicated that this mixed culture of bacteria has good potential application for the treatment of textile wastewater.