Exo-cellular polymers (ECPs) are produced by the bacteria and several studies indicate that the ECPs influence the formation of granules in UASB reactors. It is possible that functional groups associated with the ECP of one microbial cell increase ionic interactions between oppositely charged functional groups in the ECP of other microbial cells, leading to formation of a bond between the two cells. In addition, ions in the media help in bridging between two like-charged functional groups of the cell ECPs [180,181] causing the development of a strong and sticky non-deformable polymeric gel-like matrix.