Identification and characterisation of biofilm formed on membrane bio-reactor

Experiments were conducted in a laboratory scale membrane bio-reactor (MBR) system equipped with a side stream flat sheet membrane. Six runs lasting different durations (2, 4, 6, 9, 15 and 20 days) were conducted at an aeration rate of 2 m3 h−1 m−2 to understand the temporal variation of chemistry of foulant that attached on the membrane surface. The foulant attached on the membrane surface was extracted with 0.5% (v/v) NaOH solution and the extract was analysed using fluorescent spectroscopy and size exclusion chromatography. Variation of low- and high-molecular weight substances with evolution of time was compared. The results showed that the nature of foulant changed with the evolution of time. Four runs conducted for a short duration (2, 4, 6 and 9 days), low-molecular weight substances were dominant in the foulant whereas for long duration runs (15 and 20 days), high-molecular weight substances were mainly observed. Moreover, the foulant close to the membrane surface contained mainly protein and soluble microbial by-products.