Sustainable flux fouling in a membrane bioreactor: Impact of flux and MLSS

The long term sustainable flux behavior of a submerged membrane bioreactor operated under a steady state conditions at a range of mixed liquor suspended solids (MLSS) concentrations has been examined. Comparison of fouling rates at a number of imposed fluxes has been made between long term filtration trials and short term tests using the flux step method. Results indicate an exponential relationship between fouling rate and flux for both long and short term trials, although the value was an order of magnitude lower during long term tests. Moreover, operation during long term trials is characterised by a period of pseudo stable operation followed by a catastrophic rise in TMP at a given critical filtration time (t(filt)) during trials at 6 g (.) L-1 . This time of stable operation, t(filt), is characterised by a linear relationship between fouling rate and flux. Results have been compared with the literature. Data for membrane fouling prior to the end of t(filt) yielded a poor fit with a recently proposed model. Trends recorded at t > t(filt) revealed the fouling rate to follow no definable trend with flux, contrary to the notion that fouling beyond the critical filtration time relates to solids deposition.