Applicability of short-term accelerated biofouling studies to predict long-term biofouling in reverse osmosis membrane systems

Abstract

a b s t r a c tBiofouling studies addressing biofouling control are mostly executed in short-term studies. It is unclear whether data collected from these experiments are representative for long-term biofouling as occurring in full-scale membrane systems. This study investigated whether short-term biofouling studies accelerated by biodegradable nutrient dosage to feed water were predictive for long-term biofouling development without nutrient dosage. Since the presence of a feed spacer has an strong effect on the degree of biofouling, this study employed six geometrically different feed spacers. Membrane fouling simulators (MFSs) were operated with the same (i) membrane, (ii) feed flow and (iii) feed water, but with feed spacers varying in geometry. For the short-term experiment, biofilm formation was enhanced by nutrient dosage to the MFS feed water, whereas no nutrient dosage was applied in the long-term experiment. Pressure drop development was monitored to characterize the extent of biofouling, while the accumulated viable biomass content at the end of the experimental run was quantified by adenosine triphosphate (ATP) measurements. Impact of feed spacer geometry on biofouling was compared for the short-term and long-term biofouling study. The results of the study revealed that the feed spacers exhibited the same biofouling behavior for (i) the short-term (9-d) study with nutrient dosage and (ii) the long-term (96-d) study without nutrient dosage. For the six different feed spacers, the accumulated viable biomass content (pg ATP.cm -2 ) was roughly the same, but the biofouling impact in terms of pressure drop increase in time was significantly different. The biofouling impact ranking of the six feed spacers was the same for the short-term and long-term biofouling studies. Therefore, it can be concluded that short-term accelerated biofouling studies in MFSs are a representative and suitable approach for the prediction of biofouling in membrane filtration systems after long-term operation.

The membrane fouling simulator: development, application, and early-warning of biofouling in RO treatment

“…Such device should be representative for conventionally used membrane modules, thus involving the used materials (properties and structure) such as membrane and spacer, the height of the flow channels and hydraulics. The membrane fouling simulator (MFS) was introduced in 2006 [4] and since then many articles have appeared on various research aspects of biofilm characterization [2,3,[27][28][29][30][31][32][33][34][35][36], biofouling control [5,[37][38][39][40][41][42][43][44][45][46][47][48][49], and strategies for early warning of biofouling [50][51][52][53][54][55] applying the developed MFS.…”

“…An MFS study was carried out to assess whether short-term biofouling experiments with biodegradable nutrient dosage are predictive for long-term biofouling development with no addition of nutrient [60]. Feed spacer plays an important role in biofouling.…”

“…Feed spacer plays an important role in biofouling. Therefore, this study addressed six feed spacers differing in geometry [60]. MFSs were operated with the same membrane and same water and feed flow, but with different geometry spacers [60].…”

“…Therefore, this study addressed six feed spacers differing in geometry [60]. MFSs were operated with the same membrane and same water and feed flow, but with different geometry spacers [60]. During the shortterm study, biofilm development was accelerated by dosing biodegradable nutrient to the MFS.…”

“…The six feed spacers showed the same ranking for the biofouling impact on FCP increase for the short-and long-term biofouling analysis. Using MFSs, short-term biofilm studies with nutrient dosage proved to be representative and suitable for predicting biofouling after long-term operation [60].…”