Comparison of two fractionation strategies for characterization of wastewater effluent organic matter and diagnosis of membrane fouling

Two fractionation strategies were compared for characterizing organic components in effluent organic matter (EfOM) and natural organic matter (NOM). The first method is widely used and requires sample acidification and then re-neutralization during sequential organic removals onto resins. The second method uses a different suite of separation methods, does not require pH manipulation, and sequentially removes particles, colloids, organic acids, and hydrophobic neutrals without the need for adjusting pH. The NOM samples were dominantly organic acids while EfOM contained a broader distribution of organic functionalities so further evaluation was focused on EfOM. The new method completely removed colloidal matter from EfOM while the conventional fractionation method resulted in an increase in the percentage of EfOM >100 kDa with each fractionation step after filtration. Organic acids were removed in one fractionation step using the new method instead of three steps with the conventional method. The conventional method resulted in increased fouling after the final separation step apparently caused by production of inorganic colloids. The new fractionation method provided a clearer diagnosis that organic acids were the primary cause of fouling even though they were only 14% of EfOM organic carbon. We suggest that the new fractionation method should be considered for diagnosing the effects of NOM or EfOM on the performance of membrane filtration. (C) 2012 Elsevier Ltd. All rights reserved.