Various biofilter-immersed membrane configurations were examined in this research in order to determine which configuration resulted in the best water quality as defined by removals of total organic carbon (TOC), readily biodegradable carbons, and UV absorbance. In addition, the configuration which resulted in the lowest overall rate of membrane fouling was established. The water selected for study was intended to mimic a difficult to treat surface water, therefore the synthetic water used in the research was comprised of about 65% humic acid and 35% readily biodegradable carbons. The high humic acid content was selected as it is known to both cause organic fouling on membranes as well as being considered difficult to treat with a biofilter. Therefore the purpose of this research was to determine which configuration resulted in maximum water quality and the lowest rate of membrane fouling with a difficult to treat water source.

Four configurations were studied in total. The first two examined a biofilter followed by a membrane, and a membrane followed by a biofilter. Later studies examined the influence of a support media in the membrane tanks, therefore the configurations were biofilter - membrane + support media, and membrane + support media and biofilter. Over the course of the research, TOC removals improved from approximately 30% to 60%, with influent TOC levels ranging from 1.8--3.6 mg/L. The biofilter columns were maintained throughout the duration of the research, which lasted 24 months. The readily biodegradable carbons, acetate, formate and formaldehyde were all readily removed by the biofilters within 5 months of operation. In addition, humic acid was found to be removed both by the membrane as well as the biofilters. The biofilters when located first were found to remove up to 30% of the humic acid in the influent water. The reduction in UV absorbance values through the biofilters increased from 0% to 60% throughout the study. The total UV absorbance removal in the processes improved from 55 to 75%. On a short-term basis the biofilter-membrane system was found to be more effective at decreasing TOC, UV and the readily biodegradable carbons in the system, however on a long term (over 18 months) basis both processes were found to be nearly equal.

The membrane fouling was determined by monitoring the change in transmembrane pressure over time. Not surprisingly, the biofilter-membrane process fouled at a slower rate than the membrane-biofilter process. The addition of the support media was also found to significantly decrease the fouling on the membrane. Therefore, in terms of decreased membrane fouling the biofilter-membrane + support material was found to be most effective. Thus, as the system generally performed similarly in terms of produced water quality the preferred configuration to maximize water quality and minimize fouling is the biofilter-membrane + support material.