Contribution of assimilable organic carbon to biological fouling in seawater reverse osmosis membrane treatment.
Biological fouling occurs on RO membranes when bacteria and nutrients are present in conditions that are conducive to growth and proliferation of the bacteria. Controlling microbial growth on the membranes is typically limited to biocide application (i.e., disinfectants) in seawater RO plants. However, biological growth and subsequent fouling has not been well-managed. Pretreatment has not been focused on nutrient limitation. This project used a biological assay, the assimilable organic carbon (AOC) test to evaluate pretreatment effects on the nutrient supply. The AOC test provided a useful surrogate measurement for the biodegradability or biofouling potential of RO feed water. Biofouling observed in controlled conditions at the bench- and pilot-scale resulted in statistically significant correlations between AOC and the operational effects caused by biofouling. Membrane fouling rates are observed through operational changes over time such as increased differential pressure between the membrane feed and concentrate locations and decreased permeate flux through the membrane. In full scale plants there were strong correlations when AOC was used as a predictor variable for increased differential pressure (0.28-0.55 bar from September-December 2012) and decreased specific flux (1.40 L per hour/(m(2) · bar)). Increased differential pressure was associated with RO membrane biological fouling when the median AOC was 50 μg/L during pilot testing. Conditions were also evaluated at the bench-scale using a flat sheet RO membrane. In a comparison test using 30 and 1000 μg/L AOC, fouling was detected on more portions of the membrane when AOC was higher. Biofilm and bacterial deposits were apparent from scanning electron microscope imaging and biomass measurements using ATP.
213 Carriage Lane Delran, NJ 08075, USA. Electronic address: Lauren.weinrich@amwater.com.
Lauren
L
Weinrich
1025 Laurel Oak Road Voorhees, NJ 08043, USA. Electronic address: Mark.lechevallier@amwater.com.
Mark
M
LeChevallier
3141 Chestnut Street Philadelphia, PA 19104, USA. Electronic address: Haas@drexel.edu.
Charles N
CN
Haas
D057219:Biofouling; D002244:Carbon; D008567:Membranes, Artificial; D009995:Osmosis; D012623:Seawater; D018508:Water Purification
D008567:Membranes, Artificial; D002244:Carbon
AOC; Biofouling; Desalination; Pretreatment; Reverse osmosis; Seawater