Investigation of Desalination Membrane Biofouling
Year Released: 2014
Type: Scientific Investigation
Funding Partners: Bureau of Reclamation
Total Investment: $338,956 (Cash: $110,000, In-Kind: $228,956)
Principal Investigators: Sunny Jiang, PhD – University of California, Irvine and Nikolay Voutchkov, PE, DEE – Water Globe Consulting, LLC
One of the challenges seawater desalination faces today is reverse osmosis (RO) membrane biofouling. Depending on its severity, biofouling may have a measurable impact on the economics and reliability of freshwater production by desalination. Biofouling is caused by biofilm formation on the RO membrane surface by bacteria, which naturally occur in the feed seawater. Although all membranes foul, the rate and reversibility of biofouling are the two key factors that have most profound effect on the performance and efficiency of the SWRO separation process. This project provides an in-depth understanding of the type, metabolism and lifecycle of the microorganisms responsible for surface colonization and the environmental and seawater quality factors that trigger their accelerated growth.
Goals and Objectives
This project has three main objectives. The first was to identify and quantify the water quality constituents and environmental factors that trigger accelerated biofouling of seawater reverse osmosis (SWRO) membranes and to determine key species of marine microorganisms involved in biofilm formation. Second, this project defines the thresholds of easy-to-measure seawater parameters, which could be used as precursor indicators of accelerated biofouling. Lastly, multiple biofouling control strategies were tested to offer insight into the desalination facility operation.
Findings and Conclusions
This project demonstrated that diverse microbial organisms are responsible for SWRO membrane biofouling including some bacterial genera and species that had not been previously recognized by the culture-based investigations using artificial nutrient medium. However, in spite of the diversity of membrane fouling organisms in seawater feedstock in different regions of the world, there are common culprits that are the main players for SWRO membrane biofilm formation. An effective control for the main genera and species of membrane fouling organisms may offer a solution to SWRO membrane fouling. Organic nutrients, or more specifically complex organic carbon, are important causes for accelerated bacterial growth and membrane biofouling. Coastal algal blooms and associated chlorophyll concentration may be used as a precursor for SWRO fouling potential. Balancing the ratio between organic carbon (OC), nitrogen (N) and phosphate (P) to 1:1:1 in the feedstock was shown in this study to reduce biofilm thickness and membrane fouling rates.