Biofilm Research

      Posted by Dr. Kyle Murray on May 19, 2009

Microorganisms are natural elements to many aquatic environments and tend to attach to surfaces as a biofilm rather than free floating in a water column. A biofilm is defined as a group of microorganisms attached to a moist surface, embedded in an extracellular polymeric substance (EPS). EPS consists of polysaccharide compounds that are excreted by the cells into their environment. This forms a matrix that encapsulates and protects the cells as well as facilitating cell-to-cell signaling and surface adhesion. Attachment to a surface is the predominant state for bacterial colonies. Attachment may also provide protection from grazing protozoans. For a surface to be considered conditioned for biofilm development, it must be coated with organic molecules originating from decomposed organic material, excretion of living organisms, and the remains of dead organisms. A biofilm is a unique niche and its make up is dependent on the physiochemical environment, as well as the microbes present. Microbial growth rates, for example, are affected by the presence/absence and amount of essential macro- and micro-nutrients in the system. Biological fouling (biofouling) is a term used in the water industry to describe an undesired, advanced stage of biofilm development, which limits well productivity and decreases water quality.

Featured Project: Biofilm Growth and Treatment, Carrizo Aquifer



When well productivity and water quality suffer, well rehabilitation is necessary to reverse the effects of biofilm growth. The biofilm needs to be removed from the well casing, screened interval and from the gravel pack or aquifer material in the near vicinity of the well. Ideally, the well rehabilitation process would not damage the well casing, screen or alter the geochemistry of the groundwater system.

Biofilms can be treated by non-chemical or chemical means. Non-chemical methods physically remove biofilms from the surface of the casing by brushing, scraping, surging and jetting of the well casing. Ultraviolet radiation, a unique non-chemical method, can incite a photochemical reaction that limits microbial growth in water. Chemical methods include addition of a biocide to the well to either loosen biofilms prior to physical techniques or to attack various cellular features of the microorganisms inhabiting the biofilms.

Wells in the Carrizo-Wilcox aquifer are prone to biofilm growth, and have been shown to exhibit biofouling in less than 10 years of installation. Classified as a major aquifer in Texas by the Texas Water Development Board (TWDB), this aquifer provides water to users in 60 counties. Novel methods for removal of biofilms from wells in the Carrizo certainly could help to provide more reliable and inexpensive supplies of water.

Our research in the Carrizo has focused on a three-step process to develop novel treatments for groundwater well biofilms. The first step is in situ growth of the biofilm, second is harvesting and preservation of the biofilm, and third is laboratory scale treatment. Long-term goals are to (1) optimize an in situ treatment technique for groundwater well biofilms, (2) reduce maintenance costs for well fields, and (3) minimize toxicity of treatment to production system.

Carrizo Aquifer



The Carrizo-Wilcox aquifer (red on image above) extends from the Rio Grande in South Texas northeast into Louisiana and Arkansas. The Carrizo sand formation is primarily comprised of sand inter-bedded with gravel, silt and clay dipping to the southeast toward the Gulf Coast of Texas.

Queen City Aquifer





The Queen City Aquifer extends from the Rio Grande River on the southwest border of Texas to the northeastern portion of Louisiana. The aquifer is mostly composed of sand, silt, and clay and is used almost exclusively for livestock troughs and irrigation purposes.