Biotechnology Laboratory

Center for Innovation, Inc.

Biofilm Barriers and Treatment Zones

Large numbers of bacteria are naturally present in every ecosystem.  These bacteria are usually harmless to humans and can help decompose waste materials.  Healthy, growing bacteria produce large quantities of a slimy material called extracellular polymeric substances (EPS).  Large colonies of bacteria and associated EPS, called biofilms, can be used to form subsurface barriers that can impede the flow of contaminated groundwater and remediate the pollutant.  This is the basis for Biofilm Barrier Technology.

 

Without sufficient food, bacteria reduce in size and remain dormant until another nutrient source is available. This response to a lack of nutrients allows the bacteria to survive long periods of time with very little food.  Because of their unique properties, starved bacteria, or Ultramicrobacteria (UMB) as they are often called can be injected much greater distances through the subsurface than full-sized bacteria. This ability makes the formation of deep biological barriers feasible.

 

CFI staff members have constructed field scale biofilm barriers that have been able to reduce hydraulic conductivity by approximately two orders of magnitude and maintain this condition for an extended period as shown below. We have also successfully shown that these semi permeable barriers can remediate nitrate contaminated groundwater to less than 10 milligrams per liter (EPA Drinking Water Standard) as shown on the figures below. The first figure below shows that the reduction in hydraulic conductivity developed by the biofilm barrier can be sustained for an extended period of time, while the second figure portrays nitrate concentrations before and after the contaminated water passed through the biofilm barrier treatment zone.