Q: What is biofouling?

A: Biofouling describes the interference in the performance of wetted systems due to the accumulation of biological material.

Q: What is quorum sensing?

A: Quorum sensing refers to the way that bacteria can control their behavior by sensing the presence of other bacteria due to changes in environmental conditions. A certain threshold concentration of bacteria is required in order for quorum sensing to occur.

Q: What is an extrapolymeric substance?

A: An extrapolymeric substance (EPS) is a polysaccharide excreted by bacteria during the process of biofilm formation.

Q: How does biofouling affect the Ashkelon Desalination Plant? 

A: The Ashkelon Desalination Plant in Israel, the 2nd largest Reverse Osmosis plant in the world, treats over 108 million cubic meters of seawater each year. Filtration processes occur through pores on the micro- and nano-scales. The growth of EPS interfere with mass transport by blocking pores on filtration membranes.

Q: What is QCM-D?

QCM-D stands for Quartz Crystal Microbalance with Dissipating Technology. Quartz, a piezoelectric material, responds to electrical current by increasing in size. By applying an alternating current to the quartz crystal, mechanical oscillations can be observed. These oscillations are dependent on the mass of the crystal, with larger masses resulting in decreases in frequency of oscillation. Also, amplitude of oscillations decays once the power is cut off from the material, decaying more quickly for viscoelastic materials. Because of this, QCM-D can be used to measure the adsorption of a biofilm to the surface. The adsorption of the biofilm increases the total mass, which can then be determined by examining the change in oscillation frequency and effect on the decay of the amplitude of oscillations with ng/cm^3 resolution. EPS evinces accelerated dissipation due to its viscoelastic nature.

Q: What factors contribute to the formation of biofoul?

  1. Increased ionic strength.
  2. Increased divalent Calcium concentration (or other similar divalent cations).
  3. Increased alginate presence.