text: Radial stagnant point flow (RSPF) system has currently been used for the experiment of bacterial adhesion with the verification of DLVO theory. It is a well-characterized experimental system and is useful for visualizing the deposition of individual bacteria on the uniform charge, flat quartz surface. The deposition of bacteria on the surface was observed and estimated through an inverted microscope and recorded at regular intervals (10 s or 20 s) with a digital camera.
  Flow flied at the stagnation point flow https://web.archive.org/web/20090418224617/http://www.yale.edu/env/alexis_folder/alexis_research_2b.jpg
  Many bacterial stains have been used for the experiments. They are: 
  *Cryptosporidium parvum oocysts, having 3.7 μm equivalent spherical diameter.
  *Escherichia coli, having 1.7 μm equivalent spherical diameter.
  *Pseudomonas aeruginosa, having 1.24 μm equivalent spherical diameter.
  All of the bacterial strains have negative zeta potential at experimental pH (5.5 and 5.8) and less become negative at higher ionic strength in both mono and divalent salt solutions.
  Ultra pure quartz surface collectors have been used extensively due to their surface homogeneity, which is an important factor for applying DLVO theory. The quartz surface originally has negative potential. However, the surface of the collectors was usually modified to have positive surface for the favorable deposition experiments. <br />
  In some experiments, the surface collector was coated with an alginate layer with negative charge for simulating the real conditioning film in natural system.