Bacterial adhesion involves the attachment (or deposition) of bacteria on the surface (solid, gel layer, etc.). This interaction plays an important role in natural system as well as in environmental engineering. The attachment of biomass on the membrane surface will result in membrane fouling, which can significantly reduce the efficiency of the treatment system using membrane filtration process in wastewater treatment plants.^[1] The low adhesion of bacteria to soil is essential key for the success of in-situ bioremediation in groundwater treatment.^[2] However, the contamination of pathogens in drinking water could be linked to the transportation of microorganisms in groundwater and other water sources.^[3] Controlling and preventing the adverse impact of the bacterial deposition on the aquatic environment need a deeply understanding about the mechanisms of this process. DLVO theory has been used extensively to describe the deposition of bacteria in many current researches.^{[1][2][3][4][5][6]}

Prediction of bacterial deposition by classical DLVO theory

DLVO theory describes the interaction potential between charged surfaces. It is the sum of electrostatic double layer, which can be either attractive of repulsive, and attractive Van der Waals interactions of the charge surfaces.^[2] DLVO theory is applied widely in explaining the aggregation and deposition of colloidal and nano particles such as Fullerene C60 in aquatic system. Because bacteria and colloid particles both share the similarities in size and surface charge, the deposition of bacteria also can be describe by the DLVO theory.^[1][2][3][4] The prediction is based on sphere-plate interaction for one cell and the surface.

The electrostatic double layer interactions could be describes by the expression for the constant surface potential ^[2][3][4][6]

${\displaystyle V_{EDL}=\pi \varepsilon _{0}\varepsilon _{r}a_{p}{\bigg \{}2\psi _{p}\psi _{c}ln{\bigg [}{\frac {1+exp(-\kappa h)}{1-exp(-\kappa h)}}{\bigg ]}+(\psi _{p}^{2}+\psi _{c}^{2})ln{\big [}1-exp(-2\kappa h){\big ]}{\bigg \}}}$

Where ε₀is the vacuum permittivity, ε_r is the relative dielectric permittivity of water, a_p is the equivalent spherical radius of the bacteria, κ is the inverse of Debye length, h is the separation distance between the bacterium and the collector surface; ψ_p and ψ_c are the surface potentials of the bacterial cell and the collector surface. Zeta potential at the surface of the bacteria and the collector were used instead of the surface potential.

The retarded Van der Waals interaction potential was calculated using the expression from Gregory, 1981 .^[1][2][3][4]

${\displaystyle V_{VdW}=-{\frac {Aa_{p}}{6h}}{\bigg [}1+{\frac {14h}{\lambda }}{\bigg ]}^{-1}}$

With A is Hamaker constant for bacteria-water-surface collector (quartz) = 6.5 x 10⁻²¹ J and λ is the characteristic wavelength of the dielectric and could be assumed 100 nm, a is the equivalent radius of the bacteria, h is the separation distance from the surface collector to the bacteria.

Thus, the total interaction between bacteria and charged surface can be expressed as follow ${\displaystyle V_{TOT}=\pi \varepsilon _{0}\varepsilon _{r}a_{p}{\bigg \{}2\psi _{p}\psi _{c}ln{\bigg [}{\frac {1+exp(-\kappa h)}{1-exp(-\kappa h)}}{\bigg ]}+(\psi _{p}^{2}+\psi _{c}^{2})ln{\big [}1-exp(-2\kappa h){\big ]}{\bigg \}}-{\frac {Aa_{p}}{6h}}{\bigg [}1+{\frac {14h}{\lambda }}{\bigg ]}^{-1}}$

Current experimental result

References