Phenol and chlorophenols are common environmental contaminants. The fate and transport of these chemicals must be sufficiently understood to predict detrimental environmental impacts and to develop technically and economically appropriate remedial action to minimise environmental degradation. In order to gain a better understanding of the many mechanisms influencing the fate of phenol and chlorophenols in a sandy aquifer, we conducted biosorption experiments with biomass collected from a simulated aquifer polluted by consecutive accidental spills of phenol, 2-monochlorophenol, 2,4,6-trichlorophenol and pentachlorophenol under continuous bioremediation conditions following a closed-loop configuration during 180 days. A comparative study of the biosorption capacity of phenol and chlorophenols characterised by different physicochemical properties, at different pHs in the range of 6.0+/-0.1 to 9.0+/-0.1 showed the following: (i) the biosorption of phenol and chlorophenols on resident biomass was rapid (equilibrium reached in less than 2h); (ii) the experimental data followed the Freundlich isotherm; (iii) changes in pH from 6.0+/-0.1 to 9.0+/-0.1 resulted in a decrease in the equilibrium biosorption capacity (qeq); (iv) both Freundlich parameters (KF, n) should be used together as predictive parameters in mathematical models to simulate the fate of phenol and chlorophenols in the aquifer; (v) qeq of phenol and chlorophenols investigated in this study were satisfactorily correlated to their hydrophobicity (Kow) with a correlation factor 0.98. In addition, available data from other reported studies fell in the same correlation curve. The results of the present study should be introduced in mathematical models developed to predict the effect of biomass fate and transport of contaminants in aquifers during bioremediation conditions.