A cell for direct treatment of liquid using electrolysis uses a modular construction of electrode plates and spacer assemblies positioned between end plates. Changes in the liquid flow capacity of the cell may be made by changing the number of module housing sections and electrode plate assemblies. The design includes electrode plates that lock into a mating module housing section to resist the pressure of the fluid being treated. The design further provides for multiple fluid flow paths and for automatic cleaning of the cell using standard clean-in-place methods.