module 1 at e2 and exits after treatment via e3 the cell module 1 has an effluent inlet 20 leading via a chamber 21 and openings 22 to the anolyte compartments 17 of the three cells and an effluent outlet 25 communicating with the catholyte compartments 18 of the three cells via an opening 23 passing into a chamber 24 the cathodes 10 are cylinders of microporous sintered tin copper or tin zinc alloys of selected microporosity depending on the mercury concentration in the solution to be treated by the cell module with the described arrangement where the cell module 1 has three cells in parallel each cell module may have identical cathodes but with the microporosity materials of the cathodes varying from one cell module to another alternatively for example in the case when the cells in a cell module are connected in series the different cathodes in a cell module can have different microporosities and may be made of different materials as discussed previously the microporosity will become finer as the solution becomes purer and the cathodes of finest microporosity may have an increased tin content electrical connection to the cathodes 10 and anodes 11 is provided by plates 30 and 31 or copper and titanium respectively separated by an insulating layer 32 in a specific example of the installation three cell modules 1 with the associated equipment as shown in fig1 are connected in series the effluent outlet 25 of the first module leading to the inlet 20 of the next module and so on each cell module 1 has three identical cylindrical cathodes 10 made of sintered tin copper bronze the microporosity of the cathodes in the respective modules is 600 u03bcm 400 u03bcm and.