Ways to increase the efficiency of the electric spark method of wastewater purification from heavy metal ions by increasing the stability of discharges and reducing energy losses are shown. General regularities of changes in the electrical characteristics of a multi-spark underwater discharge distributed in a layer of a mixture of iron and aluminum granules from the parameters of the discharge circuit have been revealed. The dependencies of the power amplitudes of electric spark discharges in a layer of metal granules on time under conditions of different combinations of inductance and capacitance of the discharge circuit are formalized, the regularities of energy input into working reactors to regulate the conditions and efficiency of purification are considered.