A method for the energy efficient treatment of polluted wastewater comprising: providing at least a first and second solid polymer electrolyte electrolytic cell stack (201, 202), the cells in the first and second stacks each comprising an anode comprising an anode catalyst layer and the anode catalyst layer comprising an anode catalyst, a cathode comprising a cathode catalyst layer and the cathode catalyst layer comprising a cathode catalyst wherein the cathode is liquid-electrolyte free, and a solid polymer membrane electrolyte separating the anode and the cathode; supplying a flow of wastewater comprising a pollutant to the anode of each of the first and second electrolytic cell stacks at a flow rate and flow pressure; providing a voltage less than 3 volts, plus or minus 10%, across each of the cells in the first and second electrolytic cell stacks wherein the anode is positive with respect to the cathode; operating each of the cells in the electrolytic cell stacks at an operating temperature and a current density less than 20 mA/cm 2, plus or minus 10%, and such that the cathode remains liquid-electrolyte free, thereby degrading the pollutant and generating hydrogen gas at the cathode; and exhausting the generated hydrogen gas from the cathode; wherein at least one of a stack component in the first solid polymer electrolyte electrolytic cell stack and an operating condition of the first solid polymer electrolyte electrolytic cell stack is different from the stack component in the second solid polymer electrolyte electrolytic cell stack and the operating condition of the second solid polymer electrolyte electrolytic cell stack. providing at least a first and second solid polymer electrolyte electrolytic cell stack (201, 202), the cells in the first and second stacks each comprising an anode comprising an anode catalyst layer and the anode catalyst layer comprising an anode catalyst, a cathode comprising a cathode catalyst layer and the cathode catalyst layer comprising a cathode catalyst wherein the cathode is liquid-electrolyte free, and a solid polymer membrane electrolyte separating the anode and the cathode; supplying a flow of wastewater comprising a pollutant to the anode of each of the first and second electrolytic cell stacks at a flow rate and flow pressure; providing a voltage less than 3 volts, plus or minus 10%, across each of the cells in the first and second electrolytic cell stacks wherein the anode is positive with respect to the cathode; operating each of the cells in the electrolytic cell stacks at an operating temperature and a current density less than 20 mA/cm 2, plus or minus 10%, and such that the cathode remains liquid-electrolyte free, thereby degrading the pollutant and generating hydrogen gas at the cathode; and exhausting the generated hydrogen gas from the cathode; wherein at least one of a stack component in the first solid polymer electrolyte electrolytic cell stack and an operating condition of the first solid polymer electrolyte electrolytic cell stack is different from the stack component in the second solid polymer electrolyte electrolytic cell stack and the operating condition of the second solid polymer electrolyte electrolytic cell stack.