In this research, an electrochemical wastewater treatment system, powered through the conversion of temperature difference into energy, was designed. The wastewater treatment system was applied to drainage flowing from two different mines, one contaminated by arsenic (As), the other ferrous iron (Fe2+). Arsenic was adsorbed on, or co-precipitated with, iron hydroxide generated from iron electrodes. A pseudo second order model well described the tendency for As removal. Ferrous iron oxidation occurred directly on graphite electrodes and followed a first order reaction model. The efficiency of As and Fe2+ removal was up to 99.7% and 97.9%, respectively. The rate constants for each model were proportional to given temperature differences, as the relationship between current generation and temperature difference was linear. Economic evaluation of the wastewater treatment system was performed by comparing the predicted cost of the thermocouples under particular environmental conditions. The thermocouple technology currently available could be applied to wastewater treatment for hot springs with high temperatures and high As concentrations. The applicability of the system to low temperature wastewaters will expand as energy production capacity per unit cost of thermocouples increases, as occurred with the photovoltaic and heat pump systems currently in use.