Abstract: An improved bio-electrochemical wastewater treatment process and system (1) is disclosed. An electrode assembly (4) is defined by interconnecting a set of electrode modules (5). Each electrode module (5) has a first electrode of an anode-cathode pair coated with electrogenic microbes adapted to generate electrons via the consumption of organic matter in wastewater. An electrode module (5) has a second electrode of the anode-cathode pair, and a body, supporting and separating the first and second electrodes. Each electrode module (5) also comprises an interface for physically connecting the module with at least one other of the set.