Initial Determination of Electrocoagulation as an Oily Wastewater Treatment Technique at Shore Facilities

Utilization of oily wastewater collection systems at shore facilities are required for Navy vessels when moored piers ide or returning to homeport. While in state and federal waters (less than 12 nautical miles from shore), collected oily wastewater is often processed through specialized shore systems (i.e., the bilge and oily wastewater treatment system) to separate oil and grease fractions from the bulk wastewater originating from vessels. In certain situations, chemical contaminants such as metals or organics may be found within discharged oily wastewater. While these constituents are generally easily treated in industrial wastewater facilities, emerging and ubiquitous contaminants such as perfluorooctane sulfonic acid (PFOS) and other per-and polyfluoroalkyl substances (PFAS) are not easily treated with conventional wastewater facilities and may require additional treatment. The work presented here describes the initial assessment of electrocoagulation as a rapid treatment of ship-generated oily wastewater. We show that aluminum-based electrocoagulation can effectively remove oil-grease fractions from samples of saline water at relatively low voltages. In these experiments, applied DC voltages ranged between 2V and 4V and measured electrical currents ranged between 2A and 13A. We present treatment efficiencies of approximately 80% with electrocoagulation times of less than 15 minutes. Tests of PFOS removal show that at least 75% of PFOS from the water fraction can be removed through a 10-minute treatment cycle, with the maj ority ending up in the foam fraction. These results show that electrocoagulation is a promising approach for oily wastewater treatment at shore facilities supporting maritime vessels. Moreover, the low voltages and currents observed can lend themselves to the development of portable devices for effective treatment at low power demands. When utilized as a pre-treatment process, electrocoagulation can significantly remove a large fraction of contaminants. Removal or reduction of the oily wastewater waste stream also has the potential to reduce or elinate the introduction of seawater to conventional wastewater treatment plants. Thus, when combined with targeted downstream treatment processes, electrocoagulation can be an inexpensive, yet effective, part of a wastewater treatment process.