The Department of Defense (DoD) uses oil/water separators (OWS) extensively to remove oil from a variety of aqueous waste streams prior to discharge. On-site or shipboard methods to treat or reduce the volume of accumulated sludges generated by these OWSs are required to eliminate sludge transportation costs for offsite disposal, to reduce downtime for maintenance, and to increase separator efficiency. The Navy currently spends about $24 million per year to treat 1 billion gallons of bilge oil; which includes storage, off-loading, on-shore treatment, transportation, and off-site disposal costs.

This project developed a two-stage incineration process comprised of a primary vortex containment combustion (VCC) process and an actively controlled and monitored after-burner (AB) process for emissions reduction. The process was automated and integrated into a comprehensive, continuously operated, oily water treatment system.

The technical approach was built on the compact, closedloop controlled waste incinerator for blackwater successfully developed previously under SERDP project WP-887: Demonstration of Compact, Closed-Loop Controlled Waste Incinerator. The project consisted of the following six developmental phases: (1) fundamental laboratory-scale studies on surrogate sludge waste mixtures; (2) VCC and AB integration schemes; (3) conceptual design; (4) scale-up and testing of practical embodiments under full-scale conditions; (5) integration of monitoring and automatic active control schemes; and (6) testing requirements definition for future transition to a demonstration/validation program.

The integration tests with Golar 500 and the actively controlled afterburner of the WP-887 project on compact waste incineration were completed successfully. The British Thermal Unit waste throughput of the off-the-shelf Golar was increased by a factor of three and the carbon monoxide emission was reduced by a factor of nine. This understanding of the technology was instrumental in the design and fabrication of the VCC/AB in the present project. The VCC Laboratory Combustor (LC) was designed, fabricated, and assembled. Gaseous fuel combustion characteristics were established for varying operational conditions. The project team integrated the VCC LC with the afterburner using low pressure-loss de-swirl design. High VCC/AB performance was demonstrated with low carbon monoxide and unburned hydrocarbon emissions using water as sludge surrogate plus alcohol as a volatile organic compound surrogate. Diagnostics were developed for the VCC Test Unit to determine evaporization limit and flame out limit. The waste sludge acceptance criteria was broadened for the full-scale VCC and the prescribed goals were achieved for the sludge surrogates such as water, water plus oil, and water plus volatile solids. This project was completed in FY 2001.

This technology has the potential to significantly reduce the cost of on-site disposal, either on shore facilities or, for larger vessels, onboard ship. Other advantages of on-site disposal include the increasing costs of off-site disposal, reducing assumed liability of third party disposal, eliminating waste handling and transportation, and avoiding costs for improper field disposal.