The DoD Clean Water Act Service Steering Committee (CWASSC) tasked the U.S. Army Environmental Command (USAEC) to develop guidance, tools and technologies for addressing OWS problems through the creation of the OWS subgroup. The OWS subgroup published a DoD OWS Guidance Document in 1999 that included a considerable volume of technical and regulatory literature related to the planning, design, construction, procurement, operation, maintenance and record keeping associated with OWS.
A team of representatives from USAEC, U.S. Army Construction Engineering Research Laboratory (USACERL) and the U.S. Army Aberdeen Test Center (USAATC) visited Army National Guard units in California and South Carolina and Wright-Patterson Air Force Base to conduct OWS evaluation studies. The OWS were evaluated during a maintenance wash event and water samples were taken before and after the water entered the separator. Records of operation and maintenance were also evaluated to determine if the OWS was being maintained properly.
The USAEC sponsored an effort with USAATC to examine technologies used to retrofit existing Army OWS. The primary technology examined was the vertical tube coalescer (VTC) packs. The oleophilic tube packs increase the effectiveness of oil separation.
Several concentrations of oil and soil were run through a pilot scale OWS. These three influent concentrations had a known amount of total petroleum hydrocarbons (TPH) and total suspended solids (TSS). The concentrations used in the study were based on typical Army Reserve facilities wastewater characteristics determined by USACERL. The concentrations of TPH were monitored before and after running through the OWS. The differences in the concentration determined the oil removal efficiency.
The tests were run not only at different concentrations of TPH but also at different flow rates. This was to determine if the use of VTC could allow for the increased flow through the OWS while still meeting discharge criteria.
In order to determine the true effectiveness of the VTC, all tests were repeated with and without the tubes installed. This gave the study a baseline to compare the removal efficiencies.
Several Army installations were identified that either installed OWS with VTC tube packs or had retrofitted existing OWS with VTC tube packs. A site visit and reconnaissance was conducted to evaluate the feasibility and applicability of their OWS for further testing. A case study was developed to investigate the installation's experience with the retrofitted units. The OWS performance was investigated by evaluating the effectiveness of the unit with and without the VTC tube pack assembly in place. Observations and recommendations were made on design selection, construction, materials, operation & maintenance, and effectiveness of the tube systems. Results of the study can be found in the final report "Replacing or Retrofitting OWS."