The Army has a variety of maintenance and industrial operations essential to its combat readiness. These activities include vehicle wash racks; maintenance facilities; petroleum, oil and lubricants (POL) storage, grease racks, and runoff containment. The waste stream produced by these activities may be contaminated with oil or grease. OWS are used to remove the contamination from the waste stream. After leaving an OWS the wastewater is often sent to a wastewater treatment plant for final polishing.

The military's mission requirements make it one of the largest purchasers of OWS in the United States. Unfortunately, some of the separators the military installed are not performing as anticipated. Inadequacies result from poor design, improper selection of off-the-shelf units, failure to understand the characteristics of the wastewater and lack of maintenance. The same problems can be found with field-constructed separators.

Most OWS are designed to remove oil and grease from waste streams. In reality OWS encounter significant quantities of dirt, cleaning aids, fuels, floatable debris, improperly disposed litter and other material.

Primarily, military OWS fail because of improper or inadequate maintenance. At times this is due to lack of convenient access for maintenance of the OWS. Some designs have only manhole access ports or installed completely below paved surfaces. When OWS fail they become ineffective. As a result, oil does not separate out of the OWS. Improper discharge of the wastewater can lead to regulatory action, treatment plant overload, or contamination of a storm water discharge system.

P2&ETD is dealing with the OWS problems through a variety of actions.

The DOD CWASSC gave the U.S. Army Environmental Center (USAEC) a high priority to develop guidance, tools and technologies for addressing OWS problems through the creation of the OWS subgroup. The OWS subgroup is responsible for the production of a DOD OWS Guidance Document. This document will be available in January 1999. It will include a considerable volume of technical and regulatory literature related to the planning, design, construction, procurement, operation, maintenance and record keeping associated with OWS. P2&ETD is pursuing demonstration projects to resolve the performance problems experienced with OWS in support of this document.

A team of representatives from USAEC, U.S. Army Construction Engineering Research Laboratory (USACERL) and the U.S. Army Aberdeen Test Center (USAATC) visited an Army National Guard unit 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 final report was given to the installation to explain the lessons learned during the evaluation of the three separators. The evaluation included whether or not the separator was properly designed, installed and followed a proper operation and maintenance plan.

The USAEC sponsored an effort with USAATC to examine technologies used to retrofit existing Army OWS. The primary technology examined was the VTC tube packs. The oleophilic tube packs are used to 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 were used to determine 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.

Results of this bench scale study are available in the document Final Report of the Coalescing Tubes Test for OWS.

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".

OWS are an important part of pretreatment of wastewater discharges from washrack operations. The OWS is the first line of defense in the proper handling of washrack wastewater. USAEC, USACERL and USAATC collaborated to evaluate OWS as an intricate part of a washrack system. A decision tree was produced with the data gathered from the investigation. The decision tree was designed to assist facility and environmental mangers in dealing with their OWS environmental compliance problems. The decision tree complements other guidance documents dealing with pretreatment of washrack wastewater.

The decision tree format is a series of questions in flowchart form aimed to help the OWS assessors define any necessary corrective actions. The evaluator must have knowledge of separator design and maintenance in order to utilize the decision tree. The decision tree is sequenced such that responses to questions are often depended on corrective actions being completed from the previous level.

Results of the study and the decision tree can be found in the final report A Decision Tree for Improving Washrack OWS Operations.

The USAEC partnered with the USACERL and USAATC to evaluate the effectiveness of closed loop washrack treatment systems. The study evaluated two commercial off-the-shelf washrack wastewater recycle treatments systems to determine their applicability to Army facilities. The evaluation assessed the resource requirements for installation, operation, maintenance and repair, and also assessed the effectiveness of the treatment. The two systems were found to use somewhat similar treatment processes. After a 3-month evaluation for each system, the results of the evaluations were also similar.

Results of the study can be found in the final report titled Evaluation of Two Washrack Recycle Treatment Systems.

The purpose of the Oil/Water Separation Technology User's Reference and Application Matrix is to compile and organize this information into a comprehensive, yet fast and easy to use reference tool for installation personnel. It is organized into sections: Overview, Application Matrix, Design Decision Tree, and Common Questions & Problems. Depending on the nature of the user's inquiry, you can directly select the section most relevant to your search, and move around within the document, as your information needs change.

You may access the information in this document in a number of ways:

Overview—This section provides a comprehensive overview of oil/water separation technology and application considerations. It incorporates in its entirety the U.S. Army Corps of Engineer's Engineering Technical Letter No. 1110-3-466, Engineering and Design—Selection and Design of Oil/Water Separators at Army Facilities, 26 August 1994.

Application Matrix—This section enables the user to search for specific information starting with a desired Waste Stream Source of concern, and a general functional Consideration. By selecting the corresponding button, it takes the user to a subcategories frame from which specific reference material can be retrieved, or links to applicable web sites may be used.

Design Decision Tree—This decision tree enables the user to quickly determine the need for an OWS, and to identify potential solutions to the common problems.

Common Questions & Problems—This section intends to be a compilation of questions and problems experienced by installation personnel nationwide. An On-Line Survey Form is available to gather the useful information on question/answer, problem/solution, and "lessons learned." You are encouraged to fill in the survey so we can later share this information with others dealing with OWS through the DoD community.