Paints utilized for military equipment, structures, ships, submarines, and weapons are formulated to stringent military specifications (MILSPEC). After the shelf life has expired, the paint can no longer be used for its original purpose or application. Furthermore, Navy policy prohibits the use of reformulated MILSPEC paint on anything classified as mission-critical; therefore, treatment and off-site disposal are the only two alternatives available for managing this waste. As a result, management and disposal of expired shelf-life (ESL) paint is the Navy’s most expensive waste. The problem is particularly acute on ships due to replenishment uncertainty; therefore, overstocked paint occurs when deployed, leading to the offloading of large quantities of ESL paint at their home port. This is an issue that is not limited to the Navy. The Joint Group on Depot Maintenance (JGDM) has also identified disposal of waste paint as a high priority at Department of Defense (DoD) facilities and initiated a project to determine how much paint is collected and the associated disposal costs.
The objective of this project was to demonstrate and validate the economic feasibility of biological treatment of ESL paint. Specific objectives derived from the pilot scale were:
- Construct and install a full-scale treatment system using commercially available components.
- Optimize operation of the system to treat ESL paint.
- Demonstrate that the degradation end products meet requirements for discharge and disposal.
- Facilitate technology transfer by acquiring design, cost, and performance data.
The long-term objective is to implement the use of biological reactors DoD-wide to reduce the cost and liability associated with the disposal of solvent-based paint.
Biological treatment of organic rich wastewater is an attractive and commonly used technology for the removal of dissolved organics and suspended organic solids. The process typically removes more than 90% of suspended organic solids and is the most cost effective treatment available for dissolved organics. Because of its simplicity and versatility, the use of biological treatment has been expanded to treat a wide variety of biodegradable waste and has often become the method of choice for the remediation of contaminated soil and water. The basic requirement for the process is mixing a near neutral pH and, for most applications, an aeration system, which provides oxygen and additional mixing.
Two parallel sequencing batch reactors, totaling a working volume of 8600 gal, and associated parts (can crusher, mixing tank, and air biofiltration system) were procured, installed, and tested over a 1-year period in cooperation with the Industrial Wastewater Treatment Complex (IWTC) in Pearl Harbor, Hawaii. Regulations required for successful treatment were at the federal, state, and local level and included discharge requirements established by the Fort Kamehameha Wastewater Treatment Plant (FK-WTP) for the water; toxicity characteristic leaching procedure (TCLP) requirements for the sludge; and Title V requirements for the air.
Six individual runs were performed on three different types of paint, each run lasting approximately 10 days. Runs 1 and 6 were excluded from the results and analysis. Run 1 was an acclimation period, and for run 6, an atypical, new paint type was delivered that proved much more difficult to treat. For the liquid phase discharge, all requirements were met in runs 2 through 5, except for a few spikes that were addressed by further settling.
All solid phase requirements were met, and Title V requirements in the biofilter exhaust were met 83% of the time. However, despite the successful results for discharge requirements, more questions and issues were raised, and the costs to run the system were exorbitant.
Issues of greatest concern are the large quantity of organic matter found in the sludge, indicating incomplete degradation; the cost prohibitive use of granular activated carbon for air polishing; the inability to adequately shear and emulsify the paint; the possible requirement of a Part B permit; and the need for highly trained personnel to operate the system. Finally, the biggest concern is the total cost of treatment. To run the system efficiently, calculations show the system requires $19.63 per gal of paint whereas hazardous disposal currently only costs $9.19 per gal of waste. System payback is impossible and annual cost reductions are nonexistent.