The NitRem Project TeamIn July of 1993 Sam Houston State University (SHSU), Innotek Corporation, now ThermoEnergy Corporation (THE), and Battelle Pacific Northwest Laboratories (BPNNL) initiated a project which addresses one of the Defense Department's (DOD) major environmental problems, wastes from the manufacture of munitions, propellants and explosives.
Some Members of the NitRem Project Team at RFAAP
Zacker(BPNNL), Cossey(THE), Loeffler(SHSU), Fassbender(BPNNL)
Project BackgroundThis NitRem project took the patented NitRem concept which was validated in BPNNL laboratories on production wastes containing dinitrotoluene (DNT) and expanded it to a pilot scale, transportable unit. Completed laboratory scale studies, engineering design, and fabrication of a NitRem palletized pilot plant prepared the project for this demonstration which evaluated of the effectiveness of NitRem chemistry in destroying DNT in toxic, propellant production wastewater at the Radford Army Ammunition Plant (RFAAP).
NitRem Pilot Plant Under Construction
The Listed Hazardous WasteThe selected waste stream for this demonstration contains DNT which is a component of single-base propellants produced at RFAAP. This DNT-containing wastewater is co-mingled with all other industrial effluents and treated at an on-site biological wastewater treatment plant. Previous evaluations conducted by the U.S. Army Production Base Modernization Activity (PBMA), and Industrial Operations Command (IOC) have indicated that removal of DNT from the water dry effluent may alleviate the DNT discharge problem which has rendered the biosludge from the RFAAP treatment plant a listed waste.
The Dual-Shell Pressure-Balancing Pistons at RFAAP
Analysis of the effluent provided for the demonstration indicates DNT at a concentration of 120 ppm (120,000 ppb). This concentration is well over a thousand times the concentration allowed for outfall discharge according to RFAAP National Pollution Discharge Elimination System (NPDES) discharge limits (113 ppb average per week, 285 ppb daily maximum.)
Demonstration Test ResultsThe overall goal of the demonstration at RFAAP was to reduce DNT concentrations to below NPEDS permit levels. The project's Test Plan selected reactor conditions that the project's bench and engineering scale studies had predicted to provide optimum degradation reactions. At this temperature (350oC) and flow rate (0.4 gpm), the project team then improved reduction of residual DNT concentration from the original 120,000 ppb in the influent down to 40 ppb , then to 5 ppb, and finally to "non-detect" levels (well below 5 ppb) in the reactor effluent by adjusting amounts of feed chemicals. Thus, NitRem chemistry and the dual-shell, pressure-balanced reactor (DSPBR) reduced the concentration of DNT from 120,000 ppb to 5 ppb, achieving a destruction efficiency of 99.996%, then on further reducing it to <5 ppb, thus demonstrating better than "five nines" reaction efficiency!
The remainder of the Test Plan was designed to probe the question of whether or not the unit could be efficiently operated at lower temperatures and/or at feed rates other than 0.4 gpm. As expected, the test confirmed that 350oC (at 0.4 gpm) was an optimal operating temperature for this DNT waste stream although the unit could achieve acceptable destruction efficiency at 340oC with a reduced feed rate of 0.3 gpm ( down to 16 ppb DNT.) Causal relationships between temperature, residence time and reaction efficiency were further demonstrated.
The significance of these DNT results is that the NitRem chemistry along with the DSPBR will reduce this DNT, listed waste to less than 3% of RAAP's discharge limits. Once treated the NitRem process' effluent, which had been a DNT, hazardous waste, could be immediately discharged without fear of a public health hazard and in compliance with federal regulations.
In secondary sampling procedures, the project team also collected data to analyze the metal ion concentrations throughout the system. The purpose for these tests was to evaluate the possibility of corrosive degradation of the reactor shell and to detect leaks or breaches between reactor components. The liner in this DSPBR was a special chromium alloy, so monitoring chromium levels was of particular interest. The data indicate no detectable increase in chromium between influent and effluent streams, thus no significant corrosion occurred during operation. Review of sodium ion concentration in specific portions of the unit confirmed that there was no transmission of reactor side fluid, thus no breach nor leak during operation.
Numerous other tests were conducted by the project team, such as evaluation of chemical oxygen demand and nitrate/nitrite concentrations in reactor feed and reaction products, to analyze reaction conditions, as well as a gas-chromatograph/mass spectrometer study to identify possible degradation products which may be harmful to the environment. Analysis of these data further confirms that NitRem chemistry and the DSPBR worked very well indeed.
ConclusionToxic DNT levels were reduced by 99.996% to below NPEDS levels and no corrosive degradation occurred in the DSPBR. NitRem chemistry was not only effective at destroying DNT but also in destroying it in such a manner that no detectable reaction biproducts were introduced into the effluent.
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