Technology:
Direct Chemical Oxidation (DCO)
- Nonthermal, low temperature, ambient pressure, aqueous-based technology used to oxidize organic compounds in hazardous and mixed waste streams to carbon dioxide and water
- Oxidizing agent - sodium or ammonium peroxydisulfide
- Five continuously stirred tank reactors (CSTRs) - pretreatment, feed, and three-stage oxidizer (15L each)
- Hydrolysis used a pretreatment step for highly volatile wastes - for demonstration, hydrolysis used in tests of PCB waste streams only
- Operating temperature - hydrolysis - 150C; oxidation - 90C
- Oxidation rate - about 200-kg (as carbon) per cubic meter of reactor per day
- Tests conducted on several types of waste streams including concentrated waste streams (2,4,6-TNT, kerosene, triethlyamine, Dowex - an ion exchange resin, ethylene glycol), kerosene(predominately dodecane), chlorinated solvents (PCE, TCE, methylene chloride, chloroform and a mix of PCE and chloroform), and low concentrations (45 ppm) of PCBs
- The tests included oxidation and destruction rates for concentrated waste streams; oxidation time profile for kerosene; oxidation of chlorinated solvents without hydrolysis pretreatment; and treatment of PCB waste both with and without hydrolysis pretreatment
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Cleanup Authority:
Not identified
Product Line Manager:
Vince Maio
Advisory Engineer
Mixed Waste Focus Area
Lockheed Martin Idaho Technologies Company
Idaho National Engineering
and Environmental Laboratory
P.O. Box 1625
Idaho Falls, ID 83415
Telephone: 208-526-3696
Fax: 208-526-1061
E-mail: vmaio@inel.gov | Principal Investigator:
Dr. John Cooper
Chemistry and Materials Science
Directorate, L-352
LLNL
P.O. Box 808
Livermore, CA 94550
Telephone: 925-423-6649
Fax: 925-422-0049
E-mail: cooper3@llnl.gov |
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Contaminants:
Chlorinated solvents, PCBs, kerosene, explosives, ion exchange resins
- Solvents - TCE, PCE, methylene chloride, chloroform
- 2,4,6-TNT, triethylamine, ethylene gylcol |
Waste Source:
LLNL waste streams or surrogates containing chlorinated solvents |
Type/Quantity of Media Treated:
Waste streams from LLNL operations |
Purpose/Significance of Application:
Pilot-scale demonstration of the DCO process to treat a variety of organic aqueous waste streams |
Regulatory Requirements/Cleanup Goals:
- The purpose of the demonstration was to evaluate the DCO process on a variety of organic waste streams, including concentrated waste streams, under varying conditions
- No specific goals were established for the demonstration |
Results:
- Concentrated waste streams - the oxidation rate (based on Ka of 0.02-0.04 min-1 and input concentration of 5N oxidant) and the destruction rate were calculated for the concentrated waste streams; the oxidation rate was considered to be a rough estimate for CSTR scaling; oxidation rates ranged from 132 kg/m3/day (TNT and Dowex) to 432 kg/m3/day (ethylene glycol); destruction rates ranged from >98.8 (TNT and triethylamine) to >99.97% (kerosene)
- Kerosene- the oxidation rate profile showed a rapid destruction of kerosene following the addition of the oxidant at 90C - 99.97% within the first 70 minutes, followed by a slower destruction rate during the reminder of the test, with a destruction rate of 99.99% after 140 minutes
- Chlorinated solvents - results showed that chlorinated solvents are readily oxidized by the process, without pretreatment. Data reported on the extent of oxidation after 1 hr ranged from 0.967 to 0.996; however, the pretreatment step avoids the need to pressurize the oxidation step to avoid entrainment of the volatile solvents in the CO2 offgas
- PCBs - results showed that very dilute solutions of PCBs can be treated to below detection limits by the process, both with and without pretreatment; little difference was observed with and without pretreatment; pretreatment was determined not to be necessary since PCBs are not volatile |
Cost Factors:
- Projected costs for a full-scale DCO process were calculated for a 50 kg/day plant operating at an 80% capacity factor; costs were estimated for two scenarios - recycling the expended oxident and not recycling
- If recycled, the projected cost is $9.88/kg of carbon in the waste, including the cost of electrical energy ($2.63), labor ($3), and capital cost ($1.92) plus profit and G&A (30%)
- If not recycled, the projected cost is $79/kg of carbon in the waste based on the equivalent weights of sodium peroxydisulfate (119 g/equivalent) and carbon (3 g/equivalent), a bulk cost for sodium peroxydisulfate ($0.73/lb), and an assumed 80% stoichiometric efficiency |
Description:
In 1992, researchers at LLNL began developing the DCO process, a nonthermal, low temperature, aqueous based technology, for use in mixed waste treatment, chemical demilitarization and decontamination, and environmental remediation. A pilot-scale demonstration of the DCO process was conducted on a number of waste streams including concentrated wastes such as TNT, kerosene, triethlyamine, ion exchange resins, and ethylene glycol; chlorinated solvents such as TCE, PCE, methylene chloride, and chloroform; and low concentrations of PCBs in solution. The pilot-scale DCO process included a pretreatment (hydrolysis) step, used for highly chlorinated volatiles and a three-stage oxidation process performed in 15L reactors.
The results of the pilot-scale testing showed that the DCO process can treat a variety of organic waste streams. The destruction rate for the concentrated wastes was >98%, chlorinated solvents were readily oxidized using the three-stage oxidation only (without hydrolysis), and concentrations of PCBs were reduced to below detection levels both with and without pretreatment. According to LLNL, further research is not needed before scale-up of the technology, however, treatability studies are recommended for each candidate waste stream. Considerations in selecting DCO to treat a waste stream include the matrix and physical properties of the waste, waste composition and characteristics, and the target degree of oxidation/destruction removal efficiency. |
