Recent Developments in Cleanup Technologies

Robert Peterson

APEG-PLUS DECONTAMINATION OF co+nm&r of Galson DIOXIN-CONTAMINA~ SLUDGE Remediation Corporutio~

services for PCB and dfoxfn contumfnated sot2.s

aprovfder of mmedfatfon The Signo Trading Superfund site cleanup was a Superfund

andsludges. emergency response action taken by the EPA Region I1 Superfund group operating out of Edison, New Jersey. The Signo Trading site was located in a highly urban area of Mt. Vernon, New York, near the borough of Brooklyn, New York. Residential apartments are located within 50 feet of the site. In mid- 1987, large volumes of waste were removed from the site and taken to approved disposal facilities. EPA was unable to complete the site cleanup, however, due to the presence of one partially fdled drum of dioxin-contaminated material. This material could not be removed from the site, since there was (and is) no disposal facility in the United States permitted to dispose of di- oxin-contaminated materials.

In September of 1987 Galson Research Corporation (now Galson Remediation) was contacted by the on-scene coordinator for EPA Re- gion 11, to discuss the possibility of treating the dioxin-contaminated materials on-siteusingthe patented' Galson APEG-PLUS process. Fol- lowing a site review by Galson, EPA accepted a Galson proposal for laboratory simulation and on-

site processing. Both the laboratory simulation and the field remediation were completed in October. The treated material was downgraded from acutely hazardous in mid-No- vember, and the treatment residues were shipped off site for incinera- tion.

PROCESS DEXRWI'ION The APEG-PLUS process

chemistry is a form of alkaline de- chlorination. Alkaline dechlorination is a well-established process in the chemical industry, dating back to the early 1900~.~ In the APEG-PLUS process (see Figure 11, haloge- nated aromatics are decomposed to low toxicity forms by removing the halogen and substituting for it an ether group. Thii is accomplished by fmt preparing in-situ an alkoxide by reaction of an alcohol or glycol with potassium or sodium hydrox- ide. At the Signo Trading site, polyethylene glycol with an average molecular weight of 400 was used as the alcohol. This reversible re- action produces an alkoxide and water. The alkoxide attacks the halogen in a substitution reaction, producing potassium chloride and a glycol ether. A sulfoxide is used as a co-solvent and phase transfer

RJMEDIATION/SPEING 1991 239

ROBERT PETERSEN

Figure 1, APEG-PLUS reaction mechanism

4 HO (C%CHp),$IK

catalyst. Dimethyl sulfoxide was used at this site. Toxicity testing of the dioxin and PCB reaction prod- ucts of this process has been con- ducted by both EPA' and outside laboratories. The reaction product (Figure 1) is a water-soluble sub- stituted glycol material with a high molecular weight. From a structural basis, this material would not be expected to show high toxicity, and toxicity testing to date has confirmed thii expectation.

LABORATORY SIMULATION As a matter of safe operation, a

laboratory simulation is always conducted on waste material prior to full scale cleanup. This allows modification of process conditions as needed to optimize the chemis- try for a specific matrix. The labe ratory simulation uses conventional laboratory &ssware to simulate full-scale processing. The glassware used is shown in Figure 2. A laboratory simulation showed the dioxin-contaminated material from the Signo Trading site to be easily reacted. Under laboratory condi-

tions, dioxin levels were reduced from approximately 190 ppb of 2,3,7,8 TCDD to 4 ppb TCDD in less than 10 minutes at 15OOC.

I;uLcscALE<3wEANup The processing system is de-

signed to provide heating and mix- ing of the sludgeheagent mixture without escape of dioxin or other contaminants that may be present. A diagram of the setup for a single drum is shown in Figure 3. Up to 20 drums have been manifolded in thii type of treatment system.

In the drum scale system, re- agents are added to an open top drum. The drum is then covered with a modified lid containing a coupling for a drum mixer and a temperature gauge. Drum heaters wrapped around the drum allow heating of the mixture to approxi- mately 150°C. An ice water con- denser allows reflux of any volatile materials thk may be present.

The waste from the Signo trad- ing site was contained in a deterio- rated drum enclosed in an intact overpak drum. It was determined

240 REMEDIATION/SPRING 1991

R B C B ~ DBVBLOPMEIWS IN CLEANUP T a c ~ p r o ~ o ~ ~ ~ s

Figure 2. Laboratory testing apparatus

Jrn

that the old drum was not suffi- ciently intact to allow direct p r e cessing. The dioxin-contaminated material was transferred to a new drum for processing. The old drum was rinsed with reagent, and then cut into pieces and placed into a second new drum. The pieces of old drum were covered with a layer of reagent and allowed to react during the remainder of the pro- cessing period.

The dioxin-contaminated sol-

ids and sludges were mixed in the new drum with an equal mass of potassium hydroxide, dimethyl sul- foxide, and polyethylene glycol to form a slurry. The slurry was heated with mixing to about 150°C and held at that temperature for several hours. The slurry mass was then allowed to cool overnight. Samples were taken for off-site analysis.

Analysis confiied that dioxin levels for both the treated drum pieces and the waste sludge had

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