PCBs and Soil Remediation

A few things, PCBs are exteemely resistant to bioremediation. Plant could bioaccumulate them, but they won't degrade the PCBs, so you have to do something with the plants.

Also, it is not the PCBs that are the concern, but rather the potential byproduct of thermal break down in the past of the PCBs, Dioxins. Therefore, electrothermal breakdown of PCB could cause you more headache than you want. Your best options generally are to ship the soil for treatment ex situ, or to send it to a hazardous waste facility like kettelmen hills here in CA.

PCBs are very stable substances and do not even undergo combustion readily. I have studied it since my undergraduate days, and recently as a bases for a toxic wastes recovery venture. It is all round tough. In fact the US Govt has stockpiles in Dover Delaware that they have not been able to safely dispose of.

My research work which I have only recently started to implement, requires the use of special incinerators that cost somewhere around $350,000 per reactor/incinerator. The overall cost of the mini-process is well.... out there. The fact is the govt requires that before the processing takes place some kind of insurance be secured and the last time I checked which was around 1994, the policy was well... out there. This chemical is virtually indestructible as far as I know.

The only known means of destroying it other than my technology is burning in cement kilns. The cement holds it and prevents its evaporation/vaporization while the heat decomposes it. This means that you must not evaporate/vaporize it as the people in the area will sooner or later die from cancer. Birds in the area will slowly die off as the chemical thins the egg shell causing a rapid breakage of the eggs and hence death of the chicks. Plants will absorb then and hold them in tact and then discharge them through the leaves which will decay and expose the chemicals on the ground surface to be blown about in the wind. I think I will just stop here.

This is what you do, pack the soil into containers and store them even as the US Govt does.

Might find some info in the EPA Technology Innovations newsletter:

http://www.clu-in.org/products/newsltrs/tnandt/default.cfm#October%202008

PCB is found in the same critters as Chloro pesticides. Until someone has the guts to do a 'one or the other' doping study, no one will know if there is substantial harm in the trace PCB contamination of biota/ soil. If you shoot a polar bear, and he is less fat than average, is that because he has pesticides in his fat, or PCB in his fat, or did he just find and kill fewer seals that year? Let's base policy on a guess, and ignore experimental science, like everyone else!

If your PCB does not burn (at low temp, 800-1000 degrees) it will do little harm. The whole issue arose from a mistake in the 70s. The folks in Japan knew there were PCB in some food, but did not know until years later that some of it had been transformed by overheating into Polychlorinated dioxins, which are very harmful, but harder to find with 70s lab technology. Media hysteria led to new laws and regs worldwide. Once the Government had made that error, and blamed PCB, they could never admit that the 'EMPEROR HAD NO CLOTHES' as the kiddie fable goes.

If your soil has been analyzed, and is above certain levels, I believe that the govt will require you to take standard actions like digging up, etc. The options are listed by the govt. Lots of folks are tempted to say nothing about their PCB contamination, but if you have had analysis done, and keep it a secret, you might eventually face penalties for doing so.

PCB actually does break down slowly in soil/ swamps. Each type of molecule has its own half-life in a given situation. The simplest molecules in a nice swamp will be half gone in a few years. Like other oily contaminants, it can also wander- slowly moving with subsoil water flow, so it can get more widspread before it 'disappears' on its own.

PCBs are relatively hydrophobic, like many polyaromatics. This means they bioacumulate in the fatty tissues.

As far as PCBs and dioxins. It is fairly common to find trace amounts of Dioxin in PCBs from transformers, as they reached a high enough temperature locally to transform into dioxins. This is the real concern with dumping of PCBs, that through the course of previous applications they have accumulated small amounts of dioxins, and as we all know 2,3,7,8 is one of the most toxic compounds known.

A reductive environment is one of the best ways to biodegrade PCBs. However, the reaction kinetics are extremely slow in reductive processes (usually at least 10 to 100 times slower than oxidative processes. this is why organic material can accumulate in a swamp and not in oxidizing environments like aerated soils (think of how coal comes into existence). Also, PCBs are one of the most stable compounds, so the overall reductive dechlorination reaction kinetics are orders of magnitude slower then reductive dechlorination of TCE or DCE. Swamps are a reducing environment. Reductive Dechlorination will occur over time, but the time could be centuries. Regulators are not going to allow you to just let a site wait to bioremediate for a century or two. Typically, the most common and cost effective practice west of the eastern sea board is to excavate and ship the souil to a haz waste storage facility. It is relatively rapid, and releases the owners from long term maintenance, monitoring, and liabilities. Other comon methods include ex-situ thermal degradation or washing, but these tend to be more expensive, mostly due to shipping distances, for large volumes of soil with very low compliance limits.

PCBs and Dioxins are extremely hydrophobic so they really will not move much in the presence of water, plus they bind fairly strongly to soil particles. So migration of PCBs, Dioxin, and most chlorinate aromatic pesticide/herbicides is not much of an issue. I have seen sites with DDT contamination that has remained in the upper 1 foot of the soil profile since the 1950s and 1960's when it was sprayed. The main concern is potential exposure paths from surface materials (dust inhalation, contact, etc.), not drinking water consumption.

It is rare for any of the oil in a transformer to reach more than 150C; even more rare to reach 180C. I have been a leading researcher in the breakdown of transformer materials for a very long time. In the 80s, I wrote the first method for low level furans. Are you suggesting that these temps are making significant amounts of PCD in oil that is 50 ppm PCB? I have not looked at the increase in PCD over time in such units, as we have other concerns. Have you?

Significant is relative, since we measure dioxins in part per trillion. However, of the many PCB contaminated sites from transformer disposal in the 1950s through early 1970s that i have investigated, we have always found significant levels of dioxin in the soils where there were high levels of PCBs remaining. these are almost always old landfills, sometimes they are old burn dumps which would make it obvious, many are old dump sites for military or industrial electrical, automotive and various metal components, etc.. Also, you might consider that while the oil reaches an average temperature of 150 degrees, how hot is the active surface of heated electrical elements.

The hottest copper surface is what I consider, and what I was referring to. I have developed test methods, for mechanical properties and the chemistry of byproducts, for the varnish often used on copper, and for the paper wrap, at temps of 150C to 180C, the range they face in overly hot units. Switching and such are not part of the life of the oil in a padmount or a power transformer main tank. I have no evidence that PCD is made in normal oil service, but it would be interesting to know that for sure. I suspect that in the past few decades, someone has already published a study of PCD production in an in-service unit.

Burn/ dump sites can present a lot of bad stuff.

A PCB molecule may stick well to a humus particle. (OTOH) A gallon of leaked oil will migrate fairly well, once its interfacial tension has been reduced by being loose in the environment for a few years. If said oil is a few ppm in PCB, the migration potential will be that of the oxidized oil, not of neat PCB.

The most efficent way to handle this problem is to use phytoremediation, growing lake sedge, Carex aquatalis in the contaminated soil, then disposing of the plant material by converting it to ethanol using the Infnite Renewable Energy (www.ire-incorp.com) process. The PCB's will be destroyed as the lignin is burned to provide the electricity and cooking heat. Water Hyacinth, Hydrilla and a few others can be used to clean up water supplies the same way.

Burning of PCBs area tricky thing. I would not recommend it as the byproduct, Dioxin, can be extyremely toxic and makes the ash a hazardous waste.

True, true, as the PCBs will evaporate out of the wood of the trees and then generate dioxins as the wood burning temperature would not be hot enough to actually cause the combustion of the PCBs.

Back in the mid 1980's I read an article citing research in Israel where bacteria had been found which break down PCB's.

Drums of waste material were treated by simply inserting bacteria in the drum.

Due to the hydrophobic nature of the PCB's it obviously wasn't that simple, almost certainly water and detergent would need to be added.

I have an excellent filing system for these old papers - it allows me to lose them with a clear conscience! (After all, "I filed that".) Just when the paper would have been useful it is "somewhere" in about 4 full filing cabinets, if it hasn't been lost during the number of moves I have had since then.

Sorry I can't give you a reference.

DVader is right when he suggests bacteria and green growth . They should work.

Perhaps you could solvent extract the bulk of the PCB in situ, add detergent to enable water to be added, then run through an improvised wetland.

Depending on the constraints imposed by your site, it may even prove simpler and cheaper to remove the contaminated soil and dispose of it off site.

The problem associated with phyto and bio remediation is that it can be very unpredictable, and almost always takes decades to remediate chlorinated compounds. This leads to long term liabilities, recurrent monitoring and maintenance costs, and the risk of a further release or interim changes in regulations that expand the scope of work.

This is why the preference is almost always to excavate and ship to a hazardous waste facility or and ex-situ treatment facility. The faster you clean close the site, the better.

I should think that if the US Govt considered these choices viable, the stockpiles at Dover Delaware would have been disposed of long ago.

It is important to consider the client, as you have shown. As the military doesn't have the same financial liabilities and risk considerations that private for profit industry has. Cleaning up a military site always drags out, as it seems the military sees it as a nuissance and don't care all as much about cost considerations long-term versus short-term. Plus anytime you dispose of haz waste at a long term storage facility, you take on liability for that facility, and the government has the deepest pockets and makes all the regulations. If the EPA fines the DOD, that just means next year the DOD gets a budget increase to pay the fines (assuming congress and the president let EPA fine DOD).

Perhaps so but in the late 1980s when I was actively engaged on the remediation, I was contacted by a company to form a "joint venture" to undertake the disposal, because of the interest at the time to have the waste disposed of.

Actually I only became aware of the Dover pile from the contact of this other company, so I would think that the Govt do want to dispose of it under the right circumstances.

The most common circumstance I have seen for military clean ups is a base closure or site closure. When the governemnt wants to hand the facilities over to the State or local authorities. Then it becomes a political hot spot and, as we all know, no politician or bureaucrat wants to be on the news for stalling something like that, which would be portrayed as a risk to local human health and welfare. As soon as the public becomes aware and interested, then the politician apply pressure and things get done.